The characteristics of summertime raindrop size distribution(DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau(IMP) were investigated,utilizing five-year continuous observations by...The characteristics of summertime raindrop size distribution(DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau(IMP) were investigated,utilizing five-year continuous observations by a PARSIVEL2disdrometer in East Ujimqin County(EUC),China.It is found that only 7.94% of the 15 664 one-min precipitation samples meet classification criteria as convective rain(CR),but its contribution to the total rainfall amount is 63.87%.Notably,40.72% of the rainfall comes from large-sized raindrops(D> 3 mm),despite the fact that large-sized raindrops account for only 1.73% of the CR total number concentration.Further results show that the mean value of mass-weighted mean diameters(Dm) is larger(2.43 mm) and generalized intercepts(lgN_(W)) is lower(3.19) in CR,aligning with a "continentallike" cluster,which is mainly influenced by the joint impact of in-cloud ice-based processes and the below-cloud environmental background.Also,the empirical relationships of shape-slope(μ-Λ),radar reflectivity-rain rate(Z-R),and rainfall kinetic energy(KE_(time)-Rand KE_(time)-Z) are localized.To quantitatively analyze the impact of DSD parameters on kinetic energy estimation,power-law KE_(time)-R and KE_(time)-Z relationships are derived based on the normalized gamma distribution.N_(W)takes precedence over μ in affecting variabilities of multiplicative coefficients,especially for KE_(time)-R relationship where the multiplicative coefficient is proportional to N_(W)^(-0.287).It should be noted that although the proportion of CR occurring throughout the summer is small,raindrops with lower N_(W) and larger Dmwill generate higher KE_(time),which will bring a higher potential risk of soil erosion in semi-arid regions over IMP.展开更多
The raindrop size distribution(DSD) is a significant characteristic of precipitation physics,which plays a crucial role in improving the accuracy of radar quantitative precipitation estimation and prediction.There is ...The raindrop size distribution(DSD) is a significant characteristic of precipitation physics,which plays a crucial role in improving the accuracy of radar quantitative precipitation estimation and prediction.There is an effect of atmospheric circulation and weather sy stems in South China,with frequent precipitation and differences in regional features,resulting in a limited understanding of the DSD characteristics and their impact mechanisms in the region. In this study,six ground-based two-dimensional video di sdrometers(2DVDs) were used to analyze the DSD of inland and coastal in South China during the five-year(2016-2020) monsoon seasons(April to September),ERA5 reanalysis data and MODIS cloud property products were also used to investigate the dynamics and microphysical characteristics of monsoon precipitation.Compared to inland rainfall,coastal rainfall has a higher conentration of small,medium,and diameter of less than 4.7 mm large raindrops.Considering the contributions to precipitation,the inland and coastal rainfall are dominated by convective rain,accounting for 74.8% and 84.7% of the total rainfall,respectively.The coastal rainfall has a higher the mass-weiglited mean diameter(D_(m)) value than the inland rainfall D_(m) for both the stratiform and convective rainfall.The logarithmic mean of the generalized intercept parameter(log_(10)N_(w)) in inland stratiform rain is greater than that in coastal areas,while convective rain is relatively small.Due to the impact of precipitation types and climate conditions,The Z-R relationship between inland and coastal rainfall also shows obvious differences.Compared to inland areas,there is more frequent convective activity,relatively moist near-surface conditions,and lower cloud droplet number concentrations,which contribute to larger D_(m) of raindrops in coastal areas.This study deepens the understanding of changes in South China's coastal and inland DSD and provides support for improving numerical weather forecasting in the region.展开更多
The characteristics of raindrop size distribution （DSD） over the Tibetan Plateau and southern China are studied in this paper, using the DSD data from April to August 2014 collected by HSC-PS32 disdrometers in Nagqu...The characteristics of raindrop size distribution （DSD） over the Tibetan Plateau and southern China are studied in this paper, using the DSD data from April to August 2014 collected by HSC-PS32 disdrometers in Nagqu and Yangjiang, com- prising a total of 9430 and 63661-rain raindrop spectra, respectively. The raindrop spectra, characteristics of parameter variations with rainfall rate, and the relationships between reflectivity factor （Z） and rainfall rate （R） are analyzed, as well as their DSD changes with precipitation type and rainfall rate. The results show that the average raindrop spectra appear to be one-peak curves, the number concentration for larger drops increase significantly with rainfall rate, and its value over southern China is much higher, especially in convective rain larger drops, especially for convective rain in southern China. Standardized Gamma distributions better describe DSD for All three Gamma parameters for stratiform precipitation over the Tibetan Plateau are much higher, while its shape parameter （,u） and mass-weighted mean diameter （Dm）, for convective precipitation, are less. In terms of parameter variation with rainfall rate, the normalized intercept parameter （Nw） over the Tibetan Plateau for stratiform rain increases with rainfall rate, which is opposite to the situation in convective rain. The/1 over the Tibetan Plateau for stratiform and convective precipitation types decreases with an increase in rainfall rate, which is opposite to the case for Dm variation. In Z-R relationships, like ＂Z = ARb＇＇, the coefficient A over the Tibetan Plateau is smaller, while its b is higher, when the rain type transfers from stratiform to convective ones. Furthermore, with an increase in rainfall rate, parameters A and b over southern China increase gradually, while A over the Tibetan Plateau decreases sub- stantially, which differs from the findings of previous studies. In terms of geographic location and climate over the Tibetan Plateau and southern China, the precipitation in the pre-flood seasons is dominated by strong convective rain, while weak convective rain occurs frequently in northern Tibet with lower humidity and higher altitude.展开更多
Microphysical characteristics of the raindrop size distribution(RSD)in Typhoon Morakot(2009) have been studied through the PARSIVEL disdrometer measurements at one site in Fujian province,China during the passage of t...Microphysical characteristics of the raindrop size distribution(RSD)in Typhoon Morakot(2009) have been studied through the PARSIVEL disdrometer measurements at one site in Fujian province,China during the passage of the storm from 7 to 10 August 2009.The time evolution of the RSD reveals different segments of the storm.Significant difference was observed in the microphysical characteristics between the outer rainband and the eyewall;the eyewall precipitation had a broader size distribution(a smaller slope) than the outer rainband and eye region.The outer rainband and the eye region produced stratiform rains while the eyewall precipitation was convective or mixed stratiform-convective.The RSD was typically characterized by a single peak distribution and well represented by the gamma distribution.The relations between the shape(μ)and slope(Λ)of the gamma distribution and between the reflectivity(Z)and rainfall rate(R)have been investigated.Based on the NW-Dm relationships,we suggest that the stratiform rain for the outer rainband and the eye region was formed by the melting of graupel or rimed ice particles,which likely originated from the eyewall clouds.展开更多
The characteristics of the raindrop size distribution(DSD)during regional freezing rain(FR)events that occur throughout the phase change(from liquid to solid)are poorly understood due to limited observations.We invest...The characteristics of the raindrop size distribution(DSD)during regional freezing rain(FR)events that occur throughout the phase change(from liquid to solid)are poorly understood due to limited observations.We investigate the evolution of microphysical parameters and the key formation mechanisms of regional FR using the DSDs from five disdrometer sites in January 2018 in the Jianghan Plain(JHP)of Central China.FR is identified via the size and velocity distribution measured from a disdrometer,the discrete Fréchet distancemethod,surface temperature,human observations,and sounding data.With the persistence of precipitation,the emergence of graupel or snowflakes significantly reduces the proportion of FR.The enhancement of this regional FR event is mainly dominated by the increase in the number concentration of raindrops but weakly affected by the diameters.To improve the accuracy of quantitative precipitation estimation for the FR event,a modified second-degree polynomial relation between the shapeμand slopeΛof gamma DSDs is derived,and a new Z-R(radar reflectivity to rain rate)relationship is developed.The mean values of mass-weighted mean diameters(D_(m))and generalized intercepts(lgN_(w))in FR are close to the stratiform results in the northern region of China.Both the melting of tiny-rimed graupels and large-dry snowflakes are a response to the formation of this regional FR process in the JHP,dominated by the joint influence of the physical mechanism of warm rain,vapor deposition,and aggregation/riming coupled with the effect of weak convective motion in some periods.展开更多
