Characteristics Of Xian Boundary Layer Winds From Wind Profiler Radar Datasets

Atmospheric boundary layer(ABL)is the lowest part of troposphere with the height of about1~2 km,which is the main living space of human being.The wind field is very important for the study of diffusion of air pollutants,atmospheric dynamics,weather prediction and climate change.Thus we studied the characteristics of atmospheric winds in Xian boundary layer from datasets of ABL wind profile radar(WPR)located at Xian city,Shanxi province.The main conclusions are summarized as following:(1)The validation of WPR horizontal winds.Systematic comparisons have been done between WPR horizontal winds datasets(year of 2014 and 2015)and L band radar sounding datasets and the ERA-interim reanalysis datasets of the same periods with different seasons,different height levels and different observation time.The results tell that the horizontal winds of WPR are totally consistent with L band radar sounding datasets and ERA-interim reanalysis in describing the mean processes.So the horizontal winds datasets are good for study and other meteorological service.(2)The ABL wind characteristics from two years WPR observations.Two years WPR horizontal winds observations are used to analyze the characteristics of ABL winds of Xian city.The results give the distributions of effective observation in hour time scale.The WPR covers the ABL very good with more than 22 hours' coverage except the height of 880 m.The WPR can also monitor the height of 3 to 4 km,but there is a gap between 2 to 3 km.The daily mean total winds are mostly less than 15 m/s,and are often less than 10 m/s.The total winds between 1 to 2 km is heavy than heights below 1 km,and the wind speed increases from 3 km,which get 20 m/s.The daily mean zonal and meridional winds are relative small,the maximum speed is about 10 m/s.The mean winds below 2 km reach the maximum about 6~8 m/s,with the standard deviation of 3~4 m/s.The mean wind decrease from 0.88 km to 1 km,and then increase again above 1 km.The monthly mean zonal and meridional winds are very small,mostly less than 1 m/s,the maximum standard deviation is about 2~3 m/s.The altitude change is also very small to zonal winds and meridional winds.There is a discontinuity of mean zonal and meridional winds in the vertical around 1 km in the winter season,but cannot be found in thesummer season.(3)The typical periodic variations by Lomb-Scargle spectrum analysis.The total wins,zonal winds and meridional winds are analyzed using Lomb-Scargle spectrum analysis to get the typical variations.The results implies that the total winds are similar with zonal winds with the periods like 10 to 14 days,but the periodic variation of meridional winds are very different.