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OH-equivalent temperatures were derived from all of the temperature profiles retrieved in 2004 and 2005 by the ACE-FTS instrument in a 5 degree band of latitude centred on a ground-based observing station at Maynooth. A globally averaged OH volume emission rate (VER) profile obtained from WINDII data was employed as a weighting function to compute the equivalent temperatures. The annual cycle of temperature thus produced was compared with the annual cycle of temperatures recorded at the ground-based station more than a decade earlier from the OH*(3-1) Meinel band. Both data sets showed excellent agreement in the absolute value of the temperature minimum (~162 K) and in its time of occurrence in the annual cycle at summer solstice. Away from mid-summer, however, the temperatures diverged and reach a maximum disagreement of more than 20 K in mid-winter. Comparison of the Maynooth ground-based data with the corresponding results from two nearby stations in the same time-period indicated that the Maynooth data are consistent with other ground stations. The temperature difference between the satellite and ground-based datasets in winter was reduced to 14–15 K by lowering the peak altitude of the weighting function to 84 km. An unrealistically low peak altitude would be required, however, to bring temperatures derived from the satellite into agreement with the ground-based data. OH equivalent temperatures derived from the SABER instrument using the same weighting function produced results that agreed well with ACE-FTS. When the OH 1.6 μm VER profile measured by SABER was used as the weighting function, the OH equivalent temperatures increased in winter as expected but the summer temperatures were reduced resulting in an approximately constant offset of 8.6±0.8 K between ground and satellite values with the ground values higher. Variability in both the altitude and width of the OH layer within a discernable seasonal variation were responsible for the changes introduced. The higher temperatures in winter were due to primarily to the lower altitude of the OH layer, while the colder summer temperatures were due to a thinner summer OH layer. We are not aware of previous reports of the effect of the layer width on ground-based temperatures. Comparison of OH-equivalent temperatures derived from ACE-FTS and SABER temperature profiles with OH*(3-1) temperatures from Wuppertal at 51.3° N which were measured during the same period showed a similar pattern to the Maynooth data from a decade earlier, but the warm offset of the ground values was lower at 4.5±0.5 K. This discrepancy between temperatures derived from ground-based instruments recording hydroxyl spectra and satellite borne instruments has been observed by other observers. Further work will be required by both the satellite and ground-based communities to identify the exact cause of this difference.

One of the steps leading to an assessment of the biological significance of ozone destruction is to determine the biologically effective ultraviolet radiation (UVB) distribution. The objective of this study is to describe and analyze broadband UVB radiation at 24 locations across Canada, during the period from July 1992 through December 1993. This is the first study of broadband UVB measurements involving such a large number of UVB measuring instruments. Quantitative characteristics and statistical analysis of the surface UVB radiation in Canada with respect to ozone amount, as well as cloudiness, are presented. The results indicate higher UVB irradiance in the second half of 1992, compared with the same period in 1993. Among all the locations, Toronto received the greatest dose of UVB radiation in 1993. Excluding Yellowknife, due to its northernmost location (larger zenith angles), Ste-Agathe, Quebec received the smallest dose. Unusually high UVB fluxes were found to occur in March 1993 over eastern Canada. A study of the correlation of UVB radiation with total ozone and cloud opacity was carried out for most of the locations. The results suggest that other meteorological parameters have a significant impact on the ultraviolet levels.

Satellite volume emission rates of the hydroxyl airglow and the atomic oxygen greenline measured by the wind imaging interferometer (WINDII) on board the upper atmospheric research satellite (UARS) are used to infer atomic oxygen profiles in the mesopause region. The data extends during the lifetime of the instrument from late 1991 through to 1997. The atomic oxygen derived from each emission is combined to provide a climatology extending from 80 to 115 km which includes up to 15 km above and below the peak in atomic oxygen concentration. A spectral analysis is performed for each latitude/local time/altitude bin on the time series of the atomic oxygen where the measurements were taken. Annual and semi-annual variations were identified and their resulting amplitudes and phases showed strong variability as functions of altitude and latitude. A summary of the conclusions are as follows: At mid-latitudes, the atomic oxygen time series consists of both annual and semi-annual variations with amplitudes up to 50% from the mean. The maximum and minimum of the annual variation depended on the hemisphere and the altitude. At the atomic oxygen peak (about 96 km ), the amplitude of the annual variation minimized in the winter hemisphere with a change phase in 180° through the equator towards the summer hemisphere and is consistent with previous observations. The phase of these variations depends on height. Below the oxygen peak (about 87 km ), the phase of the annual variation changed by 180°. At the equator, the atomic oxygen is dominated by the semi-annual variation with maxima about a month after the equinoxes with an amplitude that is stronger than in the northern hemisphere. The mid-latitude semi-annual results are in contrast to previous observations. There is also evidence for a quasi-biennial oscillation in the mesopause region in atomic oxygen at altitudes above 95 km .

