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：利用2001年—2006年青海省的7个探空站的资料,将青海省分为7个区域,每个区域用一个探空站的资料,根据2001年-2006年青海省56个气象站的冰雹历史个例,分析了冰雹过程环流背景和每个区域的降雹日数时空分布特征,计算了每个区域探空站的08时的k指数,得出这7个分区发生降雹天气时本区域内的探空站08时的k指数的特点,在做青海省的降雹预报时提供一些依据。

简介：Byuseofgeostrophicmomentumapproximation,theanalyticalexpressionsofthewinddistributionwithintheplanetaryboundarylayerandtheverticalvelocityatthetopoftheboundarylayerareobtainedwhenthedistributionofeddytransfercoefficientkisdividedintothreesections:k1z（z0≤zk2（h1≤z