Comparison of Standardized Precipitation and Selyaninov hydrothermal drought indices

A lot of recent works have been done for development of drought indices as well as to review theirs application and comparison of their advantages and drawbacks. The Standardized Precipitation Index was proposed to characterize meteorological droughts from 2009 by World Meteorological Organization. Selyaninov’s hydrothermal coefficient is used to evaluate the agro-climatological conditions in some European countries and it is confirmed to be a drought index in Lithuania. The purpose of investigation was to compare the Standardized Precipitation Index (SPI) as the reference drought index accepted by the World Meteorological Organization and the Selyaninov’s hydrothermal coefficient (HTC) as the main drought index used in Lithuania. Assessment of vegetation period during 2003-2012 (May – September) according HTC indicated 70 % as wet periods (2004 - 2007, 2010- 2012) and 30 % as enough humid (2003, 2008, 2009), there were no dry periods indicated. Assessment according SPI indicated 90 % near normal of all periods (2003-2009 and 2011-2012), moderately wet was period of 2010. Evaluation of one month time scale periods according HTC and SPI1 differed in 39 of the 50 cases (78 %). Excessively wet and optimally wet according HTC were 52 % and 24 % accordingly. According SPI1 very wet and moderately wet were identified 8 and 16 % of total months accordingly. There was no month evaluated as extremely wet. According HTC as weak dry were identified 52 % of all months, according SPI1 72 proc. were identified as near normal. It was found out the very strong correlation (r=0,855) between HTC and SPI1, thought the rating of values according HTC and SPI1 differed. HTC < 0.7 equals to SPI1 < -1.4 and HTC < 0.5 equals to 1.8. The biggest differences determined during humid and wet periodsVytauto Didžiojo universitetasŽemės ūkio akademij