As we reach the midpoint of HAMAG, let’s reflect on the campaign thus far. Our initial three flights have covered the region south and southeast of Kiruna and over the Bothnian Bay. The map below with a digital elevation model and sea ice concentration from the University of Bremen provides an overview of our flight trajectories.

The sea ice concentration map illustrates the closed sea ice in the northern bay and the open ocean towards the south on 9 February 2024. The transect of flight RF01 on this date covered both areas of the Bothnian Bay. Meanwhile, the other two flights focused on low clouds and fog formations over land.

We will continue to update this map to include upcoming research flights.

Today’s flight planning and go or no-go decision have not been easy. The overall situation has been similar to yesterday’s with haze all over Northern Sweden and Finland and the area around Kiruna airport showing a sunny sky with broken low-level clouds only, but with a forecast saying low visibility and difficult landing conditions throughout the day. After long discussions, we decided to go for a short survey, staying local to test different settings for GRaWAC to sense the low-level haze.

Up in the air, we tried different settings with the radars to see which works best with the thin haze. Although the haze was very thin and the ground was visible, both got a signal from time to time. To get an idea of temperature and humidity stratification, two dropsondes have been launched.

High pressure conditions gave us wonderfully sunny and crisp winter weather this weekend, but also made all the clouds disappear! We decided to target forecasted haze conditions towards Finland around Sodankylä to test our new radar GRaWAC’s sensitivity limits.
Good news: higher sensitivity to detect thin layers of cloud and haze, even close to the surface, compared to our existing cloud radar MiRAC! With today’s tests, we are optimistic that we will be able to detect Arctic haze over sea ice conditions around Svalbard, our survey area for upcoming campaigns where low-level haze is crucial for radiation characteristics. The fog today was mysterious – it looked like thicker clouds from far away, but once we reached the decks, conditions were such as seen below in the photo: we could see through it easily down to the ground. Our radar detected a 30m thickness.

We are making use of the weekend to plan upcoming flights for next week, and to start off with some coding to analyze first data measured on Friday. A high pressure system has been hanging around for a few days around, making the sky wonderfully blue without a single cloud in the vicinity of Kiruna.

Today, we took off at 10 am for the first survey flight over Bothnian bay – GRaWAC’s, our new G-band radar system’s, first time in the air! Fair weather conditions over the bay and great conditions for emissivity measurements over the frozen, clear-sky Northern bay part. Clouds were scarce, but once we reached open ocean, we started seeing them from the window, and in our radar measurements, well organized.

Next flight will be on Monday – stay tuned!

Research flight preparations have started!