What is my research all about?
I am analyzing periods with low air quality in Bergen, Norway. Bergen is a coastal valley city at 60°N latitude, located between steep topography (mountains) and a sea inlet. The days in winter are short, and under fair weather conditions the city experiences frequent episodes of a phenomenon called “temperature inversions.”
In such a situation, the temperature rises with height (instead of decreasing with height, as it normally would). This is caused by the cooling of the ground that can occur during the long winter nights, in conditions of little to no sunlight and cloud-free skies. Since cooler air is heavier than warmer air, it stays low in the valley, and therefore, mixing with the warmer, cleaner air above is suppressed. When we also have low wind speeds, the air will “stand” in the valley, and emissions that would be diluted right away under normal conditions, keep accumulating, leading to poor air quality.
In my project I use a device called an MTP (Meteorological Temperature Profiler) that can measure the temperature profile of the atmosphere up to 1000meters above the valley ground (this device is an extended version of the instrument we have here on the ship). I also use data from local air quality stations. Later, a very high-resolution computer model can then simulate the small-scale turbulence of the atmosphere, and we use the model at an accuracy of within 40meters. My research will help us understand the occurrence of temperature inversions and the accumulation of pollutants in this valley, and hopefully improve the predictability of these occurrences.
Temperature inversions are also a common state of the lower Arctic atmosphere, due to the weak solar radiation in the polar regions. In the photo below, you can see the result of a temperature inversion occurrence in Bergen, with the layer of smog sitting low on the ground. In the next photo is the beautiful Arctic atmosphere during our expedition.
– Tobias Wolf
