In mid-April 2025,northern and central-eastern China experienced a catastrophic compound disaster marked by Beaufort 8 or greater wind gusts affecting∼3.5×10^(6)km^(2),exposing∼610 million residents to extreme ...In mid-April 2025,northern and central-eastern China experienced a catastrophic compound disaster marked by Beaufort 8 or greater wind gusts affecting∼3.5×10^(6)km^(2),exposing∼610 million residents to extreme conditions,with Typhoon-equivalent Beaufort 12 gusts battering Beijing’s Yanshan Mountains and Beaufort 14-15 winds devastating Inner Mongolia.This unprecedented event surpassed historical extremes at 64 weather stations,impacting 996 monitoring sites with winds exceeding the 99th percentile,including 478 stations recording historic top-three maxima.Concurrently,sandstorms engulfed∼4.3×10^(6)km^(2),reaching 18°N,while Hulunbuir faced a 1.5-m snowpack-a 30-year April record.Cascading infrastructure failures resulted in 1884 uprooted trees,approximately¥16.6 million in urban damages(in Beijing),and the collapse of utility-scale photovoltaic systems across northern China and the Huang-Huai region,exacerbating the multi-faceted crisis.A brief analysis indicates the event was primarily driven by a vertically coupled cyclone system featuring a cold vortex at the middle and upper troposphere dynamically aligned with a lower-level cyclone/mesoscale vortex.The intense,deeply coupled cyclone system sustained the wind intensification primarily through its enhanced pressure gradient force and subsidence-induced downward transport of kinetic energy(KE)behind the cyclone’s core.Clarifying the controlling synoptic-scale weather systems and dominant physical mechanisms governing such extreme wind generation is critical for refining predictive models of these high-impact events while advancing the understanding of dynamic interactions within extreme wind regimes.展开更多
A thunderstorm that produced severe wind, heavy rain and hail on 23 August 2001 in Beijing was studied by a three-dimensional cloud model including hail-bin microphysics. This model can provide important information f...A thunderstorm that produced severe wind, heavy rain and hail on 23 August 2001 in Beijing was studied by a three-dimensional cloud model including hail-bin microphysics. This model can provide important information for hail size at the surface, which is not available in hail parameterization cloud models. The results shows that the cloud model, using hail-bin microphysics, could reasonably reflect the storm＇s characteristics such as life cycle, rainfall distribution and the diameter of the hailstones and also can reproduce developing processes of downbursts, where they can then be compared with the observed features of the storm. The downburst formation mechanism was investigated based on the cloud microphysics of the simulated storm and it was found that the downburst was primarily produced by hail-loading and enhanced by cooling processes that were due to hail melting and rain evaporation. The loading and melting of hail played crucial roles in the formation of downbursts within the storm.展开更多
The characteristics of cloud-to-ground(CG) lightning activity with severe thunderstorm wind(STW) in South and North China are analyzed using CG lightning data, radar data, and serious weather reports. The percentage o...The characteristics of cloud-to-ground(CG) lightning activity with severe thunderstorm wind(STW) in South and North China are analyzed using CG lightning data, radar data, and serious weather reports. The percentage of positive CG(PCG) flashes with STW in North China is larger than that in South China. STW takes place during the period when the total CG and PCG density is increasing fastest. STW also occurs close to the high-value center of CG and PCG density. In North China, the CG and PCG density in the grid of STW maximizes approximately 20 minutes after the STW occurs; while in South China, the PCG density and percentage of PCG in the grid of STW maximizes about 10 minutes before the occurrence of STW. The high-value centers of CG density and PCG density in North China move slightly faster than those in South China, which is opposite to the rate of increasing CG activity.展开更多
The 3-D radar reflectivity data has become increasingly important for use in data assimilation towards convective scale numerical weather prediction as well as next generation precipitation estimation. Typically, refl...The 3-D radar reflectivity data has become increasingly important for use in data assimilation towards convective scale numerical weather prediction as well as next generation precipitation estimation. Typically, reflectivity data from multiple radars are objectively analyzed and mosaiced onto a regional 3-D Cartesian grid prior to being assimilated into the models. One multi-radar observations is the synchronization of all of the scientific issues associated with the mosaic of the observations. Since radar data is usually rapidly updated （-every 5-10 min）, it is common in current multi-radar mosaic techniques to combine multiple radar＇ observations within a time window by assunfing that the storms are steady within the window. The assumption holds well for slow evolving precipitation systems, but for fast evolving convective storms, this assumption may be violated and the mosaic of radar observations at different times may result in inaccurate storm structure depictions. This study investigates the impact of synchronization on storm structures in multiple radar data analyses using a multi-scale storm tracking algorithm.展开更多
