Assessment of Theissen Polygon Method to Analyse Monsoon Rain in Erstwhile Jalpaiguri District, West Bengal, India Moitrayee Das* Department of Geography, Chandernagore College, Hooghly, West Bengal, India *Corresponding author: Moitrayee Das, Department of Geography, Chandernagore College, Hooghly, West Bengal, India, Tel: +88053161355; E-mail: moitre_alap@rediffmail.com Received Date: October 12, 2018; Accepted Date: November 16, 2018; Published Date: November 23, 2018 Copyright: © 2018 Das M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract The rainy season stretches from July to the end of September in Indian sub-continent. During this period, the South-West Monsoons pick up moisture from the Bay of Bengal and blow over the state of West Bengal. Most of the annual average rainfall of 175 cm about 125 cm occurs during this period. Heavy rainfall of above 250 cm is observed in the Darjeeling, erstwhile Jalpaiguri (from 2014 the district has been divided into two administrative unit viz Jalpaiguri and Alipurduar) and Cooch Behar district. Among these districts, Jalpaiguri district is the only district of West Bengal, situated in the foothill region of eastern Himalaya. The total areal extent of this district is 6227 km 2 . Taking consideration about the areal extent IMD (Indian Meteorological Development) has been established total eight metrological station within this district. Theissen Polygon has been applied to manage these eight station to find out the exact rainfall pattern in this spatial extend. Present paper is to represent the variation of monsoon rainfall in respect of depth, volume and probability in same physiographic condition within large areal extend. Keywords: Monsoon rainfall; Depth; Volume; Probability Introduction Te climate of the district is Cwg as per Koppen’s analysis of Indian climate. Cwg refers to monsoon type climate with dry winter. It is mesothermal climate with average temperature the cold months being less than 18°C (10.8°C) in Jalpaiguri. Te maximum temperature is recorded in July-August when it is 30.9°C. It is situated on an extensive piedmont plain lying on the windward side of southern Himalayan forelands. Rainfall is high particularly from June to the middle of October due to south-west monsoons. Te winter receives scattered rains from north-east monsoons having no infuence on any food hazard event. Te atmosphere is highly humid throughout the year. Highest average rainfall is 3110 mm and it is associated with the occurrence of foods. In order to evaluate the spatial and temporal rainfall quantity, Tiessen Polygon is one of the widely used techniques and important method. Its calculation method is fast, simple and somewhat accurate. With this method, the calculation of rainfall is simple, in a way that only the station’s rainfall amount and the calculated station weight, the area of the infuence of each station (also called Teissen Constant or Area Factor) are required. Tiessen Polygon method is a standard method for computing mean areal precipitation (MAP) for the area having more or less homogeneous topographic as well as meteorological features [1]. As the district has large areal extent and having more or less homogeneous topography with variation in monsoon rainfall, Tiessen Polygon is a most appropriate technique to follow the spatial and temporal variation of monsoon rainfall within the district. Study Area Te study area comprises erstwhile Jalpaiguri districts of West Bengal which is situated in the foothill of eastern Himalaya in West Bengal. Te district is geographically situated from 26°16'35'' North to 26°59'30'' North and from 88°04’59’’East to 89°55'20'' East and comprising an area of 6227 km 2 [Jalpaiguri’-District Gazetteer]. Figure 1: Location map. In West Bengal, Jalpaiguri district occupies the southern fanks of the foothills of the Himalaya. Jalpaiguri district is bounded on the north by Darjeeling district of West Bengal and Bhutan, on the south by Uttar Dinajpur and Coochbehar districts of West Bengal, on the west by Uttar Dinajpur and Darjeeling districts of West Bengal and Purnea district of Bihar, while Assam occurs on the east. Te R. J o u r n a l o f C l i m a t o l o g y & W e a t h e r F o r e c a s t i n g ISSN: 2332-2594 Journal of Climatology & Weather Forecasting Das, Climatol Weather Forecasting 2018, 6:4 DOI: 10.4172/2332-2594.1000241 Research Article Open Access Climatol Weather Forecasting, an open access journal ISSN:2332-2594 Volume 6 • Issue 4 • 1000241