A remote-sensing-based study on evapotranspiration and the environmental factors over the Lake Poyang region

Abstract

蒸散是湖泊湿地生态系统水循环的重要组成部分,研究湖区地表蒸散量的时空变化对了解鄱阳湖湖区水量平衡关系具有重要意义.本研究基于MODIS数据,应用地面温度-植被指数三角关系法反演2000-2009年鄱阳湖湖区的实际蒸散量,分析湖区蒸散的时空分布特征及主要气象因子对流域蒸散的影响.结果表明:2000-2009年鄱阳湖湖区年蒸散量在685~921 mm之间,平均年蒸散量为797 mm,最大蒸散量出现在2004年.2000-2009年多年平均水体蒸发量为1107 mm,高于湖区植被蒸散量(774 mm).湖区汇水区域中蒸散量占降水的平均比例为55%,是水量平衡的主要支出项,径流系数约为0.45.湖区蒸散主要受辐射和气温的影响,月蒸散量与气温呈显著的指数相关,2007年蒸散量对温度的关系最为敏感.降水量距平与蒸散量距平的关系除2007年呈显著负相关外,其他年份相关性不显著.鄱阳湖湿地蒸散与湖泊水域面积总体呈正相关,但在水文干旱严重的2006年,当水域面积<30%时,蒸散速率随水域面积增加而减小.;Evapotranspiration (ET) from the land surface is a crucial component of water and energy balance.In the hydrologic balance,evapotranspiration determines the amount of precipitation resulting in runoff.To understand the process of water balance in the Lake Poyang region,it is necessary to clarify the temporal variation of ET and response of impact factors.In this study, based on MODIS products data,the ET over the Lake Poyang region was estimated using surface temperature-vegetation index triangle method during 2000-2009.The results showed that the annual average ET was 797 mm during 2000-2009,ranging from 685 to 921 mm,the highest ET occurred in 2004.The annual ET of water body was 1107 mm,which was higher than that of land surface over the Lake Poyang region.The ET was a dominant component in water balance,and the percentage of annual ET to precipitation was 55% on average for land surface of the Lake Poyang region.The ET of the Lake Poyang region was mainly affected by radiation and air temperature,monthly ET and air temperature showed significant exponential relationship,the ET in 2007 was more sensitive to air temperature than those in other years.The ET departure indicated significantly negative to precipitation departure in 2007,and there was no obviously relationship in other years.The ET of Lake Poyang wetland showed positive to water surface area, however,when water surface area was less than 30% in severe hydrological drought year,the ET was deceasing with water surface area increased.