Vergara - 1976 - Physiological and morphological adaptability of ri

124 cLuxiAnz AND RICE
Relative reight (z-hr")
A
2.0 — LAD(m2-m‘3)
10_ _ _ _ _ _ _t0 0
0 1.0 2.0
Relative wind velocity tutzl-ultirl")
5. A) Profile of wind velocity in and above rice canopy
(Kobayashi. 1973: Uehijima et at. 1974); B) Variation
in aerodynamical properties of a rieefield with plant
growth (See and Yztmaguchi, 1968).
where V», is the friction velocity. K is von Karmank constant. d and z... are
zero-plane displacement and roughness length. respectively’. l5 is an experimental
parameter. and L* is the Monin-Obukhtmt’ length. The second tenn in parentheses
011 the right hand side of Eq. (l4) was introduced for stability correction
of wind profile. On the other hand. wind profile within the rice crop is approximately
expressed
u(z) = uth_)exp(— a0 —
2
where u(h) is the wind velocity at the top of canopy xvith the height of h. and a
is the extinction coefficient. Wind measurements in rice canopies showed values
of extinction coefficient in the range from 2.1 to 2.4 (Krabayashi. 1973; Uchiiima