ARS | Publication request: Remote sensing, field measurements and large eddy simulation: Tools for investigating evaporation and land-atmosphere dynamics

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: September 22, 2008
Publication Date: October 15, 2008
Citation: Kustas, W.P., Bertoldi, G., Albertson, J.D. 2008. Remote sensing, field measurements and large eddy simulation: Tools for investigating evaporation and land-atmosphere dynamics [abstract]. American Geophysical Union. H13H-06.

Technical Abstract: Understanding and predicting the impact of land surface heterogeneity on landscape and regional scale evapotranspiration estimates is one of the major unresolved research problems being addressed by hydrologists and atmospheric scientists. While land cover characteristics and surface states used as input to land surface models are available at patch and landscape scale (~100-1000 m), atmospheric properties are often assumed uniform at regional scales (10-100 km). This scale mismatch between land surface and atmospheric states has been noted as a significant source of error in regional flux estimation. To address this issue, a research approach was developed which combined a Large Eddy Simulation (LES) with a land surface scheme that used remotely sensed land surface boundary conditions to simulate the three dimensional turbulence in the Atmospheric Boundary Layer (ABL). This approach provided the opportunity to explore the impact of variation in both the size and magnitude of contrasts in key land surface states/conditions (i.e., moisture, vegetation density, surface temperature) on atmospheric surface layer properties (i.e., wind speed, air temperature, humidity) using observations from large scale remote sensing field experiments. Research results will be presented on evaluating the roles of air temperature and wind speed variability in heat flux estimation, and on techniques for estimating spatial variability in atmospheric properties, which directly address the issue of scale mismatch. In addition, combining these tools has allowed us to investigate the impact of ABL dynamics on water vapor and sensible heat flux transport that is seen to cause anomalies in source-area footprint predictions when comparing land surface model output with aircraft-flux observations in the atmospheric surface layer. The later findings, point to the development of footprint models that consider different source area/footprint contributions for so-called active scalars (temperature) versus passive scalars (water vapor) by using remote sensing information on the spatial variation of important land surface states and atmospheric conditions.