Multiangle implementation of atmospheric correction (MAIAC): 2. Aerosol algorithm

TLDR

MAIAC is a generic MODIS atmospheric correction algorithm that retrieves aerosols over dark vegetated surfaces and bright deserts using time‑series analysis and image‑based processing. This study introduces an aerosol component of a new multi‑angle implementation of MAIAC. MAIAC’s look‑up tables incorporate surface bidirectional reflectance, and the aerosol algorithm derives a spectral regression coefficient linking blue (0.47 µm) and SWIR (2.1 µm) bands, yielding 1 km aerosol optical thickness and fine‑mode fraction products. Validation with AERONET shows MAIAC matches MOD04 accuracy over vegetated surfaces and improves accuracy over bright surfaces, providing high‑resolution aerosol information for air‑quality studies and enabling retrievals over bright deserts such as the Solar Village site in Saudi Arabia.

Abstract

[1] An aerosol component of a new multiangle implementation of atmospheric correction (MAIAC) algorithm is presented. MAIAC is a generic algorithm developed for the Moderate Resolution Imaging Spectroradiometer (MODIS), which performs aerosol retrievals and atmospheric correction over both dark vegetated surfaces and bright deserts based on a time series analysis and image-based processing. The MAIAC look-up tables explicitly include surface bidirectional reflectance. The aerosol algorithm derives the spectral regression coefficient (SRC) relating surface bidirectional reflectance in the blue (0.47 μm) and shortwave infrared (2.1 μm) bands; this quantity is prescribed in the MODIS operational Dark Target algorithm based on a parameterized formula. The MAIAC aerosol products include aerosol optical thickness and a fine-mode fraction at resolution of 1 km. This high resolution, required in many applications such as air quality, brings new information about aerosol sources and, potentially, their strength. AERONET validation shows that the MAIAC and MOD04 algorithms have similar accuracy over dark and vegetated surfaces and that MAIAC generally improves accuracy over brighter surfaces due to the SRC retrieval and explicit bidirectional reflectance factor characterization, as demonstrated for several U.S. West Coast AERONET sites. Due to its generic nature and developed angular correction, MAIAC performs aerosol retrievals over bright deserts, as demonstrated for the Solar Village Aerosol Robotic Network (AERONET) site in Saudi Arabia.