As a continuation of these calculations I made about light, temperature, and shade influence on growth in Mobara, I have made another round of calculations for Hamburg.
I've used 2014 weather data for both locations. For Mobara, the data are more precise, because I used 10 minute intervals of temperature through the year, and I accounted for the reduction of clouds on PPFD based on minute by minute measurements of bright sunshine, collected into 10 minute intervals for a year. For Hamburg, I used hourly temperature data, and I did not attempt to account for the cloud cover, so the results shown here are as if every day were sunny with no clouds.
The summary of the data from Mobara showed that afternoon shade, starting 2 hours after solar noon, will reduce PPFD when temperatures are good for C3 grass growth more than morning shade during the months of October to April. Morning shade, from sunrise until 2 hours before solar noon, would be worse than afternoon shade from May to September.
How about in Hamburg?
First, I calculated the estimated average PPFD for every second at each hour of every day. This is 15 May 2014, as an example.
Then for every hour between sunrise and sunset, I calculated the GP for C3 grasses based on the hourly temperature. That gives this result, which is the GP on an hourly basis throughout the year.
Most of the hours in which GP is above 0.5 are from March to October. That makes sense, because the cold winter temperatures in Hamburg are not very good for grass to grow.
Then, I chose 0.5 GP as a cutoff for what I would consider good growing conditions for C3 grass, and I plotted the hourly average PPFD, for a sunny day with no clouds, for each of those hours with a GP greater than or equal to 0.5. In total, this comes to 2,279 hours in the year.
Finally, I simulated morning or afternoon shade by reducing PPFD by 80% from sunrise to 2 hours before solar noon (morning shade) or from 2 hours after solar noon until sunset (afternoon shade). The result is similar to Mobara.
Of course, full sun, with no shade, is best. Any type of shade is going to reduce the photosynthetically active radiation (PAR). But by making the calculations for every hour of the year, based on the temperature during that hour, one can predict the relative effect of afternoon or morning shade. In July, August, and September, morning shade at Hamburg should be more detrimental to the grass than afternoon shade. In the autumn it doesn't matter. Both shade timings are equally detrimental. In December, January, and February, it is so cold that there isn't any useful PAR at temperatures when the grass can grow well. And in March and April, afternoon shade is more detrimental than morning shade.