On the Characterization and Mitigation of Noise in Space-Borne Microwave Sounding Instruments

Space-borne microwave sounding instruments have become vital data sources for weather prediction and climate change studies. Among the various radiometer configurations, the total power microwave radiometer is particularly appealing for current and future operational satellites due to its superior sensitivity and simple design. However, its performance is vulnerable to degradation caused by receiver gain fluctuations, electronic 1/f noise, and other time-varying receiver characteristics. For numerical weather prediction (NWP) users, 1/f noise introduces interchannel correlations, complicating the assimilation of affected observations and reducing their accuracy. Addressing this noise issue in the ground data-processing system is essential to enhance the utility of microwave sounding data. This article focuses on the characterization and mitigation of noise in current and future microwave sounding instruments, with particular emphasis on the impact of 1/f noise. Various methods are applied to quantitatively characterize noise features in both the frequency and time domains. Additionally, the influence of calibration parameters on 1/f noise is analyzed. Based on these findings, we propose a mitigation algorithm for reducing noise during the on-orbit calibration of microwave sounding instruments, aiming to improve the quality of retrieved data for operational use.