While it was still slightly hazy, only thin clouds obstructed the Sun for most of Thursday, February 27. The temperature at the weather station hadn't changed considerably from previous days and mainly hovered around -40°C. It wasn't very windy at either Eureka or the PEARL Ridge Lab. The temperature at the Ridge Lab remained at just below -30°C for the entire day. The team went up to PEARL at 8:30 AM and used the improved conditions to take measurements and further adjust some of the instruments. Kristof, Ramina and Ellen also briefly went to the roof to take pictures. The team made their way back to the weather station around 4:30 PM.
The Sun rose above the layer of cloud around noon, so Tyler and Beatriz were able to get some filter 6 and filter 3 measurements. In total, they were able to get 8 Filter 3 measurements and 7 Filter 6 measurements. Since there was a thin layer of cloud in front of the Sun, they increased the number of co-added spectra from two to four to increase the signal to noise ratio. They were also able to make the first set of measurements with the EM27/SUN. There was an issue with the MIR auto-measurement macro which was caused by an incorrect file path in one of the sub-macros. So Tyler and Beatriz were forced to collect the spectra manually. However, they were able to locate and fix this bug near the end of the day, so now the macro should be ready to use on the next sunny day. There was a tense moment, when they briefly lost connection to the Bruker through the Bruker PC, but a restart of the instrument solved this issue.
Kristof and Ramina continued the PEARL-GBS lab tests, which included a stray light test and some repetitions of Wednesday's tests for reproducibility. They then began a dark current test just after returning the PEARL-GBS to its original location in the IR lab mezzanine. The goal for Friday is to finalize the PEARL-GBS lab tests and fix the tracker issue, weather permitting. Kristof and Ramina also worked with the Pandora instrument to begin the solar alignment procedure and will continue with that on clear sunny days.
During the night from Wednesday to Thursday (February 26 to February 27), Ali started preparing the DIAL around 6:30 PM. The routine procedure includes warming up the laser and aligning the beam, and measurements started around 6:45 PM although the background was high. Around midnight clouds passed over the DIAL and light snow set in. Ali stopped the DIAL at 1:30 AM due to snow and thick clouds.
The frost had built up some more over the cold night from Wednesday to Thursday but the SPS tracker and instrument continued to function nonetheless. Excellent ozone and NO2 data were collected at both sunrise and sunset and throughout the day.
The team is encouraged by yesterday's weather and is hoping for conditions to improve even further during the following days.
Cheers,
Ellen Eckert
[on behalf of the 2020 Canadian Arctic ACE/OSIRIS Validation Campaign]