Riscuri şi Catastrofe (Apr 2013)
ANALYSIS OF DROUGHT PHENOMENON WITHIN OLTENIA PLAIN, ROMANIA (1961-2010)
Abstract
Analysis of drought phenomenon within Oltenia Plain, Romania (1961-2010). Oltenia Plain, located in the south-western part of the Romanian Plain, is characterized by a moderate pluviometric regime (compared to the pluviometric patterns of plain areas from Romania) and, thus, each negative deviation generates certain complex phenomena, such as drought, that trigger perturbations of the natural environment and economic activities. Thus, determining the annual, seasonal and monthly negative deviations of precipitation at local scale is extremely important in order to establish accurate trends of drought phenomenon. We used 50-year time series (1961-2010) for six meteorological stations. The Standardized Precipitation Anomaly (SPA) and Weighted Anomaly of Standardized Precipitation (WASP) indicate a high predominance of normal years (>70%), both at annual and monthly levels. However, there clearly resulted a deterioration of the rainfall regime in the past three decades – normal years, but negative deviations in 80% of the cases; the driest years in the last five decades (1992, 1993, 2000, 2008); the wettest years (1999 and 2005). Linear regression emphasizes an obvious negative trend of the SPA values for the western and eastern parts of the plain (D.T. Severin, Caracal) and a positive trend for the northern extremity (Craiova); the rest of the region displays a slightly negative trend. At monthly level, the most exposed season is summer, even if drought affected the region in all the months of the year. For the last decade, the impact of drought was also assessed based on satellite images SPOT- VEGETATION and TERRA/MODIS. We used the products NDVI (Normalized Difference Vegetation Index), 10-day synthesis and 1 km spatial resolution and LAI (Leaf Area Index) 8-day synthesis, 1 km spatial resolution, data supplied by French Spatial Agency and NASA. The analysis of these products allowed us to emphasize a spatial and temporal differentiation of the density of vegetation within Oltenia, mainly induced by rainfall deficit and variability.
