在每周例行的讨论会上，已经是第2次看到学生在使用这个模型了。她使用这个模型模拟不同气候变化情形下，研究区植被净生产力、土壤有机碳和水文，等一系列生态系统关键因子的响应。报告是用韩语讲的，但使用的英语的PPT。尽管不清楚她的详细内容，但是从PPT可以看出主要的工作。总体感觉和Biome-BGC、ArcSWAT等模型类似，由于包含相对复杂的生物物理过程，其模型模拟的结果的准确性有了较大程度的提高。所以在网上查了一下这个模型情况，将英文网页的内容拷贝如下（不做翻译），有兴趣的话，可以去研究一下这个模型。

这个是该项目的网页http://fiesta.bren.ucsb.edu/~rhessys/

Introduction

RHESSys is a GIS-based, hydro-ecological modeling framework designed to simulate carbon, water and nutrient fluxes. RHESSys combines both a set of physically based process models and a methodology for partitioning and parameterizing the landscape. RHESSys' architecture models the spatial distribution and spatial-temporal interactions between the different processes at the watershed scale. RHESSys, as described here, presents a significant modification of earlier versions of RHESSys as described in Band et al., (1991, 1993) and referenced by Mackay and Band (1997), Creed and Band (1998) etc..
RHESSys process models have been adapted from several pre-existing models. Specific algorithms within these original models have been modified to reflect various developments in the associated literature or to fit within the RHESSys modeling framework. The original process models include the following:

• The MTN-Clim model (Running et al, 1987) uses topography and user supplied base station information to derive spatially variable climate variables such as radiation and to extrapolate input climate variables over topographically varying terrain.
• An ecophysiological model is adapted from BIOME-BGC (Running and Coughlan, 1988; Running and Hunt, 1993) to estimate carbon, water and potentially nitrogen fluxes from different canopy cover types.
• Distributed hydrologic models – The original RHESSys utilized a single approach, TOPMODEL, to model soil moisture redistribution and runoff production. We now include two approaches:
  • TOPMODEL (Beven and Kirkby, 1979) is a quasi distributed model. TOPMODEL distributes hillslope soil moisture based on a distribution of a topograhically defined wetness index.
  • An explicit routing model is adapted from DHSVM (Wigmosta et al., 1994) which models saturated subsurface throughflow and overland flow via explicit connectivity. An important modification from the grid-based routing in DHSVM is the ability to route w ater between arbitrarily shaped surface elements. This allows greater flexibility in defining surface patches and varying shape and density of surface tesselation.

Associated with the RHESSys simulation are a number of interface programs which organize input data into the format required by the RHESSys simulation model. These include a standard GIS-based terrain partitioning program, r.watershed, and other basic GIS routines as part of the GRASS GIS system and two RHESSys specific programs:

1. GRASS2WORLD (derives landscape representation from GIS images)
   
2. CREATE_FLOWPATHS (establishes connectivity between spatial units)

These programs include methods for partitioning a landscape into hydrologically distinct units, establishing the connectivity between the units and determining how input data should be assigned to the RHESSys framework. (An ArcView interface, RAIMEnt, which combines some of the features offered by these various programs, has also been developed (Tenenbaum, 1998).

Figure 1 presents an overview of input data into, internal processing and flow of control within, and derived output for the RHESSys modeling system. The different components of this system will be described in the documents on this website.

Figure 1

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