Klaus U. Grossmann

Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment and middle atmosphere variability

The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument was built to determine whether and to what extent small-scale structures in global trace gas distributions and in dynamics are present in the middle atmosphere. To achieve this, trace gases were measured in the middle infrared by the limb scan technique at the highest possible horizontal and vertical resolution. CRISTA uses three telescopes (i.e., three view directions) simultaneously, and has three grating spectrometers for the middle IR (4-14 μm) and one spectrometer for the far IR (15-71 μm). The optics and detectors are cooled to cryogenic temperatures by supercritical helium or subcooled helium, respectively, in a double cryostat. An instrument overview is given, and the design guidelines are sketched. The CRISTA experiment was flown on the space shuttle STS 66 as part of NASA mission ATLAS 3 on November 3-14, 1994. Orbit altitude was 300 km, and inclination was 57°. A campaign of ground-based, balloon, and rocket validation and complementary measurements was performed simultaneously. The CRISTA instrument performed flawlessly. A horizontal resolution of 200 km × 650 km was achieved at the equator, with higher horizontal resolution at higher latitudes. A vertical resolution of 2.5 km (or better) was obtained. The middle atmosphere was found to be highly variable at scales of <1000 km in the stratosphere. Three streamers of tropic/ subtropic air extending to higher latitudes are described. Their meridional scale is ≤1000 km, while the zonal scale is of the order of 10,000 km and more. The streamers appear to be typical of specific winter conditions and to play a role in meridional transport. At mesospheric heights a strong tidal temperature oscillation was observed which extended well into the lower thermosphere.

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.

Density and temperature structure over northern Europe

Abstract During the Energy Budget Campaign, a number of profiles of the density and temperature were obtained to study the structure and variability of the atmosphere. The measurements were made using rocket- borne instrumentation launched from Esrange, Sweden, and Andoya Rocket Range, Norway, during November and December 1980. The techniques included meteorological temperature sondes, passive falling spheres, accelerometer instrumented falling spheres, density gauges, mass spectrometers and infrared emission experiments. The instruments provided data covering the altitude range from 20 to 150 km. The measurements were made during periods which have been grouped into three categories by level of geomagnetic activity. Analysis has been made to compare the results and to examine the wave features and variations in the vertical profiles for scales ranging between hundreds of meters and tens of kilometers. Most of the features observed fit qualitatively within the range expected for internal gravity waves. However, the features in the profiles during one of the measurement periods are unusual and may be due to aurorally generated shock waves. The geomagnetic storm conditions caused temperature increases in the lower thermosphere which maximized in the 120–140 km region.

Concentrations of H2O and NO in the mesosphere and the lower thermosphere at high latitudes

Abstract Water vapour and nitric oxide concentrations in the mesosphere and lower thermosphere were derived from infrared emission and positive ion composition measurements above northern Europe during the Energy Budget Campaign 1980. The experiments were performed at different levels of geomagnetic disturbance. Both water vapour and nitric oxide are highly variable. Water vapour mixing ratios between 0.2 ppm and 10 ppm were observed. The nitric oxide peak densities varied by more than a factor of ten. Maximum values of 2 × 10 9 cm −3 were obtained.

Measurements of trace gases by the cryogenic infrared spectrometers and telescopes for the atmosphere (CRISTA) experiment

Abstract The CRISTA experiment aboard the Shuttle Pallet Satellite (SPAS) was flown on STS 66 in early November 1994. During a free flying period of seven days measurements of atmospheric temperatures and of 15 trace gases were performed with unprecedented horizontal resolution. This paper gives a brief description of the instrument and of the observational technique. Preliminary results of CIONO 2 retrievals are presented and discussed in terms of atmospheric dynamics and photochemistry.

PMCs and the water frost point in the Arctic summer mesosphere

In August, 1997 the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) obtained vertical profiles of OH number density and polar mesospheric cloud (PMC) brightness by scanning the limb up to 71° N while the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) obtained co-located vertical profiles of temperature. MAHRSI OH densities are converted to water vapor using a one-dimensional model that assumes photochemical equilibrium. By combining water vapor profiles with CRISTA temperatures we map the frost point both vertically and horizontally in the Arctic summer mesosphere. Our data show that supersaturation can exist between 80-87 km suggesting that growth of ice particles is limited to these altitudes. Additionally, we find that not only is supersaturation an insufficient condition for a PMC but also that PMCs can exist in apparently unsaturated air.

