Anomalies in moisture sources and sinks associated to the severe central United States drought in 2012

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Thursday, 8 January 2015
Raquel Nieto, UNIVERSITY OF VIGO, Ourense, Spain; and L. Gimeno, A. Drumond, R. Trigo, D. Miralles, and S. Vicente-Serrano

The severe drought experienced in 2012 in central USA was particularly outstanding in extent (the most extensive since the 1950s) and in magnitude. This drought impinged widespread socio-economic impacts, particularly in Ecosystems and Agriculture, being classified as a major natural hazard by the U.S. Department of Agriculture. Its spatial extent and amplitude has not been experienced since the 1930s drought bowl years and resulted from the combined effect of the intense deficit of precipitation with the very high temperatures Most meteorological analyses of this drought has focused on anomalous boundary conditions such as those observed in oceanic sea surface temperature (SST). This approach is based on the accepted premise that strong SST changes in Tropical Atlantic/Pacific can result in anomalous atmospheric circulation, favouring periods with low atmospheric instability. However, to the best of our knowledge there are no work focused on the anomalous transport of moisture to this region, neither the subsequent anomalies of moisture transport from it. In this analysis we start by identifying the main drought area and defining the main drought considered for the 2012 central USA drought, allowing then to establish a comparison with the climatological sources of moisture for this region and the main sinks from it.. Afterwards, we used a Lagrangian approach to estimate the contribution of the anomalous transport of moisture to the affected area (both in position and intensity of the sources), as well as, the effect of the dryness of the region on its main moisture sinks. The identification of moisture sources and sinks as well as its changes in position was achieved with a well-known methodology which relies on the Lagrangian particle dispersion model FLEXPART, using about 2 million particles over a 34 year period (1980-2013), computed using ERA-interim reanalysis. Finally, changes in intensity of sources and sinks are stablished with two "state of the art" products of ocean and terrestrial evaporation, respectively OAFLUX and GLEAM