Argon is the third most abundant constituent of the atmosphere, but has not been previously detected by any ground-based optical remote sensing method. We report observation of argon emissions at λ840.82 and λ842.46 nm during intense aurora. These are most likely excited by direct electron impact. The maximum argon intensity observed is 270 R . Argon is the fifth elemental emission conclusively observed in geo-aurora, joining N, O, H and He.

Noctilucent clouds (NLC) are a beautiful, high-latitude, summertime phenomenon that was first reported over 100 years ago. They are seen during the hours of twilight by the scattering of sunlight from sub-micron-sized ice particles that form in the vicinity of the cold mesopause region. NLC are quite distinctive, often appearing silvery-blue in color. In recent years there has been a marked increase in their frequency of occurrence, possibly due to an increase in mesospheric water vapor and/or to a cooling of the mesopause region, prompting speculation that they are “harbingers” of potentially serious changes in the mesospheric climate. In concert with this trend there are also a growing number of ground-based NLC sightings at significantly lower latitudes than expected. Here we report two unusual NLC displays photographed from Logan, UT, USA (∼42°N) during June 1999, well over 10° lower in latitude than expected and implying a major, yet temporary, departure from normal mid-latitude summertime conditions. These data provide new evidence for the occasional expansion of NLC to unusually low latitudes possibly due to exceptional dynamical forcing. Alternatively, they may be an early indicator of significant long-term changes taking place in the upper mesospheric summertime environment.

The global distribution of traveling planetary wave (PW) activity in the mesopause region is estimated for the first time from ground-based airglow measurements. Monthly and total mean climatologies of PW power are determined from rotational temperatures measured at 19 sites from 78ºN to 76°S which contribute to the Network for the Detection of Mesospheric Change (NDMC). Wave power is expressed as the standard deviation of nocturnal mean temperature around the seasonal temperature variation. The results from 20ºN confirm the SABER traveling PW proxy by Offermann et al. (2009) at two altitudes. Most sites between 69°S and 69°N show total mean traveling PW activity of about 6 K, and only some high latitude sites have considerably higher activity levels. At the two tropical sites, there is practically no seasonal variation of PW activity. At 70% of the midlatitude sites, the seasonal variation is moderate for most of the year, but it is quite appreciable at all high latitude sites. Results about traveling PW activity at 87 km and 95 km available from several sites signal similar behavior at both altitudes. The total mean climatological results here obtained have further been used to separate the traveling PW contribution from the superposition of wave types contained in OH rotational temperature fluctuations measured by the SCIAMACHY instrument on Envisat. A narrow equatorial wave activity maximum is probably caused by gravity waves, while a tendency towards greater activity at higher northern latitudes may be due to stationary planetary waves. Fil: Reisin, Esteban Rodolfo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Scheer, Jurgen. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Dyrland, M. E.. University Centre in Svalbard; Noruega Fil: Sigernes, F.. University Centre in Svalbard; Noruega Fil: Deehr, C. S.. University of Alaska Fairbanks; Estados Unidos Fil: Schmidt, C.. Deutsches Zentrum für Luft- und Raumfahrt (DLR); Alemania Fil: Höppner, K.. Deutsches Zentrum für Luft- und Raumfahrt (DLR); Alemania Fil: Bittner, M.. Deutsches Zentrum für Luft- und Raumfahrt (DLR); Alemania Fil: Ammosov, P. P.. Institute of Cosmophysical Research and Aeronomy SB RAS; Rusia Fil: Gavrilyeva, G. A.. Institute of Cosmophysical Research and Aeronomy SB RAS; Rusia Fil: Stegman, J.. Stockholms Universitet; Suecia Fil: Perminov, V. I.. Russian Academy of Sciences; Rusia Fil: Semenov, A. I.. Russian Academy of Sciences; Rusia Fil: Knieling, P.. University of Wuppertal; Alemania Fil: Koppmann, R.. University of Wuppertal; Alemania Fil: Shiokawa, K.. Nagoya University; Japón Fil: Lowe, R. P.. University of Western Ontario; Canadá Fil: López González, M. J.. Instituto de Astrofísica de Andalucía; España Fil: Rodríguez, E.. Instituto de Astrofísica de Andalucía; España Fil: Zhao, Y.. State University Of Utah; Estados Unidos Fil: Taylor, M. J.. State University Of Utah; Estados Unidos Fil: Buriti, R. A.. Universidade Federal de Campina Grande; Brasil Fil: Espy, P. J.. Norges Teknisk-Naturvitenskapelige Universitet; Noruega Fil: French, W. J. R.. Australian Antarctic Division; Australia Fil: Eichmann, K. U.. Universität Bremen; Alemania Fil: Burrows, J. P.. Universität Bremen; Alemania Fil: von Savigny, C.. Ernst-Moritz-Arndt Universität; Alemania

