2004年冬季风期间一次强寒潮过程的能量收支研究1

Energy Budget of a Cold Surge Process during the Winter Monsoon Period of 2004

利用1°(纬度)×1°(经度)的NCEP再分析资料和常规站点观测资料对2004年12月28～31日的一次强寒潮、冷涌过程作了研究,研究结果表明:(1)此次强寒潮事件在我国南海引发了强烈的冷涌,该支冷涌一直向南越过赤道影响南半球。大尺度环境场有利于此次寒潮、冷涌事件的爆发,本次寒潮属于"横槽转竖型",其中200hPa的西风带大槽经历了一次调整,500hPa经历了一次明显的横槽转竖过程,对流层低层蒙古高压稳定维持,其东侧的偏北大风是冷空气南下的有利条件。(2)此次寒潮大风区内的动能制造以正压动能制造和斜压动能制造为主,寒潮爆发初期,以正压制造过程为主,此后,由于有效位能释放的作用增强,斜压制造过程与正压制造强度相当,大风区随着动能制造的增强而增强;当斜压、正压动能制造均减弱,大风区亦随之减弱。(3)有效位能收支表明,整层有效位能的释放与大风区相对应,有效位能的释放有利于寒潮、冷涌的维持。寒潮大风区内,对流层高层受有效位能释放的影响最大,有效位能和风能可以互相转换;对流层中层所受的影响最小,且以风能向有效位能转换为主;对流层低层则以有效位能向动能转化为主,十分有利于低层风速的增大和维持。

Based on 6-hour reanalysis data with 1° × 1°esolution from NCEP and station observed data, a cold surge during 28-31 Dec 2004 was analyzed, showing the following results： （1） During this period, the cold surge moved southward, crossed the equator and influenced the weather of the southern hemisphere. The background circulation was favorable for the breakout of the cold surge： A combination of two troughs in the westerly at 200 hPa and a transversal trough that transformed to a normal one at 500 hPa, which categorized this cold surge as a ＂transversal trough＂ type. The Mongolia high remained quasi-stationary, and the strong north wind to the east of it was favorable for the cold surge breakout. （2） The kinetic budget shows that the barotropic kinetic genesis （BTG） and baroclinic kinetic genesis （BCG） are the most important terms of the kinetic budget equation. Initially, the BTG term was dominant; later, the influence of the BCG term increased to equal that of the BTG. After 31 Dec, the kinetic genesis and strong wind zone both decreased obviously. （3） The available potential energy （APE） budget indicates a good correlation between the release of APE and the wind at 850 hPa. The release of APE was favorable for the wind increase at low tropospheric levels and influenced mostly the high levels while having only a slight influence on the middle levels of the troposphere.