The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data.The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25-2...The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data.The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25-28 January 2008 showed the advection of the geopotential by the ageostrophic wind to be both a crucial source and the primary sink of the eddy kinetic energy centers associated with the troughs.The magnitudes of the energy conversion terms,interaction kinetic energy conversion and baroclinic conversion,were too small to explain the development of the energy centers and the jet streaks.The energy centers gained energy at their entrance regions via the convergence of the ageostrophic geopotential fluxes,and then lost energy at their exit regions by the same fluxes.At the entrance regions,the fluxes converged,increasing the geopotential gradient,which generated a stronger geostrophic wind and higher kinetic energy,resulting in an ascending motion in this area.When the troughs moved to China,the ascending motion caused by the convergence of the fluxes at entrance region intensified the snowstorms over central and southern China.展开更多
Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetos...Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetosphere,and ionosphere,field-aligned currents(FACs)can also be strengthened in storm times.This study shows the responses of FACs in the plasma sheet boundary layer(PSBL)observed by the Magnetospheric Multiscale(MMS)spacecraft in different phases of a large storm that lasted from May 27,2017,to May 29,2017.Most of the FACs were carried by electrons,and several FACs in the storm time also contained sufficient ion FACs.The FAC magnitudes were larger in the storm than in the quiet period,and those in the main phase were the strongest.In this case,the direction of the FACs in the main phase showed no preference for tailward or earthward,whereas the direction of the FACs in the recovery phase was mostly tailward.The results suggest that the FACs in the PSBL are closely related to the storm and could be driven by activities in the tail region,where the energy transported from the solar wind to the magnetosphere is stored and released as the storm is evolving.Thus,the FACs are an important medium of energy transport between the tail and the ionosphere,and the PSBL is a significant magnetosphere–ionosphere coupling region in the nightside.展开更多
In this paper, the characteristics of eastern Asian dust storm are examined with emphasis on the satellite measurements of aerosol optical thickness. The reflectivity of solar radiation from the earth's atmosphere...In this paper, the characteristics of eastern Asian dust storm are examined with emphasis on the satellite measurements of aerosol optical thickness. The reflectivity of solar radiation from the earth's atmosphere depends on the optical thickness. The satellite measurement of radiance of sunlight, scattered by the earth and its atmosphere, is used to derive the properties of aerosol on oceanic surfaces. This paper involves the following: (1) investigation of the measurement of dust storm over the oceanic surface by GMS satellite; (2) investigation of the measurement of dust storm over the land surface by ground-based instruments such as actinometer, lidar, etc.; (3) for comparison, deriving an atmospheric aerosol size distribution over the oceanic surface of calm weather through measurements of NOAA satellite; and (4) the weather process and its mass load of eastern Asian dust storm.展开更多
A severe storm that occurred over Beijing in northern China on 23 June 2011 was simulated with two different ice crystal parameterization schemes(the DeMott scheme and Meyers scheme) by using the Regional Atmospheric ...A severe storm that occurred over Beijing in northern China on 23 June 2011 was simulated with two different ice crystal parameterization schemes(the DeMott scheme and Meyers scheme) by using the Regional Atmospheric Modeling System. Compared with the DeMott scheme, the simulation results with the Meyers scheme have the following characteristics:(1) Updrafts are stronger and more numerous;(2) The cloud is better organized and contains a greater peak of ice-phase hydrometeor mixing ratios;(3) Cloud water and hail mixing ratios increase while graupel mixing ratios decrease;(4) The surface precipitation is initially greater. However, at the end of the simulation, less precipitation is produced. In short, the differences between the two schemes are not obvious, but the De Mott scheme has a relatively more reasonable result.展开更多
Forecasting convective storms using NWP models is an important goal and a highly active area of ongoing research. Skillful and reliable NWP of convective storms could allow for severe weather warnings with longer lead...Forecasting convective storms using NWP models is an important goal and a highly active area of ongoing research. Skillful and reliable NWP of convective storms could allow for severe weather warnings with longer lead times, as opera- tional forecasters begin to incorporate convective-scale fore- casts into severe weather forecast operations （Stensrud et al., 2009, 2013）. This would then provide vulnerable individuals and industries with more time to seek shelter and/or mitigate the impact of severe weather hazards.展开更多
How to obtain fast-growth errors, which is comparable to the actual forecast growth error, is a crucial problem in ensemble forecast （EF）. The method, Breeding of Growth Modes （BGM）, which has been used to generat...How to obtain fast-growth errors, which is comparable to the actual forecast growth error, is a crucial problem in ensemble forecast （EF）. The method, Breeding of Growth Modes （BGM）, which has been used to generate perturbations for medium-range EF at NCEP, simulates the development of fast-growth errors in the analysis cycle, and is a reasonable choice in capturing growing errors modes, especially for extreme weather by BGM. An ideal supercell storm, simulated by Weather Research Forecast model （WRF）, occurred in central Oklahoma on 20 May 1977. This simulation was used to study the application of BGM methods in the meso-scale strong convective Ensemble Prediction System （EPS）. We compared the forecasting skills of EPS by different pertubation methods, like Monte-Carlo and BGM. The results show that the ensemble average forecast based on Monte-Carlo with statistics meaning is superior to the single-deterministic prediction, but a less dynamic process of the method leads to a smaller spread than expected. The fast-growth errors of BGM are comparable to the actual short-range forecast error and a more appropriate ensemble spread. Considering evaluation indexes and scores, the forecast skills of EPS by BGM is higher than Monte-Carlo＇s. Furthermore, various breeding cycles have different effects on precipitation and non-precipitation fields, confirmation of reasonable cycles need consider balance between variables.展开更多
