Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical para...Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical parameters. To study such an influence, the present study utilized boundary layer wind profiler radar measurements. The separation point of the radar power spectral density data was carefully selected to classify rainfall and turbulence signals;the turbulent dissipation rate ε and rainfall microphysical parameters can be retrieved to analyze the relationship betweenε and microphysical parameters. According to the retrievals of two rainfall periods in Beijing 2016, it was observed that(1) ε in the precipitation area ranged from 10^(-3.5) to 10^(-1) m^(2) s^(-3) and was positively correlated with the falling velocity spectrum width;(2) interactions between turbulence and raindrops showed that small raindrops got enlarge through collision and coalescence in weak turbulence, but large raindrops broke up into small drops under strong turbulence, and the separation value of ε being weak or strong varied with rainfall attributes;(3) the variation of rainfall microphysical parameters(characteristic diameters, number concentration, rainfall intensity, and water content) in the middle stage were stronger than those in the early and the later stages of rainfall event;(4) unlike the obvious impacts on raindrop size and number concentration, turbulence impacts on rain rate and LWC were not significant because turbulence did not cause too much water vapor and heat exchange.展开更多
The Penn State/ NCAR Mesoscale Model (MM5) is used to simulate the precipitation event that occurred during 1–2 May 1994 to the south of the Yangtze River. In five experiments the Kain–Fritsch scheme is made use of ...The Penn State/ NCAR Mesoscale Model (MM5) is used to simulate the precipitation event that occurred during 1–2 May 1994 to the south of the Yangtze River. In five experiments the Kain–Fritsch scheme is made use of for the subgrid–scale convective precipitation, but five different resolvable–scale microphysical parameterization schemes are employed. They are the simple super-saturation removal scheme, the warm rain scheme of Hsie et al. (1984), the simple ice scheme of Dudhia (1989), the complex mixed–phase scheme developed by Reisner et al. (1993), and the GSFC microphysical scheme with graupel. Our interest is how the various resolvable-scale schemes affect the domain-averaged precipitation, the precipitation distribution, the sea level pressure, the cloud water and the cloud ice. Through a series of experiments about a warm sector rainfall case, results show that although the different resolvable-scale scheme is used, the differences of the precipitation characteristics among all five runs are not very obvious. However, the precipitation is over-predicted and the strong mesoscale low is produced by the simple super-saturation removal scheme. The warm rain scheme with the inclusion of condensation and evaporation under-predicts the precipitation and allows the cloud water to reach the 300 hPa level. The scheme of the addition of graupel increases the resolvable-scale precipitation by about 20%-30%. The inclusion of supercooled liquid water in the grid-scale scheme does not affect significantly the results. Key words Mesoscale model - Precipitation - Resolvable-scale microphysical parameterization展开更多
A heavy rainfall event in south China was simulated by the Weather Research and Forecasting(WRF) model with three microphysics schemes, including the Morrison scheme, Thompson scheme, and Milbrandt and Yau scheme(MY),...A heavy rainfall event in south China was simulated by the Weather Research and Forecasting(WRF) model with three microphysics schemes, including the Morrison scheme, Thompson scheme, and Milbrandt and Yau scheme(MY), which aim to evaluate the capability to reproduce the precipitation and radar echo reflectivity features, and to evaluate evaluate their differences in microphysics and the associated thermodynamical and dynamical feedback. Results show that all simulations reproduce the main features crucial for rainfall formation. Compared with the observation, the MY scheme performed better than the other two schemes in terms of intensity and spatial distribution of rainfall. Due to abundant water vapor, the accretion of cloud droplets by raindrops was the dominant process in the growth of raindrops while the contribution of melting was a secondary effect. Riming processes, in which frozen hydrometeors collect cloud droplets mainly, contributed more to the growth of frozen hydrometeors than the Bergeron process. Extremely abundant snow and ice were produced in the Thompson and MY schemes respectively by a deposition process. The MY scheme has the highest condensation and evaporation, but the lowest deposition. As a result, in the MY scheme, the enhanced vertical gradient of condensation heating and evaporation cooling at low levels produces strong positive and weak negative potential vorticity in Guangdong, and may favor the formation of the enhanced rainfall center over there.展开更多
Accurate descriptions of cloud droplet spectra from aerosol activation to vapor condensation using microphysical parameterization schemes are crucial for numerical simulations of precipitation and climate change in we...Accurate descriptions of cloud droplet spectra from aerosol activation to vapor condensation using microphysical parameterization schemes are crucial for numerical simulations of precipitation and climate change in weather forecasting and climate prediction models.Hence,the latest activation and triple-moment condensation schemes were combined to simulate and analyze the evolution characteristics of a cloud droplet spectrum from activation to condensation and compared with a high-resolution Lagrangian bin model and the current double-moment condensation schemes,in which the spectral shape parameter is fixed or diagnosed by an empirical formula.The results demonstrate that the latest schemes effectively capture the evolution characteristics of the cloud droplet spectrum during activation and condensation,which is in line with the performance of the bin model.The simulation of the latest activation and condensation schemes in a parcel model shows that the cloud droplet spectrum gradually widens and exhibits a multimodal distribution during the activation process,accompanied by a decrease in the spectral shape and slope parameters over time.Conversely,during the condensation process,the cloud droplet spectrum gradually narrows,resulting in increases in the spectral shape and slope parameters.However,these double-moment schemes fail to accurately replicate the evolution of the cloud droplet spectrum and its multimodal distribution characteristics.Furthermore,the latest schemes were coupled into a 1.5D cumulus model,and an observation case was simulated.The simulations confirm that the cloud droplet spectrum appears wider at the supersaturated cloud base and cloud top due to activation,while it becomes narrower at the middle altitudes of the cloud due to condensation growth.展开更多
