Vertical Distribution Of Ozone Research Articles

A re-evaluated Canadian ozonesonde record: measurements of the vertical distribution of ozone over Canada from 1966 to 2013

Abstract. In Canada routine ozone soundings have been carried at Resolute Bay since 1966, making this record the longest in the world. Similar measurements started in the 1970s at three other sites, and the network was expanded in stages to 10 sites by 2003. This important record for understanding long-term changes in tropospheric and stratospheric ozone has been re-evaluated as part of the SPARC/IO3C/IGACO-O3/NDACC (SI2N) initiative. The Brewer–Mast sonde, used in the Canadian network until 1980, is different in construction from the electrochemical concentration cell (ECC) sonde, and the ECC sonde itself has also undergone a variety of minor design changes over the period 1980–2013. Corrections have been made for the estimated effects of these changes to produce a more homogeneous data set. The effect of the corrections is generally modest. However, the overall result is entirely positive: the comparison with co-located total ozone spectrometers is improved, in terms of both bias and standard deviation, and trends in the bias have been reduced or eliminated. An uncertainty analysis (including the additional uncertainty from the corrections, where appropriate) has also been conducted, and the altitude-dependent estimated uncertainty is included with each revised profile. The resulting time series show negative trends in the lower stratosphere of up to 5 % decade−1 for the period 1966–2013. Most of this decline occurred before 1997, and linear trends for the more recent period are generally not significant. The time series also show large variations from year to year. Some of these anomalies can be related to cold winters (in the Arctic stratosphere) or changes in the Brewer–Dobson circulation, which may thereby be influencing trends. In the troposphere, trends for the 48-year period are small and for the most part not significant. This suggests that ozone levels in the free troposphere over Canada have not changed significantly in nearly 50 years.

Remote Sensing and Atmosphere

The intensities observed along nadiar at the top of atmosphere as a function of solar zenith angle for ƛ = 0.55 micron, haze o refractive index m = 1.50 – 0.031 and aerosols distributed over 0.03 to 10 micron range. As the solar zenith angle increases, the increases in effective atmosphericpath leads to decrease in intensity – approaching to zero a solar zenith of 90. The rate of decrease of intensity with solar zenith angle is more for higher values of reflectivity. The variation with the solar zenith angle at the top of the atmosphere of upward – travelling radiance for each of the lands at bands as seen at an altitude of 45.538 for a surface reflectivity of 0.2. this uses an atmospheric model based on the vertical distribution and content of ozone, aerosol and water vapour for an average mid-latitude summer. Atmosphere.since the solar flux is highest in the spectral interval 0.5-0.6 micron, the upward radiance received by that hand is higher than any other band. Also as the solar zenith angle increases, the upward radiance diminishes as expected because of the added path length through which the solar flux must pass.

Lidar Measurements of Ozone in the Upper Troposphere – Lower Stratosphere at Siberian Lidar Station in Tomsk

The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors.

Instantaneous longwave radiative impact of ozone: an application on IASI/MetOp observations

Abstract. Ozone is an important greenhouse gas in terms of anthropogenic radiative forcing (RF). RF calculations for ozone were until recently entirely model based, and significant discrepancies were reported due to different model characteristics. However, new instantaneous radiative kernels (IRKs) calculated from hyperspectral thermal IR satellites have been able to help adjudicate between different climate model RF calculations. IRKs are defined as the sensitivity of the outgoing longwave radiation (OLR) flux with respect to the ozone vertical distribution in the full 9.6 μm band. Previous methods applied to measurements from the Tropospheric Emission Spectrometer (TES) on Aura rely on an anisotropy approximation for the angular integration. In this paper, we present a more accurate but more computationally expensive method to calculate these kernels. The method of direct integration is based on similar principles to the anisotropy approximation, but it deals more precisely with the integration of the Jacobians. We describe both methods and highlight their differences with respect to the IRKs and the ozone longwave radiative effect (LWRE), i.e., the radiative impact in OLR due to absorption by ozone, for both tropospheric and total columns, from measurements of the Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp-A. Biases between the two methods vary from −25 to +20 % for the LWRE, depending on the viewing angle. These biases point to the inadequacy of the anisotropy method, especially at nadir, suggesting that the TES-derived LWREs are biased low by around 25 % and that chemistry–climate model OLR biases with respect to TES are underestimated. In this paper we also exploit the sampling performance of IASI to obtain first daily global distributions of the LWRE, for 12 days (the 15th of each month) in 2011, calculated with the direct integration method. We show that the temporal variation of global and latitudinal averages of the LWRE shows patterns which are controlled by changes in the surface temperature and ozone variation due to specific processes, such as the ozone hole in the polar regions and stratospheric intrusions into the troposphere.

