不确定性因素对太湖藻华信息提取的影响

Effects of Uncertainty Factors on Extraction of Cyanobacteria Blooms

研究3个不确定因素:气溶胶的光学厚度、太阳高度角和卫星观测角对太湖藻华信息提取的影响.结果表明,气溶胶的光学厚度和太阳高度角与大气校正前后藻华提取结果的差异呈正相关,而卫星观测角对藻华信息提取结果的影响最小.对于归一化植被指数法(NDVI),大气校正前气溶胶光学厚度和太阳高度角对阈值选取的影响较大,相关系数为0.42,而大气校正后的相关系数降低到0.34;大气校正前后气溶胶光学厚度、太阳高度角与阈值均呈负相关.对于归一化水体指数法(NDWI),不论大气校正前后,气溶胶光学厚度与太阳高度角对阈值的影响均较NDVI时大,相关系数分别为0.57和0.46,该方法中大气校正前后气溶胶光学厚度与阈值也呈负相关,且NDWI中相关趋势与NDVI中的趋势相反.

Effects of Aerosol optical thickness,solar zenith angle and satellite viewing angle on cyanobacteria blooms were explored.The results indicate that both aerosol optical thickness and solar zenith angle are positively correlated with the difference between extraction results of cyanobacteria blooms before and after the atmospheric correction while the effect of satellite viewing angle on extraction results of cyanobacteria blooms is not significant.With NDVI（Normalized Difference Vegetation Index）,the comprehensive effects of aerosol optical thickness and solar zenith angle on the selection of threshold before the atmospheric correction is greater and the correlation coefficients between the two factors and the threshold is 0.42,while it reduces to 0.34 after the atmospheric correction.Both aerosol optical thickness and solar zenith angle before and after the atmospheric correction are negatively correlated with the threshold.With NDWI（Normal Difference Water Index）,the comprehensive effects of aerosol optical thickness and solar zenith angle on the selection of threshold before and after the atmosphere correction obviously are greater than that with DNVI and the correlation coefficients between the two factors and the threshold are 0.57 and 0.46,respectively.Both aerosol optical thickness and solar zenith angle before and after the atmospheric correction are negatively correlated with the threshold.The relevant trend of the two factors and the threshold with NDVI and that with NDWI are opposite.