Thermimage (version 2.1)

Te: Operative temperature estimate.

Description

Operative temperature (degrees Celsius) is a measure of the effective temperature an object/animal will be given a specific radiative and convective environment. Basal heat production and evaporative heat loss are assumed to balance each other out.

Usage

Te(Ts=30, Ta=25, Tg=NULL, RH=0.5, E=0.96, rho=0.1, cloud=0, SE=0, V=1, 
L=0.1, c=NULL, n=NULL, a=NULL, b=NULL, m=NULL, type="forced", shape="hcylinder")

Arguments

Ts

Surface temperature (degrees Celsius). Default value is 30. Used in free convection calculation.

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.

V

Air velocity (m/s). Default value is 1.

L

Characteristic dimension (m) of object. Usually the vertical dimension (i.e. height). Default value is 1.

c

coefficient used in forced convection (see Blaxter, 1986, default value is 0.24)

n

coefficient used in forced convection (see Blaxter, 1986, default value is 0.6)

a

coefficient used in free convection (see Gates, 2003, default value is 1)

b

coefficient used in free convection (0.58 upright cylinder, 0.48 flat cylinder, default value is 0.58)

m

coefficient used in free convection (0.25 laminar flow, default value is 0.25)

type

"forced" or "free" - to calculate convection coefficient for either forced or free convection. Default value is "forced"

shape

"sphere", "hplate", "vplate", "hcylinder", "vcylinder" to denote shape and orientation. h=horizontal, v=vertical. Default shape is "hcylinder"

Details

Estimates operative temperature according to calculations in Gates (2003) and Angiletta ()

References

Angiletta, M. J. 2009. Thermal Adaptation: A Theoretical and Empirical Synthesis. Oxford University Press, Oxford, UK, 304 pp. Gates, D.M. 2003. Biophysical Ecology. Courier Corporation, 656 pp.

See Also

qabs hconv

Examples

## The function is currently defined as
function (Ts=30, Ta=25, Tg=NULL, RH=0.5, E=0.96, rho=0.1, cloud=0, SE=0, V=1,
L=0.1, c=NULL, n=NULL, a=NULL, b=NULL, m=NULL, type="forced", shape="hcylinder")
{
    Te <- Ta + (qabs(Ta=Ta, Tg=Tg, RH=RH, E=E, rho=rho, cloud=cloud,
    SE=SE) - StephBoltz()*0.96*(Ta+273.15)^4) / 
    (hconv(Ts=Ts, Ta=Ta, V=V, L=L, c = NULL, n = NULL, a = NULL, b = NULL, m = NULL,
    type=type, shape=shape) + 4*StephBoltz()*0.96*(Ta+273.15)^3)
    Te
  }

# Example

Ts<-40
Ta<-30
SE<-seq(0,1500,100)
Toperative<-NULL
for(rho in seq(0, 1, 0.1)){
  temp<-Te(Ts=Ts, Ta=Ta, Tg=NULL, RH=0.5, E=0.96, rho=rho, cloud=1, SE=SE, V=0.1, 
           L=0.1, type="free", shape="hcylinder")
  Toperative<-cbind(Toperative, temp)
}
Toperative<-data.frame(SE=seq(0,1500,100), Toperative)
colnames(Toperative)<-c("SE", seq(0,1,0.1))
matplot(Toperative$SE, Toperative[,-1], ylim=c(30, 50), type="l", xlim=c(0,1000),
        ylab="Operative Temperature (C)", xlab="Solar Radiation (W/m2)", lty=1,
        col=flirpal[rev(seq(1,380,35))])