Air Mass

This function empirically computes the non-pressure-corrected (sea level) and pressure-corrected (at altitude) air
masses as a function of the solar zenith angle.


AirMass Inputs




Algorithm (Bird & Hulstrom Version)

Compute the sea-level air mass:

AirMass Bird Hulstrom Algo2

Algorithm (Kasten / Sandia Version)

Compute the sea-level air mass:

AirMass Kasten Sandia Algo3

Algorithm (Common Pressure Correction and Filtering)

1.) Restrict the calculation of the air mass for zenith angles less than 89°

AirMass Pressure Correction Algo4
2.) Reduce the air mass function by the actual pressure (a function of elevation or an input given in the weather

AirMass Pressure Correction Algo5


Bird, R., Hulstrom, R., A Simplified Clear Sky Model for Direct and Diffuse Insolation on Horizontal Surfaces, 1981
NREL SERI/TP-642-761

Kasten, F. Discussions on the Relative Air Mass, Light Research Technology 25, 129.