Martin Kaufmann

The existence of a tertiary ozone maximum in the high‐latitude middle mesosphere

Modeling and observations provide evidence of the existence of a tertiary ozone maximum in the middle mesosphere restricted to winter high-latitudes. This local maximum occurs at approximately 72 km altitude, at lati- tudes just equatorward of the polar night terminator. Model analysis indicates that this maximum is the result of a de- crease in atomic oxygen losses by catalytic cycles involving the odd-hydrogen species OH and HO2. In the middle meso- sphere, at high latitudes, the atmosphere becomes optically thick to ultra-violet radiation at wavelengths below 185 nm. Since photolysis of water vapor is the primary source of odd- hydrogen, reduced ultra-violet radiation results in less odd- hydrogen and consequently lower oxygen loss rates. The consequent increase in atomic oxygen results in higher ozone because atomic oxygen recombination remains the only sig- nificant source of ozone in the mesosphere.

Global distribution of atomic oxygen in the mesopause region as derived from SCIAMACHY O(1S) green line measurements

A new data set of atomic oxygen abundance in the upper mesosphere and lower thermosphere is presented. The data are derived from the nighttime atomic oxygen green line limb emission measurements of the SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) instrument on the European Environmental Satellite. The temporal coverage is October 2002 until April 2012, and the latitudinal extent is 50°S to 80°N at 10 P.M. local time. This data set is compared to other satellite data sets, in particular to recently published data of SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and the Mass Spectrometer and Incoherent Scatter model. SCIAMACHY atomic oxygen peak abundances are typically 3–6×1011 mol/cm3 at the atomic oxygen maximum region, depending on latitude and season. These values are similar to previous values based on chemiluminescence measurements of the atomic oxygen three-body recombination reaction but at least 30% lower than atomic oxygen abundances obtained from SABER.

Tomographic reconstruction of atmospheric gravity wave parameters from airglow observations

Gravity waves (GWs) play an important role in the dynamics of the mesosphere and lower thermosphere (MLT). Therefore, global observations of GWs in the MLT region are of particular interest. The small scales of GWs, however, pose a major problem for the observation of GWs from space. We propose a new observation strategy for GWs in the mesopause region by combining limb and sub-limb satellite-borne remote sensing measurements for improving the spatial resolution of temperatures that are retrieved from atmospheric soundings. In our study, we simulate satellite observations of the rotational structure of the O2 A-band nightglow. A key element of the new method is the ability of the instrument or the satellite to operate in so-called “target mode”, i.e. to point at a particular point in the atmosphere and collect radiances at different viewing angles. These multi-angle measurements of a selected region allow for tomographic 2-D reconstruction of the atmospheric state, in particular of GW structures. The feasibility of this tomographic retrieval approach is assessed using simulated measurements. It shows that one major advantage of this observation strategy is that GWs can be observed on a much smaller scale than conventional observations. We derive a GW sensitivity function, and it is shown that “target mode” observations are able to capture GWs with horizontal wavelengths as short as∼ 50 km for a large range of vertical wavelengths. This is far better than the horizontal wavelength limit of 100– 200 km obtained from conventional limb sounding.

The Response of Atomic Hydrogen to Solar Radiation Changes

The combination of satellite born SCIAMACHY hydroxyl and GOMOS ozone limb measurements allows for the derivation of the global distribution of atomic hydrogen abundance and instantaneous chemical heating rates in the mesopause region. Chemical heating rates show maximum values of 5–10 K/day at 85–90 km; atomic hydrogen densities are 1–5⋅108 cm−3. Signatures of equatorial Kelvin waves, Rossby-gravity waves and Rossby waves are clearly visible in the data. A pronounced latitudinal structure with maxima at the equator and at mid latitudes is observed. Between 2002 and 2008 chemical heating rates decreased and atomic hydrogen density increased, in accordance with model simulations of the 11-year solar cycle.

