I’ve made estimates of the relative effect of morning or afternoon shade on turf. These previous estimates have been inconsistent in accounting for solar noon, daylight savings time, and clouds. Sometimes I have made the adjustments, and sometimes I haven’t.

In this analysis, I attempt to be more accurate by:

For some background and links to previous calculations, see this on AM and PM shade.

Tom Cook wrote:

“I have always felt morning sun and afternoon shade in Corvallis OR provides the best case scenario for healthy turf and reduced irrigation needs. On my own site I have been able to reduce irrigation in mid summer by probably 25% compared to full sun.”

In this analysis, I will try to put a number to morning and afternoon sun in Corvallis, OR, and in Ithaca, NY, based on temperatures and global solar radiation measures in 2013 and 2014.

The data

First, I downloaded the 2013 and 2014 sub-hourly (5 minute) quality controlled data for Corvallis and Ithaca. One year of measurements on 5 minute intervals is 105,210 measurements. For this analysis, I looked especially at the air temperature and global solar radiation measurements.