The direct fitting approach for total ozone column retrievals: a sensitivity study on GOME-2/MetOp-A measurements

Abstract. We present a sensitivity study of the direct fitting approach to retrieve total ozone columns from the clear sky Global Ozone Monitoring Experiment 2/MetOp-A (GOME-2/MetOp-A) measurements between 325 and 335 nm in the period 2007–2010. The direct fitting of the measurement is based on adjusting the scaling of a reference ozone profile and requires accurate simulation of GOME-2 radiances. In this context, we study the effect of three aspects that introduce forward model errors if not addressed appropriately: (1) the use of a clear sky model atmosphere in the radiative transfer demanding cloud filtering, (2) different approximations of Earth's sphericity to address the influence of the solar zenith angle, and (3) the need of polarization in radiative transfer modeling. We conclude that cloud filtering using the operational GOME-2 FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A band) cloud product, which is part of level 1B data, and the use of pseudo-spherical scalar radiative transfer is fully sufficient for the purpose of this retrieval. A validation with ground-based measurements at 36 stations confirms this showing a global mean bias of −0.1 % with a standard deviation (SD) of 2.7 %. The regularization effect inherent to the profile scaling approach is thoroughly characterized by the total column averaging kernel for each individual retrieval. It characterizes the effect of the particular choice of the ozone profile to be scaled by the inversion and is part of the retrieval product. Two different interpretations of the data product are possible: first, regarding the retrieval product as an estimate of the true column, a direct comparison of the retrieved column with total ozone columns from ground-based measurements can be done. This requires accurate a priori knowledge of the reference ozone profile and the column averaging kernel is not needed. Alternatively, the retrieval product can be interpreted as an effective column defined by the total column averaging kernel. This interpretation relies much less on the a priori knowledge of the reference ozone profile; however, for its validation, measurements of the vertical ozone distribution are needed. The different manners of data interpretation are demonstrated for simulated and real measurements using on-ground ozone column and ozonesonde measurements for validation.

Optimization of the GSFC TROPOZ DIAL retrieval using synthetic lidar returns and ozonesondes – Part 1: Algorithm validation

Abstract. The main purpose of the NASA Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) is to measure the vertical distribution of tropospheric ozone for science investigations. Because of the important health and climate impacts of tropospheric ozone, it is imperative to quantify background photochemical ozone concentrations and ozone layers aloft, especially during air quality episodes. For these reasons, this paper addresses the necessary procedures to validate the TROPOZ retrieval algorithm and confirm that it is properly representing ozone concentrations. This paper is focused on ensuring the TROPOZ algorithm is properly quantifying ozone concentrations, and a following paper will focus on a systematic uncertainty analysis. This methodology begins by simulating synthetic lidar returns from actual TROPOZ lidar return signals in combination with a known ozone profile. From these synthetic signals, it is possible to explicitly determine retrieval algorithm biases from the known profile. This was then systematically performed to identify any areas that need refinement for a new operational version of the TROPOZ retrieval algorithm. One immediate outcome of this exercise was that a bin registration error in the correction for detector saturation within the original retrieval was discovered and was subsequently corrected for. Another noticeable outcome was that the vertical smoothing in the retrieval algorithm was upgraded from a constant vertical resolution to a variable vertical resolution to yield a statistical uncertainty of <10 %. This new and optimized vertical-resolution scheme retains the ability to resolve fluctuations in the known ozone profile, but it now allows near-field signals to be more appropriately smoothed. With these revisions to the previous TROPOZ retrieval, the optimized TROPOZ retrieval algorithm (TROPOZopt) has been effective in retrieving nearly 200 m lower to the surface. Also, as compared to the previous version of the retrieval, the TROPOZopt had an overall mean improvement of 3.5 %, and large improvements (upwards of 10–15 % as compared to the previous algorithm) were apparent between 4.5 and 9 km. Finally, to ensure the TROPOZopt retrieval algorithm is robust enough to handle actual lidar return signals, a comparison is shown between four nearby ozonesonde measurements. The ozonesondes are mostly within the TROPOZopt retrieval uncertainty bars, which implies that this exercise was quite successful.