Mêdog and Nagqu are two typical regions of the Tibetan Plateau with different geographical locations and climate regimes.These differences may lead to discrepancies in the raindrop size distributions(DSDs)and pre...Mêdog and Nagqu are two typical regions of the Tibetan Plateau with different geographical locations and climate regimes.These differences may lead to discrepancies in the raindrop size distributions(DSDs)and precipitation microphysical processes between the two regions.This paper investigates discrepancies in the DSDs using disdrometer data obtained during the rainy season in Mêdog and Nagqu.The DSD characteristics are studied under five different rainfall rate categories and two precipitation types(stratiform and convective).For the total datasets,the number concentrations of drops with diameters D>0.6(D<0.6)mm are higher(lower)in Nagqu than in Mêdog.The fitted normalized gamma distributions of the averaged DSDs for the five rainfall rate categories show that Nagqu has a larger(lower)mass-weighted mean diameter D_(m)(normalized intercept parameter,lgNw)than Mêdog does.The difference in D_(m)between Nagqu and Mêdog increases with the rainfall rate.Convective clusters in Nagqu could be identified as continental-like,while convective precipitation in Mêdog could be classified as maritime-like.The relationships between the shape factorμand slope parameterΛof the gamma distribution model,the radar reflectivity Z,and the rainfall rate R are also derived.Furthermore,the possible causative mechanism for the notable DSD variation between the two regions during the rainy season is illustrated using reanalysis data and automated weather station observations.Cold rain processes are mainly responsible for the lower concentrations of larger drops observed in Nagqu,whereas warm rain prevails in Mêdog,producing abundant small drops.展开更多
The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation...The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation process was selected,and the shape-slope(μ-Λ)relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer(2DVD)at Xinfeng Station,Guangdong Province.Simulated data of the C-band polarimetric radar reflectivity ZHHand differential reflectivity ZDRwere obtained through scattering simulation.The simulation data were combined with DSD fitting to determine the ZDR-Λand log10(ZHH/N0)-Λrelationships.Using Xinfeng C-band polarimetric radar observations ZDRand ZHH,the raindrop Gamma size distribution parametersμ,Λ,and N0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was developed.This research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity(R),mass-weighted mean diameter(Dm)and intercept parameter(Nw)with time obtained by radar retrieval are basically consistent with the observational results of the 2DVD.This scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical model.This method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation estimation.The present research will facilitate radar data assimilation in the future.展开更多
While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribut...While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribution(DSD)is useful in improving the quantitative precipitation estimation and forecast.Based on the data during 2018-2022 from 86stations in a ground-based optical disdrometer measurement network,the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution(N(D)),mass-weighted mean diameter(Dm) and other integral DSD parameters such as radar reflectivity(Z),rainfall rate(R) and liquid water content(LWC).In addition,the effects of geographical locations,weather systems(tropical cyclones,frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered.The results are shown as follows.1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation,and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution.The relationships between the Z and R for stratiform and convective precipitation are also derived for the province,i.e.,Z=332.34 R1.32and Z=366.26R1.42which is distinctly different from that of the Next-generation Weather Radar(NEXRAD) Z-R relationship in United States.2) In the rainy season(April-September),the Dm, R and LWC are larger than those in the dry season(OctoberMarch).Moreover the above parameters are larger,especially in mid-May,which is the onset of the South China Sea summer monsoon.3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dmand a larger normalized intercept parameter(log10Nw),suggestive of maritime-like rainfall.Dmis larger and log10Nwis smaller in the inland area,suggestive of continental-like rainfall.4) Affected by such weather systems as the tropical cyclone,frontal system and summer monsoon,the DSD shows characteristics with distinct differences.Furthermore,frontal system rainfall tends to present a continental-like rainfall,tropical cyclone rainfall tends to have a maritime-like rainfall,and summer monsoon rainfall characteristic are between maritime-and continental-like cluster(raindrop concentration and diameter are higher than continental cluster and maritime cluster,respectively.)展开更多
The diurnal variation in the vertical structure of the raindrop size distribution(RSD)associated with stratiform rain at Kototabang,West Sumatra(0.20°S,100.32°E),was investigated using micro rain radar(MRR)o...The diurnal variation in the vertical structure of the raindrop size distribution(RSD)associated with stratiform rain at Kototabang,West Sumatra(0.20°S,100.32°E),was investigated using micro rain radar(MRR)observations from January 2012 to August 2016.Along with the MRR data,the RSD from an optical disdrometer and vertical profile of precipitation from the Tropical Rainfall Measuring Mission were used to establish the microphysical characteristics of diurnal rainfall.Rainfall during 0000–0600 LST and 1800–2400 LST had a lower concentration of small drops and a higher concentration of large drops when compared to rainfall during the daytime(0600–1800 LST).The RSD stratified on the basis of rain rate(R)showed a lower total concentration of drops and higher mass-weighted mean diameter in 0000–0600 LST and1800–2400 LST than in the daytime.During the daytime,the RSD is likely governed by a riming process that can be seen from a weak bright band(BB).On the other hand,during 0000–0600 LST and 1800–2400 LST,the BB was stronger and the rainfall was associated with a higher concentration of midsize and large drops,which could be attributed to more active aggregation right above the melting layer with minimal breakup.Diurnal variation in the vertical profile of RSD led to a different radar reflectivity(Z)–R relationship in the rain column,in which Z during the periods 0000–0600 LST and1800–2400 LST was larger than at the other times,for the same R.展开更多
In the issue of rainfall estimation by radar through the necessary relationship between radar reflectivity Z and rain rate R (Z-R), the main limitation is attributed to the variability of this relationship. Indeed, se...In the issue of rainfall estimation by radar through the necessary relationship between radar reflectivity Z and rain rate R (Z-R), the main limitation is attributed to the variability of this relationship. Indeed, several pre-vious studies have shown the great variability of this relationship in space and time, from a rainfall event to another and even within a single rainfall event. Recent studies have shown that the variability of raindrop size distributions and thereby Z-R relationships is therefore, more the result of complex dynamic, thermody-namic and microphysical processes within rainfall systems than a convective/stratiform classification of the ground rainfall signature. The raindrop number and size at ground being the resultant of various processes mentioned above, a suitable approach would be to analyze their variability in relation to that of Z-R relation-ship. In this study, we investigated the total raindrop concentration number NT and the median volume di-ameter D0 used in numerous studies, and have shown that the combination of these two ‘observed’ parame-ters appears to be an interesting approach to better understand the variability of the Z-R relationships in the rainfall events, without assuming a certain analytical raindrop size distribution model (exponential, gamma, or log-normal). The present study is based on the analysis of disdrometer data collected at different seasons and places in Africa, and aims to show the degree of the raindrop size and number implication in regard to the Z-R relationships variability.展开更多
Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau.The analysis focuses on convective and stratiform pr...Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau.The analysis focuses on convective and stratiform precipitation at high altitudes from 2434 m to 4202 m.The results show that the contribution of stratiform and convective precipitation with rain rate between 1≤R<5 mm h^(-1)to the total precipitation increases with altitude,and the raindrop scale and number concentration of convective precipitation is larger than that for stratiform precipitation.The droplet size spectra of both stratiform and convective precipitation shows a single peak with a peak particle size between 0.31–0.50 mm,and they have essentially the same peak particle size and number concentration at the same altitude.The maximum spectral widths of stratiform clouds are between 4 mm and 5 mm,while those of convective clouds range from 4 mm to 8 mm.The Gamma distribution is more suitable than the Marshall-Palmer distribution in terms of the actual raindrop spectrum distribution.The stratiform precipitation particles are smaller with higher number concentration,while the opposite is true for the convective precipitation particles.The convective precipitation particles drop faster than stratiform precipitation particles when the particle size exceeds 2 mm,and the falling velocity of raindrops after standard curve fitting is underestimated during the observation period.Moreover,conventional radar estimation methods would underestimate the precipitation in the Northeastern Tibetan Plateau.展开更多
