Surface Processes

Question 1

What is a sensible heat flux?

Answer 1

H, upward heat flux at the surface due to conduction and convection

Question 2

What is the latent heat flux?

Answer 2

LE - upward surface heat flux due to evaporation

Question 3

In the bulk formulae for heat fluxes in the ocean, what does each variable denote?

Answer 3

C_H is the bulk coefficient
rho is density
C_p is the specific heat capacity of air
u is wind speed
T is temperature
L is the latent heat due to vaporisation
E is evaporation
q is specific humidity

Question 4

What do skin and s denote as subscripts for temperature?

Answer 4

The subscripts S and skin represent the “normal” surface temperature that
we measure

Question 5

What does q_s(Tskin) represent?

Answer 5

The s denotes the saturation mixing ratio (ie controlled by the Clausius-Clapeyron equation).
This is because the atmosphere just next to the surface can be assumed to
be saturated

Question 6

How do we eliminate Tskin and write LE in terms of H in the bulk formulae?

Answer 6

Linearise the moisture deficit q_s(Tskin) - q_s in terms of the Clausius-Clapeyron equation, and assuming p is constant.

Question 7

What equation defines surface energy balance and relates H to LE? What is the physical interpretation?

Answer 7

R = LE + H
The net downward surface radiative flux (R) is balanced by the sum of the upwards turbulent fluxes.

Question 8

What is the Bowen Ratio?

Answer 8

B = H/LE ratio of sensible to latent heat flux.

Question 9

When do we apply the Penman-Monteith equation?

Answer 9

Includes aerodynamic resistance r_A = 1 / (C_H u)

Question 10

What do we mean by soil hydraulics?

Answer 10

If we are not considering an open body of water where evaporation can readily occur, r_s is added soil resistance.

Question 11

How do we incorporate r_s and r_A into the expressions for latent heat flux?

Answer 11

Divide through by the sum of the terms on the RHS.

Question 12

Over bodies of water, what condition do we use on r_s and how does this affect the equations?

Answer 12

We return to the bulk formulae, where latent heat flux is largely determined by R. r_s «1.

Question 13

Over a dense forest, what condition do we use on r_s and how does this affect our equations?

Answer 13

r_s&raquo_space; 0 and latent heat flux is largely controlled by atmospheric humidity deficit delta q and r_s.