Forecasting of polar storms

My role in the research project that I work at is to explore the links between cold air outbreaks over the ocean and large weather patterns. Here’s a popular science piece I wrote on a recently published article:

A new study represents a step towards better forecasting of severe weather in polar regions. Cold air outbreaks over the ocean can be linked to large-scale weather patterns, and this leads the way to using new tools to forecast such events.

Marine cold air outbreaks are the breeding grounds of severe weather in the maritime polar regions. An MCAO is a large-scale departure of cold air, typically from regions covered with sea ice, into regions with open ocean. The temperature contrast between the (relatively) warm ocean and the air can be more than 20 degrees Celsius, and this leads to rising air and the development of low-pressure systems. The best-known weather phenomenon associated with MCAOs is the polar low. Sometimes compared to hurricanes, although smaller in scale, these cyclones can produce hurricane-force winds and large amounts of snow. MCAOs therefore form a significant part of the marine hazard in populated coastal regions of Norway, Russia, Iceland, Japan and even the British isles. MCAOs are also important factors in determining the amount of heat that is lost from the ocean to the air during winter. Such heat loss is associated with deep-water formation and the strength of the oceanic thermohaline circulation, the Great Ocean Conveyor. In a new study, published in Climate Dynamics and led by Bjerknes researcher Erik Kolstad, the correspondence between large-scale weather patterns and MCAOs is explored. Over the Nordic Seas region, a pronounced high-pressure anomaly over Greenland, either acting alone or in concert with a strong low-pressure anomaly over northeastern Europe, were shown to be favourable for MCAOs to form. This is potentially important because such conditions are linked to negative phases of the North Atlantic Oscillation, the primary weather pattern in the North Atlantic region. This means that any progress in medium and long range forecasting of the NAO – a large research field – may also be translated to enhanced forecasting of MCAOs.

Complete reference: Kolstad, E. W., Bracegirdle, T. J. & Seierstad, I. A. (2009), Marine cold-air outbreaks in the North Atlantic: temporal distribution and associations with large-scale atmospheric circulation, Climate Dynamics, 33(2), 187-197.

A pre-print of the article can be downloaded here.

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