By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 ...By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. （1） The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. （2） The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar refl ectivity factor is larger （over-10 dBZ）. （3） The radar’s sensitivity is comparatively higher because the minimum radar refl ectivity factor is about-35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio （LDR） of stratocumulus （commonly -11 to -14 dBZ; decreases with increasing turbulence）. （4） After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle eff ective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar refl ectivity factor.展开更多
A set of microphysics equations is scaled based on the convective length and velocity scales. Comparisons are made among the dynamical transport and various microphysical processes. From the scaling analysis, it becom...A set of microphysics equations is scaled based on the convective length and velocity scales. Comparisons are made among the dynamical transport and various microphysical processes. From the scaling analysis, it becomes apparent which parameterized microphysical processes present off-scaled influences in the integration of the set of microphysics equations. The variabilities of the parameterized microphysical processes are also studied using the approach of a controlled parameter space. Given macroscopic dynamic and thermodynamic conditions in different regions of convective storms, it is possible to analyze and compare vertical profiles of these processes. Bulk diabatic heating profiles for a cumulus convective updraft and downdraft are also derived from this analysis. From the two different angles, the scale analysis and the controlled-parameter space approach can both provide an insight into and an understanding of microphysics parameterizations.展开更多
The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parame...The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parameter in the commonly used bulk double-moment schemes, the cloud droplet spectra cannot reasonably be described during the condensation process. Therefore, a newly-developed triple-parameter condensation scheme with the shape parameter diagnosed through the number concentration, cloud water content, and reflectivity factor of cloud droplets can be applied to improve the evolution of the cloud droplet spectrum. The simulation with the new parameterization scheme was compared to those with a high-resolution Lagrangian bin scheme, the double-moment schemes in a parcel model, and the observation in a 1.5D Eulerian model that consists of two cylinders. The new scheme with the shape parameter varying with time and space can accurately simulate the evolution of the cloud droplet spectrum. Furthermore, the volume-mean radius and cloud water content simulated with the new scheme match the Lagrangian analytical solutions well, and the errors are steady, within approximately 0.2%.展开更多
There are more uncertainties with ice hydrometeor representations and related processes than liquid hydrometeors within microphysics parameterization(MP)schemes because of their complicated geometries and physical pro...There are more uncertainties with ice hydrometeor representations and related processes than liquid hydrometeors within microphysics parameterization(MP)schemes because of their complicated geometries and physical properties.Idealized supercell simulations are produced using the WRF model coupled with“full”Hebrew University spectral bin MP(HU-SBM),and NSSL and Thompson bulk MP(BMP)schemes.HU-SBM downdrafts are typically weaker than those of the NSSL and Thompson simulations,accompanied by less rain evaporation.HU-SBM produces more cloud ice(plates),graupel,and hail than the BMPs,yet precipitates less at the surface.The limiting mass bins(and subsequently,particle size)of rimed ice in HU-SBM and slower rimed ice fall speeds lead to smaller melting-level net rimed ice fluxes than those of the BMPs.Aggregation from plates in HU-SBM,together with snow–graupel collisions,leads to a greater snow contribution to rain than those of the BMPs.Replacing HU-SBM’s fall speeds using the formulations of the BMPs after aggregating the discrete bin values to mass mixing ratios and total number concentrations increases net rain and rimed ice fluxes.Still,they are smaller in magnitude than bulk rain,NSSL hail,and Thompson graupel net fluxes near the surface.Conversely,the melting-layer net rimed ice fluxes are reduced when the fall speeds for the NSSL and Thompson simulations are calculated using HU-SBM fall speed formulations after discretizing the bulk particle size distributions(PSDs)into spectral bins.The results highlight precipitation sensitivity to storm dynamics,fall speed,hydrometeor evolution governed by process rates,and MP PSD design.展开更多
