基于MODIS的长江口表层水体盐度时空分异

doi:10.13278/j.cnki.jjuese.20180212

摘要/Abstract

摘要： 长江河口地处海陆交汇地区，其海表盐度受到长江流域、东海和三角洲社会经济活动的复合影响。水体盐度直观反映了河口区域冲淡水分布，对于研究淡水羽状锋、长江物质输送与河口环境变化等具有重要意义。本文分别对枯季和洪季的长江口盐度实测数据，以及中分辨率成像光谱仪（moderate-resolution imaging spectroradiometer，MODIS）遥感反射率与反射率的比值进行拟合回归分析，建立长江口表层盐度反演经验模型，得到枯季的相关系数和均方根误差（root-mean-square error，RMSE）分别为-0.930 3、0.45‰，洪季的相关系数和RMSE分别为-0.818 5、0.88‰；并分析模型在时间尺度上的适用性。利用该盐度反演模型对长江口2007-2016年的表层盐度进行反演，结合大通站记录的长江径流量观测资料，分析长江口表层水体盐度的时空变化规律。结果表明：长江口表层盐度受径流量影响较大，空间上呈自西向东递增趋势，具有季节性分异；枯季近岸盐度较高，高盐度海水可以到达长江口南北支分叉122.5°E附近；洪季冲淡水影响范围广，高盐度海水聚集在123°E以东、31°N以南，长江口北部出现低盐区域；2007-2016年间枯季大通站流量呈上升趋势，平均盐度为29.27‰，总体呈降低趋势，洪季大通站流量呈降低趋势，平均盐度为27.10‰，呈上升趋势，盐度和径流量在年际变化中存在良好的负相关关系。

关键词: MODIS, 长江口, 海表盐度, 径流, 时空分异

Abstract: The Yangtze Estuary is located in the intersection of sea and land, and its sea surface salinity (SSS) is affected by the Yangtze River, East China Sea, and social and economic activities of the delta. Salinity can directly reflect the distribution of freshwater plumes;therefore, the research on the spatial and temporal distribution and variation of the Yangtze River salinity is significant for understanding the importance of freshwater plumes, material transport,and estuarine environment. Terra MODIS (moderate-resolution imaging spectroradiometer) remote sensing reflectance, reflectance ratio and field data in dry and flood seasons were used to establish the experienced retrieval models of the Yangtze Estuary, and their RMSE are 0.45‰ and 0.88‰ respectively. The applicability of the model in time scale was also analyzed. The models were used to retrieve SSS in the Yangtze estuarine waters from 2007 to 2016, combined with the runoff observational data from the Datong gauging station, the temporal and spatial variations of SSS were analyzed. The results showed that the SSS distribution in the Yangtze Estuary appeared increasing from the west to the east, which was deeply influenced by the Yangtze River runoff with obvious seasonal differentiation. The off-shore SSS appeared high in the dry season, with high SSS waters reaching westward 123°E, around the bifurcation of the southern and the northern branches of the Yangtze Estuary. Diluted water influenced a larger area in the flood season, which caused the high SSS waters gathering east of 123°E and south of 31°N, along with a low SSS area in the north of the Yangtze Estuary. The Datong gauging station runoff increased during 2007 to 2016 in the flood season, along with the decrease of the average SSS of the study area, and the average SSS was 29.27‰. The runoff decreased in the dry season, along with the increase of the average SSS, and the average SSS was 27.10‰. The SSS variations during 2007 to 2016 had a negative correlation with runoff.

Key words: MODIS (moderate-resolution imaging spectroradiometer), Yangtze Estuary, sea surface salinity, runoff, spatio-temporal differentiation

中图分类号:

TP79

牛莹, 赵欣怡, 周云轩, 田波, 王利花. 基于MODIS的长江口表层水体盐度时空分异[J]. 吉林大学学报(地球科学版), 2019, 49(5): 1486-1495.

Niu Ying, Zhao Xinyi, Zhou Yunxuan, Tian Bo, Wang Lihua. Sea Surface Salinity Spatio-Temporal Differentiation in Yangtze Estuarine Waters Using MODIS[J]. Journal of Jilin University(Earth Science Edition), 2019, 49(5): 1486-1495.

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