Source data for "Coupled NH3 and CO2 Fluxes over Guangzhou Reveal a Weakening of Vehicle-Exhaust Emissions"

This record contains the source data underlying the manuscript “Coupled NH3 and CO2 Fluxes over Guangzhou Reveal a Weakening of Vehicle-Exhaust Emissions”, including data used for Figures 1–3, Supplementary Figures S1–S3, and Supplementary Table S1. The primary observations were collected from the 118 m platform of Canton Tower in central Guangzhou, China (23.11°N, 113.32°E), between 2 November 2023 and 11 May 2024. The deposited Excel workbook contains quality-controlled half-hourly eddy-covariance fluxes of ammonia (NH3) and carbon dioxide (CO2), associated meteorological and footprint-model variables, figure-level plotting data, and supporting urban observations. The workbook includes: Quality-controlled 30 min NH3 and CO2 fluxes from Canton Tower, together with concentration, meteorological, turbulence, quality-control, mean-diurnal-variation gap-filling, and footprint-input variables. Source data for the campaign time series, mean diurnal cycles, NH3–CO2 flux relationships, source–sink quadrant analysis, and CO2-flux-binned NH3 response. A two-dimensional climatological flux-footprint grid, including the 70% and 90% cumulative-contribution regions and spatially allocated NH3 and CO2 fluxes. Hourly NH3 and NOx observations from the Gongyuanqian urban monitoring station for 2020–2025. No Gongyuanqian record is available for 2023; the manuscript’s multi-year comparison uses the May–November window. Quality-controlled 30 min CO2 flux data from the Hardau II urban tall tower in Zurich, reprocessed over the same period as the Canton Tower campaign for the cross-city comparison in Supplementary Table S1. Annual registered motor-vehicle and new-energy-vehicle stocks in Guangzhou for 2021–2025, together with reported fleet shares and official source links. Figure indices, data definitions, provenance information, quality-assurance records, and notes documenting manuscript–dataset consistency. Positive flux values denote upward transport or net emission, whereas negative values denote downward transport or net deposition. NH3 fluxes are reported in nmol m−2 s−1 and CO2 fluxes in µmol m−2 s−1. Blank cells indicate missing, invalid, or quality-controlled observations. Mean-diurnal-variation-filled values are explicitly identified and should not be interpreted as direct measurements. The deposited workbook contains processed half-hourly and hourly data and figure source data. The original 10 Hz high-frequency instrument data are not included. Reused and supporting datasets retain their original source information within the workbook and should be cited together with this Zenodo record.