Typhoons,characterized by their high destructive potential,significantly impact coastal residents’lives and property safety.To optimize numerical models’typhoon simulation,carefully selecting appropriate physical pa...Typhoons,characterized by their high destructive potential,significantly impact coastal residents’lives and property safety.To optimize numerical models’typhoon simulation,carefully selecting appropriate physical para-meterization schemes is crucial,offering robust support for disaster prevention and reduction efforts.This study focuses on Typhoon Mujigae,conducting a comparative analysis of different physical parameterization schemes(microphysics,cu-mulus parameterization,shortwave radiation,and longwave radiation)in WRF simulations.The key findings are as follows:cumulus and microphysics parameterization schemes notably influence the simulation of typhoon tracks and intensity,while the impact of longwave and shortwave radiation schemes is relatively minor.Typhoon intensity is more sensitive to the choice of parameterization schemes than track.Together,the Kain-Fritsch cumulus convection scheme,WRF Single Moment 5-class scheme,and Dudhia/RRTM radiation scheme yield the best intensity simulation results.Compared with the Betts-Miller-Janjićand Grell 3D scheme,the use of the Kain-Fritsch scheme results in a clearer,taller eyewall and more symmetric deep convection,enhancing precipitation and latent heat release,and consequently improving the simulated typhoon intensity.More complex microphysics schemes like Purdue Lin,WRF Single Moment 5-class,and WRF Double Moment 6-class perform better in simulations,while simpler schemes like Kessler and WSM3 exhibit significant deviations in typhoon simulations.Particularly,the large amount of supercooled water clouds simulated by the Kessler scheme is a major source of bias.Furthermore,a coupling effect exists between cumulus convection and mi-crophysics parameterization schemes,and only a reasonable combination of both can achieve optimal simulation results.展开更多
Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes（also called autoconversion） are proposed based on a large number of Cloud Sat observations between June2006 and Apri...Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes（also called autoconversion） are proposed based on a large number of Cloud Sat observations between June2006 and April 2011 over Asian land areas. The emphasis is given to the vertical distribution of liquid water content（LWC）, particularly, the threshold values of LWC for autoconversion. The results warrant a new approach to the numerical parameterization of autoconversion in warm clouds. One feature of this new approach is that the autoconversion threshold, which has been treated as a constant in previous parameterization schemes, is diagnosed as a function of altitude by using a relationship between LWC and height（H）derived from Cloud Sat observations： LWCdig =-500.0 ln（ H/9492.2）. Under this framework, the threshold LWC decreases with increasing H, allowing autoconversion to occur in clouds with low LWC（approximately0.3 g m^-3） at levels above 5.5 km. Autoconversion rates calculated based on the new parameterization are compared to those calculated based on several commonly used parameterization schemes over a range of LWCs from 0.01 to 1.0 g m^-3. The new scheme provides reasonable simulations of autoconversion at various vertical levels.展开更多
The understanding of the cloud processes of snowfall is essential to the artificial enhancement of snow and the numerical simulation of snowfall. The mesoscale model MM5 is used to simulate a moderate snowfall event i...The understanding of the cloud processes of snowfall is essential to the artificial enhancement of snow and the numerical simulation of snowfall. The mesoscale model MM5 is used to simulate a moderate snowfall event in North China that occurred during 20-21 December 2002. Thirteen experiments are performed to test the sensitivity of the simulation to the cloud physics with different cumulus parameterization schemes and different options for the Goddard cloud microphysics parameterization schemes. It is shown that the cumulus parameterization scheme has little to do with the simulation result. The results also show that there are only four classes of water substances, namely the cloud water, cloud ice, snow, and vapor, in the simulation of the moderate snowfall event. The analysis of the cloud microphysics budgets in the explicit experiment shows that the condensation of supersaturated vapor, the depositional growth of cloud ice, the initiation of cloud ice, the accretion of cloud ice by snow, the accretion of cloud water by snow, the deposition growth of snow, and the Bergeron process of cloud ice are the dominant cloud microphysical processes in the simulation. The accretion of cloud water by snow and the deposition growth of the snow are equally important in the development of the snow.展开更多
The Weather Research Forecast model (WRF) configured with high resolution and NCEP 1°×1° reanalysis data were used to simulate the development of a tropical deep convection over the Tiwi Islands,norther...The Weather Research Forecast model (WRF) configured with high resolution and NCEP 1°×1° reanalysis data were used to simulate the development of a tropical deep convection over the Tiwi Islands,northern Australia,and to investigate the sensitivity of model results to model configuration and parameterization schemes of microphysical processes.The simulation results were compared with available measurements.The results show that the model can reproduce most of the important characteristics of the observed diurnal evolution of the convection,including the initiation of convection along the sea-breeze front,which is then reinforced by downdraft outflows,merging of cells and the formation of a deep convective system.However,further improvement is needed to simulate more accurately the location and the time for initiation of the deep convective system.Sensitivity tests show that double-nesting schemes are more accurate than the non-nesting schemes in predicting the distribution and intensity of precipitation as far as this particular case is concerned.Additionally,microphysical schemes also have an effect on the simulated amount of precipitation.It is shown that the best agreement is reached between the simulation results and observations when the Purdue Lin scheme is used.展开更多
