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About the Sasse Ridge Snowpack Bar Graph |
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Let me admit that I'm having a hard time making the snowpack bar graph completely self explanatory. See this page also.
The bars for each elevation could be considered virtual snowpits, except that they don't account for melting, settling or compaction of the snow. It's a rather shallow virtual snowpit at that, because it only shows what happened in the last week. The actual conditions, say if warm rain follows the snow, may be quite different than predicted by the model. Also, occasional aberrant sensor values can give very strange results.
Each of the colored segments in the bars on the graph represent snow that has fallen during the time between two data reporting intervals, i.e. two hours. Baring rain that is. See below for how rain is depicted.
Because the temperature may have changed significantly between the two data intervals, each is first processed independently, using the temperature estimated for that interval based on the latest lapse rate from Stampede Pass. Then the snow accumulation for both periods is summed and displayed as a single color on the bars in the graph.
Use the legend to find the date and time that corresponds to the bar segments. The time shown in the legend is the end of the two hour interval. Follow the individual colors across the range of elevations to see where the snow fell.
Periods of no snow: Diagonal black portions of bars represent periods of no snow. The longer the diagonal, the longer the period. These diagonals may (or may not!) represent actual boundaries between layers of snow.
Rain: Rain is depicted at 1/20 the value for snow; just enough to generate a thin colored band, but not enough to significantly distort the total amount of snow shown. It is possible that a very large amount of rain could fall during two data intervals, and the colored band might be tall enough to suggest snow. Look for a marked increase in the height of the band above a certain elevation to see if this might be the case.
Lot’s of little colored bands one above another means that it rained for a longer time. Example: say the bar shows three very thin colored lines one above the other. This suggests that at the elevation represented by the bar, it rained for 3 data periods (two hours each) or 6 hours.
The idea is that by closely studying the graph, you can tell at what elevation the rain turned to snow, and when.
Wet Snow: The solution to the snow density problem has been evolving. The model originally used only the ‘ten to one’ rule. Later it was modified to use 5 inches per tenth for wet snow, and more recently the snow density calculation was replaced with an adjustable power function. More here.
Etc: If data transmission is delayed for a while when it is snowing, then the two data intervals that make up each bar segment may represent a longer period of time, and thus could show significantly more than one might expect for a 2 hour period.
Larry |