Narrow Results

A biased coinflip Ansatz provides a stochastic regional scale surface climate model of minimum complexity, which represents physical and stochastic properties of the rainfall–runoff chain. The solution yields the Schreiber–Budyko relation as an equation of state describing land surface vegetation, river runoff and lake areas in terms of physical flux ratios, which are associated with three thresholds. Validation of consistency and predictability within a Global Climate Model (GCM) environment demonstrates the stochastic rainfall–runoff chain to be a viable surrogate model for regional climate state averages and variabilites. A terminal (closed) lake area ratio is introduced as a new climate state parameter, which quantifies lake overflow as a threshold in separating water from energy limited climate regimes. A climate change analysis based on the IPCC A1B scenario is included for completeness.

In semi-arid environments, vegetation is not homogeneous, but rather self-organized into spatial patterns. And spatial patterns of vegetation are a central feature of these semi-arid areas. Thus, in this paper, we give detailed analysis of a vegetation model in arid ecosystems. According to the dispersion relation formula, we discuss the changes of the wavelength, with respect to the rainfall and plant mortality rate. The obtained results show that, as rainfall being decreased, spotted, striped and "black-eye" patterns emerge successively.

This paper introduces a new technique in ecology to analyze spatial and temporal variability in environmental variables. By using simple statistics, we explore the relations between abiotic and biotic variables that influence animal distributions. However, spatial and temporal variability in rainfall, a key variable in ecological studies, can cause difficulties to any basic model including time evolution.

The study was of a landscape scale (three million square kilometers in eastern Australia), mainly over the period of 1998–2004. We simultaneously considered qualitative spatial (soil and habitat types) and quantitative temporal (rainfall) variables in a Geographical Information System environment. In addition to some techniques commonly used in ecology, we applied a new method, Functional Principal Component Analysis, which proved to be very suitable for this case, as it explained more than 97% of the total variance of the rainfall data, providing us with substitute variables that are easier to manage and are even able to explain rainfall patterns. The main variable came from a habitat classification that showed strong correlations with rainfall values and soil types.

A three-dimensional σ-coordinate LES model is proposed to simulate hydrodynamic behavior of free surface turbulent flows with vegetation. Vegetation is considered as an internal source of resistant force and a phenomenon model is employed to express the performance of vegetation in the flows. The model is modified from the σ-coordinate LES model developed by Lin and Li (2002, International Journal for Numerical Methods in Fluids, Vol 38, Page 1045-1068). The governing equations of the modified model include additional terms for drag force produced by vegetation and the modified model is distinctive in that not only compound channel flow can be solved but also wave motion through vegetation in coastal region can be taken into account. An operator splitting method, which splits the solution procedure into advection, diffusion and pressure correction steps, is employed so that different numerical schemes can be used for the solution of different physical processes. The model has firstly been applied to simulate the hydrodynamic behavior of turbulent flow in compound open channel with partly vegetated region. Then by using the model the attenuation of wave movement due to vegetation in coastal region is simulated. The results reveal that the present model has the capacity of describing three-dimensional structure of large eddy appearing in free surface turbulent flows with vegetation. It is believed that the model will become a useful tool to pursue further study of wave hydrodynamics in coastal region with the presence of aquatic vegetation.