Comment on amt-2021-307

doi:10.5194/amt-2021-307-rc1

Abstract

Aerosols emitted from wildfires are becoming one of the main sources of poor air quality in the US mainland. Their extinction in UVB (wavelength range 280–315 nm) is difficult to be retrieved using simple lidar techniques because of the impact of O3 absorption and lacking information of lidar ratio at those wavelengths. The 2018 Long Island Sound Tropospheric Ozone Study (LISTOS) campaign in the New York City region allowed the characterization of lidar ratio for UVB aerosol retrieval. An algorithm for the aerosol extinction retrieval out of the Langley Mobile Ozone Lidar (LMOL) was used in conjunction with the NASA Langley High Altitude Lidar Observatory (HALO) 532 nm aerosol extinction product. This approach requires assuming 2 parameters, the lidar ratio at 292 nm and the Ångström Exponent (AE) between 532 nm and 292 nm. The objective of this work is to determine these two parameters and assess the retrieval error caused by improper assumption of lidar ratio. This work also accomplishes the first know 292 nm aerosol product inter-comparison between HALO and Tropospheric Ozone Lidar Network (TOLNet) ozone lidar. HALO results were compared with the aerosol data retrieved from the 292 nm band from LMOL with different approximations of the lidar ratio and the AE to determine optimal parameters. Using optimized parameters, the LMOL aerosol extinction can be retrieved with a 10 % accuracy up to 3 km. This work highlights the importance of the lidar ratio and AE in the retrieval and validation of 292 nm aerosol profiles obtained from UV-lidar. Errors arise from approaches that utilize a random priori lidar ratio and AE assumption. The lidar ratios at 292 nm determined in this work will also improve our understanding of the UVB optical properties of aerosol in the lower troposphere affected by transported wildfire emission.

Highlights

Wildfires produce substantial amounts of gaseous pollutants such as carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), and ozone (O3) as well as biomass burning particulate which significantly impact the climate and 35 air quality (Andreae and Merlet, 2001; Phuleria et al, 2005; Reid et al, 2005; Zauscher et al, 2013)
6 Conclusion For the first time, the aerosol extinction coefficient profile was retrieved from the Langley Mobile Ozone Lidar (LMOL) 292nm attenuated backscatter using the Fernald algorithm are compared with airborne High Altitude Lidar Observatory (HALO) data
A partial aerosol optical depth (AOD) difference method was introduced to determine 360 the optimized value for 292 nm S@ and AE between 292 nm and 532 nm which will be used for the LMOL 292 nm aerosol extinction retrieval

Summary

Introduction

Wildfires produce substantial amounts of gaseous pollutants such as carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), and ozone (O3) as well as biomass burning particulate which significantly impact the climate and 35 air quality (Andreae and Merlet, 2001; Phuleria et al, 2005; Reid et al, 2005; Zauscher et al, 2013). We try to retrieval aerosol extinction at 292 nm from the UV-lidar in this work to improve our understanding of the impact of transported wildfire emission on air quality and the aerosol optical properties in UVB band. Kuang et al (2020) demonstrated retrieval of aerosol 299 nm backscatter from the ozone lidar raw attenuated backscatter signal using an iteration algorithm and fixed lidar ratio (60 sr) in the presence of smoke. It will introduce uncertainty 55 for the aerosol retrieval if we use one lidar ratio value for aerosol with different type because the lidar ratio for different aerosol type varies a lot (Omar et al, 2009; Lopes et al, 2013, Müller et al, 2007; Burton et al, 2014; Haarig et al, 2018). As figure s1 shows, the HALO and LMOL will have coincident measurement when the HALO overpass the LMOL

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