Freezing rain(FZR)presents significant risks to energy,transportation,and agriculture,leading to substantial economiclossesandcasualties,particularlyinsouthwestern,central,andeasternChina,withonlyoccasionaloccurrences...Freezing rain(FZR)presents significant risks to energy,transportation,and agriculture,leading to substantial economiclossesandcasualties,particularlyinsouthwestern,central,andeasternChina,withonlyoccasionaloccurrences in northern China.This study investigates an extreme,large-scale FZR event that occurred during 8–9 November 2021 in Heilongjiang Province of Northeast China,marking the region’s most intense FZR since 1958.Surface station observations revealed distinct characteristics of the FZR,and the stations were classified into three types by using the k-means clustering:stations with continuous FZR(FZR_Con),stations with FZR of mixed hydrometeor types(FZR_Mix),and stations with FZR transitioning to rain(FZR_Rain).Vertical atmospheric temperature and humidity profiles significantly influenced the raindrop size distribution(DSD)for the three station types.All three station types exhibited an inversion layer in the upper atmosphere,though they formed through two distinct mechanisms:(1)the supercooled warm rain mechanism and(2)the melting mechanism.This study found that the massweighted mean diameters(D--m)were larger than those observed in FZR events in central China and in stratiform rain in northern and northwestern China.FZR_Mix,which formed through the supercooled warm rain mechanism,exhibited the largest D_(m) among the three types.In contrast,FZR_Con and FZR_Rain formed through the melting mechanism,involving the melting of ice crystals and snow particles.The drier refreezing layer in FZR_Rain,compared to FZR_Con,resulted in a lower normalized number concentration(N_(w))and a larger D_(m).Positive exponential relationships between D_(m) and R(precipitation rate),as well as N_(w) and R,across all FZR types,highlighting dominant role of microphysical processes such as collision and coalescence.Variations in the gamma distribution parameters—shape(μ)and slope(λ)—as well as in the radar Z–R relationships among the FZR types further underscore differences in the microphysical processes and regional precipitation characteristics.This study enhances our understanding of the macro-and microphysical properties of FZR formed through different mechanisms,providing valuable reference for improved radar-based precipitation estimation in mid-and high-latitude regions.展开更多
Knowledge of raindrop size distribution(RSD)is essential for understanding microphysical processes occurring within cloud and precipitation systems,as well as for enhancing the capabilities of numerical models and rad...Knowledge of raindrop size distribution(RSD)is essential for understanding microphysical processes occurring within cloud and precipitation systems,as well as for enhancing the capabilities of numerical models and radar-based quantitative precipitation estimation(QPE).However,observation and study of RSD,especially its temporal and spatial variability,remain quite limited in specific regions.One such region is Southeast China.In this paper,four years of disdrometer data from a south coastal plain site(CPS)and a north hilly inland site(HIS)in the Fujian Province of Southeast China are analyzed and compared to elucidate the characteristics and discrepancies of RSD between these two distinct climatological sites.On this basis,empirical relations between the parameters of Gamma distribution and between radar reflectivity factor(Z)and rain rate(R)are proposed.The results are summarized as follows.(1)In the cases of light to moderate rains,HIS exhibits a higher(lower)concentration of small-size(midsize and large)raindrops with diameters of D<1 mm(1≤3 and D≥3 mm),compared to CPS.Conversely,as the rain intensity increases,the raindrop concentrations across all size categories at CPS gradually exceed those at HIS.(2)RSDs at both sites broaden and exhibit elevated concentrations across most diameter categories as the rain rate increases.(3)For rainfalls with rain rates below 5 mm h^(-1),collision and coalescence dominate,resulting in unimodal rain spectra at both sites;whereas for stronger rainfalls,breakup intensifies,leading to the development of bimodal rain spectra.(4)HIS experiences more stratiform rains but fewer,weaker convective rains than CPS.Stratiform RSD at HIS possesses more small and large raindrops but fewer midsize raindrops compared to CPS,whereas convective RSD at CPS possesses higher concentrations across all diameter categories.(5)Accordingly,specific Z–R relations at these two sites are proposed and validated for two real cases,demonstrating that the accuracy of radar QPE is effectively improved based on the proposed Z–R relations.展开更多
According to the statistical shape-slope （μ-A） relationship observed for the first time by several 2D-Video-Distro-meters （2DVD） in southern China, a constrained gamma （C-G） model was proposed for the retrieval...According to the statistical shape-slope （μ-A） relationship observed for the first time by several 2D-Video-Distro-meters （2DVD） in southern China, a constrained gamma （C-G） model was proposed for the retrieval of rain drop size distributions （DSDs） from Guangzhou S-band polarimetric radar observations. Two typical precipitation processes were selected to verify the accuracy of the retrieval scheme. The p-A relationship： A = 0.0241μ^2 ＋ 0.867μ ＋ 2.453 was obtained based on the 2DVD observation results from at Huizhou Longmen station, which is a very representat-ive location in the area. Relying on the Guangzhou polarimetric radar measurements of radar reflectivity （ZHH） and differential reflectivity （ZDR）, the gamma （F） size distribution parameters （No, μ, and A） can be retrieved by the C-G model retrieval scheme. The results show that the Guangzhou polarimetric radar retrievals of DSDs were close to the 2DVD observations at Guangzhou Maofengshan station. The rain rate, mass mean diameter, and normalized inter-cept parameter of radar retrievals were in good agreement with the 2DVD observations, and the relative errors were less than 10%. The overall accuracy of the retrieval scheme was high. The retrieval scheme has established the rela-tionship between the polarimetric radar measurements and gamma size distribution parameters. It will be helpful to in-depth research and application of the dual-polarization radar data in microphysical precipitation processes analysis, as well as convection-resolved numerical model data assimilation and prediction effect evaluation.展开更多
In this study,a regional Parsivel OTT disdrometer network covering urban Zhengzhou and adjacent areas is employed to investigate the temporal-spatial variability of raindrop size distributions(DSDs)in the Zhengzhou ex...In this study,a regional Parsivel OTT disdrometer network covering urban Zhengzhou and adjacent areas is employed to investigate the temporal-spatial variability of raindrop size distributions(DSDs)in the Zhengzhou extreme rainfall event on 20 July 2021.The rain rates observed by disdrometers and rain gauges from six operational sites are in good agreement,despite significant site-to-site variations of 24-h accumulated rainfall ranging from 198.3 to 624.1 mm.The Parsivel OTT observations show prominent temporal-spatial variations of DSDs,and the most drastic change was registered at Zhengzhou Station where the record-breaking hourly rainfall of 201.9 mm over 1500-1600 LST(local standard time)was reported.This hourly rainfall is characterized by fairly high concentrations of large raindrops,and the mass-weighted raindrop diameter generally increases with the rain rate before reaching the equilibrium state of DSDs with the rain rate of about 50 mm h^(−1).Besides,polarimetric radar observations show the highest differential phase shift(K_(dp))and differential reflectivity(Z_(dr))near surface over Zhengzhou Station from 1500 to 1600 LST.In light of the remarkable temporal-spatial variability of DSDs,a reflectivity-grouped fitting approach is proposed to optimize the reflectivity-rain rate(Z-R)parameterization for radar quantitative precipitation estimation(QPE),and the rain gauge measurements are used for validation.The results show an increase of mean bias ratio from 0.57 to 0.79 and a decrease of root-mean-square error from 23.69 to 18.36 for the rainfall intensity above 20.0 mm h^(−1),as compared with the fixed Z-R parameterization.This study reveals the drastic temporal-spatial variations of rain microphysics during the Zhengzhou extreme rainfall event and warrants the promise of using reflectivity-grouped fitting Z-R relationships for radar QPE of such events.展开更多
Mêdog,located at the entrance of the water vapour channel of the Yarlung Zangbo Grand Canyon,and it has the highest rainfall and lowest elevation on the Tibetan Plateau(TP).The droplet size distribution(DSD)and m...Mêdog,located at the entrance of the water vapour channel of the Yarlung Zangbo Grand Canyon,and it has the highest rainfall and lowest elevation on the Tibetan Plateau(TP).The droplet size distribution(DSD)and microphysical processes associated with rainfall usually exhibit different characteristics under different synoptic patterns.In this study,an objective classification method is used to categorize the synoptic patterns that affect heavy rainfall(daily rainfall amounts>10 mm)in Mêdog into four patterns:southwest airflow(SWA),southern-branch trough(SBT),intense baroclinicity(IBC),and terrain-forced precipitation(TFP).SWA occurs most frequently(approximately 70%)with a mean daily rainfall of~22 mm,while TFP has the lowest occurrence frequency(7.7%)but the highest mean daily rainfall(29 mm).Both SBT and IBC exhibit occurrence frequencies around 12%.Among these patterns,the SWA pattern predominantly occurs during the monsoon season with abundant moisture and the lowest concentration of small raindrops.In contrast,the TFP pattern exhibits the highest concentration of large raindrops and the widest DSD spectrum,which can be attributed to the frequent convective activities in this area.As a result,compared with those of the other three synoptic patterns,the TFP pattern exhibits a larger mass-weighted mean diameter(D_(m))and higher rain rate(R).For stratiform rainfall,the difference in D_(m)among the four synoptic patterns can be neglected.The largest(smallest)average lgNW-value is observed in the SWA(IBC)pattern.Regarding convective rainfall,IBC dominated by northerly cold air exhibits mixed-phase processes characterized by larger raindrops and lower concentrations,resembling continental-like rainfall.In contrast,SWA occurring in monsoon season shows high concentrations of small raindrops,deeming it similar to maritime-like rainfall.In terms of the derived relationships,there are significant differences in the D_(m)-R andμ-Λrelationships among the four synoptic patterns.In addition,the diurnal variation in the DSD is analyzed in terms of the four synoptic patterns.These findings can improve the understanding of the microphysical processes of heavy rainfall events under different synoptic patterns and provide a reference for microphysical parameterizations of numerical models.展开更多
