cli_clgen – SWAT+

subroutine cli_clgen(iwgn)

Uses

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~ ~ ~ PURPOSE ~ ~ ~
this subroutine calculates the daylength, distribution of 
radiation throughout the day and maximum radiation for day

~ ~ ~ INCOMING VARIABLES ~ ~ ~
name        |units         |definition
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 
j           |none          |HRU number
latcos(:)   |none          |Cos(Latitude) for HRU
latsin(:)   |none          |Sin(Latitude) for HRU
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ OUTGOING VARIABLES ~ ~ ~
name        |units         |definition
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
frad(:,:)   |none          |fraction of solar radiation occuring during 
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ LOCAL DEFINITIONS ~ ~ ~
name        |units         |definition
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
sdlat       |none          |(-Tan(sd)*Tan(lat))
cosrho(:)   |none          |Cos(zenith angle for hour)
dd          |none          |relative distance of the earth from the sun
h           |none          |Acos(-Tan(sd)*Tan(lat))
ii          |none          |counter
sd          |radians       |solar declination: latitude at which the sun
                           |is directly overhead at noon
totrho      |none          |sum of cosrho values for all hours of day
yc          |none          |Cos(sd)*Cos(lat)
ys          |none          |Sin(sd)*Sin(lat)
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~


~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~
Intrinsic: Sin, Tan, Acos, Cos, Real
~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~

Calculate Daylength calculate solar declination: equation 2.1.2 in SWAT manual 365/2pi = 58.09

calculate the relative distance of the earth from the sun the eccentricity of the orbit daylength = 2 * Acos(-Tan(sd) * Tan(lat)) / omega where the angular velocity of the earth"s rotation, omega, is equal to 15 deg/hr or 0.2618 rad/hr and 2/0.2618 = 7.6374

sdlat will be >= 1. if latitude exceeds +/- 66.5 deg in winter latitude exceeds +/- 66.5 deg in summer Calculate Potential (maximum) Radiation !! equation 2.2.7 in SWAT manual Calculate fraction of radiation recieved during each hour in day this calculation assumes solar noon (when the angle between the observer on the earth to the sun and a line normal to the earth"s at that position is at a minimum) falls at 12 noon in day. equation 2.2.10 in SWAT manual

angular velocity times hour away from solar noon. To calculate radiation for an hour, the hour angle for the midpoint of the time period is used. time = 0. at solar noon with positive values in the morning and negative in the evening 0.2618 rad/hr

Arguments

Type	Intent	Optional	Attributes		Name
integer				::	iwgn

cli_clgen Subroutine

Contents

subroutine cli_clgen(iwgn)

Uses

Arguments