call diurnal_solar (lat, lon, time, cosz, fracday, rrsun, dt_time)

call diurnal_solar (lat, lon, gmt, time_since_ae, cosz, fracday, rrsun, dt)

The first option (used in conjunction with time_manager_mod) generates the real variables gmt and time_since_ae from the time_type input, and then calls diurnal_solar with these real inputs.

The time of day is set by

real, intent(in) :: gmt

The time of year is set by

real, intent(in) :: time_since_ae

with time_type input, both of these are extracted from

type(time_type), intent(in) :: time

Separate routines exist within this interface for scalar, 1D or 2D input and output fields:

real, intent(in), dimension(:,:) :: lat, lon
real, intent(in), dimension(:)   :: lat, lon
real, intent(in)                 :: lat, lon
real, intent(out), dimension(:,:) :: cosz, fracday
real, intent(out), dimension(:)   :: cosz, fracday
real, intent(out)                 :: cosz, fracday

One may also average the output fields over the time interval between gmt and gmt + dt by including the optional argument dt (or dt_time). dt is measured in radians and must be less than pi (1/2 day). This average is computed analytically, and should be exact except for the fact that changes in earth-sun distance over the time interval dt are ignored. In the context of a diurnal GCM, this option should always be employed to insure that the total flux at the top of the atmosphere is not modified by time truncation error.

real, intent(in), optional :: dt

type(time_type), optional :: dt_time

(see test.90 for examples of the use of these types)

Parameters

[in]	<lat>	Latitudes of model grid points [radians]
[in]	<lon>	Longitudes of model grid points [radians]
[in]	<gmt>	Time of day at longitude 0.0; midnight = 0.0, one day = 2 * pi [radians]
[in]	<time_since_ae>	Time of year; autumnal equinox = 0.0, one year = 2 * pi [radians]
[in]	<time>	Time at which astronomical values are desired (time_type variable) [seconds, days]
[out]	<cosz>	Cosine of solar zenith angle, set to zero when entire period is in darkness [dimensionless]
[out]	<fracday>	Daylight fraction of time interval [dimensionless]
[out]	<rrsun>	Earth-Sun distance (r) relative to semi-major axis of orbital ellipse (a):(a/r)**2 [dimensionless]
[in]	<dt>	OPTIONAL: Time interval after gmt over which the astronomical variables are to be averaged. this produces averaged output rather than instantaneous. [radians], (1 day = 2 * pi)
[in]	<dt_time>	OPTIONAL: Time interval after gmt over which the astronomical variables are to be averaged. this produces averaged output rather than instantaneous. time_type, [days, seconds]
[in]	<allow_negative_cosz>	Allow negative values for cosz?
[out]	<half_day_out>	half_day_out