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Global Attributes:	title: ATOMIC (Atlantic Tradewind Ocean Atmosphere Mesoscale Interaction Campaign) 2020 Field campaign: ceilometer 10min statistics from the NOAA Ship Ronald H. Brown by the National Oceanic and Atmospheric Administration (NOAA) in the tropical North Atlantic ocean summary: The temporal statistics in this file were computed from the 15-sec data that are output automatically by the Vaisala software. This covers different cloud conditions categorized by a cloud code : 0 = clear sky, 1 = one cloud layer detected, 2 = two cloud layers detected, 3 = three cloud layers detected,4 = totally obscured, 5 = partly obscured but determined transparent. Different percentile values were tested to determine how to most accurately characterize cloud base height from the lowest layer for this experiment. For this cruise the 5th percentile seemed to work best for cloud base height. All percentiles calculated are saved and explained in the comment global attribute. keywords: Earth Science > Atmosphere > Clouds > Cloud Properties > Cloud Base Height, Earth Science > Atmosphere > Clouds > Cloud Properties > Cloud Fraction, Earth Remote Sensing Instruments > Passive Remote Sensing > Photon/Optical Detectors > Ceilometers, In Situ Ocean-based Platforms > SHIPS keywords_vocabulary: GCMD Earth Science Keywords. Version 8.6 campaign: EUREC4A instrument: Lidar Ceilometer from NOAA PSL platform: RV Ronald H Brown project: ATOMIC 2020 sea_name: North Atlantic Ocean institution: NOAA Physical Sciences Laboratory (325 Broadway R/PSD, Boulder, CO 80305) naming_authority: gov.noaa.psl id: EUREC4A_ATOMIC_RonBrown_Ceilometer_10min_20200109-20200212_v1.1.nc time_coverage_start: 09-Jan-2020 00:00:00 time_coverage_end: 12-Feb-2020 23:50:00 time_coverage_duration: PT10.M publisher_type: person publisher_institution: NOAA publisher_name: Ludovic Bariteau publisher_email: ludovic.bariteau@noaa.gov contributor_name: Chris Fairall, Elizabeth Thompson, Sergio Pezoa, Ludovic Bariteau product_version: v1.1 history: v1.0: original data, v1.1: added more cloud1 percentile levels and edited comments date_created: 2021-02-18T06:11:10Z date_modified: 2021-02-18T06:11:10Z standard_name_vocabulary: CF Standard Name Table v41 ncei_template_version: NCEI_NetCDF_Trajectory_Template_v2.0 Conventions: CF-1.6, ACDD-1.3 comment: The ceilometer produced vertical profiles of backscatter intensity produced by refractive index gradients, such as differences between dry air above the trade wind inversion vs. the atmospheric boundary layer air that is laden with aerosol, sea spray, and water vapor. The principal use of the ceilometer is to track the strong backscatter returns associated with cloud base height. The base level was computed as the 5th percentile value of the heights detected from the first visible cloud level (cloud_code detections of cloud1 at 15-sec resolution) in a given hour or 10-min time period. The percentiles of cloud1 heights that were computed, tested, and saved in this file are: prcnt_cld_5, _10, _16, _50, _84. Comparing these heights can potentially yield some information on how sheared or how vertically-developed the non-raining lowest cloud layer was. However, these values are not all indicative of cloud base. The higher percentiles of cloud1 heights are mostly indicative of sheared lateral edges of clouds and detached tops of clouds whose bases have evaporated and dissipated. The signal is completely attenuated by rainfall, which was rare but did occur in this experiment. In the absence of rain, strong backscatter returns are produced by the cloud base, then the signal is rapidly attenuated above that level. The ceilometer data should never be used to determine cloud top height. The ceilometer will also detect a strong scattering return from the horizontally-sheared lateral edges of clouds overhead of the ship. For example, during situations when the cloud top becomes sheared laterally away from the location of the cloud base, the ceilometer return at that time will be higher than the actual cloud base. These times should be flagged and interpreted differently. Actual cloud base changes very slowly in these data. Detrained leftover upper-level cloud debris from mature dissipating clouds can also produce a detectable signal from the ceilometer within a km or so above the cloud base, such that the original cloud base has already evaporated. In these cases where the cloud base appears to change relatively rapidly, the lowest altitude signals from the ceilometer should be interpreted as cloud base. The ceilometer also detected middle-layer clouds in the atmosphere near 4-6 km that are separate from the low-level cumulus cloud field. A more thorough check of ceilometer statistics of cloud base and cloud fraction should be conducted between ceilometer, lidar, and LCL height calculated from mixed layer air parcels (not surface parcels). The ceilometer collected data successfully at all times except for a 9-hour outage between 03:30 UTC Jan 30 to 00:30 UTC Jan 31. This issue appears to be due to incorrect or faulty file paths. We only have an image of the data collected during that time. Contact Elizabeth for the image if needed.

