Improving Daytime Planetary Boundary Layer Height Determination from CALIOP: Validation Based on Ground-Based Lidar Station

Zhao Liu,Augustin Mortier,Weizhen Hou,Yisong Xie,Philippe Goloub,Yang Lv,Kaitao Li,Xingfeng Chen,Zhengqiang Li,Donghui Li

doi:10.1155/2017/5759074

Abstract

An integrated algorithm by combining the advantages of the wavelet covariance method and the improved maximum variance method was developed to determine the planetary boundary layer height (PBLH) from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements, and an aerosol fraction threshold was applied to the integrated algorithm considering the applicability of the two methods. We compared the CALIOP retrieval with the measurements of PBLH derived from nine years of ground-based Lidar synchronous observations located in Lille, north of France. The results indicate that a good correlation (R≥0.79) exists between the PBLHs derived from CALIOP and ground-based Lidar under clear sky conditions. The mean absolute differences of PBLHs are, respectively, of 206 m and 106 m before and after the removal of the aloft aerosol layer. The results under cloudy sky conditions show a lower agreement (R=0.48) in regard of the comparisons performed under clear sky conditions. Besides, the spatial correlation of PBLHs decreases with the increasing spatial distance between CALIOP footprint and Lille observation platform. Based on the above analysis, the PBLHs can be effectively derived by the integrated algorithm under clear sky conditions, while larger mean absolute difference (i.e., 527 m) exists under cloudy sky conditions.

Highlights

The planetary boundary layer (PBL) is part of the earth’s atmosphere, which is directly influenced by the earth’s surface
An integrated algorithm by combining the advantages of the wavelet covariance method and the improved maximum variance method was developed to determine the planetary boundary layer height (PBLH) from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements, and an aerosol fraction threshold was applied to the integrated algorithm considering the applicability of the two methods
We compared the CALIOP retrieval with the measurements of PBLH derived from nine years of ground-based Lidar synchronous observations located in Lille, north of France

Summary

Introduction

The planetary boundary layer (PBL) is part of the earth’s atmosphere, which is directly influenced by the earth’s surface. With the development of active remote sensing technique, the space-borne Lidar can provide global observations of aerosol vertical distributions, which makes it possible to estimate the PBLH from space-based Lidar. This work presents a new algorithm, based on the maximum variance technique developed by Jordan et al [24], with improved preliminary detection of the sharp gradients that are nonrelated to the PBL The validation of this method relies on comparisons with PBLH derived from nine years of ground-based Lidar synchronous observations located in Lille, north of France. Two types of data were chosen for the retrieval of PBL heights: (1) total attenuated backscatter at 532 nm from Level 1B data, which has a horizontal resolution of 333 m and a vertical resolution of 30 m from −0.5 km to 8.2 km, and (2) Level 2 Vertical Feature Mask (VFM) that contains the information of classification of cloud and aerosol and their subtypes. For consistency purposes with the Lidar wavelength, AOD were interpolated at 532 nm from 440 and 870 nm channels

Methods

Results

Conclusions