NDACC Dobson spectrophotometer no. 104 total ozone column data from DWD Hohenpeissenberg station

Total Column of Ozone (TCO) measured from Dobson spectrophotometer no. 104. The Dobson spectrophotometer measures TCO by comparing the relative intensities at two of three wavelength pairs in the UV wavelength range from 305.5 to 339.9 nm. These wavelength pairs are referred to as A, C, or D. Each pair is a ratio of solar irradiation in a short wavelength band that is highly absorbed by ozone, to solar irradiation in a long wavelength band that is less affected by ozone. For each measurement, an optical attenuator (a.k.a. wedge), is gradually adjusted to reduce the higher light intensity at the long wavelength, until it is equal to the lower light intensity at the short wavelength. With the information on the exact ratio of the long-to-short wavelength intensities, TOC values are then determined using the double-ratio of two pair measurements. DWD Hohenpeissenberg has been using Dobson104 operationally since 1968, with emphasis on direct sun AD measurements. Typically, these measurements are performed from Monday to Friday only, resulting in approximately 1200 measurements per year. The Dobson no. 104 undergoes regular calibration by comparison with the Dobson reference instrument Dobson no. 064, maintained by the Regional Dobson Calibration Centre Europe and also located at the Hohenpeissenberg station. For more information on the Dobson system see https://www-air.larc.nasa.gov/pub/NDACC/PUBLIC/meta/dobson/Hohenpeissenberg_dob_vv_2022.pdf. For information about stratospheric ozone at Hohenpeissenberg see https://www.dwd.de/ozon .