The rotational temperature obtained from the rotational population distribution in the bands of the hydroxyl airglow has been shown to be a suitable proxy for the temperature at a height of 87 km [She and Lowe, 1998]. In this paper we examine in detail simultaneous observations on November 2–3, 1997, at Fort Collins, Colorado (41°N, 105°W), with both a sodium temperature lidar and the Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) OH mesospheric temperature mapper during which significant differences between the hydroxyl and lidar temperatures occur. The large differences are associated with a major temperature enhancement in the region of the peak of the hydroxyl emission. We model the effect on the shape of the emission rate profile of the hydroxyl airglow caused by the large temperature enhancement observed on this night by the lidar. As a result of the temperature sensitivity of the processes that give rise to the airglow, the profile shows major distortions from its normal shape. These distortions in turn lead to hydroxyl rotational temperatures that differ significantly from the 87-km lidar observations. The mean rotational temperature deduced in this way agrees well with the observed values. Such deviations in the temperature are expected to be rare, occurring only when a large temperature enhancement occurs near the peak of the airglow emission profile.

Images of the variations of OH intensities have been recorded by a three-station network of scanning radiometers in southwestern Ontario during the period from May until September 1998. The ensemble of gravity waves seen in all three instruments is analyzed and observed to have a strong dependence in their propagation direction with the majority of waves seen at each of the three sites having a horizontal wave vector in the northeast direction. In order to understand these results a model of the transmission of gravity waves through the atmosphere was employed. The gravity waves observed by the OH Scanning Radiometers (OHSCRs) are assumed to originate in the troposphere with an isotropic spectrum, meaning that the average wave amplitudes are equal in all directions. The gravity waves propagate upward where they will undergo a selection process owing to the effect of the “background winds.” Using the horizontal winds from the Horizontal Wind Model (HWM-93), the transmission of gravity waves from a tropospheric source is modeled and shown to be consistent with the observations. The strong zonal winds account for the summer eastward and winter westward propagation, but it is the tidal components of the meridional wind that account for the northward tendency of wave propagation (and the corresponding relative absence of southward propagating waves). In order to further validate the transmission, model winter measurements from the OHSCR data set are examined and shown to be consistent.

Images of the variations of OH nightglow intensities have been recorded by a three-station network of scanning radiometers in southwestern Ontario during the period from May until September 1998. Each radiometer performs a 16 by 16 point raster scan of the night sky every minute, turning itself on and off when the solar depression angle is

The WINDII instrument onboard the UARS satellite made many thousands of measurements of the apparent brightness of the hydroxyl airglow as a function of tangent height during the night. The measurements were mainly at latitudes between 42°S and 42°N. Most of the profiles of volume emission rate indicate a simple layer with a peak between 85 and 90 km. However, from 5 to 25% of the measured profiles have a more complex structure for the layer profile, most frequently with two peaks separated by 4 to 6 km. The horizontal extent varies from 200 to several thousand kilometers, and the duration may be as long as 1½ hours. Here the WINDII data from November 1991 to April 1995 are used to study the frequency of occurrence of the double-peaked layers as a function of latitude, season, and local time and to explore possible causes of the unusual profiles. Early in the night the double-peaked layers occur preferentially at low to medium latitudes, migrating toward the equator by midnight where they remain for the rest of the night. There is a pronounced asymmetry between the hemispheres which reverses between the March/April equinox and the September/October equinox. The solstice behavior is similar, though not so pronounced. Through simulation three possible causes to the observed OH* double-peaked layers were identified. Gravity waves are a likely source of isolated small-scale events but the large horizontal scale, long-duration structures are more likely to result from temperature inversion layers or mixing events or a combination of the two.

