Water evaporation as a key driver of summer ammonia flux in urban Beijing

The data were collected during a 73‑day field campaign from June to September 2022 at a 220‑m level on a 325‑m meteorological tower in urban Beijing, China. Measurements include half‑hourly fluxes of ammonia (NH₃), nitrous oxide (N₂O), and carbon dioxide (CO₂) obtained using the eddy covariance technique with a quantum cascade tunable infrared laser direct absorption spectrometer (QC‑TILDAS‑DUAL) and a three‑dimensional ultrasonic anemometer.

Supporting meteorological variables, including latent heat flux, sensible heat flux, friction velocity (u*), atmospheric stability, and boundary layer height, are also provided. All data are quality‑controlled, with flagging based on steady‑state and turbulence criteria, and gap‑filled where necessary. The data are provided in Microsoft Excel (.xlsx) format, organized by figure number for direct reproducibility.