Reactive Trace Gases 1

Ozone Mapping and Profiler Suite (OMPS) was launched on 28 October 2011 on board of Suomi National Polar-orbiting Partnership (SNPP) satellite. OMPS represents next generation of US ozone monitoring system. The instrument suite consists of 3 ozone sensors designed to measure total and vertical ozone distribution. The OMPS Limb Profiler (LP) sensor acquires solar radiances scattered from atmospheric limb in UV and visible spectral ranges to retrieve vertical ozone profiles from cloud top to 60 km with vertical resolution of about 2 km.  In this study we will examine the suitability of using LP profiles to continue the ozone record from GOMOS, MIPAS and SCIAMACHY-limb observation on the ENVISAT satellite. The ENVISAT mission ended in April 2012, while OMPS LP observations started in March 2012. Since the overlap between them is too short, we will use Aura MLS and ACE-FTS data, which have more than 3-year overlap with OMPS LP, as transfer standards to determine biases between LP and the ENVISAT sensors.  ACE-FTS and GOMOS are occultation instruments that use astronomical bodies to do accurate altitude registration and provide ozone profiles in number density units versus altitude coordinate. These data are particularly suitable to assess the altitude registration accuracy of OMPS-LP and SCIAMACHY.  MIPAS and MLS measure in mixing ratio versus pressure coordinate, thus the comparison with LP requires unit conversion, which involves temperature profiles. Uncertainties related to unit conversion will be accounted for in the analysis. We will use the combined ENVISAT/OMPS dataset to determine inter-annual variability and long-term changes and compare them with MLS, ACE-FTS, and nadir satellite sensors such as SBUV/2, OMI and GOME-2. For reliable detection of long-term ozone changes it is important to have several independent datasets that can be compared.

Unambiguous and persistent recovery of ozone in the Antarctic ozone hole would constitute an important landmark in stratospheric ozone research. For many decades the Antarctic ozone hole is considered one of the prime examples of both the detrimental effects of human activities on our environment and effective and successful international implementation of environmental mitigation policies.

In response to these policies the atmospheric concentrations of ozone depleting substances (ODS) are on the decline. Expectations are that signs of recovery of stratospheric ozone and ozone in the Antarctic ozone hole should become visible shortly. For the Antarctic ozone hole some success has been claimed but this has also become a matter of substantial debate. The WMO 2014 ozone assessment report does not yet claim recovery of ozone in the Antarctic ozone hole.

Traditionally, recovery has been studied by the use of multi-variate regression of long-term ozone records. However, there are many uncertainties involved in the practical application of these regressions because of implicit choices on spatiotemporal averaging of ozone (monthly/seasonal means, extension of the Antarctic vortex area).

In this talk we will introduce a novel approach for unambiguous and persistent recovery of ozone in the Antarctic ozone hole. Rather than focusing on time and area averages of total ozone columns or ozone profiles, we make use of the time evolution of the probability distribution of vertically resolved ozone in the Antarctic ozone hole. Specifically we show that in the 10-year record of MLS satellite measurements of ozone in the Antarctic ozone hole there is a significant decline in the occurrence of extremely low ozone (near 100% ozone depletion) in favor of the occurrence of low ozone (80-90% ozone depletion).

We argue that through changes in the observed probability distributions we can provide the required fingerprint for the detection of ozone recovery in the Antarctic ozone hole. Through combination with the MLS observations of primarily temperature and N2O we argue that the observed fingerprint can be attributed to the ongoing decline in ODS.

We will discuss the advantages of our method for detection and attribution over the more traditional regression techniques and briefly discuss the potential of continuation of detection and attribution of ozone changes in the light of the currently available and planned (e.g.  Sentinel 5P) satellite remote sensing capacity.

In August 2015, the Canadian-led Atmospheric Chemistry Experiment (ACE) mission will complete its twelfth year in orbit on board the SCISAT satellite.  The long lifetime of ACE has provided a valuable time series of composition measurements that contribute to our understanding of ozone recovery, climate change and pollutant emissions.  These profiles of atmospheric trace gases and aerosols provide altitude-resolved data that are necessary for understanding processes that occur at specific altitudes or over limited vertical length scales.

