Figure 5 10-day forward trajectories beginning on 4 April 1987.
Related Figures (12)
Fig. 1. Basin-scale rawinsonde network (a) and local mesoscale network (b) employed in the Amazon basin during ABLE 2B. Location of the mesoscale network is indicated by the darkened triangle in (a). The temporal variation of major mineral aerosol Aerosol optical thickness values deduced from RSS Degg SANE SEE, INGE SE Aerosols associated with these pulses had rela- tively high concentrations of alkali and alkaline earth elements in the atmospheric mixed layer of the CAB (Talbot et al. 1990). Amazonian soils, however, are highly weathered and exhibit deficits of these elements. This finding suggested a non-local source region for the dust, which Talbot et al. (1990) believe to be the Sahara. Pulses of Saharan dust were also observed at Barbados during ABLE-2b (Talbot etal. 1990). These pulses, with concentrations at the surface reaching 180 ng m~?, appeared at Barbados 1 to 2 days before Saharan dust was seen in the CAB. The temnnral variatian af mainar mineral aerncol Cast Drazu. Ground-based rawinsonde measurements, ob- tained 4 times daily, were made in a basin scale network (1000-1500 km apart) shown in Fig. la. Local meteorological measurements used in this study include rawinsondes from the three corner stations of the mesoscale network in Fig. 1b (approximately 50km spacing) together with rainfall measurements made on the towers at 5m above the canopy. kaenwal ~awhisnl *haxdttenees walime datnned fener Fig. 3. 500 mb streamlines on 17 April 1987 illustrating the West African Subtropical High and associated wind flow across the Atlantic Ocean and into the Amazon Basin. (the volume of air exchanged in 48 h) Fig. 8. Lidar-measured aerosol attenuation coefficient near Barbados on 21 July 1984 (courtesy of E. Browell, personal communication). The dust plume is seen between 1.5 km and 4.2 km. 1989). Our ABLE 1 measurements over the western tropical Atlantic were conducted during summer- time and exhibit minimal influence from African biomass combustion products; a dramatic sea- sonal signal in this source appears in the annual record of aerosol composition at Barbados (Savoie et al., 1989). Thus, Saharan air intrusions into the CAB during the wet season appear to reflect combined chemical inputs from mineral aerosol, sea salt, and possibly biomass burning products. Table 3. Comparison of deposition fluxes (kg ha~! yr~*) of selected trace species associated with intrusions of Saharan dust and precipitation in the Amazonian wet season (December—May) Table 4. Range of values for depositional influx of P and K due to Saharan dust and associated aerosols compared to and expressed as %s of annual internal flux from litterfall and total ecosystem nutrient amount
