孟加拉湾南部冷池的极端事件及其机理初析

Preliminary analysis on extremes and its mechanismsin the southern Bay of Bengal cold pool

本研究利用多源卫星遥感数据对比分析了2018年和2015年孟加拉湾南部冷池的极端异常事件。孟加拉湾南部冷池早期出现在5月,8月和9月强度达到最大,10月开始减弱,随后逐渐消失。数据显示2018年和2015年冷池海表温度距平值分别为-0.55℃和0.43℃,是1993—2018年26年中冷池降温最强和最弱的年份。2018年孟加拉湾南部冷池风应力距平值为0.02 N/m2,而2015年距平值为-0.01 N/m2。2018年Ekman抽吸速度距平在冷池区域为正,2015年为负。经混合层热收支计算得到,造成冷池产生的主要原因是平流效应,且2018年与2015年的夏季(6—8月)降温平流项分别占49.2%和80.7%。冷池极端事件主要发生在6月,2018年6月冷池降温是2015年的2.76倍,并且海表净热通量项和平流项的异常对冷池极端事件的产生起了重要作用。

Extreme anomalous events in the southern Bay of Bengal cold pool(SBOBCP)in 2018 and 2015 were compared and analyzed based on multi-source satellite remote sensing data.The SBOBCP appeared in May,reached its maximum intensity in August and September,weakened in October,and gradually disappeared.The strongest and weakest SBOBCP years occurred in 2018 and 2015 from 1993 to 2018,with anomalies of-0.55℃and 0.43℃,respectively.The wind stress anomaly in the SBOBCP was 0.02 N/m 2 in 2018,and-0.01 N/m 2 in 2015.The Ekman pumping velocity anomaly was positive in 2018 and negative in 2015.Diagnosis suggested that advection was the main cause of the formation of the cold pool.In summer(6-8),cooling advection accounted for 49.2%and 80.7%in 2018 and 2015,respectively.June was the key period of SBOBCP s formation,and the SBOBCP cooling in June 2018 was 2.76 times of that in 2015.Meanwhile,the anomalies of the net heat flux items and advection items played an important role in the cold pool extreme events.