Trace Gases in the Stratosphere & Missions

WMO/UNEP Scientific Assessments of Ozone Depletion require accurate evaluations of long-term ozone trends and their uncertainty and attribution. Detailed studies of observations and model data allow to evaluate the success of the Montreal Protocol with regards to the recovery of the ozone layer and to make realistic projections of atmospheric ozone into the next decades. The 2014 Ozone Assessment concluded that observations showed a statistically significant recovery in the upper stratosphere. In 2015, the SI2N initiative reported –based on different data records and different analysis methods and assumptions– that upper stratospheric recovery was not necessarily significant. This apparent tension inspired a new coordinated activity endorsed by SPARC, IO3C and WMO (GAW) named LOTUS (Long-term Ozone Trends and Uncertainties in the Stratosphere). It aimed primarily at gathering the profile ozone community to reach a wide consensus on the significance of stratospheric ozone trends prior to the 2018 Ozone Assessment. LOTUS succeeded in this goal, taking advantage of state-of-the-art profile ozone Climate Data Records and chemistry-climate models and analysis tools to not only estimate ozone trends but also to establish best practices for data handling/merging and for regression analyses. We present the methodologies applied for this effort and summarize the main conclusions related to stratospheric ozone recovery between 2000 and 2016. We also look forward and emphasize lessons learned by LOTUS and in particular the challenges for ozone CDR developers and providers such as ESA’s Climate Change Initiative and EC’s Copernicus Climate Change Service.

The instrument FORUM  (Far-infrared Outgoing Radiation Understanding and Monitoring), has been selected to compete for the next Earth Explorer 9 mission. The primary goal of the FORUM mission is the characterization of the Outgoing Longwave Radiation in the far-infrared and in the middle infrared regions, from 100 to 1600 cm^-1. During the preparatory stage of the proposal, several studies have been performed to address the capability of the proposed instrument to provide information on important climate variables like surface temperature and emissivity, vertical distributions of  humidity, Temperature, trace gases,  and ice clouds. Here we summarize the results of these sensitivity studies.

ALTIUS is a limb sounder mission for the monitoring of the distribution and evolution of stratospheric ozone at high vertical resolution in support of operational services and long term trend monitoring. The ALTIUS mission will provide detailed stratospheric ozone profiles information at high vertical resolution, which adds valuable information to total column ozone used for data assimilation systems by operational centres based on nadir sounders.

The ALTIUS data will also be of high importance for the atmospheric modelling community, for use as input to climate models and their validation. It will reduce a gap in high-resolution limb observation data. It has the potential to contribute to the GCOS (Global Climate Observing System) ozone profile ECV (Essential Climate Variable). Off-line ALTIUS products are relevant for the validation of the Copernicus Atmosphere Monitoring Service (CAMS) model.

The preparation and implementation of the design, development, and validation phases (B2/C/D) of ALTIUS are currently being performed as part of the ALTIUS Element in the Earth Watch Programme with participation of Belgium, Canada, Luxembourg and Romania. The activities of this ALTIUS Earth Watch Element will end with the successful conclusion of the ALTIUS Flight Acceptance Review of the Space Segment and the Ground Segment Acceptance Review, with the following objectives:

The development, manufacturing, testing and calibration of the ALTIUS space segment up to and including demonstration of flight readiness at the Flight Acceptance Review,

The development, implementation, preparation and acceptance of the ALTIUS Ground Segment, consisting of the flight operations centre, the Payload Data Ground Segment and acquisition stations up to and including the Ground Segment Acceptance Review,

The confirmation and verification of the end-to-end mission performance, including development of required simulators,

The identification of launcher opportunities, selection of target launcher and management of the launcher interface to the level needed to ensure compatibility of the ALTIUS space segment with the target launcher.

Launch, in-orbit commission and routine operation are subject of a future project proposal to be approved by the participating states.

A Mission Advisory Group (MAG) has been established with independent advisors from data users and scientific institutes to advice the project team.

The paper will present the details of the Project, its implementation and status.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that operated from 2002 to 2012 onboard the ENVISAT satellite. The maintenance and the upgrade of both L1 and L2 ESA processors are accomplished by the Quality Working Group, where a fruitful collaboration among Level 1, Level 2 and validation teams can be exploited. Recently both ESA L1 and L2 processors have been updated, as well as the spectroscopic database and some absorption cross-sections. In addition to the products already present in the current release (V7) of ESA MIPAS data (temperature and the VMR of H₂O, O₃, HNO₃, CH₄, N₂O, NO₂, CFC-11, CFC-12, N₂O₅, ClONO₂, HCFC-22, COF₂, CF₄, HCN and CCl₄), the VMR of six additional species (OCS, CH₃Cl, HDO, C₂H₂, C₂H₆, COCl₂) will be provided in V8 dataset. In preparation of V8 full mission reprocessing, three Diagnostic Datasets have been generated to check the performances of all L1, L2 processors and the new auxiliary data.

The analysis of these Diagnostic Datasets and the comparison with previous full mission dataset V7 will be used to perform a first assessment of the quality of the new V8 products. In the paper special focus will be given to the new species.

Over the past decades, the increasing capabilities of Earth observation (EO) satellites have unleashed opportunities for improved global observations of key parameters governing Earth system processes. However, the full scientific exploitation of this capability requires continued efforts both to bring observational products to full maturity and to develop suitable Earth-system models that can help with the exploitation of the available data sets. Enhanced collaboration between the modelling and observing communities are thereby key to the success of these endeavours. The World Climate Research Programme’s SPARC and Future Earth’s IGAC core projects seek to foster such collaboration and advance our knowledge of chemistry-climate interactions in the stratosphere and the troposphere based on both models and observations. Some examples are shown from ESA/SPARC’s SPIN collaboration, the SPARC Data Initiative, the SPARC Chemistry-Climate Model Initiative, and the new ESA Water_Vapour_cci to illustrate the potential of such approaches.