Ground-based Remote Sensing of the Williams Flats Fire Using Mobile AERONET DRAGON Measurements and Retrievals during FIREX-AQ

The AERONET Distributed Regional Aerosol Gridded Network (DRAGON) networks of sun/sky/moon scanning spectral radiometers augment stationary sites to capture the regional dynamics of aerosol properties due to topographic forcing in a variety of mountainous regimes and land cover types during the 2019 FIREX-AQ campaign. Notably, two Mobile AERONET DRAGON vehicle-based lidars and radiometers (one Cimel CE318-T and one PLASMA) were dispatched closer to smoke plumes. The ground-based mobile AERONET DRAGON teams provided total column measurements of aerosol characteristics as well as the vertical distribution of aerosols and clouds using Cimel lidar. Some AERONET Version 3 algorithm cloud screening and quality control methods apply only to stationary CE318 measurements, as a result, the algorithm and processing was adapted and optimized for mobile instruments.

The AERONET DRAGON mobile deployment for the Williams Flats fire occurred from August 4 to August 8, 2019, and these data were analyzed to assess aerosol loading, particle size, and particle absorption in and near the Williams Flats Fire plume. For the measurement period, Angstrom exponent (AE, 440-870nm) values computed between 2.0 to 2.4 generally correspond to high aerosol optical depth (AOD) at 440nm values greater than 0.5 suggesting very small particles in the more opaque portion of the smoke plumes near the fire source. Close to the fire, AOD 440nm values varied widely from 0.1 to 2.7 and AE ranged significantly from 1.4-2.4. However, observations of high AOD more than 75 km downwind of the Williams Flats fire have more stable AE values ranging from 1.65 to 1.8 suggesting consistently larger smoke particles possibly due to aggregation and aging of the smoke particles. Retrievals performed using the hybrid sky scan scenario from the CE318-T similarly show decreasing effective fine mode radius with increasing fine mode volume concentration. Further, hybrid single scattering albedo retrievals decrease with increasing wavelength suggesting spectral aerosol absorption consistent with biomass burning smoke. This presentation will provide discussion on the adaptation of the Version 3 algorithm to mobile sun photometer measurements and the characterization of AERONET measurements and retrievals of Williams Flats Fire smoke plume.