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Title: AN EMPIRICAL INVESTIGATION OF CONVECTIVE PLANETARY BOUNDARY LAYER EVOLUTION AND ITS RELATIONSHIP WITH THE LAND SURFACE.

Author
item SANTANELLO, J - DEPT. OF GEOGRAPHY
item FRIEDL, M - DEPT. OF GEOGRAPHY
item Kustas, William - Bill

Submitted to: Journal of Applied Meterology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2005
Publication Date: 6/2/2005
Citation: Santanello, J.A., Friedl, M.A., Kustas, W.P. 2005. An empirical investigation of convective planetary boundary layer evolution and its relationship with the land surface. Journal of Applied Meteorology. 44:917-932.

Interpretive Summary: During the course of the day, the effects of the Earth's surface radiation and energy balances are felt throughout the lower atmosphere. Turbulence and convection act to transport and mix heat and moisture within a region of the lower troposphere of variable depth known as the planetary boundary layer (PBL). One question yet to be resolved in studies of these interactions is how conditions and fluxes at the land surface can be diagnosed using observations of the PBL and its diurnal evolution. The need for this type of approach has become evident in light of the many challenges involved in measuring PBL energy budgets and modeling land-atmosphere interactions via soil-vegetation-atmosphere-transfer schemes. Relationships among PBL evolution and land surface properties are explored using data from the Southern Great Plains. Using balloon soundings and surface flux data for June, July, and August of 1997, 1999, and 2001 a conservation approach was applied to 132 sets of daily observations. Results highlight the limitations of using this method on daily time scales due to the diurnal variability and complexity of entrainment. A statistical investigation of relationships among PBL and both land-surface and near-surface properties that are not explicitly included in conservation methods indicates that atmospheric stability in the layer of PBL growth is the most influential variable controlling PBL development. Significant relationships between PBL height and soil moisture, 2m-potential temperature, and 2m-specific humidity are also identified through this analysis and revealed that 76 percent of the variance in PBL height can be explained by observations of stability and soil water content. Using this approach, it is also possible to use limited observations of the PBL to estimate soil moisture on daily timescales without the need for detailed land surface parameterizations. In the future, the general framework presented may provide a means for robust estimation of near-surface soil moisture and land surface energy balance over regional scales.

Technical Abstract: Relationships among convective planetary boundary layer (PBL) evolution and land surface properties are explored using data from the Atmospheric Radiation Measurement Cloud and Radiation Test Bed in the Southern Great Plains. Previous attempts to infer surface fluxes from observations of the PBL have been constrained by difficulties in accurately estimating and parameterizing the conservation equation, and have been limited to multi-day averages or small samples of daily case studies. Using radiosonde and surface flux data for June, July, and August of 1997, 1999, and 2001 a conservation approach was applied to 132 sets of daily observations. Results highlight the limitations of using this method on daily time scales due to the diurnal variability and complexity of entrainment. A statistical investigation of relationships among PBL and both land-surface and near-surface properties that are not explicitly included in conservation methods indicates that atmospheric stability in the layer of PBL growth is the most influential variable controlling PBL development. Significant relationships between PBL height and soil moisture, 2m-potential temperature, and 2m-specific humidity are also identified through this analysis and revealed that 76 percent of the variance in PBL height can be explained by observations of stability and soil water content. Using this approach, it is also possible to use limited observations of the PBL to estimate soil moisture on daily timescales without the need for detailed land surface parameterizations. In the future, the general framework presented may provide a means for robust estimation of near-surface soil moisture and land surface energy balance over regional scales.