The SCISAT/ACE mission uses infrared and UV-visible spectroscopy to make its solar occultation measurements.  There are two instruments on board SCISAT.  The ACE Fourier Transform Spectrometer (ACE-FTS) is an infrared FTS operating between 750 and 4400 cm^-1 and the ACE-MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) is a dual UV-visible-NIR spectrophotometer which was designed to extend the ACE wavelength coverage to the 280-1030 nm spectral region.  From these measurements, altitude profiles of atmospheric trace gas species, temperature and pressure are retrieved.  In addition to the mission and instrument status, a review of current science and validation results from the ACE mission will be presented in this paper.

Dynamical, chemical and radiative coupling between the stratosphere and troposphere are among the important processes that must be understood for prediction of global trends, including climate change. However, the upper troposphere and lower stratosphere (UTLS) region is difficult for exploration from space. For limb-viewing satellite measurements, retrievals in UTLS are challenging due to relatively low signal-no-noise ratio and presence of clouds.

In this work, we compare the spatio-temporal distributions and variations of the ozone field in the UTLS obtained from the limb instruments participating in the ESA Climate Change Initiative for Ozone (Ozone_cci): MIPAS, SCIAMACHY and GOMOS on Envisat, OSIRIS on Odin, ACE-FTS on SCISAT. We study seasonal variations, probability density functions, influence of Asian Summer Monsoon on UTLS ozone.

The observational distributions by Ozone_cci instruments are generally in good agreement. This similarity provides confidence of the observed patterns and allows creating Level 3 datasets and parameters, which can be useful for validation of chemistry climate models.

Numerous vertical ozone profile data records collected over the past decades from space-based platforms have the potential to allow the ozone and climate communities to tackle a variety of research questions. A prime topic is the study and documentation of long-term changes in the vertical distribution of atmospheric ozone, as targeted by the recent SPARC/IO3C/IGACO-O3/NDACC Initiative (SI2N) and WMO’s ozone assessment. Such studies typically require data records with documented mutual consistency in terms of bias and long-term stability. Ground-based networks play a pivotal role in evaluating which satellite records comply with end-user requirements and are fit for their purpose. They provide high-quality, independent measurements on a pseudo-global scale from the ground up to the stratosphere.

Here, we present an assessment of the long-term stability and mutual consistency of fourteen limb/occultation ozone profile data records, using NDACC/GAW/SHADOZ ozonesonde and NDACC lidar network data as reference standards. We show how a harmonized analysis framework and robust statistical methods allow us to derive reliable estimates of the drift, bias, and short-term variability of each satellite data record. We examine the dependence of these parameters on altitude and, whenever feasible, on latitude and season. The analysis is furthermore performed in four different ozone profile representations, as it turns out that auxiliary data used for unit and representation conversions can impact data quality. We discuss the mutual consistency  and compliance of satellite data sets with respect to specific user requirements from GCOS and from climate research groups. We conclude by reflecting on the implication of our results for trend assessments on recently merged ozone profile records (Ozone_CCI, GOZCARDS, SWOOSH, ...)

MIPAS measurements on ENVISAT represent a unique database for the study of atmospheric composition and of the time variation of atmospheric constituents.

For trend studies it is important that instrumental drifts are reduced. Some of the MIPAS spectral bands are affected by time-dependent non-linearity that have been recently corrected.

In addition to this non-linearity correction, the forthcoming new version of MIPAS products (Version 7) contains several other improvements: a new approach for handling continuum leading to a more stable retrieval, a new selection of spectral intervals for the analysis of the full resolution measurements aiming to reduce the bias between full resolution and optimized resolution measurements, the regularization of the H₂O profiles. Furthermore, the implementation of the retrieval of five new species (HCFC-22, CFC-14, HCN, COF₂, CCl₄) leads to a total of 15 species in ESA products.

The latest improvements implemented in the ESA processor, the results of the validation of the products and some preliminary results on the trend of some ozone depleting substances will be presented and discussed.