Daily solar flux as a function of latitude and time

The top-of-atmosphere solar irradiance normal to the Earth’s surface varies as a function of latitude and longitude due to orbital effects throughout the year, with the most prominent being from variations in the Earth-axis tilt relative to the ecliptic and the Sun-Earth distance. Analytic formulae are derived to compute this net daily surface-normal solar flux as a function of Earth-axis tilt and latitude. Tabulated values are given for net daily flux at the top of the Earth’s atmosphere as a function of latitude and date throughout the year 2023 including corrections for Sun-Earth distance. Updates over older such tabulations, which often used an erroneously high value of the incident total solar irradiance, include applying the latest IAU-accepted lower solar-irradiance value, causing a ∼ 1 % decrease in computed values from some prominent prior publications.