In this study, a framework is given by which air/space-borne dual-wavelength radar data can be used to estimate the characteristic parameters of hydrometeors. The focus of the study is on the Global Precipitation Meas...In this study, a framework is given by which air/space-borne dual-wavelength radar data can be used to estimate the characteristic parameters of hydrometeors. The focus of the study is on the Global Precipitation Measurement （GPM） precipitation radar, a dual-wavelength radar that will operate in the Ku （13.6 GHz） and Ka （35 GHz） bands. A key aspect of the retrievals is the relationship between the differential frequency ratio （DFR） and the median volume diameter, Do, and its dependence on the phase state of the hydrometeors. It is shown that parametric plots of Do and particle concentration in the plane of the DFR and the radar reflectivity factor in the Ku band can be used to reduce the ambiguities in deriving Do from DFR. A self-consistent iterative algorithm, which does not require the use of an independent pathattenuation constraint, is examined by applying it to the apparent radar reflectivity profiles simulated from a drop size distribution （DSD） model. For light to moderate rain, the self-consistent rain profiling approach converges to the correct solution only if the same shape factor of the Gamma distributions is used both to generate and retrieve the rain profiles. On the other hand, if the shape factors differ, the iteration generally converges but not to the correct solution. To further examine the dual-wavelength techniques, the selfconsistent iterative algorithm, along with forward and backward rain profiling algorithms, are applied to measurements taken from the 2nd generation Precipitation Radar （PR-2） built by the Jet Propulsion Laboratory. Consistent with the model results, it is found that the estimated rain profiles are sensitive to the shape factor of the size distribution when the iterative, self-consistent approach is used but relatively insensitive to this parameter when the forward- and backward-constrained approaches are used.展开更多
In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and ...In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and upshear right(UR)]during the final landfall of Typhoon Ewiniar(2018) is analyzed using two-dimensional video disdrometer and S-band polarimetric radar data collected in Guangdong, China. Due to the different types of underlying surfaces, the periods before landfall(mainly dominated by underlying sea surface) and after landfall(mainly dominated by underlying land surface) are also analyzed. Both before landfall and after landfall, the downshear quadrants had the dominate typhoon precipitation. The outer rainbands had more graupel than the inner core, resulting in a larger radar reflectivity, differential reflectivity, specific differential phase shift, and mass-weighted mean diameter below the melting layer. Compared with other regions, the eyewall region had the smallest mean logarithmic normalized intercept parameter before landfall and the smallest mean mass-weighted mean diameter and the largest mean logarithmic normalized intercept parameter after landfall. The hydrometeor size sorting was obvious in the eyewall and inner core(especially in the eyewall) after landfall. A high concentration of large raindrops fell in the DL quadrant, and more small raindrops fell in the UR quadrant. Although the icephase process and warm rain process were both important in the formation of tropical cyclone precipitation, the warm rain process(ice-phase process) contributed more liquid water before landfall(after landfall). This investigation provides a reference for improving the microphysical parameterization scheme in numerical models.展开更多
During the April-June raining season,warm-sector heavy rainfall(WR) and frontal heavy rainfall(FR) often occur in the south of China,causing natural disasters.In this study,the microphysical characteristics of WR and ...During the April-June raining season,warm-sector heavy rainfall(WR) and frontal heavy rainfall(FR) often occur in the south of China,causing natural disasters.In this study,the microphysical characteristics of WR and FR events from 2016 to 2022 are analyzed by using 2-dimensional video disdrometer(2DVD) data in the south of China.The microphysical characteristics of WR and FR events are quite different.Compared with FR events,WR events have higher concentration of D<5.3 mm(especially D <1 mm),leading to higher rain rates.The mean values of Dmand lgNwof WR events are higher than that of FR events.The microphysical characteristics in different rain rate classes(C1:R~5-20 mm h-1,C2:R~20-50 mm h-1,C3:R~50-100 mm h^(-1),and C4:R> 100 mm h^(-1)) for WR and FR events are also different.Raindrops from C3 contribute the most to the precipitation of WR events,and raindrops from C2 contribute the most to the precipitation of FR events.For C2 and C3,compared with FR events,WR events have higher concentration of D <1 mm and D~3-4.5 mm.Moreover,the shape and slope(μ-A) relationships and the radar reflectivity and rain rate(Z-R) relationships of WR and FR events are quite different in each rain rate class.The investigation of the difference in microphysical characteristics between WR and FR events provide useful information for radar-based quantitative precipitation estimation and numerical prediction.展开更多
Raindrop size distribution(DSD)plays a crucial role in enhancing the accuracy of radar quantitative precipitation estimates in the Tibetan Plateau(TP).However,there is a notable scarcity of long-term,high-resolution o...Raindrop size distribution(DSD)plays a crucial role in enhancing the accuracy of radar quantitative precipitation estimates in the Tibetan Plateau(TP).However,there is a notable scarcity of long-term,high-resolution observations in this region.To address this issue,long-term observations from a two-dimensional video disdrometer(2DVD)were leveraged to refine the radar and satellite-based algorithms for quantifying precipitation in the hinterland of the TP.It was observed that weak precipitation(R<1,mm h-1)accounts for 86%of the total precipitation time,while small raindrops(D<2 mm)comprise 99%of the total raindrop count.Furthermore,the average spectral width of the DSD increases with increasing rain rate.The DSD characteristics of convective and stratiform precipitation were discussed across five different rain rates,revealing that convective precipitation in Yangbajain(YBJ)exhibits characteristics similar to maritime-like precipitation.The constrained relationships between the slopeΛand shapeμ,D_(m)and N_(w)of gamma DSDs were derived.Additionally,we established a correlation between the equivalent diameter and drop axis ratio and found that raindrops on the TP attain a nearly spherical shape.Consequently,the application of the rainfall retrieval algorithms of the dual-frequency precipitation radar in the TP is improved based on the statistical results of the DSD.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42325503,42075063,42075066,and 42021004)the Hubei Provincial Natural Science Foundation and the Meteorological Innovation and Development Project of China(Grant No.2023AFD096)the Beijige Foundation of NJIAS(Grant No.BJG202304).
文摘The characteristics of summertime raindrop size distribution(DSD) and associated relations in the semi-arid region over the Inner Mongolian Plateau(IMP) were investigated,utilizing five-year continuous observations by a PARSIVEL2disdrometer in East Ujimqin County(EUC),China.It is found that only 7.94% of the 15 664 one-min precipitation samples meet classification criteria as convective rain(CR),but its contribution to the total rainfall amount is 63.87%.Notably,40.72% of the rainfall comes from large-sized raindrops(D> 3 mm),despite the fact that large-sized raindrops account for only 1.73% of the CR total number concentration.Further results show that the mean value of mass-weighted mean diameters(Dm) is larger(2.43 mm) and generalized intercepts(lgN_(W)) is lower(3.19) in CR,aligning with a "continentallike" cluster,which is mainly influenced by the joint impact of in-cloud ice-based processes and the below-cloud environmental background.Also,the empirical relationships of shape-slope(μ-Λ),radar reflectivity-rain rate(Z-R),and rainfall kinetic energy(KE_(time)-Rand KE_(time)-Z) are localized.To quantitatively analyze the impact of DSD parameters on kinetic energy estimation,power-law KE_(time)-R and KE_(time)-Z relationships are derived based on the normalized gamma distribution.N_(W)takes precedence over μ in affecting variabilities of multiplicative coefficients,especially for KE_(time)-R relationship where the multiplicative coefficient is proportional to N_(W)^(-0.287).It should be noted that although the proportion of CR occurring throughout the summer is small,raindrops with lower N_(W) and larger Dmwill generate higher KE_(time),which will bring a higher potential risk of soil erosion in semi-arid regions over IMP.
