Aerosol retrievals from the ACEPOL Campaign

Abstract

Abstract. In this paper, we present aerosol retrieval results from the ACEPOL (Aerosol Characterization from Polarimeter and Lidar) campaign, which was a joint initiative between NASA and SRON – Netherlands Institute for Space Research. The campaign took place in October-November 2017 over the western part of the United States. During ACEPOL six different instruments were deployed on the NASA ER-2 high altitude aircraft, including four Multi-Angle Polarimeters (MAPs): SPEX airborne, the Airborne Hyper Angular Rainbow Polarimeter (AirHARP), the Airborne Multi-angle SpectroPolarimeter Imager (AirMSPI), and the Research Scanning Polarimeter (RSP). Also, two lidars participated: the High Spectral Resolution Lidar -2 (HSRL-2) and the Cloud Physics Lidar (CPL). Flights were conducted mainly for scenes with low aerosol load over land but also some cases with higher AOD were observed. We perform aerosol retrievals from SPEX airborne, RSP (410–865 nm range only), and AirMSPI using the SRON aerosol retrieval algorithm and compare the results against AERONET and HSRL-2 measurements (for SPEX airborne and RSP). All three MAPs compare well against AERONET for the Aerosol Optical Depth (AOD) (Mean Absolute Error (MAE) between 0.014–0.024 at 440 nm). For the fine mode effective radius the MAE ranges between 0.021–0.028 micron. For the comparison with HSRL-2 we focus on a day with low AOD (0.02–0.14 at 532 nm) over the California Central Valley, Arizona and Nevada (26 October) and a flight with high AOD (including measurements with AOD > 1.0 at 532 nm) over a prescribed forest fire in Arizona (9 November). For the day with low AOD the MAE in AOD (at 532 nm) with HSRL-2 are 0.014 and 0.022 for SPEX and RSP, respectively, showing the capability of MAPs to provide accurate AOD retrievals for the challenging case of low AOD over land. For the retrievals over the smoke plume also a reasonable agreement in AOD between the MAPs and HSRL-2 was found (MAE 0.088 and 0.079 for SPEX and RSP, respectively), despite the fact that the comparison is hampered by large spatial variability in AOD throughout the smoke plume. Also a good comparison is found between the MAPs and HSRL-2 for the aerosol depolarization ratio (a measure for particles sphericity) with MAE of 0.023 and 0.016 for SPEX and RSP, respectively. Finally, SPEX and RSP agree very well for the retrieved microphysical and optical properties of the smoke plume.

Use of A Neural Network-Based Ocean Body Radiative Transfer Model for Aerosol Retrievals from Multi-Angle Polarimetric Measurements

“…Therefore, we used the AOD derived using the assumed lidar ratio, which is more accurate than the one derived using the HSRL method for the low AOD situations investigated here. This AOD product from HSRL-2 was found to agree well with AOD derived from AERONET measurements, with a MAE, bias, standard deviation of 0.028, −0.014 and 0.029 at 355 nm and 0.012, −0.005 and 0.014 at 532 nm [84].…”

“…In this section we presented aerosol retrievals using real data collected during the ACEPOL campaign on 23rd and 25th October, 2017 using the SPEXairborne instrument. For our retrieval using data from the SPEX airborne measurement, we used the same spectral bands as Fu et al [84] between 450 and 750 nm. Here, shorter and longer wavelengths were excluded because of lower data quality at these wavelengths for SPEX airborne.…”

Inversion of multi-angular polarimetric measurements from the ACEPOL campaign: an application of improving aerosol property and hyperspectral ocean color retrievals

“…In order to retrieve aerosol information from polarimetric measurements over the ocean, a number of advanced aerosol retrieval algorithms have been developed for both airborne and spaceborne MAPs, such as POLDER/PARASOL (Hasekamp et al, 2011;Dubovik et al, 2011Dubovik et al, , 2014, AirMSPI (Xu et al, 2016(Xu et al, , 2019, SPEX Airborne (Fu and Hasekamp, 2018;Fu et al, 2019;Fan et al, 2019), RSP (Chowdhary et al, 2005;Wu et al, 2015;Stamnes et al, 2018;Gao et al, 2018Gao et al, , 2019, and Directional Polarimetric Camera (DPC)/GaoFen-5 (Wang et al, 2014;Li et al, 2018). In this study, we use the Multi-Angle Polarimetric Ocean coLor (MAPOL) retrieval algorithm, which is a joint aerosol and water-leaving radiance retrieval algorithm designed with the bio-optical models applicable to both open and coastal waters (Gao et al, 2018(Gao et al, , 2019.…”

“…CC BY 4.0 License. than 750 nm are excluded from our analysis due to a grating order overlap issue in the data (Smit et al, 2019;Fu et al, 2019).…”