Liang Fuming

Numerical simulations of land surface physical processes and land-atmosphere interactions over oasis-desert/Gobi region

A land-surface physical process model was coupled with a mesoscale atmospheric model. This coupled model was then used to simulate the interactions between land and the atmosphere, including surface temperature, net radiation, sensible heat flux and latent heat flux over a desert/Gobi with an oasis in northwestern semiarid regions in China. Comparisons between observations and simulations were made over the oasis and the desert/Gobi, respectively. Both cold island effect and wet island effect, the so-called oasis effect, were observed and simulated. Lower temperature, higher specific humidity and weaker turbulent transfer were present over the oasis than the desert/Gobi. A subsidence occurred over the oasis, leading to a thermally-generated mesoscale circulation.

Numerical Simulation of the Interaction between Forest Ecological System and Atmospheric Boundary Layer

Based on the basic principles of the micrometeorology of atmospheric boundary layers and vegetation canopy, a numerical model of the interaction between forest ecosystems and atmospheric boundary layers was developed. The model is used to simulate the diurnal variations of heat balance in forest ecosystems, canopy temperatures, ground surface temperatures, as well as the profiles of temporal and spatial distributions of potential temperatures, wind speeds, specific humidity, and turbulence exchange coefficients. Our study indicates that the model can be applied to study the interaction between land surface processes and atmospheric boundary layers over various underlying surfaces and their regional climate effects. This paper will establish a solid foundation to investigations on the coupling of climate models and the biosphere.

The structure and bifurcation of atmospheric motions

The 3-D spiral structure resulting from the balance between the pressure gradient force, Coriolis force, and viscous force is a common atmospheric motion pattern. If the nonlinear advective terms are considered, this typical pattern can be bifurcated. It is shown that the surface low pressure with convergent cyclonic vorticity and surface high pressure with divergent anticyclonic vorticity are all stable under certain conditions. The anomalous structure with convergent anticyclonic vorticity is always unstable. But the anomalous weak high pressure structure with convergent cyclonic vorticity can exist, and this denotes the cyclone’s dying out.The 3-D spiral structure resulting from the balance between the pressure gradient force, Coriolis force, and viscous force is a common atmospheric motion pattern. If the nonlinear advective terms are considered, this typical pattern can be bifurcated. It is shown that the surface low pressure with convergent cyclonic vorticity and surface high pressure with divergent anticyclonic vorticity are all stable under certain conditions. The anomalous structure with convergent anticyclonic vorticity is always unstable. But the anomalous weak high pressure structure with convergent cyclonic vorticity can exist, and this denotes the cyclone’s dying out.

Solitary Wave in Linear ODE with Variable Coefficients

In this paper, the linear ordinary differential equations with variable coefficients are obtained from the controlling equations satisfied by wavelet transform or atmospheric internal gravity waves, and these linear equations can be further transformed into Weber equations. From Weber equations, the homoclinic orbit solutions can be derived, so the solitary wave solutions to linear equations with variable coefficients are obtained.

Vortex of Fluid Field as Viewed from Curvature

The vortex is a common phenomenon in fluid field. In this paper, vortex can be represented by curvature c, which varies with arc length s. The variance of point (x,y) with arc length in stream line satisfies a 2-order variable-coefficient linear ordinary differential equation. The type vortex can be analyzed qualitatively by this ordinary differential equation.

Homoclinic (Heteroclinic) Orbit of Complex Dynamical System and Spiral Structure

Starting from iterated systems, it is shown that the homoclinic (heteroclinic) orbit is a kind of spiral structure. The emphasis is laid to show that there are homoclinic or heteroclinic orbits in complex discrete and continuous systems, and these homoclinic or heteroclinic orbits are some kind of spiral structure.

Solitary Wave and Wave Front as Viewed From Curvature

The solitary wave and wave front are two important behaviors of nonlinear evolution equations. Geometrically, solitary wave and wave front are all plane curve. In this paper, they can be represented in terms of curvature c(s), which varies with arc length s. For solitary wave when , then its curvature c(s) approaches zero, and when , the curvature c(s) reaches its maximum. For wave front, when , then its curvature c(s) approaches zero, and when , the curvature c(s) is still zero, but . That is, is a turning point. When c(s) is given, the variance at some point (x, y) in stream line with arc length s satisfies a 2-order linear variable-coefficient ordinary differential equation. From this equation, it can be determined qualitatively whether the given curvature is a solitary wave or wave front.

Solitary Wave and Wavelet

In this paper, it is shown that the homoclinic orbits exist in iterated functional systems, so do the solitary wave structures. Moreover, Harr father wavelet, Mexican Cap wavelet, and other closed form wavelets have this solitary wave structure, too. So wavelet is a certain kind of solitary wave.

The theoretical model of atmospheric turbulence spectrum in surface layer

It is shown that the slope of energy spectrum obtained from the velocity solution of Kdv—Burgers equation lies between —5/3 and—2 in the dilogarithmic coordinates paper. The spectrum is very close to one of Kolmogorovs isotropic turbulence and Frischs intermittent turbulence in inertial region. In this paper, the Kdv-Burgers equation to describe atmospheric boundary layer turbulence is obtained. In the equation, the 1 /Re corresponds to dissipative coefficientv,R/2t to dispersive coefficientβ, then (v/2β)2 corresponds to 1/ R2e • Ri. We prove that the wave number corresponding to maximum energy spectrumS(k) decreases with the decrease of stability (i.e., the increase of (v / 2β)2 in eddy—containing region. And the spectrim amplitude decreases with the increase of (v / 2β)2 (i.e., the decrease of stability). These results are consistent with actual turbulence spectrum of atmospheric surface layer from turbulence data.