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.
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 cold 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.
Weather patterns and cold air outbreaks
The study shows that 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 over the Nordic Seas region. 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.