Vertical structure of precipitation observed by NOAA profilers and NASA TRMM Precipitation Radar during NAME 2004

In support of the NAME 2004 field campaign, NOAA established and maintained a field site about 100 km north of Mazatlan consisting of wind profilers, precipitation profilers, surface upward/downward looking radiometers, and a 10-m meteorological tower to observe the environment within the North American monsoon. Three objectives of this NOAA project are discussed in this paper: (1) observe the vertical structure of precipitating cloud systems as they passed over the NOAA profiler site, (2) estimate the vertical air motion and the raindrop size distribution from near the surface to just below the melting layer, and (3) better understand the microphysical processes associated with stratiform rain containing well-defined radar brightbands.

In order to provide a climatological context for the profiler observations at the field site, the profiler reflectivity distributions were compared with TRMM Precipitation Radar (PR) reflectivity distributions from the 2004 season over the NAME domain as well as from the 1998-2005 seasons. This analysis places the NAME 2004 observations into context of other monsoon seasons. It also provides a basis for evaluating the representativeness of the structure of the precipitation systems sampled at this location. The number of rain events observed by the TRMM PR is dependent on geography; the land region, which includes portions of the Sierra Madre Occidental, has more events than the coast and gulf regions. Conversely, we conclude from this study that the frequencies of occurrence of stratiform rain and reflectivity profiles with radar brightbands are mostly independent of region. The analysis also revealed that the reflectivity distribution at each height has more year-to-year variability than region-to-region variability. These findings suggest that in cases with a well-defined brightband, the vertical profile of reflectivity relative to the height of the brightband is similar over the gulf, coast, and land regions.