冬夏两季太湖离水辐亮度贡献的深度廓线分布模拟

Simulation of the Profile Distribution of Water-Leaving Radiation Contribution in Taihu Lake in Winter and Summer

基于冬夏两季太湖50个采样点的散射、吸收系数,在假定水体混合均匀、无非弹性散射及内光源的情况下,利用多次散射模式模拟了冬夏两季太湖离水辐亮度贡献的深度廓线分布及相同离水辐亮度贡献之和情况下的深度分布。结果表明,由于冬夏两季风浪作用及水体中藻类浓度的差异,各层离水辐亮度贡献之和(自表层向下累加)达到99.5%,时在各采样点深度具有明显的不同。夏季梅梁湾和竺山湾最小,湖心开阔区及贡湖湾次之,太湖东南部最大,且在东太湖及西山的部分区域,底质反射的贡献不可忽略;冬季该深度基本均小于水深,无需考虑底质反射,且梅梁湾、竺山湾、西部沿岸、贡湖湾、东太湖及西山附近深度相对较大,但不超过450 mm。夏季影响该深度的因子主要是悬浮颗粒物及叶绿素,而冬季主要是悬浮颗粒物。内陆水体光学特性在空间上的非均匀分布,决定了不同深度处因散射引起的向上辐射对离水辐亮度贡献在空间上的不同,耦合离水辐亮度贡献廓线分布对提高二类水体水质参数的遥感有着重要意义。

Based on the measured scattering and absorption coefficient at fifty points in Taihu lake in winter and summer,the profile distribution of water-leaving radiation contribution and the depth of the same contribution of water-leaving radiation at different point in Taihu lake are simulated by multiple scattering models assurning that the radiation field has no internal light source,no inelastic scattering and the water is uniformly mixed.The results show that,the depth for the sum of water-leaving radiation contribution reaching 99.5%（accumulated downward from the surface） has significant difference in different space on the account of wind wave action and the concentration of phytoplankton in winter and in summer.In summer,the smallest depth is in Meiliang bay and Zhushan bay,followed by the center of the lake and Gonghu bay,in the south-east of Taihu lake the depth is the biggest and the contribution of sediments reflection in east Taihu lake and Xishan hills can not be ignored.In winter,the sediments reflection need to doesn′t be considered since the depth for the sum of water-leaving radiation contribution reaching 99.5% is less than the water depth.In Meiliang Bay,Zhushan Bay,western coast,Gonghu Bay,east Taihu Lake and Xishan Hills the depth is relatively large,but not more than 450 mm.In summer the suspended particulate and chlorophyll are the mainly factors which effected the depth,in winter the mainly factor is suspended particle.The spatial inhomogeneous distribution of the interior water body optical characters determins the spatial difference of the water-leaving radiation contribution which is caused by the upward radiation due to the different depth scattering.Coupling the profile distribution of water-leaving radiation contribution has a great improvement on remote sensing of the quality parameters of water Ⅱ.