On the intra-seasonal to decadal climate variability over South-Asia
South Asia, a land of contrasting landscapes, seasons and climates, is highly vulnerable to climate variability over intra-seasonal to decadal time scales. In winter, precipitation over the western parts of south Asia and fog over the Indo-Gangetic (IG) plains are the two major climatic features. Du...
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2011
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ftstockholmuniv:oai:DiVA.org:su-62988 2023-05-15T17:36:50+02:00 On the intra-seasonal to decadal climate variability over South-Asia Syed, Faisal Saeed 2011 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62988 eng eng Meteorologiska institutionen (MISU) Stockholm : Department of Meteorology, Stockholm University http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62988 urn:isbn:978-91-7447-375-9 info:eu-repo/semantics/openAccess South Asia monsoon western disturbances fog climate variability climate dynamics teleconnections ENSO NAO CGT Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning Doctoral thesis, comprehensive summary info:eu-repo/semantics/doctoralThesis text 2011 ftstockholmuniv 2023-02-23T21:43:43Z South Asia, a land of contrasting landscapes, seasons and climates, is highly vulnerable to climate variability over intra-seasonal to decadal time scales. In winter, precipitation over the western parts of south Asia and fog over the Indo-Gangetic (IG) plains are the two major climatic features. During summer most of the region comes under the grip of monsoon. Winter precipitation over the north-western parts of South Asia is associated with eastwards propagating ‘western disturbances’ originating mostly from Mediterranean. Both observations and regional climate-model simulations show that the winter precipitation increases/decreases during the positive/negative phases of the North Atlantic Oscillation (NAO) and the warm/cold phase of the El Niño-Southern Oscillation (ENSO). During these phases, the intensification of western disturbances results from the effect of an enhanced trough visible at sea-level as well as at higher altitudes over central Asia. The inter-annual variability of fog is coupled over IG plains with a significant trend in the fog frequencies, both in observations and ERA-Interim reanalysis data. This increase shows two distinct regime shifts in 1990 and 1998 with respect to mean and variance, this in contrast to a gradual increase of the humidity over the region. The thermodynamic analysis of the intra-seasonal summer monsoon active phases (APs) over Pakistan revealed that a few days before AP, an upper-level warm anomaly appears over the northern Hindu Kush-Himalaya region and is reinforced by surface heating. The baroclinic height anomalies, with a low-level anticyclone located east of the warming, causes a moisture convergence, strong enough to overcome the preexisting stable atmospheric conditions. The extratropical dynamics also play an important role for the inter-annual variation of the South-Asian monsoon. It is found that the two leading modes between the upper-level circulation in the Atlantic/European region and monsoon rainfall are the Circumglobal Teleconnection (CGT) and the ... Doctoral or Postdoctoral Thesis North Atlantic North Atlantic oscillation Stockholm University: Publications (DiVA) |
institution |
Open Polar |
collection |
Stockholm University: Publications (DiVA) |
op_collection_id |
ftstockholmuniv |
language |
English |
topic |
South Asia monsoon western disturbances fog climate variability climate dynamics teleconnections ENSO NAO CGT Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning |
spellingShingle |
South Asia monsoon western disturbances fog climate variability climate dynamics teleconnections ENSO NAO CGT Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning Syed, Faisal Saeed On the intra-seasonal to decadal climate variability over South-Asia |
topic_facet |
South Asia monsoon western disturbances fog climate variability climate dynamics teleconnections ENSO NAO CGT Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning |
description |
South Asia, a land of contrasting landscapes, seasons and climates, is highly vulnerable to climate variability over intra-seasonal to decadal time scales. In winter, precipitation over the western parts of south Asia and fog over the Indo-Gangetic (IG) plains are the two major climatic features. During summer most of the region comes under the grip of monsoon. Winter precipitation over the north-western parts of South Asia is associated with eastwards propagating ‘western disturbances’ originating mostly from Mediterranean. Both observations and regional climate-model simulations show that the winter precipitation increases/decreases during the positive/negative phases of the North Atlantic Oscillation (NAO) and the warm/cold phase of the El Niño-Southern Oscillation (ENSO). During these phases, the intensification of western disturbances results from the effect of an enhanced trough visible at sea-level as well as at higher altitudes over central Asia. The inter-annual variability of fog is coupled over IG plains with a significant trend in the fog frequencies, both in observations and ERA-Interim reanalysis data. This increase shows two distinct regime shifts in 1990 and 1998 with respect to mean and variance, this in contrast to a gradual increase of the humidity over the region. The thermodynamic analysis of the intra-seasonal summer monsoon active phases (APs) over Pakistan revealed that a few days before AP, an upper-level warm anomaly appears over the northern Hindu Kush-Himalaya region and is reinforced by surface heating. The baroclinic height anomalies, with a low-level anticyclone located east of the warming, causes a moisture convergence, strong enough to overcome the preexisting stable atmospheric conditions. The extratropical dynamics also play an important role for the inter-annual variation of the South-Asian monsoon. It is found that the two leading modes between the upper-level circulation in the Atlantic/European region and monsoon rainfall are the Circumglobal Teleconnection (CGT) and the ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Syed, Faisal Saeed |
author_facet |
Syed, Faisal Saeed |
author_sort |
Syed, Faisal Saeed |
title |
On the intra-seasonal to decadal climate variability over South-Asia |
title_short |
On the intra-seasonal to decadal climate variability over South-Asia |
title_full |
On the intra-seasonal to decadal climate variability over South-Asia |
title_fullStr |
On the intra-seasonal to decadal climate variability over South-Asia |
title_full_unstemmed |
On the intra-seasonal to decadal climate variability over South-Asia |
title_sort |
on the intra-seasonal to decadal climate variability over south-asia |
publisher |
Meteorologiska institutionen (MISU) |
publishDate |
2011 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62988 |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_relation |
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62988 urn:isbn:978-91-7447-375-9 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766136452132896768 |