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Journal of Tropical Meteorology 2021年第2期27卷 94-108页

作者： LI Hui-qi LIU Xian-tong XIAO Hui wan qi-lin Guangzhou Institute of Tropical and Marine Meteorology China Meteorological AdministrationGuangzhou 510640 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 China

This study explores the potential for directly assimilating polarimetric radar data(including reflectivity Z and differential reflectivity Z_(DR))using an ensemble Kalman filter(EnKF)based on the Weather Research and Forecasting model to improve analysis and forecast of Tropical Storm Ewiniar(2018).Ewiniar weakened but brought about heavy rainfall over Guangdong,China after its final *** the present study,two experiments are performed,one assimilating only Z and the other assimilating both Z and Z_(DR).Assimilation of Z_(DR)together with Z effectively modifies hydrometeor fields,and improves the forecast of the intensity,shape and position of *** of 24-hour extraordinary rainfall≥250 mm is significantly *** can also be seen in the wind fields because of cross-variable *** current study shows the possibility of applying polarimetric radar data to improve forecasting of tropical cyclones,which deserves more research in the future.

关键词： data assimilation polarimetric radar EnKF tropical cyclone heavy rainfall

THE EFFECT OF SAMPLE OPTIMIZATION ON THE ENSEMBLE KALMAN FILTER IN FORECASTING TYPHOON RAMMASUN(2014)

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Journal of Tropical Meteorology 2018年第4期24卷 433-447页

作者： LI Ji-hang wan qi-lin GAO Yu-dong XIAO Hui Key Laboratory of Regional Numerical Weather Prediction Guangzhou Institute of Tropical and Marine Meteorology

In a limited number of ensembles, some samples do not adequately reflect the true atmospheric state and can in turn affect forecast performance. This study explored the feasibility of sample optimization using the ensemble Kalman filter(EnKF) for a simulation of the 2014 Super Typhoon Rammasun, which made landfall in southern China in July 2014. Under the premise of sufficient ensemble spread, keeping samples with a good fit to observations and eliminating those with poor fit can affect the performance of En KF. In the sample optimization, states were selected based on the sample spatial correlation between the ensemble state and observations. The method discarded ensemble states that were less representative and, to maintain the overall ensemble size, generated new ensemble states by reproducing them from ensemble states with a good fit by adding random noise. Sample selection was performed based on radar echo data. Results showed that applying En KF with optimized samples improved the estimated track, intensity,precipitation distribution, and inner-core structure of Typhoon Rammasun. Therefore, the authors proposed that distinguishing between samples with good and poor fits is vital for ensemble prediction, suggesting that sample optimization is necessary to the effective use of En KF.

关键词： data assimilation ensemble prediction sample optimization Typhoon Rammasun ensemble Kalman filter

SPATIOTEMPORAL DISTRIBUTION CHARACTERISTICS AND VARIATION TRENDS OF HIERARCHICAL PRECIPITATION IN GUANGDONG PROVINCE OVER THE PAST 50 YEARS

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Journal of Tropical Meteorology 2018年第1期24卷 82-91页

作者： LIU Xian-tong ZHENG Teng-fei wan qi-lin YU Xin Guangzhou Institute of Tropical and Marine Meteorology CMAGuangzhou 510640 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 China Guangdong Provincial Meteorological Observatory Guangzhou 510640 China

The climatic characteristics of the precipitation in Guangdong province over the past 50 years were analyzed based on the daily rainfall datasets of 86 stations from 1961 to 2010. The rainfall was divided into five categories according to its intensity, and their spatiotemporal characteristics and variation trends were investigated. The annual rainfall amount was within 1,500 to 2,000 mm over most parts of Guangdong, but substantial differences of rainfall amount and rainy days were found among different parts of the province. There were many rainy days in the dry seasons （October to March）, but the daily rainfall amounts are small. The rainy seasons （April to September） have not only many rainy days but also heavy daily rainfall amounts. The spatial distributions of light rainy days （1 mm〈P〈 10 mm） and moderate rainy days （10 mm〈P〈 25 mm） resemble each other. The heavy rainy days （25 mm〈P〈 50 mm）, rainstorm days （50 ram〈P〈 100 mm） and downpour days （P〉 100 mm） are generally concentrated in three regions, qingyuan, Yangjiang, and Haifeng/Lufeng. The average rainfall amount for rainy days increases form the north to the south of Guangdong, while decreasing as the rainfall intensity increases. The contributions from light, moderate and heavy rain to the total rainfall decreases form the north to the south. The annual rainy days show a decreasing trend in the past 50 years. The light rainy days decreased significantly while the heavy, rainstorm and downpour rainy days increased slightly. The annual total rainfall amount increased over the past 50 years, which was contributed by heavy, rainstorm and downpour rains, while the contribution from light and moderate rains decreased. Key words： spatiotemporal distribution; rainfall amount; rainy days; rainfall contribution rate

