Constant blowing snow accumulated on the road and made it impossible for the team to go up to the Ridge Lab. The high winds and cold temperatures that have persisted for the last couple of days worsened overnight, from Saturday to Sunday, and continued throughout the Sunday. Wind speeds at the lab were as high as 43 knots (close to 80 km/h). These sustained cold winds brought down temperatures inside the lab as the heaters struggled to compensate for the significant heat loss. As the road was completely drifted over, Pierre and Peter benefited from a ride up to the lab in the mattrack truck with the Weather Station's Senior Aerological Observer James. Upon arrival, Pierre and Peter took the limited time available to assess the situation and take measures to mitigate further heat loss.
Even though strong winds persisted throughout the afternoon on Sunday, the sky cleared up noticeably and the team took the opportunity to go for a walk around the station.
While the meteorological situation was already unusual at ground level, even more took place in the lower and middle stratosphere these days:
A major sudden stratospheric warming (SSW) already took place on 5 March. During this event, temperatures in the stratosphere rise considerably which alters chemical processes, in particular the conversion from so-called reservoir gases into 'active' ozone destroying substances. In addition, strong westerly winds commonly associated with the polar vortex turn into easterly winds poleward of 60° and often result in a dislocation of the vortex or even a vortex split. This year, the latter happened during the course of the days of March 11-13, depending on altitude. Even though this didn't take place directly over Eureka, since the vortex has rather been hovering over Scandinavia and northwestern Russia recently, the evolution of the polar vortex has an extensive influence.
No measurements were taken with the Bruker over the weekend. Saturday's snow drifts and blowing snow prevented the team to go to the Ridge Lab or to take measurements remotely. On Sunday morning, the team noticed that temperatures were getting low in most of PEARL's rooms, dropping below freezing in the IR lab at -2℃.
To prevent damage to the Bruker chiller, the mid-infrared source was turned on. This successfully kept the temperature at +6℃ inside the instrument and may have prevented the water inside the chiller to freeze for some time. When Pierre and Peter arrived at the Ridge Lab, they used a heater to keep the room warm. The IR lab went back up to positive temperatures. Erik and Sébastien will inspect the chiller as soon as it is possible to return to the Ridge Lab.
The PEARL-GBS experienced several problems over the weekend. The azimuth motor of the sun-tracker seems to be stuck, but since the Ridge Lab was inaccessible Kristof was unable to have a closer look. Due to the bad weather, the temperatures in the IR lab crawl space (where PEARL-GBS is located) have dropped to anomalously low values, and perhaps as a consequence the PEARL-GBS CCD was not recording spectra. Since it proved impossible to resolve the problem remotely, Kristof decided to turn the instrument off until temperatures return to normal. Since the UT-GBS is set up in a temperature controlled box, its operation was not affected by the cold.
Emily made another 24-hour measurement on 11 March UTC. It was another smooth day at CRL, but the data shows a giant, snowing cloud coming in at the end of the day, which would eventually require the lidar's hatch to be closed for much of 12 March UTC.
12 March UTC was a start-and-stop day for CRL. Emily made measurements at the start of the day, revealing the continuation of the thick, snowing cloud from the day before. Only 4.5 hours of measurement were possible before the snow accumulation on the hatch became too much and the count rates dropped drastically. The hatch was closed at 4:30 UTC and for the following 14 hours, while the snow on the window sublimated, and then while waiting for the high winds to die down. By 18:30, measurements began again, revealing much thinner clouds in two to three discontinuous layers: One between 500 m and 1500 m, the next at 2500 m, and the top one at 5000 m. Measurements continued until 22:30 at which point the hatch had to be closed again due to high winds. Interesting skies make for interesting lidar measurements - but only when the hatch can be open! Emily is hoping for more continuous operations to be possible during the next day.
Neither Ellen nor Ghazal could take any measurements during the weekend and no ozonesonde could be launched due to the strong winds and blowing snow.
The team hopes the strong winds will wear off soon, so that the instruments at the Ridge Lab can be checked and measurements can be resumed.