Solar radiation simulations in the Iberian Peninsula: Accuracy and sensitivity to uncertainties in inputs of a radiative transfer model

- Uncertainty in inputs generates uncertainty in radiative transfer simulations.
- Radiative transfer simulations are in agreement with measurements.
- Differences between simulations and measurements are within uncertainties.

A radiative transfer model (RTM) is used to obtain total shortwave (SW) and erythemal (UVER) irradiances under cloudless conditions at nine Spanish locations on the Iberian Peninsula. For this purpose, various remote sensing retrievals such as ozone, aerosol optical depth, and water vapour are used as input in the RTM. The sensitivity of the simulated SW and UVER irradiances to the input uncertainties is studied repeating the same simulations but changing the inputs plus/minus their uncertainties. Sensitivity of global SW irradiance is usually below 10%, and sensitivity of global UVER irradiance is higher although it does not exceed 17%. SW and UVER irradiances are compared to measurements under cloudless conditions, with significant agreement emerging between modelled and measured, particularly for low solar zenith angles. Agreement is better for SW than for UVER. Differences between simulations and measurements are within uncertainties.