Total Column O3 Research Articles

Ground-based Measurements of Atmospheric Trace Gases in Beijing during the Olympic Games

A portable Fourier Transform Spectrometer (B3M-IR) is built and used to measure atmospheric trace gases in the city of Beijing during Olympic Games in 2008. A short description of the instrument is first provided in this paper. A detailed spectral analysis is then presented. The total columns of ozone (O3), carbon monoxide (CO), methane (CH4) and nitrous oxide (N2O) are retrieved from the ground-based solar absorption spectra recorded by the B3M-IR during the Olympic Games. Lacking validation data, only the retrieved total column of O3 is compared with that retrieved by MAX-DOAS, which is deployed at the same station. The mean difference between the two methods of measurement is 6.5%, demonstrating the performance and reliability of B3M-IR.

Ground-based Measurements of Atmospheric Trace Gases in Beijing during the Olympic Games

A portable Fourier Transform Spectrometer (B3M-IR) is built and used to measure atmospheric trace gases in the city of Beijing during Olympic Games in 2008. A short description of the instrument is first provided in this paper. A detailed spectral analysis is then presented. The total columns of ozone (O3), carbon monoxide (CO), methane (CH4) and nitrous oxide (N2O) are retrieved from the ground-based solar absorption spectra recorded by the B3M-IR during the Olympic Games. Lacking validation data, only the retrieved total column of O3 is compared with that retrieved by MAX-DOAS, which is deployed at the same station. The mean difference between the two methods of measurement is 6.5%, demonstrating the performance and reliability of B3M-IR.

Ground-based Measurements of Atmospheric Trace Gases in Beijing during the Olympic Games

A portable Fourier Transform Spectrometer (B3M-IR) is built and used to measure atmospheric trace gases in the city of Beijing during Olympic Games in 2008. A short description of the instrument is first provided in this paper. A detailed spectral analysis is then presented. The total columns of ozone (O3), carbon monoxide (CO), methane (CH4) and nitrous oxide (N2O) are retrieved from the ground-based solar absorption spectra recorded by the B3M-IR during the Olympic Games. Lacking validation data, only the retrieved total column of O3 is compared with that retrieved by MAX-DOAS, which is deployed at the same station. The mean difference between the two methods of measurement is 6.5%, demonstrating the performance and reliability of B3M-IR.

Ground-based Measurements of Atmospheric Trace Gases in Beijing during the Olympic Games

A portable Fourier Transform Spectrometer (B3M-IR) is built and used to measure atmospheric trace gases in the city of Beijing during Olympic Games in 2008. A short description of the instrument is first provided in this paper. A detailed spectral analysis is then presented. The total columns of ozone (O3), carbon monoxide (CO), methane (CH4) and nitrous oxide (N2O) are retrieved from the ground-based solar absorption spectra recorded by the B3M-IR during the Olympic Games. Lacking validation data, only the retrieved total column of O3 is compared with that retrieved by MAX-DOAS, which is deployed at the same station. The mean difference between the two methods of measurement is 6.5%, demonstrating the performance and reliability of B3M-IR.

The MUSCLES Treasury Survey. V. FUV Flares on Active and Inactive M Dwarfs* † ‡

Abstract M dwarf stars are known for their vigorous flaring. This flaring could impact the climate of orbiting planets, making it important to characterize M dwarf flares at the short wavelengths that drive atmospheric chemistry and escape. We conducted a far-ultraviolet flare survey of six M dwarfs from the recent MUSCLES (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) observations, as well as four highly active M dwarfs with archival data. When comparing absolute flare energies, we found the active-M-star flares to be about 10× more energetic than inactive-M-star flares. However, when flare energies were normalized by the star’s quiescent flux, the active and inactive samples exhibited identical flare distributions, with a power-law index of (cumulative distribution). The rate and distribution of flares are such that they could dominate the FUV energy budget of M dwarfs, assuming the same distribution holds to flares as energetic as those cataloged by Kepler and ground-based surveys. We used the observed events to create an idealized model flare with realistic spectral and temporal energy budgets to be used in photochemical simulations of exoplanet atmospheres. Applied to our own simulation of direct photolysis by photons alone (no particles), we find that the most energetic observed flares have little effect on an Earth-like atmosphere, photolyzing ∼0.01% of the total O3 column. The observations were too limited temporally (73 hr cumulative exposure) to catch rare, highly energetic flares. Those that the power-law fit predicts occur monthly would photolyze ∼1% of the O3 column and those it predicts occur yearly would photolyze the full O3 column. Whether such energetic flares occur at the rate predicted is an open question.