基金National Natural Science Foundation of China(U2242203, 41975138, 42075086, 42275008)Guangdong Basic and Applied Basic Research Foundation (2023A1515011971)Science Technology Research Program of Guangdong Meteorological Service (GRMC2021Q01)。
文摘The raindrop size distribution(DSD) is a significant characteristic of precipitation physics,which plays a crucial role in improving the accuracy of radar quantitative precipitation estimation and prediction.There is an effect of atmospheric circulation and weather sy stems in South China,with frequent precipitation and differences in regional features,resulting in a limited understanding of the DSD characteristics and their impact mechanisms in the region. In this study,six ground-based two-dimensional video di sdrometers(2DVDs) were used to analyze the DSD of inland and coastal in South China during the five-year(2016-2020) monsoon seasons(April to September),ERA5 reanalysis data and MODIS cloud property products were also used to investigate the dynamics and microphysical characteristics of monsoon precipitation.Compared to inland rainfall,coastal rainfall has a higher conentration of small,medium,and diameter of less than 4.7 mm large raindrops.Considering the contributions to precipitation,the inland and coastal rainfall are dominated by convective rain,accounting for 74.8% and 84.7% of the total rainfall,respectively.The coastal rainfall has a higher the mass-weiglited mean diameter(D_(m)) value than the inland rainfall D_(m) for both the stratiform and convective rainfall.The logarithmic mean of the generalized intercept parameter(log_(10)N_(w)) in inland stratiform rain is greater than that in coastal areas,while convective rain is relatively small.Due to the impact of precipitation types and climate conditions,The Z-R relationship between inland and coastal rainfall also shows obvious differences.Compared to inland areas,there is more frequent convective activity,relatively moist near-surface conditions,and lower cloud droplet number concentrations,which contribute to larger D_(m) of raindrops in coastal areas.This study deepens the understanding of changes in South China's coastal and inland DSD and provides support for improving numerical weather forecasting in the region.
基金supported jointly by the China Meteorological Administration Special Public Welfare Research Fund (Grant No. GYHY201406001)the National (Key) Basic Research and Development (973) Program of China (Grant No. 2012CB417202)the National Natural Science Foundation of China (Grant No. 41175038)
文摘The characteristics of raindrop size distribution （DSD） over the Tibetan Plateau and southern China are studied in this paper, using the DSD data from April to August 2014 collected by HSC-PS32 disdrometers in Nagqu and Yangjiang, com- prising a total of 9430 and 63661-rain raindrop spectra, respectively. The raindrop spectra, characteristics of parameter variations with rainfall rate, and the relationships between reflectivity factor （Z） and rainfall rate （R） are analyzed, as well as their DSD changes with precipitation type and rainfall rate. The results show that the average raindrop spectra appear to be one-peak curves, the number concentration for larger drops increase significantly with rainfall rate, and its value over southern China is much higher, especially in convective rain larger drops, especially for convective rain in southern China. Standardized Gamma distributions better describe DSD for All three Gamma parameters for stratiform precipitation over the Tibetan Plateau are much higher, while its shape parameter （,u） and mass-weighted mean diameter （Dm）, for convective precipitation, are less. In terms of parameter variation with rainfall rate, the normalized intercept parameter （Nw） over the Tibetan Plateau for stratiform rain increases with rainfall rate, which is opposite to the situation in convective rain. The/1 over the Tibetan Plateau for stratiform and convective precipitation types decreases with an increase in rainfall rate, which is opposite to the case for Dm variation. In Z-R relationships, like ＂Z = ARb＇＇, the coefficient A over the Tibetan Plateau is smaller, while its b is higher, when the rain type transfers from stratiform to convective ones. Furthermore, with an increase in rainfall rate, parameters A and b over southern China increase gradually, while A over the Tibetan Plateau decreases sub- stantially, which differs from the findings of previous studies. In terms of geographic location and climate over the Tibetan Plateau and southern China, the precipitation in the pre-flood seasons is dominated by strong convective rain, while weak convective rain occurs frequently in northern Tibet with lower humidity and higher altitude.
基金National Natural Science Foundation of China(40730948,40830958,40921160382)National Grand Fundamental Research 973 Program of China(2009CB421502)
文摘Microphysical characteristics of the raindrop size distribution(RSD)in Typhoon Morakot(2009) have been studied through the PARSIVEL disdrometer measurements at one site in Fujian province,China during the passage of the storm from 7 to 10 August 2009.The time evolution of the RSD reveals different segments of the storm.Significant difference was observed in the microphysical characteristics between the outer rainband and the eyewall;the eyewall precipitation had a broader size distribution(a smaller slope) than the outer rainband and eye region.The outer rainband and the eye region produced stratiform rains while the eyewall precipitation was convective or mixed stratiform-convective.The RSD was typically characterized by a single peak distribution and well represented by the gamma distribution.The relations between the shape(μ)and slope(Λ)of the gamma distribution and between the reflectivity(Z)and rainfall rate(R)have been investigated.Based on the NW-Dm relationships,we suggest that the stratiform rain for the outer rainband and the eye region was formed by the melting of graupel or rimed ice particles,which likely originated from the eyewall clouds.
基金supported by the National Natural Science Foundation of China(Grant Nos.41875170 and 41675136)the National Key Research and Development Program of China(2018YFC1507201 and 2018YFC1507905)the Guangxi Key Research and Development Program(AB20159013)。
文摘The characteristics of the raindrop size distribution(DSD)during regional freezing rain(FR)events that occur throughout the phase change(from liquid to solid)are poorly understood due to limited observations.We investigate the evolution of microphysical parameters and the key formation mechanisms of regional FR using the DSDs from five disdrometer sites in January 2018 in the Jianghan Plain(JHP)of Central China.FR is identified via the size and velocity distribution measured from a disdrometer,the discrete Fréchet distancemethod,surface temperature,human observations,and sounding data.With the persistence of precipitation,the emergence of graupel or snowflakes significantly reduces the proportion of FR.The enhancement of this regional FR event is mainly dominated by the increase in the number concentration of raindrops but weakly affected by the diameters.To improve the accuracy of quantitative precipitation estimation for the FR event,a modified second-degree polynomial relation between the shapeμand slopeΛof gamma DSDs is derived,and a new Z-R(radar reflectivity to rain rate)relationship is developed.The mean values of mass-weighted mean diameters(D_(m))and generalized intercepts(lgN_(w))in FR are close to the stratiform results in the northern region of China.Both the melting of tiny-rimed graupels and large-dry snowflakes are a response to the formation of this regional FR process in the JHP,dominated by the joint influence of the physical mechanism of warm rain,vapor deposition,and aggregation/riming coupled with the effect of weak convective motion in some periods.
基金the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0105)the National Natural Science Foundation of China(Grant No.41775036).
文摘Mêdog and Nagqu are two typical regions of the Tibetan Plateau with different geographical locations and climate regimes.These differences may lead to discrepancies in the raindrop size distributions(DSDs)and precipitation microphysical processes between the two regions.This paper investigates discrepancies in the DSDs using disdrometer data obtained during the rainy season in Mêdog and Nagqu.The DSD characteristics are studied under five different rainfall rate categories and two precipitation types(stratiform and convective).For the total datasets,the number concentrations of drops with diameters D>0.6(D<0.6)mm are higher(lower)in Nagqu than in Mêdog.The fitted normalized gamma distributions of the averaged DSDs for the five rainfall rate categories show that Nagqu has a larger(lower)mass-weighted mean diameter D_(m)(normalized intercept parameter,lgNw)than Mêdog does.The difference in D_(m)between Nagqu and Mêdog increases with the rainfall rate.Convective clusters in Nagqu could be identified as continental-like,while convective precipitation in Mêdog could be classified as maritime-like.The relationships between the shape factorμand slope parameterΛof the gamma distribution model,the radar reflectivity Z,and the rainfall rate R are also derived.Furthermore,the possible causative mechanism for the notable DSD variation between the two regions during the rainy season is illustrated using reanalysis data and automated weather station observations.Cold rain processes are mainly responsible for the lower concentrations of larger drops observed in Nagqu,whereas warm rain prevails in Mêdog,producing abundant small drops.
