PET calculation: account for the elliptic nature of Earth's orbit #38
Labels
Milestone
Comments
dschlaep
referenced
this issue
Jul 3, 2020
Changes in inputs: - `climate.in`: remove `atmospheric transmissivity` because they were unused - `siteparam.in`: site latitude, slope, and aspect are now in consistent units (degrees) instead of a mix of radians and degrees - `siteparam.in`: orientation of aspect has changed: aspect = 0 indicates now a South facing slope instead of a North facing slope; values range -180 to +180 instead of 0-360 Changes in flow of calculations: - `petfunc()` that calculates PET takes now radiation as input argument instead of calculating it internally --> move calculation of radiation to the `SW_Flow` module Changes in the calculation of extraterrestrial radiation: - function renamed to `solar_radiation_extraterrestrial()` from `solar_radiation_TOA()` - accounts now for varying sun-earth distance with new function `sun_earth_distance_squaredinverse()` - improved `solar_declination()` to better match calendar year to solar year - extraterrestrial radiation is now calculated both for a horizontal and a tilted surface (defined by slope and aspect) --> future improvements: these calculations are repeated for each year, but values are the same per day of year -> these could be calculated only once and memoized Changes in the calculation of global horizontal radiation: - previous function `solar_radiation_surface()` replaced by new functions `clearsky_directbeam()`, `clearnessindex_diffuse()`, and `atmospheric_attenuation_cloudfactor()` - new approach implements a clear-sky model (additionally attenuated by a cloud factor) and a separation model to treat direct beam and diffuse radiation separately Changes in the calculation of tilted radiation: - previous function `_solar_radiation_sloped()` replaced, enhanced, and fixed by new function `sun_hourangles()` - new function `sun_hourangles()` calculates all possible sunrise and sunset hour angles for a horizontal and a tilted surface as well as the daily integral of the cosine of the solar incidence angle and the daily integral of the sine of the solar altitude angle based on equations developed by Allen et al. 2006 Agricultural and Forest Meteorology 139:55-73 - new approach implements an anisotropic transposition model to transpose direct beam and diffuse components of global radiation from a horizontal to a tilted surface One radiation function: - new function `solar_radiation()` calculates and returns horizontal and tilted extraterrestrial and global radiation terms
|
closed by 9f0f986 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
We don't account for the elliptic nature of Earth's orbit around the sun in the calculation of solar radiation variable
solradby functionpetfunc, e.g., see equation 3.1 from Seller 1965:where
mean(d)is the mean distance from the sun to Earth anddis the current distance.The text was updated successfully, but these errors were encountered: