Atmos. Chem. Phys. Discuss., 10, 18879-18917, 2010
www.atmos-chem-phys-discuss.net/10/18879/2010/
doi:10.5194/acpd-10-18879-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
A decadal regional and global trend analysis of the aerosol optical depth using a data-assimilation grade over-water MODIS and Level 2 MISR aerosol products
J. Zhang1 and J. S. Reid2
1Department of Atmospheric Science, University of North Dakota, Grand Folks, ND, USA
2Marine Meteorology Division, Naval Research Laboratory, Monterey, CA, USA

Abstract. Using the ten-year (2000–2009) DA quality Terra MODIS and MISR aerosol products, as well as 7 years of Aqua MODIS, we studied both regional and global aerosol trends over oceans. This included both natural and data assimilation grade versions of the products. Contrary to some of the previous studies that showed a decreasing trend in aerosol optical depth (AOD) over global oceans, after correcting for what appears to be aerosol signal drift from the radiometric calibration of both MODIS instruments, we found MODIS and MISR agreed on a statistically negligible global trend of 0.0003/per year. Our study also suggests that AODs over the Indian Bay of Bengal, east coast of Asia, and Arabian Sea show statistically significant increasing trends of 0.07, 0.06, and 0.06 per ten years for MODIS, respectively. Similar increasing trends were found from MISR, but with less relative magnitude. These trends reflect respective increases in the optical intensity of aerosol events in each region: anthropogenic aerosols over the east coast of China and Indian Bay of Bengal; and a stronger influence from dust events over the Arabian Sea. Negative AOD trends are found off Central America, the east coast of North America, and the west coast of Africa. However, confidence levels are low in these regions, which indicate that longer periods of observation are necessary to be conclusive.

Citation: Zhang, J. and Reid, J. S.: A decadal regional and global trend analysis of the aerosol optical depth using a data-assimilation grade over-water MODIS and Level 2 MISR aerosol products, Atmos. Chem. Phys. Discuss., 10, 18879-18917, doi:10.5194/acpd-10-18879-2010, 2010.
 
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