Solar irradiance measurements from Automatic Weather Station (AWS) at Freiburg – Chemiehochhaus (FRCHEM) from 2018-01-01 to 2018-12-31 [L2]

Quality controlled and gap-filled continuous solar irradiance measurements from the urban rooftop weather station at Freiburg-Chemiehochhaus (FRCHEM, 7.8486ºE, 48.0011ºN, 323.5 m) operated 2 m above roof level. Solar irradiance is measured using a ventilated pyranometer CM21 (Kipp & Zonen, Delft, Netherlands). The pyranometer was replaced and factory calibrated at Kipp & Zonen on 2018-01-10.

• Quality controlled above-canopy solar irradiance data are available and aggregated at 10min, 30min, hourly, daily, monthly and yearly resolution for the year 2018. Values are averages during the periods shown.
• Solar irradiance in this dataset is equal "global irradiance" or "global hemispherical irrandiance" and does not distinguish between direct and diffuse irradiance.
• Modeled extraterrestrial irradiance (based on the NOAA General Solar Position Calculations of the NOAA Global Monitoring Division and considering the Earth's elliptical orbit) is provided for comparison, along with the ratio of solar irradiance to extraterrestrial  irradiance at 10min, 30min, hourly, daily, monthly and yearly resolution. Extraterrestrial irradiance is average of period show.
• Data in the mid-morning on clear-sky days in summer can be impacted for a few minutes by a guy-wire of the mast, slightly reducing readings. Data from affected periods are not removed. 
• Number of hours with solar irradiance >5 W/m2 (daylight hours) and > 120 W/m2 (sometimes used as threshold for "sun hours") provided on daily, monthly, and annual scale.
• Number of days with solar irradiance >5 W/m2 (quality check) and > 120 W/m2 ("sun hours") provided on monthly, and annual scale.
• Detailed information on gap-filled data is provided.
• Note: All times are provided in UTC, not local time.

For more details read `FRCHEM_2018_SolarIrradiance_MetaData.txt`.