After downloading and building (if necessary) the model, the latter can be run immediately using the default initial conditions built into the model. Unlike three-dimensional atmospheric models that require large and carefully filtered datasets for initialization, the one-dimensional Simsphere is far less complex to execute. Perhaps the most extensive document is a workbook, which can serve as a tutorial for the user and as a teaching tool. The Simsphere website ( ) also contains, besides the aforementioned references to published papers, many useful documents: tables of input and output variables, an extended description of the model, the uses of the input variables, and a sample output table. Many of the mathematical details of the model, including some validation, can be found on the Simsphere website and in the following papers on this site (to be discussed later): Gillies and Carlson (1995), Lynn and Carlson (1990), Carlson and Lynn (1991), Olioso et al. Instead, we will list only a few of the most relevant and useful papers in order to facilitate an understanding of the model and its operation on the web. Finally, we describe the workbook.Ĭonsisting of approximately 50 pages of Fortran-90 code, Simsphere is not able to be fully described here or in any single document or publication. Next, we describe the website and show how the model can be downloaded and run within the local user environment. First, we briefly describe some of the model structure and capabilities. The purpose of this paper is to inform the scientific community of the availability of Simsphere and to briefly describe its structure in order that the user can access and download the model from the internet. Accompanying the model on its website are many documents describing the model structure, its access to the user, a flow diagram of its structure, input, and output, as well as relevant journal references or publications (including this paper) describing parts of Simsphere and its various applications. What distinguishes Simsphere, besides being the product of 30 years of continuous development and validation, is that it is now being made freely available for download on the internet, both as an executable file and as a code that can be compiled and modified by users. Figure 2 is an example of a graph made from its output, showing variations in the various flux components during a 24-h simulation. Simsphere’s basic structure is encapsulated in Fig. Simsphere also allows for the flux of carbon dioxide from the atmosphere to the plant canopy. As such it simulates the fluxes of heat and moisture exchanges between these three layers in parallel over bare soil and vegetated surfaces, while allowing changes to occur in the atmospheric temperature, dewpoint, and wind velocity during daylight and at night and changes in temperature and water content in the substrate. One of a class of so-called two-stream models, Simsphere simulates fluxes over a surface area consisting of fractional parts of vegetation and bare soil and blends the fluxes in the atmosphere weighted by the fractional vegetation cover. Simsphere is a time-dependent, one-dimensional, two-stream model that accounts for the interaction between the soil, the vegetation, and the atmosphere over a 24-h day.
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