This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retriev...This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retrieval of raindrop size distributions（RSDs） is accomplished through eliminating vertical air motion and isolating the terminal fall velocity of raindrops in the observed Doppler velocity spectrum.The microphysical properties of raindrops in a broad stratiform region with weak convective cells are studied using data collected from a 1320-MHz wind profiler radar in Huayin,Shaanxi Province on 14 May 2009.RSDs and gamma function parameters are retrieved at altitudes between 700 and 3000 m above the surface,below a melting layer.It is found that the altitude of the maximum number of raindrops was closely related to the surface rain rate.The maximum number of large drops was observed at lower altitudes earlier in the precipitation event but at higher altitudes in later periods,suggesting decreases in the numbers of large and medium size raindrops.These decreases may have been caused by the breakup of larger drops and evaporation of smaller drops as they fell.The number of medium size drops decreased with increasing altitude.The relationship between reflectivity and liquid water content during this precipitation event was Z = 1.69×10~4M^（1.5）,and the relationship between reflectivity and rain intensity was Z = 256I^（1.4）.展开更多
A large number of in-situ measurements of cloud-precipitation microphysical properties have been made since 1960, including measurements of particle size distribution, particle concentration, and liquid water content ...A large number of in-situ measurements of cloud-precipitation microphysical properties have been made since 1960, including measurements of particle size distribution, particle concentration, and liquid water content of clouds and rain. These measurements have contributed to considerable progress in understanding microphysical processes in clouds and precipitation and significant improvements in parameterizations of cloud microphysics in numerical models. This work reviews key findings regarding cloud-precipitation microphysics over China. The total number concentrations of various particles vary significantly, with certain characteristic spatial scales. The size distributions of cloud droplets in stratiform clouds can generally be fit with gamma distributions, but the fit parameters cover a wide range. Raindrop size distributions（RSDs）associated with stratiform clouds can be fit with either exponential or gamma distributions, while RSDs associated with convective or mixed stratiform-cumuliform clouds are best fit with gamma distributions.Concentrations of ice nuclei（IN） over China are higher than those observed over other regions, and increase exponentially as temperature decreases. The particle size distributions of ice crystals, snow crystals, and hailstones sampled at a variety of locations can be reliably approximated by using exponential distributions,while aerosol particle size distributions are best described as the sum of a modified gamma distribution and a Junge power-law distribution. These results are helpful for evaluating and improving the fidelity of physical processes and hydrometeor fields simulated by microphysical parameterizations. The comprehensive summary and analysis of previous work presented here also provide useful guidelines for the design of future observational programs.展开更多
In order to study mechanisms of hailstone formation and hail suppression with seeding and to obtain optimum seeding technique for hail cloud,a 3-D compressive numerical seeding model for hail cloud is developed.The wa...In order to study mechanisms of hailstone formation and hail suppression with seeding and to obtain optimum seeding technique for hail cloud,a 3-D compressive numerical seeding model for hail cloud is developed.The water substance in hail cloud is divided into 8 categories,i.e.,water vapor,cloud droplet,raindrop,ice crystal,snow.graupel,frozen drop and hail,and the detailed microphysical processes are described in a spectrum with two variable parameters and more reasonable particle number/size distributions.Then,the model is able to predict concentration and water content of various particles.Especially.it can calculate the number of hailstones whose cores are graupel or frozen drop and apply to study mechanism of hailstone formation. Additionally,a conservative equation of AgI as seeding or glacigenous agent is found and nucleation by condensation of artificial nucleus,and nucleation by freezing of cloud droplet or rain drop which contact with AgI particle are considered.The dynamic energy flux of hail shooting on ground is used to verify seeding effect.Therefore the model is also used to study mechanism of hail suppression with seeding and the seeding technique,展开更多
基金National Key R&D Program of China(2018YFC1506102)。
文摘Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical parameters. To study such an influence, the present study utilized boundary layer wind profiler radar measurements. The separation point of the radar power spectral density data was carefully selected to classify rainfall and turbulence signals;the turbulent dissipation rate ε and rainfall microphysical parameters can be retrieved to analyze the relationship betweenε and microphysical parameters. According to the retrievals of two rainfall periods in Beijing 2016, it was observed that(1) ε in the precipitation area ranged from 10^(-3.5) to 10^(-1) m^(2) s^(-3) and was positively correlated with the falling velocity spectrum width;(2) interactions between turbulence and raindrops showed that small raindrops got enlarge through collision and coalescence in weak turbulence, but large raindrops broke up into small drops under strong turbulence, and the separation value of ε being weak or strong varied with rainfall attributes;(3) the variation of rainfall microphysical parameters(characteristic diameters, number concentration, rainfall intensity, and water content) in the middle stage were stronger than those in the early and the later stages of rainfall event;(4) unlike the obvious impacts on raindrop size and number concentration, turbulence impacts on rain rate and LWC were not significant because turbulence did not cause too much water vapor and heat exchange.
