Retired since 2024, I rarely teach much anymore but over my career I have been teaching most of the core courses in "dynamic meteorology" on way or another over many years. This includes Dynamic Meteorology, Mesoscale Meteorology and Boundary-Layer Meteorology; the two latter also at the graduate level.

I have also been teaching overview courses, on both Meteorology and Climate, and still sometimes give public popular-science lectures on climate and climate change, and especially on the Arctic. I also sometimes communicate science in media. For example you can listen to my "Sommar i P1" from 2019 at: https://www.sverigesradio.se/avsnitt/michael-tjernstrom.

My research over the last 25 years has been focussing on the Arctic climate system. The Arctic experiences the fastest climate change on Earth. Annually averaged near-surface temperatures are increasing on average up to 4 times faster in the Arctic than globally and as a consequence the sea ice is disappearing rapidly with consequences for both global climate, ecosystem and society.

The melting and freezing of the sea ice is determined by the surface energy budget. While the turbulent fluxes of heat and water vapor are important, the leading terms are the radiation fluxes, very strongly affected by clouds. Low-level clouds dominate the Arctic sky; summer is cloudy ~80-90% of the time and for winter 50-70%. Clouds in turn also affect the vertical structure of the atmospheric boundary layer and hence the turbulent surface fluxes. Cloud free conditions typically lead to a surface cooling most of the year and surface inversions with stable stratification. Cloudy conditions warm the surface and give rise to a shallow well-mixed structure; all of this is very tightly coupled! 

However, numerical weather prediction and climate models have a very hard time describing this. In my research I use field experiment processs level observations from icebreaker-based expeditions to the central Arctic Ocean.

I have developed an atmospheric observatory for the Swedish research icebreaker Oden, that has now become a part of a national infrastructure, to generate more observations to directly enhance the understanding of the Arctic atmosphere and to inform modeling and model development for all time scales. The observatory is based on two leading ideas. First, to measure as much as practically possible of the vertical atmospheric column above the ship, using a combination of in-situ and remote sensing instruments. Second, to do this with instruments that require minimum staff, to increase the likelihood that the observatory is deployed as often as possible.