Abstract
A dominant mode of interannual variability of Indian summer monsoon rainfall shows west-east dipole pattern with above normal rainfall towards west and central India and subdued rainfall towards the east and northeast India, and is related to the vigorous Azores High. The vigorous Azores High is accompanied by enhanced subsidence resulting in well-built widespread upper-troposphere convergence. This forms the meridional vorticity dipole consisting of anomalous cyclonic and anti-cyclonic circulation at 30°N and 50°N, respectively, and boosts the Rossby wave source. The cascading down Rossby wave train imposes successive negative, positive and negative Geopotential height (GPH) anomalies over north Mediterranean, northwest and northeast of India, respectively. The negative GPH anomaly at the north Mediterranean increases the Asian jet towards the Caspian Sea, strengthening the monsoon circulation through the ‘silk-road’ pattern. While, the dipole GPH anomaly north of India shift the Tibetan High westwards, triggering monsoon activity towards the west.
Highlights
The Indian summer monsoon (ISM), which is part of the South Asian monsoon system, is one of the largest global phenomena of the general circulation that has its impacts on the global weather and climate, and the life of millions of Indians
Association between Azores High and ISM; ISM Teleconnections To investigate the dominant patterns of ISM variability, Empirical Orthogonal Function (EOF) analysis of the linearly detrended Junenpj Climate and Atmospheric Science (2021) 26
July-August-September (JJAS) seasonal gridded rainfall over India, The principal component (PC) of EOF1 (PC1) ISM rainfall, is used as excluding north-east India, for the period 1979–2019 have been a basic function for elucidating its teleconnections
Summary
The Indian summer monsoon (ISM), which is part of the South Asian monsoon system, is one of the largest global phenomena of the general circulation that has its impacts on the global weather and climate, and the life of millions of Indians. It spans a short period from June through September (JJAS) and contributes about 80% of the annual rainfall in the country. The JJAS seasonal rainfall plays an important role in the water management and the economic planning of the country It has significant temporal and spatial variations[1]. It becomes very important to study this variation and its teleconnections
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