Measurements of the hydroxyl nightglow from the Wind Imaging Interferometer (WINDII) satellite-borne experiment and from ground-based photometers are compared and combined in order to characterize the hydroxyl airglow nocturnal behavior at 23°S and the equatorial region. Ground-based observations at Cachoeira Paulista (23°S, 45°W) and at Fortaleza (4°S, 38°W) from 1987 to 1994 and WINDII data from March 1992 to January 1994 are selected, and two periods are studied: the March/April equinox and the December/January solstice. The WINDII results for the equinox/solstice difference and for the nocturnal behavior of the vertically integrated emission rate of the hydroxyl nightglow are found to be in very good agreement with the ground-based observations. The WINDII measurements revealed two general characteristics of the hydroxyl nightglow altitude variation at the latitudes above. The hydroxyl nocturnal variations are predominantly occurring below 90 km, and the vertically integrated emission rate and the peak height of the volume emission rate show an inverse relationship with seasonal, latitudinal, and inter annual effects. The interpretation of these results in terms of atmospheric tides is then discussed.

Experimental investigations by ground-based and rocket methods during the last four decades have allowed the inference of many kinds of variations of the hydroxyl emission. However, the previous data base is insufficient to derive longitudinal variations of the emission characteristics. The WINDII instrument on board the UARS satellite provides global observations of the OH(8-3) band. In this paper we present such observations at mid-latitudes for 1993 to characterize the longitudinal variations of the zenith brightness and peak altitude of the hydroxyl emission.

Fifty-one nights of lidar data and seventy-eight nights of Fourier transform spectrometer data taken during 1993 for the purpose of temperature measurements in the mesopause region were analyzed. Observed OH∗-temperatures from the (3-1) band over Delaware Observatory (43°N) were compared statistically to (1) Na-layer temperatures, (2) temperatures at 87 km, and (3) OH∗-temperatures inferred from the WINDII observed OH∗ height profiles and lidar observed temperature profiles, all over Fort Collins (41°N). Seasonal temperature variations were deduced for two midlatitude sites and the resulting measurements were compared statistically. Very good agreement was obtained between the two sites in the magnitude of seasonal differences and variations. With marginal statistical significance, an overall 6–7 K difference between the observed and inferred seasonal averaged temperatures was detected. Other than the ∼3 K difference in the summer accountable by the latitude difference, the remaining discrepancy may be tentatively resolved by a longitudinal difference with higher temperatures near mountainous region, revealed from a comparison of temperatures observed at the same nights over different Stations. Even with substantial data set considered here, geophysical variability still dominates the measurement uncertainty in seasonal means. One useful conclusion of this study is that for many purposes, the hydroxyl rotational temperature can be used as proxy for the temperatures at 87±4 km.

Observations made during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) campaign during October 1993 revealed the presence of persistent large perturbations of the temperature and density in the 80 to 100 km mesopause region. These perturbations, seen both by passive airglow and active lidar techniques, were identified as due to the presence of diurnal and semidiurnal tides. These results were compared with the predictions of the thermosphere/ionosphere/mesosphere electrodynamics general circulation model (TIME-GCM). This model was recently tuned to agree with the observations from the Upper Atmosphere Research Satellite (UARS) with respect to mesosphere/lower thermosphere winds (60–200 km). It is found that although the TIME-GCM agrees with UARS winds, it underpredicts the diurnal, and possibly the semidiurnal, tidal temperature perturbations seen during ALOHA-93. Since the TIME-GCM only includes migrating tides, this comparison suggests that nonmigrating tides may have had a significant amplitude during the ALOHA-93 campaign period. UARS observations of the major nonmigrating diurnal mode were made just before and after the ALOHA-93 period. It is found that the zonally symmetric nonmigrating tide can account for the discrepancy between the ALOHA-93 results and the TIME-GCM predictions only for a few periods and only at an altitude around 88 km. If the zonally symmetric nonmigrating tide is to account for the discrepancies between the model and the data, than it has to be highly variable.