Algorithm for retrieval of vertical distribution of ozone from DIAL laser remote measurements

We present an algorithm for retrieval of vertical distribution of ozone with temperature and aerosol correction during DIAL lidar sounding of the atmosphere. Most suitable wavelengths for measurements of ozone profiles in the upper troposphere--lower stratosphere are selected. Results of lidar measurement at wavelengths of 299 and 341 nm agree with model estimates, which point to acceptable accuracy of ozone sounding in the 6---18 km altitude range.

Comparison and merging of ozone profile data from various measurement techniques at NDACC Alpine station

Within the Network for the Detection of Atmospheric Composition Changes (NDACC), various remote sensing techniques are used in addition to in situ ozone sounding measurements for the long-term evaluation of the ozone vertical distribution. These techniques, using e.g. microwave spectrometers, Fourier Transform Infrared spectrometers or laser radiation (lidars), are very different in terms of vertical distribution, time sampling and precision, which can present some difficulties for the validation of satellite data or the products of the European Monitoring atmospheric composition & climate Service (MACC). A methodology was developed for the integration of profile ozone data from various sources in order to provide consistent ozone vertical distribution time series as well as tropospheric and stratospheric ozone partial columns. This methodology was developed for measurements performed in the stations forming the Alpine station (e.g. Haute-Provence Observatory OHP – France, Bern – Switzerland, Jungfraujoch – Switzerland). Ozone measurements from the ozone DIAL lidar instrument and ozone sondes at OHP, the microwave spectrometer at Bern and the FTIR spectrometer at the Jungfraujoch station were used for this purpose.

Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends

Abstract. Trends in the vertical distribution of ozone are reported and compared for a number of new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere (as measured by equivalent effective stratospheric chlorine – EESC) was maximised in the second half of the 1990s. We examine the periods before and after the peak to see if any change in trend is discernible in the ozone record that might be attributable to a change in the EESC trend, though no attribution is attempted. Prior to 1998, trends in the upper stratosphere (~ 45 km, 4 hPa) are found to be −5 to −10 % per decade at mid-latitudes and closer to −5 % per decade in the tropics. No trends are found in the mid-stratosphere (28 km, 30 hPa). Negative trends are seen in the lower stratosphere at mid-latitudes in both hemispheres and in the deep tropics. However, it is hard to be categorical about the trends in the lower stratosphere for three reasons: (i) there are fewer measurements, (ii) the data quality is poorer, and (iii) the measurements in the 1990s are perturbed by aerosols from the Mt Pinatubo eruption in 1991. These findings are similar to those reported previously even though the measurements for the main satellite and ground-based records have been revised. There is no sign of a continued negative trend in the upper stratosphere since 1998: instead there is a hint of an average positive trend of ~ 2 % per decade in mid-latitudes and ~ 3 % per decade in the tropics. The significance of these upward trends is investigated using different assumptions of the independence of the trend estimates found from different data sets. The averaged upward trends are significant if the trends derived from various data sets are assumed to be independent (as in Pawson et al., 2014) but are generally not significant if the trends are not independent. This occurs because many of the underlying measurement records are used in more than one merged data set. At this point it is not possible to say which assumption is best. Including an estimate of the drift of the overall ozone observing system decreases the significance of the trends. The significance will become clearer as (i) more years are added to the observational record, (ii) further improvements are made to the historic ozone record (e.g. through algorithm development), and (iii) the data merging techniques are refined, particularly through a more rigorous treatment of uncertainties.

