Overirradiance conditions and their impact on the spectral distribution at low- and mid-latitude sites

•Overirradiance in spectral irradiance measurements analyzed at different climates.•Average photon energy analysis of overirradiance, cloudy, and clear-sky spectra.•Overirradiances cause red-shift and clouds a blue-shift of the clear-sky spectrum.•Red-shift caused by overirradiance is proportional to the irradiance enhancement.•Spectral red-shift indicate a cloud-enhancement of the direct normal irradiance.