[HELP]
[help] time
The time are expressed in Julian year since J2000.0. J2000.0 corresponds to the Julian calendar date 2451545.0 or to the Gregorian calendar date of 2000 Jan 1 at 12h TT.
The julian year is an auxiliary unit of time defined as equal to 365.25 days.
[help] sampling step
The minimum step is 1 year. It is usually not necessary for this step to be smaller than 100 (yr). The step is expressed in julian year. The julian year is an auxiliary unit of time defined as equal to 365.25 days.
[help] mean daily insolation
The daily insolation is computed for a given latitude
of the Earth, and for a given position of the Earth
on its orbit. This position is sometime given by a
conventional date where the origine is at the moving
equinox with conventional date 21 march.
As this terminology is confusing, in the present
program, the position of the Earth on its orbit is
given either by its true longitude (1), or by the
mean longitude (2), both expressed in degrees
with origine at the moving equinox.
The true longitude is the true position angle of the
Sun-Earth direction with respect to the equinox.
The mean longitude is a fictif angle which is
described by the Earth at constant velocity.
The mean longitude is thus proportional to the time,
and should be the normal choice in many cases.
[help] monthly insolation
The monthly insolation correspond to the mean daily
insolation over 1/12 of a year, that is 30 degrees
of mean longitude, with origine at the equinox.
[help] mean annual insolation
The mean annual insolation is computed over a full
revolution of the Earth around the Sun.
[help] mean daily/ mean longitude
Approximate conventional dates for a given mean longitude
If you want: | Enter: |
21 March | 0 |
21 April | 30 |
21 May | 60 |
21 June | 90 |
21 July | 120 |
21 August | 150 |
21 September | 180 |
21 October | 210 |
21 November | 240 |
21 December | 270 |
21 January | 300 |
21 February | 330 |
You can enter all intermediate values
[help] latitude on the Earth
Positive latitudes are for the Northern Hemisphere
Negative latitudes are for the Southern Hemisphere
[help] mean monthly
Approximate conventional dates of the months
1: 21 December - 20 January
2: 21 January - 20 February
3: 21 February - 20 March
4: 21 March - 20 April
5: 21 April - 20 May
6: 21 May - 20 June
7: 21 June - 20 July
8: 21 July - 20 August
9: 21 August - 20 September
10: 21 September - 20 October
11: 21 October - 20 November
12: 21 November - 20 December