Structure of thunderstorm gust fronts for Bojnord (Northeast of Iran) using SODAR data

The structures of thunderstorm outflows at 2011 are studied using surface and SODAR data at Bojnord stations. In this study, several thunderstorms that occurred in Bojnord investigated and selected 3 outstanding of them at 2011. Distinctive features associated with this thunderstorms are: a sudden drop in temperature ( ~ 3- 13 °C ), sudden increasing in wind speed ( ~ 10-20 m/s), wind shift(60-80), a pressure rise ( ~ 2-5 mb ), a humidity increment(14-51 %) , lightening, rain shower and hail. In horizontal wind profiles, there are two maxima. When the horizontal component of wind is maximum, its vertical component becomes minimum which is predictable through considering of vertical structure of thunderstorms by continuity. Time variations of vertical component of wind speed show that instability is developed along the top of the thunderstorm head near the surface. Calculation shows that we have severe wind shear in passing of this kind thunderstorm from Bojnord. This wind shear is dangerous for aviation in airport of Bojnord. Contours of vertical and horizontal components of wind velocity and wind direction are show that these thunderstorms have similar shapes but vary in size. This analysis also shows that the outflow has a complex and multi frontal structure. Further observational work is required for more detailed analysis of the gust front in vertical and horizontal extends.

Keywords: Thunderstorm, Vertical structure, wind shear