Understanding Recycled Precipitation at Different Spatio-Temporal Scales Over India: An Eulerian Water Tagging Approach

Land evapotranspiration has a notable impact on the continental precipitation of India during monsoons. Given the heterogeneous land use and climate, India hosts many transition zones, which are hotspots for land-atmosphere interactions. This work aims to study the soil moisture-precipitation feedbacks over India by quantifying recycled precipitation using the Eulerian water vapor-tagging technique incorporated in the Weather Research and Forecasting model. Eulerian vapor tagging techniques provide the most accurate information on recycled precipitation. We tracked the vapor originating at two spatial scales-entire India and six homogeneous monsoon regions. The latter analysis is conducted to assess inter-regional vapor exchanges. In this process, we determined the seasonal, monthly, and diurnal variations of recycling ratio and assessed its behavior during active and monsoon break periods. We considered three contrasting monsoon seasons (surplus, normal, and deficit rainfall years) for analysis. Results show a high recycling ratio in Central India, Gangetic plain, and Northeast India. Recycling ratio increases with monsoon progression and peaks in September (& SIM;0.30). The Himalaya and transient low-pressure systems originating from the Bay of Bengal are vital for precipitation recycling in India. The contrasting monsoons exhibit changes in recycling ratio only at monthly scale. Regional analysis indicates West Central India is the most significant vapor contributor, while Northeast India is the highest recipient of recycled precipitation. High recycling (& SIM;20%) shifts from central India during the active period to the foothills of Himalaya during the break period. Diurnal scale analysis reveals high afternoon recycling due to enhanced convective activity.

Automated summary

Land evapotranspiration significantly affects the continental precipitation of India during monsoons. This study utilizes the Eulerian water vapor-tagging technique to analyze the soil moisture-precipitation feedbacks and quantifies recycled precipitation. Results show a high recycling ratio in Central India, Gangetic plain, and Northeast India, increasing with monsoon progression and peaking in September. The Himalaya and transient low-pressure systems from the Bay of Bengal play vital roles in precipitation recycling in India.