Evaluating the role of South Asian High on the transition phase of the Indian summer monsoon

• Published in: Theoretical and applied climatology 2022-02, Vol.147 (3-4), p.1511-1523
• Main Authors: Agrawal, Nishtha, Pandey, Vivek Kumar
• Format: Article
• Language: English
• Subjects: Agrarian society; Analysis; Annual variations; Aquatic Pollution; Atmospheric circulation; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Climate models; Climate science; Climatology; Earth and Environmental Science; Earth Sciences; Economic conditions; Economics; Horizontal cells; Horizontal orientation; Interannual variability; Monsoon forecasting; Monsoons; Original Paper; Regional climate models; Regional climates; South Asian High; Summer; Summer monsoon; Tropical climate; Vertical profiles; Waste Water Technology; Water Management; Water Pollution Control; Wind
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-021-03890-9

The transition phase of the Indian summer monsoon has always remained crucial for the agricultural, societal, and economic conditions of India. The present study addresses the role of South Asian High (SAH) and subtropical westerly jet (STJ) on the transition period (onset and withdrawal) of the Indian summer monsoon. For this purpose, we have utilized the outputs of Regional Climate Model (RegCM v4.6) and reanalysis ERA5 pressure level data for 24 years (1982–2005) of study. We begin our analysis with the evaluation of Tibetan Plateau (TP) heating, and its relationship with Sub-Tropical Jet (STJ). We further peruse its connection with different atmospheric factors during the seasonal transition of the monsoon. We have also tried to decipher the link between SAH and inter-annual variability of monsoon. Our analysis shows the efficiency of the model in simulating inter-annual variability of onset and withdrawal features during the monsoon period. The days of onset and withdrawal period simulated by the model have a similar mid-latitude connection when compared with the reanalysis data. The vertical structure of the Hadley cell and horizontal position of SAH have been produced realistically during the transition of the monsoon. We found that the change in meridional position of STJ has a significant impact on the arrival and departure dates of the monsoon. This repositioning of STJ in the meridional direction is strongly correlated to the upper-level high developed over the eastern periphery of the western pacific, which is an important component of  the monsoon flow over Bay of Bengal. Thus, the zonal position of SAH is observed to have direct implications on the onset and withdrawal dates of India. Its consideration in future studies can potentially enhance the predictability of the monsoon.