On October 9, 1993, observations were made from the National Center for Atmospheric Research Electra aircraft during a flight from Maui, Hawaii, toward a low-pressure system NW of the island, a flight of 7 hours in total. The leading edge (wall) of a bright airglow layer was observed 900 km NW of Maui at 0815 UT, which was traveling at 75 m s−1 toward the SE, reaching Haleakala, Maui, about 3.25 hours later [see Swenson and Espy, 1995]. An intriguing feature associated with the event was the large increase in the mesospheric Na column density at the wall (∼180%). The enhancement was distributed over a broad region of altitude and was accompanied by significant perturbations in the Meinel (OH) and Na D line airglow emission intensities, as well as the temperature. This paper describes an investigation of the combined measurements from the aircraft and at Haleakala, including an analysis of the event using a gravity wave dynamic model. The modeled atmospheric variations associated with the leading edge of the “wall” wave are then applied to models of the neutral and ionic chemistry of sodium in order to establish whether the enhancement was caused by the release of atomic Na from a local reservoir species, as opposed to redistribution by horizontal convection. The most likely explanation for the Na release was the neutralization of Na+ ions in a sporadic E layer that was first transported downward by a large amplitude (≈10%) atmospheric gravity wave and then vertically mixed as the wave pushed the atmosphere into a super adiabatic state with associated convective instabilities and overturning.

The local changes of the spectrum with time are often more interesting than the spectrum of the whole time series. For example, there is an apparent drift in the nominal 28 day fluctuations of sunspot numbers over the period of the sunspot cycle, averaging ∼ 11.1 years. This time-local change in spectrum is due to a combination of Sporer's Law and the differential rotation of the sun. Similarly, the space-local variations in the 2-D spectrum on an image conveys visual information on textures, boundaries and shapes. In this paper we use the recently developed S -transform to analyse two segments of the Wolf Sunspot series, a seismogram, and a synthetic 2-D image as examples of applications of the S -transform for time-local and space-local spectral analysis.

An image is a function, f(x, y) , of the independent space variables x and y . The global Fourier spectrum of the image is a complex function F(k x , k y ) of the wave numbers k x and k y . The global spectrum may be viewed as a construct of the spectra of an arbitrary number of segments of f(x, y) , leading to the concept of a local spectrum at every point of f(x, y) . The two-dimensional S transform is introduced here as a method of computation of the local spectrum at every point of an image. In addition to the variables x and y , the 2-D S transform retains the variables k x and k y , being a complex function of four variables. Visualisation of a function of four variables is difficult. We skirt around this by removing one degree of freedom, through examination of ‘slices’. Each slice of the 2-D S transform would then be a complex function of three variables, with separate amplitude and phase components. By ranging through judiciously chosen slice locations the entire S transform can be examined. Images with strictly periodic patterns are best analysed with a global Fourier spectrum. On the other hand, the 2-D S transform would be more useful in spectral characterisation of aperiodic or random patterns.

The S transform, which is introduced in the present correspondence, is an extension of the ideas of the continuous wavelet transform (CWT) and is based on a moving and scalable localizing Gaussian window. It is shown to have some desirable characteristics that are absent in the continuous wavelet transform. The S transform is unique in that it provides frequency-dependent resolution while maintaining a direct relationship with the Fourier spectrum. These advantages of the S transform are due to the fact that the modulating sinusoids are fixed with respect to the time axis, whereas the localizing scalable Gaussian window dilates and translates.

Hydroxyl airglow measurements during the ALOHA-93, ALOHA-90 and ANLC-93 campaigns are used to evaluate features of the temperature variation of the mesopause region. Each campaign shows a persistent pattern in the averaged local time variation of temperature with peak-to-peak amplitudes of 5 K to 15 K, suggestive of the presence of tidal modulation. The nightly temperature variance, after detrending to remove low frequency variations due to tides, is shown to be significantly less during the Hawaiian campaigns than during the ANLC-93 and other campaigns at sites where significant orographic excitation of waves might be expected.

Two Fourier transform spectrometers have been used to investigate the properties of the near-infrared hydroxyl (OH) nightglow emission under high-latitude summertime conditions and any association with noctilucent clouds (NLCs). The measurements were made from Poker Flat Research Range, Alaska (65.1°N, 147.5°W), during August 1986. Simultaneous photographic observations of the northern twilight sky were made from Gulkana, Alaska (62.2°N, 145.5°W), approximately 340 km to the south to establish the presence of NLCs over the spectrometer site. Data exhibiting significant short-term variations in the relative intensity (as much as 50–100%) and rotational temperature (typically 5–15 K) were recorded on six occasions when NLCs were observed. Joint measurements were also obtained on several "cloud-free" nights. No obvious relationship was found linking the mean OH intensity or its variation with the occurrence of NLCs. However, a clear tendency was found for the mean OH temperature to be lower on NLC nights than on cloud-free nights. In particular, a significant fraction of the OH(3–1) band spectra recorded by each instrument (16–57%) exhibited temperatures below ~154 K on NLC nights compared with

