Daily mean top-of-atmosphere insolation
For solar flux S perpendicular to the rays at the current orbital distance,latitudeφ and declinationδ give cosZ=sinφsinδ+cosφcosδcosh.
Key knowledge
For solar flux S perpendicular to the rays at the current orbital distance,latitudeφ and declinationδ give cosZ=sinφsinδ+cosφcosδcosh. Integrating positive illumination over a rotation gives meanQ=(S/π)[h₀sinφsinδ+cosφcosδsinh₀]. For ordinary sunrise/sunset h₀=arccos(−tanφtanδ); polar-day/night limits use h₀=π or0 with the appropriate geometry.
Values and equations
cosZ=sinφsinδ+cosφcosδcosh; meanQ=(S/π)[h₀sinφsinδ+cosφcosδsin h₀]
- Z,φ,δ,h,h₀
- solar zenith,latitude,declination,hour angle and daylight half-angle rad
- S
- solar flux normal to rays at the stated orbital distance W m⁻²
- meanQ
- daily mean horizontal top-of-atmosphere insolation W m⁻²
Conditions and scope
- Angles are radians; ideal spherical Earth and a point-like Sun,with declination and distance nearly constant over one rotation. Q is horizontal top-of-atmosphere energy flux,not surface flux after clouds/absorption.
- At poles or limiting geometries determine illumination directly rather than evaluating singular tan products. Finite solar disk,refraction,terrain and rapid orbital variations require refinements; this does not infer surface temperature by itself.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read actual latitude/declination/hour-angle zenith relation. Corrected the PDF's cost(lat) typographical form to cos(lat),verified independently as a unit-vector dot product. Daily mean is a disclosed integral of Smax(cosZ,0) over2π,not claimed printed on the sheet; excluded approximate calendar/declination fits and sunrise refraction conventions.
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Entry details
Permanent link to this entry ↗- Record identity
- uni-earth-daily-insolation-geometry
- Revision
- core.1
- Structured reference record
- University core expansion