Hourly Mapping of the Layer Height of Thick Smoke Plumes Over the Western U.S. in 2020 Severe Fire Season

Abstract

A series of huge smoke plume events from the largest wildfire season recorded in California’s modern history has occurred in 2020. Here, a research algorithm was modified to retrieve the aerosol optical centroid height (AOCH) and aerosol optical depth (AOD) from Earth Polychromatic Imaging Camera (EPIC) measurements. The research focus is to gain insights of the algorithm’s feasibility in heavy smoke conditions to study the diurnal variation of AOCH; this is only made possible via EPIC due to its unique position at Lagrange-1 point and its equipment of O2 B-band at which the vegetated surface reflectance is low. Vicarious calibration is applied to the EPIC 443, 680 and 688 nm channels based on the Tropospheric Monitoring Instrument (TROPOMI) observation. This new calibration leads to a better agreement of AOCH values between EPIC retrievals and the counterparts derived from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol extinction vertical profile. The hourly variation of AOCH up to 0.45 km on September 7 is shown to have important implications for estimating hourly change of surface PM2.5, although more quantitative studies are needed in the future.

Aerosol layer height (ALH) retrievals from oxygen absorption bands: Intercomparison and validation among different satellite platforms, GEMS, EPIC, and TROPOMI

“…EPIC and TROPOMI defined their retrieved ALH as H in Eq. ( 1) and called AOCH (Chen et al, 2021b;Lu et al, 2023;Lu et al, 2021;Xu et al, 2019;Xu et al, 2017). GEMS defines its ALH retrieval as AEH, the altitude above which the aerosol extinction is the 1/e of total columnar AOD, as described in Eq.…”

“…Henceforth, for simplicity and consistency, the term ALH will be used to refer to all aerosol height products used in this study, including GEMS AEH, TROPOMI AOCH, and EPIC AOCH. To validate retrievals from passive remote sensing with lidar data, the extinction weighted heights derived from CALIOP 5 km level 2 aerosol extinction profile product at 532 nm following previous studies are used (Chen et al, 2021b;Lu et al, 2023;Lu et al, 2021;Xu et al, 2019).…”

Reply on RC1

“…EPIC and TROPOMI defined their retrieved ALH as H in Eq. ( 1) and called AOCH (Chen et al, 2021b;Lu et al, 2023;Lu et al, 2021;Xu et al, 2019;Xu et al, 2017). GEMS defines its ALH retrieval as AEH, the altitude above which the aerosol extinction is the 1/e of total columnar AOD, as described in Eq.…”

Reducing Aerosol Forcing Uncertainty by Combining Models With Satellite and Within‐The‐Atmosphere Observations: A Three‐Way Street

“…Although coverage by these measurements is currently limited, their precision has demonstrated value in constraining and/or validating models aimed at simulating downwind wildfire smoke and volcanic ash dispersion (e.g., Vernon et al., 2018; L. Zhu, Val Martin, et al., 2018). A number of satellite‐based, passive‐imager spectral techniques, at wavelengths ranging from the ultraviolet (UV) to the infrared, offer greater aerosol layer‐height coverage, at the cost of additional assumptions that increase uncertainty (e.g., Go et al., 2020; Griffin et al., 2020; Jeong & Hsu, 2008; Kylling et al., 2018; Lu et al., 2021; Lyapustin et al., 2020). Passive‐imager techniques, especially in UV channels, have also been effective in constraining aerosol occurrence, and even amount, over cloudy scenes (e.g., Meyer et al., 2015; Sayer et al., 2019; Torres et al., 2012).…”