High-Resolution Image

The 8 year global mean aerosol optical depth at 0.55 µm as observed by the MODIS sensor aboard the Terra satellite shows the global aerosol system that we have come to expect. We see high aerosol regions over northern and central Africa, southern and eastern Asia, parts of south and central America, and oceanic regions down wind of these "hot spots". Note that the standard MODIS algorithm does not retrieve over bright surfaces and thus no data is displayed over deserts, Greenland or Antarctica. Also annual mean values at high latitude are biased to the seasons of the year with no snow cover, and that there is an overall bias towards cloud free conditions.

The second plot shows how the 2007 annual mean AOD from MODIS deviated from the 8-year mean picture. Biomass burning in South America was particularly strong in 2007 and transport from the deforestation zone at 0 - 10 degrees south latitude spread smoke southward to the coastal areas of Uruguay and northern Argentina at anomalous levels. On the other hand, biomass burning smoke in Indonesia, particularly the island of Borneo was anomalously low as compared to the 8-year mean, as was smoke in central Africa. The plot also shows lower than "normal" aerosol at high boreal latitudes indicating that 2007 was not a strong year for boreal fire smoke.

Eastern China stands out as a strong positive anomaly in 2007, exhibiting higher annual mean AOD than even its already high 8-year mean. India shows a slightly positive anomaly, as does the Sahelian west Africa. For most other land areas, 2007 turned out to be similar to conditions represented by the 8-year mean, or in the case of northern Eurasia, lower.

Most of the open ocean failed to exhibit annual mean AOD deviations by more than 0.02 in AOD. However areas of the ocean that are usually dominated by outflow of dust from Africa and the Saudi Arabian Peninsula in certain seasons were higher than normal.

Submitted by Richard Kleidman (SSAI), Lorraine Remer (NASA/GSFC) and Shana Mattoo (SSAI).