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Inter-annual variability of rainfall in Central America: Connection with global and regional climate modulators
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. (AWEP)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Central America is a region regularly affected by natural disasters, with most of them having a hydro-meteorological origin. Therefore, the understanding of annual changes of precipitation upon the region is relevant for planning and mitigation of natural disasters. This thesis focuses on studying the precipitation variability at annual scales in Central America within the framework of the Swedish Centre for Natural Disaster Science. The aims of this thesis are: i) to establish the main climate variability sources during the boreal winter, spring and summer by using different statistical techniques, and ii) to study the connection of sea surface temperature anomalies of the neighbouring oceans with extreme precipitation events in the region.

Composites analysis is used to establish the variability sources during winter. Canonical correlation analysis is employed to explore the connection between the SST anomalies and extreme rainfall events during May-June and August-October. In addition, a global circulation model is used to replicate the results found with canonical correlation analysis, but also to study the relationship between the Caribbean Sea surface temperature and the Caribbean low-level jet.

The results show that during winter both El Niño Southern Oscillation and the Pacific Decadal Oscillation, are associated with changes of the sea level pressure near the North Atlantic Subtropical High and the Aleutian low. In addition, the El Niño Southern Oscillation signal is intensified (destroyed) when El Niño and the Pacific Decadal Oscillation have the same (opposite) sign.

Sea surface temperature anomalies have been related to changes in both the amount and temporal distribution of rainfall. Precipitation anomalies during May-June are associated with sea surface temperature anomalies over the Tropical North Atlantic region. Whereas, precipitation anomalies during August-September-October are associated with the sea surface temperature anomalies contrast between the Pacific Ocean and the Tropical North Atlantic region. Model outputs show no association between sea surface temperature gradients and the Caribbean low-level jet intensification. Canonical correlation analysis shows potential for prediction of extreme precipitation events, however, forecast validation shows that socio-economic variables must be included for more comprehensive natural disaster assessments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1438
Keyword [en]
Precipitation, climate variability, El Niño Southern Oscillation, Tropical North Atlantic, Canonical Correlation Analysis, EC-EARTH, Caribbean Low-Level Jet
National Category
Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:uu:diva-304656ISBN: 978-91-554-9716-3OAI: oai:DiVA.org:uu-304656DiVA: diva2:1033386
Public defence
2016-11-25, Axel Hambergsalen, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency, 54100006
Available from: 2016-10-31 Created: 2016-10-06 Last updated: 2016-11-02
List of papers
1. Variability of the Caribbean low-level jet during boreal winter: large-scale forcings
Open this publication in new window or tab >>Variability of the Caribbean low-level jet during boreal winter: large-scale forcings
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2016 (English)In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 36, no 4, 1954-1969 p.Article in journal (Refereed) Published
Abstract [en]

An index capturing the anomalies of the zonal wind at 925 hPa from 1950 to 2010 was defined to explore the relationship between the fluctuations of the Caribbean low-level jet (CLLJ) and the main climate variability modes affecting the Intra-Americas Sea Region. El Nino Southern Oscillation (ENSO) events, here defined using the Nino 3.4 index, are found to be the most important variability modes for the jet anomalies, in agreement with previous studies. However, the Pacific Decadal Oscillation (PDO) and the Pacific/North American (PNA) teleconnection pattern also show significant correlations with the CLLJ anomaly index during February. The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) reveal a possible interaction with the jet anomalies that could be connected with the cold fronts and cold air surges arriving to the Caribbean basin from the Northern Hemisphere during winter. A composite technique is used to explain the correlations with the Pacific indexes. We found that ENSO events are connected to CLLJ anomalies by modulating the sea-level pressure (SLP) near the east coast of the United States and the Aleutian Low. The pattern displayed by the SLP anomalies (SLPa) is also associated with the PNA. During warm (cold) ENSO phases, negative (positive) anomalies in the SLP field over the east coast of North America produce cyclonic (anticyclonic) circulations at low levels. However, the ENSO signal in the SLPa and the PNA pattern are modulated by the phases of the PDO. Results indicate that when the ENSO and PDO are in phase (out of phase), the SLPa signal is enhanced (weakened or cancelled), affecting the CLLJ anomalies in both direction and intensity, also changing the spatial distribution of precipitation.

Keyword
El Nino Southern Oscillation; Pacific Decadal Oscillation; Caribbean low-level jet; climate variability; ENSO non-linearities
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology; Meteorology
Identifiers
urn:nbn:se:uu:diva-263161 (URN)10.1002/joc.4472 (DOI)000372036800029 ()
Funder
Sida - Swedish International Development Cooperation Agency
Available from: 2015-09-28 Created: 2015-09-28 Last updated: 2016-10-07Bibliographically approved
2. Interannual variability of the midsummer drought in Central America and the connection with sea surface temperatures
Open this publication in new window or tab >>Interannual variability of the midsummer drought in Central America and the connection with sea surface temperatures
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2016 (English)In: Advances in Geosciences, ISSN 1680-7340, E-ISSN 1680-7359, Vol. 42, 35-50 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Uppsala: , 2016
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:uu:diva-287883 (URN)
Available from: 2016-04-26 Created: 2016-04-26 Last updated: 2016-10-07
3. The Role of the Meridional Sea Surface Temperature Gradient in Controlling the Caribbean Low-Level Jet.
Open this publication in new window or tab >>The Role of the Meridional Sea Surface Temperature Gradient in Controlling the Caribbean Low-Level Jet.
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(English)Manuscript (preprint) (Other academic)
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-304653 (URN)
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-07
4. The Early Rainy Season in Central America: the Role of the Tropical North Atlantic SSTs.
Open this publication in new window or tab >>The Early Rainy Season in Central America: the Role of the Tropical North Atlantic SSTs.
(English)Manuscript (preprint) (Other academic)
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-304655 (URN)
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-07
5. Seasonal prediction of extreme precipitation events and frequency of rainy days over Costa Rica, Central America, using Canonical Correlation Analysis
Open this publication in new window or tab >>Seasonal prediction of extreme precipitation events and frequency of rainy days over Costa Rica, Central America, using Canonical Correlation Analysis
2013 (English)In: Advances in Geosciences, ISSN 1680-7340, E-ISSN 1680-7359, Vol. 33, 41-52 p.Article in journal (Refereed) Published
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-304651 (URN)10.5194/adgeo-33-41-2013 (DOI)
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-07

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