Hello, is it possible to share the code how you calculated NZavg in the weewx? Did you extend aggregation type with xtypes?
Thanks for reply :) st 29. 3. 2023 v 22:37 odesílatel 'Peter Fletcher' via weewx-development < [email protected]> napsal: > It certainly does depend on what you want to do with the numbers. > > Like you, I have solar panels, and, also like you, I monitor them > separately from my weewx installation. If all you want to do is keep a > check on total (potential) energy influx, then 24-hour averaging and using > the sort of calculation you suggest, will work perfectly well, though it > won't take account of the fact that solar panels are generally tilted and > face in a specific direction (ideally between SE and SW), while most > standard weather station radiation sensors are designed to be pretty much > equally sensitive to radiation coming from anywhere in the sky. OTOH, if > you want to get total energy from daytime-only averages, you just need to > make sure that you have counted how many samples you have, so you haven't > really lost any information. My problem with simple 24-hr averaging is that > if you want to know 'how bright it was' on a past date, and you use simple > averaging, winter days won't get a fair shake, because, even if the sun was > shining out of a clear sky all day, there will be a lot more zeroes > contributing to the average and the average radiation number will be > disproportionately lower than I feel it 'should be'. I suppose that the > question I am asking and answering is: "What was the average radiation > level *during the day*?". I know it was zero at night! > > For UV, I think you are right about showing minutes per day above a > specified level (or perhaps two different ones) being more useful than any > sort of average, though here, too I think there is an argument for > averaging (if that is what you are going to do) only during the day. > > On Tuesday, March 28, 2023 at 3:43:26 AM UTC-4 Cameron D wrote: > >> The obvious question is what you need to do with the numbers. >> I have solar panels and I log the values separately so I don't use weewx >> for that - I got the weather station partly to help understand my PV >> output. The important long-term values to me are total energy over the >> day/month/etc. So, if I was needing to use weewx values of max or mean to >> plot how things were going then I suppose I would go for the 24-hour >> average. The summation of W/m2 over the day scales to the total energy >> generated - assuming your time interval is fixed and every value is >> recorded. So for a 5 minute interval, multiply the W/m2 value by 300 will >> give you J/m2. >> In the same way, because you should have a fixed number of samples per >> day, the 24-hour average also scales to total energy. However, if you only >> use daylight or non-zero values then you are adding another variable and it >> carries less meaning - if total energy is important to you. >> >> As for UV, since I live in skin cancer central, I would be mainly >> interested in the high values. Any average would be pretty useless to me, >> unless it is, for example, an average between 9:00 and 15:00 (or 3 hours >> either side of solar zenith.) A better long-term value might be minutes >> per day above index 10, 11 or 12. >> I was not even sure an arithmetic mean of a UV index was valid, but >> having had a quick look at the derivation of the index, I think it is OK. >> >> On Tuesday, 28 March 2023 at 12:37:18 am UTC+10 Peter Fletcher wrote: >> >>> I'm trying to start a discussion - not an argument! The fact that no-one >>> has come up with a way of displaying historic radiation readings that a >>> consensus of weather experts thinks is better than a simple average >>> strongly suggests either that no-one thinks that the issue is that >>> important, or that there is no one right answer - probably a bit of both. >>> You can and should use whatever approach is most meaningful for you. In >>> fairness, however, your temperature analogy really does not fly - maximum >>> daily temperatures correlate much better with mean temperatures that is >>> true for radiation values, but max temps are independently more 'important' >>> than max radiation values. This is, of course, partly because it is very >>> rare for a max temp to be a single isolated value in the way a max >>> radiation reading may frequently be. >>> >>> I have switched my annual charts of both UV and Solar Radiation to show >>> 'daytime averages', as previously described. I have attached images of both >>> pairs of charts - 'old' uses simple averaging; 'new' uses daytime >>> averaging. The maximum values are substantially higher in the latter, but >>> the overall patterns are not hugely different. The higher