Friday, April 16, 2010

Hood Initial GIS Analysis

For the past week or so have gone through the years 1987, 1992 and 2005 (the low precip and SWE years). I clipped each year’s band ratio with the .05 threshold value I determined I was going to use to each glacier outline. Upon your suggestion I cliped all three years for each glacier to the 1972 outline as well as all three years for each glacier to the 1984 outline for comparison. The top image is the coverage for each year for the 1972 outline and the the one below it is for the 1984 outline. For both outlines you can see a clear change over time.

I took a look at a couple years in between but I think with the resolution of the landsat it is not going to be feasible to accurate assess annual change. I think for my analysis I should stick to decadal change using the low snow years I have picked. You had mentioned looking at a Cumulative Degree Day approachfor the SNOTEL temp records. Could we figure out a way to look at this on a decadal scale?

You also asked about older outlines for Hood. Yes I do :). I’m going to send you an email with a screen shot of the years I have from the Portland Temporal file. But the last image down here is a comparison between the 1907 outlines and the 2004 ones.

I’m going to try to email around to figure out how to get the Hood debris flow initiation points. I think some people at the highway website may have some because they did a study on it. (I posted the link a few posts ago). If I don’t come up with anything soon I’ll let you know.

I found the average slope for the debris free ice area of each clipped glacier for each year with each outline but I’m getting weird results from Excel when I put in the equation for that column. Could you take a look at the excel file I sent you? For some reason I’m getting negative numbers...

Happy again that Pat will be joining your group this fall.

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