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Structure and Variability of the Oman Coastal Low-Level Jet
Stockholm University, Faculty of Science, Department of Meteorology . Lund University, Sweden.
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
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2015 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, 25285Article in journal (Refereed) Published
Abstract [en]

During the boreal summer strong southwesterly, coast parallel low-level winds prevail off the coast of Oman and over the Arabian Sea. The offshore large-scale structure and variability of these coastal winds has been a topic of numerous studies because of their strong connection to the south-Asian summer monsoon. However, low-level coastal jets along the coast of Oman have not been studied in detail, especially on a mesoscale level, despite their globally high frequency of occurrence. In the current study, regional atmospheric modeling has been utilized in an attempt to resolve the mesoscale structure, spatial variability and temporal characteristics of the Oman coastal low-level jet (CLLJ). The limited area model COAMPS® has been used at 6-km resolution for a five month period from May through September, during 2009. The model output compares favorably with the seasonal climatology for the coast of Oman.

In this study, analysis of high resolution model fields reveals the mesoscale structure of the Oman CLLJ, clearly distinguishing it from the large-scale southwesterly monsoon circulation farther offshore over the Arabian Sea. The Oman CLLJ is closer to the coast and spread northeastwards along the coast of Oman. Although the synoptic forcing that preconditions the Oman CLLJ is different from other areas of CLLJ occurrences, nevertheless, the jet is still driven primarily by the coastal baroclinicity due to sharp land-sea thermal contrasts. Within the study period, July exhibits the highest CLLJ frequency with ~80% occurrences and also manifests highest winds around 27 m s-1.

Place, publisher, year, edition, pages
2015. Vol. 67, 25285
Keyword [en]
coastal low-level jet, Oman, low-level jet, regional modeling
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-93150DOI: 10.3402/tellusa.v67.25285ISI: 000369825200001OAI: oai:DiVA.org:su-93150DiVA: diva2:645432
Available from: 2013-09-04 Created: 2013-09-04 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Global Climatology and Regional Modeling of Coastal Low-Level Jets
Open this publication in new window or tab >>Global Climatology and Regional Modeling of Coastal Low-Level Jets
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Localized coast-parallel wind-speed maxima at low altitude, known as coastal low-level jets (CLLJs) have important ramifications to the coastal climate and a number of human activities. This thesis documents the existence of the CLLJs around the globe including their mesoscale structure, dynamics and spatio-temporal variability.

A CLLJ-detection algorithm is presented, which identifies their occurrence and can distinguish between CLLJs and other types of low-level wind maxima. The method is based on vertical profiles of wind speed and temperature, and is applied to the ERA-Interim reanalysis dataset to obtain a 31-year-CLLJ climatology. Coastal jets are found to exist on many continents, including the previously undocumented CLLJs along the coasts of Oman and Iberian Peninsula. The study highlights a pronounced seasonality among the CLLJ regions and links to large-scale flow. The Oman coastal jet exhibits the globally highest CLLJ frequency (~70%).

The thesis also includes detailed analysis of the Oman and Iberian CLLJs using high-resolution regional modeling by dynamical downscaling. The Oman CLLJ is located close to the coast, at low altitude and is forced primarily by the coastal baroclinicity, unlike the previously known Somali-Jet, driven by the Asian summer-monsoon circulation. Although on a large-scale, the Oman CLLJ and the Somali jet appear to merge, the high-resolution simulations clearly illustrate that these are two distinctive phenomena with different forcing. The 20-year-climatology of the Iberian CLLJ reveals a strong seasonality with large inter-annual variations within spring, summer and autumn seasons while the maximum CLLJ frequency is found during the summer. Regional modeling studies were able to resolve detailed mesoscale structure of CLLJs, not visible from the coarse resolution reanalysis climatology. It is concluded that 6-km horizontal resolution can reproduce most of the small-scale features in a reasonable manner.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2013. 39 p.
Keyword
coastal low-level jets, climatology, regional modeling, boundary layer
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-93002 (URN)978-91-7447-743-6 (ISBN)
Public defence
2013-10-07, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
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Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.

Available from: 2013-09-16 Created: 2013-08-28 Last updated: 2013-09-04Bibliographically approved

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