Abstract:Heavy rainfall prediction is challenging because different trigger mechanisms and atmospheric conditions lead to different evolution processes.Based on X-band phased array antenna weather radar(XPAR)data and S-band dual-polarization Doppler weather radar(SPOL)data,this paper compares two local heavy rainfall events that occurred in Wuhu on June 5,2022,and in Shanghai on June 29,2022 to explore the spatial variations of reflectivity factor and wind field during the development of the two heavy rainfall processes,with an emphasis on the convective evolution of the Shanghai storm.The results show that:(1)The heavy rainfall in Wuhu occurred under a cold-frontal weather background,triggered by the southward-moving cold front and the low-level shear line,which was a weak cold front rainstorm.In contrast,the short-term heavy rainfall in Shanghai was a rainstorm process within the warmsector.It resulted from a weak synoptic-scale disturbance,where shallow cold air intrusion from thesurface interacted with warm-moist air to form a mesoscale convergence belt,thereby triggering theconvection.(2)During Wuhu rainfall,a small-scale meridional vertical circulation in the warm-moist air ahead of the cold front provided updrafts for the heavy rainfall.During the process of convective rainfall in Shanghai,due to the intrusion of shallow cold air near the surface air and the cold outflow of the thunderstorm,new cells were triggered intermittently by the northernly air in front of the thunderstorm.(3)The weak cold front type of rainstorm system in Wuhu was stable,varies slowly,with no obvious cell initiation or merging,so the rainstorm development is easy to predict.As for the local warm sector heavy rainfall in Shanghai,it is difficult to forecast the development because of its small scale,strong convection,rapid evolution with new convective cell initiation,merging and dissipation.

Abstract:Based on multiband radar monitoring data from Zhongshan City and Guangdong lightning positioning system data,combining model calculations,we investigated a lightning strike incident on Shitou Mountain in Zhongshan City on April 5,2024.This event,which caused transient cardiorespiratory arrest and suspended animation in one victim,occurred at the southern periphery of a convective cloud cluster during brief showers.The lightning channel featured dual-ground termination points(peak current:-20 kA)that preferentially struck two adjacent trees before side-flashing to a victim located only 0.2 m away.Calculations indicate the victim experienced both a direct strike(2.312 kA)and step voltage(348.04 kV).A witness standing 1.1 m from the tree was exposed to about 22.6 kV step voltage(below the 43.96 kV safety threshold),reporting only finger numbness.The accompanying children at 2-3 m distance experienced 3.61-7.56 kV step voltage with no effects.

Abstract:This study investigates the precipitation structures and environmental conditions of Extreme Precipitation Events(EPEs)over South China during the warm season(April-September,1998-2013)using TRMM satellite data.The structure and environmental characteristics of the Non-Extreme Precipitation Events(NonEPEs),including thunderstorm,and the convective NonEPEs(NonEPE_Inten),which lacks extreme precipitation,are compared and analyzed.The hourly extreme precipitation threshold is defined using the 99.9th percentile of hourly precipitation data of about 1 500 stations in South China during 1981-2013.EPE(NonEPE)refers a convective system in which the intensity of the precipitation center meets(does not meet)the extreme hourly precipitation threshold,and the precipitation area is at least 100 km2.Results indicate that the horizontal scale of EPE over South China exhibits meso-βscale(45-50 km),which is the scale of thunderstorms.Most EPEs occur in organized mesoscale convective systems(horizontal scale>100 km),while NonEPEs primarily occur in relatively small-scale convective systems(horizontal scale<100 km).Satellite microwave observations indicate that EPEs contain abundant ice particles.The vertical structure of EPE is significantly different from that of strong convections.The radar reflectivity of EPE(non-EPE)increases by 6-7 dBZ(2-3 dBZ)below the melt layer,indicating EPE has a more active warm rain or collision-coalescence process with higher raindrop growth efficiency.In terms of environmental conditions,EPE show higher relative humidity,stronger 700-925 hPa wind shear,thicker warm cloud depth,weaker convective effective potential energy(CAPE),and lower low-level temperature.

