The difference and correlation between microwave radiometer and radiosonde are presented in this paper, based on conventional sounding, MP 3000A ground based microwave radiometer and automatic station data. Result shows temperature and relative humidity differences from Suzhou ground based microwave radiometer are 3.2℃ and 29% respectively, while correlation coefficients are above 0.98 and around 0.5 accordingly. Analysis of signature for microwave radiometer observations in different weather conditions illustrates that there is a good correspondence between the vertical variations of relative humidity, liquid water content and the rainfall, severe weather, and fog. In precipitation and strong convection cases, relative humidity below 6 km increases ahead of the weather process (lead time of increase in relative humidity in rainfall case is longer than that in severe convection case), liquid water content below 3.5 km rises rapidly, especially in the height from 2.25 to 3.25 km. However, in fog cases, increase of relative humidity is below 3-3.5 km and liquid water content is below 1.5 km. A index and convective stability index may lost their indicative significance after obvious precipitation appears, but they perform well at the beginning of rainfall (especially remarkable rains) and in the fog case.