Solar FTIR measurements of NO<sub><i>x</i></sub> vertical distributions – Part 1: First observational evidence of a seasonal variation in the diurnal increasing rates of stratospheric NO<sub>2</sub> and NO
<p>Observations of nitrogen dioxide (NO<span class="inline-formula"><sub>2</sub></span>) and nitrogen oxide (NO) in the stratosphere are relevant to understand long-term changes and variabilities in stratospheric nitrogen oxide (NO<span class="inline-f...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/3743/2024/acp-24-3743-2024.pdf |
| Summary: | <p>Observations of nitrogen dioxide (NO<span class="inline-formula"><sub>2</sub></span>) and nitrogen oxide (NO) in the stratosphere are relevant to understand long-term changes and variabilities in stratospheric nitrogen oxide (NO<span class="inline-formula"><sub><i>x</i></sub></span>) and ozone (O<span class="inline-formula"><sub>3</sub></span>) concentrations. Due to the versatile role of NO<span class="inline-formula"><sub>2</sub></span> and NO in stratospheric O<span class="inline-formula"><sub>3</sub></span> photochemistry, they are important for recovery and build-up of O<span class="inline-formula"><sub>3</sub></span> holes in the stratosphere and therefore can indirectly affect human life. Thus, we present in this work the evaluation of NO<span class="inline-formula"><sub>2</sub></span> and NO stratospheric partial columns (<span class="inline-formula">></span> 16 km altitude) retrieved from ground-based Fourier-transform infrared (FTIR) measurements of over 25 years at Zugspitze (47.42° N, 10.98° E; 2964 m a.s.l.) and 18 years at Garmisch (47.47° N, 11.06° E; 745 m a.s.l.), Germany. The obtained stratospheric columns are only weakly influenced by tropospheric pollution and show only a very small bias of 2.5 <span class="inline-formula">±</span> 0.2 % when comparing NO<span class="inline-formula"><sub>2</sub></span> above Zugspitze and Garmisch. Stratospheric columns of both NO<span class="inline-formula"><sub>2</sub></span> and NO show a diurnal increase that depends on local solar time (LST). We quantified this behavior by calculating diurnal increasing rates. Here, we find mean values for the NO<span class="inline-formula"><sub>2</sub></span> diurnal increasing rate of (0.89 <span class="inline-formula">±</span> 0.14) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> and (0.94 <span class="inline-formula">±</span> 0.14) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> cm<span class="inline-formula"><sup>−2</sup></span> h<span class="inline-formula"><sup>−1</sup></span> at Zugspitze and Garmisch, respectively. The mean NO morning diurnal increasing rate above Zugspitze is found to be (1.42 <span class="inline-formula">±</span> 0.12) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> cm<span class="inline-formula"><sup>−2</sup></span> h<span class="inline-formula"><sup>−1</sup></span>. Regarding the seasonal dependency of these increasing rates, for the first time, we were able to experimentally detect a significant seasonal variation in both NO<span class="inline-formula"><sub>2</sub></span> diurnal increasing rates and NO morning diurnal increasing rates with a maximum of (1.13 <span class="inline-formula">±</span> 0.04) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> cm<span class="inline-formula"><sup>−1</sup></span> h<span class="inline-formula"><sup>−1</sup></span> for NO<span class="inline-formula"><sub>2</sub></span> and (1.76 <span class="inline-formula">±</span> 0.25) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> cm<span class="inline-formula"><sup>−1</sup></span> h<span class="inline-formula"><sup>−1</sup></span> for NO in September and a minimum of (0.71 <span class="inline-formula">±</span> 0.18) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> cm<span class="inline-formula"><sup>−1</sup></span> h<span class="inline-formula"><sup>−1</sup></span> in December for NO<span class="inline-formula"><sub>2</sub></span> and a minimum of (1.18 <span class="inline-formula">±</span> 0.41) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>14</sup></span> cm<span class="inline-formula"><sup>−1</sup></span> h<span class="inline-formula"><sup>−1</sup></span> in November for NO. This similar behavior may be explained by the interconnection of both species in stratospheric photochemistry. The outcome of this work is a retrieval and analysis strategy of FTIR data for NO<span class="inline-formula"><sub><i>x</i></sub></span> stratospheric columns, which can help to further validate photochemical models or improve satellite validations. The first use of this data set is shown in the companion paper (Nürnberg et al., 2023) wherein experiment-based NO<span class="inline-formula"><sub><i>x</i></sub></span> scaling factors describing the diurnal increase in the retrieved partial columns are extracted and recently published model-based scaling factors are validated.</p> |
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| ISSN: | 1680-7316 1680-7324 |