01 Nov 2023
 | 01 Nov 2023

Solar FTIR measurements of NOx vertical distributions: Part II) Experiment-based scaling factors describing the diurnal increase of stratospheric NO2 and NO

Pinchas Nürnberg, Sarah A. Strode, and Ralf Sussmann

Abstract. Long-term experimental stratospheric NO2 and NO partial columns measured by means of solar Fourier-transform infrared (FTIR) spectromertry at Zugspitze (47.42° N, 10.98° E, 2964 m a.s.l.), Germany were used to create a set of experiment-based monthly scaling factors (SFexp). The underlying data set is published in a companion paper (Nürnberg et al., 2023) comprising over 25 years of measurements depicting the diurnal variability of stratospheric NO2 and NO partial columns in dependence of local solar time (LST). In analogy to recently published simulation-based scaling factors by Strode et al. (2022), we created SFexp normalized to local solar noon for NO2 and NO for every month of the year as a function of solar zenith angle (SZA). Beside a boundary value problem at minimum SZA values originating in averaging over different times of the month, the obtained scaling factors SFexp(NO2) and SFexp(NO) in dependence of SZA represent very well the diurnal behavior already shown in model simulations and experiment in the literature. This behavior is a well pronounced increase of the NO2 and NO stratospheric partial colum with the time of the day and a flattening of this increase after noon. In addition to the discussion of SFexp, we validate the simulation-based scaling factors SFsim(NO2) (Strode et al., 2022) and present simulation-based scaling factors for NO SFsim(NO). The simulation-based scaling factors show an excellent agreement with our the experiment-based ones, i.e. for NO2 and NO the mean bias of the modulus between experiment and simulation over all SZA and months is only 0.02 %. We show, that recently used model simulations can describe very well the real behavior of nitrogen oxide (NOx) variability in the stratosphere. Furthermore, we conclude that ground-based FTIR measurements can be used for validation of the output of photochemistry models as well as creating experiment-based data sets describing the diurnal stratospheric NOx variability in dependence of SZA. This is a contribution to improved satellite validation and a better understanding of stratospheric photochemistry.

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Pinchas Nürnberg, Sarah A. Strode, and Ralf Sussmann

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1437', Anonymous Referee #2, 21 Nov 2023
  • RC2: 'Comment on egusphere-2023-1437', Anonymous Referee #1, 24 Nov 2023
  • AC1: 'Comment on egusphere-2023-1437', Pinchas Nürnberg, 05 Apr 2024
Pinchas Nürnberg, Sarah A. Strode, and Ralf Sussmann
Pinchas Nürnberg, Sarah A. Strode, and Ralf Sussmann


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Short summary
We created a set of scaling factors describing the diurnal increase of stratospheric nitrogen oxides above Zugspitze, Germany. We used these factors to validate recently published model simulation data. On the one hand, this validation helps to use the validated data to better understand the stratospheric photochemistry. On the other hand, it can improve satellite validation which has implications for the understanding of urban smog events and other pollution events in the troposphere.