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Questions about Date various derivatives applied to

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sfws
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Joined: Fri 27 Jul 2012 11:29 am
Weather Station: Combination Mix of FO stations
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Questions about Date various derivatives applied to

Post by sfws »

In other posts Freddie contributed:
freddie wrote:
Sat 28 Mar 2020 6:51 pm
Snow day runs from midnight to midnight (UTC)
freddie wrote:
Sat 28 Mar 2020 8:20 pm
It's the same for days of hail and gale too. Fog is similar to snow depth, in that it is the existence of fog (visibility less than 1000m) at 0900 GMT that makes a "fog day". Snow depth and fog day are measured at an instant in time (i.e. 0900 UTC) whereas all the other elements are measured over a period of time.
In fact, for temperatures it is complicated too. The definition of maximum temperature is that it is attributed to the date on which your meteorological day begins - which sounds reasonable. For minimum temperature, however, it is attributed to the date on which your meteorological day ends. So Cumulus doesn't have it strictly correct. For example - my weather station (via Cumulus) reported at 0900 this morning that the maximum temperature was 13.1, and the minimum temperature was -1.2. Following the definitive rules, the maximum temperature is attributed to the 27th March, but the minimum is attributed to the 28th March. But in the Cumulus "dayfile" they will both be attributed to the 27th. As maximum temperature typically occurs mid afternoon and minimum temperature around sunrise, then you can see why this strange-sounding rule originated.
No, rain days are 0900 to 0900 (UTC). The date the rainfall total is attributed to is the date at the start of the meteorological day - this Cumulus does get correct.
So let me see if I have got this right.
Let assume we are recording at 9am UTC on day 2, what has happened in last 24 hours (since 9am UTC on day 1).
* we record a snow day, or hail day, if there was any snow, hail, (respectively), prior to last midnight
* we record a gale day if there was any wind greater than 47 mph (21 m per second, 41 knots), prior to last midnight
* we record snow depth as at that instant in time (9am UTC on day 2)
* we record fog (visibility less than 1000m) as at that instant in time (9am UTC on day 2)
* we record Maximum temperature, max/min humidity, max wind gust, windrun, min/max pressure, etc. and attribute to day 1
* we record minimum temperature and attribute that to day 2, but nothing else is attributed to day 2?

My script (written for Cumulus 1) for transferring all these weather derivatives to my daily_summary database table actually has 2 rows (day 0 and day 1) of the dayfile.txt log file in PHP variables at same time, so it is easy for me to store correct values to day 1 in the database table as I have access to last 48 hours. I didn't design it for this, the read ahead was so I know when the last day is reached before I process it, and allow time for Cumulus to complete all its rollover actions as by experience I found it initiates the external batch in advance of writing backup files and other file actions.

freddie
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Re: Questions about Date various derivatives applied to

Post by freddie »

sfws wrote:
Sun 29 Mar 2020 7:52 pm
In other posts Freddie contributed:
freddie wrote:
Sat 28 Mar 2020 6:51 pm
Snow day runs from midnight to midnight (UTC)
freddie wrote:
Sat 28 Mar 2020 8:20 pm
It's the same for days of hail and gale too. Fog is similar to snow depth, in that it is the existence of fog (visibility less than 1000m) at 0900 GMT that makes a "fog day". Snow depth and fog day are measured at an instant in time (i.e. 0900 UTC) whereas all the other elements are measured over a period of time.
In fact, for temperatures it is complicated too. The definition of maximum temperature is that it is attributed to the date on which your meteorological day begins - which sounds reasonable. For minimum temperature, however, it is attributed to the date on which your meteorological day ends. So Cumulus doesn't have it strictly correct. For example - my weather station (via Cumulus) reported at 0900 this morning that the maximum temperature was 13.1, and the minimum temperature was -1.2. Following the definitive rules, the maximum temperature is attributed to the 27th March, but the minimum is attributed to the 28th March. But in the Cumulus "dayfile" they will both be attributed to the 27th. As maximum temperature typically occurs mid afternoon and minimum temperature around sunrise, then you can see why this strange-sounding rule originated.
No, rain days are 0900 to 0900 (UTC). The date the rainfall total is attributed to is the date at the start of the meteorological day - this Cumulus does get correct.
So let me see if I have got this right.
Let assume we are recording at 9am UTC on day 2, what has happened in last 24 hours (since 9am UTC on day 1).
* we record a snow day, or hail day, if there was any snow, hail, (respectively), prior to last midnight
* we record a gale day if there was any wind greater than 47 mph (21 m per second, 41 knots), prior to last midnight
* we record snow depth as at that instant in time (9am UTC on day 2)
* we record fog (visibility less than 1000m) as at that instant in time (9am UTC on day 2)
* we record Maximum temperature, max/min humidity, max wind gust, windrun, min/max pressure, etc. and attribute to day 1
* we record minimum temperature and attribute that to day 2, but nothing else is attributed to day 2?
You should remember that the definitions (e.g attribution of extreme temperature to date) come from the era before there was continuous electronic measurement of meteorological elements. Therefore, elements such as maximum and minimum relative humidity were not recorded (RH was manually calculated with a slide rule from the dry bulb and wet bulb thermometers). The same applies for pressure extremes and wind run. So I think the definitive list of recordings at 0900 UTC on day 2 is:
  • 0900-0900 Maximum temperature (attributed to day 1)
  • 0900-0900 Minimum temperature (attributed to day 2)
  • 0900-0900 Rainfall (attributed to day 1)
  • 0900 Snow depth (attributed to day 2)
  • 0900 Fog (attributed to day 2)
  • 0900 Mean Sea Level pressure
  • 0000-2359 Day of snow (attributed to date on which the phenomena occurred)
  • 0000-2359 Day of hail (attributed to date on which the phenomena occurred)
  • 0000-2359 Day of gale (mean wind speed of >=34 knots (39 mph, 17 m/s) (attributed to date on which the phenomena occurred) **N.B: gusts are irrelevant
All other element extremes/summations you mentioned were simply not recorded, as they have emerged during the "AWS age" and are not comparable with anything from the long-period climatological statistics.

There are other elements not on this list from the pre-AWS period. They include:
  • 1500-0900 Grass minimum temperature (a minimum temperature, so attributed to this day)
  • 1500-0900 Concrete minimum temperature (a minimum temperature, so attributed to this day)
  • 0900 10cm depth soil temperature (temperature at in instant in time, so attributed to this day)
  • 0900 30cm depth soil temperature (temperature at in instant in time, so attributed to this day)
  • 0900 50cm depth soil temperature (temperature at in instant in time, so attributed to this day)
  • Sunrise-Sunset (previous day) total sunshine hours (attributed to the previous day)
  • State of ground (bare patch of soil) - observed at 0900 so attributed to this day
  • State of concrete - observed at 0900 so attributed to this day
  • 0000-2359 Day in which thunder was heard (attributed to the date of the occurrence)
There may be something that I have forgotten (it is quite late and I'm a bit tired) but I think I have captured the lot here. You say you have looked at my spreadsheets before - well, it is all in there (except for 0900 pressure - which I should really record too).
Freddie
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sfws
Posts: 1004
Joined: Fri 27 Jul 2012 11:29 am
Weather Station: Combination Mix of FO stations
Operating System: R Pi OS

Re: Questions about Date various derivatives applied to

Post by sfws »

Thank you very much, Freddie.
freddie wrote:
Mon 30 Mar 2020 12:27 am
0900-0900 Maximum temperature (attributed to day 1)
0900-0900 Minimum temperature (attributed to day 2)
That fits how I did my design, my database daily_summary table has all temperatures attributed to correct day.

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