Wednesday turned out to be the first day with slightly overcast skies and haze. Towards the afternoon, it became entirely overcast with decreasing visibility and blowing snow. The temperature dropped from around -26℃ at 9 am local time, when the team arrived at the Ridge Lab, to almost -32℃ in the afternoon. While the wind speed was clearly less than 10 m/s during the night, it picked up in the early morning reaching maximum speeds of close to 20 m/s around 10 am and only slowed down slightly during the day.
The first cloudy day provided Sébastien and Erik with the opportunity to perform cell tests measurements with the Bruker 125HR. Today, they performed an HBr cell test by first switching on the source cooler and internal infrared source. A background spectrum was then acquired by measuring the internal source with no cell in the instrument. Once this was complete, they vented the instrument and inserted the HBr cell. Sébastien and Erik then evacuated the instrument and ran a cell test measurement. Erik will process the results of this cell test measurement soon. Sébastien and Erik plan to resume mid-infrared measurements tomorrow if the weather permits.
Kristof finished the lab tests for the PEARL-GBS. The strong winds prevented him from working on the roof, so progress in fixing the PEARL-GBS sun-tracker has been slow. All the spare parts are now ready and Kristof is confident that the tracker can be fixed once the roof is accessible again.
PARIS-IR had been running during the night, because the file transfer of the previous day couldn't be completed before the team had to leave the Ridge Lab on Tuesday. Ellen restarted the instrument in the morning and, due to the tricky weather conditions, decided to take background measurements with PARIS-IR. After carefully adjusting the pick-off mirror and the globar, she started routine measurements around 10 am local time. These ran without problems until the software to control PARIS-IR froze at 12:24 pm. Ellen spent some time on the issue, getting PARIS-IR back on track at 2:23 pm. She stopped measuring at 3:43 pm after taking 27 measurements in total.
The CRL made regular measurements for 14.25 hours on 1 March (UTC). The day began with clouds at about 1 km altitude, and CRL saw clouds at increasing altitudes for the following 6 hours. The lidar was closed at 8:08 UTC because of high winds and blowing snow at 0PAL. By the time it reopened at 12:55 UTC, the sky had completely cleared up. Conditions were still windy, however, and this period of measurement lasted only 3 hours before the lidar had to be closed again at 16:13 UTC. It reopened at 19:42 UTC to skies which were still quite clear, and finished out the night making measurements. Although this was quite an interrupted day in terms of opening and closing the lidar, the non-measurement times were put to quite good use: The first closed period was used to make dark count measurements which help us to interpret the analogue signals in our detectors. These measurements must be made each season, with the hatch closed, and this was a good opportunity to do them. The second closed period, in the afternoon, was full of more activity: Ghazal came to CRL and Emily showed her the ropes (and lasers and electronics and telescope and other optics etc.) during a thorough tour of the laboratory. Before leaving, when the lidar could be turned on again, they did some burn tests to check alignment so that Ghazal could see how this is carried out.
In the evening of March 1, Ghazal and Peter went to the ridge lab to operate the DIAL lidar. At the beginning of the operation, the power in the laser dropped down significantly. The hydrogen chloride gas was injected into the laser. As a result, the laser went back to operate with the desired power. The beam alignment was pretty tricky but by 12:00 am local time the DIAL system was fully operational. Data were collected from 12:00 am to 7:30 am local time.
An ozonesonde was launched at 6:15 pm local time again. The same balloon model as yesterday was used. Today, it took off into a southwestern direction, but quickly changed to southeast where it reached its maximum altitude of 34009 m. It rose with an ascent rate of 225 m/minute.