Arrange and Average Algorithm for Microphysical Retrievals with A “3β+3α” Lidar Configuration

Eduard Chemyakin,Detlef Müller,Richard Ferrare,Chris Hostetler,Sharon Burton

doi:10.1051/epjconf/201611923026

Abstract

We present the results of a comparison study in which a simple, automated, and unsupervised algorithm, which we call the arrange and average algorithm, was used to infer microphysical parameters (complex refractive index (CRI), effective radius, total number, surface area, and volume concentrations) of atmospheric aerosol particles. The algorithm normally uses backscatter coefficients ( β ) at 355, 532, and 1064 nm and extinction coefficients ( α ) at 355 and 532 nm as input information. We compared the performance of the algorithm for the existing “3 β +α” and potential “3 β +3α” configurations of a multiwavelength aerosol Raman lidar or highspectral-resolution lidar (HSRL). The “3 β +3α” configuration uses an extra extinction coefficient at 1064 nm. Testing of the algorithm is based on synthetic optical data that are computed from prescribed CRIs and monomodal logarithmically normal particle size distributions that represent spherical, primarily fine mode aerosols. We investigated the degree to which the microphysical results retrieved by this algorithm benefits from the increased number of input extinction coefficients.

Highlights

Aerosol particles affect the radiative energy balance in the atmosphere and influence Earth’ s climate [1]
The left vertical axis of each plot shows the number of cases that were tested [10]
The histogram displays the statistical distribution of errors of the retrieved microphysical parameters

Summary

Introduction

Aerosol particles affect the radiative energy balance in the atmosphere and influence Earth’ s climate [1]. E.g., sea salt, desert dust, smoke from biomass burning, and emissions from the burning of fossil fuel, influence regional and global climate through the direct and indirect radiative effect, which may result in net cooling or net warming of the air, changes of the large-scale atmospheric circulation, cloud lifetime and occurrence, and intensity of precipitation [1]. We have not seen yet any publication stating that the extinction coefficient at 1064 nm was successfully measured using Raman or HSRL technology but the “3β+3α” configuration is still possible via combination of lidar and column measurements of the atmospheric optical depth at 1064 nm We investigated if this extra extinction coefficient could have a significant effect on the retrieval accuracy of microphysical properties

Objectives

Methods

Results

Conclusion