基金National Key R&D Program of China(2018YFC1507401)Science and Technology Planning Project of Guangdong Province(2017B020244002)+1 种基金National Natural Science Foundation of China(41975138,41705020)Natural Science Foundation of Guangdong Province(2019A1515010814)。
文摘The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation process was selected,and the shape-slope(μ-Λ)relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer(2DVD)at Xinfeng Station,Guangdong Province.Simulated data of the C-band polarimetric radar reflectivity ZHHand differential reflectivity ZDRwere obtained through scattering simulation.The simulation data were combined with DSD fitting to determine the ZDR-Λand log10(ZHH/N0)-Λrelationships.Using Xinfeng C-band polarimetric radar observations ZDRand ZHH,the raindrop Gamma size distribution parametersμ,Λ,and N0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was developed.This research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity(R),mass-weighted mean diameter(Dm)and intercept parameter(Nw)with time obtained by radar retrieval are basically consistent with the observational results of the 2DVD.This scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical model.This method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation estimation.The present research will facilitate radar data assimilation in the future.
基金National Natural Science Foundation of China(42075014,41975138)Natural Science Foundation of Guangdong Province(2022A1515011814,2021A1515011539,2020A1515010602)+3 种基金Open Grants of State Key Laboratory of Severe Weather(2022LASW-B15)Radar Application and Short-term Severe-weather Predictions and Warnings Technology Program(GRMCTD202002)Key Scientific and Technological Research Project of GRMC(GRMC2020Z03)Water Resource Science and Technology Innovation Program of Guangdong Province(2022-02)。
文摘While heavy rainfall frequently takes place in southern China during summer monsoon seasons,quantitative precipitation forecast skills are relatively poor.Therefore,detailed knowledge about the raindrop size distribution(DSD)is useful in improving the quantitative precipitation estimation and forecast.Based on the data during 2018-2022 from 86stations in a ground-based optical disdrometer measurement network,the characteristics of the DSD in Guangdong province are investigated in terms of the particle size distribution(N(D)),mass-weighted mean diameter(Dm) and other integral DSD parameters such as radar reflectivity(Z),rainfall rate(R) and liquid water content(LWC).In addition,the effects of geographical locations,weather systems(tropical cyclones,frontal systems and the summer monsoon) and precipitation types on DSD characteristics are also considered.The results are shown as follows.1) Convective precipitation has a broader N(D) and larger mean particle diameter than the stratiform precipitation,and the DSD observations in Guangdong are consistent with the three-parameter gamma distribution.The relationships between the Z and R for stratiform and convective precipitation are also derived for the province,i.e.,Z=332.34 R1.32and Z=366.26R1.42which is distinctly different from that of the Next-generation Weather Radar(NEXRAD) Z-R relationship in United States.2) In the rainy season(April-September),the Dm, R and LWC are larger than those in the dry season(OctoberMarch).Moreover the above parameters are larger,especially in mid-May,which is the onset of the South China Sea summer monsoon.3) The spatial analysis of DSD shows that the coastal station observations indicate a smaller Dmand a larger normalized intercept parameter(log10Nw),suggestive of maritime-like rainfall.Dmis larger and log10Nwis smaller in the inland area,suggestive of continental-like rainfall.4) Affected by such weather systems as the tropical cyclone,frontal system and summer monsoon,the DSD shows characteristics with distinct differences.Furthermore,frontal system rainfall tends to present a continental-like rainfall,tropical cyclone rainfall tends to have a maritime-like rainfall,and summer monsoon rainfall characteristic are between maritime-and continental-like cluster(raindrop concentration and diameter are higher than continental cluster and maritime cluster,respectively.)
基金supported by the 2019 Basic Research Grants from the Ministry of ResearchTechnology and Higher Education(Grant No.T/3/UN.16.17/PT.01.03/PD-Kebencanaan/2019)。
文摘The diurnal variation in the vertical structure of the raindrop size distribution(RSD)associated with stratiform rain at Kototabang,West Sumatra(0.20°S,100.32°E),was investigated using micro rain radar(MRR)observations from January 2012 to August 2016.Along with the MRR data,the RSD from an optical disdrometer and vertical profile of precipitation from the Tropical Rainfall Measuring Mission were used to establish the microphysical characteristics of diurnal rainfall.Rainfall during 0000–0600 LST and 1800–2400 LST had a lower concentration of small drops and a higher concentration of large drops when compared to rainfall during the daytime(0600–1800 LST).The RSD stratified on the basis of rain rate(R)showed a lower total concentration of drops and higher mass-weighted mean diameter in 0000–0600 LST and1800–2400 LST than in the daytime.During the daytime,the RSD is likely governed by a riming process that can be seen from a weak bright band(BB).On the other hand,during 0000–0600 LST and 1800–2400 LST,the BB was stronger and the rainfall was associated with a higher concentration of midsize and large drops,which could be attributed to more active aggregation right above the melting layer with minimal breakup.Diurnal variation in the vertical profile of RSD led to a different radar reflectivity(Z)–R relationship in the rain column,in which Z during the periods 0000–0600 LST and1800–2400 LST was larger than at the other times,for the same R.
文摘In the issue of rainfall estimation by radar through the necessary relationship between radar reflectivity Z and rain rate R (Z-R), the main limitation is attributed to the variability of this relationship. Indeed, several pre-vious studies have shown the great variability of this relationship in space and time, from a rainfall event to another and even within a single rainfall event. Recent studies have shown that the variability of raindrop size distributions and thereby Z-R relationships is therefore, more the result of complex dynamic, thermody-namic and microphysical processes within rainfall systems than a convective/stratiform classification of the ground rainfall signature. The raindrop number and size at ground being the resultant of various processes mentioned above, a suitable approach would be to analyze their variability in relation to that of Z-R relation-ship. In this study, we investigated the total raindrop concentration number NT and the median volume di-ameter D0 used in numerous studies, and have shown that the combination of these two ‘observed’ parame-ters appears to be an interesting approach to better understand the variability of the Z-R relationships in the rainfall events, without assuming a certain analytical raindrop size distribution model (exponential, gamma, or log-normal). The present study is based on the analysis of disdrometer data collected at different seasons and places in Africa, and aims to show the degree of the raindrop size and number implication in regard to the Z-R relationships variability.
基金jointly sponsored by the Second Tibetan Plateau Atmospheric Sciences Experiment(STEP)(Grant No.2019QZKK010406)the National Natural Science Foundation of China(Grant No.42165008)Natural Science Foundation of Technology Department of Qinghai Province(Grant No.2021-ZJ-745)。
文摘Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau.The analysis focuses on convective and stratiform precipitation at high altitudes from 2434 m to 4202 m.The results show that the contribution of stratiform and convective precipitation with rain rate between 1≤R<5 mm h^(-1)to the total precipitation increases with altitude,and the raindrop scale and number concentration of convective precipitation is larger than that for stratiform precipitation.The droplet size spectra of both stratiform and convective precipitation shows a single peak with a peak particle size between 0.31–0.50 mm,and they have essentially the same peak particle size and number concentration at the same altitude.The maximum spectral widths of stratiform clouds are between 4 mm and 5 mm,while those of convective clouds range from 4 mm to 8 mm.The Gamma distribution is more suitable than the Marshall-Palmer distribution in terms of the actual raindrop spectrum distribution.The stratiform precipitation particles are smaller with higher number concentration,while the opposite is true for the convective precipitation particles.The convective precipitation particles drop faster than stratiform precipitation particles when the particle size exceeds 2 mm,and the falling velocity of raindrops after standard curve fitting is underestimated during the observation period.Moreover,conventional radar estimation methods would underestimate the precipitation in the Northeastern Tibetan Plateau.
