Spatiotemporal representativeness of ERA5 atmospheric profiles across Cameroon’s climatic gradient and clear-sky radiative sensitivity to profile choice

Abstract Vertical atmospheric profiles underpin radiative-transfer modelling, satellite retrievals and climate diagnostics, yet the representativeness of averaged profiles warrants explicit testing across contrasting tropical African environments. We analysed ERA5-derived temperature, humid-air density, water-vapour and ozone concentrations at ten Cameroonian sites spanning coastal, humid-forest, highland, Guinean-savanna, Sudanian and Sudano-Sahelian environments during 2015–2020. Profiles sampled at 06, 09, 12, 15 and 18 UTC on five dates per month were compared across hours, sampled dates, months, seasons, years and sites. Terrain masking established a common 875–1 hPa domain. Temperature and water-vapour contrasts are strongest in the lower troposphere: at 875 hPa, mean site-specific monthly and interannual water-vapour amplitudes are 6.61 and 0.81 g m⁻³, respectively, while the six-year inter-site contrast reaches 5.72 g m⁻³. Corresponding temperature amplitudes are 5.13 and 0.58 K, with a 4.47 K inter-site contrast. Ozone shows substantial lower-tropospheric spatial variation, but its monthly amplitude reaches 45.96 µg m⁻³ at 50 hPa. Across 720 sampled monthly means, site, month and their interaction account for 29.69%, 38.05% and 26.73% of water-vapour variability at 875 hPa; the shared year effect contributes 0.52%. Clear-sky libRadtran simulations comparing coherent annual, driest-month and wettest-month profiles across 60 site–years yield a mean dry–humid contrast of 34.11 W m⁻² in downward solar flux and a mean humid–dry contrast of 26.28 W m⁻² in downward longwave flux at a virtual 875-hPa boundary. These findings motivate site- and month-specific profile sensitivity tests for clear-sky radiative applications.