Vertical wavelengths of propagation of the 12-hour oscillation of the upper atmosphere have been optically determined from measurements of horizontal motions derived from the Doppler shifts of [OI] at 557 nm and OH(6–2) at 840 nm and from the [OI] and OH(8,3) heights of emission measured by the WINDII experiment. These determinations, at 43.98°S, 170.42°E, have established the existence of a large, brief, yet persistent, enhancement in the vertical wavelength of propagation near the austral autumn equinox. The typical vertical wavelengths of oscillation during the year are in the range 20 km to 40 km, except during the brief period near the austral autumn equinox when they increase to about 100 km. These findings indicate a change in the atmospheric structure at those heights, favoring the presence of longer vertical wavelength modes near the austral autumn equinox.

The Wind Imaging Interferometer (WINDII) was launched on the NASA's Upper Atmosphere Research Satellite on 12 September 1991 and operated until 2003. Its role in the mission was to measure vector winds in the Earth's atmosphere from 80 to 110 km, but its measurements extended to nearly 300 km. The approach employed was to measure Doppler shifts from a suite of visible region airglow lines emitted over this altitude range. These included atomic oxygen O(1S) and O(1D) lines, as well as lines in the OH Meinel (8,3) and O2 Atmospheric (0,0) bands. The instrument employed was a Doppler Michelson Interferometer (DMI) that measured the Doppler shift as a phase shift of the cosinusoidal interferogram generated by single airglow lines. An extensive validation program was conducted after launch to confirm the accuracy of the measurements. The dominant wind field, the first one observed by WINDII, was that of the migrating diurnal tide at the equator. The overall most notable WINDII contribution followed from this; determining the influence of dynamics on the transport of atmospheric species. Currently, non-migrating tides are being studied in the thermosphere at both equatorial and high latitudes. Other aspects investigated included solar and geomagnetic influences, temperatures from atmospheric scale heights, nitric oxide concentrations and the occurrence of polar mesospheric clouds. The results of these observations are reviewed from a perspective of twenty years. A future perspective is then projected, involving more recently developed concepts. It is intended that this description will be helpful for those planning future missions.

Spectra of the hydroxyl night airglow in the near infrared region were obtained under high latitude summer conditions at Poker Flat, Alaska, during August 1986. Rotational temperatures and relative populations have been deduced from the spectra for vibrational levels from 2 to 8. During the observing period the nightly average rotational temperature increased from 155 to 173 K, but the nightly variation of temperature generally did not exceed 10 K. On one night, a short period of nearly sinusoidal variation of both intensity and temperature was observed, with small phase shifts which varied with vibrational level. Correlation of intensity and temperature variation on two nights gave a value of ∼ 8 for Krassovsky's parameter, η. Differences in the average rotational temperature as measured from bands arising from different vibrational levels were noted, but in general they did not exceed the possible calibration uncertainty.

Sporadic Na (Nas) layers were observed by the airborne lidar during ALOHA-90 on the 22, 25 and 27 March flight missions. Perturbations in the O2 and OH nighttime airglow emission intensities and temperatures were also observed by instruments on the aircraft and at Haleakala Crater (20.8°N, 156.2°W) during these events. The most striking correlation between the airglow and lidar measurements occurred during the northbound flight leg of the 25 March mission. When the Nas layer formed at 90.7 km, while the Electra aircraft was between 750 and 500 km south of Haleakala, the O2 temperatures near 95 km above the Electra and Haleakala increased by approximately 45 K. The data for this night suggest a connection between Nas and a large-scale wave, and suggest that the wave is tidal in nature. The data also suggest that some Nas layers can form very quickly over large geographic areas. Fast chemical processes are required to generate the large amounts of atomic Na involved in some of these events.

During the ALOHA‐90 campaign a novel comparative study was made between near infrared wave structure imaged in the zenith using a CCD camera and that detected at infrared wavelengths by a Fourier Transform Spectrometer. Coincident measurements were made briefly on several occasions and for an extended period on 31 March. The temporal variations imaged in the near infrared structure during this night almost completely matched those detected in the OH (3,1) band spectrometer data when similar viewing fields were compared. However, the image data also displayed small scale wave forms that were not resolved by the larger field instrument. These structures exhibited significant changes in brightness and position on a time scale much shorter than the local Brunt‐Väisälä period indicating that very high resolution measurements are necessary to investigate short period (

