qabs {Thermimage}

Estimates the absorbed solar and infrared radiation (W/m2)

Description

Estimates the absorbed solar radiation and infrared radiation (W/m2) of an object using known physical relationships.

Usage

qabs(Ta = 20, Tg = NULL, RH = 0.5, E = 0.96, rho = 0.1, cloud = 0, SE = 100)

Arguments

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.

Details

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.

Author(s)

Glenn J Tattersall

References

Blaxter, 1986. Energy metabolism in animals and man. Cambridge University Press, Cambridge, UK, 340 pp.

See Also

Ld Lu Ld qrad

Examples

## 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