Investigation of Spatial Representativeness for Surface Flux Measurements in the Heihe River Basin

Abstract

It is very important to determine the land surface fluxes,including sensible heat fluxes and latent heat fluxes,for the issues involving many aspects of climate,agriculture,and water resources management.Nowadays,the Eddy Covariance system(EC) and the Large Aperture Scintillometer(LAS) are the main instruments measuring surface fluxes.The former is point observation and can observe hundreds of meters and the latter can observe area average fluxes in the scale of hundreds of meters to ten kilometers.In order to analyze the source area,we develop Eulerian analytical footprint models for the EC and LAS.Detailed descriptions of the theory basis and methods of the two models are given,and their differences are discussed.Simultaneous remote sensing and ground-based experiment was being carried out in the Heihe River Basin,its observing major components of water cycle were in three experiment areas,i.e.,cold region,forest,and arid region hydrology experiment areas.This paper shows some outcomes of the flux footprint models application in A′Rou freeze/thaw observation station,Yingke irrigated oasis station,Dayekou Guantan forest station and Linze grassland station.The representatinve one day or one month is selected.The analysis of the source area and spatial representativeness of the EC and LAS is given.The difference of observing flux is discussed.In the end,it reveals that reasonable source area of LAS and EC can be derived from their flux footprint models and the footprint model is an effective and practical tool.