1

Energy budget

R_n = G + H + E

2

Net radiation

R_n = (R_Si -R_So) + (R_Li - R_Lo)

3

Subsurface-heat flux (for soil)

G = HF_s + {Ts d_{bls Bs} [C_s + (W C_w)]}

4

Subsurface-heat flux (for water)

G = T_w d_{bws w} C_w

5

Sensible-heat flux

H = _a C_a k_h dT/dz_t

6

Latent-heat flux

E = ( _a k_v / P) de/dz_e

7

Available energy

E_a = R_n - G

8

Bowen ratio

= (H / E) = [(P C_a) / ( )] [(T_l - T_u) / (e_l - e_u)]

9

Evapotranspiration

ET = [E_a /( _w)][(P C_a) / ( )] [(T_l - T_u) / (e_l - e_u)+1]

10

Latent-heat flux; eddy-correlation method

E = covariance (w_v)

11

Sensible-heat flux; eddy-correlation method

H = _a C_a covariance (wT)

12

Relative closure

Cr = [(R_n - G - H - E)/R_n - G]100

C_a

Specific heat of air at a constant pressure (energy per mass per temperature)

C_s

Specific heat of dry soil (energy per mass per temperature)

C_w

Specific heat of water (energy per mass per temperature)

d_bls

Depth below land surface at which heat flux is measured (length)

C_r

Amount of residual imbalance relative to available energy (percent)

d_bws

Depth below water surface at which temperature is measured (length)

de/dz_e

Vapor-pressure gradient near the Earth's surface

dT/dz_t

Temperature gradient near the Earth's surface

e_l,u

Vapor pressure at lower and upper reference point (force per area)

E_a

Available energy (energy per area per time)

E

Rate of water evaporation (mass per area per time)

ET

Rate of evapotranspiration (length per time)

G

Subsurface-heat flux (energy per area per time)

H

Sensible-heat flux (energy per area per time)

HF_s

Heat flux through soil at some measurement depth (energy per area per time)

k_h

Turbulent transfer coefficient of heat in air (area per time)

k_v

Turbulent transfer coefficient of vapor (area per time)

P

Ambient air (barometric) pressure (force per area)

R_Li

Incoming long wave radiation (energy per area per time)

R_Lo

Outgoing long wave radiation (energy per area per time)

R_n

Net radiation (energy per area per time)

R_Si

Incoming short wave radiation (energy per area per time)

R_So

Outgoing short wave radiation (energy per area per time)

T

Instantaneous departure from average temperature

T_l,u

Temperature at lower and upper reference point

W

Gravimetric soil water content (dimensionless)

w

Instantaneous departure from average wind speed (length per time)

Bowen ratio (unitless)

T_s

Change in soil temperature between surface and soil-heat flux measurement depth (temperature per time)

T_w

Change in water temperature (temperature per time)

e

Ratio of molecular weight of water to dry air (dimensionless)

l

Latent heat of vaporization for water (energy per mass)

E

Latent-heat flux (energy per area per time)

_a

Density of air (mass per volume)

_Bs

Bulk density of soil (mass per volume)

_w

Density of water (mass per volume)

_v

Instantaneous departure from average vapor density (mass per volume)