[1] Hydroxyl and oxygen greenline nightglow observations from the Wind Imaging Interferometer (WINDII) are used to examine the local time–latitude variation of atomic oxygen in the mesopause region. Individual hydroxyl and greenline emission profiles from over 5 years of data are converted to oxygen mixing ratio (or concentration) profiles and then binned into local times, latitudes, and seasons. The two derived oxygen profiles from each emission are then combined into a single profile that spans a significant portion of the mesopause region (80 to 115 km). A technique developed earlier that addresses the altitude variability of the emission profiles is used. This level of agreement indicates a high degree of consistency in the radiance observations and in the photochemistry used to convert the emission rates to oxygen profiles. We demonstrate that the atomic oxygen concentration or mixing ratio profiles are very sensitive to local nighttime, and we display the manner in which they vary. The local time variation is primarily due to the tidal dynamics in the atmosphere. Comparisons between our atomic oxygen data set, a simple tidal model, and the TIME-GCM show good agreement; however, the local time tidal structure of atomic oxygen from MSISE-90 shows a 180° phase inconsistency. The measured local time oxygen variations vary with season and latitude, and we show that these oscillations are stronger under equinox conditions.

Gravity waves are ubiquitous in the Earth's atmosphere transporting energy and momentum between regions. GWIM is a satellite instrument that will use airglow intensity variations to measure gravity wave parameters. A major interest lies in the correlation of the presence of gravity waves with their sources near the surface or in the lower atmosphere. The specific airglow emissions were chosen because of their high radiance and their low susceptibility to contamination by moonlight scattered from clouds. GWIM consists of four nadir-looking imagers, one each for signal and background for each of the two emissions. The field of each imager will be 175 km cross-track by 80 km along the track. An integration time of about ten seconds is required to achieve the required signal-to-noise ratio. To prevent image smearing due to the effects of satellite motion and the rotation of the earth, GWIM will operate in snapshot mode with an exposure time of about 0.25 second followed by on-board shift-and-add. GWIM is being considered for flight as part of the payload of EQUARS, a Brazilian satellite planned for launch into a near equatorial orbit in 2007.

[1] The use of satellite measurements of the hydroxyl airglow volume emission rate profile to infer the atomic oxygen profile of the mesopause region is complicated by uncertainties as to the collision de-excitation mechanism and the vibration transition probabilities that are needed for the analysis. In this paper, we demonstrate that the shape of the derived atomic oxygen profiles is, to a large extent, independent of the choice of these factors. We use data from two nights of observation from the Wind Imaging Interferometer (WINDII) instrument onboard Upper Atmospheric Research Satellite (UARS) where the instrument observed the hydroxyl emission and the oxygen greenline emission on alternate orbits. The comparison between the derived atomic oxygen profiles from the two emissions is difficult because the region of overlap of good quality data lies in between the peaks and is small (about 4 km). Also, the altitude of the good overlap is not fixed but is a function of both latitude and local time and may lie anywhere in the altitude range from 88 to 94 km because the heights of the emission layers also change. We have adopted a technique of doing the comparison only at certain altitude/local time combinations depending on where the best data exists. The hydroxyl parameter set that used Goldman transition probabilities and a sudden death quenching model best fit the greenline derived atomic oxygen and will be used to complete a full atomic oxygen climatology from 80 to 110 km.

In recent times it has become increasingly clear that releases of trace gases from human activity have a potential for causing change in the upper atmosphere. However, our knowledge of systematic changes and trends in the temperature of the mesosphere and lower thermosphere is relatively limited compared to the Earths lower atmosphere, and not much effort has been made to synthesize these results so far. In this article, a comprehensive review of long-term trends in the temperature of the region from 50 to 100 km is made on the basis of the available up-to-date understanding of measurements and model calculations. An objective evaluation of the available data sets is attempted, and important uncertainly factors are discussed. Some natural variability factors, which are likely to play a role in modulating temperature trends, are also briefly touched upon. There are a growing number of experimental results centered on, or consistent with, zero temperature trend in the mesopause region (80–100 km). The most reliable data sets show no significant trend but an uncertainty of at least 2 K/decade. On the other hand, a majority of studies indicate negative trends in the lower and middle mesosphere with an amplitude of a few degrees (2–3 K) per decade. In tropical latitudes the cooling trend increases in the upper mesosphere. The most recent general circulation models indicate increased cooling closer to both poles in the middle mesosphere and a decrease in cooling toward the summer pole in the upper mesosphere. Quantitatively, the simulated cooling trend in the middle mesosphere produced only by CO 2 increase is usually below the observed level. However, including other greenhouse gases and taking into account a “thermal shrinking” of the upper atmosphere result in a cooling of a few degrees per decade. This is close to the lower limit of the observed nonzero trends. In the mesopause region, recent model simulations produce trends, usually below 1 K/decade, that appear to be consistent with most observations in this region

