气溶胶光学厚度对蓝藻水华信息提取的影响

Effects of aerosol optical thickness on extracting cyanbacteria bloom

通过探讨气溶胶光学厚度(AOT)对蓝藻水华信息提取的影响程度和消除方法,为蓝藻水华的动态监测提供可靠依据。首先,利用MODIS数据产品(MOD 02,MOD 04和MOD 09),基于单波段和比值植被指数2种方法分别提取了2006年太湖蓝藻水华的空间分布信息,探讨了AOT对信息提取阈值选择的影响方式和影响程度。研究结果表明:在固定阈值情况下,采用上述2种方法提取的蓝藻水华信息面积差异与AOT的相关性高于自选阈值情况下的相关性;在单波段法和比值植被指数法中,大气校正前所设定的阈值与AOT的相关性都高于大气校正后再选择阈值的相关性。这反映出AOT对蓝藻水华信息提取的影响是不容忽视的,即便不能完全消除,也要选择适当的方法尽量降低其影响程度。

In this paper, the effect of Aerosol Optical Thickness （AOT） on cyanbacteria bloom in the Taihu lake was investigated, which could lay a foundation for dynamically monitoring cyanbacteria bloom. Moreover, a study of the elimination of the effects of AOT on the extraction results was carried out. MODIS products （ MOD 02, MOD 04 and MOD 09 ） were chosen. Single band （NIR） and ratio vegetation index （NIR/G） were used to extract the spatial distribution of cyanbacteria bloom in the Taihu Lake in 2006. The effect of AOT was explored. A quantitative analysis of the degree of the effect of AOT on both the net changes of the area of cyanbacteria bloom and threshold selection was conducted. The results show that the correlation in the case of fixed threshold is higher than that of the demand threshold when the correlation of the area differences of cyanbacteria bloom and AOT is studied with single band and ratio vegetation index. In these two methods, the correlation without atmospheric correction is higher than that with atmospheric correction in the case of the corresponding value. This shows that the atmosphere will have some impact on the extraction of cyanbacteria bloom. Therefore, if cyanbacteria bloom information needs to be extracted accurately and reliably, AOT cannot be ignored. Also, if it cannot be completely eliminated, appropriate methods could be used to minimize its effect.