Rainfall variability analysis of Uttar Pradesh for crop planning and management

Time series analysis and statistical significance of trends in rainfall data was carried out using standard Mann-Kendall test statistics. The non-parametric Mann-Kendall (M-K) statistical rank test, which is widely used in climate research, was employed in this study to find out fluctuations and presence of trend in time series data of rainfall at a single station, as well as regional averages. Analysis of rainfall data (1981-2012) of Uttar Pradesh reveals significant decreasing trend in total quantum of annual rainfall. It was also noticed that the frequency of occurrence of annual rainfall below normal was less before 1990s while increased after 1990s. The amount of annual rainfall decreased significantly after 1996 from 1040.5 mm to 988 mm, i.e., a decrease of 5 percent. A very interesting trend has been noticed for the quantum of monthly rainfall, i.e., it was found significantly decreased after 1996 for the months of winter season (October-February) while at par for the months of summer season except May only which was found increased as compared to before 1996. The quantum of monthly rainfall was found significantly decreased after 1996 for initial and last months of monsoon season, i.e., June and September while increased for the middle months, i.e., July and August as compared to before 1996. The study of decadal variability in annual rainfall showed that an alternate decreasing and increasing trend in all the three decades viz., 1981-1990, 1991-2000 and 2001-2010.