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Heat/cold degree days and Chill hours: Difference between revisions
Heat/cold degree days and Chill hours (view source)
Revision as of 15:05, 7 September 2013
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This measure is sometimes called ''Growing Degree Days'', because it relates to plants or insects rather than heating systems, but that seems a strange labelling because growth in most plants and insects responds to warmth, although some seeds need a period of chilling to stimulate germination and as described below some fruit needs chilling to promote development. However, [http://sandaysoft.com/forum/tracker.php?p=1&t=262| enhancement request #262] reports a different definition of ''Growing Degree Days'' based on summing daily: ((MaxTemp - MinTemp)/2 - BaseTemp) for all days where the value is positive (negative values are not subtracted).
=== Calculation of Chill Hours ===
The traditional way of calculating the accumulation of Chill Hours is the number of hours the temperature is below 45 degrees Fahrenheit or 7.5 degrees Celsius for the period of 1st October to 30th April in the Northern Hemisphere. One
On Cumulus that threshold, and start date are the default, so you simply observe the reported value at the relevant time on 30 April/1 May. The current figure is viewable on the 'This Year' screen accessed from the View menu (only when the current year is selected), stored in [[today.ini]], and is available via web tag <#chillhours> to be added to a web page template of your design. Should you miss checking the reported value on 1 May, then for a few days, you can look in the backup sub-folder for the necessary archived today.ini. In the current version of Cumulus, a new archive of the data sub-folder is taken just after each rollover.
[[User:Sfws|Sfws]] 10:53, 1 December 2012 (UTC) (with thanks to Randy who raised [http://sandaysoft.com/forum/tracker.php?p=1&t=117| Enhancement Request #117] and supplied some of the above text)
=== Air Frost ===
However, the way it can be configured on Cumulus will allow you to track air frost (defined as when temperature at the standard measuring height is below the freezing point for water) hours, ground frost (temperature close to ground level is below freezing) hours or any other measure being below the threshold parameter. Sometimes the term 'grass frost' is used for whan the air temperature goes below 4 degrees Celsius, it roughly corresponds to when grass looks white due to frozen dew (water is more dense below 4 degress than above 4 degrees so the cold moisture falls onto the grass).
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