9402021 Palmer Knowledge of spatial and frequency domain interferometric (SI/FDI) techniques has progressed to a point where real scientific gains are being obtained. Using these relatively new techniques has provided the scientist with additional observations to investigate the atmosphere. The first phase of the project is the study of the planetary boundary layer (PBL) using a recently acquired 915 MHz radar at the University of Nebraska-Lincoln. We propose to modify the radar so that FDI can be performed. The main goal is to study the effect on gravity wave propagation of low- level jets, which exist in the Great Plains region. The proposed research also extends into the tropo/stratospheric regions, where the PIs are interested in refining the observational methods. Although the idea of "corrected" vertical velocities at VHF wave- lengths was introduced in 1985, recent measurements at multiple wavelengths has cast doubt on this idea. The PIs intend to investigate the problem using the MU radar facility in Japan, where there is a VHF interferometric system along with a UHF boundary layer radar. The effect of the jet stream on refractivity layer tilting will also be investigated using SI techniques. Isentropic surface are known to reverse in tilt above and below a jet stream peak. Japan has an extremely strong jet in the winter and it is proposed to make measurements directly related to studying the jet stream. Using the Sondre Stromfjord radar in Greenland, the MU radar in Japan, and the modified 915 MHz radar in Nebraska, the dependence of FDI techniques on wavelength will be investigated. The FDI techniques can provide an estimate of the vertical extend of turbulent layers, which may have a dependence on radar wavelength. Observations using these three wavelengths should elucidate this problem.
