DIURNAL WINDS OBSERVED IN THE TROPICAL TROPOSPHERE USING 50 MHZ WIND PROFILERS

摘要

The seasonal diurnal zonal and meridional winds observed from 2 to 18 km in the tropical Pacific using five SP-R?Hz wind profilers are presented. The hourly data sets ranged in length from 686 days to 2934 days of observations. The observed diurnal winds are compared with tidal model winds forced by solar absorption of water vapor that are primarily the (1,1,1) tidal mode. Similarities between observed and modeled diurnal winds off the equator (12 degrees S) suggest these off-equator observations are forced by solar absorption of water vapor and are global oscillations. Differences between observed and modeled winds near the equator (2 degrees N and 1 degrees S) suggest these observations are forced by local or mesoscale processes. The vertical structure of meridional wind near the equator supports the diurnal forcing by the radiation of cloud tops and/or cirrus clouds above 12 km or the latent heat release of precipitating clouds extending throughout the troposphere. While near-equator observations appear to be locally forced, the global distribution of these ''local'' forcing mechanisms may generate global oscillations that cannot be resolved with these wind profiler data from the Pacific basin. The observed winds below 4 km appear to be affected by boundary layer processes and have different characteristics than winds above 4 km. [References: 20]