Atmosphere-Land Surface Interaction Over A Midwest Watershed: CASES-97

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This renewal project seeks to understand the interaction between the land surface and the atmosphere. It continues the analysis of data collected in a month-long field expedition conducted in the spring of 1997. The overall objective of this project is to observe the effect of surface processes on the evolution of the atmospheric boundary layer over the course of a 24-hr period (diurnal cycle). Though observational in nature, the project is closely allied with on-going work in atmospheric boundary layer modeling and parameterization of boundary layer effects in large-scale models. It is unique in several respects: (a) it concentrates upon a mesoscale watershed with moderately complex terrain (Kansas); (b) it focuses upon fair weather situations with no lower clouds and only scattered cirrus; (c) intensive observing periods covered 4 complete and 2 partial diurnal cycles with varying degrees of soil moisture and plant maturity. Specifically, the current objectives are: o Extend atmospheric sensible heat and moisture budget computation for two intensive observing periods (IOP) from the morning period to the evening period and include entrainment from the atmosphere on top of the boundary layer.o Complete budget computations for the rest of the IOPs and investigate the effect of' observed variations in soil moisture and land cover.o Compare an evapotranspiration algorithm to measured 5-cm soil moisture and eddy correlation evaporation.o Investigate the characteristics of the nocturnal boundary layer. Through interaction with atmospheric modelers, this observational project will contribute to the improvement of boundary layer parameterizations within large atmospheric models.