Comparative analysis of hydrothermal conditions of Tomsk region by using different drought coefficients

Abstract

Abstract The global and regional climatic changes that have been most intense in recent decades are characterized by an increase in the frequency of extreme natural events which include droughts and periods of extensive moistening. Air temperature and precipitation are the main characteristics of climate indicating the changes in the droughts/extensive moistening. According to observations of weather stations of Tomsk region, air temperature has been changing very much since the 70s of the 20th century (during 1967-1997 from -0.6 to + 0.56°C and during 1970-2009 from 0.4 to 0.6°C/10 years). Since the mid-1980s, an increase in precipitation has been observed. For a detailed analysis of drought indices (HTC, S, SPI, and SPEI) in the present paper, we use observation data from the Tomsk region weather stations from May to September, 1966-2017. When calculating the indices, warming of the atmosphere, expressed through air temperature, as well as atmospheric humidification, characterized by precipitation, must be taken into account. Also, for a correct comparison of the hydrothermal conditions of different landscapes it is necessary to use normalized indicators. A comparative analysis of the different hydrothermal indices has shown that the S and SPEI indices most closely correspond to these requirements. They also most synchronously indicate droughts.