Yague, C.; Viana, S.; Maqueda, G.; Redondo, J. M.
Nonlinear processes in geophysics
Vol. 13, num. Special Issue, p. 185-203
DOI: 10.5194/npg-13-185-2006
Data de publicació: 2006-06-21
Article en revista
Data from SABLES98 experimental campaign
have been used in order to study the influence of stability
(from weak to strong stratification) on the flux-profile relationships
for momentum, m, and heat, h. Measurements
from 14 thermocouples and 3 sonic anemometers at three
levels (5.8, 13.5 and 32 m) for the period from 10 to 28
September 1998 were analysed using the framework of the
local-scaling approach (Nieuwstadt, 1984a; 1984b), which
can be interpreted as an extension of the Monin-Obukhov
similarity theory (Obukhov, 1946). The results show increasing
values of m and h with increasing stability parameter
=z/3, up to a value of 1–2, above which the values remain
constant. As a consequence of this levelling off in m
and h for strong stability, the turbulent mixing is underestimated
when linear similarity functions (Businger et al., 1971)
are used to calculate surface fluxes of momentum and heat.
On the other hand when m and h are related to the gradient
Richardson number, Ri , a different behaviour is found,
which could indicate that the transfer of momentum is greater
than that of heat for high Ri . The range of validity of these
linear functions is discussed in terms of the physical aspects
of turbulent intermittent mixing.
Data from SABLES98 experimental campaign
have been used in order to study the influence of stability
(from weak to strong stratification) on the flux-profile relationships
for momentum, m, and heat, h. Measurements
from 14 thermocouples and 3 sonic anemometers at three
levels (5.8, 13.5 and 32 m) for the period from 10 to 28
September 1998 were analysed using the framework of the
local-scaling approach (Nieuwstadt, 1984a; 1984b), which
can be interpreted as an extension of the Monin-Obukhov
similarity theory (Obukhov, 1946). The results show increasing
values of m and h with increasing stability parameter
=z/3, up to a value of 1–2, above which the values remain
constant. As a consequence of this levelling off in m
and h for strong stability, the turbulent mixing is underestimated
when linear similarity functions (Businger et al., 1971)
are used to calculate surface fluxes of momentum and heat.
On the other hand when m and h are related to the gradient
Richardson number, Ri , a different behaviour is found,
which could indicate that the transfer of momentum is greater
than that of heat for high Ri . The range of validity of these
linear functions is discussed in terms of the physical aspects
of turbulent intermittent mixing.