西藏中部“一江两河”地区地表通量的卫星遥感估算

Land Surface Heat Fluxes in the Middle Reaches of Yarlung Zangbo River and Its Two Tributaries Derived from AVHRR and MODIS Data

西藏中部一江两河地区(包括雅鲁藏布江中游和拉萨河、年楚河中下游地区)是西藏主要的农业区,藏中农业区地表特征参数(地表反照率、地表温度和植被指数)的变化和地表通量的遥感估算对农作物长势监测、农作物估产、灾害监测以及理解农业区内部乃至其与周边地区的能量水循环研究具有重要的意义.选取2003年4月14日和10月16日影像作为春季和秋季代表,利用两种相同空间分辨率的卫星资料———AVHRR和MODIS反演研究区地表特征参数和地表通量.在反演得到地表特征参数的基础上,结合研究区9个台站的地面气象观测资料,利用SEBS模式对该地区地表通量进行了遥感估算.结果表明,研究区地表能量平衡各分量具有明显的空间分布和时间变化特征.同一天中AVHRR和MODIS估算结果空间分布态势保持一致,但由于过境时间的差异,MODIS通量结果均大于AVHRR.

The middle reaches of Yarlung Zangbo River and its two tributaries（including lower reaches of Lhasa River and Nianchu River） is a region in central Tibet Autonomous Region,where the agricultural economy is most concentrative and developed.Remote sensing of land surface characteristic parameters（albedo,land surface temperature,NDVI） and land surface heat fluxes have significant meaning for crop growth monitoring,crop yield assessment,disaster monitoring and understanding energy and water cycle in local area and even for surrounding regions.In this paper,AVHRR-16 L1B data and MODIS L1B data,which have the same spatial resolution,are applied to retrieve land surface characteristic parameters and land surface heat fluxes,respectively.The satellite images taken on 14 April and 16 October,2003 are selected as representative cases for spring and autumn.Based on the land surface characteristic parameters derived from satellite images and meteorological data from nine meteorological stations in the study area,the land surface heat fluxes were estimated by applying Surface Energy Balance System（SEBS）.Results show that the energy balance components have clear spatial distribution and temporal variation.By comparing the estimation results from these two different satellites,it is found that the heat fluxes have the same spatial distribution trends in general.However,because of the different satellite passing time,the heat flux values from MODIS are larger than those from AVHRR.