关键词： spatiotemporal distribution rainfall amount rainy days rainfall contribution rate

Occurrences of Wintertime Tropical Cyclones in the Western North Pacific under the Background of Global Warming

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Atmospheric and Oceanic Science Letters 2009年第6期2卷 333-338页

作者： HE Jie-lin GUAN Zhao-Yong qiAN Dai-Li wan qi-lin wanG Li-Juan Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science ＆Technology Nanjing 210044 China Yulin City Meteorological Bureau of Guangxi Yulin 537000 China Guangzhou Institute of Tropical and Oceanic Meteorology CMA Guangzhou 510080 China

Using tropical cyclone （TC） observations over a 58-yr period （1949-2006） from the China Meteorological Administration, the 40-year ECMWF Reanalysis （ERA-40）, NCEP-NCAR reanalysis, and the Hadley Centre sea ice and sea surface temperature （HadISST） datasets, the authors have examined the behaviors of tropical cyclones （TCs） in the western north Pacific （WNP） in boreal winter （November-December-January-February）. The results demonstrate that the occurrences of wintertime TCs, including super typhoons, have decreased over the 58 years. More TCs are found to move westward than northeastward, and the annual total number of parabolic-track-type TCs is found to be decreasing. It is shown that negative sea surface temperature anomalies （SSTAs） related to La Nifia events in the equatorial central Pacific facilitate more TC genesis in the WNP region. Large-scale anomalous cyclonic circulations in the tropical WNP in the lower troposphere are observed to be favorable for cyclogenesis in this area. On the contrary, the positive SSTAs and anomalous anticyclonic circulations that related to E1 Nifio events responsible for fewer TC genesis. Under the background of global warming, the western Pacific subtropical high tends to intensify and to expand more westward in the WNP, and the SSTAs display an increasing trend in the equatorial eastern-central Pacific. These climate trends of both atmospheric circulation and SSTAs affect wintertime TCs, inducing fewer TC occurrences and causing more TCs to move westward.

关键词： tropical cyclone frequency track boreal winter global warming

SAMPLE OPTIMIZATION OF ENSEMBLE FORECAST TO SIMULATE TROPICAL STORMS(MERBOK, MAWAR, AND GUCHOL) USING THE OBSERVED TRACK

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Journal of Tropical Meteorology 2020年第1期26卷 14-26页

作者： LI Ji-hang GAO Yu-dong wan qi-lin ZHANG Xu-bin Guangzhou Institute of Tropical and Marine Meteorology CMA Guangzhou 510641 China

Nowadays,ensemble forecasting is popular in numerical weather prediction(NWP).However,an ensemble may not produce a perfect Gaussian probability distribution due to limited members and the fact that some members significantly deviate from the true atmospheric ***,event samples with small probabilities may downgrade the accuracy of an ensemble *** this study,the evolution of tropical storms(weak typhoon)was investigated and an observed tropical storm track was used to limit the probability distribution of *** ensemble forecast method used pure observation data instead of assimilated *** addition,the prediction results for three tropical storm systems,Merbok,Mawar,and Guchol,showed that track and intensity errors could be reduced through sample *** the research,the vertical structures of these tropical storms were compared,and the existence of different thermal structures was *** possible reason for structural differences is sample optimization,and it may affect storm intensity and track.

关键词： ensemble forecast sample optimization tropical storm observed track

AN OBSERVATIONAL ANALYSIS OF A TORRENTIAL RAINSTORM IN THE WARM SECTOR OF SOUTH CHINA COASTAL AREAS

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Journal of Tropical Meteorology 2018年第4期24卷 481-493页

作者： ZHENG Teng-fei YU Xin HUANG Jian wan qi-lin LIU Xian-tong Guangzhou Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction CMA Guangdong Provincial Meteorological Observatory/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction CMA