Atmospheric Trace Gas (NO2 and O3) Variability in South Korean Coastal Waters, and Implications for Remote Sensing of Coastal Ocean Color Dynamics

Coastal environments are highly dynamic, and are characterized by short-term, local-scale variability in atmospheric and oceanic processes. Yet, high-frequency measurements of atmospheric composition, and particularly nitrogen dioxide (NO2) and ozone (O3) dynamics, are scarce over the ocean, introducing uncertainties in satellite retrievals of coastal ocean biogeochemistry and ecology. Combining measurements from different platforms, the Korea-US Ocean Color and Air Quality field campaign provided a unique opportunity to capture, for the first time, the strong spatial dynamics and diurnal variability in total column (TC) NO2 and O3 over the coastal waters of South Korea. Measurements were conducted using a shipboard Pandora Spectrometer Instrument specifically designed to collect accurate, high-frequency observations from a research vessel, and were combined with ground-based observations at coastal land sites, synoptic satellite imagery, and air-mass trajectory simulations to assess source contributions to atmospheric pollution over the coastal ocean. TCO3 showed only small (<20%) variability that was driven primarily by larger-scale meteorological processes captured successfully in the relatively coarse satellite imagery from Aura-OMI. In contrast, TCNO2 over the ocean varied by more than an order of magnitude (0.07–0.92 DU), mostly affected by urban emissions and highly dynamic air mass transport pathways. Diurnal patterns varied widely across the ocean domain, with TCNO2 in the coastal area of Geoje and offshore Seoul varying by more than 0.6 DU and 0.4 DU, respectively, over a period of less than 3 h. On a polar orbit, Aura-OMI is not capable of detecting these short-term changes in TCNO2. If unaccounted for in atmospheric correction retrievals of ocean color, the observed variability in TCNO2 would be misinterpreted as a change in ocean remote sensing reflectance, Rrs, by more than 80% and 40% at 412 and 443 nm, respectively, introducing a significant false variability in retrievals of coastal ocean ecological processes from space.

Monitoring air pollution in China from geostationary satellite: A synthetic study using simulated observations

We simulated geostationary satellite observations to assess the potential for high spatial- and temporal-resolution monitoring of air pollution in China with a focus on tropospheric ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO). Based on the capabilities and parameters of the payloads onboard sun-synchronous satellites, we simulated the observed spectrum based on a radiative transfer model using a geostationary satellite model. According to optimal estimation theory, we analyzed the sensitivities and retrieval uncertainties of the main parameters of the instrument for the target trace gases. Considering the retrieval error requirements of each trace gas, we determined the major instrument parameter values (e.g., observation channel, spectral resolution, and signal-to-noise ratio). To evaluate these values, retrieval simulation was performed based on the three-dimensional distribution of the atmospheric components over China using an atmospheric chemical transportation model. As many as 90% of the experiments met the retrieval requirements for all target gases. The retrieval precision of total-column and stratospheric O3 was 2%. In addition, effective retrieval of all trace gases could be achieved at solar zenith angles larger than 70°. Therefore, the geostationary satellite observation and instrument parameters provided herein can be used in air pollution monitoring in China. This study offers a theoretical basis and simulation tool for improving the design of instruments onboard geostationary satellites.

