GEOPHYSICAL RESEARCH LETTERS, VOL. 22, NO. 20, PAGES 2825-2828, OCTOBER 15, 1995 Lidar observations of the temperature profile between 25 and 103 km: evidence of strong tidal perturbation Phan D. Dao and Robert Farley Phillips Laboratory, Geophysics Directorate Xin Tao and Chester S. Gardner University of Illinois at Urbana-Champaign Abstract. Simultaneous observations of the mid- dle atmosphere and lower thermosphere by Na Wind/Temperature (W/T) and Rayleigh/Raman lidar and other ground-based measurements wereconducted the night of October 21, during the ALOHA-93 cam- paign. Rayleigh/Raman lidar measurements provide densityfrom 25 to 90 km and temperaturefrom 25 to 85 km. From the samelocation,Na W/T lidar mea- surements were also obtained between ~ 83 and 103 km. The combined data provides continuous temper- ature from 25 to 103 km. Strong perturbations which may be associated with the diurnal tide are observed in the temperature and wind profiles. Introduction Atmospheric waves dominatethe variability of den- sity and temperature structure in the middle atmo- sphereand lower thermosphere and present a serious challenge to the modeling of atmospheric parameters in thisregion. To ameliorate the situation, more dataare neededto validate modelscurrently in use or under de- velopment in support of space operations [Killeen, et al., 1993]. While lidar diagnostics provide the conve- nience and cost-effectiveness of repetitive ground-based measurement of atmospheric conditions [Gille ei al., 1991], the goal of obtaining extensive and validated data continuously from the troposphere to the lowerthermo- sphere hasbeenfrustratedby a gapin the measurement range. With the exception of systems with very large telescope apertures [Meriwether et al., 1994], Rayleigh lidar has provided density/temperature mainly in the altitude rangefrom 20 to 70 km, while Na lidar covers the range from80 to 105 km [Fricke et al., 1985; Bills et al., 1993]. Because of thegap in databetween 70 and 80 km, continuous measurements through out the 20-105 km regionhave not been possible. Furthermore, the technique for measuring temperaturewith a Rayleigh lidar also requiresexperimentalvalidation. Tempera- ture is derived from Rayleigh lidar signal based on (a) a plausible assumption of idealgas andhydrostatic equi- Copyright 1995 by theAmerican Geophysical Union. Paper number 95GL02950 0094-8534/95/95GL-02950503.00 librium and'(b) an assumed temperature at its upper bound. The validity of the first assumption neverthe- lessdemandsexperimental confirmationwhich is made possible in ALOHA-93 because Rayleigh and Na tem- perature measurements are conducted simultaneously at a single location. With temperatureavailable at 84 km by the Na W/T lidar, the derivation of temperature for the Rayleigh lidar is entirely based on measurement. The validation is further confirmed by comparison with collocatedOH temperatures measuredby the Univer- sity of Western Ontario (UWO) [Lowe et al., this is- sue] and the Aerospace Corporation [Hecht et al., this issue].The combined Rayleigh-Na W/T lidar, to our best knowledge the first to measure temperature from 25 to 103 km and wind from 85 to 103 km, is shown to provide critical and comprehensive data on middle atmosphere dynamics. System Description and Measurements The Phillips Laboratory (PL) Rayleigh lidar system was moved to the Air Force Maul Optical Site(AMOS), Haleakala (20.7N and 203.7E),Maul, June1993 in sup- port of ALOHA-93. The campaignwas scheduled for measurement from September 27 to November3, 1993. A Nd:YAG laser, Quantel 581C, wasusedat 532 nm for Rayleighand N2 Raman measurements. A lidar detec- tor module was built for the appropriate wavelengths: 532 and 618 nm and mounted on the 1.6 m telescope, lidar receiver, operated by the PL AMOS team. The av- eragelaser power is 3 W and the lidar power-aperture product is 6 Wm •. Rayleigh data is recorded with a vertical resolutionof 150 m and 2 minute temporal res- olution. To obtain significant statistics,data is further smoothed to 3 km and 30 minute resolutions. With those resolutions, the photon count at 80 km is 1040 or a Rayleigh S/N ratio of 32. During ALOHA-93, the University of Illinois (UI) operated a Na density lidar aboard the NCAR Electra aircraft and a Na W/T lidar at the Air Force Maul Optical Site near the summit of Haleakala at an altitude of 3055 m. The Na W/T lidar was interfaced with the 0.8 m diameter Beam Direc- tor Telescope which provided full scanning capabilities. The lidaf was pointed sequentially at zenith and 15 de- grees off zenith to the north and east so that tempera- ture and all three components of the wind vector could be measured.The average laserpower was 1 W yielding a power-aperture product of 0.5 Wm2. The data were smoothed yielding profileswith a vertical resolutionof 2825