Growing degree days calculation method citation

[mimas8000]

I'm trying to understand how the growing degree day function gdd(tmax, tmin, tbase, tbase_max) works. Can you add a citation that details the calculation method to your documentation? The pollen gdd function gives me a little different result than some other methods e.g. "single triangle method" as described in the following citation.

• Zalom, F.G., Goodell, P.B., Wilson, L.T., Barnett, W.W. and Bentley, W.J., 1983. Degree-Days, the Calculation and Use of Heat Units in Pest Management: University of California Division of Agriculture and Natural Resources Leaflet 21373. University of California, Berkeley, CA.

[Nowosad]

Hi, @mimas8000 - thanks for opening this issue. You are the second person asking me this question this week.

The only GDD method available in the released version of pollen is presented as case C below (from Baskerville, G., & Emin, P. (1969). Rapid Estimation of Heat Accumulation from Maximum and Minimum Temperatures. Ecology, 50(3), 514-517. doi:10.2307/1933912):

However, I added a new option in the development version - case. It adds case B and D from the above-mentioned paper. You can install the development version from GitHub:

remotes::install_github("nowosad/pollen")

I also created a new package vignette - https://nowosad.github.io/pollen/articles/gdd.html.

Please take a look at the vignette and try the code by yourself. It still could have bugs, so I will be grateful for your feedback. Also, feel free to suggest any changes or improvements.

[mimas8000]

Thank you Jakub, this is immensely helpful! BTW I happen to be working with the other person who contacted you and I'll share this with them. I'll give the updated function a try: gdd(tmax, tmin, tbase, tbase_max, case = "C") Thanks also for developing this package. It's very useful.

[Nowosad]

@mimas8000 The updated version is on CRAN now.