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Heat/cold degree days and Chill hours: Difference between revisions
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Heat/cold degree days and Chill hours (view source)
Revision as of 15:28, 11 June 2021
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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, [https://cumulus.hosiene.co.uk/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). | 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, [https://cumulus.hosiene.co.uk/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 === | === 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 degrees Celsius for the period of 1st October to 30th April in the Northern Hemisphere | The traditional way of calculating the accumulation of Chill Hours is the number of hours the temperature is below 45 degrees Fahrenheit or 7 degrees Celsius for the period of 1st October to 30th April in the Northern Hemisphere. | ||
On Cumulus that threshold | From MX 3.12.0, the default start month is April in Southern hemisphere and October in Northern hemisphere. Earlier releases had start month of October regardless of the latitude. There are other changes in 3.12.0 that improve the way that Cumulus software processes Chill Hours. | ||
One applicability is to stone and seed fruit as their exposure to low temperatures during the winter months will have a significant effect on the following harvest. Too few cold hours can result in poor quality and quantity of the crop. Fruit tree varieties prefer a Chill Hour rating from about 200 hours to around 1500 hours. | |||
On Cumulus that threshold is the default, so you simply observe the reported value at the relevant time on 30 April/1 May in Northern hemisphere. | |||
To use a different threshold add ''ChillHourThreshold=x.x'' to [[Cumulus.ini_(Cumulus_1)#Section:_Station| station section in Cumulus.ini_(Cumulus_1)]] where x.x is the temperature you want in your normal Cumulus temperature units. Use ''ChillHourSeasonStart=mm'' in [[Cumulus.ini_(Cumulus_1)#Section:_Station| station section in Cumulus.ini_(Cumulus_1)]] where mm represents month number (1=January, 12=December) to change the season start. 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 seasonal or longer period 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 final 1.9.4 version of Cumulus 1, a new archive of the data sub-folder is taken just after each rollover, but note that Chill hours are counted in Cumulus by calendar day (therefore some interpolation is needed if your rollover is 9am/10am). From release 3.10.0, the backup reverted to at end of day as in early Cumulus 1 software versions. | |||
[[User:Sfws|Sfws]] 10:53, 1 December 2012 (UTC) (with thanks to Randy who raised [https://cumulus.hosiene.co.uk/tracker.php?p=1&t=117| Enhancement Request #117] and supplied some of the above text) | [[User:Sfws|Sfws]] 10:53, 1 December 2012 (UTC) (with thanks to Randy who raised [https://cumulus.hosiene.co.uk/tracker.php?p=1&t=117| Enhancement Request #117] and supplied some of the above text) | ||
Updated for MX 15:28, 11 June 2021 (UTC) [[User:Sfws|Sfws]] ([[User talk:Sfws|talk]]) | |||
=== Air Frost === | === 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). | 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). | ||
To see the number of '''Air Frost days''', use the View menu to select 'This Month', 'This Year' or 'This Period' and choose the precise period of interest using the drop down selectors. (As at build 1058, there are no web tags to give air frost day counts). | To see, in the legacy Cumulus 1 software only, number of '''Air Frost days''', use the View menu to select 'This Month', 'This Year' or 'This Period' and choose the precise period of interest using the drop down selectors. (As at build 1058, there are no web tags to give air frost day counts). | ||
The Chill hours web tag with a threshold of 0 degrees Celsius (32 Fahrenheit) will give '''air frost hours''' since the starting month. | The Chill hours web tag with a threshold of 0 degrees Celsius (32 Fahrenheit) will give '''air frost hours''' since the starting month. | ||
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=Setting the threshold= | =Setting the threshold= | ||
== Heat and Cold Degree Days for NOAA reports == | == Heat and Cold Degree Days for NOAA reports == | ||
=== CAUTION: Think carefully, about what threshold to use === | ===MX Settings=== | ||
Cumulus stores your selected threshold values in the '''cumulus.ini''' file within the folder containing your Cumulus software (see [[Cumulus. | |||
Please see [[Cumulus.ini#Thresholds]] for information about setting thresholds in latest MX release. No screenshot is included, as there are 2 different ways in which the setting screens can now be displayed, so to show one or both would be muddling. | |||
===Legacy Software=== | |||
[[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. | |||
==== CAUTION: Think carefully, about what threshold to use ==== | |||
Cumulus stores your selected threshold values in the '''cumulus.ini''' file within the folder containing your Cumulus software (see [[Cumulus.ini_(Cumulus_1)#Section:_NOAA]]). | |||
===General Explanation=== | |||
It allows you to specify, in the units you have selected to use in your implementation of Cumulus, the two thresholds (they do not have to be the same, although they are in the picture that shows the thresholds traditionally used in the UK in the pre-computer age of standard reference look-up tables). Since it introduced electronic processing in the 1960s, the UK Meteorological office has used 22 Celsius for Cold degree days, and used 15.5 Celsius for Heat degree days. | |||
'''If you later change the threshold, you will have inconsistencies on your reports:''' | '''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 degree day counts based on the new threshold for the minute by minute interrogations of the weather station. | * The report will quote the new threshold, but only ''after the time'' you changed the threshold, will Cumulus calculate the degree day counts based on the new threshold for the minute by minute interrogations of the weather station. | ||
* For the period from ''when you installed'' Cumulus version 1.9.2 (this also applies for any earlier days added by 'create missing' with the new version) until day before changing threshold, the integrated figures as 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 at the time that the figures were stored in the daily summary log. It is therefore not possible to affect these degree days | * For the period from ''when you installed'' Cumulus version 1.9.2 (this also applies for any earlier days added by 'create missing' with the new version) until day before changing threshold, the integrated figures as 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 at the time that the figures were stored in the daily summary log. It is therefore not possible to affect these degree days retrospectively by changing the thresholds. | ||
* For days that were 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. | * For days that were 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. | ||
Cumulus 1.9.2 was available as default version from 5th October 2011, or as beta Build 1004 from 21 July 2011. | Cumulus 1.9.2 was available as default version from 5th October 2011, or as beta Build 1004 from 21 July 2011. | ||
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== Configuring Chill Hours == | == Configuring Chill Hours == | ||
The '''Chill Hours defaults''' are configurable by adding entries to the [Station] section in Cumulus.ini (see [[Cumulus. | |||
The '''Chill Hours defaults''' are configurable by adding entries to the [Station] section in Cumulus.ini file with Cumulus software stopped (see [[Cumulus.ini_(Cumulus_1)#Section:_Station]]): | |||
''ChillHourSeasonStart=10'' | ''ChillHourSeasonStart=10'' | ||
