Diurnal variability of stratospheric column NO<sub>2</sub> measured using direct solar and lunar spectra over Table Mountain, California (34.38° N)
<p>A full diurnal measurement of stratospheric column NO<span class="inline-formula"><sub>2</sub></span> has been made over the Jet Propulsion Laboratory's Table Mountain Facility (TMF) located in the mountains above Los Angeles, California, USA (2.286 km...
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| Autores principales: | , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/fd8b51441fb24a7a8201ea68fc3a6f0b |
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| Sumario: | <p>A full diurnal measurement of stratospheric column
NO<span class="inline-formula"><sub>2</sub></span> has been made over the Jet Propulsion Laboratory's Table Mountain
Facility (TMF) located in the mountains above Los Angeles, California, USA
(2.286 km above mean sea level, 34.38<span class="inline-formula"><sup>∘</sup></span> N, 117.68<span class="inline-formula"><sup>∘</sup></span> W).
During a representative week in October 2018, a grating spectrometer
measured the telluric NO<span class="inline-formula"><sub>2</sub></span> absorptions in direct solar and lunar
spectra. The stratospheric column NO<span class="inline-formula"><sub>2</sub></span> is retrieved using a modified
minimum-amount Langley extrapolation, which enables us to accurately treat
the non-constant NO<span class="inline-formula"><sub>2</sub></span> diurnal cycle abundance and the effects of
tropospheric pollution near the measurement site. The measured 24 h cycle
of stratospheric column NO<span class="inline-formula"><sub>2</sub></span> on clean days agrees with a 1-D
photochemical model calculation, including the monotonic changes during
daytime and nighttime due to the exchange with the N<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>5</sub></span> reservoir
and the abrupt changes at sunrise and sunset due to the activation or
deactivation of the NO<span class="inline-formula"><sub>2</sub></span> photodissociation. The observed daytime
NO<span class="inline-formula"><sub>2</sub></span> increasing rate is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">1.34</mn><mo>±</mo><mn mathvariant="normal">0.24</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mn mathvariant="normal">14</mn></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="96pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="34a5641338ec0c60d4842678be7a7e17"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-14-7495-2021-ie00001.svg" width="96pt" height="15pt" src="amt-14-7495-2021-ie00001.png"/></svg:svg></span></span> cm<span class="inline-formula"><sup>−2</sup></span> h<span class="inline-formula"><sup>−1</sup></span>. The observed NO<span class="inline-formula"><sub>2</sub></span> in one of the afternoons during the
measurement period was much higher than the model simulation, implying the
influence of urban pollution from nearby counties. A 24 h back-trajectory
analysis shows that the wind first came from inland in the northeast and
reached southern Los Angeles before it turned northeast and finally
arrived at TMF, allowing it to pick up pollutants from Riverside County, Orange
County, and downtown Los Angeles.</p> |
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