Table 1
Glossary of key impactful features.
| Category | Description | Abbr. |
|---|---|---|
| Base Irradiance Measurements | Direct Normal Irradiance: The solar radiation received by a surface held perpendicular (normal) to the sun’s rays. | DNI |
| Global Horizontal Irradiance: The total solar radiation received on a horizontal surface. | GHI | |
| Diffuse Horizontal Irradiance: The solar radiation received on a horizontal surface that has been scattered by the atmosphere. | DHI | |
| Temporal Stability & Change | Rolling standard deviation, measuring irradiance stability, for: | |
| - Direct Normal Irradiance (DNI) | Sdhi | |
| - Global Horizontal Irradiance (GHI) | Sghi | |
| - Diffuse Horizontal Irradiance (DHI) | Sdhi | |
| Coefficient of Variation: The normalized stability of GHI over a 30 min window. | CVghi,30 | |
| Clearness & Ratio Indices | Ratio of Direct Normal to Diffuse Horizontal Irradiance (DNI/DHI). | Rd |
| Clearness Index: Ratio of measured GHI to theoretical clear-sky GHI. | kt | |
| Beam Clearness Index: Ratio of measured DNI to theoretical clear-sky DNI. | kb | |
| Clear-sky Score: A composite score combining clearness indices (kt, kb) and their stability to indicate clear-sky likelihood. | Scs | |
| Diffuse Fraction Deviation: Deviation of the diffuse fraction from its zenith-specific median. | Δkd,z | |
| Ratio Match Score: Match between the measured and theoretical direct-to-diffuse ratio. |  |
|
| Solar Geometry & Temporal | Azimuth: The compass direction of the sun. | Az |
| Zenith Angle: The angle of the sun relative to the point directly overhead (the zenith). | θz | |
| Month: The month of the year, used to capture seasonal patterns. | Mo | |
| Cyclical encoding of time, representing the annual/daily pattern: | ||
| - Sine of the day of the year | dsin | |
| - Cosine of the hour of the day | hcos |
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