A Polar Low Flight

A small delegation of atmospheric modellers from the University of Bergen had the possibility to visit the ACCACIA field campaign. With the idea that meeting experimental meteorologists and looking out of the window instead of staring at a computer screen would broaden our views we went off to Kiruna. My PhD-project is about the dynamics of polar lows, also known as arctic hurricanes. These winter storms are well known by local fishermen and people living along the north-west coast of Norway for their sudden appearance and are usually accompanied by heavy snowfall and hurricane force winds. So far March had been a month of high polar low activity, including the period of the ACCACIA field campaign. Despite the focus of the campaign on aerosols and clouds, there’s always a chance that other meteorological features can become the target for the day.

Plan B became reality: we went off to fly into a polar low! There was a remarkable agreement between the met.no forecast and the latest satellite overpass, so we were very likely to actually find the polar low (usually the forecast and reality don’t match that well). It was my first flight on a research aircraft and this plane looks like one big instrument, everywhere on the outside there are instruments mounted and the inside has some seats, but most of the space is occupied by instrument racks and screens.

Flight Manager

Steph & Matt at the flight manager’s console

After take-off from Kiruna we headed straight to the polar low area. First two legs in the polar low zone were at high altitude, zzzzzzhp and another dropsonde is doomed to have a seaman’s grave… We dropped 11 of those, providing us with a nice glimpse of the state of the atmosphere, and than descended to finish with two low legs. Really low legs: approximately 100ft over a rough ocean state: high demand flying for the pilots (and too bumpy to take pictures), as far as I know this is one of very few direct measurements of the surface fluxes in a polar low. As the dropsonde data indicated, and now confirmed by looking out of the window: we were at the right location. Flying into wind speeds around 25 m/s and looking down at rough sea states, which changed suddenly into a calm and cosy ocean with wind speeds around 5m/s. A remarkable change, often mentioned by fishermen: it looks like a black wall is coming towards you and within a few minutes there is a transit from calm conditions to severe storm…

Annick Terpstra

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About Ian Brooks

Trained as a physicist, sidetracked into meteorology, and slowly working my way down to the oceans - I am a Professor in atmospheric science in the School of Earth and Environment, at the University of Leeds. I do research in boundary-layer processes, air-sea interaction, and Arctic meteorology & climate.

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