Synoptic-Scale Studies Using the Nimbus 6 Scanning Microwave Spectrometer

Abstract

Several frontal systems over Europe in August 1975 and January and February 1976 are examined using scanning microwave spectrometer (SCAMS) data. Comparisons are made with thermal fields constructed from radiosonde temperatures. Because of the cloud penetrating property of microwave radiation, together with the high stability and sensitivity of the SCAMS instrument, many of the problems encountered with infrared remote sensing instruments are absent in the SCAMS measurements. Synoptic-scale features displayed by the SCAMS retrievals are comparable with radiosonde temperature analysts under both clear and cloudy conditions. Results from the synoptic-scale studies, confirm the theoretical expectations of standard error, which are 2.2, 2.3, 2.9 and 3.6 K at the 700, 500, 300 and 100 mb levels, respectively. These SCAMS results were obtained using “theoretical” temperature retrieval coefficients, which are based on the simulated SCAMS response to a historical sample of independent temperature statistics and as such are unbiased toward any particular meteorological situation. The independence of SCAMS results is substantiated by the small differences found at pressures greater than 300 mb using “derived” temperature retrieval coefficients based on SCAMS measured response to a set of dependent radiosonde temperatures. At pressures less than 300 mb the lack of better weighting functions necessitates the use of improved statistical information in the theoretical coefficients.