The influence of instrumental line shape degradation on NDACC gas retrievals: total column and profile

Abstract. We simulated instrumental line shape (ILS) degradations with respect to typical types of misalignment, and compared their influence on each NDACC (Network for Detection of Atmospheric Composition Change) gas. The sensitivities of the total column, the root mean square (rms) of the fitting residual, the total random uncertainty, the total systematic uncertainty, the total uncertainty, degrees of freedom for signal (DOFs), and the profile with respect to different levels of ILS degradation for all current standard NDACC gases, i.e. O3, HNO3, HCl, HF, ClONO2, CH4, CO, N2O, C2H6, and HCN, were investigated. The influence of an imperfect ILS on NDACC gases' retrieval was assessed, and the consistency under different meteorological conditions and solar zenith angles (SZAs) were examined. The study concluded that the influence of ILS degradation can be approximated by the linear sum of individual modulation efficiency (ME) amplitude influence and phase error (PE) influence. The PE influence is of secondary importance compared with the ME amplitude. Generally, the stratospheric gases are more sensitive to ILS degradation than the tropospheric gases, and the positive ME influence is larger than the negative ME. For a typical ILS degradation (10 %), the total columns of stratospheric gases O3, HNO3, HCl, HF, and ClONO2 changed by 1.9, 0.7, 4, 3, and 23 %, respectively, while the columns of tropospheric gases CH4, CO, N2O, C2H6, and HCN changed by 0.04, 2.1, 0.2, 1.1, and 0.75 %, respectively. In order to suppress the fractional difference in the total column for ClONO2 and other NDACC gases within 10 and 1 %, respectively, the maximum positive ME degradations for O3, HNO3, HCl, HF, ClONO2, CO, C2H6, and HCN should be less than 6, 15, 5, 5, 5, 5, 9, and 13 %, respectively; the maximum negative ME degradations for O3, HCl, and HF should be less than 6, 12, and 12 %, respectively; the influence of ILS degradation on CH4 and N2O can be regarded as being negligible.

Analysis of multi-year near-surface ozone observations at the WMO/GAW “Concordia” station (75°06′S, 123°20′E, 3280 m a.s.l. – Antarctica)

This work focuses on the near-surface O3 variability over the eastern Antarctic Plateau. In particular, eight years (2006–2013) of continuous observations at the WMO/GAW contributing station “Concordia” (Dome C–DMC: 75°06′S, 123°20′E, 3280 m) are presented, in the framework of the Italian Antarctic Research Programme (PNRA). First, the characterization of seasonal and diurnal O3 variability at DMC is provided. Then, for the period of highest data coverage (2008–2013), we investigated the role of specific atmospheric processes in affecting near-surface summer O3 variability, when O3 enhancement events (OEEs) are systematically observed at DMC (average monthly frequency peaking up to 60% in December). As deduced by a statistical selection methodology, these OEEs are affected by a significant interannual variability, both in their average O3 values and in their frequency. To explain part of this variability, we analyzed OEEs as a function of specific atmospheric variables and processes: (i) total column of O3 (TCO) and UV-A irradiance, (ii) long-range transport of air masses over the Antarctic Plateau (by Lagrangian back-trajectory analysis – LAGRANTO), (iii) occurrence of “deep” stratospheric intrusion events (by using the Lagrangian tool STLEFLUX). The overall near-surface O3 variability at DMC is controlled by a day-to-day pattern, which strongly points towards a dominating influence of processes occurring at “synoptic” scales rather than “local” processes. Even if previous studies suggested an inverse relationship between OEEs and TCO, we found a slight tendency for the annual frequency of OEEs to be higher when TCO values are higher over DMC. The annual occurrence of OEEs at DMC seems related to the total time spent by air masses over the Antarctic plateau before their arrival to DMC, suggesting the accumulation of photochemically-produced O3 during the transport, rather than a more efficient local production. Moreover, the identification of recent (i.e., 4-day old) stratospheric intrusion events by STEFLUX suggested only a minor influence (up to 3% of the period, in November) of “deep” events on the variability of near-surface summer O3 at DMC.

