Accumulated Freezing Degree Day Indicator

[rmartz]

In estimating ice thickness, one method suggested by the U.S. Army Corps of Engineers is to use the square root of the Accumulated Freezing Degree Day (AFDD) with a coefficient based on the type of body of water.

AFDD is defined as the consecutive sum of the difference of average daily temperature to freezing, bounded by 0. That is, you advance day-by-day and calculate the difference of the average temperature to freezing... days warmer than freezing decrease the AFDD by the difference, to a minimum of 0, while days colder than freezing increase the AFDD by the same amount.

Based off of this, we could create an indicator that calculates the maximum AFDD per year. This could be used to estimate ice thickness, but it could also be used to show change in ice thickness... for a given body of water, a year with half the maximum AFDD could be expected to have greatest ice coverage 70% as thick.

Challenge would be that maximum AFDD would require advancing from fall into spring and crossing to the new year with a continued sum, which may not be possible with our current indicator design.

[CloudNiner]

That paper is a great find, this would be an excellent indicator to add.

👍

[fungjj92]

Note:
Make sure to add to indicators detail section in docs