March 9 was another rather cold but sunny day with great visibility, so the team took off to the Ridge Lab in the morning and started measurements once they got there. Temperatures at Eureka stayed close to -47°C the entire day and hovered mainly around -34°C at the Ridge Lab. However, with the windchill temperatures on the ridge were closer to -46°C. Since measurements were running smoothly, the team went for a short hike in the afternoon and enjoyed the fantastic scenery. When they were about to head down to the weather station in the afternoon, Pierre found the front tire on one of the trucks had a flat. He and Alexey changed the tire and they made their way back with Ramina and Ellen. They arrived at Eureka at around 5:45 PM where they were welcomed with a warm meal despite the delay. Tyler, Beatriz and Kristof were taken out to the iceberg in the fiord by Eureka SPM Scott just after dinner. The following morning, Scott and Eureka SPM-in-training Andrew gave Ramina, Ali and Ellen a ride out on the fiord to see the Sun rising over the icebergs.
Since it was clear and sunny, Beatriz and Tyler started mid-infrared measurements with the Bruker 125HR and EM27/SUN around 9 AM. At 11:30 AM local time, they swapped the beamsplitters from the KBr (potassium bromide) one used for the mid-infrared measurements to the CaF2 (calcium fluoride) used for the near-infrared measurements. They then took the first 50 near-infrared TCCON spectra of the year, which will be used in the comparisons between the 125HR and the EM27/SUN. The TCCON measurements require solar zenith angles below 85 degrees, so the period around noon was ideal for these measurements. At 3 PM, they changed the beamsplitter back to the KBr and took mid-infrared measurements for the remainder of the day. In total, they collected 49 mid-infrared spectra and 50 near-infrared spectra, as well as approximately 1800 interferograms with the EM27/SUN.
With clear and sunny skies for the past few days, Kristof and Ramina continued processing the zenith sky measurements from the PEARL-GBS and UT-GBS. Their analysis was similar to previous years, indicating that the instruments are in great shape for the measurement period.
Ali and Alexey took measurements with DIAL between 9 PM and 4:30 AM during the night of Sunday, March 8, to Monday, March 9. 9 PM seems to be a bit early by now as the background was high when they started measurements. They kept the DIAL running on the same schedule regardless, since it is always possible to throw out part of the data at a later time. Ali went up to the Ridgelab on Sunday and spent the morning cleaning the laser optics.
The CRL made 24 h of measurements on 8 March 2020, and measurements continue.
Another "Raven" was launched on Monday, March 9, and made it to 20072 m (39.0 hPa).
Thanks to the generosity of the Eureka Weather Station staff and the amazing weather the team enjoys their last days in the high Arctic to the fullest.
Cheers,
Ellen Eckert
[on behalf of the 2020 Canadian Arctic ACE/OSIRIS Validation Campaign]