calc_ClearSky_QuantileRegression: Calculate fractional absorption of solar radiation by...

In laubblatt/cleaRskyQuantileRegression: Calculate monthly fractional clear-sky shortwave transmission from global radiation records

Description

The slope at a given quantile (here 0.85) is assumed to represent the fractional absorption of solar radiation under cloud-free conditions. This can be used to estimate the clear sky solar radiation of a period of one month when global radiation records are available. The observations should not be biased, since this directly effects the estimate. Persistent cloud-cover will reduce the estimate, but often results in poorer goodness of fit. The estimate is not useful for nighttime conditions. Details are described in Renner et al., 2019 ESS

Usage

calc_ClearSky_QuantileRegression(IncomingShortwave,
  IncomingShortwavePotential, tau = 0.85)

Arguments

IncomingShortwave	Vector of observed incoming total Shortwave radiation in units W m-2, also refferred to as global radiation or the sum of diffuse and direct radiation if available
IncomingShortwavePotential	Vector pf potential surface shortwave radiation at the surface without clouds.
tau	Numeric constant, quatile for which the regression is being performed. Defaults to 0.85 based on many BSRN stations, but this may vary (cloud type, frequency and aerosols).

Value

A data.table with columns tau, statistic and value. Key statistics are R1 (measure of goodness of fit), slope1 (linear slope assumed to represent the fractional absorption of solar radiation under cloud-free conditions), slope_sd (the standard deviation of the slope estimate), intercept (which should be close to 0, otherwise there is a problem in the correct timing of the observed and potential radiation), and n the sample size

Author(s)

Maik Renner, mrenner [at] bgc-jena.mpg.de

References

Renner, M., M. Wild, M. Schwarz, and A. Kleidon. "Estimating Shortwave Clear-Sky Fluxes from Hourly Global Radiation Records by Quantile Regression." Earth and Space Science, 2019. https://doi.org/10.1029/2019EA000686

See Also

[calc_PotRadiation_CosineResponsePower()] for calculating potential surface shortwave radiation as function of date, time and position

laubblatt/cleaRskyQuantileRegression documentation built on Nov. 27, 2019, 12:26 p.m.