| day2l {palinsol} | R Documentation |
Converts calendar day into true solar longitude and vice-versa
Description
Converts calendar day into true solar longitude for a given astronomical configuration and vice-versa
Usage
day2l(orbit, day)
l2day(orbit, l)
date_of_perihelion(orbit)
Arguments
orbit |
Output from a solution, such as |
day |
calendar day, in a 360-d year |
l |
true solar longitude, in radians |
Details
The 360-d calendar is a conventional calendar, for which day 80 is the day of NH spring equinoxe. The tropic year, which in reality is 365.24219876 * 86400 seconds was the practical reference to define the Gregorian Calendar since this is the time needed to go through all the seasons. More discussion of calendars and conversions in Berger et al. (2010) appendix D.
The day2l and l2day is based on algoritms given in Berger
(1978), but which can be traced back to expansions of the mean and true
anomaly by Brouwer and Clemente (1961), pp. 65 and 77 (see code for further
details).
Value
day of year (360-d cal.) or true solar longitude (in radians).
Functions
-
l2day(): Converts true solar longitude into calendar day -
date_of_perihelion(): Returns date of perihelion
Author(s)
Michel Crucifix, U. catholique de Louvain, Belgium.
References
Brouwer D. and G. M. Clemence, (1961), Methods of celestial mechanics, Academic Press, New York.
Berger, (1978) Long-term variations of daily insolation and Quaternary climatic changes, J. Atmos. Sci., 35, 2362-2367 1978, doi:10.1175/1520-0469(1978)035<2362:LTVODI>2.0.CO;2
Berger, A. Loutre, M.F. and Yin Q. (2010), Total irradiation during any time interval of the year using elliptic integrals, Quaternary Science Reviews, 29, 1968 - 1982, doi:10.1016/j.quascirev.2010.05.007
Examples
## date of perihelion throughout today
orbit=c(eps=0.409214, ecc=0.01672393, varpi=4.92251)
date_of_perihelion(orbit)
## date of winter solstice)
l2day(orbit, 270*pi/180.)