Role of equatorial central Pacific sea surface temperature in modulating rainfall over north India during Indian summer monsoon

The summer monsoon season contributes about 80% of annual rainfall in the highly populated region of north India. The teleconnections moderating the variation of summer monsoon rainfall in this region are not satisfactorily understood. A pathway of the equatorial central Pacific sea surface temperature (PSST) influences the north India summer rainfall is revealed from the high-resolution, more reliable, and state-of-the-art 41-year (1979-2019) observational data analysis and numerical experiment. The rise in PSST intensifies convection over the equatorial central Pacific with compensatory subsidence over the western equatorial Pacific. Consequently, a much broader and intense anomalous convergence is developed at the upper-troposphere, which subsequently intensifies the Asian subtropical westerly jet-stream. The Asian jet intensification strengthens the tropospheric wind shear at north India, as the low-level monsoonal winds are easterlies over there. The strong wind shear restricts the convective activities in north India. These results are also confirmed using the CFSv2 model sensitivity experiment and a case study of the year 2010.

Automated summary

The study reveals the pathway of equatorial central Pacific sea surface temperature affecting summer rainfall in north India. This influence strengthens the Asian subtropical westerly jet-stream, leading to restricted convective activities in north India due to strong wind shear.