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EUREC4A_BCO_LGR_1min_1.0.nc

netcdf EUREC4A_BCO_LGR_1min_1.0 {
dimensions:
        level = 1 ;
        time = UNLIMITED ; // (0 currently)
variables:
      	double time(time) ;
                time:units = "seconds since 2020-01-01 00:00:00 UTC" ;
        double ppmv_H2O(time) ;
                ppmv_H2O:long_name = "H2O Concentration" ;
                ppmv_H2O:units = "ppmv" ;           
        double q_H2O(time) ;
                q_H2O:long_name = "Specific Humidity" ;
                q_H2O:units = "kg/kg" ;
        double d18O(time) ;
                d18O:long_name = "Oxygen 18/16 isotope delta value" ;
                d18O:units = "delta_per_mil" ;
        double dD(time) ;
                dD:long_name = "D/H isotope delta value" ;
                dD:units = "delta_per_mil" ;
 
// global attributes:
								:Title = "EUREC4A_BCO_LGR_1min_1.0"	;                
                :Author = "Sebastian Los <slos@unm.edu" ;
                :PI = "Dr. Joseph Galewsky <galewsky@unm.edu"	;
                :Description = "Continuous water vapor isotopic time series. Delta values per mil on VSMOW-SLAP scale. Bulk uncertainties: d18O = 0.41, dD = 0.94." ;
                :Experiment = "EUREC4A Field Campaign" ;
                :Location = "Barbado Cloud Observatory, Deebles Point (13.16°N, 59.43°W), 17 m a.s.l." ;
                :Instrument = "Los Gatos off-axis integrated cavity output spectroscopy (OA-ICOS) isotopic analyzer" ;                
                :Collected = "Jan 18 - Feb 16, 2020" ;
                :Created = "Feb 15, 2021"	;
                :Updated = "Oct 11, 2021"	;               
                :History = "Version 1.0, moving IAEA calibration"	;                
                :Version = "1" ;
}

During the EUREC4A campaign, a Los Gatos Research (LGR) analyzer, using off-axis integrated cavity output spectroscopy (OA-ICOS) was operated at the Barbados Cloud Observatory (13.16°N, 59.43°W) from 18 January to 16 February 2020. The instrument was installed alongside a Picarro Water Vapor Isotopic Analyzer in a temperature-regulated container (24±2°C). Both analyzers sampled ambient air from the same protected inlet and heated inlet line. Water vapor isotope data from the LGR were normalized to the VSMOW-SLAP scale using three liquid standards; two were measured once, while a third was introduced during daily checks. The daily standard was interpolated to the raw 1 Hz time resolution and the IAEA procedure (IAEA, 2017) was used to calibrate and account for instrument drift. Only the stablest parts of each calibration check (10-to-30 minutes in length) were selected for normalization. No humidity-dependence correction was applied to the data. Uncertainty estimates are ±0.41‰ and ±0.94‰ for δ18O and δD respectively. An additional source of uncertainty for the OA-ICOS analyzer are large oscillations in δ18O —on the order of 1-1.5 ‰ permil— that were observed during some periods of ambient sampling. While the cause of these oscillations has yet to be identified, the fact that they appear only in one isotope ratio and not the other suggests an intermittent problem with the internal spectroscopy. This effect is not included in the uncertainty estimate mentioned above. Masked (missing) data in either BCO water vapor isotopic dataset represent periods when daily calibration checks or instrument maintenance were performed. All variables have been averaged in 1-minute intervals. IAEA – International Atomic Energy Agency (2017). Reference sheet for VSMOW2 and SLAP2 international measurement standards, IAEA, Vienna, 8 pp.