Atlantic Niño modulation of the Indian summer monsoon through Asian jet

Abstract

The Indian rainfall and the Atlantic Niño peaks during summer month and have inverse relationship. This relationship has been revisited in the current study and it is found that the Atlantic Niño significantly influences a dipole pattern of rainfall in the north-east and the north-western parts of India. The positive phase of the Atlantic Niño intensifies the inter-tropical convergence zone, as a result of this local tropospheric warming, over the equatorial east Atlantic and west Africa, owing to the enlargement of the upper-troposphere divergence. This provokes meridional stationary wave owing to the stronger meridional transfer of energy, as the influences of background jet-streams are minimal over North Africa and Europe. This results in the consecutive anomalous negative, positive, and negative geopotential heights (GPHs) over the tropical east Atlantic, Mediterranean, and north-west Europe, respectively. The north-west Europe acts as the center of action for the propagation of a Rossby wave train zonally oriented toward central Asia reinforcing positive GPH anomaly over there. The positive GPH anomaly reduces the Asian subtropical westerly jetstream east of the Caspian Sea, owing to the reduction in the upper-troposphere divergence toward the Indian subcontinent and caused for above (below) normal north-east (north-west) Indian summer monsoon rainfall. The atmospheric general circulation model captures general characteristics of wave pattern and changes in the Asian jet when correlated with Atlantic Niño with considerable skill.

Long-Lead Statistical Forecasts of the Indian Summer Monsoon Rainfall Based on Causal Precursors

“…In this case, the physical linkage is less clear , nevertheless IMD identifies some predictability for the ISMR from SST in the tropical North Atlantic and SLP over the Azores High region (likely linked to the NAO) (Rajeevan et al 2007. Previous evidence suggests that the ISMR and the Atlantic Niño share an inverse relationship during summer months (Wang et al 2009;Yadav et al 2018). The Atlantic Niño significantly influences a dipole pattern of rainfall in the northern parts of India and the positive phase of the Atlantic Niño results in a local tropospheric warming, which intensifies the intertropical convergence zone over the equatorial east Atlantic and west Africa and excites an anticyclonic anomaly over India (Wang et al 2009;Kucharski and Joshi 2017;Yadav et al 2018).…”

“…Previous evidence suggests that the ISMR and the Atlantic Niño share an inverse relationship during summer months (Wang et al 2009;Yadav et al 2018). The Atlantic Niño significantly influences a dipole pattern of rainfall in the northern parts of India and the positive phase of the Atlantic Niño results in a local tropospheric warming, which intensifies the intertropical convergence zone over the equatorial east Atlantic and west Africa and excites an anticyclonic anomaly over India (Wang et al 2009;Kucharski and Joshi 2017;Yadav et al 2018). During March and April, a positive correlation is found between Atlantic tropical SST and the ISMR, as shown in our study (Varikoden and Babu 2015).…”

Predicting peak summer monsoon precipitation over Pakistan in ECMWF SEAS5 and North American Multimodel Ensemble

“…The inter‐annual variability of the summer monsoon precipitation over South Asia is affected remotely by the sea surface temperature (SST) anomalies in the Pacific (Shukla & Paolina, 1983; Webster & Yang, 1992; Kumar, Rajagopalan, & Cane, 1999, among others) related to El Niño–Southern Oscillation (ENSO) and Atlantic (Cherchi, Kucharski, & Colleoni, 2018; Dogar, Kucharski, & Azharuddin, 2017; Syed & Kucharski, 2016; Yadav, Srinivas, & Chowdary, 2018), and it is also locally influenced by SST anomalies in the Indian Ocean (Cherchi & Navarra, 2013; Yuan, Yang, Zhou, & Li, 2008). For the boreal summer monsoon precipitation over Pakistan, several studies focused on the long‐term trend and variability using observational data and empirical models (e.g., Hartmann & Andresky, 2013; Iqbal & Athar, 2018; Khan, Ali, & Pilz, 2018; Adnan et al, 2020, among others).…”

The impact of varying seasonal lengths of the rainy seasons of India on its teleconnections with tropical sea surface temperatures

“…which shows a complex relationship at different lead/lag leading to contrasting interpretations of the teleconnection (Krishna Kumar et al, 1999;Kirtman and Shukla, 2000;Gershunov et al, 2001). The influence of the Indian ocean dipole and the tropical Atlantic Ocean on the ISM in contrast is far more subtle and at times used to understand the noncanonical ISM-ENSO seasons (Krishnamurthy and Kirtman, 2009;Yadav et al, 2018). Nonetheless, despite these teleconnections, the seasonal prediction of the ISM continues to be a challenge (Ramu et al, 2017;Pillai et al, 2018).…”