Vertical distribution of ozone over a tropical station: Seasonal variation and comparison with satellite (MLS, SABER) and ERA-Interim products

In the present study, vertical distribution of ozone observed using ozonesonde measurements obtained during 2010–2014 from a tropical station Gadanki (13.48°E, 79.18°E) is presented with special emphasis on the variability within the atmospheric boundary layer (ABL), in the free troposphere and in the lower stratosphere. In general, a clear semi-annual oscillation in ozone is seen within ABL and free-troposphere with peak during pre- and post-monsoon seasons. Whereas annual oscillation with peak during monsoon season dominates in the lower stratosphere. Interestingly, there is a delay of one month in the peak in the ozone mixing ratio (OMR) in the free troposphere when compared to the ABL during pre-monsoon and these features are quite different compared to other stations in the Indian region. One of the main objectives of the present study is to examine how well the present satellite (MLS and SABER) and re-analysis (ERA-Interim) ozone data sets represent the variability of ozone over the tropical station. In general, MLS and ERA-Interim overestimate the OMR by 97% and 80%, respectively, near the tropical tropopause, in comparison with ozonesonde data. Thus, caution is to be exercised in using these data sets for investigating the stratosphere–troposphere exchange (STE) process. However, all the three data sets show very good agreement with ozonesonde measurements above 22.5 km. ERA-Interim data set is found to agree well in the free troposphere but not in the ABL. Interestingly, the ozone tropopause is found to be more associated with the convective outflow level than cold point tropopause height. Back trajectory analysis reveals that the observed ozone in the troposphere over Gadanki region is mostly transported from the western region and from the higher altitudes. These features are discussed in the light of current understanding of the generation and transport of the ozone in the troposphere.

The Influence of ENSO on Northern Midlatitude Ozone during the Winter to Spring Transition

Abstract The influence of El Niño–Southern Oscillation (ENSO) on northern midlatitude ozone during the period January–March (JFM) is investigated using various observations and a chemistry–climate model. The analysis reveals that, during El Niño events, there are noticeable anomalously high total ozone column (TOC) values over the North Pacific, the southern United States, northeastern Africa, and East Asia but anomalously low values in central Europe and over the North Atlantic. La Niña events have almost the opposite effects on TOC anomalies. The longitudinal dependence of midlatitude ozone anomalies associated with ENSO events during the period JFM is found to be related to planetary waves. Planetary waves excited by tropical convection propagate into the middle latitudes and give rise to longwave trains (Pacific–North American pattern) and shortwave trains along the North African–Asian jet. These wave trains affect ozone in the upper troposphere and lower stratosphere (UTLS) by modulating the midlatitude tropopause height and cause TOC anomalies by changing the vertical distributions of ozone. In addition, synoptic-scale Rossby wave breaking increases on the poleward flanks of the enhanced westerly jet during El Niño events, leading to a stronger eddy-driven meridional circulation in the UTLS and hence causing TOC increases over the North Pacific, the southern United States, northeastern Africa, and East Asia and vice versa for La Niña events. It is also found that the contribution of changes in Brewer–Dobson circulation due to anomalous planetary wave dissipation in the stratosphere during ENSO events to TOC changes in the middle latitudes for the period JFM is small, not more than 1 Dobson unit (DU) per month.

ATMOSPHERIC OZONE PROFILES DURING VASYLKIV OIL BURNING EPISODE

Ground-based Fourier Transform Infrared spectrometer (FTIR) observations have been used for study stratosphere/troposphere ozone vertical distribution during Vasylkiv (near Kyiv, Ukraine) incident of petroleum storage burning in June 8–14, 2015.