The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weat...The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weather radar data and numerical simulations from a high-resolution convection-allowing model.The deep convection towers occurred prior to the emergence of SWV and throughout its onset and development stages.They largely resemble the vortical hot tower(VHT)commonly seen in typhoons or hurricanes and are thus considered as a special type of VHT(sVHT).Each sVHT presented a vorticity dipole structure,with the upward motion not superpose the positive vorticity.A positive feedback process in the SWV helped the organization of sVHTs,which in turn strengthened the initial disturbance and development of SWV.The meso-γ-scale large-value areas of positive relative vorticity in the mid-toupper troposphere were largely induced by the diabatic heating and tilting.The strong mid-level convergence was attributed to the mid-level vortex enhancement.The low-level vortex intensification was mainly due to low-level convergence and the stretching of upward flow.The meso-α-scale large-value areas of positive relative vorticity in the low-level could expand up to about 400 hPa,and gradually weakened with time and height due to the decaying low-level convergence and vertical stretching in the matured SWV.As the SWV matured,two secondary circulations were formed,with a weaker mean radial inflow than the outflow and elevated to 300-400 hPa.展开更多
The traditional threat score based on fixed thresholds for precipitation verification is sensitive to intensity forecast bias. In this study, the neighborhood precipitation threat score is modified by defining the thr...The traditional threat score based on fixed thresholds for precipitation verification is sensitive to intensity forecast bias. In this study, the neighborhood precipitation threat score is modified by defining the thresholds in terms of the percentiles of overall precipitation instead of fixed threshold values. The impact of intensity forecast bias on the calculated threat score is reduced. The method is tested with the forecasts of a tropical storm that re-intensified after making landfall and caused heavy flooding. The forecasts are produced with and without radar data assimilation. The forecast with assimilation of both radial velocity and reflectivity produce precipitation patterns that better match observations but have large positive intensity bias. When using fixed thresholds, the neighborhood threat scores fail to yield high scores for forecasts that have good pattern match with observations, due to large intensity bias. In contrast, the percentile-based neighborhood method yields the highest score for the forecast with the best pattern match and the smallest position error. The percentile-based method also yields scores that are more consistent with object-based verifications, which are less sensitive to intensity bias, demonstrating the potential value of percentile-based verification.展开更多
In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature an...In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature and precipitation during the severe snowstorm that occurred in southern China during 0800 26 January to 0800 29 January 2008 （Note that all times are local time except when otherwise stated）. Black carbon aerosol was simulated online within the WRF-Chem. The model resuits showed that surface-albedo, averaged over 27-28 January, can be reduced by up to 10% by the deposition of BC. As a result, relative to a simulation that does not consider deposition of BC on snow/ice, the authors predicted surface air temperatures during 27-28 January can differ by -1.95 to 2.70 K, and the authors predicted accumulated precipitation over 27-28 January can differ by -2.91 to 3.10 mm over Areas A and B with large BC deposition. Different signs of changes are determined by the feedback of clouds and by the availability of water vapor in the atmosphere.展开更多
Capabilities to assimilate Geostationary Operational Environmental Satellite “R-series ”(GOES-R) Geostationary Lightning Mapper(GLM) flash extent density(FED) data within the operational Gridpoint Statistical Interp...Capabilities to assimilate Geostationary Operational Environmental Satellite “R-series ”(GOES-R) Geostationary Lightning Mapper(GLM) flash extent density(FED) data within the operational Gridpoint Statistical Interpolation ensemble Kalman filter(GSI-EnKF) framework were previously developed and tested with a mesoscale convective system(MCS) case. In this study, such capabilities are further developed to assimilate GOES GLM FED data within the GSI ensemble-variational(EnVar) hybrid data assimilation(DA) framework. The results of assimilating the GLM FED data using 3DVar, and pure En3DVar(PEn3DVar, using 100% ensemble covariance and no static covariance) are compared with those of EnKF/DfEnKF for a supercell storm case. The focus of this study is to validate the correctness and evaluate the performance of the new implementation rather than comparing the performance of FED DA among different DA schemes. Only the results of 3DVar and pEn3DVar are examined and compared with EnKF/DfEnKF. Assimilation of a single FED observation shows that the magnitude and horizontal extent of the analysis increments from PEn3DVar are generally larger than from EnKF, which is mainly caused by using different localization strategies in EnFK/DfEnKF and PEn3DVar as well as the integration limits of the graupel mass in the observation operator. Overall, the forecast performance of PEn3DVar is comparable to EnKF/DfEnKF, suggesting correct implementation.展开更多
