In this study, we quantify the uncertainty of the intra-seasonal to inter-annual variation of TPW derived from multiple MW radiometers under different meteorology (i.e., clear, cloudy, non-precipitation/cloudy and precipitation/cloudy) conditions using collocated TPW estimates derived from COSMIC (Constellation System for Meteorology, Ionosphere and Climate) radio occultation (RO). The Global Positioning System (GPS) Radio Occultation (RO) is an active remote sensing technique, which is complementary with the passive microwave and infrared sounders and microwave imagers. Because GPS RO data are not sensitive to clouds and precipitation, GPS RO derived water vapour products are very useful to identify the possible TWP biases retrieved from measurements of passive microwave sounders and imagers under different meteorology conditions. Results show that the mean microwave radiometer - COSMIC TPW differences range from 0.06-0.18 mm for clear skies, 0.79-0.96 mm for cloudy skies, 0.46-0.49 mm for cloudy but non-precipitation conditions, and 1.64-1.88 mm for precipitation conditions. Because RO measurements are not significantly affected by clouds and precipitation, the biases mainly result from MW retrieval uncertainties under cloudy and precipitating conditions. All COSMIC and MW radiometers detect a positive TPW trend over these ten years. The trend using all COSMIC observations collocated with MW pixels is 1.79 mm/decade, with a 95% confidence interval of (0.96, 2.63), which is in close agreement with the trend estimated by all MW observations (1.78 mm/decade with a 95% confidence interval of 0.94, 2.62). These two trends from independent observations are larger than previous estimates and are a strong indication of the positive water vapor-temperature feedback in a warming planet.