John Prytherch Ceilometer backscatter, cloud base height and cloud fraction data from the Arctic Ocean 2018 expedition Bolin Centre Database 2019 Datafile Atmosphere Clouds Cloud-base height Cloud fraction Backscatter profile Arctic Ocean 2018 AO2018 AO18 Meteorology Arctic boundary layer Arctic clouds High Arctic ACAS Earth science > Atmosphere John Prytherch 2019-07-22T13:50:51+00:00 English 1.0 None Data from the MISU Vaisala CL31 ceilometer, averaged over either 1 or 30-minute intervals. Two data formats are available: Matlab (.mat) and NetCDF (.nc), with an accompanying readme (.rtf) file. The height to the lowest cloud base, and up to two additional cloud bases when the lowest cloud layer does not cover the whole sky, was measured by a Vaisala CL31 ceilometer, located above Oden’s bridge on the 7th deck. The ceilometer was part of the Stockholm University ACAS project. The system uses a proprietary Sky Condition algorithm to determine cloud fraction at up to five levels, converting single-point time-series measurements to time-averaged area coverage. The system additionally recorded the backscatter profile, and hence serves as a so-called poor-man’s LiDAR. When the attenuation of the laser beam reaches a threshold, like in a dense fog, it switches to reporting vertical visibility, rather than cloud-base height. Data from the ceilometer are combined into a cruise-length file. The data are time-averaged to both 1-minute and 30-minute intervals, to correspond with the micrometeorological averaging periods used for the mast sensors. Coordinates (lat, lon) for the observations are not included in this dataset, but they are the same as in the <a href="">Weather data from MISU weather station during the Arctic Ocean 2018 expedition</a>.