基于MODIS数据的安徽区域日蒸散量估算与分析

ESTIMATION AND ANALYSIS OF EVAPOTRANSPIRATION IN ANHUI PROVINCE WITH MODIS DATA

蒸散的估算在区域能量平衡和水资源研究中具有重要意义,遥感技术发展促进了区域蒸散的研究。利用安徽省气象资料、MODIS数据产品及GIS背景信息,基于SEBAL模型,按1km空间分辨率进行了面尺度的安徽省日蒸散量估算,并在GIS空间分析模块的支持下对不同土地覆盖类型的日蒸散量进行统计分析。结果表明:遥感估算的蒸散量与利用Penman-Monteith公式计算的蒸散量比较,两者之间具有较好的相关性,遥感蒸散估算值整体偏小,不同土地利用类型的日蒸散量间差异显著。遥感蒸散估算方法在安徽省具有一定的实用性,需优化模型参数,以提高其进一步技术推广的前景。

Evapotranspiration (ET) is a critical component of the land surface energy balance system and hydrologic processes.Analysis of spatiotemporal variations and influencing factors of ET is of great importance to evaluate the growing environment for crops and to effectively use water resources in Anhui Province.The traditional methods are based on point measurement,while remote sensing provides extensive surface information.The development of remote sensing has promoted the study of regional ET.SEBAL model is based on Surface Energy Balance Algorithm for Land and its physical meaning is clear.This model was developed to show the spatial variability of surface evapotranspiration.SEBAL model was applicable to large areas in conjunction with Moderate-resolution Imaging Spectroradiometer (MODIS) data products (i.e.,MOD11A1,MOD11A2,MOD13A2,MOD43B3,and MCD43B3).According to the shortcomings of the traditional method of calculating ET,based on SEBAL model,the daily regional evapotranspiration of Anhui Province was estimated with 1 km spatial resolution by using MODIS products and meteorological data (including temperature and wind speed) collected in meteorological stations distributed across the study area.Firstly,the estimation results of March 26th and August 5th,2010 were taken as examples in the analysis of daily ET characteristics of different land covers in the study area by using the spatial analysis module of GIS.Secondly,based on meteorological data of March 26 th,2010 and August 5 th,including daily temperature,relative humidity,sunshine hours and wind speed of 80 meteorological stations in Anhui province,crop reference evapotranspiration (ET0) was calculated by using the Penman-Monteith (P-M) formula,which was nominated by FAO in 1998 and Kriging method.Because of lacking observed data from the lysimeter,the results of P-M were compared with the estimation results based on SEBAL model in this research.The comparison of the evapotranspiration estimated with MODIS products and field observation showed that the former results were lower than the latter results on the whole,and demonstrated that there existed a certain correlation between the two results,the average relative error was different at different land surfaces.The average relative error was below 20％.It was concluded that evapotranspiration of water body was high,which was 3.6 mm.It was followed by paddy field,which was 2.0 mm.Evapotranspiration of dry lands was the lowest,which was only about 1.65 mm.The ET computation method based on Remote Sensing proves that this model has strong practicality in Anhui Province,and it will show great potential in this field with better optimizing the model parameters.