Presentation day

Today I gave a presentation to the department and Rod March of the USGS and several other USGS employees that were teleconferenced. The presentation was an update on what I have been working on and was meant to spur discussion on what I could be doing better or other aspects of the project that I could explore. I think it went pretty well. Discussion points included

-sensitivity analysis on the parameters of the model vs hand waving calibration
-how the outline of the glacier changes and affects the discharge/mass balance in the model
-how unreliable the discharge data is. Not to expect perfect matches
-in 2004 ash from nearby forest fires covered the glacier and changed melt patterns

Rod March was extremely helpful! Thank you Rod!

I've included jpeg version of the presentation below. The presentation should be a good summary of what I have been doing for the past month. The model is pretty much calibrated at this point. Now I am ready to get the future climate data from Jing Zhang and run the model using the future data and then analyze it and see what looks interesting!

Grid files in MATLAB

Regine gave me a matlab program to read .bin files so I am completely disconnected from IDL now and have more flexibility. Here is what the grids look like once they are read by MATLAB. This is more flashy than it is that helpful, but it's nice to visualize the glacier.Gulkana DEM. Elevation of Gulkana area

Gulkana glacier elevation. This is the elevation of just the glacier.



Visualizing slope of the area. Dark blue is flat (0°) and and red is vertical (90°).




Visualizing aspect.

Day 12 - Adding Mass Balance

All 40 years of simulated and measured data yay!

Today after simulating all 40 years of data using model 1 (woohoo!) I worked on getting mass balance output. The USGS measured mass balance data is pretty messy and hard to work with, but it will do for now just starting. After plotting the mass balance data (measured vs simulated) it looks really bad so there is something wrong either with the data or the model. Hopefully I will figure that out.

There are three mass balance components that the model works with; winter, summer, and net. Winter mass balance measured the change in mass balance during the winter, summer mass balance measures the change during the summer, and the net is the winter minus the summer or the total mass balance for the year. Snow accumlates during the winter so mass balance is positive and melts in the summer so mass balance is negative and the net measures whether more snow accumlated or melted during the year.

Mass balance combined with disharge gives a pretty good idea about how the glacier is melting and fitting the model to both mass balance and discharge ensures that the model is appropriately and accurately modeling the glacier dynamics.


PLAN:
refine mass balance
more matlab!
calibrate model 1 and 2

Day 11 - Output!

Since the last major accomplishment of making the most basic model run and produce some output, there were some roadblocks and bugs in the model that have taken the last few days to iron out. I can also now run the model completely on my computer independent of Regine's computer which is nice.

The melt of the glacier is accounted for in the discharg so we had to get that component working for the model. The model reads measured discharge data and also produces simulated discharge data and then compares them with an r^2 value (measures how well the measured and simulated data matches up and therefore how well the model is working). I'm now at the point where I can begin to calibrate various aspects of the model and try to get my r^2 value as close to 1 as possible and make the discharge curves match. I have to run the model for all 40 years and see what happens (hopefully that works!) and I have to run the model number 2. Model number 2 takes into account solar radiation and topographic shading of the area. Right now I am running the simplest model that only looks at temperature/melt relationship and gives a degree day factor based on this relationship for ice and for snow.

This is an example of the discharge plots that I can now create in MATLAB.

Calibrating the model is interesting because different combinations of the different parameters will yeild the same result. It is important that I match discharge data as well as mass balance data that is simulated and measured. The more outputs I have to match, the number of different combinations of variables decreases and I will be more likely to find some realistic values for those variables.

Regine and Anthony seemed very happy with how well the model seemed to work already with just random and arbitrary values for the variables and the expect that the USGS will be very interested in what I found out. They also expressed interest in creating a little paper out of this project which could then be published! Cool!

I'm also still working in MATLAB and plotting the output from the model in MATLAB. It's been very convienent to learn how to use the model and MATLAB simultaneously. I'm now working on writing scripts that are general enough for anyone to be able to give the name of the data file and then produce a graph with a MATLAB script.

NEXT:
Keep working on MATLAB
Calibrate the model 1 or 2?
Start looking at Mass Balance Data