文摘The Penn State/ NCAR Mesoscale Model (MM5) is used to simulate the precipitation event that occurred during 1–2 May 1994 to the south of the Yangtze River. In five experiments the Kain–Fritsch scheme is made use of for the subgrid–scale convective precipitation, but five different resolvable–scale microphysical parameterization schemes are employed. They are the simple super-saturation removal scheme, the warm rain scheme of Hsie et al. (1984), the simple ice scheme of Dudhia (1989), the complex mixed–phase scheme developed by Reisner et al. (1993), and the GSFC microphysical scheme with graupel. Our interest is how the various resolvable-scale schemes affect the domain-averaged precipitation, the precipitation distribution, the sea level pressure, the cloud water and the cloud ice. Through a series of experiments about a warm sector rainfall case, results show that although the different resolvable-scale scheme is used, the differences of the precipitation characteristics among all five runs are not very obvious. However, the precipitation is over-predicted and the strong mesoscale low is produced by the simple super-saturation removal scheme. The warm rain scheme with the inclusion of condensation and evaporation under-predicts the precipitation and allows the cloud water to reach the 300 hPa level. The scheme of the addition of graupel increases the resolvable-scale precipitation by about 20%-30%. The inclusion of supercooled liquid water in the grid-scale scheme does not affect significantly the results. Key words Mesoscale model - Precipitation - Resolvable-scale microphysical parameterization
基金National Natural Science Foundation of China(42230612,41905071,41620104009)。
文摘A heavy rainfall event in south China was simulated by the Weather Research and Forecasting(WRF) model with three microphysics schemes, including the Morrison scheme, Thompson scheme, and Milbrandt and Yau scheme(MY), which aim to evaluate the capability to reproduce the precipitation and radar echo reflectivity features, and to evaluate evaluate their differences in microphysics and the associated thermodynamical and dynamical feedback. Results show that all simulations reproduce the main features crucial for rainfall formation. Compared with the observation, the MY scheme performed better than the other two schemes in terms of intensity and spatial distribution of rainfall. Due to abundant water vapor, the accretion of cloud droplets by raindrops was the dominant process in the growth of raindrops while the contribution of melting was a secondary effect. Riming processes, in which frozen hydrometeors collect cloud droplets mainly, contributed more to the growth of frozen hydrometeors than the Bergeron process. Extremely abundant snow and ice were produced in the Thompson and MY schemes respectively by a deposition process. The MY scheme has the highest condensation and evaporation, but the lowest deposition. As a result, in the MY scheme, the enhanced vertical gradient of condensation heating and evaporation cooling at low levels produces strong positive and weak negative potential vorticity in Guangdong, and may favor the formation of the enhanced rainfall center over there.
基金supported by the National Natural Science Foundations of China(Grant Nos.42305163 and U22A20577)the Construction Project of Weather Modification Ability in Central China(Grant No.ZQC-H22256)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0760300)the Projects of the Earth System Numerical Simulation Facility(Grant Nos.2024-EL-PT-000707,2023-ELPT-000482,2023-EL-ZD-00026,and 2022-EL-PT-00083)the STS Program of the Inner Mongolia Meteorological Service,Chongqing Institute of Green and Intelligent Technology,Chinese Academy of Sciences,and Institute of Atmospheric Physics,Chinese Academy of Sciences(Grant No.2021CG0047)。
文摘Accurate descriptions of cloud droplet spectra from aerosol activation to vapor condensation using microphysical parameterization schemes are crucial for numerical simulations of precipitation and climate change in weather forecasting and climate prediction models.Hence,the latest activation and triple-moment condensation schemes were combined to simulate and analyze the evolution characteristics of a cloud droplet spectrum from activation to condensation and compared with a high-resolution Lagrangian bin model and the current double-moment condensation schemes,in which the spectral shape parameter is fixed or diagnosed by an empirical formula.The results demonstrate that the latest schemes effectively capture the evolution characteristics of the cloud droplet spectrum during activation and condensation,which is in line with the performance of the bin model.The simulation of the latest activation and condensation schemes in a parcel model shows that the cloud droplet spectrum gradually widens and exhibits a multimodal distribution during the activation process,accompanied by a decrease in the spectral shape and slope parameters over time.Conversely,during the condensation process,the cloud droplet spectrum gradually narrows,resulting in increases in the spectral shape and slope parameters.However,these double-moment schemes fail to accurately replicate the evolution of the cloud droplet spectrum and its multimodal distribution characteristics.Furthermore,the latest schemes were coupled into a 1.5D cumulus model,and an observation case was simulated.The simulations confirm that the cloud droplet spectrum appears wider at the supersaturated cloud base and cloud top due to activation,while it becomes narrower at the middle altitudes of the cloud due to condensation growth.