基金Supported by the Hubei Provincial Natural Science Foundation and Meteorological Innovation and Development Project of China(2023AFD096,2022CFD122,and 2023AFD100)Science and Technology Development Fund of Hubei Meteorological Bureau(2023Y18)+3 种基金Qinghai Province 2023 Key R&D and Transformation Plan(2023-SF-111)Special Program for Innovation and Development of China Meteorological Administration(CXFZ2022J010)Natural Science Foundation of Wuhan(2024020901030454)CMA Meteorological Observation Centre Field Experiment Project in 2024(GCSYJH24-30)。
文摘Freezing rain(FZR)presents significant risks to energy,transportation,and agriculture,leading to substantial economiclossesandcasualties,particularlyinsouthwestern,central,andeasternChina,withonlyoccasionaloccurrences in northern China.This study investigates an extreme,large-scale FZR event that occurred during 8–9 November 2021 in Heilongjiang Province of Northeast China,marking the region’s most intense FZR since 1958.Surface station observations revealed distinct characteristics of the FZR,and the stations were classified into three types by using the k-means clustering:stations with continuous FZR(FZR_Con),stations with FZR of mixed hydrometeor types(FZR_Mix),and stations with FZR transitioning to rain(FZR_Rain).Vertical atmospheric temperature and humidity profiles significantly influenced the raindrop size distribution(DSD)for the three station types.All three station types exhibited an inversion layer in the upper atmosphere,though they formed through two distinct mechanisms:(1)the supercooled warm rain mechanism and(2)the melting mechanism.This study found that the massweighted mean diameters(D--m)were larger than those observed in FZR events in central China and in stratiform rain in northern and northwestern China.FZR_Mix,which formed through the supercooled warm rain mechanism,exhibited the largest D_(m) among the three types.In contrast,FZR_Con and FZR_Rain formed through the melting mechanism,involving the melting of ice crystals and snow particles.The drier refreezing layer in FZR_Rain,compared to FZR_Con,resulted in a lower normalized number concentration(N_(w))and a larger D_(m).Positive exponential relationships between D_(m) and R(precipitation rate),as well as N_(w) and R,across all FZR types,highlighting dominant role of microphysical processes such as collision and coalescence.Variations in the gamma distribution parameters—shape(μ)and slope(λ)—as well as in the radar Z–R relationships among the FZR types further underscore differences in the microphysical processes and regional precipitation characteristics.This study enhances our understanding of the macro-and microphysical properties of FZR formed through different mechanisms,providing valuable reference for improved radar-based precipitation estimation in mid-and high-latitude regions.
基金Supported by the National Key Research and Development Program of China(2023YFC3007501)Natural Science Foundation of Fujian Province of China(2023J011337)Innovation Ability Promotion Plan Project of Chengdu University of Information Technology(KYQN202307)。
文摘Knowledge of raindrop size distribution(RSD)is essential for understanding microphysical processes occurring within cloud and precipitation systems,as well as for enhancing the capabilities of numerical models and radar-based quantitative precipitation estimation(QPE).However,observation and study of RSD,especially its temporal and spatial variability,remain quite limited in specific regions.One such region is Southeast China.In this paper,four years of disdrometer data from a south coastal plain site(CPS)and a north hilly inland site(HIS)in the Fujian Province of Southeast China are analyzed and compared to elucidate the characteristics and discrepancies of RSD between these two distinct climatological sites.On this basis,empirical relations between the parameters of Gamma distribution and between radar reflectivity factor(Z)and rain rate(R)are proposed.The results are summarized as follows.(1)In the cases of light to moderate rains,HIS exhibits a higher(lower)concentration of small-size(midsize and large)raindrops with diameters of D<1 mm(1≤3 and D≥3 mm),compared to CPS.Conversely,as the rain intensity increases,the raindrop concentrations across all size categories at CPS gradually exceed those at HIS.(2)RSDs at both sites broaden and exhibit elevated concentrations across most diameter categories as the rain rate increases.(3)For rainfalls with rain rates below 5 mm h^(-1),collision and coalescence dominate,resulting in unimodal rain spectra at both sites;whereas for stronger rainfalls,breakup intensifies,leading to the development of bimodal rain spectra.(4)HIS experiences more stratiform rains but fewer,weaker convective rains than CPS.Stratiform RSD at HIS possesses more small and large raindrops but fewer midsize raindrops compared to CPS,whereas convective RSD at CPS possesses higher concentrations across all diameter categories.(5)Accordingly,specific Z–R relations at these two sites are proposed and validated for two real cases,demonstrating that the accuracy of radar QPE is effectively improved based on the proposed Z–R relations.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2015CB452802)Natrional Key Research and Development Program of China(2017YFC1501701)+3 种基金National Natural Science Foundation of China(41475102,41705020,and 41705120)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406013)Guangdong Province Science and Technology Project(2015B020217001)Natural Science Foundation of Guangdong Province(2016A030313141)
文摘According to the statistical shape-slope （μ-A） relationship observed for the first time by several 2D-Video-Distro-meters （2DVD） in southern China, a constrained gamma （C-G） model was proposed for the retrieval of rain drop size distributions （DSDs） from Guangzhou S-band polarimetric radar observations. Two typical precipitation processes were selected to verify the accuracy of the retrieval scheme. The p-A relationship： A = 0.0241μ^2 ＋ 0.867μ ＋ 2.453 was obtained based on the 2DVD observation results from at Huizhou Longmen station, which is a very representat-ive location in the area. Relying on the Guangzhou polarimetric radar measurements of radar reflectivity （ZHH） and differential reflectivity （ZDR）, the gamma （F） size distribution parameters （No, μ, and A） can be retrieved by the C-G model retrieval scheme. The results show that the Guangzhou polarimetric radar retrievals of DSDs were close to the 2DVD observations at Guangzhou Maofengshan station. The rain rate, mass mean diameter, and normalized inter-cept parameter of radar retrievals were in good agreement with the 2DVD observations, and the relative errors were less than 10%. The overall accuracy of the retrieval scheme was high. The retrieval scheme has established the rela-tionship between the polarimetric radar measurements and gamma size distribution parameters. It will be helpful to in-depth research and application of the dual-polarization radar data in microphysical precipitation processes analysis, as well as convection-resolved numerical model data assimilation and prediction effect evaluation.
基金Supported by the National Key Research and Development Program of China(2022YFC3003901)National Natural Science Foundation of China(42305087 and 42105141)+2 种基金Science and Technology Innovation Project for Ecosystem Construction of Zhengzhou Supercomputing Center in Henan Province(201400210800)Meteorological Joint Project of Henan Provincial Science and Technology(222103810094 and 232103810091)Basic Research Fund of Chinese Academy of Meteorological Sciences(451490 and 2023Z008).
文摘In this study,a regional Parsivel OTT disdrometer network covering urban Zhengzhou and adjacent areas is employed to investigate the temporal-spatial variability of raindrop size distributions(DSDs)in the Zhengzhou extreme rainfall event on 20 July 2021.The rain rates observed by disdrometers and rain gauges from six operational sites are in good agreement,despite significant site-to-site variations of 24-h accumulated rainfall ranging from 198.3 to 624.1 mm.The Parsivel OTT observations show prominent temporal-spatial variations of DSDs,and the most drastic change was registered at Zhengzhou Station where the record-breaking hourly rainfall of 201.9 mm over 1500-1600 LST(local standard time)was reported.This hourly rainfall is characterized by fairly high concentrations of large raindrops,and the mass-weighted raindrop diameter generally increases with the rain rate before reaching the equilibrium state of DSDs with the rain rate of about 50 mm h^(−1).Besides,polarimetric radar observations show the highest differential phase shift(K_(dp))and differential reflectivity(Z_(dr))near surface over Zhengzhou Station from 1500 to 1600 LST.In light of the remarkable temporal-spatial variability of DSDs,a reflectivity-grouped fitting approach is proposed to optimize the reflectivity-rain rate(Z-R)parameterization for radar quantitative precipitation estimation(QPE),and the rain gauge measurements are used for validation.The results show an increase of mean bias ratio from 0.57 to 0.79 and a decrease of root-mean-square error from 23.69 to 18.36 for the rainfall intensity above 20.0 mm h^(−1),as compared with the fixed Z-R parameterization.This study reveals the drastic temporal-spatial variations of rain microphysics during the Zhengzhou extreme rainfall event and warrants the promise of using reflectivity-grouped fitting Z-R relationships for radar QPE of such events.
