Assessing Local Land-Atmosphere Coupling from a Global Land Data Assimilation Reanalysis

Abstract:

The interaction between the land and atmosphere affects the evolution of both these systems, and requires a proper understanding and then realistic representation of the physical processes in weather and climate models. This interaction begins at a local scale, i.e. between surface fluxes and the near-surface atmosphere, with the strength of near-surface land-atmosphere coupling dependent on the relationship between soil moisture and evapotranspiration, a function of the surface-layer turbulence and vegetation and soil properties, where for strong land-atmosphere coupling, a given change in soil moisture yields a large change in evapotranspiration, and conversely for weak coupling, the change in soil moisture yields only a small change in evapotranspiration. Following a conceptual development, we use observations from surface flux sites to examine the various aspects of local land-atmosphere interaction, then extend this to the global scale by assessing the coupling using a global land data assimilation (GLDAS) data set from NCEP.