Numerical simulations are carried out to investigate the effect of cloud condensation nuclei（CCN） concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are si...Numerical simulations are carried out to investigate the effect of cloud condensation nuclei（CCN） concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are simulated, a spring case and a summer case, in a semiarid region of northern China, with the Regional Atmospheric Modeling System. The results are used to investigate the differences and similarities of the CCN effects between spring and summer hailstorms. The similarities are：（1） The total hydrometeor mixing ratio decreases, while the total ice-phase mixing ratio enhances, with increasing CCN concentration;（2） Enhancement of the CCN concentration results in the production of a greater amount of small-sized hydrometeor particles, but a lessening of large-sized hydrometeor particles;（3） As the CCN concentration increases, the supercooled cloud water and rainwater make a lesser contribution to hail, while the ice-phase hydrometeors take on active roles in the growth of hail;（4） When the CCN concentration increases, the amount of total precipitation lessens,while the role played by liquid-phase rainfall in the amount of total precipitation reduces, relatively, compared to that of icephase precipitation. The differences between the two storms include：（1） An increase in the CCN concentration tends to reduce pristine ice mixing ratios in the spring case but enhance them in the summer case;（2） Ice-phase hydrometeor particles contribute more to hail growth in the spring case, while liquid water contributes more in the summer case;（3） An increase in the CCN concentration has different effects on surface hail precipitation in different seasons.展开更多
The Regional Atmospheric Modeling System (RAMS) has been used to investigate the effects of varied giant cloud condensation nuclei (GCCN) concentrations on precipitation characteristics of the spring hailstorms in a s...The Regional Atmospheric Modeling System (RAMS) has been used to investigate the effects of varied giant cloud condensation nuclei (GCCN) concentrations on precipitation characteristics of the spring hailstorms in a semi-arid region. The simulation result shows that this variation has significant effects on the storm microphysical processes as well as on the surface precipitation. The coverage of hail and hail mixing ratio maxima in cloud increases with greater GCCN concentrations. The accumulation zone structure benefits the growth of hail particles. Higher GCCN concentrations lead to more supercooled rain water and cloud water available for freezing. This simulation also shows that increasing GCCN concentrations may produce more rainfall on the surface but less hail precipitation, and the total accumulated precipitation increases while the ice phase precipitation decreases. This effect is stronger in polluted air than in clean air. The surface flow field changes with different GCCN concentrations. The identification index of spring hailstorm is different from that of summer hailstorm with a different aerosol background.展开更多
The transports of dust are calculated using 3-dimensional(3-D)trajectory method for three cases of duststorms in the terrain-following coordinate system,and the synoptic processes are also discussed for each case.The ...The transports of dust are calculated using 3-dimensional(3-D)trajectory method for three cases of duststorms in the terrain-following coordinate system,and the synoptic processes are also discussed for each case.The case of 17—20 April 1980,a severe duststorm was associated with the rapid development of a cyclone over the Mongolia Plateau.The dust moved from west to east across several deserts,formed a typical dust path in spring.The other two were weaker and the dust was triggered by the strong wind behind the cold front from northwest or north.Because the vertical velocity is considered in 3-D trajectory analysis,trajectories calculated should better reveal the transport rule of the dust particles and the results seem to be more consistent with the synoptic processes.The trajectory analysis on the 2-D isobaric sur- faces is simpler but can be used only in the conditions with weak vertical wind shear and weak vertical velocity.The dif- ference of trajectories at lower levels between two methods may be caused by the different treatment of orography.展开更多
The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan regio...The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model.展开更多
基金supported by the National Natural Science Foundation of China[grant number 42475008]the Strategy Priority Research Program of the Chinese Academy of Sciences[grant number XDB0760400].
文摘In mid-April 2025,northern and central-eastern China experienced a catastrophic compound disaster marked by Beaufort 8 or greater wind gusts affecting∼3.5×10^(6)km^(2),exposing∼610 million residents to extreme conditions,with Typhoon-equivalent Beaufort 12 gusts battering Beijing’s Yanshan Mountains and Beaufort 14-15 winds devastating Inner Mongolia.This unprecedented event surpassed historical extremes at 64 weather stations,impacting 996 monitoring sites with winds exceeding the 99th percentile,including 478 stations recording historic top-three maxima.Concurrently,sandstorms engulfed∼4.3×10^(6)km^(2),reaching 18°N,while Hulunbuir faced a 1.5-m snowpack-a 30-year April record.Cascading infrastructure failures resulted in 1884 uprooted trees,approximately¥16.6 million in urban damages(in Beijing),and the collapse of utility-scale photovoltaic systems across northern China and the Huang-Huai region,exacerbating the multi-faceted crisis.A brief analysis indicates the event was primarily driven by a vertically coupled cyclone system featuring a cold vortex at the middle and upper troposphere dynamically aligned with a lower-level cyclone/mesoscale vortex.The intense,deeply coupled cyclone system sustained the wind intensification primarily through its enhanced pressure gradient force and subsidence-induced downward transport of kinetic energy(KE)behind the cyclone’s core.Clarifying the controlling synoptic-scale weather systems and dominant physical mechanisms governing such extreme wind generation is critical for refining predictive models of these high-impact events while advancing the understanding of dynamic interactions within extreme wind regimes.
