Transport of central American biomass burning smoke aerosols in 1979–2005

Previous studies using the TOMS aerosol index and back trajectory analyses showed that the Central American Biomass Burning (CABB) smoke aerosols are influenced by two prevailing transport regimes: one northward moving across the Gulf of Mexico with the possibility of reaching the U.S., and one westward flowing over the east Pacific Ocean. The relative dominance of these two regimes changes with time, and highly depends on the large-scale synoptic conditions in which the ITCZ and the subtropical height over the western Atlantic ocean are presumably important players. To date, it is still not clear how the interplay between the ITCZ and the subtropical height would affect the transport and distribution of CABB smoke aerosols, particularly when the impact of El Nino is considered. The abnormal dryness in Central America in May 1998 was coincident with an El Nino event. The CABB smoke particles produced in this time period were mainly transported northward, and the amount was far above normal. This seems to support the hypothesis that El Nino can lead to more CABB smoke aerosol being transported to U.S. which in turn affects the regional climate. Using the TOMS aerosol index from 1979 through 2005, AVHRR aerosol optical thickness from 1983 - 2001, GOES and MODIS fire products from 2001 - 2005, as well as the NCEP/NCAR precipitation and meteorology reanalysis data from 1979 - 2005, we perform various statistical analyses to test the validity of this hypothesis, and investigate possible linkages of ITCZ and subtropical height with the regional climate in the southern U.S. through the transport of CABB aerosols.