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Abstract
Rainfall is the major climatic factor that affects the growth and distribution of natural vegetation at a regional scale. The high space–time variability of rainfall in the Tunga and Bhadra river basins caused by the high-elevation Western Ghats mountains forces changes in the seasonal distribution of local vegetation. Understanding the relationship between vegetation greenness and rainfall is a key feature in managing the vegetation of the river basin. For this, we have analysed a 7-year (2005–2011) time series of the Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index (NDVI) and Tropical Rainfall Measuring Mission 3B42 rainfall data. The results show that rainfall exerts seasonal control on vegetation greenness. A significant negative correlation was observed for the monsoon season and a favourable positive association for the rest of the seasons. We found a maximum amount of vegetation greenness in the post-monsoon season (October–December). The availability of enough soil moisture from the southwest monsoon season along with suitable climatic conditions triggers an increased greenness amount during the post-monsoon months. We also investigated seasonal and monthly correlations of monsoon rainfall with the NDVI of its subsequent months. The results suggest that monsoon rainfall is a key factor that sustains the long-term greenness in the river basins.
Acknowledgements
The authors would like to acknowledge the Central University of Karnataka for providing a laboratory facility for the analysis. The TRMM data used in this study were acquired using the GES-DISC Interactive Online Visualization and Analysis Infrastructure (Giovanni) as part of the NASA’s Goddard Earth Sciences (GES) Data and Information Services Centre (DISC).