Estimating Monthly Energy Fluxes Using Observations of Near-Surface Air Temperature, Humidity and Radiosonde Profiles

A new boundary-layer method is proposed to estimate sensible and latent heat fluxes on a monthly scale, based on hourly surface observations of temperature and specific humidity, as well as their vertical profile in the morning. It assumes that advective effects may be neglected over such a time scale, so that temporal tendencies of temperature and specific humidity are controlled solely by the vertical flux convergence over the mixed layer. The growth of the mixed layer in the model is driven by the sensible heat flux and opposed by the mean thermal stratification observed by upper-air soundings over that month. The method is tested for three sites, where the flux estimates are compared to eddy-covariance observations. No filtering of days based on synoptic condition, cloudiness or other external conditions is applied, providing realistic monthly estimates. In the three cases, the flux estimates approach closely the eddy-covariance observations, indicating that the method may be applied to estimate the fluxes at places where only weather station data are available.