ISSN:
1573-1472
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract Accurate and fast-response measurements of space-time observations of specific humidity were made above a drying land surface at the University of California at Davis, using the Los Alamos water Raman-lidar. In an attempt to quantify the space-time intermittency features of turbulent flows in the lower atmosphere, a multifractal analysis of these water vapour measurements was performed. The structure of the specific humidity, θ(x, t), was analyzed quantifying a scalar gradient measure $$( \sim [{\text{grad }}\theta {\text{]}}^{\text{2}} )$$ both in time and space, for all possible one-dimensional cuts, i.e. $$\chi _t (x,t) = [\partial \theta (x,t)/\partial t]^2$$ and $$\chi _x (x,t) = [\partial \theta (x,t)/\partial x]^2$$ . The results confirm the multifractal nature of this scalar gradient measure (a type of scalar dissipation rate) and show that humidity measurements at fixed times (χx) are more intermittent (e.g. have less entropy dimension) than those at fixed locations in space (χt). Similar multifractal behaviour of the spatial data, with and without a transformation from the observed wind velocities, supports the validity of Taylor's hypothesis for the studied fields.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00709237
