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Humidex - Discuss!

From build 3044 the development baton passed to Mark Crossley. Mark has been responsible for all the Builds since. He has made the code available on GitHub. It is Mark's hope that others will join in this development, but at the very least he welcomes your ideas for future developments (see Cumulus MX Development suggestions).

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Re: Humidex - Discuss!

Post by ConligWX »

Personally I probably would not use it, however, this is another feature that could be used by one's who will use/want it.

Why not.... bring it on!
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Re: Humidex - Discuss!

Post by sfws »

mcrossley wrote:
Sun 19 Jul 2020 10:38 am
OK, given the current restrictions with MX, and to match Heat Index and Wind Chill, here's what I'm going to do...

1. Implement as an index - no units, always based on Canadian values, ie no Fahrenheit conversion
2. Implement a cutoff of 10°C, below that it returns the temperature in Celsius (same a heat index and wind chill)
3. Add to dayfile fields for the max value and time
4. Add records/alarms for max value the same as heat index

Let's see how that goes.
I don't use the standard web pages, but I was hoping ...
sfws wrote:
Sun 19 Jul 2020 8:16 am
Humidex is at least valid at temperatures seen in UK in many months of year. ... Weather web pages display Heat Index, which is much more useless in UK.
... (taken together with Humidity Index and Heat Index comparison in my first post) would stimulate a response on whether the 4 points above should get this 5th point or not:

5. On standard web pages, replace the Heat Index (defined only for very high temperatures seen only in a few places) by the Humidex (defined for range of temperatures seen in many nations)

In support, I notice that Heat Index does not appear on a number of third party alternative web pages.
In opposition, I once more quote Steve Loft and his key comment about the standard web pages his wife, Beth, designed:
"They exist because they're our web pages, and they're really only included with Cumulus as examples of how the web tags work. It never occurred to me that most people would simply use the supplied examples instead of creating their own pages!"
Obviously, this quote was made in early days of Cumulus 1, and I have not checked what was actually included on the web pages (or indeed which web pages were available) at that time!

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Re: Humidex - Discuss!

Post by mcrossley »

I will be adding Humidex to the graphs of both the admin interface and the standard web site - which of course means it it is added to the graph data JSON.

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Re: Humidex - Discuss!

Post by HansR »

If still possible: make options which lines to display (and to send data for; of course temperature excluded) because that graph datafile is getting awfully big with lots of data not used/wanted by many! :( (And otherwise I have to implement those parameters/options myself as I do now in CumulusUtils 8-) )
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Re: Humidex - Discuss!

Post by mcrossley »

I guess there are two reasonable options for that; store the choice in cookies (which I don't think the basic web server used for the admin interface supports), or add more options to the Cumulus.ini file.

Another approach is to leave all the derived values hidden by default and just show the basic values on the graph, leaving to user to click to enable anything extra they want to see.

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Re: Humidex - Discuss!

Post by HansR »

mcrossley wrote:
Tue 21 Jul 2020 11:28 am
I guess there are two reasonable options for that; store the choice in cookies (which I don't think the basic web server used for the admin interface supports), or add more options to the Cumulus.ini file.

Another approach is to leave all the derived values hidden by default and just show the basic values on the graph, leaving to user to click to enable anything extra they want to see.
Yes, well, if you leave the derived values hidden just for the user to click and show (storing the choice in cookies), that means the data is still send over. And that is basically the issue. If you just want Temp, Dew point and e.g. Feels Like (how odd, my preference ;) ) you do not want all the other values in the the JSON file. Currently I show 2 days and the file is already larger than 400K, the new data augments it to more than 470K.

I don't mind a bit of regular data transfer, but you need an option to bring it to the level you're prepared for.
So I think it comes down to additional options in CMX, yes/no for any derived value (dew point is also a derived value). Temperature of course is obligatory, otherwise why are we on earth?

So essentially, if you really want to go into the deep, it comes down to the difference between display layer data/acquisition layer. Let's be honest: every website can easily do the derived value calculations in a javascript procedure. It's about distribution of work.

But anyway, from what we have and where I stand, I would go for parameters in Cumulus to switch off the data transfer and the display.
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Re: Humidex - Discuss!

Post by sfws »

HansR wrote:
Tue 21 Jul 2020 12:03 pm
dew point is also a derived value
Actually, that is not a fact.

Some weather stations do supply dew point.

CalculatedDP=... is a parameter in Cumulus.ini https://cumuluswiki.org/a/Cumulus.ini#Section:_Station which determines whether Cumulus calculates it as a derived parameter or it is taken from the station as a source value.
========================================================
mcrossley wrote:
Tue 21 Jul 2020 11:28 am
add more options to the Cumulus.ini file
Actually this would be using options previously in the file; you have forgotten that in Cumulus 1 settings both determined which graphs were uploaded as images for its trends.htm, and also what was plotted on the charts (like temperature) that had multiple lines. If you look at https://cumuluswiki.org/a/Cumulus.ini#Section:_Graphs you will see that C1 let you decide not to plot the Heat index (HIVisible=0 ) that I have been suggesting is not useful.

Moreover, a Cumulus user asked a month ago if there was a ini file selection for what was plotted.
jon_iz wrote:
Tue 23 Jun 2020 9:21 pm
Is it available in an .ini file somewhere and I've missed a setting to enable it?
So ini settings is exactly what is expected by users.
HansR wrote:
Tue 21 Jul 2020 12:03 pm
If you just want Temp, Dew point and e.g. Feels Like (how odd, my preference ;) ) you do not want all the other values in the the JSON file.
As I said in earlier post in this thread, I find dew point useful, (although I convert it to absolute humidity). But I would argue that now I can see Feels Like, I no longer need to see Wind Chill as they are identical in the range where Wind Chill is actually valid.
In viewtopic.php?f=40&t=18042 there is discussion on whether apparent temperature needs to be plotted now that feels like can be plotted.