Multi-year comparisons of ground-based and space-borne Fourier transform spectrometers in the high Arctic between 2006 and 2013

Abstract. This paper presents 8 years (2006–2013) of measurements obtained from Fourier transform spectrometers (FTSs) in the high Arctic at the Polar Environment Atmospheric Research Laboratory (PEARL; 80.05° N, 86.42° W). These measurements were taken as part of the Canadian Arctic ACE (Atmospheric Chemistry Experiment) validation campaigns that have been carried out since 2004 during the polar sunrise period (from mid-February to mid-April). Each spring, two ground-based FTSs were used to measure total and partial columns of HF, O3, and trace gases that impact O3 depletion, namely, HCl and HNO3. Additionally, some tropospheric greenhouse gases and pollutant species were measured, namely CH4, N2O, CO, and C2H6. During the same time period, the satellite-based ACE-FTS made measurements near Eureka and provided profiles of the same trace gases. Comparisons have been carried out between the measurements from the Portable Atmospheric Research Interferometric Spectrometer for the InfraRed (PARIS-IR) and the co-located high-resolution Bruker 125HR FTS, as well as with the latest version of the ACE-FTS retrievals (v3.5). The total column comparison between the two co-located ground-based FTSs, PARIS-IR and Bruker 125HR, found very good agreement for most of these species (except HF), with differences well below the estimated uncertainties ( ≤ 6 %) and with high correlations (R ≥ 0. 8). Partial columns have been used for the ground-based to space-borne comparison, with coincident measurements selected based on time, distance, and scaled potential vorticity (sPV). The comparisons of the ground-based measurements with ACE-FTS show good agreement in the partial columns for most species within 6 % (except for C2H6 and PARIS-IR HF), which is consistent with the total retrieval uncertainty of the ground-based instruments. The correlation coefficients (R) of the partial column comparisons for all eight species range from approximately 0.75 to 0.95. The comparisons show no notable increases of the mean differences over these 8 years, indicating the consistency of these datasets and suggesting that the space-borne ACE-FTS measurements have been stable over this period. In addition, changes in the amounts of these trace gases during springtime between 2006 and 2013 are presented and discussed. Increased O3 (0. 9 % yr−1), HCl (1. 7 % yr−1), HF (3. 8 % yr−1), CH4 (0.5 % yr−1), and C2H6 (2. 3 % yr−1, 2009–2013) have been found with the PARIS-IR dataset, the longer of the two ground-based records.

First reprocessing of Southern Hemisphere ADditional OZonesondes (SHADOZ) profile records (1998–2015): 1. Methodology and evaluation

AbstractElectrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long‐term data records for deriving O3trends, model development, satellite validation, and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reporting, and instrument changes that have resulted in inhomogeneities within individual station data records. A major milestone is the first reprocessing of seven Southern Hemisphere ADditional OZonesondes (SHADOZ) station ozonesonde records to account for errors and biases in operating/processing procedures. Ascension Island, Hanoi, Irene, Kuala Lumpur, La Réunion, Natal, and Watukosek station records all show an overall increase in O3after reprocessing. Watukosek shows the largest increase of 9.0 ± 2.1 Dobson Units (DU) in total column O3; Irene and Hanoi show a 5.5 ± 2.5 DU increase, while remaining sites show statistically insignificant enhancements. Negligible to modest O3enhancements are observed after reprocessing in the troposphere (up to 8%) and stratosphere (up to 6%), except at La Réunion for which the application of background currents reduces tropospheric O3(−2.1 ± 1.3 DU). Inhomogeneities due to ozonesonde/solution‐type changes at Ascension, Natal, and La Réunion are resolved with the application of transfer functions. Comparisons with EP‐TOMS, Aura's Ozone Monitoring Instrument and Microwave Limb Sounder (MLS) satellite O3overpasses show an overall improvement in agreement after reprocessing. Most reprocessed data sets show a significant reduction in biases with MLS at the ozone maximum region (50–10 hPa). Changes in radiosonde/ozonesonde system and nonstandard solution types can account for remaining discrepancies observed at several sites when compared to satellites.

