Heat/cold degree days and Chill hours: Difference between revisions

[[File:NOAA_Setup_extract.jpg‎]]The thresholds for '''Heat and Cold Degree days''' are set in the ''NOAA Setup'' option within the ''Configuration'' menu. The picture shows just parts of the setup screen. It allows you to specify the two thresholds in(they thedo units younot have selected to usebe inthe yoursame, implementationalthough ofthey Cumulus.are in Cumulusthe stores your selected threshold valuespicture) in the '''cumulus.ini'''units fileyou withinhave theselected folderto containinguse in your Cumulusimplementation softwareof (see [[Cumulus.ini#Section:_NOAA]]).

=== CAUTION: Think carefully, about what threshold to use. ===

'''If you later change the threshold, you will have inconsistencies on your reports:'''

* The report will quote the new threshold, but only ''after the time'' you changed the threshold, will Cumulus calculate the minutedegree byday minutecounts interrogationsbased ofon the weathernew stationthreshold allow Cumulus to calculatefor the degreeminute dayby countsminute basedinterrogations onof the newweather thresholdstation.

* For the period from ''when you installed'' Cumulus version 1.9.2 (wasthis availablealso asapplies defaultfor versionany fromearlier 5thdays Octoberadded 2011,by or'create asmissing' betawith Build 1004 from 21the Julynew 2011version) until day before changing threshold, the integrated figures alreadyas stored in [[dayfile.txt]] at the end of the meteorological day are quoted in the report. These counts were integrated on a minute-by-minute basis using the thresholds that existed onat eachthe day,time andthat the totalsfigures were stored after rollover in the daily summary log. It is therefore not possible to affect these totalsdegree days restrospectively by changing the thresholds.

* For datadays whichthat waswere logged before you installed version 1.9.2 (or a later build if you missed out that version), there are no degree day figures in dayfile.txt. The values for the NOAA report are calculated simply by comparing the average daily temperature with the current threshold settings, so in this case any change in the threshold does apply retrospectively for those days although the calculation is inconsistent with later days.

* One option is to manually recalculate ''an approximate value'' for each day simply by comparing the average daily temperature with the current threshold settings, making any consequent edits directly onin stored files containing past reports. For each degree (° C or ° F) below/above the threshold of the average daily temperature, it is accounted asadd/subtract 1 degree-day from the daily figure previously recorded.

* The preferred option uses the View menu in Cumulus and the selection to generate new NOAA reports for a month (or year). The new report will ''not be consistent with the latest thresholds'' unless you have ''deleted all the 'pre-threshold change' values'' stored on 'dayfile.txt', but there is an option to save the new report (overwriting any previous one if you use the same name). Obviously if you have deleted values, your report will be consistent for the whole month, it will not haveuse integrated totals, but simply an approximation based on the average daily temperature.