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Accurate identification of clear-sky and cloudy periods from hyperspectral radiometric data is essential for atmospheric and remote sensing studies. Traditional approaches that rely on single-wavelength spectral ratios often fail under broken clouds due to rapid irradiance fluctuations and aerosol interference. This study introduces a new method based on the spectrally integrated diffuse-to-direct irradiance ratio (IDR), which is derived from modeled hyperspectral components and provides a robust indicator of sky conditions. The model is developed using 15-year hyperspectral measurements of solar downwelling irradiance (ES(λ), mW m-2 nm-1) and sky radiance (LS(λ), mW m-2 nm-1 sr-1) collected in a fixed coastal station located at the Marsdiep tidal inlet in the Dutch Wadden Sea.