A height resolved global view of dust aerosols from the first year CALIPSO lidar measurements

Abstract

Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resolved global distribution of dust aerosols is presented for the first time. Results indicate that spring is the most active dust season,, during which ∼20% and ∼12% of areas between 0 and 60°N are influenced by dust at least 10% and 50% of the time, respectively. In summer within 3-6 km, ∼8.3% of area between 0 and 60°N is impacted by dust at least 50% of the time. Strong seasonal cycles of dust layer vertical extent are observed in major source regions, which are similar to the seasonal variation of the thermally driven boundary layer depth. The arid and semiarid areas in North Africa and the Arabian Peninsula are the most persistent and prolific dust sources. African dust is transported across the Atlantic all yearlong with strong seasonal variation in the transport pathways mainly in the free troposphere in summer and at the low altitudes in winter. However, the trans-Atlantic dust is transported at the low altitudes is important for all seasons, especially transported further cross the ocean. The crossing Atlantic dusty zones are shifted southward from summer to winter, which is accompanied by a similar southward shift of dust-generating areas over North Africa. The Taklimakan and Gobi deserts are two major dust sources in East Asia with long-range transport mainly occurring in spring. The large horizontal and vertical coverage of dust aerosols indicate their importance in the climate system through both direct and indirect aerosol effects. Copyright 2008 by the American Geophysical Union.