简介:1概况国家干旱政策高级别会议于2013年3月1l~15日在瑞士日内瓦召开。会议由wMO、联合国防治荒漠化公约(UNCCD)和联合国粮农组织(FAO)联合举办。此次会议分为科学会议和高层政策会议两部分。共有300多位代表出席了科学会议,深入探讨了与干旱及其风险管理有关的科学问题,研究应对干旱的多种策略和行动。来自尼日尔、荷兰、瑞士、坦桑尼亚、津巴布韦等20多个国家的政府首脑和部长,以及wMO、UNCCD、FAO等联合国机构的行政首脑出席了高层政策会议,与此前参加科学会议的代表团和科学家们共同通过了“国家干旱政策高级别会议宣言”。
简介:Theformationofatropicalcycloneistheresultofaprocessinwhichaninitialdisturbanceevolvesintoawarm-corelow-pressuresystem;however,theoriginoftheinitialdisturbanceandthefeaturesoftheinitialfieldsareoverlookedinmostexistingtheories.Inthisstudy,basedonFY-2CbrightnesstemperaturedataandtheJapanreanalysisdataset,theoriginandevolutionofthetropicaldisturbancethatbecameTyphoonFung-Wong(2008)wereexamined.Theresultsdemonstratedthattheinitialdisturbanceemergedwithinasaddle-typefieldwithlargeverticaltroposphericwindshear.Theverticalwindsheardecreasedwiththeadjustmentoftheuppercirculation;moreover,accompaniedbyconvectionoverthewarmsectionaroundtheuppercoldvortex,itprovidedfavorablethermalanddynamicconditionsforthedevelopmentofatropicalvortex.Duringitsdevelopment,thezoneofassociatedpositiverelativevorticitystrengthenedanddescendedfromthemid-tropospheretolowerlevels.Thisrapidstrengtheningoflower-levelvorticitywasduetoincreasingconvergencerelatedtotheintensificationofthepressuregradientsouthwestofthesubtropicalhigh.ThisindicatedthattheuppercoldvortexandWestPacificsubtropicalhighplayedveryimportantrolesinthiscase.
简介:AquantitativediagnosisiscarriedoutfortheupwardbranchofalocalmeridionalcirculationoversouthernChina(SC)duringtheabnormalsnowstormswithseverefreezingrainfrom10Januaryto3February2008.Thediagnosticstudyshowsthattheupwardbranchismainlyassociatedwiththezonaladvectionofwesterlymomentumandmeridionaltemperatureadvectioninsteadofthelatentheating(whichiscommonlythedominantfactorinmanyotherstormcases).Thecorrespondingweatheranalysesindicatethat(1)thezonaladvectionofwesterlymomentumrepresentstheeffectoftheupper-leveldivergenceontheanticyclone-shearsideintheentranceofa200hPawesterlyjetwithawestwarddeviationfromitsclimatologicallocationoversouthwesternJapan;(2)themeridionaltemperatureadvectionrepresentstheinteractionbetweenthemid-lowerlayer(850to400hPa)warmadvectionoverSC(aheadoftemperatureandpressuretroughswiththelattertroughdeeperthantheformerintheBayofBengal)andcoldadvectionovernorthChina(steeredbyanunderlyingflowat500hPa);(3)therelativelyweakvaportransport(comparedtothatofspring,summerandautumn)fromtheBayofBengalandtheSouthChinaSeatoSCandtheexistenceofatemperatureinversionlayerinthelowertroposphereoverSCdiminishtheeffectoflatentheating.Withthesignificantincreaseofvaportransportafter24January,theroleoflatentheatingisupgradedtobecomethethirdpositivecontributortotheupwardbranchoverSC.
简介:在中国上的暴风雪的第三个阶段的energetics用ECWMF数据被分析。为中东马槽和在25282008年1月上向中国发展了的西方的和平的马槽的精力预算的分析由是关键来源和与马槽联系的旋涡动能中心的主要水池的ageostrophic风显示出geopotential的移流。精力变换学期,相互作用动能变换和baroclinic变换的大小,太小,不能解释精力中心和喷气条纹的发展。精力中心经由ageostrophicgeopotential流动的集中在他们的入口区域获得了精力,然后由一样的流动在他们的出口区域失去了精力。在入口区域,流动收敛了,增加geopotential坡度,它产生了更大的因地球自转而引起的风和更高的动能,导致在这个区域的一个上升运动。当马槽搬到中国时,流动的集中在入口区域引起的上升运动在中央、南部的中国上加强了暴风雪。
简介:BasedontheB08RDP(Beijing2008OlympicGamesMesoscaleEnsemblePredictionResearchandDevelopmentProject)thatwaslaunchedbytheWorldWeatherResearchProgramme(WWRP)in2004,aregionalensemblepredictionsystem(REPS)ata15-kmhorizontalresolutionwasdevelopedattheNationalMeteorologicalCenter(NMC)oftheChinaMeteorologicalAdministration(CMA).Supplementingtotheforecasters’subjectiveaffirmationonthepromisingperformanceoftheREPSduringthe2008BeijingOlympicGames(BOG),thispaperfocusesontheobjectiveverificationoftheREPSforprecipitationforecastsduringtheBOGperiod.Byuseofasetofadvancedprobabilisticverificationscores,thevalueoftheREPScomparedtothequasi-operationalglobalensemblepredictionsystem(GEPS)isassessedfora36-dayperiod(21July-24August2008).TheevaluationhereinvolvesdifferentaspectsoftheREPSandGEPS,includingtheirgeneralforecastskills,specificattributes(reliabilityandresolution),andrelatedeconomicvalues.TheresultsindicatethattheREPSgenerallyperformssignificantlybetterfortheshort-rangeprecipitationforecaststhantheGEPS,andforlighttoheavyrainfallevents,theREPSprovidesmoreskillfulforecastsforaccumulated6-and24-hprecipitation.ByfurtheridentifyingtheperformanceoftheREPSthroughtheattribute-focusedmeasures,itisfoundthattheadvantagesoftheREPSovertheGEPScomefrombetterreliability(smallerbiasesandbetterdispersion)andincreasedresolution.Also,evaluationofadecision-makingscorerevealsthatamuchlargergroupofusersbenefitsfromusingtheREPSforecaststhanusingthesinglemodel(thecontrolrun)forecasts,especiallyfortheheavyrainfallevents.
简介:利用江西省17个国家级台站1960~2008年逐日降水量资料,对日降水量超过绝对阈值(25mm和50mm)和百分位数阈值(95%和99%)的极端降水变化情况进行了分析。结果表明,江西省近50年极端降水频率和强度均呈波动上升趋势,大雨和强降水频率的增加最为迅速,暴雨和极端强降水事件强度增加最大;夏季各种极端降水事件频率均有明显升高;冬季大雨和强降水事件频率也有显著增加;春季和秋季极端降水强度有明显增加,特别是暴雨和极端强降水事件强度增加迅速;夏季暴雨和极端强降水强度有所降低或略有增加;江西省极端降水的频率和强度变化趋势较为一致,特别是1990年代;极端降水的增加以发生频数的增加为主,降水强度的增加并不显著;近50年江西省大部分地区的极端降水事件频率和强度均有增加,但高值区的分布有较大的差异。极端强降水事件强度在鄱阳湖平原附近减小,而在周边的大部分地区呈增长趋势。进一步的分析发现,极端降水强度的变化与地形有显著的正相关关系。