The surface energy budget drives all aspects of the global climate system. Net radiation absorbed at the Earth’s surface is the primary energy source for all other processes inherent in surface-atmosphere interactions. Furthermore, variations in the partitioning of this energy on a large-scale initiate changes in global circulation patterns and synoptic-scale weather systems, while regional variability impacts mesoscale and microscale weather phenomena. There are two primary mechanisms for the atmospheric partitioning of net radiation absorbed at the Earth’s surface: sensible and latent heat flux. Although net radiation is the direct forcing mechanism of this planetary feedback process, spatial and temporal variations in soil moisture generate changes in land-surface heat capacity, albedo, and vegetation that directly impact these fluxes.

The Oklahoma Mesonet is an automated network of 116 remote, meteorological stations across Oklahoma. In addition to providing standard meteorological measurements such as air temperature and humidity, station pressure, and wind speed and direction, 101 sites are equipped with sensors to estimate soil moisture at four depths (5, 25, 60, and 75 cm), while 10 sites are outfitted with sensors to measure the components of the surface energy budget. At each of these 10 sites, designated Oklahoma Atmospheric Surface-layer Instrumentation System (OASIS) Super Sites, a 3-D sonic anemometer and krypton hygrometer provide estimations of sensible and latent heat flux through the eddy correlation technique.

Preliminary results have yielded linear relationships between root-zone soil moisture and latent and sensible heat flux. This study examines three years of data from 2000-2002 across the OASIS Super Sites in Oklahoma and illustrates the linear correlations that exist between soil moisture, latent and sensible heat flux, and evaporative fraction on clear sunny days in which radiative forcing is dominant.