Comparison of the differences of sensible heat flux observation methods at different spatial scales in North China Plain

Abstract

Understanding the estimation of sensible heat flux on heterogeneous underlying surface of farmland is of great environmental importance for alleviating ecological pollution and adapting agricultural water management. Data measurements were conducted to evaluate the difference of sensible heat flux under large aperture scintillometer (H-las) and eddy covariance (H-ec) under various underlying surfaces in North China Plain. Four typical periods represented as the crop periods (January, March, May, and August) were selected to investigate the correlation between the H-las and H-ec as well as relative error assessment. Results showed that the H-las and H-ec were consistent on the non-uniform underlying surface as time; the correlation coefficient (R2) were 0.75 in January, 0.65 in March, 0.65 in May, and 0.60 in August, respectively; the coverage of LAS footprints was 45 times that of single-point observations. In the prevailing wind direction, most of the EC source areas were homogeneous farmland, while the LAS source areas also include residential areas and woodland; the H-las was slightly higher than H-ec by 1.61–21.21%, which results from the non-uniformity of underlying surface, the variation of meteorological factors, the inconsistency source areas, and the deviation of EC. The method of LAS is recommended for measuring average sensible heat flux in this study area accordingly.