maxima 'feel' >>> better to me, but I certainly would not go to the wall for 'my' way of >>> doing things. >>> On Sunday, March 26, 2023 at 11:33:09 PM UTC-4 [email protected] >>> wrote: >>> >>>> Where I live, with the hardware I use, in my understanding, it is >>>> useful: in addition to the information how much energy from solar radiation >>>> your location got over the day, you can tell if was clear at least for some >>>> time that day, or not. So if you say "where I live, fairly high spikes on >>>> otherwise cloudy days are common, and days with light to moderate cloud >>>> cover with significantly lower maxima are also fairly common" that's just >>>> the point: that's the extra information you get. The fact that you know >>>> that because you live there is proven with data and if your station is on >>>> the internet, everyone can know. >>>> What would you reply to me, if I said: "I not convinced daily maxima >>>> are particularly useful for temperature. At least where I live, fairly high >>>> maxima on otherwise pretty cold days are common, and days with moderate >>>> averages, and maxima not significantly above average, are also fairly >>>> common"? Probably you'd say: "That's different", which is true, because >>>> radiation changes are very like to be more radical than temerature changes >>>> often, but it is not so much different one might think. >>>> >>>> Peter Fletcher schrieb am Sonntag, 26. März 2023 um 22:32:13 UTC+2: >>>> >>>>> I'm not convinced that daily maxima are particularly useful for solar >>>>> radiation. At least where I live, fairly high spikes on otherwise cloudy >>>>> days are common, and days with light to moderate cloud cover with >>>>> significantly lower maxima are also fairly common. Simple averages are, at >>>>> least, somewhat meaningful, and I don't think showing the daily maxima >>>>> adds >>>>> anything to them. Only counting as maxima values that are sustained for >>>>> more than a specified time might make them more so. >>>>> >>>>> On Tuesday, March 21, 2023 at 1:16:48 AM UTC-4 [email protected] >>>>> wrote: >>>>> >>>>>> For myself, I found that for a yearly chart, using a bar chart with >>>>>> the daily averages, and a crosshair to display the daily maximum, a >>>>>> comprehensive way to display solar readings. >>>>>> >>>>>> Peter Fletcher schrieb am Donnerstag, 16. März 2023 um 00:29:26 UTC+1: >>>>>> >>>>>>> In order to look at different ways of presenting solar and UV >>>>>>> radiation data, I dumped the contents of weewx.sdb to a csv file and >>>>>>> used >>>>>>> Excel to manipulate and chart the relevant data. The attached charts >>>>>>> show >>>>>>> daily averages for solar and UV radiation for four-month summer and >>>>>>> winter >>>>>>> periods in 2021 and 2021/22. More (probably 'simple') averaging would >>>>>>> probably be done in producing yearly charts for a website, but I >>>>>>> thought it >>>>>>> helpful to get a somewhat more granular picture of the processed data. >>>>>>> For >>>>>>> all the charts and both types of data, 'Avg ...' uses the current >>>>>>> calculation (simple averaging of all readings for the 24 hr day), 'NZ >>>>>>> Avg >>>>>>> ...' represents the average of all non-zero readings acquired during the >>>>>>> 24hr day, and 'Day Avg ...' represents the average of all readings >>>>>>> (including any zeroes) recorded between sunrise and sunset (calculated >>>>>>> for >>>>>>> my location and the date by the standard NOAA method). >>>>>>> >>>>>>> For solar radiation, in both seasons, the non-zero and daytime >>>>>>> averaging methods produce almost identical results (there are only a few >>>>>>> places where the two lines do not coincide), and the numbers generated >>>>>>> are >>>>>>> a bit more than 1.6 times the simple average numbers in the summer and >>>>>>> well >>>>>>> over twice the simple average numbers in the winter. This additional >>>>>>> seasonal difference is, of course, a result of the non-zero winter >>>>>>> averages >>>>>>> not being 'diluted' by the zero values from the longer nights. The >>>>>>> results >>>>>>> of the two more complex averaging methods make more sense to me as a >>>>>>> way to >>>>>>> present solar radiation readings for long time-periods. Non-zero >>>>>>> averaging >>>>>>> is computationally simpler and would probably be my preferred way to go. >>>>>>> >>>>>>> For UV radiation, the picture is rather different. Here, the simple >>>>>>> average numbers are again lowest, but the other two averaging methods >>>>>>> produce substantially different results, with non-zero averaging giving >>>>>>> (particularly in the winter) results up to three times those generated >>>>>>> by >>>>>>> non-zero averaging. Here, I think daytime averaging makes more sense. >>>>>>> As I >>>>>>> indicated in my earlier