Examination of Relationship Between Direct Solar Irradiance and Measured Surface Air Temperature

This study examines the relationship between the post-processed Spectral Solar Irradiance (SSI) data and the radiative population of Surface Air Temperature (SAT) from multiple Canadian records spanning over ~70 years. ‘Radiative days’ refer to days during which the diurnal temperature cycle conforms well with the quasi-sinusoidal pattern [1,2] of typical daily air temperature variability. A set of sensitivity cases testing different extinction cross-sections, covering integrated incoming irradiance at the surface in 16 wavelength bins is developed in an attempt to provide quantitative substantiation to the conjecture that the observed SAT increase is caused by the changes in the Earth’s atmosphere. The SSI data are acquired from the Naval Research Laboratory Spectral Solar Irradiance version 2.1 NRLSSIv2.1 model while Earth’s orbital data utilized for calculation of the orbital effects on SSI are obtained from Jet Propulsion Laboratory (JPL) numerically integrated Dynamical Ephemerides DE431 [4]. A simple model of atmospheric transmittance was developed to calculate SSI on the earth’s surface. The model includes a spherically stratified atmosphere with explicit accounting for density and refraction index variability with altitude to accurately determine the optical path and mass allowing the modeling of atmospheric constituents. By varying the extinction cross section and other elements of the transmittance model we endeavor to infer the evolution of atmospheric greenhouse gases in past 70 years. This study suggests that daily rates of increase in SAT and SSI (from sunrise to early afternoon) are strongly correlated and that the correlation coefficients between SAT and SSI evolve due to climate change while SSI remains relatively constant. These effects are particularly noticeable within the population of radiative days when daily temperature increases are generally driven by insolation, and specifically by the short wavelength incoming irradiance.

References:

[1] Žaknić-Ćatović, A., Gough, WA., “Identification of Radiative and Advective Populations in Canadian Temperature Time Series Using the Linear Pattern Discrimination Algorithm”, 2021., International Journal of Climatology, 41:5100-5124.

[2] Žaknić-Ćatović, A., Gough, WA., “Seasonal Aspects of Radiative and Advective Air Temperature Populations: A Canadian Perspective”, 2022., 13(7):1017.

[3] Coddington O., Lean J., Lindholm, D., Pilewskie, P., Snow, M., “Spectral Irradiance Solar Data”, NOAA CDR Program 2015.

[4] Folkner, W.M., Williams, J.G., Boggs, D.H., Park, R.S., Kuchynka, P., “The Planetary and Lunar EphemeridesDE430 and DE431”, IPN Progress Report 42-196, Jet Propulsion Laboratory