Evaluation of the Impact of Instrument Noises on F18 Special Sensor Microwave Imager/Sounder Measurements and Noises Correction

The SSMIS on board the Defense Meteorological Satellite Program (DMSP) F-16, F-17, F-18 satellites platform is a series of passive microwave conical scan instruments which can provide atmospheric temperature, water vapor profiles as well as surface parameters by combining AMSU like temperature and water vapor sounding channels and SSMI like window channels. The Sensor Microwave Imager/Sounder (SSMIS) measurement is effected by instrument issues like solar intrusions into the warm calibration load, main reflector emissions. These issues greatly reduced the data quality and need to be considered before assimilation of SSMI/S measurements in NWP. In this paper the effects of instrument parameters noises on L1-B level SSMI/S measurements and biases (O-B) of SSMI/S measurements from brightness temperature simulated by Community Radiative Transfer Model (CRTM) are analyzed. The first part of the paper is noise filtering. The frequency spectrum of noises in warm load count (WLC), and platinum resistance thermometer (PRT) temperature are analyzed. The WLC and PRT are reconstructed by filtering the high frequency noises. After that the brightness temperature measurements are reconstructed. The difference between the reconstructed brightness temperature and original brightness temperature follows the change of solar zenith angle. This implies the effect of solar intrusions has been reduced. Principle component analysis (PCA) is also applied to filter the noise in WLC and PRT. The brightness temperatures reconstructed through these two methods are compared. In the second part of the paper, the reflector temperature is reconstructed from measured arm-rim temperature. Then the reflector emissions are removed from the reconstructed brightness temperatures. The O-B mean value and standard deviation are reduced after removal of reflector emissions.