Mean winds and tides in the upper middle atmosphere at Urbana (40°N, 88°W) during 1991–1992

Abstract

A summary of the first 18 months of continuous wind observations using the Urbana medium frequency (MF) radar is presented. Emphasis is placed on height-time contours of monthly mean winds and on amplitudes and phases of 24 hour and 12 hour tides. Results are compared with data from other midlatitude stations and models. Below 85 kin, monthly mean winds are shown to agree closely with the zonal mean, geostrophic wind model CIRA86. Significant dis•ancies above 85 km have been noted in comparisons between CIRA86 and the other mesosphere-!ower-thermosphere (MLT) radar stations (including MF, meteor, and low-frequency (IF)refers)and are also sustained in the observations reported here. Tidal characteristics are generally consistent with other midlatitude observations, although significant differences are noted between Urbana and its closest MLT network neighbor station (Durham, 43øN, 71øW). The mean wind observations provide a context for the gravity wave climatology derived from Na lidar observations at Urbana and promise to contribute toward improvements of middle atmosphere wind and tidal models. INTRODUCTIONThe past 20 years have been characterized by rapid improvements in the quantity and quality of observational data pertaining to mean winds and tides in the middle atmosphere.A variety of radar techniques have contributed measurements of winds in the 60 to 100 km altitude region, and a few stations have been collecting such data for a number of years. Under the auspices of the Middle Atmosphere Program (MAP), techniques used for the extraction of information from winds measured by radar techniques were improved and standardized.These studies showed that continuous measurements in both height and time are extremely useful for studying the longperiod oscillations in the middle atmosphere. The MAP studies revealed a need for a more complete global network of radars that can provide temporally continuous wind data. Manson et al. [1985aManson et al. [ , 1990Manson et al. [ , 1991 have compiled a detailed comparison of the mean winds obtained from midlatitude radar observations, and Manson et el. [1991] report detailed comparisons between observations and CLRA1986. In another study, Manson et el. [1989] summarized and compared semidiurnal and diurnal tidal climatologies derived from radar measurements at middle latitudes. The radar climatologies were also compared with the most current tidal models. In this paper we concentrate on descriptive analysis of the monthly mean winds and tidal parameters at Urbana and also compare and contrast the observations with those reported by other midlatitude stations. The mean wind and tidal climatology data presented here are intended to complement those presented by Manson et at. [1989, I991] and add one more midlatitude data point to the developing picture of midlatitude mesospheric dynamics. It is expected that the continuous data set being collected at Urbana, when combined with data collected at other midlatitude stations, will provide much useful information on the Copyfight...

A new approach to MF radar interferometry for estimating mean winds and momentum flux

“…The climatology of mesospheric winds observed at Urbana has been previously derived using the spaced antenna full correlation analysis technique [Franke and Thorsen, 1993]. The SA-FCA climatology, consisting of monthly means obtained by averaging 5-min velocity estimates, is compared here with the time domain interferometry technique.…”

“…Over the past few decades, long-term climatologies of the mesospheric circulation generated by medium frequency (MF) radars employing the spaced antenna full correlation analysis (SA-FCA) technique have played a fundamental role in strengthening our understanding of mesospheric dynamics [ Gregory and Manson, 1975;Manson et al, 1985Manson et al, , 1991Franke and Thorsen, 1993]. At the same time, the effects of external noise, radar antenna geometry, and signal processing (e.g., finite record length, sampling interval, filtering) on the SA-FCA technique have been investigated [Golley and Rossiter, 1970 …”

Climatology and modeling of quasi‐monochromatic atmospheric gravity waves observed over Urbana Illinois

“…The operation of the MF radar to obtain atmospheric winds is discussed by Franke and Thorsen [1993]. For this paper the 12 individual month composite days are used which are derived from a seven year climatology.…”

Comparison of terdiurnal tidal oscillations in mesospheric OH rotational temperature and Na lidar temperature measurements at mid-latitudes for fall/spring conditions

“…) and appear to propagate westwards following the motion of the Sun (e.g., Chapman and Lindzen, 1970). Remote sensing investigations of the MLT region using ground-based radar (e.g., Avery et al, 1989;Vincent et al, 1989;Franke and Thorsen, 1993;Thayaparan, 1997) and spaceborne optical sensors on the Upper Atmospheric Research Satellite (UARS) (e.g., Hays et al, 1994;Burrage et al, 1995;Shepherd et al, 1995;McLandress et al, 1996;Geller et al, 1997) have provided a wealth of data on the local time and global scale effects of solar tides on the wind field. Together with recent model developments such as the Global Scale Wave Model (GSWM) Hagan, 1996), these studies have revealed a complex, yet understandable, mean global variation Copy right c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.…”