Studies of Arctic Middle Atmosphere Chemistry using Infrared Absorption Spectroscopy
Bibliographic record
Abstract
The objective of this Ph.D. project is to investigate Arctic middle atmosphere chemistry using solar infrared absorption spectroscopy. These measurements were made at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut, which is operated by the Canadian Network for the Detection of Atmospheric Change (CANDAC). This research is part of the CANDAC/PEARL Arctic Middle Atmosphere Chemistry theme and aims to improve our understanding of the processes controlling the stratospheric ozone budget using measurements of the concentrations of stratospheric constituents. The instrument, a Bruker IFS 125HR Fourier transform infrared (FTIR) spectrometer, has been specifically designed for high-resolution measurements over a broad spectral range and has been used to measure reactive species, source gases, reservoirs, and dynamical tracers at PEARL since August 2006. \nThe first part of this research focuses on the optimization of ozone retrievals, for which 22 microwindows were studied and compared. The spectral region from 1000 to 1005 cm-1 was found to be the most sensitive in both the stratosphere and troposphere, giving the highest number of independent pieces of information and the smallest total error for retrievals at Eureka. \niii \nSimilar studies were performed in coordination with the Network for the Detection of Atmospheric Composition Change for nine other species, with the goal of improving and harmonizing the retrieval parameters among all Infrared Working Group sites. Previous satellite validation exercises have identified the highly variable polar conditions of the spring period to be a challenge. In this work, comparisons between the 125HR and ACE-FTS (Atmospheric Chemistry Experiment-Fourier transform spectrometer) from 2007 to 2010 have been used to develop strict criteria that allow the ground and satellite-based instruments to be confidently compared. After applying these criteria, the differences between the two instruments were generally small and in good agreement with previous ground-based FTIR/ACE-FTS comparisons. No clear bias was seen from year-to-year, and, in all cases, the difference between the measurements was within one standard deviation. The mean biases between the ACE-FTS and 125HR partial columns for 2007-2010 were -5.61 to 1.11%, -0.23 to 4.86%, -15.33 to -2.86%, -4.77 to 1.09%, and -0.34 to 5.23% for O3, HCl, ClONO2, HNO3, and HF, respectively. \nThe 125HR measurements and three atmospheric models (CMAM-DAS, GEM-BACH, and SLIMCAT) were used to derive an NOy partial column data product for Eureka. This data product includes the five primary species NO, NO2, HNO3, N2O5, and ClONO2 and was used to study the seasonal and interannual variability of NOy from 2007 to 2010. The NOy 15-40 km partial column was found to be approximately constant through the sunlit part of the year, with greater variability during the spring. The mean partial column averaged for the spring period was (2.5±0.2)x1016 molec cm-2, while for the summer, it was (2.3±0.1)x1016 molec cm-2. The springtime evolution of NOy and its constituent nitrogen species, was also examined for all four years. The variability of the 5-NOy partial column was seen to be dominated by that of HNO3. \niv \nThe evolution of the individual nitrogen species was found to be consistent with the current understanding of the chemical and dynamical processes that occur in the polar stratosphere. Unusually low ozone columns were measured at Eureka from mid-February to late March 2011 and compared to the previous 14 years of measurements by the 125HR and its predecessor, Environment Canada’s Bomem DA8. The normalized O3/HF, HCl/HF, and HNO3/HF ratios, for which the effects of dynamics have been reduced, also showed record minima over this period. The SLIMCAT chemical transport model was used to quantify chemical ozone loss using the passive subtraction method. Chemical ozone depletion inside the vortex above Eureka was estimated to be 35%, which is the largest observed there in the past 15 years.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.037 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".