On May 20 th 2007, a brief but severe downpour rainstorm occurred in the coastal areas of Maoming and Yangjiang with rainfall of 115 mm per hour. Data from NCEP/NCAR reanalysis with 1°×1° resolution, Doppler weather radar, conventional surface observations, high-altitude radiosonde and wind profiler radar were used to analyze characteristics and contributions of synoptic scale and mesoscale systems during this torrential rainstorm. The results showed that:(1) the storm was caused by a quasi-linear mesoscale convective system(MCS) and the slow-movement of this system was the primary trigger of the torrential downpour;(2) water vapor was abundant, nearly saturated and in steady state throughout the atmosphere before the storm; intrusion of the weak dry and cold air in the middle level and a striking "dry above and wet below " structure had increased the atmospheric instability;(3) low-level southwesterly airflow from a low pressure(trough) at the Beibu Gulf provided abundant water vapor at the onset of the rainstorm; a deep dry layer was formed by dry and cold air behind the high-level trough, which facilitated latent heat release;upper-level divergence and low-level convergence circulations also provided vertical uplift for warm and moist air at the lower level;(4) Topography only played a minor role as the MCS developed and strengthened over relatively flat coastal terrain. Low level density flow induced by convection triggered new convective cell generation at the leading edge of the convective system, thereby playing a key role in the change of temperature gradient at lower layers, and resulting in strengthening atmospheric instability.

关键词： south China coastal areas rainstorm in the warm sector synoptic scale systems mesoscale process

Raindrop Size Distribution Parameters Retrieved from Xinfeng C-Band Polarimetric Radar Observations

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Journal of Tropical Meteorology 2020年第3期26卷 275-285页

作者： DING Yan wan qi-lin YANG ling LIU Xian-tong XIA Feng FENG Lu College of Electronic Engineering Chengdu University of Information TechnologyChengdu 610225 China China Meteorological Administration Key Laboratory of Atmospheric Sounding Guangzhou 510641 China Guangzhou Institute of Tropical and Marine Meteorology China Meteorological AdministrationChengdu 610225 China

The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south *** observation period of the precipitation process was selected,and the shape-slope(μ-Λ)relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer(2DVD)at Xinfeng Station,Guangdong *** data of the C-band polarimetric radar reflectivity ZHHand differential reflectivity ZDRwere obtained through scattering *** simulation data were combined with DSD fitting to determine the ZDR-Λand log10(ZHH/N0)-Λ*** Xinfeng C-band polarimetric radar observations ZDRand ZHH,the raindrop Gamma size distribution parametersμ,Λ,and N0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was *** research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity(R),mass-weighted mean diameter(Dm)and intercept parameter(Nw)with time obtained by radar retrieval are basically consistent with the observational results of the *** scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical *** method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation *** present research will facilitate radar data assimilation in the future.

关键词： C-band polarimetric radar 2DVD raindrop size distribution DSDs retrieval precipitation characteristics

CAUSAL ANALYSIS AND NUMERICAL MODElinG OF THE INSHORE INTENSIFICATION OF SUPER TYPHOON “HATO”

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Journal of Tropical Meteorology 2019年第3期25卷 293-303页

作者： YU Xin ZHENG Teng-fei wan qi-lin XIAO Hui LIU Xian-tong wanG Ting Guangdong Provincial Meteorological Observatory/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction CMAGuangzhou 510641 China Guangzhou Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction CMAGuangzhou 510641 China

This paper comprehensively analyzes the characteristics and cause of the inshore intensification of super typhoon 'Hato', the 13 th super typhoon in 2017. The aspects of typhoon structure, evolution of large-scale circulation and physical quantity field are analyzed using observation data from the Guangdong Automatic Station, Shenzhen Doppler Radar data, NCEP 1°×1° reanalysis data, NCEP 0.25°×0.25° sea surface temperature(SST) data, ***, in order to investigate the influence of SST change on the intensity of 'Hato', the WRF model and ECMWF 0.125°×0.125° reanalysis data are combined to conduct 3 sensitivity tests on'Hato'. The results show that the favorable conditions for inshore intensification of 'Hato'included the strengthening and westward extension of the subtropical high, continuous increase of low level moisture transport, an anomalous warm SST area north of 20°N in the South China Sea, an extreme divergence value in the northern South China Sea exceeding 6 ×10-5 s-1, and vertical environmental wind shear between 1.1 m/s-4.8 m/s. The intensity of'Hato'was very sensitive to changes in SST. When the SST rose or dropped by 2℃, the minimum central pressure of the typhoon changed by about 13 hPa or 11 hPa,respectively. SST indirectly influenced the intensity of the typhoon through affecting latent heat transport and sensible heat transport.

