Validation of MODIS aerosol optical depth retrieval over land

TLDR

Aerosol optical depths are derived operationally for the first time from MODIS measurements over vegetated and partially vegetated land at 0.47 and 0.66 µm wavelengths, but the lack of AERONET measurements in East Asia, India and Australia limits validation in those regions. The validation covered July–September 2000, comparing 315 co‑located MODIS and AERONET τa from over 30 sites. MODIS aerosol retrievals are within retrieval errors of Δτa = ±0.05 ± 0.2 τa, with RMS errors ≤ 0.1 in continental inland regions and up to 0.3 in coastal regions, indicating that MODIS aerosol products can be used quantitatively in many applications with caution for residual clouds, snow/ice, and water contamination.

Abstract

Aerosol optical depths (τ a ) are derived operationally for the first time from the MODIS (Moderate Resolution Imaging Spectroradiometer) measurements over vegetated and partially vegetated land at 0.47 and 0.66 μm wavelengths. The extensive validation made during July – September 2000 encompasses 315 co‐located τ a in space and time derived by MODIS and AERONET (Aerosol Robotic Network) from more than 30 AERONET sites. The lack of AERONET measurements in East Asia, India and Australia makes this validation unavailable for those regions. The MODIS aerosol retrievals, except in coastal zones, are found within the retrieval errors of Δτ a = ±0.05 ±0.2 τ a . The root mean square (RMS) errors are ≤ 0.1 in the continental inland regions and up to 0.3 in the coastal regions (attributed mainly to water contaminated signals). With this validation we believe that MODIS aerosol products can be used quantitatively in many applications with caution for possible residual clouds, snow/ice, and water contamination.