Spatial and temporal variability of ground and satellite column measurements of NO2 and O3 over the Atlantic Ocean during the Deposition of Atmospheric Nitrogen to Coastal Ecosystems Experiment

AbstractIn situ measurements of O3 and nitrogen oxides (NO + NO2 ≡ NOx) and remote sensing measurements of total column NO2 and O3 were collected on a ship in the North Atlantic Ocean as part of the Deposition of Atmospheric Nitrogen to Coastal Ecosystems (DANCE) campaign in July–August 2014, ~100 km east of the mid‐Atlantic United States. Relatively clean conditions for both surface in situ mixing ratio and total column O3 and NO2 measurements were observed throughout the campaign. Increased surface and column NO2 and O3 amounts were observed when a terrestrial air mass was advected over the study region. Relative to ship‐based total column measurements using a Pandora over the entire study, satellite measurements overestimated total column NO2 under these relatively clean atmospheric conditions over offshore waters by an average of 16%. Differences are most likely due to proximity, or lack thereof, to surface emissions; spatial averaging due to the field of view of the satellite instrument; and the lack of sensitivity of satellite measurements to the surface concentrations of pollutants. Total column O3 measurements from the shipboard Pandora showed good correlation with the satellite measurements (r = 0.96), but satellite measurements were 3% systematically higher than the ship measurements, in agreement with previous studies. Derived values of boundary layer height using the surface in situ and total column measurements of NO2 are much lower than modeled and satellite‐retrieved boundary layer heights, which highlight the differences in the vertical distribution between terrestrial and marine environments.

Tropospheric ozonesonde profiles at long-term U.S. monitoring sites: 1. A climatology based on self-organizing maps.

Sonde-based climatologies of tropospheric ozone (O3) are vital for developing satellite retrieval algorithms and evaluating chemical transport model output. Typical O3 climatologies average measurements by latitude or region, and season. Recent analysis using self-organizing maps (SOM) to cluster ozonesondes from two tropical sites found clusters of O3 mixing ratio profiles are an excellent way to capture O3 variability and link meteorological influences to O3 profiles. Clusters correspond to distinct meteorological conditions, e.g. convection, subsidence, cloud cover, and transported pollution. Here, the SOM technique is extended to four long-term U.S. sites (Boulder, CO; Huntsville, AL; Trinidad Head, CA; Wallops Island, VA) with 4530 total profiles. Sensitivity tests on k-means algorithm and SOM justify use of 3×3 SOM (nine clusters). At each site, SOM clusters together O3 profiles with similar tropopause height, 500 hPa height/temperature, and amount of tropospheric and total column O3. Cluster means are compared to monthly O3 climatologies. For all four sites, near-tropopause O3 is double (over +100 parts per billion by volume; ppbv) the monthly climatological O3 mixing ratio in three clusters that contain 13 - 16% of profiles, mostly in winter and spring. Large mid-tropospheric deviations from monthly means (-6 ppbv, +7 - 10 ppbv O3 at 6 km) are found in two of the most populated clusters (combined 36 - 39% of profiles). These two clusters contain distinctly polluted (summer) and clean O3 (fall-winter, high tropopause) profiles, respectively. As for tropical profiles previously analyzed with SOM, O3 averages are often poor representations of U.S. O3 profile statistics.

Atmospheric nitrogen oxides (NO and NO<sub>2</sub>) at Dome C, East Antarctica, during the OPALE campaign

