Assessment of droughts in Romania using the Standardized Precipitation Index

This paper analyses the temporal and spatial variability of droughts in Romania, over the last five decades, based on a high-resolution data set developed at country level, namely ROCADA. Droughts are analyzed by means of the Standardized Precipitation Index (SPI) for 3-, 6- and 12-month time scales. The time period 1979-1995 was identified as the period with the highest number of months affected by moderate, severe as well as extreme drought conditions. The 2000-2001 episode was identified as the major drought event, concerning the severity and the spatial extent, with an area of 60 % of the country affected by extreme drought for more than 10 consecutive months. The results of the trend analysis emphasize an inhomogeneous spatial aspect of the dryness/wetness trends. Statistically significant positive trends (wetter conditions) over small areas distributed inhomogeneous around the country like the southernmost corner as well as the northeastern part and some small areas in the western part of the country have been identified. Statistically significant negative (drier conditions) trends have been obtained over the southwestern part of the country and over the eastern part. In general, the SPI trends follow the observed trends in the monthly precipitation totals, at country level. The results indicate that there is no spatial consistency in the occurrence of droughts at country level and the SPI at different time scales may vary in its usefulness in drought monitoring, due to the fact that in the case of shorter time scales the SPI values have the tendency to fluctuate frequently above and below the zero line, while for longer time scales there are well-defined dry and wet cycles.