I've added data for one more location -- Holly Springs, Mississippi -- to this analysis of light and temperature in 2014. Holly Springs in 2014 was a little cooler than Fukuoka, Tokyo, and Watkinsville, with 136 days at a mean temperature of 20°C or above. Fukuoka and Tokyo both had 150 such days in 2014, and Watkinsville had 151.

Previous posts on this topic include:

• distribution of daily light integral (DLI) at different locations
• combining DLI and temperature to look at location effect on turfgrass
• DLI and temperature in tropical and subarctic locations, for comparison and context

By adding together the mean daily temperature for each day of the year at these locations, one can see how much the total temperature is.

The temperature will have some effect on the grass. If we are thinking of ultradwarf bermudagrass, for example, it is expected that the locations with the higher temperatures will generally be better for the grass.

One can also look at the cumulative sum of the DLI.

Watkinsville had a higher cumulative temperature than Holly Springs, but the cumulative DLI was similar at those locations in 2014. And Tokyo and Fukuoka, which had higher cumulative temperatures than either Watkinsville or Holly Springs, didn't have so much DLI.

Looking only at those days with a mean temperature greater than or equal to 20°C, one sees that the distribution of DLI for Watkinsville and Holly Springs have a lot more days with DLI > 40 than do Tokyo or Fukuoka, while Tokyo and Fukuoka have a lot more days with DLI < 20 than do Watkinsville or Holly Springs.

The next calculation I'll make is the development of a DLI index, which I'll calculate as the actual DLI divided by the maximum the DLI could be on that day at that location. From this, I'll be able to express both temperature (by calculating the growth potential) and DLI on a scale of 0 to 1. Then if I multiply those two values, will I have a useful growth index?