Ceilometer backscatter, cloud base height and cloud fraction data from the Arctic Ocean 2016 expedition

John Prytherch, Michael Tjernström, Ian Brooks

Measurements of cloud base height, cloud fraction and backscatter profiles from the ceilometer operating on icebreaker Oden’s 7th deck during the Arctic Ocean 2016 expedition to the High Arctic.

Citation

John Prytherch, Michael Tjernström, Ian Brooks (2019) Ceilometer backscatter, cloud base height and cloud fraction data from the Arctic Ocean 2016 expedition. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-ao-2016-ceilometer-1

Data description

Data from the FMI Vaisala CL51 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.

Comments

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 CL51 ceilometer, located above Oden’s bridge on the 7th deck. The ceilometer, owned by the Finnish Meteorological Institute (FMI), was deployed as part of the Stockholm University weather station.

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 Weather data from MISU weather station during the Arctic Ocean 2016 expedition.

More information about the Canadian-Swedish Arctic Ocean 2016 expedition is available from the Swedish Polar Research Secretariat.