基金funded by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program,Grant No.2019QZKK0105Basic Research Fund of CAMS(2023Z009)Science and Technology Development Fund of Chinese Academy of Meteorological Sciences(2023KJ041).
文摘Mêdog,located at the entrance of the water vapour channel of the Yarlung Zangbo Grand Canyon,and it has the highest rainfall and lowest elevation on the Tibetan Plateau(TP).The droplet size distribution(DSD)and microphysical processes associated with rainfall usually exhibit different characteristics under different synoptic patterns.In this study,an objective classification method is used to categorize the synoptic patterns that affect heavy rainfall(daily rainfall amounts>10 mm)in Mêdog into four patterns:southwest airflow(SWA),southern-branch trough(SBT),intense baroclinicity(IBC),and terrain-forced precipitation(TFP).SWA occurs most frequently(approximately 70%)with a mean daily rainfall of~22 mm,while TFP has the lowest occurrence frequency(7.7%)but the highest mean daily rainfall(29 mm).Both SBT and IBC exhibit occurrence frequencies around 12%.Among these patterns,the SWA pattern predominantly occurs during the monsoon season with abundant moisture and the lowest concentration of small raindrops.In contrast,the TFP pattern exhibits the highest concentration of large raindrops and the widest DSD spectrum,which can be attributed to the frequent convective activities in this area.As a result,compared with those of the other three synoptic patterns,the TFP pattern exhibits a larger mass-weighted mean diameter(D_(m))and higher rain rate(R).For stratiform rainfall,the difference in D_(m)among the four synoptic patterns can be neglected.The largest(smallest)average lgNW-value is observed in the SWA(IBC)pattern.Regarding convective rainfall,IBC dominated by northerly cold air exhibits mixed-phase processes characterized by larger raindrops and lower concentrations,resembling continental-like rainfall.In contrast,SWA occurring in monsoon season shows high concentrations of small raindrops,deeming it similar to maritime-like rainfall.In terms of the derived relationships,there are significant differences in the D_(m)-R andμ-Λrelationships among the four synoptic patterns.In addition,the diurnal variation in the DSD is analyzed in terms of the four synoptic patterns.These findings can improve the understanding of the microphysical processes of heavy rainfall events under different synoptic patterns and provide a reference for microphysical parameterizations of numerical models.
文摘In this study, a framework is given by which air/space-borne dual-wavelength radar data can be used to estimate the characteristic parameters of hydrometeors. The focus of the study is on the Global Precipitation Measurement （GPM） precipitation radar, a dual-wavelength radar that will operate in the Ku （13.6 GHz） and Ka （35 GHz） bands. A key aspect of the retrievals is the relationship between the differential frequency ratio （DFR） and the median volume diameter, Do, and its dependence on the phase state of the hydrometeors. It is shown that parametric plots of Do and particle concentration in the plane of the DFR and the radar reflectivity factor in the Ku band can be used to reduce the ambiguities in deriving Do from DFR. A self-consistent iterative algorithm, which does not require the use of an independent pathattenuation constraint, is examined by applying it to the apparent radar reflectivity profiles simulated from a drop size distribution （DSD） model. For light to moderate rain, the self-consistent rain profiling approach converges to the correct solution only if the same shape factor of the Gamma distributions is used both to generate and retrieve the rain profiles. On the other hand, if the shape factors differ, the iteration generally converges but not to the correct solution. To further examine the dual-wavelength techniques, the selfconsistent iterative algorithm, along with forward and backward rain profiling algorithms, are applied to measurements taken from the 2nd generation Precipitation Radar （PR-2） built by the Jet Propulsion Laboratory. Consistent with the model results, it is found that the estimated rain profiles are sensitive to the shape factor of the size distribution when the iterative, self-consistent approach is used but relatively insensitive to this parameter when the forward- and backward-constrained approaches are used.
基金jointly supported by Guangdong Basic and Applied Basic Research Foundation (2021A1515011415)the National Natural Science Foundation of China (Grant Nos. 42075086, 41975138, and 42005062)the Natural Science Foundation of Guangdong Province, China (2019A1515010814)。
文摘In this paper, the evolution of the microphysical characteristics in different regions(eyewall, inner core, and outer rainbands) and different quadrants [downshear left(DL), downshear right(DR), upshear left(UL), and upshear right(UR)]during the final landfall of Typhoon Ewiniar(2018) is analyzed using two-dimensional video disdrometer and S-band polarimetric radar data collected in Guangdong, China. Due to the different types of underlying surfaces, the periods before landfall(mainly dominated by underlying sea surface) and after landfall(mainly dominated by underlying land surface) are also analyzed. Both before landfall and after landfall, the downshear quadrants had the dominate typhoon precipitation. The outer rainbands had more graupel than the inner core, resulting in a larger radar reflectivity, differential reflectivity, specific differential phase shift, and mass-weighted mean diameter below the melting layer. Compared with other regions, the eyewall region had the smallest mean logarithmic normalized intercept parameter before landfall and the smallest mean mass-weighted mean diameter and the largest mean logarithmic normalized intercept parameter after landfall. The hydrometeor size sorting was obvious in the eyewall and inner core(especially in the eyewall) after landfall. A high concentration of large raindrops fell in the DL quadrant, and more small raindrops fell in the UR quadrant. Although the icephase process and warm rain process were both important in the formation of tropical cyclone precipitation, the warm rain process(ice-phase process) contributed more liquid water before landfall(after landfall). This investigation provides a reference for improving the microphysical parameterization scheme in numerical models.
基金National key research and development program of China(2022YFC3003902)National Natural Science Foundation of China(U2242203,42075086,41975138)Guangdong Basic and Applied Basic Research Foundation(2023A1515011971,2021A1515011415,2019A1515010814)。
文摘During the April-June raining season,warm-sector heavy rainfall(WR) and frontal heavy rainfall(FR) often occur in the south of China,causing natural disasters.In this study,the microphysical characteristics of WR and FR events from 2016 to 2022 are analyzed by using 2-dimensional video disdrometer(2DVD) data in the south of China.The microphysical characteristics of WR and FR events are quite different.Compared with FR events,WR events have higher concentration of D<5.3 mm(especially D <1 mm),leading to higher rain rates.The mean values of Dmand lgNwof WR events are higher than that of FR events.The microphysical characteristics in different rain rate classes(C1:R~5-20 mm h-1,C2:R~20-50 mm h-1,C3:R~50-100 mm h^(-1),and C4:R> 100 mm h^(-1)) for WR and FR events are also different.Raindrops from C3 contribute the most to the precipitation of WR events,and raindrops from C2 contribute the most to the precipitation of FR events.For C2 and C3,compared with FR events,WR events have higher concentration of D <1 mm and D~3-4.5 mm.Moreover,the shape and slope(μ-A) relationships and the radar reflectivity and rain rate(Z-R) relationships of WR and FR events are quite different in each rain rate class.The investigation of the difference in microphysical characteristics between WR and FR events provide useful information for radar-based quantitative precipitation estimation and numerical prediction.
基金funded by the second Tibetan Plateau Scientific Expe-dition and Research Program(2019QZKK0604).
文摘Raindrop size distribution(DSD)plays a crucial role in enhancing the accuracy of radar quantitative precipitation estimates in the Tibetan Plateau(TP).However,there is a notable scarcity of long-term,high-resolution observations in this region.To address this issue,long-term observations from a two-dimensional video disdrometer(2DVD)were leveraged to refine the radar and satellite-based algorithms for quantifying precipitation in the hinterland of the TP.It was observed that weak precipitation(R<1,mm h-1)accounts for 86%of the total precipitation time,while small raindrops(D<2 mm)comprise 99%of the total raindrop count.Furthermore,the average spectral width of the DSD increases with increasing rain rate.The DSD characteristics of convective and stratiform precipitation were discussed across five different rain rates,revealing that convective precipitation in Yangbajain(YBJ)exhibits characteristics similar to maritime-like precipitation.The constrained relationships between the slopeΛand shapeμ,D_(m)and N_(w)of gamma DSDs were derived.Additionally,we established a correlation between the equivalent diameter and drop axis ratio and found that raindrops on the TP attain a nearly spherical shape.Consequently,the application of the rainfall retrieval algorithms of the dual-frequency precipitation radar in the TP is improved based on the statistical results of the DSD.