基金Supported by China Meteorological Administration Special Public Welfare Research Fund(GYHY201206038,GYHY200906053,and GYHY201306040)National(Key)Basic Research and Development(973)Program of China(2013CB430102)+8 种基金National High Technology Research and Development Program(863)of China(2007AA061901)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(10KJA170030)State Key Laboratory Program(2013LASW-B16)Nanjing Weather Radar Open Laboratory Research Fund(BJG201208)Key Technology Projects of China Meteorological Bureau(CMAGJ2014M21)Young Scientists Fund of the Natural Science Foundation of Jiangsu Province(BK2012466)Postgraduate Science and Technology Innovation Project of Jiangsu Province(CXZZ13-0513)Non-Profit Industry Fund by Ministry of Science and Technology of China and Ministry of Water Resources(201201063)Young Scientists Fund of the National Natural Science Foundation of China(41305031)
文摘By using the cloud echoes fi rst successfully observed by China’s indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. （1） The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. （2） The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar refl ectivity factor is larger （over-10 dBZ）. （3） The radar’s sensitivity is comparatively higher because the minimum radar refl ectivity factor is about-35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio （LDR） of stratocumulus （commonly -11 to -14 dBZ; decreases with increasing turbulence）. （4） After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle eff ective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar refl ectivity factor.
基金Acknowledgments. Thanks to Dr. Alexander MacDonald of NOAA/FSL for his support throughout this study, and to Professors William Cotton. Roger Pielke. Wayne Schubert of Colorado State University, and to Dr. Fanyou Kong of University of Oklahoma and Mr. Hu
文摘A set of microphysics equations is scaled based on the convective length and velocity scales. Comparisons are made among the dynamical transport and various microphysical processes. From the scaling analysis, it becomes apparent which parameterized microphysical processes present off-scaled influences in the integration of the set of microphysics equations. The variabilities of the parameterized microphysical processes are also studied using the approach of a controlled parameter space. Given macroscopic dynamic and thermodynamic conditions in different regions of convective storms, it is possible to analyze and compare vertical profiles of these processes. Bulk diabatic heating profiles for a cumulus convective updraft and downdraft are also derived from this analysis. From the two different angles, the scale analysis and the controlled-parameter space approach can both provide an insight into and an understanding of microphysics parameterizations.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41275147 and 41875173)the STS Program of Inner Mongolia Meteorological Service, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences and Institute of Atmospheric Physics, Chinese Academy of Sciences (Grant No. 2021CG0047)
文摘The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parameter in the commonly used bulk double-moment schemes, the cloud droplet spectra cannot reasonably be described during the condensation process. Therefore, a newly-developed triple-parameter condensation scheme with the shape parameter diagnosed through the number concentration, cloud water content, and reflectivity factor of cloud droplets can be applied to improve the evolution of the cloud droplet spectrum. The simulation with the new parameterization scheme was compared to those with a high-resolution Lagrangian bin scheme, the double-moment schemes in a parcel model, and the observation in a 1.5D Eulerian model that consists of two cylinders. The new scheme with the shape parameter varying with time and space can accurately simulate the evolution of the cloud droplet spectrum. Furthermore, the volume-mean radius and cloud water content simulated with the new scheme match the Lagrangian analytical solutions well, and the errors are steady, within approximately 0.2%.
基金This research was primarily supported by a NOAA Warn-on-Forecast(WoF)grant(Grant No.NA16OAR4320115).
文摘There are more uncertainties with ice hydrometeor representations and related processes than liquid hydrometeors within microphysics parameterization(MP)schemes because of their complicated geometries and physical properties.Idealized supercell simulations are produced using the WRF model coupled with“full”Hebrew University spectral bin MP(HU-SBM),and NSSL and Thompson bulk MP(BMP)schemes.HU-SBM downdrafts are typically weaker than those of the NSSL and Thompson simulations,accompanied by less rain evaporation.HU-SBM produces more cloud ice(plates),graupel,and hail than the BMPs,yet precipitates less at the surface.The limiting mass bins(and subsequently,particle size)of rimed ice in HU-SBM and slower rimed ice fall speeds lead to smaller melting-level net rimed ice fluxes than those of the BMPs.Aggregation from plates in HU-SBM,together with snow–graupel collisions,leads to a greater snow contribution to rain than those of the BMPs.Replacing HU-SBM’s fall speeds using the formulations of the BMPs after aggregating the discrete bin values to mass mixing ratios and total number concentrations increases net rain and rimed ice fluxes.Still,they are smaller in magnitude than bulk rain,NSSL hail,and Thompson graupel net fluxes near the surface.Conversely,the melting-layer net rimed ice fluxes are reduced when the fall speeds for the NSSL and Thompson simulations are calculated using HU-SBM fall speed formulations after discretizing the bulk particle size distributions(PSDs)into spectral bins.The results highlight precipitation sensitivity to storm dynamics,fall speed,hydrometeor evolution governed by process rates,and MP PSD design.
