1974—2020年珠江口外海海洋热浪变化趋势分析

Trend analysis of marine heatwaves variability in the outer Pearl River estuary from 1974 to 2020

基于珠江口大万山海洋站(21°56′N,113°43′E)观测的1974—2020年逐日平均海表温度(sea surface temperature,SST)资料,参照世界气象组织关于海洋热浪(marine heatwave,MHW)定义、强度分类标准及全球与北半球年平均表面温度资料,采用相关及对比方法,分析珠江口海洋热浪的变化趋势,结果表明:(1)近47年来珠江口每年都出现MHW事件,平均每年出现6.5次,最多年13次(2020年),且每年出现次数呈上升趋势,平均每次持续时间为11.7d,最长62d;(2)近47年来每年珠江口的MHW日数呈显著增加趋势,上升率为1.81d·a^(–1);(3)此时期各级MHW强度的出现日数占总出现日数的比例分别为中度18.92%,强烈53.24%,严重24.06%,极端3.77%;(4)珠江口MHW日数上升及出现极端MHW的主要原因可能与全球气候变暖、南海高压增强和季风减弱有关。预估未来珠江口的MHW日数还会呈现上升趋势。

Based on the daily mean sea surface temperature(SST) data observed at the Dawanshan Marine Environmental Monitoring Station(DMEMS) in the Pearl River Estuary from 1974 to 2020, the definition of marine heatwaves(MHW)adopted by the World Meteorological Organization, the intensity classification criteria, and the global and northern hemisphere annual mean surface temperature anomaly data, the trends of MHW in the Pearl River Estuary are analyzed using correlation and comparison methods. The results show that: 1) MHW incidents have occurred annually in the Pearl River Estuary in the past 47 years, with an average of 6.5 times per year and up to 13 times in 2020. There is an upward trend in the number of occurrences every year. The average duration is 11.7 days, up to 62 days. 2) MHW days in the Pearl River Estuary have increased significantly in the past 47 years, with an increasing rate of 1.81 d·a^(-1)–1. 3) During this period, the proportion of MHW days with each level of intensity to all days is: moderate 18.92%, strong 53.24%, severe 24.06% and extreme 3.77%. 4) The main reasons for the increase of MHW days and the occurrence of extreme MHW in the Pearl River Estuary might be global warming, enhanced high pressure and weakened monsoon in the South China Sea. It is estimated that the MHW days in the Pearl River Estuary will increase in the future.