黄海绿潮分布年际变化特征分析

摘要

From 2008 to 2015,large-scale floating Green Tides have consecutively occurred in the Yellow Sea of China,which have great impacts on the marine environment and economic.Based on the EOS/MODIS remote sensing ocean color data,the NDVI algorithm was adopted to inverse the distribution of Green Tides during May to August.The Green Tides were firstly found from MODIS images in 2007 with the coverage area less than 50 km2 in the Yellow Sea.Seasonally,the Green Tides first appeared during the middle of May to early June,then its coverage grew rapidly and continuously and reached a peak in 30 -40 days.In July,the Green Tides depleted gradually and disappeared in August.The maximum coverage areas of the Green Tides were 3 110 km2 and 4 075 km2 in 2008 and 2009 respectively.The Green Tides coverages were in low phase from 2010 to 2012 and the peak areas in these past three years were less than 1 800 km2 .Since 2013,the scales of Green Tides increased rapidly, and the peak coverage reached 5 629 km2 in 2015.(The Green Tides covered the regions ranged from 124°E in the east,Lianyungang of Jiangsu Province in the west,Rudong of Jiangsu Province in the south and 37°N in the north).The trajectories of the Green Tides could be divided into three categories:(a)moved northward to 34°30′N,then turned to northwest toward the coast in 2008,2010 and 2011;(b)moved northward to 35°N,then drifted northeast parallel to the coast in 2009 and 2012;(c)moved northward to the coast of Shandong province,then turned along the coast in 2013,2014 and 2015.%2008—2015年，连续8年在黄海海域暴发大规模绿潮，但因暴发时间、规模及漂移路径的不同，对沿海地区造成的环境影响和经济损失大不相同。本文利用 EOS／MODIS 卫星的多通道资料，采用 NDVI算法获取绿潮信息，给出了2007年以来5—8月所有无云或少云晴朗天气下黄海海面绿潮的分布情况。黄海绿潮覆盖面积变化每年呈现单峰值分布，MODIS 卫星在5月中旬至6月初首次发现绿潮，随后30～40 d 内达到覆盖面积峰值，7月快速消退，8月上旬完全消失。2007年绿潮出现首年覆盖面积极低，发现绿潮时面积均未超过50 km2；2008年和2009年绿潮覆盖面积峰值分别为3110 km2和4075 km2，自此绿潮灾害成为新的海洋环境事件；2010—2012年绿潮暴发规模异常低值，各年覆盖面积峰值均未超过1800 km2，但从2013年开始绿潮规模逐渐攀升，到2015年绿潮覆盖面积峰值达5629 km2，持续可达98 d，覆盖面积和持续时间为历年之最。绿潮漂移路径可归纳分为3类：2008年和2011年绿潮主体先北向漂移越过34°30′N 后，西北向垂直于岸线漂移，主要对连云港、日照和青岛造成较大影响；2009年和2012年绿潮主体先北向漂移越过35°N 后，东北向平行于岸线漂移，故只有少许绿潮上岸；2010年、2013—2015年绿潮主体北向漂移至近岸后东北向沿岸漂移，对日照、青岛和荣成沿海造成大面积影响。所有年份绿潮影响范围均限于南黄海内，东侧边界最远未越过124．2°E。