Comparison of Tropospheric Temperature Derived from the Microwave Sounding Unit and the National Meteorological Center Analysis

Abstract

The Microwave Sounding Units (MSU) aboard the NOAA series of polar-orbiting satellites (TIROS-N to NOAA-12) have provided stable and precise measurements of vertically integrated atmospheric temperature since December 1978. Comparisons are made between the MSU channel measurements and temperatures derived from the global data assimilation system (GDAS) at the National Meteorological Center (NMC) for the period 1979?1990. The largest correlations occur at high to midlatitudes, where the troposphere exhibits large monthly anomaly fields, and where radiosondes provide ample coverage for the GDAS. Intermonthly differences from each dataset had global correlations above 0.97. However, poor correlations with MSU were noted over areas of high terrain and tropical landmasses. These poorer correlations can be attributed to temporal changes and data limitations in the GDAS analysis. Comparisons between the GDAS and MSU temperature anomaly fields indicate that frequent model changes mask the climate signal in the GDAS analysis. Nonetheless, the study suggests that both GDAS- and MSU-derived temperature anomalies detect similar spatial and temporal variability over regions where the GDAS is data rich and the signal is large, that is, the El Niño-Southern Oscillations. This study suggests that the NMC reanalysis, using a fixed assimilation model, will produce a stable dataset of tropospheric temperatures. Therefore, the 35 years of reanalyzed NMC model data can he used in conjunction with satellite data to improve the suite of tools used in climate monitoring.