And of course viewtopic.php?f=14&t=17684&p=136911 talks about removing some lines from plots.

From memory, there were quite a lot of contributions in the forum when Steve Loft asked how he should determine what was plotted in a chart, and I even recall Steve being adamant about how he would implement inside humidity/temperature plotting. Cumulus Users in those days were far more vocal on what they wanted added to Cumulus and how it might work.

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Re: Humidex - Discuss!

Post by HansR »

sfws wrote:
Tue 21 Jul 2020 3:05 pm
HansR wrote:
Tue 21 Jul 2020 12:03 pm
dew point is also a derived value
Actually, that is not a fact.

Some weather stations do supply dew point.
Actually, it is a fact. Even if you get it from the weather station, does not make it a measurement.
It is just calculated by the station.
Would be interesting to compare those two btw.

Your next remark
CalculatedDP=... is a parameter in Cumulus.ini https://cumuluswiki.org/a/Cumulus.ini#Section:_Station which determines whether Cumulus calculates it as a derived parameter or it is taken from the station as a source value.
is related to that. A source value can still be a derived (calculated) value!!
sfws wrote:
Tue 21 Jul 2020 3:05 pm
[...] there is discussion on whether apparent temperature needs to be plotted now that feels like can be plotted.
So, give users a choice.... end of discussion.
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Re: Humidex - Discuss!

Post by Mapantz »

HansR wrote:
Tue 21 Jul 2020 6:10 pm
Actually, it is a fact. Even if you get it from the weather station, does not make it a measurement.
Am I really reading that? You're implying that dew point is not a measurement?? :shock:
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Re: Humidex - Discuss!

Post by HansR »

@Mapantz: Yes, you are really reading that: https://en.m.wikipedia.org/wiki/Dew_poi ... _dew_point

Unless you can point me to a dewpoint sensor with the sensor theory behind it, I stand by the fact the dewpoint is a calculated value (though not like feels like etc...) And not a measurement like temperature.

And to continue on that: evapotranspiration also come from the station (the Davis that is). Now you will really have a very hard time defining that as a measurement.
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Re: Humidex - Discuss!

Post by sfws »

HansR wrote: A source value can still be a derived (calculated) value!!
....
So, give users a choice
...
And not a measurement like temperature.

.... end of discussion.
The context of my post, that the first part of above quote responded to, was Cumulus. In that context, dew point can be supplied to, or derived by, Cumulus, that is factual.

I will add now that Cumulus 1 and MX use different formula to calculate dew point.

The second part of above quote ignored the rest of the post it replied to. My post actually said selection of which lines were plotted was something available in Cumulus 1 by Cumulus.ini settings, and that it should be implemented in MX the same way.

Pursuing your argument in third part of quote, about what is derived in a wider than Cumulus context, temperature is a derived measurement.
For an electronic sensor, temperature will be derived from another property such as resistance.
For a domestic thermometer, it might be derived from the bending of two materials bonded together resulting from their differential expansion, or by expansion of a liquid.
Any temperature scale is derived from one, two, or three, fixed points and calculated (or interpolated) between them.

A hygrometer measures dew point, just as a thermometer measures temperature.

It now seems appropriate to move to your final quoted words.

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Re: Humidex - Discuss!

Post by HansR »

@sfws: First important to note that I reacted to Mapantz who did not believe he was reading something.

But you say things which require some reaction in this context.
sfws wrote:
Wed 22 Jul 2020 5:22 am
The context of my post, that the first part of above quote responded to, was Cumulus. In that context, dew point can be supplied to, or derived by, Cumulus, that was my fact.
It is important to make a difference between measurements and derived values. Therefore what you state as fact (the origin of the value for the dew point) may be true: it either originates in Cumulus or in the weather station. But the origin is irrelevant: there is no dew point measurement.
sfws wrote:
Wed 22 Jul 2020 5:22 am
A hygrometer measures dew point, just as a thermometer measures temperature.
Now I am the one asking whether I am really reading this. A Hygrometer measures relative humidity. If you are saying RH and DP are the same, and if you really are saying (a bit before this quote) temperature is a derived measurement, we are done talking. Because than there is no measurement at all. Everything is derived. Sure...

Anyway, for a good mutual understanding it is important to make a difference between measurements and calculated values. In the class of calculated values one should make a difference between the theoretical values which are not measured directly (like DP) and (very complex) numbers which are invented along the road. Like Feels Like, Evapotranspiration etc... (and for that matter: pwsFWI) This last class may be useful to many, but they are definitely not measurements - no matter their origin - neither do they belong to the standard thermodynamic theory behind meteorology.
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Re: Humidex - Discuss!

Post by Mapantz »

sfws is absolutely correct; hygrometers are used to measure dew point.

Calculation or not, If you don't think dew point is a measurement, then you have a serious misunderstanding of the basics of thermodynamics.
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Re: Humidex - Discuss!

Post by HansR »

Living apart together in different worlds ¯\_(ツ)_/¯

EDIT: You are probably referring to the Dewpoint Hygrometer which is definitely not the sensor mounted in the weather stations CMX is using. Those measure the RH.
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Re: Humidex - Discuss!

Post by freddie »

In meteorology, hygrometers are used to measure the amount of water vapour in the air. Dew point is derived from this measurement, using other factors such as air temperature and air pressure. In the context of a PWS, dew point is definitely a derived quantity. The pertinent measurements made by a PWS are air temperature, air pressure and relative humidity. Dew point is derived from these three measurements.
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