Spatial and temporal trends in high resolution gridded rainfall data over India
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Indian Academy of Sciences (0123456789().,-volV)(0123456789( ).,-volV)
Spatial and temporal trends in high resolution gridded rainfall data over India GRACE NENGZOUZAM1, SANAYANBI HODAM2, ARNAB BANDYOPADHYAY1,* and ADITI BHADRA1 1
Department of Agricultural Engineering, North Eastern Regional Institute of Science and Technology, Nirjuli (Itanagar) 791 109, Arunachal Pradesh, India. 2 RMO Division, National Institute of Hydrology, Roorkee 247 667, Uttarakhand, India. *Corresponding author. e-mail: [email protected] MS received 27 September 2019; revised 11 June 2020; accepted 8 August 2020
A high resolution (0.2590.25) daily gridded dataset was analysed to study the spatial and temporal trend in various regions of India during the period of 1901–2013. The non-parametric Mann–Kendall (MK) test has been applied to the time series (1901–2013) rainfall data in order to detect the trends for both rainfall depth and number of rainy days. Sen slope estimator test was also used to Bnd out the magnitude of the trend. In addition, Pettitt–Mann–Whitney (PMW) test was employed so as to determine the probable change year. The results of trend analysis of rainfall depth showed maximum number of grid points having increasing trend in summer months, while the dry months showed higher grid points with significant decreasing trend. Jammu and Kashmir, in particular, was found to have increasing trend in all months for all three levels of significances, i.e., 1%, 5%, and 10%, while NE (northeastern) region continuously reported significant decreasing trends. The annual trend analysis of the 30-year moving window of rainfall depth showed higher number of grid points with significant increasing trend during 1901–1950, decreasing trend during 1931–1980, and increasing trend again during 1961–2013. The PMW test for the rainfall depth and number of rainy days for 1901–2010 showed 1961 and 1974 as the most probable change point years with about 339 and 284 grid points agreeing upon it, respectively. The maximum increasing significant trends in rainfall was observed during south-west monsoon months. Recent years also reported an increase in rainfall intensity leading to probable increase of extreme events like Coods and droughts. Keywords. Gridded rainfall; temporal and spatial trends; change point analysis; Mann–Kendall test; Pettitt–Mann–Whitney test.
1. Introduction For an agriculture dependent country like India, rainfall is the most important parameter aAecting the national economy through agricultural
production as most parts of the country entirely depends upon monsoon rain for the production of food grains. Rainfall is also responsible for other hazardous natural events like extreme rainfall (both drought and Cood) which directly or
Supplementary materials pertaining to this article are available on the Journal of Earth Science Website (http://www.ias.ac.in/ Journals/Journal˙of˙Earth˙System˙Science).
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indirectly aAect the country’s economy as dry years have negative eAect on grain production, food s
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