Multi-year mole fraction and isotopic records for 5 UK sites

Description

CH4 mole fraction and δ13C data that have been measured by Royal Holloway, University of London (RHUL) from five locations around the UK. The samples were collected at Barra/Vatersay (BAR) in the Outer Hebrides, RHUL in Egham (EGH), Weybourne Atmospheric Observatory (WAO) - University of East Anglia, and the Western Channel Observatory (WCO) at two locations (E1 and L4) in the English Channel - Plymouth Marine Lab (PML). The Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME) was used to calculate the sensitivity of measurements, taken at EGH and WAO, to the surrounding emissions field. The raw NAME output files contain information about the locations of the modelled air particles at each time step. This information is processed to create hourly footprints in units of (mol/mol)(mol/m$^2$/s) for each latitude/longitude grid cell.

Steps to reproduce

The collection methods involved pumping ambient air into stainless steel flasks at Egham and into Tedlar or Flexfoil bags (SKC) at the other sites, these samples were collected approximately weekly and then sent to Royal Holloway, University of London for Analysis. CH4 mole fraction is analysed by a Picarro G1301 cavity ring-down analyser, to the WMO X2004A scale. Stable carbon isotope ratio measurements were carried out using CF-GC-IRMS (Continuous Flow Gas Chromatography-Isotope Ratio Mass Spectrometry), according to the method outlined in Fisher et al,. (2006). The reproducibility is 0.05 ‰ or better for most δ13C measurements. Note that for EGH, CH4 mole fractions were measured on a HP5890 GC-FID (gas chromatograph, flame ionisation detector) until 22nd March 2010, with the Picarro G1301 used thereafter. NAME III V7.2 was used with an output resolution of 0.23° latitude × 0.35° longitude. The whole study domain was (10.7 - 79.3)° N, (- 97.9 - 39.7) ° E. NAME was run with a UK Met Office Unified Model product for the UK, at a spatial resolution of 1.5 km and temporal resolution of 1 hour. The UK Met Office’s Global Unified Model (12-17 km horizontal resolution) was used to provide meteorology for the rest of the domain at a temporal resolution of 3 hours. The NAME transport model is available from the UK Met Office under licence by contacting https://enquiries@metoffice.gov.uk (Jones et al., 2007). The meteorological data used to drive the transport model from the UK Met Office operational numerical weather prediction (NWP) Unified Model (UM) are available from https://data.ceda.ac.uk/badc/ukmo-nwp (Met Office NAME Team, 2021).

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