Biomedical subjects

Tiefan Pei

Publications and source records attributed to Tiefan Pei.

13 recordsLinked to original sources

PubMed2006

[Application and verification of distributed model in simulating watershed evapotranspiration].

Based on the conventional observed meteorological data during 1989 approximately 2000, a distributed model was employed to simulate the temporal and spatial distribution of the potential and actual evapotranspiration in the upper Zagunao watershed of Sichuan Province. Grids of 500 m and step of 1 d were used to describe the spatial and temporal heterogeneity and variability in the study area. The potential evapotranspiration was simulated by a deformation form of Penman-Monteith Equation, and a method for calculating actual evapotranspiration was proposed, with the underlying conditions considered. The results showed that the relative error of the normal annual evapotranspiration in the 12 years between the simulation and the calculation was 3.47%, with a reasonable temporal and spatial distribution. The research results provided an effective method for the distributed rainfall-runoff model in simulating actual evapotranspiration.

Mathematics↗

PubMed2006

[Soil moisture dynamics under broad-leaved Korean pine forest in Changbai Mountains].

The located observation on the soil moisture dynamics under broad-leaved Korean pine forest in Changbai Mountains in 1990 - 1992 and 2003 showed that the seasonal variation of soil moisture content could be divided into five periods, i. e., gathering water stage in spring, consuming water stage in arid season, holding water stage in rainy season, losing water stage in autumn, and relatively stable stage of soil moisture in winter-spring. By using standard deviation and variation coefficient, the vertical layers of soil moisture were divided into rapid change layer, active layer, and sub-active layer. Correlation analysis was applied to analyze the relationships of moisture content among different soil layers and the correlation between soil moisture and precipitation in the same period.

China↗

PubMed2006

[Estimation of rainfall interception by broad-leaved Korean pine forest in Changbai Mountains].

Rainfall interception by forest canopy is an important process of water resources cycle in forest watershed. Most studies focused on the relationships of the interception with the precipitation in one or more rainfall events, without considering rainfall density and vegetation characteristics. By using a semi-theoretical model of canopy rainfall interception model, taking rainfall intensity and leaf area indices as inputs and canopy wetness index as parameter, and combining with Penman-Monteith equation, this paper simulated the rainfall interception by the broad-leaved Korean pine forest canopy in Changbai Mountains, and estimated the total interception of rainfall events from 1 May to 30 September 2004. The results showed that the total interception was 39.96 mm, occupying 10.2% of the precipitation, and the estimated results agreed well with the measured ones. Based on the estimated results, the relationships between interception and rainfall on different temporal scales were analyzed, which suggested that with the increase of temporal scale from 30 min to a month, the correlation between interception and rainfall became more and more obvious.

China↗

PubMed2005

[Discussion on hydrologic scaling].

Hydrologic scaling is the hotspot and frontier of today's hydrologic research, which includes three different meanings distinguished from each other, i.e., process scale, observation scale and modelling scale. As a characteristic of hydrologic scale, dominant process scale has been paid more attention. Hydrologic scaling includes the scaling of hydrologic models, parameters, state variables and inputs, which owns special research methods respectively. The difficulty of hydrologic scaling mainly comes from the organized complexity of hydrologic systems, the heterogeneity and variability in space and time, and the insufficiency of data. The ubiquitous self-similarity of natural river networks makes itself an important part of hydrologic scaling research. The combination of various techniques and theories is needed to motivate hydrologic scaling research.

Ecosystem↗

PubMed2005

[Construction and verification of distributed rain-runoff model for forested watershed in alpine and gorge region].

Considering of the main hydrological characteristics in the upper Zagunao River watershed of the upper reach of Minjiang River, general hydrological models were selected to construct the distributed rainfall-runoff process model for the forested watershed in typical alpine and gorge terrains. Calibration of too many regional parameters was avoided to assure the transportability of the models in similar watersheds. Two flow series of 1 000 hours in 1999 and 2000 were simulated by using the distributed model. The runoff hydrograph, accumulative runoff volume, peak discharge, and peak time showed good fittings with observed series. The simple structure and less empirical parameters gave the distributed model the ability to simulate the rainfall-runoff processes in similar watershed across scales, which provided the basic approach to the hydrological scaling research.

Ecosystem↗

PubMed2005

[Application of phenological pattern recognition in ecological dynamic forecasting].

This paper described the principles, methods, and procedures of ecological dynamic forecasting by the automation techniques of pattern recognition and mathematical logic judgment on the basis of phenological data and model output maps from T42L9 numerical weather prediction model. This new forecasting method proposed on the basis of modern meteorology and automation techniques enables the classic phenology to apply to a new field ecological forecasting. It enables phenological forecasting to develop from single-station forecasting stage to regional forecasting stage, which is greatly corresponded to the development stage from single station forecasting stage to synoptic stage in weather forecasting, and enables agro-meteorological forecasting to develop from qualitative and statistical forecasting stage to ecological dynamic forecasting stage. With this new qualitative forecasting method, both the predicted objective and predictors are of considerable bio-physical interests. The ecological dynamic forecasting method could be applied to crop sowing, crop growth, irrigation and fertilization, and diseases and pests

Computer Simulation↗

PubMed2005

[Research advances in inverse methods used for modeling plant-atmosphere exchange].