SMILES observations of mesospheric ozone during the solar eclipse

AbstractThe Superconducting Submillimeter‐Wave Limb‐Emission Sounder (SMILES) successfully observed vertical distributions of ozone (O3) concentration in the middle atmosphere during the annular solar eclipse that occurred on 15 January 2010. In the mesosphere, where the photochemical lifetime of O3 is relatively short (approximately 100 s), altitude‐dependent changes in O3 concentration under reduced solar radiation and their temporal variations were clearly observed as a function of the eclipse obscuration. This study reports the vertical distributions of mesospheric O3 during a solar eclipse event and analyzes theoretically the eclipse‐induced changes. We show that simple analytical expressions for O3 concentration, which assume that O3 and O are in a photochemically steady state, can be used to describe the O3 concentration under reduced solar radiation. The SMILES data obtained during the eclipse provide a unique opportunity to test our current understanding of mesospheric O3 photochemistry.

Transport effects on the vertical distribution of tropospheric ozone over western India

AbstractIn situ tropospheric ozone measurements by balloon‐borne electrochemical concentration cell (ECC) sensors above Ahmedabad in western India from May 2003 to July 2007 are presented, along with an analysis of the transport processes responsible for the observed vertical ozone distribution. This analysis is supported by 12 day back trajectory calculations using the FLEXPART Lagrangian particle dispersion model. Lowest ozone (~20 ppbv) is observed near the surface during September at the end of the Asian summer monsoon season. Average midtropospheric (5–10 km above sea level) ozone is greatest (70–75 ppbv) during April–June and lowest (40–50 ppbv) during winter. Ozone variability is greatest in the upper troposphere with higher ozone during March–May. The FLEXPART retroplume results show that the free tropospheric vertical ozone distribution above this location is affected by long‐range transport from the direction of North Africa and North America. Ozone levels are also affected by transport from the stratosphere particularly during March–April. The lower tropospheric (<3 km) ozone distribution during the Asian summer monsoon is affected by transport from the Indian Ocean via the east coast of Africa and the Arabian Sea. Influence from deep convection in the upper troposphere confined over central Asia has been simulated by FLEXPART. Lower ozone levels are observed during August–November than in any other season at 10–14 km above sea level. These in situ observations are in contrast to other studies based on satellite data which show that the lowest ozone values at these altitudes occur during the Asian summer monsoon.

On sampling uncertainty of satellite ozone profile measurements

Abstract. Satellite measurements sample continuous fields of atmospheric constituents at discrete locations and times. However, insufficient or inhomogeneous sampling, if not taken into account, can result in inaccurate average estimates and even induce spurious features. We propose to characterize the spatiotemporal inhomogeneity of atmospheric measurements by a measure, which is a linear combination of the asymmetry and entropy of a sampling distribution. It is shown that this measure is related to the so-called sampling uncertainty, which occurs due to non-uniform sampling patterns. We have estimated the sampling uncertainty of zonal mean ozone profiles for six limb-viewing satellite instruments participating in the European Space Agency Ozone Climate Change Initiative project using the high-resolution ozone field simulated with the FinROSE chemistry-transport model. It is shown that the sampling uncertainty for the instruments with coarse sampling is not negligible and can be as large as a few percent. It is found that the standard deviation of the sampling uncertainty in the monthly zonal mean data allows for a simple parameterization in terms of the product of the standard deviation of natural variations and the proposed inhomogeneity measure. The sampling uncertainty estimates improve the uncertainty quantification and can be used in comprehensive data analyses. The focus of this work is the vertical ozone distributions measured by limb-viewing satellite instruments, but the developed methods can also be applied to different satellite, ground-based and in situ measurements.

Observing trends in total ozone and extreme ozone events

The ozone layer in the stratosphere has been recovering since the 1989 Montreal Protocol reduced the use of ozone‐destroying chlorofluorocarbons. Fitzka et al. observed trends in total ozone levels and the vertical distribution of ozone at Hoher Sonnblick, a mountain in Austria, from 1994 to 2011.

