http://bolin.su.se/data/oden-artofmelt-2023-ceilometer-1 Sonja Murto, Michael Tjernström, Michail Karalis, John Prytherch Bolin Centre Database 2024 Datafile Atmosphere Weather observations Clouds Cloud base height Cloud fraction Lidar backscatter Backscatter profiles Arctic Arctic Ocean Meteorology Atmosphere Weather observations ARTofMELT ARTofMELT 2023 expedition Icebreaker Oden Earth science > Atmosphere Sonja Murto 2024-06-23T17:31:34+00:00 English 1 The dataset includes four NetCDF (`.nc`) files zipped into one zip-file. Total file size is about 519 MB (compressed 257 MB). A list of all variable names, with short explanations and units is provided below. There is also an associated [`Readme_CL.txt`](data/oden-artofmelt-2023-ceilometer-1/Readme_CL.txt) file that provides code definitions and further details of data and processing. ##### Variables{#expandable} Primary variables are cloud base heights and sky condition data, where a clustering algorithm has been applied to separate multiple cloud layers over a 10-minute time period and also provides cloud fractions for multiple layers. - [Primary variables](#Primary-variables){.collapsed} - `day_of_year` Decimal day of year (in UTC) [time] - `year` Year - constant [time] - `month` Month of the year [time] - `day` Day of the month [time] - `hour` Hour of the day (in UTC) [time] - `minute` Minutes of the hour [time] - `second` Seconds of the minute [time] - `flag_cloudcode` Housekeeping (-1 = missing data; 0 = no significant backscatter; 1-3 = number of cloud bases detected; 4 = full obscuration but no cloud base detected) [time] - `vertical_visibility` Vertical visibility (m) (when flag_cloudcode = 4, true for 30s original data) [time] - `highest_detected_signal` Highest signal detected (m) (NaN except for flag_cloudcode = 4; true for 30s original data) [time] - `cloud_base_altitude` The height to the cloud base of maximum three layers (NaN when a layer is not detected, either because it is obscured or because there is only lower layers) [time/cloud_layer] - `backscatter_profile` backscatter coefficient profile (1/(km*steradians)) [time/range_levels] - [Derived variables](#Derived-variables){.collapsed} - `sky_condition_cloud_fraction` Cloud fraction(s) in octas for up to five cloud layers as identified by a proprietary cluster algorithm (NaN when a layer is not detected/missing data and 9 when the lidar is obscured (first level only)). [time/sky_condition_layer] - `sky_condition_cloud_altitude` The height to the cloud base of maximum five layers identified identified by a proprietary cluster algorithm including instrument height (m). (NaN when a layer is not detected/mising data or reported as vertical visibility (lowest layer only) when corresponding sky_condition_cloud_fraction = 9 ) [time/sky_condition_layer] ##### Dimensions Dimensions for the fields are time, some variables have a second dimension. The four NetCDF files have the following different time resolutions: - native 30 s time resolution - 1 minute time averaged data - 10 minute time averaged data - 20 minute time averaged data The data was concatenated from the native format and averaged when necessary. ##### Measurement system The data was obtained from a lidar ceilometer from Vaisala (Vaisala CL31). Clouds are detected by thresholds on backscatter radiation from an eye-safe lidar. When the lowest cloud layer is not covering the sky, multiple cloud layers can be detected. The instrument also provides a cloud scene product based on the last 10 minutes of data using a proprietary clustering algorithm that in addition to cloud base height also provide a cloud fraction for each layer. The original backscatter profile is also provided. ##### Quality control No data quality control is applied, except for adding the instrument height to the cloud base height variables. ##### Associated raw data and code The raw data, from which this dataset is derived, was created by [Murto et al. (2024)](https://doi.org/10.17043/oden-artofmelt-2023-ceilometer-raw-1) and is available separately. The current dataset is the concatenation of the original raw files on the native time scale and also averaged into 1 min, 10 min and 20 min averaging periods to accommodate the user. The computer codes, in Matlab and Python, written by [Murto and Prytherch (2024)](https://git.bolin.su.se/bolin/oden-artofmelt-2023-ceilometer), used to derive this dataset in NetCDF format from the raw data files are also available. ##### Data creators' roles The instrument system was continuously logging and was monitored by the Stockholm University Meteorology team onboard Oden: - Sonja Murto (operator and dataset creator) - Michail Karalis (operator) - Michael Tjernström (chief scientist; operator) John Prytherch (also Stockholm University) is responsible for the instrument system. ##### The expedition Data were collected during the ARTofMELT 2023 expedition on board the Swedish icebreaker Oden, which was organized by the [Swedish Polar Research Secretariat](https://www.polar.se/en/expeditions/previous-expeditions/arctic/artofmelt-2023/) from 8 May through 14 June, 2023.