Is the Atlantic Ocean driving the recent variability in South Asian dust?
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 satel...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/acp-2020-1305 https://acp.copernicus.org/preprints/acp-2020-1305/ |
| Summary: | 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. |
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