Atmospheric parameters retrieved from CRISTA measurements in the upper mesosphere and lower thermosphere

During its two missions of about one week duration each in November 1994 and in August 1997 the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment observed spectrally resolved mid- and far- infrared emissions from the earth limb in the altitude regime from the troposphere to the lower thermosphere. The measurements concentrated on high spatial resolution in all three dimensions in the lower part of the height range. At upper mesosphere/lower thermosphere altitudes global ozone concentrations during day and night, daytime carbon-dioxide densities, and atmospheric temperatures were derived using a comprehensive non-LTE model. The derived parameters compare well with other experimental data. Pronounced horizontal structures in latitude as well as in longitude are found in all parameters showing that dynamical influences are of importance also in the upper mesosphere/lower thermosphere. Carbon dioxide mixing ratios start to depart from their tropospheric values at altitudes as low as 70 - 80 km. Atmospheric temperatures of 140 K and below were retrieved near the mesopause at high northern latitudes in August. These data are supported by the simultaneous observation of polar mesospheric clouds.

Infra-red Radiative Cooling/Heating of the Mesosphere and Lower Thermosphere Due to the Small-Scale Temperature Fluctuations Associated with Gravity Waves

We address the effect of an additional infrared radiative cooling/heating of the mesosphere and lower thermosphere (MLT) in the infrared bands of CO2, O3 and H2O due to small-scale irregular temperature fluctuations associated with gravity waves (GWs). These disturbances are not well resolved by present general circulation models (GCMs), but they alter the radiative transfer and cooling rates significantly. A statistical model of gravity wave-induced temperature variations was applied to large-scale temperature profiles, and the corresponding direct radiative calculations were performed with accounting for the breakdown of the local thermodynamic equilibrium (non-LTE). We show that temperature fluctuations can cause an additional cooling of up to 4 K day−1 near the mesopause. The effect is produced mainly by the fundamental 15 μm band of the main CO2 isotope 12C16O2 (626). A simple parametrization has been derived that computes corrections depending on the temperature fluctuations variance, which need to be added in radiative calculations to the mean temperature and the volume mixing ratios (VMRs) of CO2 and O(3P) to account for additional cooling/heating caused by the unresolved disturbances. Implementation of this scheme into the LIMA model resulted in a colder and broader simulated summer mesopause in agreement with recent lidar measurements at Spitsbergen.

A novel CubeSat payload for airglow measurements in the mesosphere and lower thermosphere

The Institute for Atmospheric and Environmental Research at the University of Wuppertal and the Institute of Energy and Climate Research Stratosphere (IEK-7) at the Research Center Juelich developed a novel CubeSat payload for atmospheric research. The payload consists of a small spectrometer for the observation of airglow at 762 nm. The line intensities of the oxygen A-band are used to derive temperatures in the mesosphere and lower thermosphere (MLT) region. The temperature data will be used to analyze dynamical wave structures in the atmosphere which have become increasingly important for the modeling of the climate system. Integrated in a 6U CubeSat, the instrument needs a highly accurate attitude determination and control system (ADCS) for limb sounding of the atmosphere. The agility of a CubeSat shall be used to sweep the line-of-sight through specific regions of interest to derive a three-dimensional image of an atmospheric volume using tomographic reconstruction techniques. The spectrometer technology chosen to measure the ro-vibrational structure of the O2 atmospheric band at 762 nm is a Spatial Heterodyne Interferometer (SHI) originally proposed by Pierre Connes in 1958. The throughput of an SHI is orders of magnitude larger than of a conventional grating spectrometer of the same size. It can be designed to deliver extraordinary spectral resolution to resolve individual emission lines. The utilization of a two-dimensional imaging detector allows for recording interferograms at adjacent locations simultaneously. Since an SHI has no moving parts, it can be built as a monolithic block which makes it very attractive for remote sensing, especially from space.

Atmospheric gravity waves observation from a lunar base

Global change refers to changes in the atmosphere, oceans, biosphere, pedosphere and lithosphere over the past century. It is a long process with large dimensions. Nowadays, satellite provides a regular platform to take measurements of all sensitivity factors of Earth. However, measurements taken from satellite platform is only available in a limited region on Earth with a short observing time. This is a new challenge for the purpose to observe large scale, long period Earth phenomena. In recent years, there has been a renewed interest in the development of robotic and manned exploration missions to the Moon. Here we propose the possibility of observing large-scale Earth phenomena from a lunar base. Atmospheric gravity waves, which is of interest to atmospheric research and important to the global change, are discussed as a sensitivity factor for lunar-based observation.