Effects of systematic and random errors on the retrieval of particle microphysical properties from multiwavelength lidar measurements using inversion with regularization

D Pérez-Ramírez,I Veselovskii,D N Whiteman,L Alados-Arboledas,A Kolgotin,M Korenskiy

doi:10.5194/amt-6-3039-2013

Abstract

Abstract. In this work we study the effects of systematic and random errors on the inversion of multiwavelength (MW) lidar data using the well-known regularization technique to obtain vertically resolved aerosol microphysical properties. The software implementation used here was developed at the Physics Instrumentation Center (PIC) in Troitsk (Russia) in conjunction with the NASA/Goddard Space Flight Center. Its applicability to Raman lidar systems based on backscattering measurements at three wavelengths (355, 532 and 1064 nm) and extinction measurements at two wavelengths (355 and 532 nm) has been demonstrated widely. The systematic error sensitivity is quantified by first determining the retrieved parameters for a given set of optical input data consistent with three different sets of aerosol physical parameters. Then each optical input is perturbed by varying amounts and the inversion is repeated. Using bimodal aerosol size distributions, we find a generally linear dependence of the retrieved errors in the microphysical properties on the induced systematic errors in the optical data. For the retrievals of effective radius, number/surface/volume concentrations and fine-mode radius and volume, we find that these results are not significantly affected by the range of the constraints used in inversions. But significant sensitivity was found to the allowed range of the imaginary part of the particle refractive index. Our results also indicate that there exists an additive property for the deviations induced by the biases present in the individual optical data. This property permits the results here to be used to predict deviations in retrieved parameters when multiple input optical data are biased simultaneously as well as to study the influence of random errors on the retrievals. The above results are applied to questions regarding lidar design, in particular for the spaceborne multiwavelength lidar under consideration for the upcoming ACE mission.

Highlights

The importance of atmospheric aerosol particles on Earth’s climate and on environmental problems is widely recognized
The Nd:YAG laser has been used as the transmitter for multiwavelength Raman lidar systems (MW), which have permitted the retrieval of the profile of aerosol microphysical properties (e.g., Müller et al, 2001, 2004, 2005, 2011; Wandinger et al, 2002; Böckman et al, 2005; Noh et al, 2009; Balis et al, 2010; Alados-Arboledas et al, 2011; Tesche et al, 2011; Veselovskii et al, 2012; Papayannis et al, 2012; Wagner et al, 2013; Navas-Guzmán et al, 2013)
We have presented the results of a study of the sensitivity of the retrievals of aerosol physical parameters using the regularization technique to systematic and random uncertainties in the input optical data

Summary

Introduction

The importance of atmospheric aerosol particles on Earth’s climate and on environmental problems is widely recognized. D. Pérez-Ramírez et al.: Errors of microphysical particle retrievals from 3β + 2α lidar measurements occurring in the atmosphere (Eck et al, 2010) and aerosol dynamics (e.g., Pérez-Ramírez et al, 2012). Müller et al (2001, 2004, 2005) and Veselovskii et al (2002, 2004) demonstrated the capability of the regularization technique to retrieve aerosol microphysical properties from a lidar system that provides just five optical signals using a tripled Nd:YAG laser. The aim of this work, is to study the sensitivity of microphysical retrievals by the regularization technique to systematic variations in the input optical data provided by the 3β + 2α lidar configuration.

Inversion technique

Size distribution for the simulations

Effects on the retrievals of systematic errors in the optical data

Findings

Summary and conclusions