Abstract. Mixing ratios of the atmospheric nitrogen oxides NO and NO2 were measured as part of the OPALE (Oxidant Production in Antarctic Lands & Export) campaign at Dome C, East Antarctica (75.1° S, 123.3° E, 3233 m), during December 2011 to January 2012. Profiles of NOx mixing ratios of the lower 100 m of the atmosphere confirm that, in contrast to the South Pole, air chemistry at Dome C is strongly influenced by large diurnal cycles in solar irradiance and a sudden collapse of the atmospheric boundary layer in the early evening. Depth profiles of mixing ratios in firn air suggest that the upper snowpack at Dome C holds a significant reservoir of photolytically produced NO2 and is a sink of gas-phase ozone (O3). First-time observations of bromine oxide (BrO) at Dome C show that mixing ratios of BrO near the ground are low, certainly less than 5 pptv, with higher levels in the free troposphere. Assuming steady state, observed mixing ratios of BrO and RO2 radicals are too low to explain the large NO2 : NO ratios found in ambient air, possibly indicating the existence of an unknown process contributing to the atmospheric chemistry of reactive nitrogen above the Antarctic Plateau. During 2011–2012, NOx mixing ratios and flux were larger than in 2009–2010, consistent with also larger surface O3 mixing ratios resulting from increased net O3 production. Large NOx mixing ratios at Dome C arise from a combination of continuous sunlight, shallow mixing height and significant NOx emissions by surface snow (FNOx). During 23 December 2011–12 January 2012, median FNOx was twice that during the same period in 2009–2010 due to significantly larger atmospheric turbulence and a slightly stronger snowpack source. A tripling of FNOx in December 2011 was largely due to changes in snowpack source strength caused primarily by changes in NO3− concentrations in the snow skin layer, and only to a secondary order by decrease of total column O3 and associated increase in NO3− photolysis rates. A source of uncertainty in model estimates of FNOx is the quantum yield of NO3− photolysis in natural snow, which may change over time as the snow ages.

Data assimilation of satellite-retrieved ozone, carbon monoxide and nitrogen dioxide with ECMWF's Composition-IFS

Abstract. Daily global analyses and 5-day forecasts are generated in the context of the European Monitoring Atmospheric Composition and Climate (MACC) project using an extended version of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The IFS now includes modules for chemistry, deposition and emission of reactive gases, aerosols, and greenhouse gases, and the 4-dimensional variational data assimilation scheme makes use of multiple satellite observations of atmospheric composition in addition to meteorological observations. This paper describes the data assimilation setup of the new Composition-IFS (C-IFS) with respect to reactive gases and validates analysis fields of ozone (O3), carbon monoxide (CO), and nitrogen dioxide (NO2) for the year 2008 against independent observations and a control run without data assimilation. The largest improvement in CO by assimilation of Measurements of Pollution in the Troposphere (MOPITT) CO columns is seen in the lower troposphere of the Northern Hemisphere (NH) extratropics during winter, and during the South African biomass-burning season. The assimilation of several O3 total column and stratospheric profile retrievals greatly improves the total column, stratospheric and upper tropospheric O3 analysis fields relative to the control run. The impact on lower tropospheric ozone, which comes from the residual of the total column and stratospheric profile O3 data, is smaller, but nevertheless there is some improvement particularly in the NH during winter and spring. The impact of the assimilation of tropospheric NO2 columns from the Ozone Monitoring Instrument (OMI) is small because of the short lifetime of NO2, suggesting that NO2 observations would be better used to adjust emissions instead of initial conditions. The results further indicate that the quality of the tropospheric analyses and of the stratospheric ozone analysis obtained with the C-IFS system has improved compared to the previous "coupled" model system of MACC.

Tropospheric column amount of ozone retrieved from SCIAMACHY limb–nadir-matching observations

Abstract. Tropospheric ozone (O3), has two main sources: transport from the stratosphere and photochemical production in the troposphere. It plays important roles in atmospheric chemistry and climate change. Its amount and destruction are being modified by anthropogenic activity. Global measurements are needed to test our understanding of its sources and sinks. In this paper, we describe the retrieval of tropospheric O3 columns (TOCs) from the combined limb and nadir observations (hereinafter referred to as limb–nadir-matching (LNM)) of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument, which flew as part of the payload onboard the European Space Agency (ESA) satellite Envisat (2002–2012). The LNM technique used in this study is a residual approach that subtracts stratospheric O3 columns (SOCs), retrieved from the limb observations, from the total O3 columns (TOZs), derived from the nadir observations. The technique requires accurate knowledge of the SOCs, TOZs, tropopause height, and their associated errors. The SOCs were determined from the stratospheric O3 profiles retrieved in the Hartley and Chappuis bands from SCIAMACHY limb scattering measurements. The TOZs were also derived from SCIAMACHY measurements, but in this case from the nadir viewing mode using the Weighting Function Differential Optical Absorption Spectroscopy (WFDOAS) technique in the Huggins band. Comparisons of the TOCs from SCIAMACHY and collocated measurements from ozonesondes in both hemispheres between January 2003 and December 2011 show agreement to within 2–5 DU (1 DU = 2.69 × 1016 molecules cm−2). TOC values from SCIAMACHY have also been compared to the results from the Tropospheric Emission Spectrometer (TES) and from the LNM technique exploiting Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) data (hereinafter referred to as OMI/MLS). All compared data sets agree within the given data product error range and exhibit similar seasonal variations, which, however, differ in amplitude. The spatial distributions of tropospheric O3 in the SCIAMACHY LNM TOC product show characteristic variations related to stratosphere–troposphere exchange (STE) processes, anthropogenic activities and biospheric emissions.

