Monday started of with clear skies around midnight, but in the early morning high clouds and ice crystals started to form. Shortly before breakfast (7:30 am local time at Eureka), these turned into moderately high clouds. Around noon, the sky was covered by lower clouds and light snow started to set in. These conditions persisted through the rest of the day. Visibility was still rather good when the team arrived at the Ridge Lab at about 9:00 am. In the early afternoon, everyone gathered in the living room to attend the PAHA-EC collaboration teleconference on working together with the International Arctic System for Observing the Atmosphere project. The team went back to the Eureka weather station at around 4:30 pm. By this time, the weather conditions had changed drastically and viewing distance had decreased tremendously.
In the IR lab, Erik and Sébastien decided to do a HCl cell test measurement with the InGaAs detector dedicated to TCCON observations. They first vented the instrument to replace the KBr beamsplitter with the CaF2 beamsplitter. The HCl cell is always in place in the front sample compartment of the instrument. After evacuating the instrument, Erik and Sébastien took an HCl cell test measurement with an optical path difference (OPD) of 45 cm and another one with an OPD of 65 cm. Sébastien will process the results of the HCl cell test. Before heading back to the Eureka weather station, Erik and Sébastien repeated to beamsplitter swap operation and the KBr beamsplitter is back in the Bruker 125HR spectrometer. Thus, the instrument is ready to resume mid-infrared measurements as soon as weather permits.
Kristof continued monitoring the PEARL-GBS sun-tracker in case the previous problems reappeared, but the instrument continued to operate without any issues. Today's clouds prevented direct sun measurements, so both instruments continued to operate in zenith sky - MAX-DOAS mode.
At the 6th of March UTC, Emily made CRL measurements for the full 24 hours, and was able to produce some plots for colleagues to look at for this and previous campaign days.
Due to the cloudy conditions during the night from Sunday to Monday, Ghazal couldn't do final alignment tests for the DIAL, since that requires clear sky conditions.
Another Raven ozonesonde was released at 6:15 pm. At an ascent rate of 197 m/minute, it made it to an altitude of 35414 m. After a tiny loop mid-way, it ended up about 196 km south of Eureka.