The field program will use the CASES site within the Walnut River Watershed east of Wichita, Kansas, near which there are already several sets of instrumentation in place (the Department of Energy ARM-CART Great Plains site, the Argonne National Laboratory Atmospheric Boundary Layer Experiments (ANL ABLE) sites, and the NOAA Wind Profiler Network), together with enhanced instrumentation, for one month of extensive measurements during October 1999. The experimental site is a watershed, but a relatively shallow one with typical slopes of 0.5o or less, and is climatologically favored for clear sky and weakly stable (0.25 < Ri <1.0) to very stable (Ri > 1.0) conditions during autumn.

CASES-99 will combine measurements and data analyses with state-of-the-art numerical modeling to investigate five areas of scientific interest. The choice of these scientific topics is motivated by both the need to delineate physical processes that characterize the stable boundary layer, which are as yet not clearly understood (see Nappo and Johansson, 1998), and the specific scientific goals of the investigators. The scientific areas addressed in this request are: 1) Intermittent turbulent transfer of momentum, moisture and sensible heat, and sensible and radiative flux divergences of heat in the surface layer of the stable nighttime boundary layer (including, specifically, characterization of the heterogeneity and relevant scales of these fluxes); 2) Nonstationarity and momentum, heat and moisture flux divergence associated with vertical shear flow instabilities near the ground and aloft, the overturning of Kelvin-Helmholtz billows and internal gravity waves; 3) Enhanced dissipation of kinetic energy associated with small-scale density fronts and synoptic-scale cold fronts and; 4) The specific source mechanisms for the generation of inertial oscillations, with emphasis on the evening boundary layer transition and on frontal passages.

Effective research in these scientific areas relies heavily on high-quality measurements of temperature, moisture, and momentum fluxes over horizontal and vertical scales and on knowledge of the meso-(-scale atmospheric environment within which events occur that cause the fluxes. The instruments requested in this LAOF proposal will provide the core measurements upon which testing of many of the associated scientific hypotheses will depend. Furthermore, if this request is granted, the entire multi-agency, multi-nation plan for deployment of instruments for CASES-99 will center upon the LAOF group of reliable, high-quality, measurement systems. A summary of requested instrumentation is as follows:

1. 1 GLASS (to be co-located with the 40-meter tower);
2. 3 ISS (to be place in a triangular, meso-(-scale array surrounding the main CASES-99 site);
3. 9 ISFF (3 to be placed on one 40-meter tower, 6 to be distributed in concentric triangles);
4. 8 extra PRTs, preferably with 5 Hz or better sampling, to be placed on the 40-meter tower (5 m intervals);
5. The Wyoming King Air (addressed through a separate request);
6. Multiple radiative flux divergence instruments accurate to ~ 1 Wm-2 and water vapor flux with the ISFFs;
7. A 40-meter tower (to have 3 ISFF sets, plus a number of other investigator supplied instruments).