HR: 1400h
AN: SA53B-01    [Abstracts]
TI: Tropical tides and thermal structure in MLT region observed by lidars and SABER at Arecibo, Puerto Rico and Maui, Hawaii
AU: * Chu, X
EM: Xinzhao.Chu@Colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, CIRES, Boulder, CO 80309, United States
AU: * Chu, X
EM: Xinzhao.Chu@Colorado.edu
AF: Department of Aerospace Engineering Sciences, University of Colorado, 429 UCB, Boulder, CO 80309, United States
AU: Friedman, J S
EM: jonathan@naic.edu
AF: NAIC Arecibo Observatory, HC-03 Box 53995, Arecibo, PR 00612, United States
AU: Farias Gutierrez, P
EM: Paloma.Farias@colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, CIRES, Boulder, CO 80309, United States
AU: Farias Gutierrez, P
EM: Paloma.Farias@colorado.edu
AF: Department of Aerospace Engineering Sciences, University of Colorado, 429 UCB, Boulder, CO 80309, United States
AU: Zhang, X
EM: zhangx@colorado.edu
AF: Department of Aerospace Engineering Sciences, University of Colorado, 429 UCB, Boulder, CO 80309, United States
AU: Forbes, J M
EM: Forbes@Colorado.EDU
AF: Department of Aerospace Engineering Sciences, University of Colorado, 429 UCB, Boulder, CO 80309, United States
AU: Liu, H
EM: liuh@ucar.edu
AF: High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, United States
AB: A complete range-resolved seasonal climatology of the nocturnal thermal structure in the MLT region (80-105 km) is characterized for the first time at a tropical site Arecibo, PR (18.35°N, 66.75°W) with groundbased nighttime observations from 2004 to 2006 using the Arecibo K Doppler lidar. Several unique features emerge, which are very different from the climatologies obtained by the University of Illinois Na wind and temperature lidar at a mid-latitude site SOR, NM (35°N, 106.5°W) and a sub-tropical site Maui, HI (20.7°N, 156.3°W). First, semiannual variations dominate the seasonal variations at Arecibo with maxima around the equinoxes and minima near the solstices, in contrast to the annual periodicity dominating the SOR seasonal variations. Second, the Arecibo mesopause altitude never drops below 90 km, unlike Maui and SOR that both show a low summer mesopause altitude around 86.5 km. Third, the Arecibo mesospheric inversion layers (MIL) are much weaker than those for SOR and Maui most of the year except summer, when the Arecibo MIL has similar amplitude to SOR and Maui. Fourth, the Arecibo lower thermosphere (100-105 km) exhibits summer cooling, in contrast to the mid- and high-latitude summer warming. Fifth, the Arecibo semidiurnal tides show a nearly 180 degree of phase shift from winter to equinox, which is not observed at SOR and Maui. With assistance from TIMED-SABER temperature data, we investigate to answer the following questions: (1) What effect does the tidal phase have on the observed MIL, and whether the MIL is caused by local gravity wave - tide interactions or by decay of global scale planetary waves? (2) How does the undersampling of the diurnal tides affect the observed mesospheric semi-annual oscillation (MSAO)? (3) Whether the summer cooling in the tropical lower thermosphere is caused by the MSAO-induced cooling/heating or is it an aliasing effect from the semiannual and annual variations of the diurnal tides? (4) Whether the observed temperature differences between Arecibo and Maui--two sites separated only by 2.4 degrees in latitude but by 90 degrees in longitude -- are caused by non-migrating tidal effects.
DE: 0340 Middle atmosphere: composition and chemistry
DE: 3332 Mesospheric dynamics
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3360 Remote sensing
DE: 3389 Tides and planetary waves
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly