TOGA: Triple Doppler Radar Measurements from Aircraft

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This proposal is for the development of a technique to obtain triple Doppler Radar measurement of convective storms using aircraft radar alone. Airborne Doppler radars that make fore and aft conical scans, such as the recently modified NOAA P-3 radars and the NCAR ELDORA radar now under development, could be used with this technique. The advantage of triple over dual Dopper analysis is that all three components of precipitation particle velocity can be obtained. Using mass continuity to obtain vertical air motion, particle terminal velocity can be derived, which allows inferences to be made about precipitation growth. This technique also makes possible a superior estimate of vertical air motion at cloud top, which is needed to derive accurate vertical air velocities. This technique will be used to measure vertical mass fluxes and precipitation evolution in oceanic convective clouds during the intensive field phase of TOGA COARE. Both pieces of information are important in characterizing the convection in the COARE domain. A preliminary test of the technique will be made during the Tropical Cyclone Initiation experiment in July 1991 using a P-3 radar. Results of these measurements will be used to test a model development to predict the vertical fluxes of mass, heat, and moisture in cumulus clouds. This research is important because it is a key study in TOGA/COARE both to describe and understand the principal atmospheric processes that organize convection and to link those convective scale physical processes to the larger scales that affect climate variability in an especially climate sensitive region of the world, the western Pacific Ocean, the field site of TOGA/COARE.