Motion chart: difference between cool-season and warm-season growth potential

Larry Stowell from PACE Turf suggested that in addition to looking at C3 and C4 growth potential (GP) individually, as I had done in blog posts about overseeding timing at Kashima and at Dubai, it would be interesting to look at the cumulative sum of the difference between C3 and C4 GP.

If we subtract the C4 GP from the C3 GP, then a positive slope of those data plotted against time will be indicative of relatively better weather for cool-season grass. Conversely, a negative slope of the same data will be indicative of better growing weather for warm-season than for cool-season. Thus, such an approach could conceivably be used to identify the transition times in spring and autumn for overseed timing or transition back to warm-season from the overseed. Those times are expected to correspond with the inflection points on the graph – the points at which the slope changes direction.

I have examined this for 15 years of daily data, in a series of charts and explanatory text. Read another way to look at turfgrass growth potential and overseeding for a look at just how precisely this can be estimated when using daily weather data. I've made this motion chart with the "diff" variable representing the cumulative sum of monthly average C3 GP minus C4 GP. This is based on the WMO climatological normals data from 1961 to 1990 for the six locations shown on the chart. As shown here, this is only useful in a very rough sense, because these are monthly average data, rather than daily. One can only get an approximate idea of transition time from warm to cool-season weather, and vice versa. However, it is interesting to have data from multiple locations on the same plot.

Data: plot • Chart ID: gpinflection

R version 3.0.2 (2013-09-25) • googleVis-0.4.7
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On Data, Charts, and Software

Data shown on these charts are from the World Meteorological Organization and, in the case of the Japan motion chart, from the Japanese Meteorological Agency.

The static charts were made using the ggplot2 package in R. Motion charts were made using the googleVis package in R. This document explains the procedure I used to make a motion chart with data from 52 world cities.

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