Abstract
In this study, trends as well as dominant and significant periodicity of metro-logical drought variables were analyzed for all regions of India and five homogenous monsoon regions of India. Monsoon, nonmonsoon and annual standardized precipitation index (SPI) along with annual drought duration (ADD), annual drought severity (ADS), and annual drought peak (ADP) time series were analyzed. Discrete wavelet transform-based Mann-Kendall test was used to identify trends and dominant periodic components affecting trend, whereas global wavelet spectrum obtained from continuous wavelet transform was used to identify significant periodicities in drought variables. A significant decreasing trend in monsoon SPI was observed in central and north east India, whereas significant decreasing trend was also observed in annual SPI in north eastern India. No significant trends were observed in northwest monsoon drought, ADD, ADS, and ADP time series. Both high-(2–8 year periodicity) and low-frequency (16–64 year) components were observed to influence the trend in drought variables. However, for most of the regions, these dominant periodic components were not significant.
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