基金This research was jointly sponsored by the National Natural Science Foundation of China （Grant Nos. 40575003 and 40333033） the Chinese Academy of Sciences Innovation Foundation （Grant No. KZCX3-SW-213 and KZCX3-SW-225）.
文摘A thunderstorm that produced severe wind, heavy rain and hail on 23 August 2001 in Beijing was studied by a three-dimensional cloud model including hail-bin microphysics. This model can provide important information for hail size at the surface, which is not available in hail parameterization cloud models. The results shows that the cloud model, using hail-bin microphysics, could reasonably reflect the storm＇s characteristics such as life cycle, rainfall distribution and the diameter of the hailstones and also can reproduce developing processes of downbursts, where they can then be compared with the observed features of the storm. The downburst formation mechanism was investigated based on the cloud microphysics of the simulated storm and it was found that the downburst was primarily produced by hail-loading and enhanced by cooling processes that were due to hail melting and rain evaporation. The loading and melting of hail played crucial roles in the formation of downbursts within the storm.
基金supported by the China Meteorological Administration (Grant No. GYHY201406002)the Key Program of the Chinese Academy of Sciences (Grant No. 2013CB430100)
文摘The characteristics of cloud-to-ground(CG) lightning activity with severe thunderstorm wind(STW) in South and North China are analyzed using CG lightning data, radar data, and serious weather reports. The percentage of positive CG(PCG) flashes with STW in North China is larger than that in South China. STW takes place during the period when the total CG and PCG density is increasing fastest. STW also occurs close to the high-value center of CG and PCG density. In North China, the CG and PCG density in the grid of STW maximizes approximately 20 minutes after the STW occurs; while in South China, the PCG density and percentage of PCG in the grid of STW maximizes about 10 minutes before the occurrence of STW. The high-value centers of CG density and PCG density in North China move slightly faster than those in South China, which is opposite to the rate of increasing CG activity.
基金Major funding for this research was provided under the United States Federal Aviation Administration (FAA) Aviation Weather Research Program Advanced Weather Radar Technologies Prod-uct Development Team Memorandum Of Understanding(MOU)partial funding was provided under NOAA-University of Oklahoma Cooperative Agreement Grant No. NA17RJ1227, U.S. Department of Commerce
文摘The 3-D radar reflectivity data has become increasingly important for use in data assimilation towards convective scale numerical weather prediction as well as next generation precipitation estimation. Typically, reflectivity data from multiple radars are objectively analyzed and mosaiced onto a regional 3-D Cartesian grid prior to being assimilated into the models. One multi-radar observations is the synchronization of all of the scientific issues associated with the mosaic of the observations. Since radar data is usually rapidly updated （-every 5-10 min）, it is common in current multi-radar mosaic techniques to combine multiple radar＇ observations within a time window by assunfing that the storms are steady within the window. The assumption holds well for slow evolving precipitation systems, but for fast evolving convective storms, this assumption may be violated and the mosaic of radar observations at different times may result in inaccurate storm structure depictions. This study investigates the impact of synchronization on storm structures in multiple radar data analyses using a multi-scale storm tracking algorithm.
基金supported by the National Basic Research Project of China (Grant Nos. 2013CB430105 and 2012CB417201)the National Natural Science Foundation of China (Grant No. 40930950)+1 种基金the Chinese Academy of Meteorological Sciences State Key Laboratory of Severe Weather (LaSW) (Grant No. 2011LASW-A01)the Key Research Program of the Sciences (Grant No. KZZDEW-05-01)
文摘The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data.The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25-28 January 2008 showed the advection of the geopotential by the ageostrophic wind to be both a crucial source and the primary sink of the eddy kinetic energy centers associated with the troughs.The magnitudes of the energy conversion terms,interaction kinetic energy conversion and baroclinic conversion,were too small to explain the development of the energy centers and the jet streaks.The energy centers gained energy at their entrance regions via the convergence of the ageostrophic geopotential fluxes,and then lost energy at their exit regions by the same fluxes.At the entrance regions,the fluxes converged,increasing the geopotential gradient,which generated a stronger geostrophic wind and higher kinetic energy,resulting in an ascending motion in this area.When the troughs moved to China,the ascending motion caused by the convergence of the fluxes at entrance region intensified the snowstorms over central and southern China.
