An air-soil layer coupled scheme for computing surface heat fluxes

An air-soil layer coupled scheme is developed to compute surface fluxes of sensible heat and latent heat from data collected at the Oklahoma Atmospher ic Radiation Measurement-Cloud and Radiation Testbed (ARM-CART) stations. T his new scheme extends the previous variational method of Xu and Qiu in two aspects: 1) it uses observed standard deviations of wind and temperature t ogether with their similarity laws to estimate the effective roughness leng th, so the computed fluxes are nonlocal; that is, they contain the contribu tions of large eddy motions over a nonlocal area of O(100 km(2)); and 2) it couples the atmospheric layer with the soil-vegetation layer and uses soil data together with the atmospheric measurements (even at a single level), so the computed fluxes are much less sensitive to measurement errors than t hose computed by the previous variational method. Surface skin temperature and effective roughness length are also retrieved as by-products by the new method.