Rainfall over the Himalayan foot-hill region: Present and future
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Indian Academy of Sciences (0123456789().,-volV)(0123456789( ).,-volV)
Rainfall over the Himalayan foot-hill region: Present and future ARKADEB BANERJEE1, A P DIMRI1,*
and KIREET KUMAR2
1 School 2
of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India. G.B. Pant National Institute of Himalayan Environment and Sustainable Development, Kosi-Katarmal, Almora, Uttarakhand, India. *Corresponding author. e-mail: [email protected] MS received 1 March 2019; revised 7 August 2019; accepted 7 September 2019
Uttarakhand, one of the Himalayan foot-hill states of India, covers an area of 51,125 km2. This region is enriched with bio-diversity and is one of the highly potential regions in the Central Himalayas for agroclimate, hydro power generation, food-processing, tourism, etc. Present study investigates the spatiotemporal rainfall distribution over the state during Indian summer monsoon period. Observational and modelled (under different Representative Concentration Pathways (RCPs) at radiative forcing 2.6, 4.5 and 8.5 W/m2) rainfall distribution is studied to assess the present and future trends. Study uses standard observational rainfall estimates from APHRODITE, Tropical Rainfall Measuring Mission (TRMM 3B42) and India Meteorological Department (IMD) gridded rainfall datasets and inter-compare these products in order to Bnd out orographic responses during the monsoon months and elevation dependent mean rainfall pattern changes. It is found that rainfall pattern breaks near 3100 m elevation. Comparative analysis reCects that with respect to IMD, TRMM 3B42 rainfall underestimates more than 3 mm/day rainfall whereas, APHRODITE overestimates rainfall below 4.5 mm/day. Future trends in modelled monsoon rainfall are examined and mixed results are found and discussed with possible explanation. Keywords. Uttarakhand; rainfall; topography; trends.
1. Introduction Understanding the rainfall processes and its spatiotemporal variability over the Indian sub-continent is very crucial for a wide range of applications viz., agriculture, water resource management, hydrological purpose etc. India gets about 80% of total annual rainfall during June–September (JJAS) summer monsoon season (Ghosh et al. 2009). The seasonal migration of the inter-tropical convergence zone (ITCZ), which is a manifestation of a wind reversal process in the monsoon region, plays an important role in the generation and development of the Indian Summer Monsoon (ISM)
(Gadgil 2003). The strength of the summer monsoon rainfall decreases when it reaches the northern part of India specifically, the Western and Central Himalayas from east to west along its trajectory (Basistha et al. 2007). The study region (Bgure 1) Uttarakhand is located at the foot-hills of the Central Himalayas encompassing geographic location from 28N– 31.5N and 77.5E–81.4E. The total geographical area of the state is 51,125 km2 and out of which 93% is mountainous, 65% is covered by forest and glaciers are found at the higher elevations. Geographically, the state can b
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