Variability of agro climatic regime over homogeneous monsoon regions of India — El Niño and La Niña events

The global short term climate signal from the Equatorial Pacific sea surface temperature pattern in conjunction with the Southern oscillation of sea level pressure plays a crucial role in governing the global weather systems by modulating and altering the yearly climate scenario across the globe. The analysis of Normalized Difference in Vegetation Index (NDVI) fields of the five homogeneous regions of India with the index of moisture adequacy and Multivariate ENSO Index yielded the phenological metrics such as senescence in terms of greenness up and down along with the lag between maximum NDVI and index of moisture adequacy for normal (1982–2000), El Niño (1997) and La Niña (1998) years respectively. A threshold value of 60% soil moisture adequacy is considered for sustainable crop or vegetation growth in obtaining the phenological metrics for the regions under consideration. The north east, peninsular India along with west central India experienced an increase in the number of humid days both in the El Niño and La Niña years compared to normal. The annual figures of All India rice yields are increasing linearly and the trend was significant but no trend is noticed in moisture adequacy. An agro climatic model is developed for the estimation of All India rice yield and is of help in designing the agro meteorological advisories.

► The NE, Peninsular and WC India experienced increased number of humid days both in the El Nino and La Nina years compared to normal.
► The NW India recorded maximum NDVI by September and was advanced by one month compared to other regions.
► Small variations in IMA are accompanied by large variations in All India rice yield.
► The annual All India rice yields are increasing linearly with significant trend.
► The suggested agro climatic model imbibed the four variables that have significant impact on rice yield.