PPAO_NH3_2022_2023_v2

# PPAO NH₃ dataset, 2022-2023 (v2) This dataset contains 6-hourly atmospheric NH₃ measurements from the Penlee Point Atmospheric Observatory (PPAO), southwest United Kingdom, during 2022-2023, together with corresponding seawater NH₃ and NHₓ concentrations, calculated NH₃ air-sea fluxes, air-mass trajectory classifications, and supporting meteorological and seawater parameters. The data are provided in CSV format together with the Python scripts used for the associated analysis and figure generation. Column descriptions and units are given below. ## Column descriptions **Date_time** - Timestamp of observation (UTC) **CH4_dry_ppm** - Dry atmospheric methane mixing ratio (ppm) **H2O_signal** - Atmospheric water-vapour signal. See associated manuscript methods for instrument measurement details. **atmospheric_pressure_mbar** - Atmospheric pressure (mbar) **relative_humidity** - Relative humidity (%) **air_temperature_degC** - Air temperature (°C) **windspeed_ms** - Measured wind speed (m s⁻¹) **wind_direction_deg** - Mean wind direction (°) **NH3_ppb** - Background-corrected atmospheric NH₃ mixing ratio (ppb) **NH3_raw_ppb** - Atmospheric NH₃ mixing ratio without zero-air background subtraction (ppb) **NHx_seawater_uM** - Seawater NHₓ concentration (NH₃ + NH₄⁺) (µM) **seawater_temperature_degC** - Seawater temperature (°C) **seawater_salinity** - Seawater salinity **seawater_pH** - Seawater pH (total scale) **U10_windspeed_ms** - Wind speed adjusted to 10 m height (m s⁻¹) **Fd_umol_m2_day** - NH₃ air-sea flux calculated using the background-corrected atmospheric NH₃ mixing ratio (µmol m⁻² day⁻¹). Positive values indicate sea-to-air emission and negative values indicate air-to-sea deposition. **Fd_raw_umol_m2_day** - NH₃ air-sea flux calculated using the atmospheric NH₃ mixing ratio without zero-air background subtraction (µmol m⁻² day⁻¹). Positive values indicate sea-to-air emission and negative values indicate air-to-sea deposition. **NH3_seawater_nmol_m3** - Dissolved seawater NH₃ concentration (nmol m⁻³) **cluster_number** - HYSPLIT air-mass trajectory cluster classification: 1) English Channel mixed (EC-M)2) North Atlantic South (NA-S)3) North Atlantic North (NA-N)4) United Kingdom mixed (UK-M)5) Continental Europe mixed (CE-M) # Missing data Missing values indicate periods for which measurements were unavailable or excluded following quality-control procedures, including instrument downtime, calibration periods, and experimental or instrument-testing periods.