An updated assessment of uncertainties in ''observed'' climatological winds and temperatures in the middle atmosphere (over altitudes ϳ10-80 km) is provided by detailed intercomparisons of contemporary and historic datasets. These datasets include global meteorological analyses and assimilations, climatologies derived from research satellite measurements, historical reference atmosphere circulation statistics, rocketsonde wind and temperature data, and lidar temperature measurements. The comparisons focus on a few basic circulation statistics (temperatures and zonal winds), with special attention given to tropical variability. Notable differences are found between analyses for temperatures near the tropical tropopause and polar lower stratosphere, temperatures near the global stratopause, and zonal winds throughout the Tropics. Comparisons of historical reference atmosphere and rocketsonde temperatures with more recent global analyses show the influence of decadal-scale cooling of the stratosphere and mesosphere. Detailed comparisons of the tropical semiannual oscillation (SAO) and quasibiennial oscillation (QBO) show large differences in amplitude between analyses; recent data assimilation schemes show the best agreement with equatorial radiosonde, rocket, and satellite data.

[1] The aim of the UARS (Upper Atmosphere Research Satellite) Reference Atmosphere Project (URAP) is to provide a comprehensive zonal mean reference description of the stratosphere using measurements from instruments on board the UARS. A data set has been produced which describes the monthly zonal mean zonal winds from the surface to the upper mesosphere. Wind measurements from the High Resolution Doppler Imager (HRDI) were combined with results from the Met Office stratospheric data assimilation system. Balanced winds derived from the URAP temperature data set were used to bridge the gap between the stratospheric winds and HRDI mesospheric winds.

[1] Using the TIMED Doppler interferometer (TIDI) mesospheric and lower thermospheric neutral-wind multiyear data set (2002)(2003)(2004)(2005)(2006)(2007) and NCAR TIME General Circulation Models (GCM) 1.2 annual run results (2002)(2003)(2004)(2005) at the TIDI sampling points, we study the migrating diurnal tide's global distribution, interannual, and seasonal variations in connection with the mean zonal wind interannual variations. A strong quasi-biennial oscillation (QBO) effect on the diurnal tide was observed in the TIDI data and reproduced to a lesser degree in the TIME-GCM run. The migrating diurnal tide amplitude is larger during the eastward phase of the stratospheric QBO and weaker during the westward phase. Westward mesospheric equatorial mean zonal winds appeared during the eastward phase of the stratospheric QBO (in 2002, 2004, and 2006). The strongest QBO effect on both the migrating diurnal tide and mean zonal winds was observed during the March equinox. The stronger tides may be related to the weaker gravity wave filtering in the stratosphere during the eastward phase stratospheric QBO. The TIDI data also exhibit large interhemispheric asymmetry. The westward mean zonal winds in the mesosphere appeared to be associated with the enhanced diurnal tide. The TIME-GCM 1.2 diurnal tide amplitudes are in general smaller than those observed by the TIDI instrument. Limited vertical spatial resolution for the TIME-CGM 1.2 is suggested as the cause. Future improvements are expected with a higher spatial resolution in the model.

A strong westward traveling oscillation, with a period of 2 days and zonal wave number 3, is observed in the mesospheric and lower thermospheric winds from the High Resolution Doppler Imager on the Upper Atmosphere Research Satellite. The important events happen in January, July, and September/October, of which the occurrence in January is the strongest with an amplitude over 60ms−1. Detailed analyses for the periods of January 1992 and January 1993 reveal a cause‐and‐effect relationship in the wave developing process at 95km. The global structures of the wave amplitude and phase are also presented.

