Two Sentry SVS-1 visibility sensors were installed at the Iqaluit Weather Office site. One instrument was an RS-232 Output version (Visibility 1), while the second was Analog version (Visibility 2) of the instrument. The instruments had measurement ranges of 30 m to 16 km with an accuracy of ± 10%. Both sensors were set to sample once every minute, and mounted at a height or 1.5 m.

Visibility 1 (RS-232 output) was positioned on the east side of the Upper Air shed at the Weather Office during the fall field campaign. The data files were logged using an Acumen Data Logger, and stored on a compact flash card. Data files are in *.dat format where they contain date, time, sensor output voltage (VDC), visibility in (km). To derive the visibility from the VDC the following formula was used: σ km-1 = 20* (0.150/VDC).

Visibility 2 (Analog output), was positioned with the 10-m tower automatic weather station (A3) and the Weather Office site. A Campbell Scientific CR23X data logger was used to log the data. Data files are in a simple *.csv format where they contain date, time, visibility (km). To derive the visibility from the VDC the following formula was used: σ km-1 = 20* (0.150/VDC).

Data from this instrument was downloaded daily during the Fall period and weekly during the winter period. This was accomplished by exchanging the CF card in the data logger. The CF card was then brought into the Environment Canada weather office, where it was offloaded onto the STAR desktop computer. To exchange the CF cards, the data logger had to be turned off for periods between 1-5 minutes. As a result, 1-5 minutes of data is missing during these time periods.

This instrument moved over to the 10-m tower weather station (A3) for the winter blowing snow project (Feb 1- March 30). The same downloading procedure was adpated , however downloads occurred on a weekly basis. See Visibility 1 Winter metadata form for more info.