Event characteristics of intra-seasonal climate circulations
An analysis of rainfall characteristics over the summer rainfall areas of South Africa is done in order to find links between rainfall variability and the general circulation. Seasonal rainfall totals are clearly linked to significant rain days, indicating the importance of evaluating synoptic-scale...
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ftunivcapetownir:oai:open.uct.ac.za:11427/38379 2023-12-03T10:30:20+01:00 Event characteristics of intra-seasonal climate circulations Tennant, Warren James Hewitson, Bruce 2002 application/pdf http://hdl.handle.net/11427/38379 eng eng Not Specified http://hdl.handle.net/11427/38379 Philosophy Doctoral Thesis Doctoral PhD 2002 ftunivcapetownir 2023-11-03T00:15:55Z An analysis of rainfall characteristics over the summer rainfall areas of South Africa is done in order to find links between rainfall variability and the general circulation. Seasonal rainfall totals are clearly linked to significant rain days, indicating the importance of evaluating synoptic-scale event characteristics. Rank ordered rainfall characteristics reveal that normal rainfall may be considered as the middle three quintiles, with the outer quintiles representing wet and dry conditions. The general circulation in tenns of atmospheric state (humidity and temperature), moisture and heat transport, and energy exchange - with attention to tropical-extratropical cloud-bands, are central to wet seasons in South Africa. These are generally associated with deep convection that is driven by vertical instability. Transport of moisture into South Africa generally takes place from the east with the Indian Ocean being a major source of water vapour. Although important, fluctuations in moisture transport are not clearly associated with rainfall. This is because moisture is a necessary but not a sufficient condition for rainfall. Atmospheric dynamics producing rainfall are a combination of disturbances of mid-latitude and tropical origin. These disturbances often initiate the tropical-temperate cloud-band where eddy available potential energy, generated through surface heating over land, is converted to eddy kinetic energy. It is generally mid-latitude disturbances with stronger vertical shear that are associated with rainfall events. Increased baroclinic activity in the Southern Ocean south of South Africa, as such, is generally associated with dry seasons. During these seasons there is usually a greater amount of available potential energy which strengthens the southern branch of the Hadley Cell. The effect of this is to increase the strength of the subtropical jet through enhanced poleward flux of angular momentum. The resulting increase in baroclinicity in the South Atlantic Ocean then disrupts rainfall over South ... Doctoral or Postdoctoral Thesis South Atlantic Ocean Southern Ocean University of Cape Town: OpenUCT Southern Ocean Indian |
institution |
Open Polar |
collection |
University of Cape Town: OpenUCT |
op_collection_id |
ftunivcapetownir |
language |
English |
topic |
Philosophy |
spellingShingle |
Philosophy Tennant, Warren James Event characteristics of intra-seasonal climate circulations |
topic_facet |
Philosophy |
description |
An analysis of rainfall characteristics over the summer rainfall areas of South Africa is done in order to find links between rainfall variability and the general circulation. Seasonal rainfall totals are clearly linked to significant rain days, indicating the importance of evaluating synoptic-scale event characteristics. Rank ordered rainfall characteristics reveal that normal rainfall may be considered as the middle three quintiles, with the outer quintiles representing wet and dry conditions. The general circulation in tenns of atmospheric state (humidity and temperature), moisture and heat transport, and energy exchange - with attention to tropical-extratropical cloud-bands, are central to wet seasons in South Africa. These are generally associated with deep convection that is driven by vertical instability. Transport of moisture into South Africa generally takes place from the east with the Indian Ocean being a major source of water vapour. Although important, fluctuations in moisture transport are not clearly associated with rainfall. This is because moisture is a necessary but not a sufficient condition for rainfall. Atmospheric dynamics producing rainfall are a combination of disturbances of mid-latitude and tropical origin. These disturbances often initiate the tropical-temperate cloud-band where eddy available potential energy, generated through surface heating over land, is converted to eddy kinetic energy. It is generally mid-latitude disturbances with stronger vertical shear that are associated with rainfall events. Increased baroclinic activity in the Southern Ocean south of South Africa, as such, is generally associated with dry seasons. During these seasons there is usually a greater amount of available potential energy which strengthens the southern branch of the Hadley Cell. The effect of this is to increase the strength of the subtropical jet through enhanced poleward flux of angular momentum. The resulting increase in baroclinicity in the South Atlantic Ocean then disrupts rainfall over South ... |
author2 |
Hewitson, Bruce |
format |
Doctoral or Postdoctoral Thesis |
author |
Tennant, Warren James |
author_facet |
Tennant, Warren James |
author_sort |
Tennant, Warren James |
title |
Event characteristics of intra-seasonal climate circulations |
title_short |
Event characteristics of intra-seasonal climate circulations |
title_full |
Event characteristics of intra-seasonal climate circulations |
title_fullStr |
Event characteristics of intra-seasonal climate circulations |
title_full_unstemmed |
Event characteristics of intra-seasonal climate circulations |
title_sort |
event characteristics of intra-seasonal climate circulations |
publisher |
Not Specified |
publishDate |
2002 |
url |
http://hdl.handle.net/11427/38379 |
geographic |
Southern Ocean Indian |
geographic_facet |
Southern Ocean Indian |
genre |
South Atlantic Ocean Southern Ocean |
genre_facet |
South Atlantic Ocean Southern Ocean |
op_relation |
http://hdl.handle.net/11427/38379 |
_version_ |
1784256116973109248 |