Abstract:This study develops grid-based objective identification criteria for persistent heavy precipitation events(PHPEs)in South China during May-September using daily precipitation observations from 2 407 stations across China(1961-2015).We then evaluated extended-range forecast skill using a Comprehensive Test Score(CTS)and improved dichotomous metrics,assessing multi-model ensemble means constructed from different proportions of top-ranked members based on the reforecast data from four operational models in the World Meteorological Organization's(WMO)Subseasonal-to-Seasonal(S2S)Prediction Project-the European Centre for Medium-Range Forecasts(ECMWF),China Meteorological Administration(CMA),United Kingdom Met Office(UKMO),and National Centers for Environmental Prediction(NCEP).The results show that South China experiences an average of 4.5 PHPEs per year,with significant interannual variability ranging from a minimum of 2 to a maximum of 8 events.The duration is mainly 3-7 days,and the longest duration can be up to 19 days with an increasing trend.The CTS,threat score(TS),and equitable threat score(ETS)decrease as more ensemble members in descending order are included in the mean.Among individual models,NCEP performs best in terms of CTS,while UKMO shows slightly better performance than ECMWF and NCEP according to TS and ETS.The CMA model exhibits the lowest skill across all metrics.The multi-model ensemble achieves the highest forecast skill when combining the top 50%of ensemble members.Additionally,all-ensemble-mean forecasts show higher scores for heavy precipitation events with longer durations.The results can provide valuable insights for real-time monitoring and subseasonal forecasting of PHPEs.

Abstract:A supercell accompanied with severe hail in southern Fujian on 26 March 2022 is analyzed based on observations of Xiamen Haicang X-band dual polarization phased array radar,S-band Doppler dual polarization radar,and Quanzhou S-band Doppler radar,combined with conventional meteorological observation.The study yields the following results.(1)By using three radars for collaborative observation of hail supercells,more comprehensive radar hail characteristics can be obtained,which may improve the warning ability of severe weather.(2)The Haicang X-band phased array radar fully observs the process of hook shaped echo evolution within 10 minutes,and the dual polarization characteristics such as ZDR arc,KDP foot,ZDR ring,and CC ring reflect the changes in particle phase state within the supercell.The back of the strong echo is attenuated,resulting in V-shaped notches or even missing echoes.The appearance of KDP hole in the strong echo area indicates the presence of large hail.When hail grows,the echo intensity increases,the ZDR and KDP high value areas decrease,and CC decreases;When hail falls,ZDR increases,KDP significantly increases,and CC decreases near the melting layer.(3)Quanzhou S-band radar observs classic hail features such as hook shaped echoes,bounded weak echoes,three body scattering,and storm top divergence.The rapid decline of HT and VIL reflects the characteristics of hail falling.The strengthening and weakening of mesocyclones provide a good indicator for determining the strength changes of supercells.(4)The X-band phased array radar detection capability is better than that of Haicang S-band radar,and its KDP performance is better than that of S-band radar in effective echoes.X-band phased array radar has enhanced detection sensitivity in liquid particle detection.However,X-band phased array radar shows reduced detection capability for reflectivities below 15 dBZ and above 70 dBZ compared to the Haicang S-band radar,and the gust front of the supercell is not detected.Its detection intensity is about 5-20 dBZ lower than that of S-band radar.

Abstract:Using daily precipitation data,ERA5 reanalysis data and NOAA monthly sea surface temperature(SST)data from 1991 to 2020,we employed Empirical Orthogonal Function(EOF)analysis and water vapor budget diagnostics to investigate the characteristics of frontal precipitation in South China during the pre-rainy season(FRSCPS)and its response to Indian Ocean SST anomalies.The results indicate that the leading spatial mode of FRSCPS is characterized by a regionally coherent pattern across South China.During flood years,the Western Pacific Subtropical High shifts westward,accompanied by an anomalous cyclone in the lower troposphere.This configuration induces air mass convergence,enhances upward motion,and promotes anomalous moisture flux convergence,which increases precipitation.The circulation during drought years exhibits opposite patterns.The abnormal FRSCPS is primarily influenced by two dynamic factors:changes in moisture advection and the dynamic contribution from wind field convergence and divergence,with the latter playing a dominant role.Meridional moisture transport in the lower troposphere is crucial for FRSCPS.Positive SST anomalies in the Indian Ocean key regions(80-108°E,12°S-14°N)excite eastward propagation Kelvin waves by triggering atmosphere heating via latent heat release from condensation,leading to an anomalous anticyclonic in the lower troposphere over the South China Sea-Western Pacific region,thereby enhancing the meridional moisture transport to South China and increasing precipitation.

