On estimating surface energy fluxes from single level climatological observations

A number of federal and nonfederal climate observation networks are under development. These observations are invaluable for a variety of applied climatological purposes ranging from agriculture, air pollution, aviation, severe weather analysis, and climate change studies. All these applications can benefit more if information on surface energy fluxes are available. Energy fluxes are important in defining the structure of the atmosphere and in generating local circulations through surface gradients. They also form an important link for the comparison of model results with the observations. Finally, there is an increased awareness of the impact of land - atmosphere interactions and most of the developments relies on special field measurements. However to develop further understanding of these exchanges seasonally and annually, over a large domain there is a definitive need to extract energy fluxes from routine climatological observations. Towards this end, the State Climate Office of North Carolina is developing a procedure for estimating energy fluxes from their surface observation network: AgNet.

In this paper, a recent iterative algorithm based on local and mesoscale roughness concept is applied to estimate surface fluxes of sensible and latent heat using observations from an AgNet site in Raleigh, North Carolina. For the case study, fluxes are estimated from three days of single-level meteorological / climatological data from a meteorological towers in an urban environment in central North Carolina. Penman-Monteith parameterization, along with Monin-Obukhov similarity theory is used for the calculation of the latent heat flux. The resulting flux estimates are related to incoming total radiation and other commonly measured surface variables. In addition, at this particular site, there were two levels of air temperature and hence sensible heat flux estimates could be compared to the estimates from the profile method, based on K-theory. Suggestions are made for further study of this procedure for implementation in a regional scale observational network.