Reactive Trace Gases 4

In addition to the nominal routine observations of the lower atmosphere (6-70 km), MIPAS also observed the middle and upper atmosphere using the special modes of Middle Atmosphere (MA, 18-102 Km), Upper Atmosphere (UA, 42-172 Km) and Noctilucent Clouds (NLC, 42-102 Km). Observations in these modes were taken regularly (1 out of 5 days) since mid-2007 until the failure of Envisat in April 2012. The wide spectral range, high spectral resolution and high sensitivity allowed MIPAS to measure many species in the middle atmosphere with large sensitivity including, temperature, and O3, H2O, CH4, N2O, NO2, NO, CO, and CO2 concentrations. The inversion of these quantities in those regions required, however, a complex retrieval algorithm that needs to incorporate non-(local thermodynamic equilibrium) effects.

In this work we present some results of recent analysis of this dataset carried out by comparing with other instruments (e.g. SABER and ACE) and 3D model simulations of WACCM. In particular we plan to cover, the solar cycle effects on mesospheric temperature; the nighttime ozone variability in the high latitude winter mesosphere, and the COx (CO+CO2) solar cycle and trends in the mesosphere and lower thermosphere.

In the dark polar winter, increases in N₂O concentrations in the upper stratosphere and lower mesosphere have been observed and attributed to solar proton events and energetic particle precipitation. It has been suggested that the N₂O production occurs at higher altitudes and descends into the upper stratosphere, where it can then be converted into NO_x and play a role in the catalytic destruction of O₃. This study will present ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) N₂O measurements and climatologies throughout the atmosphere, from the stratosphere to the lower thermosphere. The ACE-FTS measurements show that in the polar-regions in the lower thermosphere there is a continuous source of N₂O production that is highly correlated to the Ap index (a proxy for geomagnetic activity). From year to year, the Arctic summer ACE-FTS N₂O measurements are fairly consistent. However, the Arctic winter measurements in the middle atmosphere are highly dependent on the local dynamics. The ACE-FTS measurements and variations in the upper stratosphere will be compared to correlative N₂O data from the satellite instruments MIPAS and MLS. We will investigate the possible sources and sinks of N₂O in the upper atmosphere and quantify the effect its descent into the stratosphere has on stratospheric NO_x and O₃ concentrations.

At the end of 2014 ESA launched a study called ‘Operoz’  with the aim to exactly define what would be needed in terms of an operational capacity for long-term ozone profile monitoring at high vertical resolution. Here we present the results of the ESA study and ask for feedback from the ESA atmosphere community.

Over the years several internationally coordinated strategic documents (e.g. GCOS, WCRP-SPARC, CEOS, ESA Convoy, as well as other frameworks)  have made reference to an upcoming  ‘Limb Gap’ . This ‘Limb Gap’ refers to a lack of planned limb observations of ozone as well as other atmospheric constituents after more than two decades with multiple satellite missions using limb view including UARS(1991-2005; HALOE, CLAES, MLS), ERBS (1984-2005; Sage-II), Envisat (2001-2012; MIPAS, SCIAMACHY, GOMOS), Scisat (2003 - present; ACE-FTS, Maestro) EOS-Aura (2004-present; HIRDLS, MLS) and Odin(2001-present; OSIRIS, SMR).

Since 2012 the US-based Suomi-NPP mission carries the OMPS instrument which combines ozone measurements in nadir and limb viewing modes. OMPS can be considered as the first operational limb sounder for ozone profiling. A  successor for the OMPS limb component is planned on JPSS-2 (2022+). In Europe there is a need to better define the required limb capacity on top of the planned Copernicus Space Segment including Sentinel 4, 5 and 5p for nadir-based ozone monitoring.

In this presentation the three basic questions that have been addressed in Operoz are covered: (i) Why do we need operational limb monitoring of ozone profiles on top of the operational nadir sounders (mission objectives), (ii) What do we need to observe exactly (observational requirements), and (iii) how could a compliant limb capacity be envisaged (reality check)?

