42
Fuchs et al. (1969) used a method in which instability in the
lower atmosphere was accounted for in conjunction with the logarithmic
wind profile to calculate the surface mass transfer coefficient. This
involved using the KEYPS function (Panofsky, 1963) to determine the
curvature of the diabetic lapse rate (w) of the logarithmic wind
profile. The surface mass transfer coefficient was calculated from
-2
h = k2WS ( 7 + In (z + D) (2-50)
m Zo
where
hm = transfer coefficient of mass from surface to height, z,
in the air [m-s-1]
k = von Karman constant dimensionlesss]
WS = wind speed at height, z [m-s-1]
D = height displacement [m]
= d + z0
d = height above soil surface where wind velocity is zero
[m]
Z0 = roughness length [m]
z = height above the displacement height [m]
x = curvature of the diabetic lapse rate or diabetic
influence function dimensionlesss]
Fuchs et al. (1969) then calculated the surface heat transfer
coefficient using
hh = hmcpaPa
(2-51)