1. Investigation of Rainfall Trend in Jorhat Town, Assam Mayurakshi Bhuyan Baruah Department of Geography, North-Eastern Hill University Shillong-793022, Meghalaya, INDIA Email id: mayurakshibhuyanjrt@gmail.commayurakshibhuyanjrt@gmail.com +91 9482502746 (M)

2. Generalities Rainfall is the Prime Source Jorhat experiences South-west Tropical Monsoon Importance of rainfall Analysis

3. Study Area

4. Data Base and Methodology Secondary data of Rainfall (1958-2007) Tocklai Experimental Station, Jorhat Mean Moving Average Least Square Method Co-efficient of Variation

5. Results and Discussion Mean Annual Rainfall Decadal Rainfall Variability Seasonal Variability of Rainfall

6. Mean Annual Rainfall 198.76 cm per annum 126.34 cm in summer monsoon 15.95 cm in winter season

7. Mean Monthly Rainfall 1.91 cm (January) 25.50 cm (May) 73.15 cm in August, 1963 (Highest) -37 per cent of the total rainfall

8. Annual Rainfall 270.77 cm (1977)-Highest 139.44 cm (2001)-Lowest 82 per cent of total annual rainfall-May to October 18 per cent of total annual rainfall-December to April

9. Trend of Annual Rainfall Fig. 1: Trend of Annual Rainfall (cm) in Jorhat Town

10. Trend of Annual Rainfall Fig. 2: Trend of Annual Rainfall in Jorhat Town (1958-2007)

11. Decadal Rainfall Variability DecadesTotalAverage Standard Deviation Coefficient of Variation 1958-19672007.01167.25148.4888.78 1968-19772146.98178.92145.7781.47 1978-19871913.00159.42135.8685.22 1988-19972021.76168.48133.2779.10 1998-20071849.06154.09122.0579.21 Table 1: Decadal Rainfall Variability (cm) in Jorhat Town (1958 -2007) (Source: Rainfall in Jorhat 1958-2007) Fig. 3: Decadal Rainfall Variability (cm) in Jorhat Town

12. Seasonal Variability of Rainfall Seasons MonthsTotalAverage Maxi- mumMini-mum Standard Deviation Coefficient of Variation WinterJan 95.691.915.6301.4977.65 Feb 198.053.9613.0602.8171.03 Pre- monsoon Mar 320.746.4120.740.184.4669.49 Apr 957.5819.1544.321.939.3848.99 May 1275.2125.5062.568.9211.1543.73 MonsoonJun 1506.6930.1349.738.539.0530.02 Jul 1911.0838.2264.3117.7510.0726.35 Aug 1670.0533.4073.1518.0610.2630.72 Sep 122924.5841.3811.258.0832.86 Post- monsoon Oct 590.6311.8126.632.836.8958.32 Nov 116.852.348.202.0688.36 Dec 66.241.326.3801.51114.15 Total 9937.81198.7562416.0969.4577.21691.67 Table 2: Seasonal Variability of Rainfall (cm)in Jorhat Town (1958-2007) (Source: Rainfall in Jorhat 1958-2007) Fig. 4: Seasonal Variability of Rainfall (cm) (1958-2007)in Jorhat Town

13. Conclusion Decreasing trend of rainfall Post-monsoon Season has suffered Highest decadal rainfall variability (1958-67)

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