post in this thread, I thought that non-zero >>>>>>> averaging for UV radiation was likely to produce 'average' results that >>>>>>> were distorted by periods of sunshine during an otherwise cloudy day, >>>>>>> and I >>>>>>> believe that this is a substantial contributor to what is happening >>>>>>> here. >>>>>>> Assuming, however, that stations which have UV sensors generally also >>>>>>> have >>>>>>> solar radiation sensors, it might be computationally simpler to average >>>>>>> UV >>>>>>> radiation readings if/when the accompanying solar radiation values are >>>>>>> non-zero. >>>>>>> >>>>>>> Any thoughts or comments? >>>>>>> >>>>>>> On Saturday, March 11, 2023 at 4:05:18 PM UTC-5 Peter Fletcher wrote: >>>>>>> >>>>>>>> When looking at some of my 'yearly' charts (see >>>>>>>> https://fletchers-uk.com/weather/index.html), the other day, I was >>>>>>>> struck by how low the 'peaks' in the Solar Radiation and UV graphs >>>>>>>> were. >>>>>>>> On a sunny day in the summer (yes - we do have such days in >>>>>>>> Buffalo!), I >>>>>>>> typically see Solar Radiation numbers above 900 and UV values above >>>>>>>> 7 >>>>>>>> for at least a couple of hours around solar noon, but the peaks of >>>>>>>> the >>>>>>>> yearly graphs barely exceed 325 and 2, respectively. A (very) >>>>>>>> little >>>>>>>> thought revealed the reason for this - the longer term charts >>>>>>>> average >>>>>>>> the raw values recorded over periods of more than 24 hours (a week, >>>>>>>> in >>>>>>>> my case), so the averages displayed on the charts include a large >>>>>>>> number >>>>>>>> of entirely predictable nocturnal zero readings. In the depths of a >>>>>>>> Buffalo winter, it is dark for 15 hours out of the 24, and even in >>>>>>>> high >>>>>>>> summer here it is dark for a bit less than 9 hours out of 24. >>>>>>>> >>>>>>>> 'Straight' averages are easy to compute, and make reasonably good >>>>>>>> sense >>>>>>>> for displaying the majority of weather-related measurements, which >>>>>>>> typically have no particular diurnal pattern - or, at least, not >>>>>>>> such an >>>>>>>> extreme one - but it doesn't seem totally to make sense to use them >>>>>>>> when >>>>>>>> you know in advance that there is such a pattern. OTOH, it clearly >>>>>>>> wouldn't be very useful just to record and display the daily peak >>>>>>>> values >>>>>>>> for these measurements, since that would treat otherwise cloudy >>>>>>>> days >>>>>>>> during which the sun appeared through the clouds for ten minutes >>>>>>>> around >>>>>>>> noon in the same way as days on which the sun shone out of a >>>>>>>> cloudless >>>>>>>> sky from dawn to dusk. Some averaging is needed. >>>>>>>> >>>>>>>> One possibility that might produce (IMHO) more meaningful results >>>>>>>> is >>>>>>>> 'non-zero averaging' - do not count zero values in computing the >>>>>>>> average. Solar Radiation rarely reads as zero during the day, so >>>>>>>> the >>>>>>>> results of this calculation should correspond reasonably well to a >>>>>>>> daytime-only average. Daytime UV readings, OTOH, are frequently >>>>>>>> zero if >>>>>>>> it is reasonably heavily overcast, so 'non-zero averaging' would >>>>>>>> produce >>>>>>>> misleadingly high 'average' values on days with variable cloud >>>>>>>> cover. >>>>>>>> >>>>>>>> A second, and, I think, better, possibility would be to explicitly >>>>>>>> record and average only daytime values for both readings - defining >>>>>>>> daytime as being between sunrise and sunset for the date and the >>>>>>>> station's location. >>>>>>>> >>>>>>>> It might also be of interest to record and display the average >>>>>>>> daily >>>>>>>> number of minutes/hours for which the reading exceeded a particular >>>>>>>> threshold, and/or the level reached for at least a certain length >>>>>>>> of >>>>>>>> time - the thresholds in each case being determined in advance - >>>>>>>> but >>>>>>>> computing these results on the fly would likely be more >>>>>>>> challenging. >>>>>>>> >>>>>>>> I am going to be playing with implementing these ideas over time, >>>>>>>> but I >>>>>>>> would like to hear others' thoughts. >>>>>>>> >>>>>>>> -- >>>>>>>> >>>>>>>> Peter R. Fletcher <[email protected]> >>>>>>>> Home Page - https://pfletch.fletchers-uk.com >>>>>>>> >>>>>>>> -- > You received this message because you are subscribed to the Google Groups > "weewx-development" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-development/fe2f240a-6aef-4536-98e6-7a5f1a573508n%40googlegroups.com > <https://groups.google.com/d/msgid/weewx-development/fe2f240a-6aef-4536-98e6-7a5f1a573508n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "weewx-development" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-development/CAPXATBUESWSv1tqJ6e8YQubg2stoLn0o%2BLFdObWVtzj0MGmcGQ%40mail.gmail.com.
