孟加拉湾北部逆温现象的观测特征及机制分析

摘要

在冬季,孟加拉湾北部存在显著的季节性逆温现象.利用Argo浮标和锚碇浮标资料,分析了冬季孟加拉湾逆温现象的观测特征和维持机制.结果表明,系统性的逆温现象主要局限于15°N以北的区域,它最早于11月份出现在恒河、伊洛瓦底江和戈达瓦里河的河口区域.逆温的强度及分布区域在1月份达到最大,随后从西南部逐步退化,3月逆温现象基本消失.冬季的逆温层位于障碍层之中,厚度在35 m左右,最大海温位于40～ 60m深度,整层满足静力稳定条件.对混合层温度和盐度的诊断表明,逆温的出现主要与冬季风导致的强烈海表热量损失有关,低盐水的平流过程也对逆温现象有一定的维持作用.%Temperature inversion (TI) is a seasonal feature in the northern Bay of Bengal during winter.Based on in situ observation from Argo and RAMA buoy,general characteristics and maintenance mechanism are analyzed in the present study.During winter,TI is mostly confined in the northern bay north of 15°N,and it firstly occurs in the estuaries of Ganges,Godavari and Irrawaddy in November.Generally,the intensity and coverage of TI get strongest in January and TI completely disappears in early March.The inversion layer is static stable as the stability loss by temperature is compensated by the salinity gain in the halocline.The thickness of inversion layer is about 35 m and the maximum temperature is found at the depth around 40 to 60 m.Diagnosis indicates the occurrence of TI primarily depends on the sharp surface heat loss induced by the winter monsoon,and the horizontal salinity advection helps the maintenance of the TI.