学科分类
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5 个结果
  • 简介:Reliablefielddataforallhydrologicparametersareoftenunavailableforwatershedsevenforthoseintensivelymonitored.Intheabsenceofreliablesuchdata,verifiedmathematicalrelationsforanareacanbeusedforotherareaswithsamehydrologicandclimaticregimes.Theobjectivesofthisresearchwere:1)toassessthetotalrunoffandsedimentloss,and2)todeveloprainfall,runoffandsoillossrelationsforfourprominentlanduses(includingdegraded,pasture,forestandagriculturelands)intheHilkotwatershed(Pakistan).Fourexperimentalnaturalrunoffplotswereestablishedonthelanduses(degraded,pasture,forestandagricultureland).ThefieldstudyanddatacollectionwereconductedintheHilkotwatershedfrom1999to2005.Regressionanalysiswasconductedtoestablishrelationsamongrainfall,runoffandsoillossforalllandusesusing.Regressionanalysisindicatedgoodcorrelationwithfielddata.

  • 标签: 土壤流失量 巴基斯坦 径流 降雨 土地利用 分水岭
  • 简介:Thisstudyintroducesanewdynamicalquantity,sheargradientvorticity(SGV),whichisdefinedasverticalwindshearmultiplyingthehorizontalcomponentofvorticitygradient,aimingtodiagnoseheavyprecipitationinducedbysomestrongconvectiveweathersystems.Thevorticitygradientcomponentcanbeusedtostudythecollisionormergingprocessbetweendifferentvortexesorthedeformationofavortexwithasharpvorticitygradient.Verticalwindshear,anothercontributedcomponentofSGV,alwaysrepresentstheenvironmentaldynamicalfactorinmeteorology.Bythecombinedeffectofthetwocomponents,overall,SGVcanrepresenttheinteractionbetweentheenvironmentalwindshearandtheevolutionofvortexeswithalargevorticitygradient.Othertraditionalvorticity-likedynamicalquantities(suchashelicity)havethelimitationinthediagnosisoftheconvection,sincetheydonotconsiderthevorticitygradient.Fromthisperspective,SGVhasthepotentialtodiagnosesomestrongconvectiveweatherprocesses,suchasExtratropicalTransition(ET)oftropicalcyclonesandtheevolutionofmulticellstorms.TheforecastperformanceofSGVforthenumericalETcaseofTyphoonToraji(0108)hasbeenevaluated.Comparedwithhelicity,SGVhasshownagreateradvantagetoforecastthedistributionofheavyprecipitationmoreaccurately,especiallyinthefrontalzone.

  • 标签: 热带气象 气象学 天气学 气团
  • 简介:河健康能被定义为河流的精力来源,水质量,流动政体,产地和生物区系匹配自然条件到的度。在一条健康的河里,物理过程和形式遗体活跃地连接了并且能互相调整、生物社区有差异的自然层次并且对环境应力有弹性。物理差异和生物多样性影响河健康。物理差异被水文学,hydraulics,和底层管理,在河隧道和邻近的泛滥平原的几何学思考了它为水、河边的有机体创造产地。生物多样性被象竞争和predation那样的生物过程管理,但是生物多样性也反映产地,以及连接的差异,丰富和稳定性。在一个河走廊以内的连接包括纵、侧面、垂直的尺寸。当任何这些交往的部件被人的活动损害,河健康衰退。水坝的累积效果和河的另外的人的改变主要是直接减少物理差异和连接,它间接地减少生物多样性。在水坝影响的河里的物理差异和生物多样性的恢复和维护要求在流动和沉积的驱动程序变量之间的确定的关系供应,和产地,连接,和生物社区的反应变量。这些关系能拿阀值的形式(例如,streambed沉积的乘火车)或反应曲线(例如,泛滥平原淹没的鱼生物资源对程度和持续时间)。我在西方的美国从怀俄明,科罗拉多,和亚利桑那使用例子说明怎么确定在在河里的司机和反应变量之间的关系由水坝影响了。

  • 标签: 河流健康 美国西部 大坝 生物多样性 物理过程 河床沉积物
  • 简介:Twotypicalprovincialcapitals(NanjingandZhengzhou)andtwocounties(RugaoandYuanyang)ineast(JiangsuProvince)andcentral(HenanProvince)Chinawerechosenrespectivelyasthedevelopedandlessdevelopedcomparativecasesforpedodiversityandlandusediversitycorrelativeanalysisbyborrowingtherecentlybetterdevelopedpedodiversitymethodology.Landuseclassificationwasworkedoutusingremotesensingimagesinthreedifferentperiods(1986-1988,2000-2001and2004-2006)forthesestudiedcaseareasbeforethecalculationoftheconstituentdiversityindexandspatialdistributiondiversityindexmodifiedafterShannonentropyin2km×2kmgridscaleofthesoilandlandusepatternwereconductedandthenaconnectionindexwasproposedtoevaluatetherelationshipbetweensoilandlandusediversity.Resultsshowthatduringtheyearsfrom1986to2006,thecompositionandspatialdistributionofregionallandusepatternhadchangedgreatly.TheagriculturallandareaofallthestudiedcaseareasdecreasedobviouslyinwhichNanjinghasthehighestdecrementof895.98km2mainlyintourbanusewhiletheotherlandusetypeareachangesshowthesametrend.Theconnectionindexoffourtypicalsoilfamilytypesandtypicalurbanlandusetypes,i.e.,urbanconstructionland,transportationlandandindustrialandminingareaallincreasedinthisperiod.Inthestudiedcaseareas,thereisthehighestsoilconstituentdiversityinZhengzhouat0.779whilethesimplestsoilconstituentdiversityinRugaoat0.582.MeanwhilewehavehigherlandusediversityinthemoreurbanizedJiangsuProvincethanHenanProvince,Nanjingisrankingthefirstthathasbeengettinghigherandhigherinthethreeperiodsat0.366in1986-1988,0.483in2000-2001and0.545in2004-2006.Finally,theconnectionindexfigurestoevaluatetherelationshipbetweensoilandlandusediversityofthestudiedareaswerecomparedtoshowthesimilarphenomenonthatthisfiguregrowsfastestinNanjingfollowedb

  • 标签: 土地利用格局 土壤多样性 中国地区 土地利用类型 省会城市 城市建设用地
  • 简介:StaticCoulombstresschangeinducedbyearthquakeslipisfrequentlyusedtoexplainearthquakeactivitiesandaftershockdistribution.However,someparametersfortheCoulombstresscalculationareunabletobewellconstrainedfromlaboratoryexperimentsandfieldobservations.DifferentparametersmaydirectlyaffectthepatternofstaticCoulombstress.ThestaticCoulombstresschangesinducedbytheWenchuanearthquakecalculatedbysixresearchgroupsarenotconsistentwitheachother.Toinvestigatehowtheparametersaffectthecalculationresults,wechangetheparametersinturnthroughmodelingandcomparetheresultsofdifferentcalculationparameters.Wefindthatgravity,positionandstrikeofreceiverfaultshavelittleinfluenceoncoseismicCoulombstresscalculations,butotherparameterscanchangethevalueandsignoftheresultsinvariousdegreesespeciallyaroundtheearthquakeruptureplane.ThereforetheuncertaintyanalysisofstaticCoulombstresschangeinducedbyearthquakeshouldbetakenintoconsiderationintheearthquakehazardanalysis.

  • 标签: 不确定性分析 库仑应力 地震发生 应力变化 静态 汶川