Propagation of radiosonde pressure sensor errors to ozonesonde measurements

Abstract. Several previous studies highlight pressure (or equivalently, pressure altitude) discrepancies between the radiosonde pressure sensor and that derived from a GPS flown with the radiosonde. The offsets vary during the ascent both in absolute and percent pressure differences. To investigate this problem further, a total of 731 radiosonde/ozonesonde launches from the Southern Hemisphere subtropics to northern mid-latitudes are considered, with launches between 2005 and 2013 from both longer term and campaign-based intensive stations. Five series of radiosondes from two manufacturers (International Met Systems: iMet, iMet-P, iMet-S, and Vaisala: RS80-15N and RS92-SGP) are analyzed to determine the magnitude of the pressure offset. Additionally, electrochemical concentration cell (ECC) ozonesondes from three manufacturers (Science Pump Corporation; SPC and ENSCI/Droplet Measurement Technologies; DMT) are analyzed to quantify the effects these offsets have on the calculation of ECC ozone (O3) mixing ratio profiles (O3MR) from the ozonesonde-measured partial pressure. Approximately half of all offsets are > ±0.6 hPa in the free troposphere, with nearly a third > ±1.0 hPa at 26 km, where the 1.0 hPa error represents ~ 5% of the total atmospheric pressure. Pressure offsets have negligible effects on O3MR below 20 km (96% of launches lie within ±5% O3MR error at 20 km). Ozone mixing ratio errors above 10 hPa (~ 30 km), can approach greater than ±10% (> 25% of launches that reach 30 km exceed this threshold). These errors cause disagreement between the integrated ozonesonde-only column O3 from the GPS and radiosonde pressure profile by an average of +6.5 DU. Comparisons of total column O3 between the GPS and radiosonde pressure profiles yield average differences of +1.1 DU when the O3 is integrated to burst with addition of the McPeters and Labow (2012) above-burst O3 column climatology. Total column differences are reduced to an average of −0.5 DU when the O3 profile is integrated to 10 hPa with subsequent addition of the O3 climatology above 10 hPa. The RS92 radiosondes are superior in performance compared to other radiosondes, with average 26 km errors of −0.12 hPa or +0.61% O3MR error. iMet-P radiosondes had average 26 km errors of −1.95 hPa or +8.75 % O3MR error. Based on our analysis, we suggest that ozonesondes always be coupled with a GPS-enabled radiosonde and that pressure-dependent variables, such as O3MR, be recalculated/reprocessed using the GPS-measured altitude, especially when 26 km pressure offsets exceed ±1.0 hPa/±5%.

Anomalies of total column CO and O<sub>3</sub> associated with great earthquakes in recent years

Abstract. Variations of total column CO and O3 in the atmosphere over the epicenter areas of 35 great earthquakes that occurred throughout the world in recent years were studied based on the hyper-spectrum data from Atmospheric Infrared Sounder (AIRS). It was found that anomalous increases of CO and/or O3 concentrations occurred over the epicenter areas of 12 earthquakes among the 35 studied ones. However, increases in both CO and O3 concentrations were found for 6 earthquakes. The O3 anomalies appeared in the month when the earthquake occurred and lasted for a few months, whereas CO anomalies occurred irregularly. The duration of CO and O3 anomalies related to the earthquakes ranged from 1 to 6 months. The anomalies of CO concentration related to the earthquake can be mainly attributed to gas emission from the lithosphere and photochemical reaction, while the anomalous increases in O3 concentration can be mainly due to the transport of O3-enriched air and photochemical reaction. However, more work needs to be done in order to understand the mechanism of the CO and O3 anomalies further.

