基于MODIS/EVI时间序列数据分析冰冻灾害对植被绿叶始期的影响

Effects of Freezing Disaster on Green-up Date of the Vegetation Using MODIS/EVI Time Series Data

在全球气候变化的研究中,植被物候与气候的关系是一个重要的课题,它显示陆地生态系统对全球变化的响应。笔者用2005～2008年1～7月每8 d时间序列的MODIS/EVI数据及其相应的地面数据,运用时间序列谐波分析(HANTS)算法对EVI数据进行去云处理。对处理后的结果,采用动态阈值法获取该区域2005～2008年植被物候(生长始期)及其分布格局,并将冰冻灾害年份跟正常年份植被物候分布格局进行对比,分析冰冻灾害对该地区植被物候的影响。结果表明,处理后的EVI数据能较好地反映冰冻灾害对植被物候的影响,准确地反映了冰冻灾害的实际影响范围。该研究结果说明,通过HANTS法分析卫星遥感数据可较为准确地反映植被的生态特征。

In the field of global changes, the relationship between plant phenology and climate, which reflects the response of terrestrial ecosystem to global climate change, has become a key subject that is highly concerned. Using the moderate-resolution imaging spectroradiometer （MODIS）/enhanced vegetation index（EVI） collected every eight days during January-July from 2005 to 2008 and the corresponding remote sensing data as experimental materials, we constructed cloud-free images via the Harmonic analysis of time series （HABITS）. The cloud-free images were then treated by dynamic threshold method for obtaining the vegetation phenology in green up period and its distribution pattern. And the distribution pattern between freezing disaster year and normal year were comparatively analyzed for revealing the effect of freezing disaster on vegetation phenology in experimental plot. The result showed that the treated EVI data performed well in monitoring the effect of freezing disaster on vegetation phenology, accurately reflecting the regions suffered from freezing disaster. This result suggests that processing of remote sensing data using HANTS method could well monitor the ecological characteristics of vegetation.