Comprehensive analysis of trends in mean temperature over the Cauvery River Basin, India using various statistical methods and discrete wavelet transform

ABSTRACT

Climate change (CC) and global warming are widely acknowledged as the most important environmental problems faced by the world now. The rise in global and local mean temperature (Tmean), along with increased human interventions, has significantly impacted the hydrology of the Cauvery River Basin (CRB). Thus, this study carried out a comprehensive trend analysis for the Tmean data over the CRB from 1970 to 2022. Four aspects of the trend, viz. magnitude, significance, nature, start, and end are assessed using various statistical tests. Also, the regional significance of the trends is evaluated utilizing the false discovery rate (FDR) test. Discrete wavelet transform (DWT) is used in combination with the Mann–Kendall (MK) test/MK test with Block Boot Strapping (MKBBS test) and Sequential Mann–Kendall (SQMK) test to determine the time scale that dominated the trends in Tmean data over the basin. The results showed that consistent warming trends are observed in Tmean for all temporal scales throughout the basin with positive Sen's slope (SS) values. From the decomposition, it is observed that the trends are driven by periodic patterns lasting under 10 years, or, generally, 2 and 4 years for annual and seasonal scales and 4 and 8 months for the monthly time scale.