Dr. Jun Wang

Diurnal Change of Aerosols Optical Thickness in East Asia Retrieved from

Geostationary Meteorology Satellite (GMS)

Reference: Wang, J., S.A. Christopher, F. Brechtel, J. Kim, B. Schmid, J. Redemann, P.B. Russell, P. Quinn, and B.N. Holben, Geostationary Satellite Retrievals of Aerosol Optical Thickness during ACE-Asia, J. Geophys. Res., 108 (23), doi:10.1029/2003JD003580, 2003. (pdf file).

Observations show that dust aerosols from the Takla Makan and Gobi deserts in northwest China can be transported to Korea , and even across the Pacific Ocean to the United States [Husar et al., 2001, Herman et al., 1997] and Canada [McKendry et al., 2001].  Due to rapid economic growth, the emission of industrial pollutants has increased in the East Asian regions [Bergin et al., 2001].   The aerosols in this region include sulfate, dust, soot and sea salt, in a highly mixed condition, producing a complex aerosol loading in the troposphere.   Some studies have shown that aerosols might be an important factor for the regional cooling in the Sichuan basin in Southern China [Luo et al., 2001; Li et al., 1995] and drought in northern China [Menon et al., 2002].

Since there are few observations available over the oceans, satellite measurements, due to their large spatial coverage (e.g, polar-orbit satellite) and high temporal resolution (e.g., geostationary satellite), provide a unique tool for quantifying aerosol properties and spatial distributions.  However, to reliably retrieve aerosol properties from satellite measurements, ground and aircraft measurements are needed to constrain the satellite retrieval processes and validate the satellite results.  This study demonstrates such a strategy, with emphasis on estimating the day-time diurnal change of aerosol radiative forcing, by using geostationary satellite data and other measurements during the ACE-Asia Intensive Observation Period (IOP), April 01-April 30, 2001. ACE-Asia was conducted off the coast of East China, Korea, and Japan from late March to early May 2001.  A detailed description of this campaign is given by Huebert et al [2003].  In contrast with the time-invariant aerosol models used in previous satellite retrieval studies [e.g., Wang et al., 2003; Rao et al., 1989], aerosol properties in this study are calculated as a function of space and time (called the dynamic aerosol model) by incorporating an aerosol climatology for East Asia as well as observed aerosol properties from ground and in-situ measurements during ACE-Asia.  The detailed description of the retrieval method and validations of the retrieval algorithms can be found in the reference listed above. The following is the case demo of our AOT product.

Time series of Aerosol Optical Thickness (AOT) Retrieved from GMS satellite during ACE-Asia.  The following images show a dust front propagating from the east coast of China to the west Pacific and  industry pollutants in the east coast of Korea and Japan.  The high-temporal resolution capability of GMS satellite provides opportunities to study the dynamic transport and the radiative effects of pollutions in more detailed spatial-temporal scale.  Recall there is very few measurements over the ocean, and the polar-orbiting satellite only revisit the same area once per day.  But for most dust events, its temporal scale is in unit of hours. As shown in the following, the dust AOT can be doubled in only several hours.