Variables:	time: Array of 64 bit Reals [time = 0..5039] time: standard_name: time units: seconds since 2020-01-01 00:00:00UTC axis: T calendar: standard comment: Time mark the start point of each duration interval. coverage_content_type: coordinate _FillValue: -9999.0
	lat: Array of 64 bit Reals [time = 0..5039] time: standard_name: latitude units: degree_north axis: Y actual_range: 12.791101, 15.864921 valid_range: -90.0, 90.0 coverage_content_type: coordinate instrument: Ship GPS _FillValue: -9999.0
	lon: Array of 64 bit Reals [time = 0..5039] time: standard_name: longitude units: degree_east axis: X actual_range: -59.65249, -50.926708 valid_range: -180.0, 180.0 coverage_content_type: coordinate instrument: Ship GPS _FillValue: -9999.0
	RonBrown: String RonBrown long_name: NOAA Ship Ronald H. Brown ncei_code: 096U call_sign: WTEC imo_code: 9105786 DODS: strlen: 5040 dimName: time
	crs: 64 bit Real crs grid_mapping_name: latitude_longitude epsg_code: EPSG:4326
	Ceilometer_instrument: String Ceilometer_instrument long_name: Vaisala CL31 single-wavelength backscatter lidar (ceilometer) ncei_name: Ceilometer make_model: Vaisala CL31 serial_number: E2310001 DODS: strlen: 5040 dimName: time
	cloud_base: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud base height standard_name: cloud_base_altitude units: km coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 7.0 actual_range: 0.28, 6.86975 _FillValue: -9999.0 comment: Computed as the 5th percentile of cloud1, the height of first cloud layer detected, from 15 sec raw data over this time period.
	frac_cloud: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud fraction standard_name: cloud_area_fraction_in_atmosphere_layer units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 1.0 actual_range: 0.0, 1.0 _FillValue: -9999.0 comment: cloud fraction of time period when cloud was detected in 15 sec data cloud_code, including codes 1-5 ranging from lower to upper level clouds and obscured clouds. The layer here ranges from surface to 7km
	frac_clear: Array of 64 bit Reals [time = 0..5039] time: long_name: clear sky fraction units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 1.0 actual_range: 0.0, 1.0 _FillValue: -9999.0 comment: fraction of time period when clear sky was detected in 15 sec data cloud_code, including code 0
	count_total: Array of 32 bit Integers [time = 0..5039] time: long_name: count of total cloud detections units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 100.0 actual_range: 0.0, 41.0 _FillValue: -9999 comment: count of any cloud classifications in this time period from 15 sec cloud_code data, either codes 1-5 ranging from lower to upper level clouds and obscured clouds
	count_layers_1_to_3: Array of 32 bit Integers [time = 0..5039] time: long_name: count of cloud detections in layers 1 to 3 units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 100.0 actual_range: 0.0, 41.0 _FillValue: -9999 comment: count of any cloud classifications from codes 1, 2, 3 for first, second, and third cloud layers detected in this time period from 15 sec cloud_code data
	count_cloud_obscured: Array of 32 bit Integers [time = 0..5039] time: long_name: count of obscured cloud detections units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 100.0 actual_range: 0.0, 40.0 _FillValue: -9999 comment: count of obscured cloud classifications in this time period from 15 sec cloud_code data, from code 4
	count_part_obscured_transparent: Array of 32 bit Integers [time = 0..5039] time: long_name: count of partly obscured cloud detections units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 100.0 actual_range: 0.0, 0.0 _FillValue: -9999 comment: count of partly obscured and transparent cloud classifications in this time period from 15 sec cloud_code data, from code 5
	count_clear: Array of 32 bit Integers [time = 0..5039] time: long_name: count of clear detections units: 1 coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 100.0 actual_range: 0.0, 41.0 _FillValue: -9999 comment: count of clear sky cloud classifications in this time period from 15 sec cloud_code data, from code 0
	prcnt_cld_5: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud base height from 5th percentile standard_name: cloud_base_altitude units: km coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 10.0 actual_range: 0.28, 6.86975 _FillValue: -9999.0 comment: This is the same as cloud_base height for this dataset since appeared to be the most consistent threshold. This is the 5th percentile of cloud1, the height of first cloud layer detected, from 15 sec raw data over this time period.
	prcnt_cld_10: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud base height from 10th percentile standard_name: cloud_base_altitude units: km coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 10.0 actual_range: 0.305, 6.992 _FillValue: -9999.0 comment: This is the 10th percentile of cloud1, the height of first cloud layer detected, from 15 sec raw data over this time period.
	prcnt_cld_16: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud base height from 16th percentile standard_name: cloud_base_altitude units: km coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 10.0 actual_range: 0.32520000000000004, 7.0237 _FillValue: -9999.0 comment: This is the 16th percentile of cloud1, the height of first cloud layer detected, from 15 sec raw data over this time period. Therefore this is one standard deviation below the median.
	prcnt_cld_50: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud base height from 16th percentile standard_name: cloud_base_altitude units: km coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 10.0 actual_range: 0.39, 7.375 _FillValue: -9999.0 comment: This is the 50th percentile or median of cloud1, the height of first cloud layer detected, from 15 sec raw data over this time period.
	prcnt_cld_84: Array of 64 bit Reals [time = 0..5039] time: long_name: cloud base height from 16th percentile standard_name: cloud_base_altitude units: km coverage_content_type: thematicClassification instrument: ceilometer_instrument platform: RonBrown grid_mapping: crs coordinates: time lat lon cell_methods: time: point longitude: point latitude: point valid_range: 0.0, 10.0 actual_range: 0.39, 7.62 _FillValue: -9999.0 comment: This is the 84th percentile of cloud1, the height of first cloud layer detected, from 15 sec raw data over this time period. Therefore this is one standard deviation above the median.

