THE DYNAMIC OF DUST IN SOUTHERN SOUTH AMERICA: ANALYSIS OF VERTICAL AND HORIZONTAL FLUXES ALONG THE ARID DIAGONAL.

D. GAIERO; L. SIMONELLA; S. GASSÓ; J. ARCE; H. MARELLI ; P. SOSA; R. BECCHIO

Santa Rosa La Pampa

Conferencia; ICAR VII, Internacional Conference on Aeolian Research; 2010

UNLP/INTA

Direct measurements of dust fluxes under natural conditions and the simultaneous monitoring of vertical (VF-pyramidal receptacles) and horizontal (HF-BSNE traps) fluxes are scarce in the literature. Most of our knowledge of the variability and intensity of the Southern South American (SSA) source is primarily based on model simulations. Therefore, there is a growing scientific interest to account with modern dust flux measurements in SSA as it is of significance for regional climatic studies. Compared to VF, HF is 3 orders of magnitude higher at the Patagonian coast and 1 order of magnitude higher at NW Argentina (NWA) and the Pampas. VF at NWA (27 g m-2 y-1) and the Pampas (36 g m-2 y-1), shows a strong association with the seasonal rainfall fluctuation and agrees with recent model estimations of dust deposition for these regions. Also, higher HF occurs during spring-early summer when wind speed (WS) is higher and relative humidity (RH) is lower. At Patagonia both, VF and HF, point toward a similar annual variation indicating higher fluxes during spring-summer according to the increase of the mean monthly WS and the decrease of the mean monthly RH. The mean daily HF estimated at Trelew (from May/04 to May/08) was 1124 g m-2 y-1, which is about 4 times higher compared to the HF estimated for the Pampas (309 g m-2 y-1) and NWA (210 g m-2 y-1). In all the cases maximums HF/VF are reported during dust storms; the highest rates of dust transport were recorded along the Patagonian coast (i.e., maximum 51 g m-2 d-1 at S. Juliàn). Here, the median grain-size of HF fluctuate between 16 to 67 µm (mean=31 µm), contrasting with a range between 12-33 µm (mean=21 µm) measured at NWA and the Pampas. HF obtained in this study are many times higher that the ones estimated by the most recent models. Moreover, having in mind the low efficiency of BSNE devices, our data should be taken as a minimum estimation.