Over the past year, I've been doing a lot of research about climate and turfgrass performance, especially as it relates to how much light is available for photosynthesis. You may have seen the climate charts that show the large differences in sunshine hours between cities in Asia and cities in North America and in southern Europe, even when the average temperature is quite similar. 

More recently, I've used a quantum meter to measure the instantaneous photosynthetic irradiance in Thailand, Hong Kong, and Japan, from sunrise to sunset, and I've written a short report that summarizes the results to date. The report shows the data from hundreds of measurements and explains that photosynthetic irradiance is reduced, generally, from 50% to 75% when it is cloudy. This has some bearing on the management and selection of grasses in tropical and subtropical areas with significant cloud cover that restricts the photosynthetic irradiance. Download the five page report here (1 MB).