中国近海局部海域低空大气波导的天气学特征分析

利用大气模式MM5模拟结果统计分析了中国近海低空大气波导的季节分布特征;根据模拟结果与观测数据选取局部海域为研究对象,采用经验正交函数(EOF)分解方法,详细研究了该海域低空大气波导形成的天气学特征.研究发现,当位于冷高压偏南侧、或热带低压的西北侧、或南部高压与北部低压之间时,依次对应着有利于产生低空大气波导的三种主要天气形势;第一种形势(约占41%)下的波导高度较高(约1300～1600m),第二种形势(约占7%)下的波导强度较大(约17M),它们的共同点是辐散下沉形成稳定逆温层且大气低层较强的水汽平流造成较大的水汽垂直梯度;第三种形势(约占4%)下,平流过程是形成大气波导的主要原因.本文研究同时表明,分析某一局部海域大气波导天气学特征时,EOF分解方法是一种极为有效的途径.

Synoptic Features Analysis of Atmospheric Ducts over Chinese Regional Sea

A simulated climatology of atmospheric ducts over Chinese regional seas was produced with the MM5 atmospheric model.An analysis of ducts over a regional sea was studied in detail by using empirical orthogonal function (EOF) decomposition,and find three top weather situations were favorable for duct occurrence.In these situations,the regional sea is located southern to a cold anticyclone,north-western to a tropical low,and between a northern low and a southern high,respectively.In the first situation (accounts for 41%) duct height is relatively high (1300~1600m),and duct strength is much intense (17M) in the second (accounts for 7%).The similarity of these two types is that air divergence and subsidence results in inversion,and strong water vapor advection causes large vertical humidity gradient in lower atmosphere.However,in the third situation (accounts for 4%) advection plays an important role.The result suggests that EOF is an effective approach to study synoptic features of atmospheric ducts over a regional sea.