Estimating surface fluxes over middle and upper streams of the Heihe River Basin with ASTER imagery

Abstract

Abstract. Land surface heat fluxes are essential measures of the strengths of land-atmosphere interactions involving energy, heat and water. Correct parameterization of these fluxes in climate models is critical. Despite their importance, stateof-the-art observation techniques cannot provide representative areal averages of these fluxes comparable to the model grid. Alternative methods of estimation are thus required. These alternative approaches use (satellite) observables of the land surface conditions. In this study, the Surface Energy Balance System (SEBS) algorithm was evaluated in a cold and arid environment, using land surface parameters derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Field observations and estimates from SEBS were compared in terms of net radiation flux (R n ), soil heat flux (G 0 ), sensible heat flux (H ) and latent heat flux (λE) over a heterogeneous land surface. As a case study, this methodology was applied to the experimental area of the Watershed Allied Telemetry Experimental Research (WATER) project, located on the mid-to-upstream sections of the Heihe River in northwest China. ASTER data acquired between 3 May and 4 June 2008, under clearsky conditions were used to determine the surface fluxes. Ground-based measurements of land surface heat fluxes were compared with values derived from the ASTER data. The results show that the derived surface variables and the land surface heat fluxes furnished by SEBS in different months over the study area are in good agreement with the observed Correspondence to: W. Ma (wqma@lzb.ac.cn) land surface status under the limited cases (some cases looks poor results). So SEBS can be used to estimate turbulent heat fluxes with acceptable accuracy in areas where there is partial vegetation cover in exceptive conditions. It is very important to perform calculations using ground-based observational data for parameterization in SEBS in the future. Nevertheless, the remote-sensing results can provide improved explanations of land surface fluxes over varying land coverage at greater spatial scales.

Improving Estimation of Evapotranspiration under Water-Limited Conditions Based on SEBS and MODIS Data in Arid Regions

“…Consistent with earlier studies [27,31,33], the original SEBS clearly underestimated H (Figure 4a), particularly for low values of the NDWI; therefore, a shortage of soil water and a lack of vegetation cover were present. Underestimation of H leads to an overestimation of λE (Figure 4c).…”

Intercomparison of four remote-sensing-based energy balance methods to retrieve surface evapotranspiration and water stress of irrigated fields in semi-arid climate

“…But in most cases, those studies lack the temporal representativeness of a surface evolution during a full growing season (Choi et al, 2009;French et al, 2005;Gonzalez-Dugo et al, 2009;van der Kwast et al, 2009;Li et al, 2005Li et al, , 2008Long and Singh, 2012;Ma et al, 2011;McCabe and Wood, 2006;Minacapilli et al, 2009;Su et al, 2005Su et al, , 2007. A nonexhaustive list of validation and intercomparison studies of surface energy budget (SEB) models is shown in Table 1.…”

Assessment of spatial and temporal patterns of green and blue water flows under natural conditions in inland river basins in Northwest China

“…The Heihe river basin is a typical arid and semi-arid region, suffering from a serious water crisis . Water use in mid-stream regions has increased sharply in the Heihe river basin related to socio-economic development (Ma et al, 2011). As a consequence, the Heihe river basin has been confronted with serious ecosystem degradation including the complete dry-up of the downstream West and East Juyanhai lakes (Cheng, 2002).…”