Validation: Validated against the original running in Excel. Each calculation in the model was individually validated as well. Comments on numerical integration: Euler integration with time steps of 1. In Simile the "time units" were set to "day" and execution was for 364 days as the simulation starts at time 0 (not time 1 as in the Excel model). Comments on running Simile model: Users must specify the temperature controlled growing season themselves. To do this use the following steps which take only a few minutes to complete. Do a trail run of the model and plot a graph of "growing days" versus time in the model run environment. The "Page 2" tab in the model run environment for Miscanmod has this graph set-up ready. The longest stretch of unbroken 0s around the summer on this plot would constitute the growing season. Ignore the odd day showing a value of 1 in an extended summer block of 0s especially if the corresponding average temperature was only slightly below the growth threshold temperature stored in the variable "growing season threshold". From the x-axis of the graph the first and last day actually in the growing season can be estimated. These day numbers can then be checked to find the exact days from a table of "growing days", which is done ready on the "Page 6" tab of the Miscanmod model run environment. The first day in the growing season can be entered into the Simile variable "gs start day" and the last day in the growing season entered into "gs end day". The model is then set-up to run correctly.
Original Model: Language: Excel. Author: John Clifton-Brown. File name of original code:ProdMod(for EuClim)v7.1.xls. Comments: The model runs inside a Microsoft Excel workbook of 13 interlinked worksheets (including 1 sheet of notes). Only one worksheet contains the model, the other sheets either contain the database data, pre-process it or collate the results of the model. A macro takes the input data for each 0.5ox0.5o grid square in turn and applies it to the model's worksheet and then collects the model's results to summarise on another sheet. Overview of original model: The model was developed to provide estimates of above ground biomass yield values for Miscanthus for 0.5ox0.5o grid squares across the whole of Europe. The original data for the model came from databases of monthly radiation, rainfall and temperature averaged over 30 years. Soil moisture holding capacities were likewise taken from a Europe wide database. The monthly values were disaggregated to daily values by linear interpolation to feed to the model as driving variables. The model was then used on each grid square in turn to calculate the end of growing season yield by stepping the model through time with one day time steps. The yield results were then plotted on a map and used to estimate the potential of the crop in meeting carbon emission reduction targets. For the mapping account was also taken of land not available to Miscanthus cultivation or where the yields were too low to be useful. The extensive land area to be modelled with the concomitant need for data along with the relative lack of knowledge of Miscanthus physiology at the time meant that the model needed to be relatively simple and high-level. The model was also configured with the features and constraints of its (highly averaged) European data sets in mind, with yield as the fundamental output of interest.
Purpose: Miscanthus is a giant perennial grass with C4 photosynthesis which is being developed as a source of biofuel. The entire above-ground biomass is harvested after the end of the growing season, once it has undergone complete senescence and drying. It is burnt as a biofuel with the aim of carbon mitigation by replacing fossil fuels and eliminating the inefficient use of grain crops for bioenergy production. Miscanmod models the above ground biomass yield using daily met data as input.
Clifton-Brown J.C., Stampfl P.F. and Jones M.B (2004). Miscanthus biomass production for energy in Europe and its potential contribution to decreasing fossil fuel carbon emissions.. Global Change Biology 10, 509-518.
Originally submitted to PLaSMo on 2010-01-27 13:47:41
Created: 10th Jan 2019 at 17:41