Ozone ProfilE Retrieval Algorithm (OPERA) for nadir-looking satellite instruments in the UV–VIS

Abstract. For the retrieval of the vertical distribution of ozone in the atmosphere the Ozone ProfilE Retrieval Algorithm (OPERA) has been further developed. The new version (1.26) of OPERA is capable of retrieving ozone profiles from UV–VIS observations of most nadir-looking satellite instruments like GOME, SCIAMACHY, OMI and GOME-2. The setup of OPERA is described and results are presented for GOME and GOME-2 observations. The retrieved ozone profiles are globally compared to ozone sondes for the years 1997 and 2008. Relative differences between GOME/GOME-2 and ozone sondes are within the limits as specified by the user requirements from the Climate Change Initiative (CCI) programme of ESA (20% in the troposphere, 15% in the stratosphere). To demonstrate the performance of the algorithm under extreme circumstances, the 2009 Antarctic ozone hole season was investigated in more detail using GOME-2 ozone profiles and lidar data, which showed an unusual persistence of the vortex over the Río Gallegos observing station (51° S, 69.3° W). By applying OPERA to multiple instruments, a time series of ozone profiles from 1996 to 2013 from a single robust algorithm can be created.

Variations of the vertical ozone distribution over Moscow during sudden stratospheric warming in winter 2012–2013

The new results of remote sensing of atmospheric ozone over the Moscow region in the cold half-year of 2012–2013, including the period of major sudden stratospheric warming are presented. Methods for analyzing the results of observation of the vertical ozone distribution, obtained using spectral equipment operating at the frequencies of the ozone rotational line with a center at 142.175 GHz, are described. The features of the time series of the vertical stratospheric ozone distribution before, during, and after a strong disturbance of the stratospheric dynamics in January 2013 are considered. The data are compared with ozone observations during the period of previous major stratospheric warming in 2009–2010. The considered year to year differences and the diversity of the features of the dynamic processes affecting the vertical ozone distribution point to the importance of further monitoring of atmospheric ozone, which is necessary to develop numerical climate models and to predict the ozonosphere and climate evolution.

Evidence of a LNOX influence on middle/upper troposphere ozone‐mixing ratios at Dakar, Senegal during Northern Hemisphere summer season

AbstractWe present results for the vertical distribution of tropospheric ozone from 40 measurements at Dakar, Senegal (14.59°N, 17.5°W) from June to September of 2008, 2010, 2011 and 2012. Under pre‐monsoon conditions (June), many dry air intrusions are found in the lower troposphere transitioning to humid conditions during July, August and September. Measurements show the highest ozone‐mixing ratios (50–100 ppb) in the 400–200 hPa layer and easterly wind flow during each month. Lightning‐NOX (LNOX) is the only viable source to explain the vertical distribution of ozone, with a large amount of upstream lightning over West Africa during summer.

Long Term Variation in the Vertical Distribution of Tropospheric Ozone in India

The seasonal, interannual and decadal variance in tropospheric ozone levels has been examined at three Indian cities: New Delhi, Pune and Thiruvananthapuram over the period from 1970 - 2009 using ozonesonde data. It is observed that the tropospheric ozone levels have not changed monotonically in a single direction over these years and the observed changes in ozone levels is a mixture of countervailin g signals from both natural and anthropogenic factors. In general, the ozone concentration in the lower troposphere at all these stations is high during winter, decreases throughout summer reaching a minimum during monsoon and increases thereafter during post monsoon. For most part of the year, the ozone concentration in the lower troposphere is highest at Delhi followed by Pune and lowest at Thiruvananthapuram, while in the middle and upper troposphere it is highest at Delhi followed by Thiruvananthapuram and lowest at Pune. Linear trend of ozone partial pressure at different altitudes indicates that the maximum decreasing trend occurs around 10–13 km altitude. This altitude is observed to increase with increase in latitude.