The Influence of Thermal Interaction between Land Surface and Atmospheric Boundary Layer on Cold Front Sandstorm in Hexi Corridor

Abstract

The thermal effect has an important influence on the sand initiation process and dust vertical transport of the dust source area in Hexi Corridor， and it is a key factor to consider in the sandstorm forecast in this area.To reveal the effect of thermal effect on the intensity of cold front sandstorm in Hexi Corridor， using ECMWF ERA5 hourly reanalysis data and conventional meteorological observation data， the similarities and differences of the thermal mechanisms such as the boundary layer temperature， front function and surface heat flux on the basis of favorable background analysis of atmospheric circulation situation were diagnosed and analyzed.The results show that： （1） In addition to the influence of high and low altitude wind speed， the intensity and position of cold and warm air to ground， the intensity of center and transit time of cold front play important roles in the intensity of regional cold front sandstorm； （2） The greater the surface sensible heat flux in the afternoon and the increase of thermal flux from 09:00 （Beijing Time， the same as after） to 14:00， the stronger the intensity of the duststorm.The maximum（ 5-hour increase） afternoon sensible heat flux in general， strong and extremely strong duststorm areas are 367（307） W·m-2， 417 （360）W·m-2and 460（380） W·m-2， respectively.（3） The intensity of the sandstorm increases with the temperature increase range before the outbreak of sandstorm， temperature differences between before and after the outbreak of sandstorm below 1.5 km in the boundary layer， the temperature increase range（ temperature difference）in general， strong and extremely strong duststorm areas are 2.9（-16.5） ℃， 4.9（-17.0） ℃， 7.9（-22.8 ℃）， respectively； （4） The stronger or higher of frontogenesis， the stronger the duststorm.The intensity of frontogenesis in general， strong and extremely strong duststorm areas are 208×10-10 K·m-1·s-1， 477×10-10 K·m-1·s-1 and 686×10-10 K·m-1·s-1， respectively， the accordingly heights of frontogenes are 767 hPa， 686 hPa， 450 hPa.The results of this paper have a scientific understanding of the thermal characteristics of the sandstorm in Hexi Corridor， and provide new ideas and technical methods for improving the accuracy of sandstorm prediction and early warning.

Keywords

• hexi corridor
• cold front standstorm
• boundary layer structure
• frontogenesis function
• surface heat flux