基金National Natural Science Foundation of China(42130605,72293604)Guangdong Basic and Applied Basic Research Foundation(2019B1515120018,2019A1515111009)+2 种基金Shenzhen Natural Science Foundation(JCYJ20210324131810029)Guangdong Provincial College Innovation Team Project(2019KCXTF021)First-Class Discipline Plan of Guangdong Province(080503032101,231420003)。
文摘Typhoons,characterized by their high destructive potential,significantly impact coastal residents’lives and property safety.To optimize numerical models’typhoon simulation,carefully selecting appropriate physical para-meterization schemes is crucial,offering robust support for disaster prevention and reduction efforts.This study focuses on Typhoon Mujigae,conducting a comparative analysis of different physical parameterization schemes(microphysics,cu-mulus parameterization,shortwave radiation,and longwave radiation)in WRF simulations.The key findings are as follows:cumulus and microphysics parameterization schemes notably influence the simulation of typhoon tracks and intensity,while the impact of longwave and shortwave radiation schemes is relatively minor.Typhoon intensity is more sensitive to the choice of parameterization schemes than track.Together,the Kain-Fritsch cumulus convection scheme,WRF Single Moment 5-class scheme,and Dudhia/RRTM radiation scheme yield the best intensity simulation results.Compared with the Betts-Miller-Janjićand Grell 3D scheme,the use of the Kain-Fritsch scheme results in a clearer,taller eyewall and more symmetric deep convection,enhancing precipitation and latent heat release,and consequently improving the simulated typhoon intensity.More complex microphysics schemes like Purdue Lin,WRF Single Moment 5-class,and WRF Double Moment 6-class perform better in simulations,while simpler schemes like Kessler and WSM3 exhibit significant deviations in typhoon simulations.Particularly,the large amount of supercooled water clouds simulated by the Kessler scheme is a major source of bias.Furthermore,a coupling effect exists between cumulus convection and mi-crophysics parameterization schemes,and only a reasonable combination of both can achieve optimal simulation results.
基金Supported by the National Natural Science Foundation of China(41405006)China Meteorological Administration Special Public Welfare Research Fund(GYHY201006014 and GYHY201306005)+1 种基金National(Key)Basic Research and Development(973)Program of China(2012CB417204)Basic Research Fund of the Chinese Academy of Meteorological Sciences(2014R016 and2014Z001)
文摘Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes（also called autoconversion） are proposed based on a large number of Cloud Sat observations between June2006 and April 2011 over Asian land areas. The emphasis is given to the vertical distribution of liquid water content（LWC）, particularly, the threshold values of LWC for autoconversion. The results warrant a new approach to the numerical parameterization of autoconversion in warm clouds. One feature of this new approach is that the autoconversion threshold, which has been treated as a constant in previous parameterization schemes, is diagnosed as a function of altitude by using a relationship between LWC and height（H）derived from Cloud Sat observations： LWCdig =-500.0 ln（ H/9492.2）. Under this framework, the threshold LWC decreases with increasing H, allowing autoconversion to occur in clouds with low LWC（approximately0.3 g m^-3） at levels above 5.5 km. Autoconversion rates calculated based on the new parameterization are compared to those calculated based on several commonly used parameterization schemes over a range of LWCs from 0.01 to 1.0 g m^-3. The new scheme provides reasonable simulations of autoconversion at various vertical levels.
基金The authors benefited from discussions with Professors C.-H.Sui and Xu Huanbin.The comments of the three anonymous reviewers are acknowledged.This research was supported by the National Natural Science Foundation of China.(Grant Nos.40375036 and 40105006).
文摘The understanding of the cloud processes of snowfall is essential to the artificial enhancement of snow and the numerical simulation of snowfall. The mesoscale model MM5 is used to simulate a moderate snowfall event in North China that occurred during 20-21 December 2002. Thirteen experiments are performed to test the sensitivity of the simulation to the cloud physics with different cumulus parameterization schemes and different options for the Goddard cloud microphysics parameterization schemes. It is shown that the cumulus parameterization scheme has little to do with the simulation result. The results also show that there are only four classes of water substances, namely the cloud water, cloud ice, snow, and vapor, in the simulation of the moderate snowfall event. The analysis of the cloud microphysics budgets in the explicit experiment shows that the condensation of supersaturated vapor, the depositional growth of cloud ice, the initiation of cloud ice, the accretion of cloud ice by snow, the accretion of cloud water by snow, the deposition growth of snow, and the Bergeron process of cloud ice are the dominant cloud microphysical processes in the simulation. The accretion of cloud water by snow and the deposition growth of the snow are equally important in the development of the snow.
