I really need some reliable measured hourly weather data for a few sites across the world. It needs to include solar diffuse and direct values or their equivalents.
I've tried the usual sources: Met Office, Weather Underground and Weather Analytics but none of them provide what I need. They are either not hourly, don't contain solar radiation, or have difficult licence/ access restrictions. This is for some research to determine if there's any relation between position of sun, temperature, relative humidity, wind speed and direction. So I'd need a couple of years data for a couple of locations. Aggregate data isn't much use I'm afraid.