Campbell Scientific VisualWeather Software - Manual (Page 31)

VisualWeather
™
Software
• Upper-Lower – Uses both the Upper Temperature Limit
(upperThreshold) and Lower (Base) Temperature (lowerThreshold) to
calculate the GDD. The method of calculation changes based on both the
Temp Values to Use field and the Cutoff Method field as described
below:
o Average Temperature
ƒ None – Not adjusted for upper threshold. Basically the
same as the Simple GDD Method.
ƒ Horizontal – If (Tmean > upperThreshold) then
Tmean = upperThreshold
ƒ Intermediate – If (Tmean > upperThreshold) then
Tmean = Tmean – (Tmean – upperThreshold) * 2
ƒ Vertical – If (Tmean > upperThreshold)
then GDD = 0
The GDD is then calculated as follows:
If (Tmean > lowerThreshold) then
GDD = (Tmean – lowerThreshold) * dataInterval
Else
GDD = 0
o Min/Max Temperature
ƒ None – Not adjusted for upper threshold. Basically the
same as the Simple GDD Method.
ƒ Horizontal – If (Tmax > upperThreshold) then
Tmax = upperThreshold
ƒ Intermediate – If (Tmax > upperThreshold) then
Tmax = Tmax – (Tmax – upperThreshold) * 2
ƒ Vertical – If (Tmax > upperThreshold) then
GDD = 0
If the above calculation causes Tmax to be below Tmin, then
Tmin is set equal to Tmax.
The mean value is calculated from this new Tmax and Tmin:
Tmean = (Tmax + Tmin) / 2
The GDD is then calculated as follows:
If (Tmean > lowerThreshold) then
GDD = (Tmean – lowerThreshold) * dataInterval
Else
GDD = 0
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