List of principal symbols

b'

Calibration factor for square root minimum temperature prediction

C

Certainty that an event will occur (i.e. C = 1 - R)

C_V

J m^-3 °C^-1

Volumetric heat capacity of soil

E

kPa

Water vapour pressure or actual water vapour pressure

E

kg m^-2 s^-1

Water vapour mass flux density

E

W m^-2

Energy from radiation

e_a

kPa

Saturation vapour pressure at temperature T_a

e_d

kPa

Saturation vapour pressure at the dew-point temperature T_d (note that e_d = e)

e_f

kPa

Saturation vapour pressure at the frost-bulb temperature T_w

e_i

kPa

Saturation vapour pressure at the ice point temperature T_i (note that e_i = e)

E_L

m

Elevation relative to mean sea level

E_o

MJ l^-1, MJ kg^-1

Energy output

E_R

W m^-2

Energy requirement

e_s

kPa

Saturation vapour pressure over a flat surface of liquid water or ice at temperature T

e_w

kPa

Saturation vapour pressure at wet bulb temperature T_w

F

—

Function to account for cloudiness effect on long-wave downward radiation

F_C

l h^-1, kg h^-1

Fuel consumption rate

G

W m^-2

Soil heat flux density

G₁

W m^-2

Soil heat flux density at the soil surface (i.e. G₁ = G)

G₂

W m^-2

Soil heat flux density measured with a flux plate at some depth in the soil

G_sc

W m^-2

Solar constant. G_sc = 1367 W m^-2

H

—

Number of hours from two hours past sunset until sunrise

H

W m^-2

Sensible heat flux density

H_H

—

Heaters per hectare

K_h

W m^-1 °C^-1

Thermal conductivity

K_s

W m^-1 °C^-1

Thermal conductivity of the soil

L

Latent heat of vaporization

LE

W m^-2

Latent heat flux density

p

—

p = 86 400 s per day

P

—

Probability that an event will occur in any given year

P_b

kPa

Barometric pressure

R

—

Risk or probability that an event will occur during a known number of years

R₁

°C

Residual R₁ = T_n - T_p

R₁'

°C

Residual R₁ prediction using T_d at time t₀

R_A

mm h^-1

Sprinkler application rate

R_Ld

W m^-2

Downward positive long-wave (terrestrial) radiation

R_Ln

W m^-2

Net long-wave radiation (R_Ln = R_Ld + R_Lu)

R_Lu

W m^-2

Upward negative long-wave (terrestrial) radiation

RMSE

RMSE = [S(Y-X)²/n]^0.5 where n is the number of pairs of random variables Y and X

R_n

W m^-2

Net radiation

R_o

°C

Range of soil surface temperature

R_Sd

W m^-2

Downward positive short-wave (solar) radiation

R_Sn

W m^-2

Net short-wave (solar) irradiance (R_Sn = R_Sd + R_Su)

R_So

W m^-2

Downward short-wave (solar) radiation from a clear sky

R_Su

W m^-2

Upward negative short-wave (solar) radiation

R_z

°C

Range of soil temperature at depth z in the soil

T

°C

Temperature

t

—

Time

T₁₀

The critical temperature at which 10 percent damage is expected

T₉₀

The critical temperature at which 90 percent damage is expected

T_a

°C

Air temperature

T_C

—

Critical temperature or critical damage temperature - the temperature at which a particular damage level is expected

T_cf

°C

Citrus fruit peel temperature

T_d

°C

Dew-point temperature

T_e

°C

Equivalent temperature (the temperature achieved if all latent heat in a parcel of air is adiabatically converted to sensible heat)

T_f

°C

Frost-bulb temperature

t_f

—

Time at the end of a sample interval

T_i

°C

Ice point temperature

t_i

—

Time at the beginning of a sample interval

T_i

°C

Temperature at the i^th hour following t₀

T_K

K

Absolute temperature in kelvins (273.15 K = 0°C)

T_n

°C

Observed minimum temperature at sunrise

t₀

—

Starting time for FFST.xls application (i.e. two hours past sunset)

T₀

°C

Temperature at time t₀

T_p

°C

Minimum temperature predicted from air and dew-point temperature at t₀

t_p

—

Time of sunrise for predicted minimum temperature (T_p)

T_p'

°C

Minimum temperature predicted using T₀ at time t₀

T_sf

°C

Soil temperature at the end of a sample interval

T_si

°C

Soil temperature at the beginning of a sample interval

T_w

°C

Wet-bulb temperature

V_m

—

Volume fraction of minerals in the soil

V_o

—

Volume fraction of organic matter in the soil

z

m

Depth below or height above the surface (e.g. in metres)

D

kPa °C^-1

Slope of saturation vapour pressure curve at temperature T

a

—

Albedo (i.e. reflection of short-wave radiation)

e

—

Emissivity

e₀

—

Apparent emissivity downward from clear sky

g

kPa °C^-1

Psychrometric constant

k_T

m² s^-1

Thermal diffusivity in the soil

l

MJ kg^-1

Latent heat of vaporization

l_max

m

Wavelength of maximum energy emission
(i.e. a function of temperature)

m_d

—

Mean value for a date

q

—

Volume fraction of water in the soil

s

W m^-2 K^-4

Stefan-Boltzmann constant s = 5.67 × 10^-8 W m^-2K^-4

s

mol m^-3

Density of air

s_d

Mg m^-3

Density of water

s_d

—

Standard deviation of a date