Atmospheric visibility measurements from Automatic Weather Station (AWS) at Freiburg – Chemiehochhaus (FRCHEM) from 2020-01-01 to 2020-12-31 [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 2020. 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_2020_Visibility_MetaData.txt`.本数据集为弗赖堡化工大厦（Freiburg-Chemiehochhaus，简称FRCHEM，东经7.8486°，北纬48.0011°，海拔323.5米）城市屋顶气象站采集的、经过质量控制且已填补间隙的连续大气能见度数据——气象光学视程（Meteorological Observable Range, MOR）。该数据由安装于屋顶上方2米处的前向散射系统（CS125型天气与能见度传感器，坎贝尔科学公司（Campbell Scientific Inc.）出品）获取。 2020年的经质量控制大气能见度数据已按10分钟、30分钟、小时、日、月及年尺度完成聚合。 数据集提供小时、日、月及年尺度下的平均、最小与最大能见度统计值。 基于世界气象组织（World Meteorological Organization, WMO）分级标准，提供日、月、年尺度下，存在至少1分钟能见度低于20、10、4、2、1、0.5及0.2公里的小时与天数统计，可用于判定雾天发生频率。 同时提供日、月、年尺度下，存在至少1分钟能见度高于50公里的小时与天数统计。 CS125传感器的最大可测能见度为75公里，因此当数据值为75公里时，代表实际能见度大于或等于75公里；在计算平均能见度时，将大于75公里的数值统一按75公里处理。 关于间隙填补数据的详细说明已随数据集一并提供。 注：所有时间均采用协调世界时（UTC），而非当地时间。 更多详细信息请参阅`FRCHEM_2020_Visibility_MetaData.txt`文件。