Abstract
Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR) reflectivity data is compared with freezing level (altitude of the 0C̊ isotherm) values derived from National Center for Environmental Prediction (NCEP) 40-Year Reanalysis to determine the relationship between the two sets of data. To establish a baseline for comparison, a climatology of NCEP freezing level data is produced. NCEP freezing level is derived using a reverse linear interpolation scheme applied to the temperature profile for each gunpoint. Global monthly means and measures of variability are calculated for the period 1979-1998, and a 20-year global climatology is presented. Zonal means are calculated from the monthly mean data for 1998 and the 1979-1998 climatology. The NCEP freezing level is considered a proxy for the melting level, and is compared with derived TRMM PR melting level values. Some difference is expected, as some time is required for frozen precipitation to fall through freezing level, melt, and create a melting layer and "bright band'' signature. To estimate the height of the melting level, an algorithm is used to isolate the maximum reflectivity altitude in the vertical reflectivity profile of mature tropical convection. The 1998 monthly mean melting levee from the TRMM PR data are compared to the calculated NCEP monthly means and 20-year freezing level climatology. Generally, the TRMM PR retrieved values are about 600 m lower than the NCEP freezing level height and show similar spatial distribution to the NCEP data.
Harris, Gettys Nunn (1999). Comparison of melting level altitudes from the NCEP reanalysis with TRMM precipitation radar data. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1999 -THESIS -H375.