基金National Natural Science Foundation (40675005)Science Foundation (QD52)Natural Science Foundation for High Education in Jiangsu Province (06KJB170047)
文摘The Weather Research Forecast model (WRF) configured with high resolution and NCEP 1°×1° reanalysis data were used to simulate the development of a tropical deep convection over the Tiwi Islands,northern Australia,and to investigate the sensitivity of model results to model configuration and parameterization schemes of microphysical processes.The simulation results were compared with available measurements.The results show that the model can reproduce most of the important characteristics of the observed diurnal evolution of the convection,including the initiation of convection along the sea-breeze front,which is then reinforced by downdraft outflows,merging of cells and the formation of a deep convective system.However,further improvement is needed to simulate more accurately the location and the time for initiation of the deep convective system.Sensitivity tests show that double-nesting schemes are more accurate than the non-nesting schemes in predicting the distribution and intensity of precipitation as far as this particular case is concerned.Additionally,microphysical schemes also have an effect on the simulated amount of precipitation.It is shown that the best agreement is reached between the simulation results and observations when the Purdue Lin scheme is used.
基金Supported by the National Natural Science Foundation of China(41075023)China Meteorological Administration Special Public Welfare Research Fund(GYHY200906039 and GYHY201206042)State Key Laboratory of Severe Weather ResearchFund
文摘This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retrieval of raindrop size distributions（RSDs） is accomplished through eliminating vertical air motion and isolating the terminal fall velocity of raindrops in the observed Doppler velocity spectrum.The microphysical properties of raindrops in a broad stratiform region with weak convective cells are studied using data collected from a 1320-MHz wind profiler radar in Huayin,Shaanxi Province on 14 May 2009.RSDs and gamma function parameters are retrieved at altitudes between 700 and 3000 m above the surface,below a melting layer.It is found that the altitude of the maximum number of raindrops was closely related to the surface rain rate.The maximum number of large drops was observed at lower altitudes earlier in the precipitation event but at higher altitudes in later periods,suggesting decreases in the numbers of large and medium size raindrops.These decreases may have been caused by the breakup of larger drops and evaporation of smaller drops as they fell.The number of medium size drops decreased with increasing altitude.The relationship between reflectivity and liquid water content during this precipitation event was Z = 1.69×10~4M^（1.5）,and the relationship between reflectivity and rain intensity was Z = 256I^（1.4）.
基金Supported by the China Meteorological Administration Special Public Welfare Research Fund(GYHY201006014 and GYHY201306005)National Natural Science Foundation of China(91437221,41175064,and 41175047)+1 种基金National(Key)Basic Research and Development(973)Program of China(2012CB417204)Basic Research Fund of the Chinese Academy of Meteorological Sciences(2014R016 and 2014Z001)
文摘A large number of in-situ measurements of cloud-precipitation microphysical properties have been made since 1960, including measurements of particle size distribution, particle concentration, and liquid water content of clouds and rain. These measurements have contributed to considerable progress in understanding microphysical processes in clouds and precipitation and significant improvements in parameterizations of cloud microphysics in numerical models. This work reviews key findings regarding cloud-precipitation microphysics over China. The total number concentrations of various particles vary significantly, with certain characteristic spatial scales. The size distributions of cloud droplets in stratiform clouds can generally be fit with gamma distributions, but the fit parameters cover a wide range. Raindrop size distributions（RSDs）associated with stratiform clouds can be fit with either exponential or gamma distributions, while RSDs associated with convective or mixed stratiform-cumuliform clouds are best fit with gamma distributions.Concentrations of ice nuclei（IN） over China are higher than those observed over other regions, and increase exponentially as temperature decreases. The particle size distributions of ice crystals, snow crystals, and hailstones sampled at a variety of locations can be reliably approximated by using exponential distributions,while aerosol particle size distributions are best described as the sum of a modified gamma distribution and a Junge power-law distribution. These results are helpful for evaluating and improving the fidelity of physical processes and hydrometeor fields simulated by microphysical parameterizations. The comprehensive summary and analysis of previous work presented here also provide useful guidelines for the design of future observational programs.
文摘In order to study mechanisms of hailstone formation and hail suppression with seeding and to obtain optimum seeding technique for hail cloud,a 3-D compressive numerical seeding model for hail cloud is developed.The water substance in hail cloud is divided into 8 categories,i.e.,water vapor,cloud droplet,raindrop,ice crystal,snow.graupel,frozen drop and hail,and the detailed microphysical processes are described in a spectrum with two variable parameters and more reasonable particle number/size distributions.Then,the model is able to predict concentration and water content of various particles.Especially.it can calculate the number of hailstones whose cores are graupel or frozen drop and apply to study mechanism of hailstone formation. Additionally,a conservative equation of AgI as seeding or glacigenous agent is found and nucleation by condensation of artificial nucleus,and nucleation by freezing of cloud droplet or rain drop which contact with AgI particle are considered.The dynamic energy flux of hail shooting on ground is used to verify seeding effect.Therefore the model is also used to study mechanism of hail suppression with seeding and the seeding technique,