Year-round retrievals of trace gases in the Arctic using the Extended-range Atmospheric Emitted Radiance Interferometer

Abstract. The Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) was installed at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut, Canada in October 2008. Spectra from the E-AERI provide information about the radiative balance and budgets of trace gases in the Canadian high Arctic. Measurements are taken every 7 min year-round, including polar night when the solar-viewing spectrometers at PEARL are not operated. This allows E-AERI measurements to fill the gap in the PEARL dataset during the four months of polar night. Measurements were taken year-round in 2008–2009 at the PEARL Ridge Lab, which is 610 m a.s.l. (above sea-level), and from 2011 onwards at the Zero-Altitude PEARL Auxiliary Lab (0PAL), which is at sea level 15 km from the Ridge Lab. Total columns of O3, CO, CH4, and N2O have been retrieved using a modified version of the SFIT2 retrieval algorithm adapted for emission spectra. This provides the first ground-based nighttime measurements of these species at Eureka. Changes in the total columns driven by photochemistry and dynamics are observed. Analyses of E-AERI retrievals indicate accurate spectral fits (root-mean-square residuals consistent with noise) and a 10–15% uncertainty in the total column, depending on the trace gas. O3 comparisons between the E-AERI and a Bruker IFS 125HR Fourier transform infrared (FTIR) spectrometer, three Brewer spectrophotometers, two UV-visible ground-based spectrometers, and a System D'Analyse par Observations Zenithales (SAOZ) at PEARL are made from 2008–2009 and for 2011. 125HR CO, CH4, and N2O columns are also compared with the E-AERI measurements. Mean relative differences between the E-AERI and the other spectrometers are 1–10% (14% is for the un-smoothed profiles), which are less than the E-AERI's total column uncertainties. The E-AERI O3 and CO measurements are well correlated with the other spectrometers (r > 0.92 with the 125HR). The 24 h diurnal cycle and 365-day seasonal cycle of CO are observed and their amplitudes are quantified by the E-AERI (6–12 and 46%, respectively). The seasonal variability of H2O has an impact on the retrievals, leading to larger uncertainties in the summer months. Despite increased water vapour at the lower-altitude site 0PAL, measurements at 0PAL are consistent with measurements at PEARL.

The contributions of chemistry and transport to low arctic ozone in March 2011 derived from Aura MLS observations

Stratospheric and total columns of Arctic O3 (63–90oN) in late March 2011 averaged 320 and 349 DU, respectively, 50–100 DU lower than any of the previous 6 years. We use Aura Microwave Limb Sounder (MLS) O3 observations to quantify the roles of chemistry and transport and find there are two major reasons for low O3 in March 2011: heterogeneous chemical loss and a late final warming that delayed the resupply of O3 until April. Daily vortex‐averaged partial columns in the lowermost stratosphere (p > 133 hPa) and middle stratosphere (p < 29 hPa) are largely unaffected by local heterogeneous chemistry, according to model calculations. Very weak transport into the vortex between late January and late March contributes to the observed low ozone. The lower stratospheric (LS) column (133–29 hPa, ~370–550 K) is affected by both heterogeneous chemistry and transport. Because MLS N2O data show strong isolation of the vortex, we estimate the contribution of vertical transport to LS O3 using the descent of vortex N2O profiles. Simulations with the Global Modeling Initiative (GMI) chemistry and transport model (CTM) with and without heterogeneous chemical reactions show 73 DU vortex averaged O3 loss; the loss derived from MLS O3 is 84 ± 12 DU. The GMI simulation reproduces the observed O3 and N2O with little error and demonstrates credible transport and chemistry. Without heterogeneous chemical loss, March 2011 vortex O3 would have been at least 40 DU lower than climatology due to the late final warming that did not resupply O3 until mid‐April.