Observations and Modelling of Fronts and Frontogenesis

constant pressure c = 4.1x103 J K1- kg1-, and thermal
expansibility a = l.7xl04 K-) are,
x Ax'
= (g(p*/p0)h*)l/2/f = 2m0u*/f [100 m], (26b)
t = t*tl, t* = [3300 s = 55 mm], (26c)
(h1,h2,h3,H) =h*(h11,h2',h3',H'),
h* = 2m0u*3/(agQ*/cp) [33 m], (26d)
(ul,u2,u3)=U*(ui',u2',u3'),
(v1,v2,v3) =
(P3 Pl,P3 P2P2 P1) =
= fA* [1 cm s'-], (26e)
u*2/th* [3 cm 1.j,
(26f)
*(aQ*/c)(f/u*2) [3x104 kg m3]. (26g)
The vertical scale h is the Monin-Obukhov length. The
ageostrophic velocity scale V* results from the balance of
Coriolis force and vertical stress divergence, and the
geostrophic velocity scale U* from the inertial balance of
Coriolis force and acceleration. The time scale t,i- is chosen
to balance temporal and advective rates of change. The
density scale p* is suggested by the balance of local or
advective heating and surface heat flux. The horizontal
length scale * is the internal deformation radius formed
from h* and p*. Note that the density and horizontal length
scales are small. Much larger density differences and
horizontal scales 0(1 kg m3, 50 kin) characterize the initial
61