Re: Heat sum & growing season
Posted: Thu 01 Apr 2021 4:58 am
@beteljuice: actually aren't all charts timeseries?
Only this one is per year.
Only this one is per year.
Support forum for Cumulus weather station software
https://cumulus.hosiene.co.uk/
I looked at several definitions and they all use (Max + Min) / 2Hans wrote:... the difference between the integral average and the estimator can be quite large (up to two degrees) so if you can avoid it don't use it.
That is because the UK did not take the leap into the future and remains with ancient estimatorsbeteljuice wrote: ↑Thu 01 Apr 2021 8:54 am I looked at several definitions and they all use (Max + Min) / 2
It is also a Wiki, so maybe it should be noted that it is ancient.beteljuice wrote: ↑Thu 01 Apr 2021 8:54 am Remember this is a 'reference' and it would have been created long before mean samples were easy to do.
Had to look that one up. I disagree there as well, that is not what I am doing.
GoodHad to look that one up.
Quite correct, it was misappliedI disagree there as well, that is not what I am doing.
That remains the way the WMO defines average temperature, and therefore the way that all international comparisons are made.beteljuice wrote: ↑Thu 01 Apr 2021 8:54 am I looked at several definitions and they all use (Max + Min) / 2
Sorry I really do not understand this line of argumentation. The definition of the GDD is given as the integral of the temperature deviation of the daily average Td relative to some temperature Tbase. Then they come up withbeteljuice wrote: ↑Thu 01 Apr 2021 2:06 pm ... but that means you accepted the definition in order to draw a conclusion
... so why do you want to re-define GDD in such a way as all reference tables would have to be re-written ?
This apparently leads you to interpret this as a definition rather than an estimator of the integral. And that is wrong.A simpler, approximately equivalent formulation
A modern farmer works with computers and takes calculations produced buy their own weather stations.[...]a heuristic tool in phenology. GDD are a measure of heat accumulation used by horticulturists, gardeners, and farmers to predict plant and animal development rates such as the date that a flower will bloom, an insect will emerge from dormancy, or a crop will reach maturity.
Hmm, I would argue that is exactly what they do!
I did read the whole thread before making my previous post.
At the start of this thread, you interpreted that Cooling degree days (temperature and time combined) was the answer.mcrossley wrote: ↑Mon 29 Mar 2021 4:05 pm Set the Cooling threshold to 5C, then Cooling Degree Days becomes your Growing Degree Days.
For MX (while left running) calculation of degree days is based on tracking, during each day, the duration that the temperature is above a threshold. Yet the above quote is asking to track the number of days the average temperature is above the threshold. This is the reason why your first answer might not work.Pes wrote: ↑Wed 31 Mar 2021 2:45 pm Effective heat sum is a figure describing the heat accumulated during the growing season.
The effective heat sum is obtained by summing the part that exceeds the average temperature of all days + 5 ° C during the summer. - Degree days
Different plants require different amounts of effective heat to grow.
If the effective heat sum is more than 600 degrees (or degree days, ° Cvrk), trees will grow.
Pes wrote: ↑Mon 29 Mar 2021 5:39 pm The site has charts of heat accumulation and heat sum for each year. I calculate them with an excel program from the average daily temperature. I compare years with each other like this. Heat sum graphics link https://jussilanet.com/tehotemp.htm and heat buildup graphics link https://jussilanet.com/sumheat.htm. Is it possible in the future to get cmx to run these graphics?
From those posts by the originator, it seems that average temperature is indeed the only criteria. As the graphics plotted this on a yearly basis, the thread moved on to arguing how to define average temperature. Mark, you will remember an early modification you made to the NOAA reports was to replace their use of the WMO average (on (max-min)/2 basis) with the "integrated average" Cumulus calculates.
Some plants respond to temperature, some to light conditions, some to moisture levels, but the information I have seen, always quotes this in respect to day by day, not minute by minute (or second by second).
This proves a plant responds to temperature fluctuations. So you are partly right, growth can vary depending on current temperature. But a plant does not decide to pop out of the ground, or produce a bud based on a spot temperature, these responses take time to action. Heat may help crops to ripen, but I have seen no evidence that minute to minute temperature variation is a factor.changes in the ambient temperature can be quickly detected by cell organelles, triggering specific pathways of biochemical and molecular responses in each of these cell compartments and making up an integrated cell response to temperature changes.
My previous reply, was to support this WMO definition of average temperature. I argued, this topic is about growing season, and that is defined in terms of days when plants can grow, and days when they cannot grow. Like beteljuice, I see that formula used in the scientific studies of how plants grow.beteljuice wrote: ↑Thu 01 Apr 2021 8:54 am ]I looked at several definitions and they all use (Max + Min) / 2
Remember this is a 'reference' and it would have been created long before mean samples were easy to do. If you change the basis of the formula you can't compare with look-up tables or other(s) data.
This quote surely confirms my assertion that the growing season in question is based on a response to daily extremes. There is evidence of a response to extremes in this final quote.The growth and development of plants depend, in part, on the temperature. Shifts in the timing of seasons as a direct result of increases in global average temperatures show that growth and development of many plants during spring and summer occur earlier in the year than in the past. To better understand how changes in temperature influence plants, scientists use a well-known tool referred to as Growing Degree Days (GDD) as a way to track the stages of growth and development.
...
GDD are calculated by finding the average of the maximum (Tmax) and minimum (Tmin) daily temperatures and subtracting this value from a base temperature (Tbase) of interest
...
GDD are cumulative–they add up as the year progresses–since they are calculated daily.
One factor to remember is that on a commercial basis, there will be lots of plants growing together (a woodland or crop field generally has say thousands of plants), these provide shelter, and make most (not those on outside edge) of the plants will be less susceptible to minute by minute variations in air temperature (as the plants see a more constant temperature). This is one reason why WHO mean, not integral of individual temperatures is a better measure for the whole field.It has been known since 1939 (Laude et al) that plants' response to heat stress fluctuates between day and night - if you apply heat stress to a plant during the middle of the day, it is much more likely to survive than if you applied the same heat stress at night.