基于MODIS/Aqua的胶州湾及青岛近海叶绿素a浓度年变化特征分析

Analysis on the Annual Change Characteristics of Chlorophyll-a Concentration in the Jiaozhou Bay and Qingdao Coastal Area Based on MODIS/Aqua

利用2002-2013年MODIS/Aqua的Level 1B数据,经标准大气校正算法和叶绿素a浓度[chl-a]波段比经验算法(OC2M-HI),获得近12 a的胶州湾及青岛近海海域晴空的MOIDS/Aqua叶绿素a浓度。根据GOCI/COMS和MODIS/Aqua叶绿素a浓度产品在胶州湾及青岛近海交叉比较的结果[1],对2002-2013年的MODIS/Aqua[chl-a]进行了修正。基于修正后的MODIS/Aqua[chl-a]分析了胶州湾及青岛近海的叶绿素a浓度年变化特征。该海域的叶绿素a浓度大致呈现北高南低,湾内高于近海的特点,且每年空间分布趋势基本一致;近12 a的[chl-a]呈小的上升趋势,胶州湾的上升趋势大于青岛近海。胶州湾跨海大桥建设前,其附近区域叶绿素a浓度以0.47μg/L/year的趋势上升,基值为2.62μg/L;大桥开建及通车后,其附近叶绿素a浓度年变化趋势不明显,但基值明显增大(4.00μg/L)。

Nearly 12-year chlorophyll-a concentrations [chl-a] under cloud-free conditions in the Jiaozhou Bay and Qingdao coastal area were retrieved using MODIS/Aqua Level 1B data from 2002 to 2013 by the standard atmospheric correction algorithm and the default band ratio algorithm for [chl-a]（i.e., OC2M-HI）. The MODIS/Aqua [chl-a] were corrected according to the cross-comparison result of [chl-a] products from GOCI/COMS and MODIS/Aqua in the Jiaozhou Bay and Qingdao coastal area. The corrected MODIS/Aqua [chl-a] were used to analyze the annual change characteristics of [chl-a] in the Jiaozhou Bay and Qingdao coastal area. The results show that the values of [chl-a] in the northern Bay are higher than those in the south, and [chl-a] values in the overall bay are higher than those in coastal waters. Furthermore, the spatial distribution of [chl-a] is basically the same during the 12 years and presents a slight increasing trend, and the trend in the Jiaozhou Bay is greater than that in the Qingdao coastal area. The [chl-a] value had an upward trend of 0.47 μg/L/a with a baseline value of2.62 μg/L before the Jiaozhou Bay Bridge was constructed, while the annual change trend of [chl-a] value kept the same after the bridge was completed with an obvious increscent baseline value of 4.00 μg/L.