Trend Detection Analysis of Seasonal Rainfall of Homogeneous Regions and All India, Prepared by Using Individual Month Rainfall Values

Abstract

For agriculture-based country like India, seasonal rainfall is very crucial. Trends and variability in rainfall are one of the crucial aspects in studies of climate change. Earlier studies performed on the trend detection analysis of seasonal rainfall of homogeneous regions and all India (ALLIN) are having three drawbacks: (1) they have not considered individual month rainfall values of given season in the analysis, (2) they have not used smoothing curve and innovative trend analysis plot for supporting the results of trend detection analysis, and (3) they have not studied the effect of different time periods on the results of trend detection analysis. Thus aforesaid three research gaps are addressed in the present study by performing trend detection analysis of seasonal rainfall of ALLIN and seven homogeneous regions by the following: (1) considering individual month rainfall values of given season in the analysis, (2) use of smoothing curve and innovative trend analysis plot for supporting the results of trend detection analysis, and (3) performing trend detection analysis for three time periods 1901–2003, 1948–2003, and 1970–2003 to study the effect of different time periods on the results of trend detection analysis. Mann-Kendall (MK) test and MK with block bootstrapping approach (MKBBS) test are used for assessment of statistical significance of trend present in independent and dependent time series, respectively. Correlogram is used for assessment of independence of data. Magnitude of trend is assessed by using SS test. Study detected presence of statistically significant trends in pre-monsoon rainfall time series of North West India (NWIND) region and monsoon rainfall time series of ALLIN and West Central India (WCIND) region for the time period 1948–2003.