solarforecastarbiter.validation.validator.detect_clearsky_ghi(ghi, ghi_clearsky)[source]

Identifies times when GHI is consistent with clear sky conditions.

Uses the function pvlib.clearsky.detect_clearsky. Assumes ghi data with regular (constant) time intervals which must be 15 minutes or less.

  • ghi (Series) – Global horizontal irradiance in W/m^2
  • ghi_clearsky (Series) – Global horizontal irradiance in W/m^2 under clear sky conditions

flags (Series) – True when clear sky conditions are indicated.


Clear-sky conditions are inferred when each of six criteria are met; see pvlib.clearsky.detect_clearsky for references and details. Threshold values for each criterion were originally developed for ten minute windows containing one-minute data [1]. As indicated in [2], the algorithm also works for longer windows and data at different intervals, if threshold criteria are roughly scaled to the window length. Here, the threshold values are based on [1] with the scaling indicated in [2].

Warns:RuntimeWarning – If pvlib.clearsky.detect_clearsky cannot be applied to the input.


[1] Reno, M.J. and C.W. Hansen, “Identification of periods of clear sky irradiance in time series of GHI measurements” Renewable Energy, v90, p. 520-531, 2016.

[2] B. H. Ellis, M. Deceglie and A. Jain, “Automatic Detection of Clear-Sky Periods From Irradiance Data,” in IEEE Journal of Photovoltaics, vol. 9, no. 4, pp. 998-1005, July 2019. doi: 10.1109/JPHOTOV.2019.2914444