[1] The new Horizontal Wind Model (HWM07) provides a statistical representation of the horizontal wind fields of the Earth's atmosphere from the ground to the exosphere (0-500 km). It represents over 50 years of satellite, rocket, and ground-based wind measurements via a compact Fortran 90 subroutine. The computer model is a function of geographic location, altitude, day of the year, solar local time, and geomagnetic activity. It includes representations of the zonal mean circulation, stationary planetary waves, migrating tides, and the seasonal modulation thereof. HWM07 is composed of two components, a quiet time component for the background state described in this paper and a geomagnetic storm time component (DWM07) described in a companion paper.

The WIND imaging interferometer (WINDII) 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 responsibility 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.

Thermospheric winds measured by the Wind Imaging Interferometer (WINDII) on the upper atmosphere research satellite are analyzed for migrating solar tides. The data cover a 2‐year period commencing February 1992 and are obtained from the atomic oxygen O(1S) 557.7‐nm emission, which provides observations of the 90‐ to 200‐km altitude range during daytime and the 90‐ to 110‐km range at night. The subtropical lower thermosphere is dominated by the diurnal propagating tide which exhibits a vertical wavelength of approximately 22 km, grows in amplitude up to 95 km, and decays rapidly above where molecular diffusion greatly reduces the vertical shears. Although the phase remains fairly uniform throughout the year, a pronounced semiannual oscillation is observed in the diurnal tide amplitude. At both 20°N and 20°S the meridional and zonal wind components attain their maximum values at equinox of approximately 70 and 40 m/s, respectively, while the solstitial minima are nearly a factor of 2 smaller. At 35°N the diurnal tide semiannual amplitude oscillation is still present in the lower thermosphere, but above 100 km it is replaced by an annual cycle with a maximum in July and August. This contrasts with 35°S where the July/August peak is absent and the semiannual oscillation extends to 110 km. At midlatitudes the zonal and meridional winds are of similar magnitude, and no significant hemispheric asymmetries in amplitudes are observed. In the lower thermosphere the semidiurnal tide amplitude exhibits an annual oscillation, with maximum values of 30 to 40 m/s occurring in June/July near 100 km at 35°N, 35°S, and the equator. A bimodal structure in the seasonal variation of the semidiurnal phase is observed. This feature is characterized by rapid equinoctial transitions and is particularly well defined at the equator. Examination of the equatorial middle thermosphere indicates that the semidiurnal tide attains its maximum amplitude at 140 km and exhibits a vertical wavelength of approximately 60 km. These findings indicate the predominance of the antisymmetric (2,3) Hough mode in the tropics.

[1] Using a multiple linear regression analysis of nearly six years of WINDII records, an empirical formula is determined to predict the altitude of the peak of the OH nightglow emission. More than 50,000 altitude profiles of volume emission rate collected by WINDII for the OH (8-3) band P 1 (3) line emission during November 1991 to August 1997 over latitudes 40°S-40°N are used. The peak altitudes of these profiles increase with decreasing integrated emission rates and are almost completely described by the integrated emission rates. However the fitting is improved when a solar cycle dependence is considered. A slight further improvement results from incorporating a sinusoidal annual/semi-annual component for data from the midlatitude region. With this formula, more than 87% of the calculated peak altitudes lie within a 1 km difference of the measured values for the mid-latitude region.

[1] We present a global empirical disturbance wind model (DWM07) that represents average geospace-storm-induced perturbations of upper thermospheric (200-600 km altitude) neutral winds. DWM07 depends on the following three parameters: magnetic latitude, magnetic local time, and the 3-h Kp geomagnetic activity index. The latitude and local time dependences are represented by vector spherical harmonic functions (up to degree 10 in latitude and order 3 in local time), and the Kp dependence is represented by quadratic B-splines. DWM07 is the storm time thermospheric component of the new Horizontal Wind Model (HWM07), which is described in a companion paper. DWM07 is based on data from the Wind Imaging Interferometer on board the Upper Atmosphere Research Satellite, the Wind and Temperature Spectrometer on board Dynamics Explorer 2, and seven ground-based Fabry-Perot interferometers. The perturbation winds derived from the three data sets are in good mutual agreement under most conditions, and the model captures most of the climatological variations evident in the data.

