An Analysis of Tropical Transport: Influence of the Quasi-biennial Oscillation

An analysis of over 4 years of Upper Atmosphere Research Satellite (UARS) measurements of CH4, HF, O3, and zonal wind are used to study the influence of the quasi-biennial oscillation (QBO) on constituent transport in the tropics. At the equator, spectral analysis of the Halogen Occultation Experiment (HALOE) and Microwave Limb Sounder (MLS) observations reveals QBO signals in constituent and temperature fields at altitudes between 20 and 45 km. Between these altitudes, the location of the maximum QBO amplitude roughly corresponds with the location of the largest vertical gradient in the constituent field. Thus, at 40 km where CH4 and HF have strong vertical gradients, QBO signals are correspondingly large, while at lower altitudes where the vertical gradients are weak, so are the QBO variations. Similarly, ozone, which is largely under dynamical control below 30 km in the tropics, has a strong QBO signal in the region of sharp vertical gradients (∼28 km) below the ozone peak. Above 35 km, annual and semi-annual variations are also found to be important components of the variability of long-lived tracers. Therefore, above 30 km, the variability in CH4 and HF at the equator is represented by a combination of semiannual, annual, and QBO timescales. A one-dimensional vertical transport model is used to further investigate the influence of annual and QBO variations on tropical constituent fields. QBO-induced vertical motions are calculated from observed high resolution Doppler imager (HRDI) zonal winds at the equator, while the mean annually varying tropical ascent rate is obtained from the Goddard two-dimensional model. Model simulations of tropical CH4 confirm the importance of both the annual cycle and the QBO in describing the HALOE CH4 observations above 30 km. Estimates of the tropical ascent rate and the variation due to the annual cycle and QBO are also discussed

TIMED Doppler Interferometer: Overview and recent results

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94617/1/jgra18230.pd

Global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide: 2. Nonmigrating tide

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94716/1/jgra18976.pd

Global distribution and interannual variations of mesospheric and lower thermospheric neutral wind diurnal tide: 1. Migrating tide

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95689/1/jgra18975.pd

Comparison of mesospheric and lower thermospheric residual wind with High Resolution Doppler Imager, medium frequency, and meteor radar winds

The objective of this study is to compare observed mean meridional winds with those deduced from theory. The diabatic circulation is computed from High Resolution Dopper Imager (HRDI) mesospheric and lower thermospheric temperatures during January and July conditions. The meridional wind component is compared with HRDI Eulerian mean meridional winds near 95 km and with seasonal averages of meridional winds at a number of radar medium-frequency (MF) and meteor wind (MW) sites. The diabatic wind is directed from the summer toward the winter hemisphere. Peak values exceed 20 m s−1 and are observed at 105 km near 20° in the summer hemisphere. A secondary maximum of about 10 m s−1 is observed in the wintertime lower mesosphere during the July case. The diabatic wind is qualitatively consistent with HRDI 95-km mean meridional winds at latitudes equatorward of 50°. Time-averaged summertime radar winds are consistent with HRDI and diabatic winds between 50°S and 20°N. At winter midlatitudes, MF radar winds are directed oppositely to the diabatic wind, while one available MW measurement is directed with the diabatic wind. The zonal acceleration implied by the diabatic wind is about 150–200 m s−1 d−1 in the midlatitude summer lower thermosphere.R. S. Lieberman, A. K. Smith, S. J. Franke, R. A. Vincent, J. R. Isler, A. H. Manson, C. E. Meek, G. J. Fraser, A. Fahrutdinova, T. Thayaparan, W. Hocking, J. MacDougall, T. Nakamura, and T. Tsud

Mesosphere/lower thermosphere prevailing wind model

The mesosphere/lower thermosphere (MLT) wind data from the 46 ground-based (GB) MF and meteor radar (MR) stations, located at the different latitudes over the globe, and the space-based (SB) HRDI data were used for constructing of the empirical global climatic 2-D prevailing wind model at 80-100 km heights for all months of the year. The main data set is obtained during 1990-2001 period. It is shown that the three datasets (MF, MR, HRDI) are mainly well correlated. However, a certain systematic bias between the GB and SB data at 96 km exists, as well as that between the MF and MR data higher 88 km. Simple correction factors are proposed to minimize these biases. The 2-D distant-weighted least-square interpolation procedure for some arbitrary collection of points was used for drawing model contour plots. The model is available in the computer readable form and may be used for construction of the new CIRA model. © 2004 COSPAR. Published by Elsevier Ltd. All rights reserved