简介:BasedontheJointTyphoonWarningCenter(JTWC)best-trackdatasetbetween1965and2009andthecharacteristicparametersincludingtropicalcyclone(TC)position,intensity,pathlengthanddirection,amethodforobjectiveclassificationoftheNorthwesternPacifictropicalcyclonetracksisestablishedbyusingk-meansClustering.TheTClifespan,energy,activeseasonandlandfallprobabilityofsevenclustersoftropicalcyclonetracksarecomparativelyanalyzed.Thecharacteristicsoftheseparametersarequitedifferentamongdifferenttropicalcyclonetrackclusters.Fromthetrendofthepasttwodecades,thefrequencyofthewesternrecurvingcluster(accountingfor21.3%ofthetotal)increased,andthelifespanelongatedslightly,whichdiffersfromtheotherclusters.TheannualvariationofthePowerDissipationIndex(PDI)ofmostclustersmainlydependedontheTCintensityandfrequency.However,theannualvariationofthePDIinthenorthwesternmovingthenrecurvingclusterandthepelagicwest-northwestmovingclustermainlydependedonthefrequency.
简介:Byuseofgeostrophicmomentumapproximation,theanalyticalexpressionsofthewinddistributionwithintheplanetaryboundarylayerandtheverticalvelocityatthetopoftheboundarylayerareobtainedwhenthedistributionofeddytransfercoefficientkisdividedintothreesections:k1z(z0≤z
简介:选用关键区42站1985~1989年高空资料和延安地区同期14时地面资料找出物理意义清楚的因子,作为预报因子制作8月份本地区分县晴雨预报。
简介:2007年12月17~21日,第8届中越灾害性天气研讨会在越南胡志明市召开。来自中越双方的40余位专家出席了此次会议,国家气象中心副主任毕宝贵为团长的中国气象代表团一行8人参加了会议。越南国家水文气象局局长BuiVanDuc博士出席开幕式并致欢迎辞;中国国家气象中心副主任毕宝贵在致辞中,简要介绍了中国的灾害天气情况以及综合观测系统、预报预测系统、公共气象服务系统的有关情况,介绍了我国数值预报的进展,同时也指出了灾害性天气预报和服务所面临的一些问题和困难。两国的18位气象专家的最新研究成果在大会上进行了交流,内容涉及到台风预报、资料同化、中尺度天气分析、短时临近预报以及雷达资料应用等。
简介:CH4emissionrateshavebeenmeasuredcontinuouslyfortheearlyriceof1988andlatericesof1987and1988duringentiregrowingseasonsinaricepaddyfieldinHangzhou,ZhejiangProvince,China,byusinganautomaticsamplingandanalyzingsystem.DuringmostpartsoftheseasonsCH4emissionratesshowedstrongdiurnalvariations.Bi-modepatternswiththehighestvalueintheafternoonandasecondpeakatmid-nightweregenerallyfoundfortheearlyrice,whilethehighestvalueswerealmostalwaysfoundinthenightforthelaterice.Bi-modepatternswithasecondpeakintheafternoonwerealsofoundduringthereproductivephaseofthelatericeplants.Thesediurnalvariationsmaybeexplainedbythediurnalvariationsofthesoiltemperatureandtheactivityofriceplants.Strongseasonalvariationswithonepeakinthetilleringstageandtwoduringthereproductivephaseofriceplantswereobservedforallthethreegrowingseasons.Theseasonalvariationsmaybeexplainedbytheactivityofriceplants,availabilityoforganicsubstratesinthesoil,andtheactivityofsoilbacteriarelatedtosoiltemperatures,FertilizationdidnotshowsignificanteffectsonthetotalseasonalCH4emissionsbutslightlychangedthepatternoftheseasonalvariationsoftheCH4emissionrates.Averagedoverthemeasuringperiodsand8spots,CH4emissionratesof7.8mgm-2h-1fortheearlyriceand28.6mgm-2h-1forthelatericewereobtained.Basedonthesemeasureddata,thetotalglobalemissionofCH4fromricepaddiesisestimatedtobeabout90Tg/yrrangingfrom70to110,accountingfor20%ofthetotalsourceofCH4.