Impact Analysis of a Taihang Mountain Fohn on Haze Intensity
Utilizing the NCEP reanalysis data, and the every 5 minute data of ground automatic weather station, laser radar, wind profiler and microwave radiometer, we analyzed the changes of haze intensity in a typical fohn process in Shijiazhuang during the winter of 2015. The results show that the east of Taihang Mountain experienced obvious fohn due to the topographic trough over North China with static and stable weather situation. The fohn led to a rapid decline in humidity, which might cause the rapid rising of horizontal visibility, the decline of PM2.5 concentration and the weakening of haze intensity. Laser radar could visually reflect the changes of boundary layer structure and the concentration of pollutants before and after the fohn. By using the wind profile, we learned that the changes of wind direction (may vary a lot) and speed (may be larger) are obvious below 300 m, which proves the strong pulsation of wind. The horizontal and vertical scales of fohn are 25 km and 1 km, respectively.