Analysis of trends and dominant periodicities in drought variables in India: A wavelet transform based approach

• Published in: Atmospheric research 2016-12, Vol.182, p.200-220
• Main Authors: Joshi, Nitin, Gupta, Divya, Suryavanshi, Shakti, Adamowski, Jan, Madramootoo, Chandra A.
• Format: Article
• Language: English
• Subjects: Drought; Mann-Kendall test; Periodicity; SPI; Trend analysis; Wavelet transform
• ISSN: 0169-8095; 1873-2895
• DOI: 10.1016/j.atmosres.2016.07.030

In this study, seasonal trends as well as dominant and significant periods of variability of drought variables were analyzed for 30 rainfall subdivisions in India over 141years (1871–2012). Standardized precipitation index (SPI) was used as a meteorological drought indicator, and various drought variables (monsoon SPI, non-monsoon SPI, yearly SPI, annual drought duration, annual drought severity and annual drought peak) were analyzed. Discrete wavelet transform was used in conjunction with the Mann-Kendall test to analyze trends and dominant periodicities associated with the drought variables. Furthermore, continuous wavelet transform (CWT) based global wavelet spectrum was used to analyze significant periods of variability associated with the drought variables. From the trend analysis, we observed that over the second half of the 20th century, drought occurrences increased significantly in subdivisions of Northeast and Central India. In both short-term (2–8years) and decadal (16–32years) periodicities, the drought variables were found to influence the trend. However, CWT analysis indicated that the dominant periodic components were not significant for most of the geographical subdivisions. Although inter-annual and inter-decadal periodic components play an important role, they may not completely explain the variability associated with the drought variables across the country. •Trend and periodicity in monsoon, non monsoon and yearly SPI, drought severity, duration and peak over India is studied.•During the second half of 20th century, drought occurrences have increased over Northeast and Central India.•Inter-annual and inter-decadal periodic components play an important role in the observed trends in drought variables.•Inter-annual and inter-decadal periodic components may not completely explain the drought variability across the country.