Preprints
https://doi.org/10.5194/acp-2020-1305
https://doi.org/10.5194/acp-2020-1305

  10 Feb 2021

10 Feb 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

Is the Atlantic Ocean driving the recent variability in South Asian dust?

Priyanka Banerjee1, Sreedharan Krishnakumari Satheesh1,2, and Krishnaswamy Krishna Moorthy2 Priyanka Banerjee et al.
  • 1Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, India
  • 2Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India

Abstract. This study investigates the large-scale factors controlling interannual variability of dust aerosols over South Asia during 2001–2018. We use a parameter DA%, which refers to the frequency of days in a year when high dust activity is experienced over a region, as determined by combination of satellite aerosol optical depth and Angstrom exponent. While positive sea surface temperature (SST) anomaly in the central Pacific Ocean has been important in controlling DA% over South Asia during 2001–2010; in recent years the North Atlantic Ocean has assumed a dominant role. Specifically, high DA% is associated with warming in the mid-latitude and cooling in the sub-tropical North Atlantic SSTs: the two southern arms of the North Atlantic SST tripole pattern. This shift towards a dominant role of the North Atlantic SST in controlling DA% over South Asia is associated with a recent shift towards persistently positive phase of the North Atlantic Oscillation (NAO) and a resultant positive phase of the spring-time SST tripole pattern. Interestingly, there has also been a shift in the relation between the two southern arms of the SST tripole and NAO, which has resulted in weakening of the southwest monsoon circulation over the northern Indian Ocean and strengthening of the dust-carrying westerlies and northerlies in the lower and mid-troposphere. Simulations with an earth system model show that anomalous transport due to the North Atlantic SST tripole pattern can result in 10 % (20 %) increase in dust optical depth (concentration at 800 hPa) over South Asia during May–September; with increases as much as 30 % (50 %) during the month of June.

Priyanka Banerjee et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2020-1305', Jerome Brioude, 30 Jun 2021
  • RC2: 'Comment on acp-2020-1305', Anonymous Referee #2, 22 Jul 2021

Priyanka Banerjee et al.

Priyanka Banerjee et al.

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Short summary
This study shows that in recent years the Atlantic Ocean is the major driver of interannual variability of dust load over South Asia. This is a shift from the previously important role played by the Pacific Ocean in controlling dust transport over South Asia. With the end of the recent global warming hiatus, the North Atlantic sea surface temperatures have remotely weakened the South Asian monsoon, while strengthening the dust-bearing wind over this region.
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