1. Assessing the impact of clouds on ground-based UV–visible total column ozone measurements in the high Arctic
- Author
-
X. Zhao, K. Bognar, V. Fioletov, A. Pazmino, F. Goutail, L. Millán, G. Manney, C. Adams, K. Strong, Department of Physics [Toronto], University of Toronto, Environment and Climate Change Canada, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, NorthWest Research Associates (NWRA), Department of Physics [Socorro], New Mexico Institute of Mining and Technology [New Mexico Tech] (NMT), Environmental Monitoring and Science Division of Alberta (EMSD), and Alberta Government
- Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] ,Atmospheric Science ,Ozone ,010504 meteorology & atmospheric sciences ,lcsh:TA715-787 ,Differential optical absorption spectroscopy ,lcsh:Earthwork. Foundations ,010502 geochemistry & geophysics ,Atmospheric sciences ,01 natural sciences ,Column (database) ,lcsh:Environmental engineering ,Weather station ,Latitude ,chemistry.chemical_compound ,chemistry ,Arctic ,13. Climate action ,Measurement uncertainty ,Environmental science ,Positive bias ,lcsh:TA170-171 ,0105 earth and related environmental sciences - Abstract
Zenith-Sky scattered light Differential Optical Absorption Spectroscopy (ZS-DOAS) has been used widely to retrieve total column ozone (TCO). ZS-DOAS measurements have the advantage of being less sensitive to clouds than direct-sun measurements. However, the presence of clouds still affects the quality of ZS-DOAS TCO. Clouds are thought to be the largest contributor to random uncertainty in ZS-DOAS TCO, but their impact on data quality still needs to be quantified. This study has two goals: (1) to investigate whether clouds have a significant impact on ZS-DOAS TCO, and (2) to develop a cloud-screening algorithm to improve ZS-DOAS measurements in the Arctic under cloudy conditions. To quantify the impact of weather, 8 years of measured and modelled TCO have been used, along with information about weather conditions at Eureka, Canada (80.05∘ N, 86.41∘ W). Relative to direct-sun TCO measurements by Brewer spectrophotometers and modelled TCO, a positive bias is found in ZS-DOAS TCO measured in cloudy weather, and a negative bias is found for clear conditions, with differences of up to 5 % between clear and cloudy conditions. A cloud-screening algorithm is developed for high latitudes using the colour index calculated from ZS-DOAS spectra. The quality of ZS-DOAS TCO datasets is assessed using a statistical uncertainty estimation model, which suggests a 3 %–4 % random uncertainty. The new cloud-screening algorithm reduces the random uncertainty by 0.6 %. If all measurements collected during cloudy conditions, as identified using the weather station observations, are removed, the random uncertainty is reduced by 1.3 %. This work demonstrates that clouds are a significant contributor to uncertainty in ZS-DOAS TCO and proposes a method that can be used to screen clouds in high-latitude spectra.
- Published
- 2019
- Full Text
- View/download PDF