[1] The Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite carries a limb-scanning Fabry-Perot interferometer designed to perform remotesensing measurements of upper atmosphere winds and temperatures globally. This instrument is called the TIMED Doppler Interferometer, or TIDI. This paper provides an overview of the TIDI instrument design, on-orbit performance, operational modes, data processing and inversion procedures, and a summary of wind results to date. Daytime and nighttime neutral winds in the mesosphere and lower thermosphere/ionosphere (MLTI) are measured on TIDI using four individual scanning telescopes that collect light from various upper atmosphere airglow layers on both the cold and warm sides of the highinclination TIMED spacecraft. The light is spectrally analyzed using an ultrastable plane etalon Fabry-Perot system with sufficient spectral resolution to determine the Doppler line characteristics of atomic and molecular emissions emanating from the MLTI. The light from all four telescopes and from an internal calibration field passes through the etalon and is combined on a single image plane detector using a Circle-to-Line Interferometer Optic (CLIO). The four geophysical fields provide orthogonal line-of-sight measurements to either side of the satellite's path and these are analyzed to produce altitude profiles of vector winds in the MLTI. The TIDI wind measurements presented here are from the molecular oxygen (0-0) band, covering the altitude region 85-105 km. The unique TIDI design allows for more extended local time coverage of wind structures than previous wind-measuring instruments from high-inclination satellites. The TIDI operational performance has been nominal except for two anomalies: (1) higher than expected background white light caused by a low-level light leak and (2) ice deposition on cold optical surfaces. Both anomalies are well understood and the instrumental modes and data analysis techniques have been adjusted to mitigate their effects on data quality. The analysis techniques used to derive winds are described. The TIDI wind measurements from multiple yaw cycles of TIMED have been used to extract migrating diurnal and semidiurnal tides. The migrating tide results are compared with predictions from the Global Scale Wave Model (GSWM), and results from the Upper Atmospheric Research Satellite, High Resolution Doppler Imager (HRDI) instrument. TIDI wind measurements are also compared with ground-based meteor radar observations, showing consistent results.

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...

[1] Observations of the diurnal tide from instruments aboard the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) explorer and from the Upper Atmosphere Research Satellite (UARS) show that the vertical wavelength of the tide is significantly shorter than what is predicted by tidal theory. The observed vertical structure of the tide can be reproduced in a mechanistic model by including gravity wave interaction. The model tide amplitude and phase are sensitive to the amplitude and phase of the diurnal component of momentum forcing that arises from gravity wave breaking. The phase of the momentum forcing relative to the tide determines whether the tide amplitude is increased or diminished by gravity wave forcing, while the amplitude of the momentum forcing determines how rapidly the tide phase will change with height. The momentum forcing profile is shaped by the structure of the gravity wave source spectrum. By comparing both the model tide amplitude and phase profiles to observations, we can provide constraints on both the gravity wave source spectrum that should be used in a gravity wave parameterization scheme and on the eddy diffusion that acts on the tide. We examine differences between the effects that two gravity wave schemes have on the tide. The role that gravity waves may play in producing tide variability is discussed in light of the results presented here.

[1] This study focuses on interannual variations of diurnal tropospheric heating and the response in the mesosphere observed by radars and predicted by a model. The work is prompted by reports of interannual variability in amplitudes of tidal variables at low latitudes. Diurnal tides observed at Hawaii and Christmas Island exhibit a pronounced ''spike'' in amplitude from late 1997 to early 1998. It has been speculated that this variability may be linked to the El Niño-Southern Oscillation phenomenon. We examine diurnal solar heating due to water vapor absorption, and diurnal latent heat release due to deep convection between 1988 and 2005. Both of these heating drives exhibit anomalously higher amplitudes in the tropical central and eastern Pacific during 1997-1998. The altered heating patterns result in a stronger forcing of the migrating diurnal tide by water vapor heating, and excitation of several weaker nonmigrating modes by latent heating. A primitive equation model is used to evaluate how these drives contribute to diurnal winds in the mesosphere. Anomalous water vapor heating results in about 15% increases in model meridional wind amplitudes over climatological values at subtropical latitudes between 300°E and the Greenwich meridian. While the timing of the model amplitude enhancements is consistent with observations at Hawaii, the observed increases are significantly stronger. Our study indicates that water vapor heating is the larger contributor to tidal enhancement observed during 1997-1998.