The torrential rainfall from typhoon caused the damage and loss of lives and properties. The low visibility produced by heavy fog always has a significant impact on transportation and military mission. The above-mentioned atmospheric parameters are the requirements of operational organizations. The aim of this study is rainfall estimation and fog detection by passive microwave data. Satellite passive microwave observations have potential to provide rainfall estimation and fog detection for wide oceans. The rainfall estimation for typhoons over ocean is using Bayesian approach. The fog detection over sea is based on the difference of brightness temperatures of TMI channels between heavy fog and clear weather conditions. The preliminary analysis shows the difference of brightness temperature is obvious in high frequency channels, especially in 85 GHz. In addition, we compare retrieved rain rate with that obtained from Precipitation Radar. Their correlation coefficients are 0.68 and 0.75 for the convection and stratiform rainfall patterns, respectively.