A global measurement of lower thermosphere atomic oxygen densities

The first global measurements of the atomic oxygen fine structure emission line O( 3 P 1 ) → O( 3 P 2 ) at a wavelength of 63 pm were performed by the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiments in November 1994 and in August 1997. The measured limb radiances were converted to atomic oxygen densities in the altitude regime from 130 km to 175 km using a radiative transfer code and MSIS thermospheric temperatures. The resultant densities are on the average about 40% below the predictions of the MSIS model for the low solar activity conditions of the CRISTA experiments and at all altitudes covered by the measurement. The densities exhibit considerable horizontal structures which are only in partial agreement with the MSIS predicted relative variations. The latitudinal distribution shows steeper decreases towards the poles than given in MSIS.

Mesospheric minor species determinations from rocket and ground-based i.r. measurements

Abstract As part of the MAP/WINE campaign the infrared hydroxyl airglow layer was investigated at Kiruna, Sweden, by simultaneous measurements with rocket probes of OH≠ and O2(a1Δg) infrared emissions and concentrations of odd oxygen species (O and O3). Coordinated measurements of OH≠ and O2(a1Δg) zenith radiance and emission spectra and their time histories were made from the ground. The rocket-borne Λ = 1.55 μm radiometer ( ΔΛ ≊ 0.23 μm ) provided volume emission rates for OH for both rocket ascent and descent, showing a peak near 87 km with a maximum of nearly 106 photons sec−1 cm−3. The atomic oxygen distribution showed a concentration of about 1011 cm−3 between 88 and 100 km, dropping off sharply below 85 km. The ground-based radiometer at Λ = 1.56 μm, which had a similar filter bandpass to the rocket-borne instrument, yielded an equivalent of 130 kR for the total OH Δv = 2 sequence, which is consistent with the zenith-corrected rocket-based sequence radiance value of ≌ 110 kR. The rotational temperature of the OH night airglow obtained from the rotational structure of the OH M (3,1) band observed by the ground-based interferometer was about 195K at the time of the rocket measurement. Atomic oxygen concentrations were calculated from the OH profile and show agreement with the directly measured values. Atomic hydrogen concentrations of a few times 107 cm−3 near 85 km were inferred from the data set.

Measurements of odd oxygen in the polar region on 10 February 1984 during MAP/WINE

Abstract Abundances of atomic oxygen and ozone have been measured by various techniques over northern Scandinavia during the MAP/WINE campaign in the winter 1983–1984. On 10 February at Kiruna, Sweden, rocket experiments used resonance fluorescence and twin path absorption at 130 nm to measure [O]between 70 and 178 km. Rocket-borne measurements of nightglow at 557.7, 761.9 and 551.1 nm and at 1.27 μm have also been obtained and [O]values derived from the atmospheric band intensities. Ozone abundances between 50 and 90 km have been determined from rocket-borne measurements of the ν 3 9.6 μm nightglow intensity from Andoya, Norway, and Kiruna. These have been compared with [O 3 ] measured on the same day from the Solar Mesospheric Explorer satellite, using measurements of dayglow at 1.27 μm, and with results from other rocket launchings in MAP/WINE. The results show evidence of low, perhaps exceedingly low, [O] and below normal [O 3 ] above the mesopause. Below 75 km at night [O 3 ] exceeded earlier and subsequent observations in the campaign. The measurements were made during a minor stratospheric warming, characterised by an offset polar vortex centred near the measurement zone.

Rocket-borne measurements of atmospheric infrared fluxes

Abstract In the Energy Budget Campaign two rockets, one from Andoya Rocket Range, Norway, and one from Esrange, Sweden, each carrying a liquid helium cooled infrared spectrometer, were simultaneously launched as part of salvo B. The launches occurred during the recovery phase of the last of four auroral magnetic events after a Joule heating criteria was exceeded. At Andoya, zenith radiance altitude profiles were obtained of nitric oxide (NO) near 5.4μm from 70 to 185 km (rocket apogee), of ozone (O 3 ) near 9.6 μm from 70 to 105 km (instrument sensitivity) and of carbon dioxide (CO 2 ) near 15 μm from 70 to 150 km (instrument sensitivity). Measured CO 2 spectra at 72 km are shown to compare favorably to those calculated for local thermodynamic equilibrium conditions and instrument resolution. By comparing Andoya and Esrange CO 2 radiance profiles it is shown that there is evidence for spatial variation in the emission. Further, it is shown that the very disturbed conditions of salvo B prior to and during these launches appears to have significantly changed the O 3 9.6μm radiance profiles compared to previous rocket measurements in polar disturbed and quiet atmospheres. Using the nitric oxide radiance profiles and spectrum, previous rocket results and computed models it is shown that no radiance increase could be detected from prompt auroral energy deposition. The results support the thesis that the NO density in auroral regions is significantly enhanced over mid-latitude values and that for weak auroras, the reaction NO ( v = 0) + O → NO ( r = 1) + O is the dominant radiation mechanism.