AutoCal is a generic tool for performing automatic calibration, parameter optimisation, sensitivity analysis and scenario management of the numerical modelling engines under MIKE Zero. It interfaces the modelling engines using the MIKE Zero PFS (parameter files system) format for model input and the DFS (data file system) format for model output. AutoCal can also be linked to other modelling engines by interfacing ASCII model input files and creating a bridge between the model output and the DFS file format.
The core of the AutoCal tool consists of the following steps:
1. Provision of a set of model parameter values to the numerical model to be used in a specific model run.
2. Execution of the simulation model using the specified set of model parameter values.
3. Calculation of statistical performance measures of the model output.
The model parameter interface is made via a so-called template file. This file is simply a replica of the model input file in which parameter identification tags are placed at the locations where the numerical values of the model parameters are given. Thus, when AutoCal has to provide a new set of model parameters to the model, the parameter identification tags in the template file are substituted by the numerical values and saved in the model input file to be used when running the model. It is possible to manipulate model parameters in different model input files. For each model input file a corresponding template file is defined.
NOTE: The character “!” is used as a delimiter in the template file to identify the parameters to be manipulated during the simulation. I.e. the character “!” is a reserved character for AutoCal and cannot be used anywhere else in the model input, e.g. in text strings or file names.
AutoCal allows parameters to be defined as functions of other parameters that are manipulated in the AutoCal run. In this case general equations can be specified that defines the relations between the dependent model parameter and the other parameters. AutoCal provides the set of independent parameter values and the dependent parameters are then calculated automatically from these values using the defined equations. Both dependent and independent parameter values are then substituting their corresponding parameter identification tags in the template files. Besides the standard arithmetic operators, the equation tool includes a large number of mathematical functions.
A parameter may also be defined as a constant. In this case the constant value defined in AutoCal is substituting the corresponding parameter identification tag in the template file. This feature is especially useful when a sensitivity analysis is performed prior to the parameter optimisation. In this case the sensitivity analysis typically includes a long list of parameters. From the results of the sensitivity analysis the most sensitive parameters are retained in the subsequent parameter optimisation. Instead of making a new AutoCal setup, the same setup as used in the sensitivity analysis can be applied simply by setting the insensitive parameters to constant values.
A model simulation in AutoCal can be defined as a sequence of individual model runs. AutoCal supports execution of all the MIKE Zero model engines. In this case the model simulation setup file is given as input. In addition, AutoCal enables execution of any executable (.exe) or batch (.bat) file. In this case the executable as well as the corresponding list of arguments are given as input.
Whether AutoCal is used for parameter optimisation, sensitivity analysis or scenario management, the performance of the model simulation given the specified parameter set should be assessed. This is done by calculating statistical performance measures. These measures are typically comparison statistics that compare measurements or, in general, target values with corresponding simulated values.
For calculating the comparison statistics AutoCal requires that simulation results and corresponding observations are given as time series in DFS0 files. If the output from a model engine is not explicitly given in DFS0 format, a processing of simulation results is required to transform the simulation results at measurement locations into DFS0 format. This post-processing is then part of the sequence of model runs defined in AutoCal. Typically post-processing is required for MIKE 11 result files (.res11) and for models that provide results in 1D, 2D or 3D grid files (.dfs1, .dfs2 and.dfs3). For application of AutoCal with modelling engines that are not included in MIKE Zero the COM components included in the MIKE Objects Time Series Package can be used to create DFS0 time series files from the model output files.
Before setting up AutoCal, the simulation model should be properly tested. At least one model run should be performed to create the output files that are needed in the AutoCal setup.