The Spitsbergen South Cape tip jet

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Reeve, Mathew A., Kolstad, Erik W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2011
• Subjects: Barents Sea; Norwegian Sea; Svalbard; Spitsbergen
• Online Access: http://dx.doi.org/10.1002/qj.876; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.876; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.876

Abstract We investigated low‐level tip jets generated at the southern tip of the island of Spitsbergen, part of the Svalbard archipelago in the Arctic. Low‐level tip jets occur in many locations where airflow converges around obstacles, such as islands. They are often poorly resolved in forecasts or re‐analyses, so it is important to document their locations and shed light on why they occur. Tip jets are the result of flow stagnation and flow splitting upstream of an obstacle; both of these processes are dependent on the stability of the air column, wind speed and direction upstream. Jets generated around Sørkapp, the southern cape of Spitsbergen, have been resolved previously in numerical studies, but no climatology exists. In this study, we used the Weather Research and Forecasting model (WRF) to demonstrate the influence of topography on the development of tip jets. We used QuikSCAT satellite‐derived surface wind data to identify tip jet events and compile climatologies, and the ERA‐Interim data to investigate the prevailing synoptic conditions during jet events and identify the main driving forces. We found that tip jets can occur throughout the year, associated with a negative surface‐level pressure anomaly moving in a northeast direction from the Norwegian Sea and towards the Barents Sea. On average, jets occurred just over 8% of days throughout the year. The maximum 60‐day running mean of occurrence was around 12% and occurred between February and March. The results showed that negative wind speed and positive static stability anomalies were statistically significant upstream of the island group. These anomalies remain significant when seasons of high, middle and low occurrence were analysed separately. We conclude therefore that wind direction persistence may play an important role in the seasonality of jet occurrences in the study region. Copyright © 2011 Royal Meteorological Society