OH column abundance over Table Mountain Facility, California: Annual average 1997–2000

Mills, F. P.; Cageao, R. P.; Nemtchinov, V.; Jiang, Yibo; Sander, Stanley P.

doi:10.1029/2001gl014151

Cited by 10 publications

(23 citation statements)

References 13 publications

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“…1C, gray), with an uncertainty of ±3% (1σ). This OH variability agrees with that observed over the FPO (15), although the absolute values of X OH from the FPO and TMF, both in middle latitudes, have shown statistical differences of several tens of percentage points (27).…”

Section: Observational Evidencesupporting

confidence: 78%

Midlatitude atmospheric OH response to the most recent 11-y solar cycle

Wang

Pongetti

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The hydroxyl radical (OH) plays an important role in middle atmospheric photochemistry, particularly in ozone (O 3 ) chemistry. Because it is mainly produced through photolysis and has a short chemical lifetime, OH is expected to show rapid responses to solar forcing [e.g., the 11-y solar cycle (SC)], resulting in variabilities in related middle atmospheric O 3 chemistry. Here, we present an effort to investigate such OH variability using long-term observations (from space and the surface) and model simulations. Groundbased measurements and data from the Microwave Limb Sounder on the National Aeronautics and Space Administration's Aura satellite suggest an ∼7-10% decrease in OH column abundance from solar maximum to solar minimum that is highly correlated with changes in total solar irradiance, solar Mg-II index, and Lyman-α index during SC 23. However, model simulations using a commonly accepted solar UV variability parameterization give much smaller OH variability (∼3%). Although this discrepancy could result partially from the limitations in our current understanding of middle atmospheric chemistry, recently published solar spectral irradiance data from the Solar Radiation and Climate Experiment suggest a solar UV variability that is much larger than previously believed. With a solar forcing derived from the Solar Radiation and Climate Experiment data, modeled OH variability (∼6-7%) agrees much better with observations. Model simulations reveal the detailed chemical mechanisms, suggesting that such OH variability and the corresponding catalytic chemistry may dominate the O 3 SC signal in the upper stratosphere. Continuing measurements through SC 24 are required to understand this OH variability and its impacts on O 3 further.decadal variability | odd hydrogen Q uantifying effects of the solar cycle (SC) in Earth's atmosphere helps differentiate relative contributions of natural processes and anthropogenic activities to global climate change (1). From the 11-y SC maximum (max) to minimum (min), the total solar irradiance (TSI) varies only by ∼0.1%. However, changes in solar UV fluxes can be much larger (2). Thus, detectable SC impacts on Earth's climate are more likely to be linked to changes in middle (stratosphere and mesosphere, tropopause to ∼90 km) and upper (thermosphere and above) atmospheric composition through photochemistry in the UV region.A number of observational and modeling studies have characterized SC modulations in mesospheric and stratospheric chemistry, especially in ozone (O 3 ) (3-9). Changes in UV absorption by O 3 at low latitudes over the SC can lead to changes in thermal structures in the middle atmosphere, affecting tropospheric and polar climates, and may lead to changes in global circulations (1). Accurate simulations of the O 3 response to the SC are therefore required for better understanding the sun-climate relationship (10, 11). However, the SC signal in O 3 simulated by different models shows quantitative differences, which may be due to differences in model resolutions, model...

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Section: Observational Evidencesupporting

confidence: 78%

Midlatitude atmospheric OH response to the most recent 11-y solar cycle

Wang

Pongetti

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…An earlier study using TMF spectra also analyzed the Q 1 ð2Þ line at 32; 458:5918 cm −1 [2] with good agreement being observed with the P 1 ð1Þ results [30]. The other OH lines are weaker and have greater interference from solar lines, and until recently these have not been reliably retrieved with existing techniques.…”

Section: Multiple Absorption Line Analysismentioning

confidence: 79%

“…10). The five lines chosen are the same used in [27], and the calculation of the uncertainty is similar to that described in [30]. One important difference between this calculation and that of [30] is that here the uncertainty is calculated relative to a second order polynomial fit to the diurnal OH profile, rather than relative to a separate linear fit to both the morning and afternoon OH column abundances.…”

Section: Use Of the "Nanowindow" And The Conjugate-gradient Fitmentioning

confidence: 93%

“…The method here is similar to that used to find Fig. 2 of Mills et al [30], except that the deviation is calculated from a second order polynomial fit to the diurnal OH column abundances, instead of two separate linear fits to the morning and afternoon OH abundances.…”

Section: Discussionmentioning

confidence: 99%

“…Within the ∼400 cm −1 bandpass of the frontend interference filter, over twenty lines in the OH A 2 Σ þ ←X 2 Π (0,0) band have been observed by FTUVS. The groups [20][21][22] that have employed Fabry-Perot and grating spectrometers to measure OH have all used the P 1 ð1Þ line at 32; 440:5741 cm −1 , because the solar baseline is reasonably flat and the line itself is one of the strongest in the band [30][31][32][33].…”

Section: Multiple Absorption Line Analysismentioning

confidence: 99%

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Atmospheric hydroxyl radical (OH) abundances from ground-based ultraviolet solar spectra: an improved retrieval method

Cheung

Wang

et al. 2008

Appl. Opt.

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The Fourier Transform Ultraviolet Spectrometer (FTUVS) instrument has recorded a long-term data record of the atmospheric column abundance of the hydroxyl radical (OH) using the technique of high resolution solar absorption spectroscopy. We report new efforts in improving the precision of the OH measurements in order to better model the diurnal, seasonal, and interannual variability of odd hydrogen (HO x ) chemistry in the stratosphere, which, in turn, will improve our understanding of ozone chemistry and its long-term changes. Until the present, the retrieval method has used a single strong OH absorption line P 1 ð1Þ in the near-ultraviolet at 32; 341 cm −1 . We describe a new method that uses an average based on spectral fits to multiple lines weighted by line strength and fitting precision. We have also made a number of improvements in the ability to fit a model to the spectral feature, which substantially reduces the scatter in the measurements of OH abundances.

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