关键词： super typhoon "Hato" inshore intensification sea surface temperature(SST) sensitivity test

NUMERICAL PREDICTION OF AN EXTREME RAINSTORM OVER THE PEARL RIVER DELTA REGION ON 7 MAY 2017 BASED ON WRF-ENKF

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Journal of Tropical Meteorology 2019年第3期25卷 312-323页

作者： XIAO Hui wan qi-lin LIU Xian-tong ZHENG Teng-fei FENG Lu XIA Feng CHEN Jing-hua Guangzhou Institute of Tropical and Marine Meteorology CMAGuangzhou 510641 China Nanjing University of Information Science and Technology Nanjing 210044 China

An ensemble Kalman filter based on the Weather Research and Forecasting Model(WRF-En KF) is used to explore the effectiveness of the assimilation of surface observation data in an extreme local rainstorm over the Pearl River Delta region on 7 May 2017. Before the occurrence of rainstorm, the signals of weather forecasts in this case are too weak to be predicted by numerical weather model, but the surface temperature over the urban area are high. The results of this study show that the wind field, temperature, and water vapor are obviously adjusted by assimilating surface data of 10-m wind, 2-m temperature, and 2-m water vapor mixing ratio at 2300 BST 6 May, especially below the height of 2 km. The southerly wind over the Pearl River Delta region is enhanced, and the convergence of wind over the northern Guangzhou city is also enhanced. Additionally, temperature, water vapor mixing ratio and pseudoequivalent potential temperature are obviously increased over the urban region, providing favorable conditions for the occurrence of heavy precipitation. After assimilation, the predictions of 12-h rainfall amount, temperature, and relative humidity are significantly improved, and the rainfall intensity and distribution in this case can be successfully reproduced. Moreover, sensitivity tests suggest that the assimilation of 2-m temperature is the key to predict this extreme rainfall and just assimilating data of surface wind or water vapor is not workable, implying that urban heat island effect may be an important factor in this extreme rainstorm.

关键词： extreme rainfall 2-m temperature assimilation of surface observations WRF-EnKF rainstorm

Kinematics and Microphysical Characteristics of the First Intense Rainfall Convective Storm Observed by Jiangsu Polarimetric Radar Network

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Journal of Tropical Meteorology 2022年第2期28卷 169-182页

作者： wanG Kun XIA Xin MEI Yi-qing JIANG Ning wan qi-lin LI Min GU Pei-shu PENG Xiao-yan Nantong Meteorological Bureau NantongJiangsu 226000 China Guangdong-Hong Kong-Macao Greater Bay Area Weather Research Center for Monitoring Warning and Forecasting ShenzhenGuangdong 518000 China State Key Laboratory of Severe Weather(LASW)and Institute of Climate System Chinese Academy of Meteorological SciencesBeijing 100081 China Haimen Meteorological Bureau NantongJiangsu 226100 China

The polarimetric radar network in Jiangsu Province has just been operationalized since *** first intense precipitation event observed by this polarimetric radar network and disdrometer occurred during August 28-29,2020 and caused severe flooding and serious damage in eastern Jiangsu *** microphysics and kinetics for this heavy precipitation convective storm is diagnosed in this study,in order to promote the application of this polarimetric radar *** size distribution(DSD)of this event is estimated from measurements of a ground disdrometer,and the corresponding three-dimensional atmospheric microphysical features are obtained from the multiple polarimetric *** to features of updraft and lighting,the evolution of the convective storm is divided into four stages:developing,mature with lightning,mature without lightning and *** DSD of this event is featured by a large number of raindrops and a considerable number of large *** microphysical characteristics are similar to those of warm-rain process,and ice-phase microphysical processes are active in the mature *** composite vertical structure of the convective storm indicates that deep ZDR and KDP columns coincide with strong updrafts during both mature *** hierarchical microphysical structure retrieved by the Hydrometeor Identification Algorithm(HID)shows that depositional growth has occurred above the melting level,and aggregation is the most widespread ice-phase process at the-10℃level or *** negative lightning activity,the presence of strongest updrafts and a large amount of ice-phase graupel by riming between the 0℃and-35℃layers generate strong negative electric fields within the *** convective storms are typical warm clouds with very high precipitation efficiency,which cause high concentration of raindrops,especially the presence of large raindrops within a short period of *** ice-phase microphysical processes above the me

关键词： convective storms cloud microphysics lightning warm rain polarimetric S-band radar observations