Entrainment Zone Thickness And Convective Boundary Layer Over Wuhan (30.5°N,114.4°E) Observed By Lidar

The Earth's surface is the bottom boundary of the atmosphere.The portion of the atmosphere most affected by that boundary is called the atmosphere boundary layer(ABL),or boundary layer for short.The thickness of the boundary layer is quite variable in space and time.Normally ~1 or 2 km thick(occupying the bottom 10 to 20% of the troposphere),it can range from tens of meters to 4 km or more.Turbulence and static stability conspire to sandwich a strong stable layer(called a capping inversion)between the boundary layer below and the rest of the troposphere above(called atmosphere).This stable layer traps turbulence,pollutants,and moisture below it and prevents most of the surface friction from being felt by the free atmosphere.This paper introduces the working principle and basics structure of a lidar briefly the configuration of Wuhan University Polarization Lidar System and experimental detection techniques as well as its application in measuring atmosphere are discussed in detail.Variations of the Convective Boundary Layer(CBL)height and Entrainment Zone Thickness(EZT)have been studied based on 532-nm polarization lidar measurements between January 2011 and December 2017 at Wuhan(30.5°N,114.4°E),China.The 1-min backscatter ratio R profiles are retrieved using the backward iteration Fernald method.The hourly CBL height and EZT are determined with the variance method.The results indicate that the CBL height and the EZT over Wuhan have obvious seasonal variation.The average value of the maximum CBL height is 1.14,1.25,1.06,and 0.74 km in spring,summer,autumn,and winter respectively,while the average EZT is 0.4,0.51,0.34,and 0.26 km in spring,summer,autumn,and winter respectively.These characteristics have a clear-cut positive correlation with the land surface temperature in Wuhan.