González, CarmenVilaplana, Jose ManuelSerrano, Antonio2026-03-202026-03-202023-12-26Journal of Geophysical Research: Atmospheres 128(24): e2023JD0395002169-897Xhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JD039500https://hdl.handle.net/20.500.12666/1799The dataset used for the uncertainty evaluation of Brewer #150 is available at Zenodo (González et al., 2023a). The software (version 1.0) associated with this manuscript for the implementation of the Monte Carlo method is published on Zenodo (González et al., 2023b). Ozone data measured by Brewer #150 was used in the creation of this manuscript and can be downloaded from EuBrewNet (Rimmer et al., 2018). Aerosol optical depth measured at INTA/El Arenosillo station was used for the cosine correction and can be downloaded from AERONET (Dubovik & King, 2000; Holben et al., 1998).Precise spectral ultraviolet (UV) measurements are needed to ensure human protection as well as to support scientific research. Quantifying the uncertainty of the UV spectra recorded is crucial to evaluate the quality of the measurements which is needed, in turn, for the assessment of their reliability. However, for double-monochromator spectroradiometers, the analytical derivation of this uncertainty is a challenging task due to the difficulties involved in propagating individual uncertainties. Under these circumstances, a Monte Carlo simulation is a reliable alternative as it does not require the calculation of partial derivatives and considers both nonlinear effects and correlations in the data. In the present study, the uncertainty of the spectral UV irradiance measured by a Brewer MKIII spectrophotometer is evaluated using a Monte Carlo approach. This instrument belongs to the National Institute of Aerospace Technology and has successfully participated in several international campaigns, which ensures its precise calibration. The average expanded uncertainty (k = 2) of the global UV irradiance measured by this instrument varies between 10% at 300 nm and 7% at 363 nm. At shorter wavelengths, it increases sharply due to thermal and electronic noise as well as wavelength misalignment. The results indicate that a Brewer spectrophotometer is suitable for climatological studies and model validation. Nevertheless, a substantial reduction of these uncertainties might be required for accurately detecting long-term UV trends. Although the study focused on a Brewer spectrometer, the methodology used for the uncertainty analysis is general and can be adapted to most UV spectroradiometers.engAttribution 4.0 Internationalhttps://creativecommons.org/licenses/by/4.0/info:eu-repo/semantics/article10.1029/2023JD0395002169-8996http://dx.doi.org/10.13039/501100011033info:eu-repo/semantics/openAccess