Horizontal wind fields in the mesosphere and lower thermosphere are obtained with the high resolution Doppler imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) by observing the Doppler shifts of emission lines in the 09. atmospheric band. The validity of the derived winds depends on an accurate knowledge of the positions on the detector of the observed lines in the absence of a wind-induced Doppler shift. Relative changes in these positions are readily identified in the routine measurements of onboard calibration lines. The determination of the absolute values relies on the comparison of HRDI observations with those obtained by MF radars and rockets.In addition, the degrees of horizontal and vertical smoothing of the recovered wind profiles have been optimized by examining the effects of these parameters both on the amplitude of the HRDI-derived diurnal tidal amplitude and on the variance of the wind differences with correlative measurements. This paper describes these validation procedures and presents comparisons with correlative data. The main discrepancy appears to be in the relative magnitudes measured by HRDI and by the MF radar technique. Specifically, HRDI generally observes larger winds than the MF radars, but the size of the discrepancy varies significantly between different stations. HRDI wind magnitudes are found to be somewhat more consistent with measurements obtained by the rocket launched falling sphere technique and are in very good agreement with the wind imaging interferometer (WINDID, also flown on UARS. 1. Introduction The high resolution Doppler imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) is designed to measure horizontal winds in the mesosphere and lower thermosphere (50-115 kin) and in the stratosphere (10-40 kin), as part of a coordinated mission which is aimed at an improved understanding of global atmospheric change [Reber et al., 1993]. One of the most important objectives of the HRDI project is to develop a comprehensive global climatology of the winds in the atmosphere from 50 to 115 kin. This will serve as a reference point for future investigations and will provide comparison for global models. Prior to UARS the understanding of the global circulation in the Paper number 95JD01700. 0148-0227/96/95JD-01700505.00 upper mesosphere was based primarily on a collection of localized (ground-based or in situ) observations. Many studies of this region have employed the view of the circulation based on the COSPAR International Reference Atmosphere (CIRA). The widely used CIRA-72 model was derived from data obtained with meteorological rockets prior to 1970. The more recent CIRA-86 contains global gradient winds derived from Nimbus 5 and 6 satellite radiance data in the altitude range 20-80 km and MSIS-83 [Hedin, 1983] satellite and ground-based data in the altitude range 80-120 kin. Wind measurements of the mesosphere and lower thermosphere (MLT) obtained from a network of MF and meteor detection radars show features not present in the simplified CIRA view o...

This paper examines the combined mesospheric and thermospheric (50 to 200 kin) longitudinally averaged winds measured by the wind imaging interferometer (WINDII) and the high-resolution Doppler imager (HRDI) onboard the Upper Atmosphere Research Satellite. The data analyzed cover 2 years from February 1992 to February 1994 and consist of both day and nighttime WINDII winds obtained from the O(•S) green line emission and mesosphere/lower thermosphere daytime HRDI winds from the 02 atmospheric band. The combination of the WINDII and HRDI data sets is first justified by comparing •11 the data in the Iower-thermosphere ..... 1 ..... ;•'" for n•y• and orbits when both ;n•tr•mont• observing the same volume of atmosphere. This comparison shows good agreement between the two instruments. An analysis of the combined WINDII and HRDI winds during equinox and solstice periods is then performed. The amplification with height of the diurnal tide at equinox and its subsequent decay in the lower thermosphere is clearly demonstrated by the observations. The corresponding background (i.e., diurnal mean) zonal wind component exhibits a broad region of easterlies at lower latitudes in the upper mesosphere and lower thermosphere and westerlies at midlatitudes. Above 120 km the mean winds revert to easterlies in the zonal component and a two-celled equator to pole meridional circulation. The solstice circulation is highly asymmetric about the equator in accordance with the interhemispheric difference in solar heating. The reversal of the mesospheric jets as well as the summer to winter hemisphere meridional flow in the middle thermosphere are clearly shown. At solstice a significantly weaker and more hemispherically asymmetric propagating diurnal tide is also evident. struments on UARS make direct horizontal wind measurements: the high-resolution Doppler imager (HRDI) [Ha!rs et al., 1993] measures winds from 10 to 40 km and from 50 to 115 km; the wind imaging interferometer (WINDII)[Shepherd et al., 1993] measures neutral Copyright 1996 by the American Geophysical Union. Paper number 95 JD01706. 0148-0227/96/95 JD-01706505.00 winds from a number of photochemical species in the 80-to 300-km altitude range. The two years of wind data that are presently available provide an unprecedented view of the atmosphere from the stratosphere to the middle thermosphere. HRDI obtains daytime wind measurements from the 02 (0,0) atmospheric band emission layer in the mesosphere and lower thermosphere (MLT) over the 50-to 115-km altitude range. At night this emission is confined to a narrow layer, and HRDI provides winds only at, the altitude of the emission peak (situated at approximately 94 km). Because of the uncertainty in their altitudes (• 4-2 km) the HRDI nighttime winds have not been employed in the present study. In addition, the HRDI stratospheric winds (10 -40 km) are beyond the scope of this paper and so are not used. 10,441 10,442 MCLANDRESS ET AL.: MESOSPHERE/THERMOSPHERE WINDS FROM UARS At present, only winds obtained from the WINDII O(•...

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