Solar radiatio vs sunshine hrs
Posted 26 November 2011 - 21:18
Posted 27 November 2011 - 09:57
In general there is no easy direct relationship between solar radiation totals and sunshine hours. Solar radiation in w/m2 is a measurement of energy flux and the only way to make a conversion to sunshine hours is by setting a threshold and taking the current reading to compare with the maximum possible for the date/time/latitude.
What is important to note is that bright white cloud on a sunny day causes a higher reading by reflecting solar radiation back to the ground which doesn't happen with a clear blue sky - this is called diffuse solar radiation as opposed to direct solar radiation which ignores the reflected element. So it is possible for a sunny day with lots of cumulus to give a diffuse reading of 1000 w/m2 but for the next day with an apparently clear blue sky to read maybe 850 w/m2 (and there may be a haze which is invisible to the naked eye). So I imagine in theory is that a location which is generally cloud free could have lower solar radiation average over a period of time to a location that is more prone to convective cloud even if sunshine hours are comparable.
If this isn't what you meant by your question could you give an example to show?