Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Modelling coastal low-level wind-jets: does horizontal resolution matter?
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
2016 (English)In: Meteorology and atmospheric physics (Print), ISSN 0177-7971, E-ISSN 1436-5065, Vol. 128, no 2, 263-278 p.Article in journal (Refereed) Published
Abstract [en]

Atmospheric flows in coastal regions are impacted by land-sea temperature contrasts, complex terrain, shape of the coastline, among many things. Along the west coast of central North America, winds in the boundary layer are mainly from north or northwest, roughly parallel to the coastline. Frequently, the coastal low-level wind field is characterized by a sharp wind maximum along the coast in the lowest kilometer. This feature, commonly referred to as a Coastal Low-Level Jet (CLLJ), has significant impact on the climatology of the coastal region, influencing aviation, shipping, fishing and a number of other human activities along the littoral zone, and better understanding and forecasting of this is vital.

The purpose of this study is to elucidate the issue of proper resolution in a mesoscale numerical model to describe the physics of a CLLJ, and its impact on the upper ocean. The COAMPS® model is used for a summer event to determine the realism of the model results compared to observations, from an area of supercritical flow adjustment between Pt. Sur and Pt. Conception, California. Simulations at different model horizontal resolutions, from 54 km to 2 km are performed. While the model produces realistic results with increasing details at higher resolution, the results do not converge even at a resolution of only few kilometers and an objective analysis of model errors do not show an increased skill with increasing resolution. New methods may thus have to be developed to evaluate models at very high resolution. Based on all available information, a compromise resolution appears to be at least 6 km.

Place, publisher, year, edition, pages
2016. Vol. 128, no 2, 263-278 p.
Keyword [en]
low-level coastal jets, COAMPS, model resolution, scale dependence, mesoscale meteorology
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-93148DOI: 10.1007/s00703-015-0413-1ISI: 000373304700009OAI: oai:DiVA.org:su-93148DiVA: diva2:645418
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)
Opponent
Supervisors
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

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Ranjha, RazaTjernström, MichaelSvensson, Gunilla
By organisation
Department of Meteorology
In the same journal
Meteorology and atmospheric physics (Print)
Meteorology and Atmospheric Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 218 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf