Revisit MAGT vs MAAT for thermal ratio computation in ModBerg
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Twas a prescient issue...per MB's feedback:
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A significant issue is the assumption that the mean annual air temperature (MAAT) is equal to mean annual soil surface temperature (MASST) as stated in the assumptions. The current MAAT for Fairbanks, even for the 2010-2039 projections, is colder than 32°F. This suggests that the conditions favor the presence of permafrost. Ground surface conditions have a strong control as to whether a location is a permafrost (depth of thaw problem) or seasonal frost (depth of freeze) location. As we mentioned, this can be addressed with n-factors. N-factors are not perfect, but they offer a better alternative to the assumption that MAAT is equal to MASST. This does not appear to offer a major hurdle in the code. We suggest providing a listing of n-factors and allow those to be included in the calculations. If the estimated MASST is greater than 32°F, then perform a depth of thaw calculation.
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