I have ground-level radiation data of solar incoming radiation from a radiometer (cosine collector) measured along the day. In the following plot you can see PAR irradiance (ie visible light) in Watts per square meter versus time of day (local time). AS usual for this type of sensor, radiation intensity varies with the Sun's angle with respect to the ground level.
As you can see it doesn't look perfectly smooth, rather it has some 'chopped' sections (most notably after maximum at noon) due to the presence of transient, passing-by clouds. I would like to use these data points to fit a model and obtain the ideal radiation curve as if it was a clear-sky day, ie perfect, continuous curve.
As you can see it is not a gaussian curve... I've heard before that the appropriate model is the Rayleigh distribution, but I'm not sure...
What do you think? is that the correct one or should I use another distribution? I don't want just to fit any equation, rather I want to use the appropriate one which is suitable for investigating ant testing the corresponding parameters. Thanks!