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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D07308, doi:10.1029/2004JD005208, 2005

Evaluation of aerosol properties over ocean from Moderate Resolution Imaging Spectroradiometer (MODIS) during ACE-Asia

D. A. Chu

Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA


L. A. Remer

Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


Y. J. Kaufman

Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


B. Schmid

NASA Ames Research Center, Moffett Field, California, USA


J. Redemann

NASA Ames Research Center, Moffett Field, California, USA


K. Knobelspiesse

Science Systems and Applications, Inc., Lanham, Maryland, USA


J.-D. Chern

Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


J. Livingston

NASA Ames Research Center, Moffett Field, California, USA


P. B. Russell

NASA Ames Research Center, Moffett Field, California, USA


X. Xiong

Laboratory for Terrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


W. Ridgway

Science Systems and Applications, Inc., Lanham, Maryland, USA


Abstract

The Aerosol Characterization Experiment-Asia (ACE-Asia) was conducted in March–May 2001 in the western North Pacific in order to characterize the complex mix of dust, smoke, urban/industrial pollution, and background marine aerosol that is observed in that region in springtime. The Moderate Resolution Imaging Spectroradiometer (MODIS) provides a large-scale regional view of the aerosol during the ACE-Asia time period. Focusing only on aerosol retrievals over ocean, MODIS data show latitudinal and longitudinal variation in the aerosol characteristics. Typically, aerosol optical depth (τ a ) values at 0.55 μm are highest in the 30°–50° latitude band associated with dust outbreaks. Monthly mean τ a in this band ranges ∼0.40–70, although large differences between monthly mean and median values indicate the periodic nature of these dust outbreaks. The size parameters, fine mode fraction (η), and effective radius (r eff ) vary between monthly mean values of η = 0.47 and r eff = 0.75 μm in the cleanest regions far offshore to approximately η = 0.85 and r eff = 0.30 μm in near-shore regions dominated by biomass burning smoke. The collocated MODIS retrievals with airborne, ship-based, and ground-based radiometers measurements suggest that MODIS retrievals of spectral optical depth fall well within expected error (Δτ a = ±0.03 ± 0.05τ a ) except in situations dominated by dust, in which cases MODIS overestimate both the aerosol loading and the aerosol spectral dependence. Such behavior is consistent with issues related to particle nonsphericity. Comparisons of MODIS-derived r eff with AERONET retrievals at the few occurrences of collocations show MODIS systematically underestimates particle size by 0.2 μm. Multiple-year analysis of MODIS aerosol size parameters suggests systematic differences between the year 2001 and the years 2000 and 2002, which are traced to instrumental electronic cross talk. Sensitivity studies show that such calibration errors are negligible in τ a retrievals but are more pronounced in size parameter retrievals, especially for dust and sea salt.

Received 7 July 2004; accepted 11 January 2005; published 9 April 2005.

Keywords: aerosol properties; remote sensing; characterization.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 3360 Atmospheric Processes: Remote sensing; 4801 Oceanography: Biological and Chemical: Aerosols (0305, 4906).

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Citation: Chu, D. A., et al. (2005), Evaluation of aerosol properties over ocean from Moderate Resolution Imaging Spectroradiometer (MODIS) during ACE-Asia, J. Geophys. Res., 110, D07308, doi:10.1029/2004JD005208.