Improvements In The Height Of The Boundary Layer In A Desert Region And Changes In The Amount Of Sand Produced By Dust Tornadoes

The atmospheric boundary layer height is closely related to the dust emission of dust aerosols,and the Planetary Boundary Layer Height(PBLH)of summer is underestimated in model.On the basis of the YSU boundary layer parameterisation scheme,research the Tengger Desert region from June to August in summer 2019,by using sounding and conventional meteorological data from the Minqin station site and FNL reanalysis information from the National Centers for Environmental Prediction(NCEP)and the National Center for Atmospheric Research(NCAR),and Coupling to a dust cyclone sand initiation scheme constructed by Tang et al.The meteorological elements in the study area are first simulated using the MYJ,YSU,and BL boundary layer parameterization schemes to determine which boundary layer parameterization scheme can better simulate the boundary layer height in the desert region.An empirically modified boundary layer RYSU scheme was also used to compare the improved boundary layer heights.The spatial and temporal distributions of sand initiation in the Tengger Desert in the summer of 2019 were then obtained using the dust cyclone sand initiation scheme,the conclusions are as follows:(1)Daily variations and regional characteristics of near-surface meteorological elements in the study area were simulated using the MYJ and BL parameterisation schemes in the WRF model and the YSU parameterisation scheme.The YSU scheme simulates best in the near-surface simulations,but all three schemes are unsatisfactory in the vertical field simulations and in the simulations of boundary layer heights.the boundary layer parameterisation schemes is required to be revisied.(2)The meteorological elements of the near-surface and vertical fields in the study area were simulated with the parametric schemes MYJ and BL in the WRF model and YSU in the non-local closure scheme,and compared with observations,showing that the YSU scheme is the best in the desert area,but it still has very large errors,especially in the boundary layer height,which varies about 2 km and needs to be corrected for the YSU parametric scheme.(3)Using the coupled RYSU scheme WRF-Chem model and Tang's dust devil emission initiation scheme,the spatial and temporal distribution of the dust devil emission in the Tengger Desert in summer 2019 was obtained,,and the instantaneous dust devil emission and extent of dust devil emission at the whole point simulated by the RYSU scheme were higher than those of the YSU scheme from 08:00 to 18:00.The frequency of occurrence is closer to that observed in the Tengger Desert.At the same time,the total daily dust devil emission in the study area from June to August with the RYSU scheme is almost three times higher than with the YSU scheme,indicating that the boundary layer height has a significant influence on the dust devil emission.(4)Simply making the boundary layer height more realistic,with all other factors held constant,triples the amount of the total daily dust devil emission,and ust devil emission contributs 62.3% to the dust aerosol,indicating that the annual contribution of dust devil to dust aerosols is higher than that of dust storms dominated by powered sand initiation mechanisms.