Example of the hand-labelled clear-sky dataset. The plot displays 1 min time series of Global Horizontal Irradiance (GHI) and Diffuse Horizontal Irradiance (DHI) to visually illustrate the difference between clear periods (smooth GHI, low DHI) and cloudy conditions. The source dataset, from a fixed-tilt PV system in Golden, CO, USA [6], also provides the Direct Normal Irradiance (DNI) and Plane-of-Array (POA) irradiance used in this study. The clear-sky periods, highlighted in green, were manually labelled based on comparisons to a clear-sky model and stable temporal variability.