Using brightness temperature and instability indices, such like K Index (KI), Lifting Index (LI), Showalter Index (SI), Total Total Index (TTI) and Convective available potential energy (CAPE) from14-channel ground-based microwave radiometer named RPG-HATPRO-G3, variation tendency before 9 convective-cloud precipitation events in 2015-2016 were analyzed, and compared with which in non-precipitation days. The results showed that in non-precipitation days, brightness temperature at 22 GHz and 58 GHz and 5 instability indices exhibited diurnal variation, and the variation of brightness temperature at 22 GHz was more apparent than that of 58 GHz. The diurnal variation difference of 5 instability indices was larger in summer and autumn than that in winter and spring. Continuous increase of brightness temperature at 22 GHz was observed 34 minutes before the beginning of 9 convective-cloud precipitation events, and the duration of increasing was earlier than continuous decline of brightness temperature at 58 GHz. Moreover, the value and the diurnal variation difference of brightness temperature at 22 GHz were larger than those in non-precipitation days of all four seasons that means brightness temperature at 22 GHz was more indicative than brightness temperature at 58 GHz for the beginning of convective-cloud precipitation events. KI, TTI and CPAE were observed to continuous increase, and the values were larger than mean values in non-precipitation days of all four seasons. On the contrary, LI and SI observed to continuous decline, and the values were smaller than mean values in in non-precipitation days of all four seasons. The value of 5 instability indices can provide references for the threshold of the beginning of convective-cloud precipitation. KI, TTI, LI and SI change duration was observed about 40 minutes before the beginning of convective-cloud precipitation, which was earlier than that of CPAE. The range of brightness temperature at 22 GHz time rate of change was in -1.12~1.12 K·s-1 1 h before 9 convective-cloud precipitation events, and the percentage of which lager than 0.28 K·s-1 gradually increased with being close to the precipitation. It was also noticed that the proportion of large negative time rate in -10~0 min was also higher than that of other periods. In -10~0 min, KI, SI and CPAE time rate of change were in the range of 0.025~0.05 K·s-1, -0.04~0.02 and -12~12 J·kg-1·s-1 respectively. The percentage of the largest KI time rate of change was larger in -10~0 min than that in other time, the same phenomenon could be found in SI and CPAE. But the percentage of largest KI and SI time rate of change were larger than that of CPAE. Considering the time of continuous increase and largest time rate of change, KI and SI were more indicative than CPAE.
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