Is the Atlantic Ocean driving the recent variability in South Asian dust?
<p>This study investigates the large-scale factors controlling interannual variability in dust aerosols over South Asia during 2001–2018. We use a parameter DA<span class="inline-formula"><sub><i>%</i></sub></span>, which refers to the frequency of...
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| Autores principales: | , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/7175e781be0b46cdb48fd809daf496c5 |
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| Sumario: | <p>This study investigates the large-scale factors controlling interannual
variability in dust aerosols over South Asia during 2001–2018. We use a
parameter DA<span class="inline-formula"><sub><i>%</i></sub></span>, which refers to the frequency of days in a year when
high dust activity is experienced over a region, as determined by a
combination of satellite aerosol optical depth and the Ångström exponent. While a
positive sea surface temperature (SST) anomaly in the central Pacific Ocean
was important in controlling DA<span class="inline-formula"><sub><i>%</i></sub></span> over South Asia during
2001–2010; in recent years, the North Atlantic Ocean has assumed a dominant
role. Specifically, high DA<span class="inline-formula"><sub><i>%</i></sub></span> is associated with warming in the
midlatitude and cooling in the subtropical North Atlantic SSTs: the
location of 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<span class="inline-formula"><sub><i>%</i></sub></span> over South Asia coincides with a recent shift towards
a persistently positive phase of the North Atlantic oscillation (NAO) and a
resultant positive phase of the springtime 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 troposphere
and mid-troposphere. Simulations with an Earth system model show that the
positive phase of the North Atlantic SST tripole pattern is responsible for a
10 % increase in the dust optical depth over South Asia during May–September;
with increases as high as 30 % during the month of June. This increase is
mainly due to transport by the westerlies at the 800 hPa pressure level, which increases the dust concentration at this pressure level by 20 % on average
during May–September and up to 50 % during June.</p> |
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