To estimate the source/sink and the vertical fluxes of mass and energy within and above plant canopies continues to be a critical research problem in biosphere-atmosphere exchange processes. The underlying approaches in such problem are to exploit the natural properties of turbulence within and above vegetation, such as Lagrangian inverse analysis, high order Eulerian closure model, and hybrid Eulerian-Lagrangian method. This paper introduced the recent development in multilayer turbulent transport methods to compute the distributions of the strengths of scalar sources and sinks within plant-atmosphere continuum, and in particular, focused on the so-called "inverse methods", and described above three methods and their characteristics in detail. The limitation and prospect of these methods were also mentioned.

Air↗

PubMed2005

[Research progress on unsaturated and saturated soil water movement in forest catchments].

This paper reviewed the studies on the movement ways, i. e., infiltration, phreatic evaporation, ground water recharge and interflow, of unsaturated and saturated soil water in forest catchments, and introduced the present advances in soil hydraulic parameters, including soil water characteristic curve, and unsaturated and saturated soil hydraulic conductivity. Research directions in the future were also proposed.

Models, Theoretical↗

PubMed2004

[Effects of climate change on forest succession].

Forest regeneration is an important process driven by forest ecological dynamic resources. More and more concern has been given to forest succession issues since the development of forest succession theory during the early twentieth century. Scientific management of forest ecosystem entails the regulations and research models of forest succession. It is of great practical and theoretical significance to restore and reconstruct forest vegetation and to protect natural forest. Disturbances are important factors affecting regeneration structure and ecological processes. They result in temporal and spatial variations of forest ecosystem, and change the efficiencies of resources. In this paper, some concepts about forest succession and disturbances were introduced, and the difficulties of forest succession were proposed. Four classes of models were reviewed: Markov model, GAP model, process-based equilibrium terrestrial biosphere models (BIOME series models), and non-linear model. Subsequently, the effects of climate change on forest succession caused by human activity were discussed. At last, the existing problem and future research directions were proposed.

Climate↗

PubMed2004

[Research advances in dynamic mechanism and its simulation of eco-hydrological process in forest catchment].

Hydrological process is the key link between climatic fluctuations and ecologic dynamics of forests at spatial and temporal scales. To some extent, global climate change and large-scale human's activities will impact the spatial-temporal changes of eco-hydrological process in forest catchments in the future. Therefore, researches on the dynamic mechanism of eco-hydrological processes in forest catchments play a crucial role in understanding and controlling the rational use of ecological resources, resuming regional ecology, and sustainable development in economy. This paper described the interception, evapotranspiration and rainfall-runoff of forest ecological system and their effects on hydrological process. The spatial structure of soil moisture and its evolution with time were also the cause and consequence of forest. The spatial-temporal interaction between hydrologic and ecologic dynamics, the application of distributed hydrological model, and the eco-hydrological dynamics and cybernetics of forest would be the most exciting frontiers of the relative researches in the future.

Climate↗

PubMed2003

[Calculation of parameters in forest evapotranspiration model].

Forest evapotranspiration is an important component not only in water balance, but also in energy balance. It is a great demand for the development of forest hydrology and forest meteorology to simulate the forest evapotranspiration accurately, which is also a theoretical basis for the management and utilization of water resources and forest ecosystem. Taking the broadleaved Korean pine forest on Changbai Mountain as an example, this paper constructed a mechanism model for estimating forest evapotranspiration, based on the aerodynamic principle and energy balance equation. Using the data measured by the Routine Meteorological Measurement System and Open-Path Eddy Covariance Measurement System mounted on the tower in the broadleaved Korean pine forest, the parameters displacement height d, stability functions for momentum phi m, and stability functions for heat phi h were ascertained. The displacement height of the study site was equal to 17.8 m, near to the mean canopy height, and the functions of phi m and phi h changing with gradient Richarson number R i were constructed.

Mathematics↗

PubMed2003

[Research progress on hydrological scaling].

With the development of hydrology and the extending effect of mankind on environment, scale issue has become a great challenge to many hydrologists due to the stochasticism and complexity of hydrological phenomena and natural catchments. More and more concern has been given to the scaling issues to gain a large-scale (or small-scale) hydrological characteristic from a certain known catchments, but hasn't been solved successfully. The first part of this paper introduced some concepts about hydrological scale, scale issue and scaling. The key problem is the spatial heterogeneity of catchments and the temporal and spatial variability of hydrological fluxes. Three approaches to scale were put forward in the third part, which were distributed modeling, fractal theory and statistical self similarity analyses. Existing problems and future research directions were proposed in the last part.

Models, Theoretical↗

PubMed2002

[Determination and calculation of evapotranspiration of broad-leaved Korean pine forest on Changbai Mountain].

In this paper, the Et of broad-leaved Korean pine forest on Changbai Mountain was determined by water balance method, and calculated by Bowen ratio-energy balance (BREB) method in July, August and September, 2001. The total Et was 288.18 mm and 214.94 mm, respectively, and the daily average Et in each month was gained, while the rainfall is 301.9 mm. Furthermore, the daily Et and hourly Et rate were computed by BREB method, and the availability and precision of the Et determined by water balance and calculated by BREB method was discussed.

China↗