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The simple atmosphericCeiling*sin(elevation) model overestimates clear-sky radiation at low sun angles because it ignores the longer atmospheric path light travels near the horizon. At 5° elevation the path is ~11x vertical, making the real clear-sky ceiling ~26 W/m² rather than the 83 W/m² the naive model predicts — causing sunny low-angle readings to be misclassified as mostly cloudy. Replace with the Beer-Lambert correction: expectedClearSky = 950 * exp(-opticalDepth / sin(elevation)) * sin(elevation) opticalDepth=0.1 (clear atmosphere) produces accurate values across all angles: ~26 W/m² at 5°, ~93 W/m² at 10°, ~715 W/m² at solar noon. |
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| condition.go | ||
| weather.go | ||