| Abstrakt: |
Based on conventional meteorological observation data, ECMWF model data, etc., the causes of rainstorm in the northeast of Qinghai from the afternoon to the night of August 19, 2019 were analyzed, and the causes and predictability of major forecast errors were discussed. The results show that there was high temperature, high humidity and high energy in the middle and low layers in the early period of rainstorm. As the subtropical high retreated eastwards, the high-altitude trough of the westerly belt and the vertical shear line of the plateau moved eastwards to make ground cold air move eastwards, and local short-term heavy precipitation appeared under the influence of this weather system. At the same time, the high-level dry and cold air moved into convective unstable areas. The wind speed at 700 hPa strengthened, and the low-level jet stream appeared to aggravate the instability of atmospheric stratification, which was more conducive to the generation of convection. The forecast results of precipitation based on various numerical models were significantly smaller, and the predicted western cold air was obviously weaker, which was also one of the reasons why the weak transportation of the western water vapor resulted in a small value of predicted precipitation. In the adjustment of model forecast, the proportion and amount of convective precipitation should be adjusted to be large, which has a certain indicating significance for the forecast of convective precipitation. In short-term nowcasting, the deviation of major weather systems predicted based on the model should be corrected in real time, and attention should be paid to the location of ground specific humidity and the convergence line. The falling area of heavy precipitation can be judged according to the high-value area of specific humidity, and the maximum of specific humidity appeared 1 -2 h earlier than short-term heavy rainfall. [ABSTRACT FROM AUTHOR] |
