I would be very interested in this calculation as well! Unfortunately I am of a limited proficiency when it comes to Python.
As I understand cooling degree days, they reference a temperature mean for the day. Chill hours would be a different subset, and is specifically the amount of time below 45 degrees Fahrenheit. Cooling hours are cumulatively counted between October 1 through February 28 (at least in Texas). A more specific model only counts time with temperatures greater than 32 and less than 45 degrees. Newer models (still being reviewed I believe) have begun subtracting the time below 32 degrees from the cumulative number for a more exact count. Seth, I think you are on the right track. If you could calculate on a daily basis and include that in the summary database, you would then only need to add the summaries together for a selected period. This is the same process used for rain (I think). -Jonathan Z On Tuesday, January 18, 2022 at 6:11:03 PM UTC-6 [email protected] wrote: > What's the difference between chill hours and the existing cooling-days, > except for the value of the base? > > On Tue, Jan 18, 2022 at 3:47 PM Seth Ratner <[email protected]> wrote: > >> Ok, I'm looking at this from a different angle, and was wondering if >> someone knew the "right" way to do this before I go inventing a more >> complicated solution. >> >> For Chill Hours, I just need to add up the time that the temp is below XX >> degrees between two dates. As I understand WeeWX, every database entry has >> the interval length and the average temp for that interval. So in theory I >> can query the DB for the number of entries between two timestamps where the >> temp is below XX, and multiply the number of entries by the interval >> duration (5 minutes default). >> >> However, that would have me doing that query every time I wanted to >> display the value, which might be unnecessary processing power. It would >> also limit my display options. For example, if I wanted a chart to show >> chill hours the same way rain can be shown (with a cumulative line, an >> absolute line, etc), I'd have to come up with a more complicated query. >> >> Which got me thinking, chill hours are somewhat similar to rain, in that >> they are additive. So do I just create a service that gets triggered on an >> archive entry, looks at the temp for that archive entry, and if the temp is >> below the threshold it adds a value to column 'chill_hours' equal to the >> interval duration is? Then instead of inches, I'm using "minutes" as the >> unit of measurement. >> >> And is there any way to influence the daily summary table that would be >> created for this new "chill hours" field? Or do they all have to follow the >> same logic? >> >> Am I going about this the entirely wrong way? Ultimately I'd like to >> create the ability to track the accumulated hours of various custom temp >> ranges, and use that data for charting similar to other existing fields. >> >> Thanks, >> Seth >> >> >> >> >> >> On Saturday, December 25, 2021 at 11:48:43 AM UTC-6 Seth Ratner wrote: >> >>> Hi everyone, >>> >>> I was wondering if anyone had already come up with a way to monitor >>> chill hours (cumulative hours below 45℉) in WeeWx. I'm using Belchertown, >>> and it would be nice to have a readout with Oct-May chill hours, and maybe >>> a chart that shows the per-week and cumulative hours together. >>> >>> Thanks! >>> Seth >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "weewx-user" 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-user/dcff6386-f236-43ab-92e2-c2e0c76acd37n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/weewx-user/dcff6386-f236-43ab-92e2-c2e0c76acd37n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "weewx-user" 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-user/f7932dc4-02de-4d37-bf8a-3d5b000c7a7en%40googlegroups.com.
