Rain block - % of monthly rain vs. yearly rain

[Lespius]

Hello,

I think there is a small mistake in that block:



Logically, during the month of January, the % of rain should be the same for that month and for the year. We can see that the average is not the same: 68.75mm (January) and 65.05mm (for year to date). Strange, isn't it

Alain

[Jachym]

It seems illogical, but it makes sense.

1-16 Jan - the period is the same

However the year to date average is calculated by using
annual rain /365 * number of days (in this case 16)

Monthly is:
monthly rain / days in month * 16

[Lespius]

OK, understood.
Actually I thought that you were adding the average of day 1 + average of day 2, etc... instead of a linear average. Probably easier.
Have a nice evening

[Jachym]

It would of course be more accurate to use daily average norms, but we dont have normal data in daily intervals for most locations and I guess most of you wont like having to enter 365 numbers for temperature and rain in the Main setup

[Lespius]

Hi Jachym.

I have thought a bit about those numbers. And I have checked. The average numbers that are used to calculate the % are:
> daily (6.3)= the station average and not the normals
> monthly (68.75)= the sum monthtodate of the daily average

So nothing to do with normals. You are using the station average, not the normals, which is the aim of that block.

For the yearly average (65.05), I must say that I don't know where it comes from: neither the normal yearly sum nor the station yearly sum lead to the number used for the % calculation (65.05):
> yearly normal ytd is 1181 (according to the Precipitation Analysis plugin) / 365 * 16 =51.76 mm
> yearly station average ytd is 1149.2/365*16= 50.37mm

you are using 65.05....

So i still believe there is some kind of addition of every previous days and no division by 365 and multiplication by the numbers of days. And that in January the % of monthly average and yearly average should be identical.

Don't you think so?