Aerosol profiling using radiometric and polarimetric spectral measurements in the O2 A-band

Aerosols are deleterious to both human and ecosystem health, causing premature deaths and crop losses worldwide each year. Starting with the 2017 Earth Science Decadal Survey, the air quality community has been seeking accurate aerosol measurements in the near surface layer (0 to 2 km) over megacities, where air quality strongly influences human health and economic prosperity. Both in-situ and lidar remote sensing techniques provide current-state-of-the-art aerosol measurements; however, the spatial coverage of these measurements is limited.

Recently, the CLARS-FTS (California Laboratory for Atmospheric Remote Sensing - Fourier Transform Spectrometer) instrument has acquired a new capability for the simultaneous measurement of radiometric and polarimetric spectra with a high spectral resolution of (~0.24 cm^-1) across the oxygen A-band, using sunlight reflected from the land surface as a light source. The CLARS-FTS is deployed on top of Mt. Wilson (1.67 km a.s.l.), overlooking the Los Angeles basin, providing measurements with a spatial resolution of 100-200 m. The CLARS site has a nearly unobstructed view of the entire Los Angeles (LA) basin, permitting the spatial mapping of aerosols.

Here, we present methodologies for the radiative transfer modeling and retrieval of aerosol vertical distribution and other optical/microphysical properties using CLARS-FTS measurements over the LA basin. We will also provide the retrieval characteristics and evaluation using reference data. These instrumental and algorithmic tools will quantify the aerosols' spatial-temporal distribution over the LA basin, thus helping to constrain process-based air quality models. These results provide an improved mechanistic understanding of air pollution and its impact on health and economic prosperity, and will assist in the development of the temporal-spatial measurement strategies over megacities.