基金funded by the National Natural Science Foundation of China(NSFCGrant Nos.42204177,42274219,41974205,42130204,42241155,and 42241133)+5 种基金the Guangdong Basic and Applied Basic Research Foundation-Natural Science Foundation of Guangdong(Grant Nos.2022A1515010257,2022A1515011698,and 2023A1515030132)the Shenzhen Science and Technology Research Program(Grant Nos.JCYJ20210324121403009 and JCYJ20210324121412034)the Macao foundation,the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2022041)the Shenzhen Key Laboratory Launching Project(Grant No.ZDSYS20210702140800001)the pre-research project on Civil Aerospace Technologies(Grant No.D020103)funded by the China National Space Administration.YuanQiang Chen was also funded by China Postdoctoral Science Foundation(Grant No.2022M720944)supported by the Chinese Academy of Sciences Center for Excellence in Comparative Planetology.
文摘Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetosphere,and ionosphere,field-aligned currents(FACs)can also be strengthened in storm times.This study shows the responses of FACs in the plasma sheet boundary layer(PSBL)observed by the Magnetospheric Multiscale(MMS)spacecraft in different phases of a large storm that lasted from May 27,2017,to May 29,2017.Most of the FACs were carried by electrons,and several FACs in the storm time also contained sufficient ion FACs.The FAC magnitudes were larger in the storm than in the quiet period,and those in the main phase were the strongest.In this case,the direction of the FACs in the main phase showed no preference for tailward or earthward,whereas the direction of the FACs in the recovery phase was mostly tailward.The results suggest that the FACs in the PSBL are closely related to the storm and could be driven by activities in the tail region,where the energy transported from the solar wind to the magnetosphere is stored and released as the storm is evolving.Thus,the FACs are an important medium of energy transport between the tail and the ionosphere,and the PSBL is a significant magnetosphere–ionosphere coupling region in the nightside.
文摘In this paper, the characteristics of eastern Asian dust storm are examined with emphasis on the satellite measurements of aerosol optical thickness. The reflectivity of solar radiation from the earth's atmosphere depends on the optical thickness. The satellite measurement of radiance of sunlight, scattered by the earth and its atmosphere, is used to derive the properties of aerosol on oceanic surfaces. This paper involves the following: (1) investigation of the measurement of dust storm over the oceanic surface by GMS satellite; (2) investigation of the measurement of dust storm over the land surface by ground-based instruments such as actinometer, lidar, etc.; (3) for comparison, deriving an atmospheric aerosol size distribution over the oceanic surface of calm weather through measurements of NOAA satellite; and (4) the weather process and its mass load of eastern Asian dust storm.
基金partially supported by the National Natural Science Foundation of China (Grant No. 41205099)the National Basic Research Program of China (973 Program, Grant Nos. 2014CB441403 and 2013CB430105)+1 种基金the Special Scientific Research Project of the Meteorological Public Welfare Profession of China (Grant No. GYHY201006031)the Guizhou Province Scientific Research Joint Project (Grant No. G[2013]4001)
文摘A severe storm that occurred over Beijing in northern China on 23 June 2011 was simulated with two different ice crystal parameterization schemes(the DeMott scheme and Meyers scheme) by using the Regional Atmospheric Modeling System. Compared with the DeMott scheme, the simulation results with the Meyers scheme have the following characteristics:(1) Updrafts are stronger and more numerous;(2) The cloud is better organized and contains a greater peak of ice-phase hydrometeor mixing ratios;(3) Cloud water and hail mixing ratios increase while graupel mixing ratios decrease;(4) The surface precipitation is initially greater. However, at the end of the simulation, less precipitation is produced. In short, the differences between the two schemes are not obvious, but the De Mott scheme has a relatively more reasonable result.
文摘Forecasting convective storms using NWP models is an important goal and a highly active area of ongoing research. Skillful and reliable NWP of convective storms could allow for severe weather warnings with longer lead times, as opera- tional forecasters begin to incorporate convective-scale fore- casts into severe weather forecast operations （Stensrud et al., 2009, 2013）. This would then provide vulnerable individuals and industries with more time to seek shelter and/or mitigate the impact of severe weather hazards.
基金supported jointly by the Nature Science Foundation of China (Project No:40875068)Public-Welfare Meteorological Research Foundation (ProjectNo:GYHY200806029)
文摘How to obtain fast-growth errors, which is comparable to the actual forecast growth error, is a crucial problem in ensemble forecast （EF）. The method, Breeding of Growth Modes （BGM）, which has been used to generate perturbations for medium-range EF at NCEP, simulates the development of fast-growth errors in the analysis cycle, and is a reasonable choice in capturing growing errors modes, especially for extreme weather by BGM. An ideal supercell storm, simulated by Weather Research Forecast model （WRF）, occurred in central Oklahoma on 20 May 1977. This simulation was used to study the application of BGM methods in the meso-scale strong convective Ensemble Prediction System （EPS）. We compared the forecasting skills of EPS by different pertubation methods, like Monte-Carlo and BGM. The results show that the ensemble average forecast based on Monte-Carlo with statistics meaning is superior to the single-deterministic prediction, but a less dynamic process of the method leads to a smaller spread than expected. The fast-growth errors of BGM are comparable to the actual short-range forecast error and a more appropriate ensemble spread. Considering evaluation indexes and scores, the forecast skills of EPS by BGM is higher than Monte-Carlo＇s. Furthermore, various breeding cycles have different effects on precipitation and non-precipitation fields, confirmation of reasonable cycles need consider balance between variables.
