Validation of mesosphere and lower thermosphere winds from the high resolution Doppler imager on UARS

Abstract

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...

Simulation study for measurement of horizontal wind profiles in the polar stratosphere and mesosphere using ground-based observations of ozone and carbon monoxide lines in the 230–250 GHz region

“…The height resolutions, estimated at ∼ 20 km in winter and ∼ 16 km in summer from the AVK FWHMs, are coarser than for the O 3 wind retrievals whereas the observation errors are smaller at ∼ 3 m s −1 in both winter and summer conditions at Halley. Our simulated wind retrieval is comparable to the polar mesospheric wind speeds above the South Pole determined with uncertainty ± 5 m s −1 by observing the CO line at 461 GHz (Burrows et al, 2007).…”

“…Le Pichon et al, 2010;Assink et al, 2012Assink et al, , 2013Chunchuzov et al, 2015). Over a 14-year period the space-borne high-resolution Doppler imager (HRDI) (Burrage et al, 1996) measured wind velocities typically between 60 • N and 60 • S and down to 50 km and contributed to the Upper Atmosphere Research Satellite (UARS) Reference Atmosphere Project (URAP) (Swinbank and Ortland, 2003) wind climatology. Also on UARS, the limb-sounding WIND Imaging Interferometer (WINDII) observed O( 1 S) airglow emission to measure winds over 90-110 km (Gault et al, 1996b).…”

“…The frequency shifts are small, in the range 5 to 200 kHz, but can be measured precisely using stable, high-resolution digital fast Fourier transform spectrometers (Klein et al, 2012). Wind speeds at 70-85 km above the South Pole were determined with uncertainty ±5 m s −1 by observing the carbon monoxide (CO) line at 461 GHz (Burrows et al, 2007). Rüfenacht et al (2012Rüfenacht et al ( , 2014 used observations of the O 3 microwave emission line at 142.18 GHz by the ground-based wind radiometer (WIRA), and optimal estimation retrieval, to measure daily mean zonal and meridional wind profiles.…”

MF and HF radar techniques for investigating the dynamics and structure of the 50 to 110 km height region: a review

“…Burrage et al (1996) concluded that the HDRI results were more consistent with falling sphere measurements and with WINDII measurements and so by inference that MF wind magnitudes were too small. It is worth noting that the HRDI measurements represented averages over several hundred kilometers in the meridional direction.…”

“…Intercomparisons between HRDI and a number of MF/HF SA FCA radars found that mean and tidal component winds in the satellite instrument were larger than the corresponding radar winds (e.g., Khattatov et al 1996), and Burrage et al (1996) concluded that HRDI measured larger winds than MF radars, but that the size of the difference varied from radar to radar. Burrage et al (1996) concluded that the HDRI results were more consistent with falling sphere measurements and with WINDII measurements and so by inference that MF wind magnitudes were too small.…”