Description Usage Arguments Details Author(s) References See Also Examples
Estimates the absorbed solar radiation and infrared radiation (W/m2) of an object using known physical relationships.
1 |
Ta |
Air temperature (degrees Celsius). Default value is 20. Used to estimate ground temperature if Tg is unavailable. |
Tg |
Ground temperature (degrees Celsius). Default value is NULL, but a measured Tg can be substituted or estimated with other functions. |
RH |
Relative humidity (fraction 0 to 1). Default value is 0.5. Used in call to Ld() to determine incoming radiation. |
E |
Emissivity (fraction 0 to 1) of the object absorbing longwave radiation. According to Kirschoff's law, emissivity = absorptivity. Absorptivity is multiplied by the average of the incoming longwave radiation to estimate absorbed radiation. |
rho |
Reflectivity (fraction 0 to 1) of the object absorbing solar radiation. Used to modify absorbed solar energy. Default is 0.1. |
cloud |
Fractional cloud cover (fraction from 0 to 1). Used in call to Ld() to determine incoming radiation. Default is 0. |
SE |
Solar energy (W/m2), usually measured. Default is 100. |
Total solar radiation must be supplied at this stage. The calculation here provides the worst case scenario since since no profile/angle metrics are yet taken into account. The animal could change orientation to/away from solar beam.
Glenn J Tattersall
Blaxter, 1986. Energy metabolism in animals and man. Cambridge University Press, Cambridge, UK, 340 pp.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 | ## The function is currently defined as
function (Ta = 25, Tg = NULL, RH = 0.5, E = 0.96, rho = 0.1,
cloud = 0, SE = 100)
{
if (length(SE) == 1)
SE <- rep(SE, length(Ta))
if (is.null(Tg))
Tg <- Tg(Ta, SE)
Ld <- Ld(Ta, RH = RH, n = cloud)
Lu <- Lu(Tg)
IR <- E * (Lu + Ld)/2
qabs <- (1 - rho) * SE + IR
qabs
}
# Example:
Ta<-25
Tg<-30
RH<-0.5
E<-0.96
rho<-0.1
cloud=0
SE<-100
qabs(Ta, Tg, RH, E, rho, cloud, SE)
# If Tg is unknown it can be set to NULL, and the qabs function will estimate Tg from
# an empirical relationship of Tg vs Ta and SE from the Tground() function
qabs(Ta, Tg=NULL, RH, E, rho, cloud, SE)
# For detailed examples and explanations, see:
# https://github.com/gtatters/Thermimage/blob/master/HeatTransferCalculations.md
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