International Journal of Water Resources and Arid Environments 2(4): 108-114, 2012 ISSN 2079-7079 © PSIPW, 2012 Corresponding Authorr: S.K. Dubey, Water Resource Development and Management, Indian Institute of Technology, Roorkee, 247667, India. Tel: +919452488914, E-mail: sunil2949@gmail.com. 108 Assessing the Relation Between NDVI and Rainfall over India S.K. Dubey, G. Pranuthi and S.K. Tripathi Water Resource Development and Management, Indian Institute of Technology, Roorkee, 247667, India Abstract: The Indian subcontinent has diverse vegetation with the climate varying from monsoonal in south to temperate in the North. The biological productivity of the vegetation cover therefore largely controlled by water and temperature stresses. The Normalized Deferential Vegetation Index (NDVI) was shown to be sensitive to changes in vegetation conditions. Since it is directly influenced by the chlorophylls absorption of the suns radiation. In this study rainfall data (from IMD) and MODIS- NDVI data (GLAM project) for 28 states of India was used. NDVI data from MODIS (with a resolution of 250 km) images was correlated with state wise annual precipitation for the year 2004-2008. The correlation value for NDVI and rainfall was observed to be 0.64 and R value was 0.40. From this study we can conclude that the NDVI is majorly dependent on the rainfall. Other 2 factors like temperature, humidity, radiation etc., also influence the vegetation growth and productivity but in lesser proportion compared to precipitation. Key words: NDVI Precipitation Correlation analysis MODIS images INTRODUCTION is almost similar and they contribute 13.8 % and 14.2 % of According to the Koppen system of climatic monsoon rainfall (877.2 mm) contributes 74.2 % of classification, the climate of India is resolved into six annual rainfall (1182.8 mm). Contribution of pre-monsoon major climatic subtypes; their influences give rise to rainfall and post-monsoon rainfall in annual rainfall is desert in the west, alpine tundra and glaciers in the mostly the same (11%). Coefficient of variation is higher north, humid tropical regions supporting rain forests in during the months of November, December, January and the southwest and Indian Ocean island territories that February. flank the Indian subcontinent. Regions have starkly Normalised Difference Vegetation Index (NDVI) is an different-yet tightly clustered-microclimates. The nation index which measures this difference, providing a measure is largely subject to four seasons: winter (January and of vegetation density and condition. It is influenced by February), summer (March to May), a monsoon (rainy) the fractional cover of the ground by vegetation, the season (June to September) and a post-monsoon period vegetation density and the vegetation greenness. It (October to December). indicates the photosynthetic capacity of the land surface Indian monsoon rainfall is without any trend and cover NDVI is also directly related to the: mainly random in nature over a long period of time, particularly on the all India time scale (Mooley and “leaf area index” (LAI), which is often used in crop Parthasarathy, 1984). To understand the trend and growth models distribution of rainfall over India a brief study was done herbaceous or total green biomass (tons/ha) for by (Guhathakurta and Rajeevan 2006) using rainfall data given vegetation types, of all over India (36 Meteorological sub division) from photosynthetic activity of the vegetation 1901-2003 and they find that June and September rainfall percent ground cover. annual rainfall respectively. The mean south-west