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February 27, 2009

New Equation of state II

Here is a comparison of the development of the temperature field at station 1 for two different runs: One using the original ROMS Equation of state (EOS) and one using Chen and Millero. The bottom panel is the difference between the two. These effects are subtle but I am a lot more comfortable with the development of the temperature field wit h the C&M EOS.

EOS_comparison_1.png

February 20, 2009

the general approach

The general approach for the first set of model runs is to simulate a 1-year period, with and without ice, and observe the difference.

For this 1-year period, I chose to use forcing data from 2008, since that's the year for which I have the most MODIS data. Still missing a bit but its a good start.

The forcing data is written out in 3-hour intervals for the time-varying components.

For an initial condition, I sent the entire model temperature field equal to 3.8C, and set velocities to zero. It will be interesting to study the sensitivity of the model results to this initial state- i.e. how long does it take to erase any memory of the initial condition?

the model is run with a 1200s time step for an entire year. This is about 26k time steps. Without the ice model ,it takes about 4h to run. With the ice model about 6h.

I output history data daily, average values daily, and station values (at three stations located roughly where the NOAA buoys would be) hourly.

The extended entry has a list of the cppdefs I use. For the ice model, I define ICE_MODEL.

Continue reading "the general approach" »

February 18, 2009

Welcome to the Ice blog

This is a discussion site dedicated to the Ice and Carbon grant. The blog is here to facilitate discussion between the various participants in this grant.

The primary goal of the grant is to develop a better understanding of the role that ice plays in determining annual and interannual variability in both the physical structure (i.e. dynamics/ thermodynamics) and the biogeochemical structure of Lake Superior, specifically the Carbon balance.

We are approaching this problem with two approaches: A modeling program designed to test the impact of different climate scenarios on both idealized and realistic lake models, and an observational program designed to collect primarily physical data (temperature and velocities) at a variety of locations around Lake Superior over the next three years.

The main participants in this work are:
Jay Austin, University of Minnesota Duluth
Katsumi Matsumoto, University of Minnesota, Twin Cities
Brooke White, Graduate Student, UM- Twin Cities
Erik Brown, University of Minnesota, Duluth
and more to be added.