Abstract:The high-temporal-resolution water vapor density, integral water vapor content (V) and liquid water path (L) measured by ground-based microwave radiometer have important application potential and value in the prediction and research of severe convective precipitation. The paper uses these data to study the water vapor distribution, evolution and vapor-liquid conversion in different stages before and after the two thunderstorms that happened in Urumqi and Chengdu airports, respectively. During the July 4 thunderstorm in Urumqi, under the action of water vapor transport and vertical motion, the low-level water vapor density significantly increased before precipitation and recovered rapidly after precipitation. Before the July 15 thunderstorm precipitation in Chengdu, the whole-layer water vapor experienced the evolution process of increasing first and then decreasing. During the process of water vapor accumulation, the maximum increment was 4.99 g·m-3. During the process of water vapor conversion, the whole-layer water vapor decreased rapidly, of which the water vapor density decreased more significantly at the height of clouds. The cloud water vapor content (IWVc) inversion in the text is better than V and L in indicating the onset and end of precipitation. Before the Urumqi July 4 precipitation, IWVc increased by 1.8 times and 2.2 times, respectively. After the end of precipitation, IWVc decreased rapidly. Before the precipita-tion in Chengdu on July 15, IWVc increased by 1.3 times and 1.5 times, respectively. During the severe precipitation, the growth rate of water vapor in the cloud was lower than that of water vapor conversion. In addition, the increase or decrease of IWVc can also be good indicators for the precipitation intensity of the two thunderstorm processes. For the stable precipitation of the Urumqi July 4 thunderstorm, as the IWVc increased, the surface precipitation intensity increased. Moreover, the greater the increment of water vapor in clouds, the higher the surface precipitation intensity. In the period when the IWVc decreased, the precipitation amount was less than 0.01 mm. For the showery precipitation during the Chengdu July 15 thunderstorm, the accumulation of IWVc was ahead of the occurrence of surface precipitation. The more the IWVc accumulated, the severer the surface precipitation happened. After turning into stable precipitation, the relationship between IWVc and surface precipitation returned to the corresponding increase or decrease, and the decline of IWVc increment or decrement also indicated the 〖JP2〗weakening and end of the precipi-〖JP〗tation.