Observations of Land-Atmosphere Interactions at a U.S. Southern Great Plains Site

This study examines observational aspects of land-atmosphere interaction during warm seasons of the years 1997 to 2008 at the Department of Energy Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) Central Facility site near Lamont, Oklahoma.

Characteristics of the local land-atmosphere coupling are inferred by analyzing the covariation of selected surface and atmospheric variables. For both the energetic and hydrological aspects of this coupling, it is found that atmospheric forcings generally predominate, with comparatively weak feedbacks of the land on the atmosphere occurring much of the time.

The diminished land feedbacks are manifested, in particular, by 1) the inability of soil moisture to comprehensively impact the coupled land-atmosphere energetics, and 2) the limited recycling of local precipitation under synoptic conditions where most of the rainfall derives from remotely triggered convective cells. However, a relative strengthening of local land feedbacks is observed to occur with the initial drying of the soil in the aftermath of precipitation events, or on days when shallow cumulus clouds (indicative of moist thermal updrafts driven by surface sensible heating) are present in the atmospheric boundary layer.

Acknowledgments: This work was funded by the U.S. Department of Energy and was performed at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.