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Characteristics of extreme rainfall and rainbands evolution of Super Typhoon Lekima (2019) during its landfall

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Frontiers of Earth Science 2022年第1期16卷 64-74页

作者： Chunyi XIANG Liguang WU Nannan QIN Key Laboratory of Meteorological Disaster(Ministry of Education) Nanjing University of Information Science and TechnologyNanjing 210044China National Meteorological Center Beijing 100081China Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences Fudan UniversityShanghai 200433China

As one of the most devastating tropical cyclones over the western North Pacific Ocean,Super Typhoon Lekima(2019)has caused a wide range of heavy rainfall in China.Based on the CMA Multi-source merged Precipitation Analysis System(CMPAS)-hourly data set,both the temporal and spatial distribution of extreme rainfall is analyzed.It is found that the heavy rainfall associated with Lekima includes three main episodes with peaks at 3,14 and 24 h after landfall,respectively.The first two rainfall episodes are related to the symmetric outburst of the inner rainband and the persistence of outer rainband.The third rainfall episode is caused by the influence of cold,dry air from higher latitudes and the peripheral circulation of the warm moist tropical storm.The averaged rainrate of inner rainbands underwent an obvious outburst within 6 h after landfall.The asymmetric component of the inner rainbands experienced a transport from North(West)quadrant to East(South)quadrant after landfall which was related to the storm motion other than the Vertical Wind Shear(VWS).Meanwhile the outer rainband in the vicinity of three times of the Radius of Maximum Wind(RMW)was active over a 12-h period since the decay of the inner rainband.The asymmetric component of the outer rainband experienced two significant cyclonical migrations in the northern semicircle.

关键词： extreme rainfall rainband evolution landfalling tropical cyclone

Experiments with the Improved Dynamical-Statistical-Analog Ensemble Forecast Model for landfalling Typhoon Precipitation over South China

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Journal of tropical Meteorology 2022年第2期28卷 139-153页

作者：马蕴琦任福民贾莉丁晨晨 State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 China

In recent work,three physical factors of the Dynamical-Statistical-Analog Ensemble Forecast Model for landfalling Typhoon Precipitation(DSAEF_LTP model)have been introduced,namely,tropical cyclone(TC)track,TC landfall season,and TC intensity.In the present study,we set out to test the forecasting performance of the improved model with new similarity regions and ensemble forecast schemes added.Four experiments associated with the prediction of accumulated precipitation were conducted based on 47 landfalling TCs that occurred over South China during 2004-2018.The first experiment was designed as the DSAEF_LTP model with TC track,TC landfall season,and intensity(DSAEF_LTP-1).The other three experiments were based on the first experiment,but with new ensemble forecast schemes added(DSAEF_LTP-2),new similarity regions added(DSAEF_LTP-3),and both added(DSAEF_LTP-4),respectively.Results showed that,after new similarity regions added into the model(DSAEF_LTP-3),the forecasting performance of the DSAEF_LTP model for heavy rainfall(accumulated precipitation≥250 mm and≥100 mm)improved,and the sum of the threat score(TS250+TS100)increased by 4.44%.Although the forecasting performance of DSAEF_LTP-2 was the same as that of DSAEF_LTP-1,the forecasting performance was significantly improved and better than that of DSAEF_LTP-3 when the new ensemble schemes and similarity regions were added simultaneously(DSAEF_LTP-4),with the TS increasing by 25.36%.Moreover,the forecasting performance of the four experiments was compared with four operational numerical weather prediction models,and the comparison indicated that the DSAEF_LTP model showed advantages in predicting heavy rainfall.Finally,some issues associated with the experimental results and future improvements of the DSAEF_LTP model were discussed.

关键词： landfalling tropical cyclone heavy rainfall forecast DSAEF_LTP model forecasting performance South China

On the Improvement of the DSAEF_LTP Model to Heavy Precipitation Simulation of landfalling tropical cyclones over China in 2018

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Journal of tropical Meteorology 2021年第3期27卷 232-245页

作者：陈禹旭贾莉贾作丁晨晨任福民李国平 College of Atmospheric Sciences Chengdu University of Information TechnologyChengdu 610225 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 China

In this study,the Dynamical-Statistical-Analog Ensemble Forecast model(DSAEF_LTP model)for landfalling tropical cyclone(LTC)precipitation was employed to simulate the precipitation of 10 LTCs that occurred over China in 2018.With similarity region scheme(SRS)parameter values added and TC intensity introduced to the generalized initial value(GIV),four groups of precipitation simulation experiments were designed to verify the forecasting ability of the improved model for more TC samples.Results show that the simulation ability of the DSAEF_LTP model can be optimized regardless of whether adding SRS values only,or introducing TC intensity into GIV,while the experiment with both the two improvements shows a more prominent advantage in simulating the heavier precipitation of LTCs.Compared with four NWP models(i.e.,ECMWF,GFS,GRAPES and SMS-WARMS),the overall forecasting performance of the DSAEF_LTP model achieves a better result in simulating precipitation at the thresholds over 250 mm and performs slightly better than NWP models at the thresholds over 100 mm.