The OH(6-2) band was monitored during 1990 at Davis, Antarctica (68.6°S, 78.0°E) using a Czerny-Turner scanning spectrometer. Spectra obtained with a 0.15-nm bandwidth and wavelength steps of 0.005 nm have been recorded in an attempt to isolate auroral features. This has enabled detailed study of weak features in the region λ837.5–855.5 nm. These weak features can contribute to the apparent intensity of P-branch lines and to the background. Their presence is allowed for in our calculation of rotational temperature, but the P1(3) line is excluded because of significant contamination. An average temperature of 221±2 K is obtained from a selected data set of 104 spectra. The mid-winter average temperature, for the months of May, June and July, is 224±2 K, which is consistent with the 1986 CIRA model values for mid-winter at this height and latitude, but this result is dependent on the choice of transition probabilities. Preliminary assessments of seasonal and diurnal variations in rotational temperature and intensity are presented. Key words. Atmospheric composition and structure · Airglow and aurora; Middle-atmosphere composition and chemistry · Pressure · density and temperature

2D local spectral information can be obtained form an image using Instantaneous Wavevector (IW). This 2D function is a vector quantity found by taking the gradient of the phase of the analytic image. Several synthetic images will be presented to illustrate the utility of IW analysis, and its application to OH airglow images will be discussed. The IW of an image gives us the dominant wavevector present at any point in the image. The amplitude of the analytic image gives us the magnitude of this component, and the phase differences of the analytic image between successive images allow us to infer the velocity of these waves. This method is used to determine phase velocities of internal waves from Hydroxyl airglow data. The instrument used, UWOSCR, is a scanning radiometer in the near infra-red, taking an 256 pixel image of the OH airglow every minute.

The local spectral information of the continuous wavelet transform with Morlet wavelets can, with slight modification, be used to perform 'local' cross spectral analysis with very good time resolution. This 'phase correction' absolutely references the phase of the wavelet transform to the zero time point, thus assuring that the amplitude peaks are regions of stationary phase. Thus phase differences between the 'local spectra' of time series from two spaced receivers can be used to infer time lags as a function of frequency. This method is used to determine apparent phase velocities of atmospheric gravity waves from hydroxyl airglow data. The instrument used, UWOSCR, is a scanning radiometer in the near infra-red, taking a 256 pixel image of the OH airglow every minute. Pixel-to-pixel time lags are used to determine the phase velocity as a function of frequency and time.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

International audience; The WIND imaging interferometer (WINDID was launched on the Upper Atmosphere Research Satellite (UARS) on September 12, 1991. This joint project, sponsored by the Canadian Space Agency and the French Centre National d'Etudes Spatiales, in collaboration with NASA, has the responsi- bility of measuring the global wind pattern at the top of the altitude range covered by UARS. WINDII measures wind, temperature, and emission rate over the altitude range 80 to 300 km by using the visible region airglow emission from these altitudes as a target and employing optical Doppler interferometry to measure the small wavelength shifts of the narrow atomic and molecular airglow emission lines induced by the bulk velocity of the atmosphere carrying the emitting species. The instrument used is an all-glass field-widened achromatically and thermally compensated phase- stepping Michelson interferometer, along with a bare CCD detector that images the airglow limb through the interferometer. A sequence of phase-stepped images is processed to derive the wind velocity for two orthogonal view directions, yielding the vector horizontal wind. The process of data analysis, including the inversion of apparent quantities to vertical profiles, is described.

International audience; WINDII, the Wind Imaging Interferometer on the Upper Atmosphere Research Satellite, began atmospheric observations on September 28, 1991 and since then has been collecting data on winds, temperatures and emissions rates from atomic, molecular and ionized oxygen species, as well as hydroxyl. The validation of winds and temperatures is not yet complete, and scientific interpretation has barely begun, but the dominant characteristic of these data so far is the remarkable structure in the emission rate from the excited species produced by the recombination of atomic oxygen. The latitudinal and temporal variability has been noted before by many others. In this preliminary report on WINDII results we draw attention to the dramatic longitudinal variations of planetary wave character in atomic oxygen concentration, as reflected in the OI 557.7 nm emission, and to similar variations seen in the Meinel hydroxyl band emission.