基金Operational Technology Research Team Project of Chongqing Meteorological Service(YWGGTD-201702)Technology Innovation and Application Development Key Project of Chongqing(cstc2019jscx-tjsb X0007)Natural Science Foundation of Chongqing(cstc2018jcyj AX0434)。
文摘The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weather radar data and numerical simulations from a high-resolution convection-allowing model.The deep convection towers occurred prior to the emergence of SWV and throughout its onset and development stages.They largely resemble the vortical hot tower(VHT)commonly seen in typhoons or hurricanes and are thus considered as a special type of VHT(sVHT).Each sVHT presented a vorticity dipole structure,with the upward motion not superpose the positive vorticity.A positive feedback process in the SWV helped the organization of sVHTs,which in turn strengthened the initial disturbance and development of SWV.The meso-γ-scale large-value areas of positive relative vorticity in the mid-toupper troposphere were largely induced by the diabatic heating and tilting.The strong mid-level convergence was attributed to the mid-level vortex enhancement.The low-level vortex intensification was mainly due to low-level convergence and the stretching of upward flow.The meso-α-scale large-value areas of positive relative vorticity in the low-level could expand up to about 400 hPa,and gradually weakened with time and height due to the decaying low-level convergence and vertical stretching in the matured SWV.As the SWV matured,two secondary circulations were formed,with a weaker mean radial inflow than the outflow and elevated to 300-400 hPa.
基金primarily supported by the National 973 Fundamental Research Program of China(Grant No.2013CB430103)the Department of Transportation Federal Aviation Administration(Grant No.NA17RJ1227)through the National Oceanic and Atmospheric Administration+1 种基金supported by the National Science Foundation of China(Grant No.41405100)the Fundamental Research Funds for the Central Universities(Grant No.20620140343)
文摘The traditional threat score based on fixed thresholds for precipitation verification is sensitive to intensity forecast bias. In this study, the neighborhood precipitation threat score is modified by defining the thresholds in terms of the percentiles of overall precipitation instead of fixed threshold values. The impact of intensity forecast bias on the calculated threat score is reduced. The method is tested with the forecasts of a tropical storm that re-intensified after making landfall and caused heavy flooding. The forecasts are produced with and without radar data assimilation. The forecast with assimilation of both radial velocity and reflectivity produce precipitation patterns that better match observations but have large positive intensity bias. When using fixed thresholds, the neighborhood threat scores fail to yield high scores for forecasts that have good pattern match with observations, due to large intensity bias. In contrast, the percentile-based neighborhood method yields the highest score for the forecast with the best pattern match and the smallest position error. The percentile-based method also yields scores that are more consistent with object-based verifications, which are less sensitive to intensity bias, demonstrating the potential value of percentile-based verification.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant KZCX2-YW-205)the National Natural Science Foundation of China (Grant Nos.40825016,90711004,and 40775083)
文摘In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature and precipitation during the severe snowstorm that occurred in southern China during 0800 26 January to 0800 29 January 2008 （Note that all times are local time except when otherwise stated）. Black carbon aerosol was simulated online within the WRF-Chem. The model resuits showed that surface-albedo, averaged over 27-28 January, can be reduced by up to 10% by the deposition of BC. As a result, relative to a simulation that does not consider deposition of BC on snow/ice, the authors predicted surface air temperatures during 27-28 January can differ by -1.95 to 2.70 K, and the authors predicted accumulated precipitation over 27-28 January can differ by -2.91 to 3.10 mm over Areas A and B with large BC deposition. Different signs of changes are determined by the feedback of clouds and by the availability of water vapor in the atmosphere.
