Atmospheric visibility measurements from Automatic Weather Station (AWS) at Freiburg – Chemiehochhaus (FRCHEM) from 2023-01-01 to 2023-12-31 [L2]

Quality controlled and gap-filled continuous atmospheric visibility data (Meteorological Observable Range MOR) measured at the urban rooftop weather station at Freiburg-Chemiehochhaus (FRCHEM, 7.8486ºE, 48.0011ºN, 323.5 m) using an a forward scatter system (CS125, Present Weather and Visibility sensor, Campbell Scientific Inc.) operated 2 m above roof level.

• Quality controlled atmospheric visibility data are available and aggregated at 10min, 30min, hourly, daily, monthly and yearly resolution for the year 2023.
• Average, minimum and maximum visibility are provided on hourly, daily, monthly and annual scales.
• Hours and days with at least one minute of a visibility of less than 20, 10, 4, 2, 1, 0.5 and 0.2 km based on the WMO classes are provided on daily, monthly and annual scales. Can be used to determine frequency of fog conditions.
• Hours and days with at least one minute of a visibility of greater than 50 km are provided on daily, monthly and annual scales.
• Maximum visibility output by the CS125 is 75 km, so a value of 75 km means greater or equal 75 km. Averaged visibility accounts for values greater than 75 km with 75 km.
• Detailed information on gap-filled data is provided.
• Note: All times are provided in UTC, not local time.

For more details read `FRCHEM_2023_Visibility_MetaData.txt`.

Version 1.1

• corrects an error in the time-axis of the file "..._Visibility_10_min_UTC.csv", where previously the file would only contain reasonable values until August-15, 23:50. Other files were unaffected by this.
• displays times according to ISO 8610 to unambiguously identify that all times are given in UTC. Further, the column headers for the time periods have been changed to "From" and "To" to indicate the start and end of the aggregation periods.