For questions or comments about this dataset, contact the administrator of this server [PSL Data Group] at: psl.data@noaa.gov

For questions or comments about the OPeNDAP service bundled with the TDS, email THREDDS support at: support-thredds@unidata.ucar.edu

DDS:

Dataset {
    Float64 time[time = 5040];
    Float64 lat[time = 5040];
    Float64 lon[time = 5040];
    String RonBrown;
    Float64 crs;
    String Ceilometer_instrument;
    Float64 cloud_base[time = 5040];
    Float64 frac_cloud[time = 5040];
    Float64 frac_clear[time = 5040];
    Int32 count_total[time = 5040];
    Int32 count_layers_1_to_3[time = 5040];
    Int32 count_cloud_obscured[time = 5040];
    Int32 count_part_obscured_transparent[time = 5040];
    Int32 count_clear[time = 5040];
    Float64 prcnt_cld_5[time = 5040];
    Float64 prcnt_cld_10[time = 5040];
    Float64 prcnt_cld_16[time = 5040];
    Float64 prcnt_cld_50[time = 5040];
    Float64 prcnt_cld_84[time = 5040];
} Datasets/ATOMIC/data/rhb/ceilometer/EUREC4A_ATOMIC_RonBrown_Ceilometer_10min_20200109-20200212_v1.1.nc;

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