[gradsusr] Confusiong about WEASDSFC, GFS

[Stephen McMillan]

Chris,

If you want to convert amounts in mm to in, you need to divide by 25.4, not
2.54 (or, multiply by the 0.03937 you had in your example).    To go the
other way (in to mm), multiply in. amounts by 25.4.

However, if you are converting mm to in. and using a 10:1 snow-liquid
ratio, then simply dividing the weasdsfc amounts by 2.54 should achieve the
same result as dividing by 25.4 (multiplying by 0.03937) then multiplying
result by 10.  Result would be in inches.

Stephen Mc



On Tue, Sep 29, 2015 at 8:41 AM, Christopher Gilroy <chris.gilroy at gmail.com>
wrote:

> Alright, I have two primary questions, and if the answers are yes to both,
> the follow-up makes no sense to me.
>
> 1.) weasdsfc is water equivalent based in mm, correct?
> 2.) weasdsfc has no "default" liquid:water ratio, correct? A meteorology
> friend of mine said 'typically' 10:1 is a good standard, so I'm unsure if
> the model is based around that or not?
>
> I'm fairly certain I'm correct on #1. I'm unsure on the other 2 though,
> but here's my current situation. If I use the expression below:
>
> 'd
> const((sum(maskout(weasdsfc-weasdsfc(t-1),weasdsfc-weasdsfc(t-1)),t=2,t='%i%')/2.54),
> 0, -u)'
>
> I get an identical looking map as another well known sites 10:1 snow
> accum, in inchs. The confusion part of that equation should be converting
> (/2.54) IN to MM, no?
>
> Now, if on the other hand I do the (if I'm understanding this right)
> "correct" calculation to convert mm to in:
>
> 'd const((sum(maskout(weasdsfc-weasdsfc(t-1),weasdsfc-
> weasdsfc(t-1)),t=2,t='%i%')*0.039370), 0, -u)'
>
> I get very, very, very little snow plotted.
>
> Now, I am using the sflux files instead of the pgrb2.0p25 files, which I
> thought the flux files maybe used different units or something but they
> don't, weasdsfc is still [kg/m^2] which should mean (unless my expression
> is more of a hack than I would have imagine) I should be getting the
> opposite outputs of what each expression is actually producing?
>
> I don't know if I'm missing a parenthesis group somewhere and I'm somehow
> getting an inches, 10:1 snow accum plot with my code by "accident" or what?
> :-/
>
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