radiation and uv graph query

[Ian Prescott]

Hi all

I was researching some of my weather history the other day when I stumbled on strange radiation and uv graphs in weekly, monthly and yearly pages.

so current data graph shows day 18/08/19 (on the left side of night)

UV touched 8

Radiation touched 1400

so week data graph shows day 18/08/19

UV touched 7

Radiation touched 1200

so monthly data graph shows day 18/08/19

UV touched 5.5  

Radiation just over 1000

so yearly data graph shows trend

UV almost 2  

Radiation just over 300

So UV and Radiation values appear to decrease as the time view increases.

Is this right? or have I messed something up?

I have attached weewx.conf and image files.

thanks

[Andrew Milner]

I would guess they are averaged values - whereas perhaps you would prefer to plot maximum values.

[Liz]

On Mon, 19 Aug 2019 06:16:13 -0700 (PDT)
Andrew Milner <andrew.s...@gmail.com> wrote:

> I would guess they are averaged values - whereas perhaps you would
> prefer to plot maximum values.
>

They are average values.

Liz

[gjr80]

Have a look in the relevant skin.conf under [ImageGenerator] and then look at the aggregate_type and aggregate_interval config options under each [[ ]] stanza. By default the plots for week and longer periods plot an average (set by aggregate_type config option) calculated over the aggregate_interval period. For week this is a one hour average, month is a three hour average and year is a one day average (day plots plots do no averaging). Consequently week, month and year plots of data such as UV and radiation can appear to display low values.

One of the main reasons for this approach is to avoid excessive processor loads/times when generating large plots. For a 5 minute archive period one day consists of 288 data points, for a one year plot this would be over 100 000 data points if there was not some sort of aggregation being used. As mentioned you can change aggregate_type to plot the maximum value if you want a more realistic plot. Have a read of The image generator section in the Customization Guide (http://weewx.com/docs/customizing.htm#image_generator)

Gary

[Ian Prescott]

Thanks for the explanation, I will have a read of the image generator section.

But I am happy that I haven't messed something up.

Ian

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