Mathematics – Logic
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.p14a..03b&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #P14A-03
Mathematics
Logic
3322 Land/Atmosphere Interactions, 1809 Desertification, 1625 Geomorphology And Weathering (1824, 1886), 1640 Remote Sensing, 0305 Aerosols And Particles (0345, 4801)
Scientific paper
Mineral aerosols (desert dust) interact with global climate and biogeochemistry. Recent research has suggested that the most significant sources of mineral aerosols are associated with topographic lows in drylands that contain contemporary or old ephemeral lakes, and that complex relationships may exist between surface water, hydrology and these desert dust sources. Most mineral aerosol emissions are observed in the northern hemisphere. Here, the identification of key processes acting within the dust source areas using remote sensing is far from straightforward; and currently inconclusive. This has implications for the generation and testing of dust emission models, and for estimating the relative impacts of natural and anthropogenic dust emission processes. In the southern hemisphere, dust emissions from a range of relatively discrete dust sources, centred on contemporary ephemeral lake basins, may provide an opportunity to constrain some of the emission processes and forcing mechanisms at regional scales. Research here involves the study of processes occurring within the dust source areas of southern Africa, southern America, and Australia. Using time-series of monthly TOMS, AVHRR, gridded climate data, surface climate data, and occasional gauged hydrological inputs, the relationship between dust emissions and surface processes have been investigated for a 20-year period (1982-2002) for large ephemeral lakes. The sources investigated were: (i) Etosha Pan, Namibia (location: 16oE, 18oS: area c.4800km2), (ii) The Makgadikgadi Pans, Botswana (location: 21oS, 26oE; area c.4480km2 (Ntwetwe Pan) and c.1116 km2 (Sua pan), (iii) Lake Eyre, Australia (location 27oS 137oE, area c.9300km2) and (iv) Salar de Uyuni (area c.10580km2) and Salar de Coipasa (area c.2220km2) located at approx. 20oS 67oW in Bolivia. For most of these lakes, findings show a significant relationship between anomalies in TOMS AI and the timing/extent of inundation; confirming a link between each ephemeral lake basin and the TOMS dust plumes, and giving a clear indication of dust emission processes acting in each basin. In particular, significant inflows and inundation events in most of these basins are associated with La Nina episodes, and these events lead to significant negative TOMS anomalies over long time-periods; primarily due to raised groundwater levels and increased vegetation abundance. El Nino periods generally equate to periods of low inflows, a reduction in groundwater level, and greater likelihood of positive TOMS anomalies. This research suggests that the large southern hemisphere ephemeral lake basins are significant regional dust sources, and that an appreciation of their hydrological dynamics is essential for understanding/modelling global dust emissions from drylands.
Bryant Robert G.
Eckardt F.
Mahowald Natalie M.
Ross Simon
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