Tropospheric Structure And Reliability Of Reanalysis Data In The Arctic

Human activities are mainly in the troposphere,especially in the Atmospheric Boundary Layer?ABL?.The troposphere and atmospheric boundary layer are closely related to climate change,synoptic systems,interaction between atmosphere and ocean/ice snow/land,etc.A full understanding of troposphere and boundary layer structure is helpful to study synoptic system and improve accuracy weather prediction.Comparing with the middle and low latitude regions,the density of automatic weather stations and sounding stations around Arctic is low.There are few automatic weather stations buoying which can work continuously to obtain long time series of ground meteorological data,and lack of atmospheric troposphere profile data on the Arctic Ocean.Meteorologists can only investigate the troposphere structure of the Arctic through satellite remote sensing products,reanalysis data and numerical models.In this paper,the altitude,temperature,air pressure,relative humidity and wind speed of the troposphere are calculated from the sounding data of Xuelong during China's 6th to 9th Arctic scientific expedition.It is concluded that in summer over the Arctic Pacific sector and the Bering Sea,the altitude of the troposphere is about 10km and decreases when latitude increasing,and is lower than that over the mid and low latitude,but higher than the annual average in Arctic.LRT and CPT are suitable for diagnosing troposphere height,with strong consistency and positive correlation.By comparing tropopause potential height,temperature and pressure of NCEP/NCAR reanalysis1 reanalysis data with sounding,it is confirmed that the products of reanalysis1 tropopause are basically consistent with the actual atmospheric tropospheric state.The potential height of the tropopause in the Arctic increases with latitude,and the seasonal variation of the increasing of latitude weakens,as it is higher in summer than winter.The seasonal variation of the increase of latitude strengthens when the temperature of tropopause is higher in summer than in winter.Since 1948,the tropopause of 50°N?60°N has decreased while 70°N?90°N increased.Over the Arctic Ocean,the correlation between NECP?TGH and 500h Pa/200h Pa is positive in summer and negative in winter.In summer over the Arctic Pacific sector and the Bering Sea,the lapse rate in the middle troposphere is 6.4??km^-1,and there are inversions in the lower troposphere and the tropopause;the inversion height and thickness of the tropopause decrease with latitude,with the relative humidity declining sharply;90%of the precipitable water in the troposphere concentrates in the middle and lower layers,and it has a negative correlation with latitude;wind speed in troposphere increases with raise.The maximum wind speed and height of the high-altitude jet decrease in high latitude regions,and the typical high-altitude jet in the temperate zone is obvious at60°N?65°N in the 6th Arctic scientific expedition.Case study shows that Heffer's scheme is suitable for diagnosing the height of convective boundary layer,and the calculation result is low when stable.The ABL Height estimated by Heffer's scheme is close to Sullivan's scheme,and higher than Wyngaard's scheme.In the inversion layer near the top of ABL,the weak turbulence leads to strong vertical gradient of relative humidity and slows down raise of sounding balloon.In summer,the mean ABL height over the Arctic Pacific sector and the Bering Sea is only 362.6m,lower than that of the middle and low latitude regions.ABL height gradually decreases from July to September,as well as decreases from 50°N to 80°N.The comparison of Reanalysis data?ERA5/Reanalysis1?and Observation indicates that ERA5 can more accurately describe the atmospheric state in the Arctic troposphere,which is more reliable for investigating of Arctic climate,atmospheric vertical structure and synoptic systems,especially in the middle troposphere.Temperature of Reanalysis data performs better than relative humidity and wind speed.Complex surface reduces the ability of reanalysis data to reconstruct meteorological elements in ABL,especially near the ground.