Retrieval And Analysis Of Atmospheric Boundary Layer Height Based On Turbulent Kinetic Energy Dissipation Rate

The atmospheric boundary layer(ABL)is the lowest layer of the Earth’s atmosphere.As an important characterization of the ABL structure,the boundary layer height(BLH)is a key parameter in weather,climate,and air quality forecast models.Usually,the BLH is retrieved from the vertical profiles of tracers,such as aerosol concentration or turbulence intensity.As an active remote sensing instrument,coherent Doppler wind lidar(CDWL)is one of the most promising instruments in detecting BLH.However,there are still challenges.One is the robustness of BLH detections in long-term observations or harsh environment.The other is the applicability of the turbulent kinetic energy dissipation rate(TKEDR)threshold for retrieving mixed layer height(MLH)under different convective weather conditions.The third is the interference of atmospheric turbulence on the performance of lidar system and BLH detections.In response to these challenges,the main works of this paper are as follows:1.A robust solution for BLH detections with CDWL is proposed and experimentally demonstrated.An intercomparison experiment is designed with two CDWLs,where only one is equipped with a stability control subsystem,thus the BLH result from the stable CDWL can be used as a reference.The carrier-to-noise ratio(CNR)and TKEDR measured by CDWL can be used as tracers.To find the robust solution,the ABL is classified into the mixed layer and the stable boundary layer(residual layer),then a statistical comparison of the BLH results from the two CDWLs is performed.The statistics indicate that MLH is retrieved best from TKEDR,while stable boundary layer height(SBLH)and residual layer height(RLH)can be retrieved from CNR.2.The optimum TKEDR threshold for retrieving MLH is found to be a constant value under different convective weather conditions in the experiments.The turbulence intensity can be characterized by vertical velocity variance or TKEDR.The vertical velocity variance threshold for retrieving MLH varies with convective turbulence intensity.To study the universality of TKEDR threshold,ground-based experiments are conducted at three different sites,including a mid-temperate grassland site,a subtropical urban site,and a tropical marine site.The results indicate that TKEDR threshold does not vary with convective turbulence intensity.After that,by using a ship-borne CDWL,the marine MLH along the ship’s route is successfully detected.3.A dual-frequency coherent Doppler lidar(DF-CDL)is developed.To reduce the interference of atmospheric turbulence on BLH detections,the instrument of DF-CDL is attractive.In this paper,birectional electro-optic phase modulation in a Sagnac loop is employed to generate the dual-frequency laser,and the performance of the lidar system is validated by target velocity detection experiments.Next,the DF-CDL is expected to apply in detecting wind field.