基金supported by NOAA JTTI award via Grant #NA21OAR4590165, NOAA GOESR Program funding via Grant #NA16OAR4320115provided by NOAA/Office of Oceanic and Atmospheric Research under NOAA-University of Oklahoma Cooperative Agreement #NA11OAR4320072, U.S. Department of Commercesupported by the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce via Grant #NA18NWS4680063。
文摘Capabilities to assimilate Geostationary Operational Environmental Satellite “R-series ”(GOES-R) Geostationary Lightning Mapper(GLM) flash extent density(FED) data within the operational Gridpoint Statistical Interpolation ensemble Kalman filter(GSI-EnKF) framework were previously developed and tested with a mesoscale convective system(MCS) case. In this study, such capabilities are further developed to assimilate GOES GLM FED data within the GSI ensemble-variational(EnVar) hybrid data assimilation(DA) framework. The results of assimilating the GLM FED data using 3DVar, and pure En3DVar(PEn3DVar, using 100% ensemble covariance and no static covariance) are compared with those of EnKF/DfEnKF for a supercell storm case. The focus of this study is to validate the correctness and evaluate the performance of the new implementation rather than comparing the performance of FED DA among different DA schemes. Only the results of 3DVar and pEn3DVar are examined and compared with EnKF/DfEnKF. Assimilation of a single FED observation shows that the magnitude and horizontal extent of the analysis increments from PEn3DVar are generally larger than from EnKF, which is mainly caused by using different localization strategies in EnFK/DfEnKF and PEn3DVar as well as the integration limits of the graupel mass in the observation operator. Overall, the forecast performance of PEn3DVar is comparable to EnKF/DfEnKF, suggesting correct implementation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41205099 and 41575037)the National Science Foundation of China (Grant No. 41405128)+2 种基金the National Grand Fundamental Research 973 Programs of China (Grant Nos. 2014CB441403 and 2013CB430105)the Special Scientific Research Project of the Meteorological Public Welfare Profession of China (Grant No. GYHY201006031)the Guizhou Province Scientific Research Joint Project (Grant No. G[2013]4001)
文摘Numerical simulations are carried out to investigate the effect of cloud condensation nuclei（CCN） concentrations on microphysical processes and precipitation characteristics of hailstorms. Two hailstorm cases are simulated, a spring case and a summer case, in a semiarid region of northern China, with the Regional Atmospheric Modeling System. The results are used to investigate the differences and similarities of the CCN effects between spring and summer hailstorms. The similarities are：（1） The total hydrometeor mixing ratio decreases, while the total ice-phase mixing ratio enhances, with increasing CCN concentration;（2） Enhancement of the CCN concentration results in the production of a greater amount of small-sized hydrometeor particles, but a lessening of large-sized hydrometeor particles;（3） As the CCN concentration increases, the supercooled cloud water and rainwater make a lesser contribution to hail, while the ice-phase hydrometeors take on active roles in the growth of hail;（4） When the CCN concentration increases, the amount of total precipitation lessens,while the role played by liquid-phase rainfall in the amount of total precipitation reduces, relatively, compared to that of icephase precipitation. The differences between the two storms include：（1） An increase in the CCN concentration tends to reduce pristine ice mixing ratios in the spring case but enhance them in the summer case;（2） Ice-phase hydrometeor particles contribute more to hail growth in the spring case, while liquid water contributes more in the summer case;（3） An increase in the CCN concentration has different effects on surface hail precipitation in different seasons.
基金supported by National Natural Science Foundation of China (Grant Nos. 40875080 and 40875002)Ministry of Science and Technology of China (Grant No. 2006BAC12B01-01)
文摘The Regional Atmospheric Modeling System (RAMS) has been used to investigate the effects of varied giant cloud condensation nuclei (GCCN) concentrations on precipitation characteristics of the spring hailstorms in a semi-arid region. The simulation result shows that this variation has significant effects on the storm microphysical processes as well as on the surface precipitation. The coverage of hail and hail mixing ratio maxima in cloud increases with greater GCCN concentrations. The accumulation zone structure benefits the growth of hail particles. Higher GCCN concentrations lead to more supercooled rain water and cloud water available for freezing. This simulation also shows that increasing GCCN concentrations may produce more rainfall on the surface but less hail precipitation, and the total accumulated precipitation increases while the ice phase precipitation decreases. This effect is stronger in polluted air than in clean air. The surface flow field changes with different GCCN concentrations. The identification index of spring hailstorm is different from that of summer hailstorm with a different aerosol background.
基金This project is supported by Doctoral Programme Foundation of Institution of Higher Education.
文摘The transports of dust are calculated using 3-dimensional(3-D)trajectory method for three cases of duststorms in the terrain-following coordinate system,and the synoptic processes are also discussed for each case.The case of 17—20 April 1980,a severe duststorm was associated with the rapid development of a cyclone over the Mongolia Plateau.The dust moved from west to east across several deserts,formed a typical dust path in spring.The other two were weaker and the dust was triggered by the strong wind behind the cold front from northwest or north.Because the vertical velocity is considered in 3-D trajectory analysis,trajectories calculated should better reveal the transport rule of the dust particles and the results seem to be more consistent with the synoptic processes.The trajectory analysis on the 2-D isobaric sur- faces is simpler but can be used only in the conditions with weak vertical wind shear and weak vertical velocity.The dif- ference of trajectories at lower levels between two methods may be caused by the different treatment of orography.
基金supported by the National Natural Science Foundation of China(Grant Nos.41630425,41671144074)the Key Research Program of Frontier Science,CAS(Grant No.QYZDJ-SSW-DQC007)the National Key Basic Research Program of China(Grant No.2014CB441401)。
文摘The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model.
