FA-70887 / Weather index computation / Member archive

Magnus dew point with ice branch: freezing branch boundary · case 02

Readings at exactly 0 degC are computed with ice constants.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input temperature in degC and RH in percent. RH <= 0 or RH > 100 returns None. Use Magnus constants a=17.62, b=243.12 when T >= 0 and a=22.46, b=272.62 below freezing; g = ln(RH/100) + aT/(b+T); dew/frost point = b*g/(a-g) rounded to 0.01.

Why this case matters

Dew and frost point drive fog, icing and frost forecasts.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
0 C at 50% RH	`-8.16`	`-9.2`	Failed

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