Abstract:To address the slow development of typhoon catastrophe insurance in China,insufficient risk quantification abilities,and lack of sophisticated catastrophe models for the quantitative catastrophic loss assessment,China Re Catastrophe Risk Management Company,in collaboration with the Chinese Academy of Meteorological Sciences and other professional research institutions,has successfully developed a real-time typhoon loss assessment system called"Eye of Wind".This typhoon catastrophe model,engineered for the insurance industry,is based on independent intellectual property rights.Utilizing the"Eye of Wind"system across different typhoon forecast path scenarios,this study conducts a quantitative pre-assessment of potential economic losses from two representative typhoons in 2023,"Saola"and"Khanun".According to the model's estimation,Typhoon"Saola"would cause comprehensive property damage losses of approximately 1.5-6.7 billion CNY in some areas of Guangdong Province,Fujian Province,Guangxi Zhuang Autonomous Region,and Jiangxi Province,including residential,industrial and mining enterprises,and public infrastructure losses.For Typhoon"Khanun",the model predicts it would cause 50-500 million CNY in similar aspects of losses in affected regions of Liaoning Province,Jilin Province,and Heilongjiang Province.Compared with actual conditions,the results show that the"Eye of Wind"model performs well in simulating the disaster losses.This model will provide crucial technical support for the typhoon catastrophe identification,quantitative assessment,actuarial pricing,portfolio optimization,risk accumulation control,and reinsurance structuring,significantly enhancing China's insurance industry in typhoon catastrophe risk management.

Abstract:Climate change strongly affects human society.Further research is required to fully understand how the climatic conditions affect human health,particularly mental health.This study investigates how seasonal climatic conditions affect seasonal affective disorder using data from the China Family Panel Study(CFPS,N=58 256),based on nationally representative data from 2012 to 2020.We analyzed the impact of temperature,relative humidity and climate amenity on depression,and compared the effects under different geographical locations and social demographic factors,including gender,age,and household registration.The results are shown as follows.(1)During spring and summer,all meteorological factors significantly affected depression.The climate amenity influence was more significant than that of basic meteorological factors.The results showed that meteorological factors were all significantly and negatively related to depression,except for the Cool Index,which was positively related to depression.(2)When temperature and relative humidity were controlled simultaneously,the influence on depression was more obvious than that of individual meteorological factor.(3)Different effects of meteorological conditions on depression existed in the same season in different regions.All meteorological indicators on depression showed significant effects in northern cities,while no significant effect was found in the southern cities.(4)Socio-demographic factors also significantly affected depression.For example,the larger the proportion of unmarried population,the higher the level of public depression would be.This study enhances understanding for psychologists,climate scientists,and policymakers regarding psychology application in climate practices and public mental health response.This offers insights for climate-resilient society health strageties.

Abstract:Fengyun-4B(FY-4B)is the latest generation of China's geostationary meteorological satellite,providing atmospheric motion vector(AMV)data with higher spatial-temporal resolution.To facilitate the application of FY-4B AMV data in numerical models,this study conducts a comparative analysis between FY-4B AMV and FY-4A AMV datasets.First,we analyze the vertical distribution of observation errors and update the default error settings in the Weather Research and Forecasting Model Data Assimilation System(WRFDA).Then,we investigate the impact of AMV data assimilation on the forecast of Typhoon Muifa in 2022.The results indicate that the U and V wind components of the FY-4B AMV data exhibit smaller observational errors overall than those of FY-4A.While assimilating FY-4A AMV data leads to a westward bias in the simulated typhoon track,FY-4B AMV assimilation improves the dynamic structure of the typhoon's core region,enhancing westerly winds in the middle-upper troposphere and producing a more accurate track forecast.FY-4B AMV assimilation demonstrates superior performance in precipitation forecasting compared to FY-4A.

Abstract:In this paper, correlation statistics and analysis between the storm rainfall far from typhoon and non-zonal high level jet streak(NHJ) were carried out. The results show that: The high level jet streak(HJ) in 200 hPa is constantly SW(90.2 percent) during the period of which storm rainfall occurs. Rainfall area lies in the right behind regions of HJ axes. While storm is being intensive, the HJ has a trend that non-zonal feature become stronger. In terms of MM4 model, numerical simulation and diagnosis were carried out for 9711 typhoon on 19th to 20th August, 1997. The far distant rainfall storm is tightly correlative to the NHJ and low level typhoon trough. The divergence field of HJ is related to v component. The upper level can caused the allobaric wind convergence at low level. This is the result of the form of low level typhoon trough and the strength of the storm. By scale analysis , there exists one branch of middle scale transverse inverse circulation in the right entrance regions behind the HJ below the 300 hPa level, which is very important to the keeping and strengthening of rainfall storm. This branch of inverse circulation is relative to the reinforcement of HJ's non-zonal characteristics. From the field of middle scale divergence field and non-zonal wind field we can find that: The stronger symmetry caused by transverse circulation in the two sides of HJ, rainfall's feedback and reinforcement of HJ's non-zonal characteristics leaded to positive feedback mechanism that was favorable of storm rainfall's strengthening.