CAJ | 학술논문

采用MM5非静力原始方程中尺度模式模拟了1995年7月26日发生在高原上的中尺度对流系统(MCS).(1)模式基本上模拟出26日高原上MCS发生发展的大尺度背景场,它们是强大的对流层高层青藏高原反气旋高压和强的低层热力强迫.模式还得到了与MCS相联的α中尺度涡旋,它能在500 hPa实测风场中得到反映,而且,模式模拟的400 hPa雨水混合比场在一定程度上模拟了MCS在Tbb图上反映的β中尺度次级结构特征.另一方面,模拟存在的差异也是明显的,例如:时间上有3小时滞后;模拟的MCS α中尺度涡旋位置偏西3-5个经度.(2)模拟的α中尺度气旋性涡旋的结构和演变是高原上探空资料难于描述的.模拟的结果表明,它只限于高原上在450 hPa以下的对流层中低层,范围向上减小,在500 hPa直径约4个经纬度.这个中低层涡旋对应上升运动区,但它的上方是反气旋涡度,对应下沉运动.该涡旋是在高原上从无到有发展出来的,出现在MCS成熟阶段和之后,持续3-6个小时.在它的形成和消亡时都是位势高度场的变化先于风场的变化,这表明该涡旋与高原上的热力作用密切相联.(3)一系列模式敏感性试验考察了不同的物理过程和高原地表热力强迫对高原上MCS的影响.结果表明,文中的高原上MCS在高层青藏高原反气旋高压的大尺度背景下主要受中低层热力强迫的支配.这些模拟结果暗示出一定的高层大尺度背景下适当的低层热力效应就有可能在高原上形成MCS的可能性.
채용MM5비정력원시방정중척도모식모의료1995년7월26일발생재고원상적중척도대류계통(MCS).(1)모식기본상모의출26일고원상MCS발생발전적대척도배경장,타문시강대적대류층고층청장고원반기선고압화강적저층열력강박.모식환득도료여MCS상련적α중척도와선,타능재500 hPa실측풍장중득도반영,이차,모식모의적400 hPa우수혼합비장재일정정도상모의료MCS재Tbb도상반영적β중척도차급결구특정.령일방면,모의존재적차이야시명현적,례여:시간상유3소시체후;모의적MCS α중척도와선위치편서3-5개경도.(2)모의적α중척도기선성와선적결구화연변시고원상탐공자료난우묘술적.모의적결과표명,타지한우고원상재450 hPa이하적대류층중저층,범위향상감소,재500 hPa직경약4개경위도.저개중저층와선대응상승운동구,단타적상방시반기선와도,대응하침운동.해와선시재고원상종무도유발전출래적,출현재MCS성숙계단화지후,지속3-6개소시.재타적형성화소망시도시위세고도장적변화선우풍장적변화,저표명해와선여고원상적열력작용밀절상련.(3)일계렬모식민감성시험고찰료불동적물리과정화고원지표열력강박대고원상MCS적영향.결과표명,문중적고원상MCS재고층청장고원반기선고압적대척도배경하주요수중저층열력강박적지배.저사모의결과암시출일정적고층대척도배경하괄당적저층열력효응취유가능재고원상형성MCS적가능성.
A mesoscale convective system (MCS) developing over the Qinghai-Xizang Plateau on 26 July 1995 issimulated using the fifth version of the Penn State-NCAR nonhydrostatic mesoscale model (MM5). Theresults obtained are inspiring and are as follows. (1) The model simulates well the largescale conditionsin which the MCS concerned is embedded, which are the well-known anticyclonic Qinghai-Xizang PlateauHigh in the upper layers and the strong thermal forcing in the lower layers. In particular, the modelcaptures the meso-α scale cyclonic vortex associated with the MCS, which can be analyzed in the 500 hPaobservational winds; and to some degree, the model reproduces even its meso-β scale substructure similarto satellite images, reflected in the model-simulated 400 hPa rainwater. On the other hand, there aresome distinct deficiencies in the simulation; for example, the simulated MCS occurs with a lag of 3 hoursand a westward deviation of 3-5° longitude. (2) The structure and evolution of the meso-α scale vortexassociated with the MCS are undescribable for upper-air sounding data. The vortex is confined to thelower troposphere under 450 hPa over the plateau and shrinks its extent with height, with a diameter of4° longitude at 500 hPa. It is within the updraft area, but with an upper-level anticyclone and downdraftover it. The vortex originates over the plateau, and does not form until the mature stage of the MCS. Itlasts for 3-6 hours. In its processes of both formation and decay, the change in geopotential height fieldis prior to that in the wind field. It follows that the vortex is closely associated with the thermal effectsover the plateau. (3) A series of sensitivity experiments are conducted to investigate the impact of varioussurface thermal forcings and other physical processes on the MCS over the plateau. The results indicatethat under the background conditions of the upper-level Qinghai-Xizang High, the MCS involved is mainlydominated by the low-level thermal forcing. The simulation described here is a good indication that itmay be possible to reproduce the MCS over the plateau under certain large-scale conditions and with theincorporation of proper thermal physics in the lower layers.