The answers from the Operoz project on these three questions will be presented together with concrete recommendations for a small to medium size space mission targeting global ozone profiles at high vertical resolution. The mission objectives relate to (i) operational ozone services as part of the Copernicus Atmospheric Monitoring Service and (ii) long-term ozone (trend) monitoring. Additional mission objectives for an operational mission using limb geometry have also been suggested in Operoz. The observational requirements will be presented for potential specific mission extensions on top of a minimum mission for long-term ozone profile monitoring using limb view.

Solar, auroral, and radiation belt electrons and soft solar X-rays produce nitric monoxide (NO) in the mesosphere and lower thermosphere (MLT, 50--150 km). Thus, the NO content in this atmospheric region reveals how solar activity and variability impacts the atmospheric composition. NO downward transport during polar winters then influences the lower atmosphere, in particular by catalytically depleting ozone. This in turn changes the heating and cooling rates and eventually the atmospheric circulation.

We present an overview and comparison of satellite measurements of NO in the MLT region. Results are shown for the data from ACE-FTS, MIPAS, SCIAMACHY, and SMR. MIPAS and SCIAMACHY are on board the now defunct ESA satellite Envisat and measured from July 2002 until April 2012. SMR is on board the Swedish-led satellite and ESA third-party mission Odin, still delivering data since October 2003. ACE-FTS is on board the Canadian satellite SCISAT-1 and is also still delivering data since February 2004. MIPAS, SCIAMACHY, and SMR are limb sounders and provide global data, however, the MLT region was only scanned at selected days. ACE-FTS is a solar occultation instrument which provides almost daily coverage of the atmosphere up to 120 km, but only at a limited number of latitudes.

We compare the daily zonal mean NO data of the four instruments in the MLT region. In addition to the MLT scans from SCIAMACHY, we present the results from its nominal scans (0--90 km). These are daily data from 08/2002 until 04/2012 and useful up to 80 km. We find that the data are consistent and valuable for further evaluating the chemistry and dynamics in the middle atmosphere.

Having established a consistent data set, we can use it to extract solar and geomagnetic forcing parameters with different statistical approaches. With the derived parameters, we aim to build a simple model of the NO content in the mesosphere driven by solar and geomagnetic activity. Eventually, this helps improving models of solar variability in climate and chemistry-climate models.

SCIAMACHY on Envisat performed observations of mesospheric and lower thermospheric airglow. These measurements were utilized to derive global datasets of atomic oxygen and atomic hydrogen abundance. Both species are key parameters in the mesospheric chemistry and they are essential for the quantification of the energy budget of the middle and upper atmosphere. In this paper, we compare the SCIAMACHY oxygen and hydrogen data with measurements of other instruments and investigate their 11 year solar cycle dependence.

The exploitation of the synergy between infrared and mm-wave
limb sounding measurements is one of the key strength of the
scientific payload proposed for the PREMIER mission candidate to the
Core Missions of ESA Earth Explorer 7. As part of the preparatory
activities of PREMIER,  the PremierEx campaign was conducted in the
Arctic region (Kiruna, Sweden) with the high altitude research
aircraft M-55 Geophysica in March 2010. In this work, we discuss the
synergistic use of MARSCHALS and MIPAS-STR data acquired during the
PremierEx scientific flight conducted on March 10, 2010 by using an
innovative approach to the problem of atmospheric data fusion. We compare
the quality of synergistic and individual retrieval products and
present our conclusions on the potential of combined exploitation of
the information associated to infrared and mm-wave limb observations
of the UTLS. The cloud coverage (low clouds in the first part, no
clouds in the central part and high tropospheric clouds at the end)
observed along the flight provided representative test cases to
evaluate the synergy in three different cloudy scenarios.

During the discussion, seed questions proposed by the chairs will be discussed with the audience.”