The “Long-Term” data type option will create a data file that starts somewhere between 1997 and 1999, depending on the region. The data file contains hourly mean solar and weather parameters updated regularly using the latest available satellite imager data. By looking at multiple years of resource data, you can get a better understanding of what to expect for inter-annual variation in power. Probability of exceedance values can be derived from the long-term resource data.