滇池蓝藻水华光谱特征、遥感识别及暴发气象条件

通过研究滇池蓝藻水华在可见光、红外谱段的光谱特征,并利用假彩色合成法以及归一化植被指数(NDVI)法进行了滇池蓝藻水华信息的遥感识别和提取,进而对提取结果进行了对比分析.结果表明:假彩色合成图的绿色区域和NDVI值大于-0.1的区域,为蓝藻水华区域.-0.1≤NDVI≤0.2时,轻度水华,像元内水华覆盖度为0-30%;0.2NDVI≤0.4时,中度水华,像元内蓝藻水华覆盖度为31%-80%;NDVI0.4时,重度水华,水华浓厚,像元内蓝藻水华覆盖度为81%-100%.同时研究了激励滇池蓝藻水华暴发的关键气象因子和指标.滇池蓝藻水华暴发的关键时期是6-9月份,影响滇池蓝藻暴发的关键因子是日照和风速.6-9月份连续4-5h的光照,且风速≤2m/s的气象条件组合极易引起蓝藻水华暴发.

Spectral features,remote sensing identification and breaking-out meteorological condi-tions of algal bloom in Lake Dianchi

Based on high spectral reflectivity features of Blue-green Algal Bloom (BAB) in Lake Dianchi, by MODIS satellite re mote sensing data, RGB:621 combined false color synthesis and Normalized Difference Vegetation Index(NDVI)method, we found that green region in false color synthesis image and the region with NDVI value > - 0.1 were just the BAB area. When - 0. 1 ≤ NDVI≤0. 2, slight BAB occurred, and bloom coverage in a pixel reaches 0-30%; when 0.2 0.4,and bloom coverage in a pixel can be 81% -100%. From June to September is the key period for BAB breaking-out in Lake Dianchi, and the key factors to affect BAB breaking-out maybe sunshine and wind velocity. During this period, if the sunshine can last for only 4-5 hours and the wind velocity ≤2m/s, it's quite easy for BAB breaking-out.