根据1996—2002年无锡太湖监测站的水质资料分析,太湖悬浮物具有季节性特征,因而分季节的悬浮物估测模型比单一的模型可能更加适合用来估测太湖全年的悬浮物浓度.在分析太湖水体光谱特征的基础上,根据太湖悬浮物的季节性分布特征,使用春夏秋冬四季的Landsat TM/ETM图像和准同步的水质采样数据,建立了太湖分季节的悬浮物估算模型.结果表明:估测因子(B2+B3)/(B2/B3)在春、秋、冬三季都能很好地估测出悬浮物的浓度(R^2〉0.52).夏季由于叶绿素的干扰性较大,悬浮物的估测效果不理想.冬季的估测效果最好(R^2=0.81),模型为lnSS:14.656×(B2+B3)/(B2/B3)+1.661,其中,lnSS表示悬浮物取自然对数后的值,B2、B3为TM/ETM图像经过6S大气校正、3×3低通滤波后第2、3波段的反射率值.
Suspended sediment in Lake Taihu has its seasonal character according to the analysis of in situ data acquired by Taihu Monitoring Wuxi Station during 1996-2002, so seasonal models may better than a single model for estimating suspended sediment in Lake Taihu. After analyzing the spectral characteristic of Lake Taihu, seasonal suspended sediment estimating models were built based on four Landsat TM/ETM images, respectively in spring, summer, autumn and winter, as well as synchronous in situ data. Result shows that (B2 +B3)/(B2/B3) is a good index for estimating suspended sediment in Spring, Autumn and Winter (R^2 〉 0. 52). The summer model is not sound due to the disturbance of high chlorophyll concentration, as alga boom in summer. The winter model has the best effect in estimating suspended sediment ( R^2 = 0. 81 ). The Winter model is lnSS = 14. 656× ( B2 + B3 )/( B2/B3 ) + 1. 661, in which lnSS is the natural logarithm of suspended sediment concentration, B2 and B3 are the reflectance in Band 2 and B3 of the Landsat TM/ETM images after 6S atmospheric correction and a 3 ×3 low-pass filtering.