Abstract:

Based on the NCEP reanalysis data and conventionally observational data, influence mechanism of establishment of mixed layer (ML) on a strong gust weather process on March 23 2012 in Tianjin was diagnosed and simulated. The results show that joint action of strong pressure and allobaric gradient in front of cold high is synoptic background of formation of surface strong gusts. Strong gusts occur in the period of higher surface temperature, lower pressure and low relative humidity. In the afternoon, the hot and dry convection within the deep ML makes the upper-level momentum that is in the north side of upper jet easily propagate to ground layer effectively, which leads to enhancement of surface gusts. The establishment of deep ML is another reason leading to formation of strong surface gusts. Results simulated by the WRF suggest that local intensity of the ML may cause local differences of downward propagation of momentum, which may be the important factor causing spatial differences of gusts intensity over Tianjin.

Key words: Tianjin area, Strong gusts, Mixed layer, Downward propagation of momentum, Numerical simulation