Molecular Oxygen Singlet Delta State and Ozone Concentration Profiles from SPIRE Data

The rocketborne SPIRE (SPectral InfraRed Experiment) probe was launched from Poker Flat Research Range, Alaska, on Sept 28, 1977 to measure infrared atmospheric emission from the earth’s limb.1 The payload included two coaligned, telescoped, circular-variable-filter (CVF) spectrometers. The short-wavelength spectrometer, cooled to 77° K, covered the spectral region between 1.4μm and 7.0μm while the long-wavelength instrument, cooled to 4° K, made measurements between 9.0μm and 16.5μm. The payload reached an altitude of 285 km. The earthlimb was continuously spatially scanned from hard earth to local horizontal at 0.5 deg/sec while taking a spectrum at 2 scans/sec. The spectrometers measured the earthlimb emission during 12 vertical spatial scans at different azimuths. In doing so the emission was measured from the night (scan 8), terminator (scans 1 through 7), and daylit (scans 9 through 12) sectors of the earthlimb. For a given tangent height day scans correspond to different solar elevation angles. The emission from the a 1Δg (v′=0) --&gt; x3Σg (v″=1) transition of O2 at 1.58μm is observed during the day scans only and increases in radiance with solar elevation angle (Figure 1). This shows that the only important process lending to the production of O2(1Δg) is the photodissociation of ozone. The emissions from ozone at 9.8μm (ν3 band), as well as the 4.8μm v1 + v3 combination band, are measured during both day and night (Figure 2). Around 80 km tangent height, the daytime 9.6μm emission is smaller than the nighttime value by a factor of about 5, because of the decreased daytime ozone density due to photodissociation. Below 50 km tangent height the daytime and nighttime emissions do not show a significant variation, in spite of the fact that some daytime ozone is photodissociated to O2(1Δg) which is observed at 1.58μm. The observed emissions from ozone and O2(1Δg) state are discussed in terms of modelled time-dependent ozone concentrations along the line-of-sight.</jats:p

Simultaneous observations of mesospheric gravity waves and sprites generated by a midwestern thunderstorm

The present report investigates using simultaneous observations of coincident gravity waves and sprites to establish an upper limit on sprite-associated thermal energy deposition in the mesosphere. The University of Alaska operated a variety of optical imagers and photometers at two ground sites in support of the NASA Sprites99 balloon campaign. One site was atop a US Forest Service lookout tower on Bear Mt. in the Black Hills, in western South Dakota. On the night of 18 August 1999 we obtained from this site simultaneous images of sprites and OH airglow modulated by gravity waves emanating from a very active sprite producing thunderstorm over Nebraska, to the Southeast of Bear Mt. Using 25 s exposures with a bare CCD camera equipped with a red filter, we were able to coincidentally record both short duration (\u3c10 ms) but bright (\u3e3 MR) N2 1PG red emissions from sprites and much weaker (~1 kR), but persistent, OH Meinel nightglow emissions. A time lapse movie created from images revealed short period, complete 360° concentric wave structures emanating radially outward from a central excitation region directly above the storm. During the initial stages of the storm outwardly expanding waves possessed a period of τ≈10 min and wavelength λ≈50 km. Over a 1 h interval the waves gradually changed to longer period τ≈11 min and shorter wavelength λ≈40 km. Over the full 2 h observation time, about two dozen bright sprites generated by the underlying thunderstorm were recorded near the center of the outwardly radiating gravity wave pattern. No distinctive OH brightness signatures uniquely associated with the sprites were detected at the level of 2% of the ambient background brightness, establishing an associated upper limit of approximately ΔT ≤ 0.5 K for a neutral temperature perturbation over the volume of the sprites. The corresponding total thermal energy deposited by the sprite is bounded by these measurements to be less than ~1 GJ. This value is well above the total energy deposited into the medium by the sprite, estimated by several independent methods to be on the order of ~1–10 MJ

CO2 Non-LTE Effects in a Line-by-Line Radiative Excitation Model

We have developed a radiative-transfer algorithm for infrared bands in the terrestrial atmosphere and used it to calculate non-LTE vibrational populations of CO2 (described here) and CO (described in a companion paper1). A unique feature of our model is that it incorporates a complete line-by-line transport algorithm. All the effects of the variations in the emission and absorption lineshapes with altitude (for example, due to temperature and pressure dependence) are accounted for. The absorption is calculated on a monochromatic basis for points within each line and then integrated, and this is done for all lines in all ro-vibrational bands in which radiative transport is significant.</jats:p

Comparison of nighttime nitric oxide 5.3 μm emissions in the thermosphere measured by MIPAS and SABER

A comparative study of nitric oxide (NO) 5.3 μm emissions in the thermosphere measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) spectrometer and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) radiometer satellite instruments was conducted for nighttime data collected on 14 June 2003. The agreement between the data sets was very good, within ∼25% over the entire latitude range studied from −58° to + 4°. The MIPAS and SABER data were inverted to retrieve NO volume emission rates. Spectral fitting of the MIPAS data was used to determine the NO(v = 1) rotational and spin-orbit temperatures, which were found to be in nonlocal thermodynamic equilibrium (non-LTE) above 110 km. Near 110 km the rotational and spin-orbit temperatures converged, indicating the onset of equilibrium in agreement with the results of non-LTE modeling. Because of the onset of equilibrium the NO rotational and spin-orbit temperatures can be used to estimate the kinetic temperature near 110 km. The results indicate that the atmospheric model NRLMSISE-00 underestimates the kinetic temperature near 110 km for the locations investigated. The SABER instrument 5.3 μm band filter cuts off a significant fraction of the NO(Δv = 1) band, and therefore modeling of NO is necessary to predict the total band radiance. The needed correction factors were directly determined from the MIPAS data, providing validation of the modeled values used in SABER operational data processing. The correction factors were applied to the SABER data to calculate densities of NO(v = 1). A feasibility study was also conducted to investigate the use of NO 5.3 μm emission data to derive NO(v = 0) densities in the thermosphere.</p