Get going sheet for MyLake 1.2

Short instruction for running the MyLake v.1.2 applications for lake Vansjø-Storefjorden

By Tuomo Saloranta, NIVA, 12.11.2007

The MyLake model has been developed at NIVA (Norwegian Institute for Water Research) within various projects, and is freely available, but comes with no warranty (we apply GNU General Public Licence to the model code (http://www.gnu.org/copyleft/gpl.html)). MyLake consists of a set of model code files, and has no graphical user interface. The model applications are controlled via MATLAB scripts written specifically for each application.. Furthermore, any application script lines with “nansum”, “nanmean” etc. type functions will not work without “Statistics toolbox”, although you can download these functions separately. As the application scripts function as “workbenches” their content (most of which is script for plotting of figures of the model output results) is less polished, commented and maintained than the model code files which are version numbered. Any comments and suggestions for model improvement are very welcome.

Installation

1. Copy the folder Mylake_v12_package and all its contents to your computer.
2. Start MATLAB and modify all the path names for model code, observations, and forcing files in the model application script (TSA_modelVAN_v12.m) so that they point to the right folders (search for string “H:\” in order to find these lines).
3. Run the application script. Some information, such as ice-on/off dates, are displayed on command window while the model is running. Figures are plotted when the model run is finished.

Package overview The folder Mylake_v12_package has the following subfolders: • v12, containing the model code • air_sea, containing the MATLAB air-sea toolbox used for surface heat flux calculations • manuals, containing documentation of the model versions 1.1 and 1.2 • Vansjo_application containing the forcing-, parameter- and initial profile Excel files as well as the application script for the Vansjø-Storefjorden application. Observations are included in folder Observations. The Vansjø-Storefjorden application is somewhat calibrated for temperature and water quality, and can be used as a template to built model applications for other lakes. NOTE: Use of the included data is allowed only for model testing purposes. • v12_1, containing revised model files for version 1.2.1 and the documentation for these revisions.

Notes on the model code As the model is based on daily time step (although surface heat balance is solved separately during day- and nighttime), the model grid size (dz) should be larger than the thickness of the surface layer which could undergo significant temperature variations during a day. Otherwise numerical instability may occur in the temperature and ice simulations. This is due to the fact that the uppermost surface layer acts as a “receiver/sender” of the turbulent and longwave heat fluxes. Ice formation is initiated also in this same surface layer.

Some model parameters are still contained in the main model code file solvemodel_v12.m. The same file also contains the few model “switches” with which one can turn on/off e.g. sediment heat flux calculations (see manual for further information).