Kharif foodgrain yield and daily summer monsoon precipitation over India

摘要

Foodgrain yield over India during kharif (summer) season is directly affected by day to day variations in summer monsoon precipitation (June through September). An increase (decrease) in foodgrain yield is generally associated with an increase (decrease) in rainfall. However, the reduction of rainfall or occurrence of heavy rainfall activity may cause adverse effect on the crop growth. This study is therefore aimed at understanding the impact of all possible values of daily precipitation from lowest to highest rainfall during summer monsoon on kharif foodgrain yield over India for the period 1966-2003. The study also includes an impact of intense rainfall events (1 and 5 days maximum precipitation) on foodgrain yield. Analysis covers frequency of rainy days based on all fixed thresholds (1 mm and above) at the interval of 1 mm as well as percentile thresholds (1st percentile to 99th percentile) at the interval of 1 percentile. The study reveals that the kharif foodgrain yield increases with increase in all-India summer monsoon precipitation and rainy days. Strong positive relationship (statistically significant at 1% level) is observed for lower range of threshold values from 1 to 50 mm (1st percentile to 90th percentile), and the magnitudes of correlation decreases with increase in threshold values. The negative impact of the heavy rainfall activity is more pronounced over the heavy rainfall regions of northeast India. It is found that the prolonged occurrence of intense rainfall activity increases their impact on the foodgrain yield. Normal (moderate) range of precipitation indices is seen to be associated with both positive and negative anomalies of foodgrain yield, which point towards the influence of other climatic factors in determining the better yield of kharif foodgrain.