Study on the Variation Characteristics of Meteorological Elements in the Boundary Layer of Two Types of ShortTime Heavy Rainfall
This article focuses on the application of the 2013-2015 Beijing meteorological tower data and derivative data, combined with conventional and unconventional observation data, such as VDRAS, automatic weather stations and NCEP reanalysis data. According to the evolution of the boundary layer elements, shorttime heavy precipitation is divided into two types, one has the surface convergence line and the other has not. And we also focus on the evolution of the boundary layer elements of the two types shorttime rainfalls to find the forecasting signal before heavy rainfalls occur in summer, which could provide reference for the shorttime heavy rainfall forecasting. The results show that varivation of the elements of the meteorological power can not predict for the occurrence of the nonsurface convergence line type, but it has certain guiding significance to the shorttime severe rainfall of the surface convergence line type. Before such type of heavy rain occurs, the temperature and potential temperature begin to decrease obviously and decline rate gradually increases. The temperature change rate gradually increases to -0.35℃ per minute. The specific humidity increases significantly 3 h before the start of the heavy rainfall below 325 m. When it begins to rain, the specific humidity decreases about 3.5 g·kg-1 during 20 min before the rainfall begins. The lowlevel wind shear is up to the strong degree. But the specific humidity and lowlevel wind shear can show the signals at 10-20 min lead time. So the evolution of tower meteorological elements and the physical quantities have indicative meaning for the forecasting and warning of shorttime rainfall of surface convergence line type.