pvlib.atmosphere.get_relative_airmass

pvlib.atmosphere.get_relative_airmass(zenith, model='kastenyoung1989')

Calculate relative (not pressure-adjusted) airmass at sea level.

Parameter model allows selection of different airmass models.

Parameters:

• zenith (numeric) – Zenith angle of the sun. [degrees]

• model (string, default 'kastenyoung1989') –

  Available models include the following:

  • ’simple’ - secant(apparent zenith angle) - Note that this gives -Inf at zenith=90

  • ’kasten1966’ - See [1] - requires apparent sun zenith

  • ’youngirvine1967’ - See [2] - requires true sun zenith

  • ’kastenyoung1989’ (default) - See [3] - requires apparent sun zenith

  • ’gueymard1993’ - See [4], [5] - requires apparent sun zenith

  • ’young1994’ - See [6] - requires true sun zenith

  • ’pickering2002’ - See [7] - requires apparent sun zenith

  • ’gueymard2003’ - See [8], [9] - requires apparent sun zenith

Returns:

airmass_relative (numeric) – Relative airmass at sea level. Returns NaN values for any zenith angle greater than 90 degrees. [unitless]

Notes

Some models use apparent (refraction-adjusted) zenith angle while other models use true (not refraction-adjusted) zenith angle. Apparent zenith angles should be calculated at sea level.

Comparison among several models is reported in [10].

References

[1]

Fritz Kasten, “A New Table and Approximation Formula for the Relative Optical Air Mass,” CRREL (U.S. Army), Hanover, NH, USA, Technical Report 136, 1965. DOI: 11681/5671

[2]

A. T. Young and W. M. Irvine, “Multicolor Photoelectric Photometry of the Brighter Planets. I. Program and Procedure,” The Astronomical Journal, vol. 72, pp. 945-950, 1967. DOI: 10.1086/110366

[3]

Fritz Kasten and Andrew Young, “Revised optical air mass tables and approximation formula,” Applied Optics 28:4735-4738, 1989. DOI: 10.1364/AO.28.004735

[4]

C. Gueymard, “Critical analysis and performance assessment of clear sky solar irradiance models using theoretical and measured data,” Solar Energy, vol. 51, pp. 121-138, 1993. DOI: 10.1016/0038-092X(93)90074-X

[5]

C. Gueymard, “Development and performance assessment of a clear sky spectral radiation model,” in Proc. of the 22nd ASES Conference, Solar ’93, 1993, pp. 433–438.

[6]

A. T. Young, “Air-Mass and Refraction,” Applied Optics, vol. 33, pp. 1108-1110, Feb. 1994. DOI: 10.1364/AO.33.001108

[7]

Keith A. Pickering, “The Southern Limits of the Ancient Star Catalog and the Commentary of Hipparchos,” DIO, vol. 12, pp. 3-27, Sept. 2002. Available at DIO

[8]

C. Gueymard, “Direct solar transmittance and irradiance predictions with broadband models. Part I: detailed theoretical performance assessment”. Solar Energy, vol 74, pp. 355-379, 2003. DOI: 10.1016/S0038-092X(03)00195-6

[9]

C. Gueymard, “Clear-Sky Radiation Models and Aerosol Effects”, in Solar Resources Mapping: Fundamentals and Applications, Polo, J., Martín-Pomares, L., Sanfilippo, A. (Eds), Cham, CH: Springer, 2019, pp. 137-182. DOI: 10.1007/978-3-319-97484-2_5

[10]

Matthew J. Reno, Clifford W. Hansen and Joshua S. Stein, “Global Horizontal Irradiance Clear Sky Models: Implementation and Analysis” Sandia National Laboratories, Albuquerque, NM, USA, SAND2012-2389, 2012. DOI: 10.2172/1039404

Examples using pvlib.atmosphere.get_relative_airmass

Modelling shading losses in modules with bypass diodes

Modelling shading losses in modules with bypass diodes

Modeling Spectral Irradiance

Modeling Spectral Irradiance

Spectral Mismatch Estimation

Spectral Mismatch Estimation

Average Photon Energy Calculation

Average Photon Energy Calculation