Disaggregation of eddy covariance evapotranspiration fluxes from heterogeneous landscapes

Abstract:

Evapotranspiration (ET) is a key variable for the water and energy balance, determines land-atmosphere interactions, and modulates biogeochemical cycles. Evapotranspiration is measured with high accuracy using eddy covariance (EC) systems. A key assumption of EC systems is that ET is from homogeneous source areas. However, in many field conditions, ET fluxes are averaged from heterogeneous or mixed surface types. In this study, we designed a scheme for disaggregating ET fluxes from heterogeneous surfaces into their (homogeneous) components using a combination of EC footprint modeling, MODIS and LANDSAT remote sensing imagery. Using Texas Water Observatory as a test bed, we designed field experiments with multiple EC sensors installed to estimate ET from a mosaic of a heterogeneous surface composed of cotton and pasture land covers. We installed two additional EC systems to separately estimate ET from the cotton and pasture homogeneous source areas within the heterogeneous surface considered and used their ET to evaluate the proposed disaggregation algorithm. Preliminary results show good estimates of ET for each surface type/land cover from the disaggregated ET. This analysis allows the disaggregation of ET from heterogeneous surfaces of any EC footprint.