Relative Contribution of Precipitation and Air Temperature on Dry Season Drying in India, 1951-2018

Soil moisture plays an essential role in food production and land-atmosphere feedback. However, the relative contribution of precipitation and air temperature on dry season (October-December) soil moisture has not been systematically examined in India. Using observations and simulations from the Variable Infiltration Capacity model, a significant (4%, p value = 0.04) decline in soil moisture (dry season drying hereafter) was found in a large part of India during the 1951-2018. The decline in the summer monsoon precipitation in India during 1951-2018 is mainly due to a decrease in rainfall during the late monsoon season (August-September). A substantial decline (-18.6%, p value = 0.009) in the late monsoon and (-26%, p value = 0.19) dry season precipitation was observed. A significant warming (0.75 degrees C, p value = 0.002) has occurred during the dry season between 1951 and 2018. The relative contribution of decline in precipitation in the late monsoon (30%) and dry season (34%) is considerably higher than the dry season warming (15%). The previously unexplored role of climate warming on the dry season drying was analyzed using Maximum Covariance Analysis between precipitation and sea surface temperature, which suggests both large-scale and localized influences. Climate warming over the Indian and Atlantic Oceans is associated with declining precipitation during the late monsoon and dry seasons over central India. Also, climate warming over land exacerbates the dry season drying by depleting soil moisture. The dry season drying over a large part of India contributed by climate warming has substantial implications for irrigation water management and groundwater abstraction.