Seasonal changes in physical processes controlling evaporation over inland water

Abstract

AbstractWhile previous studies have shown the distinct characteristics of water surface energy fluxes in different seasons, much less analysis is conducted about how seasonal changes in physical processes and environmental variables in the atmospheric surface layer (ASL) cause variations in flux exchange. Here we analyzed and compared eddy covariance fluxes of sensible heat (H) and latent heat (LE) and other microclimate variables that were measured over a large inland water surface in the winter season (January, February, and March) and the summer season (June, July, and August) of 2008. Our analysis was primarily focused on LE using half‐hour time series data on a short‐term basis. Our results show that an increase in wind speeds (U) or vapor pressure difference in the ASL (Δe) or ASL instability did not necessarily cause an increase in LE, and the opposite changes in LE with changes in these variables were observed. Relative regulations of LE by different environmental variables depended largely on Δe magnitudes. Under low Δe conditions, diurnal LE variations were not sensitive to changes in Δe and U but were controlled primarily by changes in the ASL stability. Under high Δe conditions, diurnal LE variations were mainly determined by changes in Δe, though alternate controls by U and Δe were observed, whereas ASL stability played minor roles in affecting LE variations. Whether these highly nonlinear responses of LE to environmental variables are adequately reflected in the bulk transfer relations requires further studies.