Fore-warning of early season agricultural drought condition over Indian region - a fractional wetness approach

Fore-warning plays an essential role for effective drought mitigation planning. A new approach, i.e. fractional wetness (f(w)), has been proposed towards fore-warning of early season agricultural drought over Indian region. The optimum soil moisture triggers the subsequent crop sowing activities that has been conceptualized in this approach. Shortwave Angle Slope Index (SASI) images derived from time-series (2001-2012) MODIS data was used for fractional-wetness (f(w)) computation. f(w) is the surrogate indicator for the percentage moisture available for a given time, based on its long-term range. The zone-wise f(w)thresholds was developed to estimate the area-favourable-for-crop-sowing (AFCS), which was validated with subsequent months' crop-planted-area derived from fractional vegetation cover (f(c)). The mean absolute error (MAE) was found to be similar to 5.73% of the agricultural area. The present methodology is capable of fore-warning the agricultural-drought one month prior to the traditional method. Moreover, the comparison of predicted AFCS with all India food-grains area corroborates the feasibility of proposed approach in quantifying the agricultural-drought, in terms of its intensity, extent and progression.