关键词： landfalling tropical cyclone heavy precipitation simulation the DSAEFLTP model similarity region scheme

Large-scale characteristics of landfalling tropical cyclones with abrupt intensity change

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Frontiers of Earth Science 2019年第4期13卷 808-816页

作者： Qianqian JIU Feng XU Jianjun XU Mei LIANG Shifei TU Siqi CHEN South China Sea Institute of Marine Meteorology Guangdong Ocean UniversityZhanjiang 524088China College of Ocean and Meteorology Guangdong Ocean UniversityZhanjiang 524088China Southern Marine Science and Engineering Guangdong Laboratory Zhanjiang 524088China

Data from the China Meteorological Administration and ERA-Interim are used to examine the environmental characteristics of landfalling tropical cyclones(TCs)with abrupt intensity change.The results show that,of all 657 landfalling TCs during 1979-2017,71%,70%and 65%of all landfalling TDs,TSs and TYs,respectively,intensify.Of all the 16595 samples,4.0%and 0.2%of typhoons and tropical storms,respectively,experience over-water rapid intensification(RI)process during their life cycle.Meanwhile,4.5%and 0.6%of typhoons and tropial storms,respectively,undergo overwater rapid decay(RD).These two kinds of cases,i.e.,RI and RD,are used to analyze their associated large-scale conditions.Comparisons show that the RI cases are generally on the south side of the strong western Pacific subtropical high(WPSH);warm sea surface temperatures(SSTs)and sufficient water vapor fluxes existing in RI samples is a dominant feature that is conducive to the development of TCs.Also,the moderate low-level relative vorticity is favorable for TC intensification.On the contrary,the RD TCs are located on the west side of the WPSH;significant decreasing SSTs and low-level water vapor transport may synergistically contribute to RD.Simultaneously,low-level relative vorticity seems to be unfavorable for the development of TCs.

关键词： landfalling tropical cyclone abrupt intensity change environmental factors dynamic composite analysis

Possible Linkage Between tropical Indian Ocean SST Anomalies and the Date of First and Last tropical cyclones landfalling in the Chinese Mainland

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Journal of tropical Meteorology 2022年第1期28卷 71-81页

作者：周群魏立新李敏 National Marine Environmental Forecasting Center Ministry of Natural ResourcesBeijing 100081 China

Bases on the NCEP/NCAR reanalysis products,Had ISST dataset,and data of tropical cyclone(TC)landfalling in the Chinese mainland during 1960-2019,the possible impacts of Indian Ocean Dipole(IOD)mode and Indian Ocean basin(IOB)mode on the last-TC-landfall date(LLD)and first-TC-landfall date(FLD),respectively,are investigated in this study.The LLD is in significantly negative correlation with autumn IOD on the interannual timescale and their association is independent of El Nino-Southern Oscillation(ENSO).The LLD tends to be earlier when the IOD is positive while becomes later when the IOD is negative.An anomalous lower-level anticyclone is located around the Philippines during October-November,resulting from the change of Walker circulation over the tropical Indo-west Pacific Ocean forced by sea surface temperature(SST)anomalies related to a positive IOD event.The Philippines anticyclone anomaly suppresses TC formation there and prevents TCs from landfalling in the Chinese mainland due to the anomalous westerly steering flows over southeast China during October-November,agreeing well with the earlier LLD.However,the robust connection between spring IOB and FLD depends on ENSO episodes in the preceding winter.There is an anticyclonic anomaly around the Philippines caused by the tropical SST anomalies through modulating the Walker circulation during May-June when the IOB is warming in the El Nino decaying phase.Correspondingly,the TC genesis is less frequent near the Philippines and the mid-level steering flows associated with the expanded western Pacific subtropical high are disadvantageous for TCs moving towards southeast China and making landfall during May-June,in accordance with the later FLD.By contrast,cooling IOB condition in spring of a La Nina decaying year and negative IOD cases during autumn could produce a completely reversed atmospheric circulation response,leading to an earlier FLD and a later LLD over the Chinese mainland,respectively.

关键词： IOD IOB ENSO landfalling tropical cyclone

RADAR OBSERVATION OF PRECIPITATION ASYMMETRIES IN tropical cycloneS MAKING LANDFALL ON EAST CHINA COAST

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tropical cyclone Research and Review 2013年第2期2卷 81-95页

作者： DAN WU KUN ZHAO BEN JONG-DAO JOU WEN-CHAU LEE Shanghai Typhoon Institute/China Meteorological Administration Key Laboratory for Mesoscale Severe Weather/MOE and School of Atmospheric Science Nanjing University Department of Atmospheric Sciences National Taiwan University The National Center for Atmospheric Research

This study explores,for the first time,the asymmetric distribution of precipitation in tropical cyclones(TCs) making landfall along east China coast using reflectivity data collected from coastal Doppler radars at China's Mainland and Taiwan.Six TCs(Saomai,Khanun,Wipha,Matsa,Rananim and Krosa) from 2004 to 2007 are examined.The temporal and spatial evolution of these TCs’ inner and outer core asymmetric precipitation patterns before and after landfall is investigated.The radius of inner-core region is a function of the size of a TC apart from a fixed radius(100 km) adopted in previous studies.All six TCs possessed distinct asymmetric precipitation patterns between the inner-and outer-core regions.The amplitude of asymmetry decreases with the increasing TC intensity and it displays an ascending(descending) trend in the inner(outer) core.In the inner-core region,the heavy rainfall with reflectivity factor above 40 d BZ tends to locate at the downshear side before landfall.Four cases have precipitation maxima on the downshear left side,in agreement with previous studies.As TCs approaching land(~ 2 hr before landfall),their precipitation maxima generally shift to the front quadrant of the motion partly due to the interaction of TC with the land surface.In the outer-core region,the precipitation maxima occur in the front quadrant of the motion in five of the six cases before landfall.After landfall,the precipitation maxima shift from the right-front quadrant clockwisely to the right-rear quadrant of the motion collocated well with the mountainous areas along the coast,which indicates the impact of topography forcing on the precipitation distribution.This study illustrated how the precipitation asymmetry in the inner-and outer-core at different stages of TC landfall is affected by storm motion,vertical wind shear and topography.

关键词： landfalling tropical cyclone asymmetric precipitation distribution East China