scholarly journals Estimation of the equivalent Rayleigh friction in mesosphere/lower thermosphere region from the migrating diurnal tides observed by TIMED

2009 ◽  
Vol 114 (D23) ◽  
Author(s):  
Jiyao Xu ◽  
A. K. Smith ◽  
H.-L. Liu ◽  
W. Yuan ◽  
Qian Wu ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Rayleigh Friction ◽  
Diurnal Tides

scholarly journals Global distributions of diurnal and semi-diurnal tides: observations from HRDI-UARS of the MLT region

2002 ◽  
Vol 20 (11) ◽  
pp. 1877-1890 ◽  
Author(s):  
A. H. Manson ◽  
Y. Luo ◽  
C. Meek
Keyword(s):  
Seasonal Changes ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Wave Model ◽  
Global Scale ◽  
Radio Science ◽  
Contour Maps ◽  
June July ◽  
Longitudinal Variability ◽  
Diurnal Tides

Abstract. HRDI (High Resolution Doppler Interferometer-UARS) winds data have been analyzed in 4° latitude by 10° longitude cells at 96 km to obtain global contour maps of solar-tidal amplitudes and phases, and also mean winds. The solstices June–July (1993), December–January (1993–1994), and one equinox September–October (1994) are shown.  The 24-h diurnal tide that maximizes near the 20–25° latitude has significant seasonal changes with equinoctial maxima, and very clear longitudinal variability. Maxima are very clear over the oceans. In contrast, the 12-h semi-diurnal tides that maximize near the 40–55° latitude have very strong seasonal changes with winter maxima, and more modest longitudinal changes. The similarities with MLT (mesosphere-lower thermosphere) radar observations (90 km) and the GSWM (Global Scale Wave Model) are very satisfactory. The mean winds are consistent with expectations and show clear poleward flow from summer to winter hemispheres in the solstices.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides) Radio science (remote sensing)

Planetary wave-tide nonlinear interactions increase the variety of MLT waves in summer 2019

2021 ◽  
Author(s):  
Maosheng He ◽  
Jorge L. Chau ◽  
Jeffrey M. Forbes ◽  
Denise Thorsen ◽  
Guozhu Li ◽  
...  
Keyword(s):  
Planetary Wave ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Diurnal Tide ◽  
Nonlinear Interactions ◽  
Zonal Wavenumber ◽  
Spectral Peaks ◽  
Northern Hemispheric ◽  
Mesosphere And Lower Thermosphere ◽  
Diurnal Tides

<p>Mesospheric winds collected by multiple meteor radars at mid-latitudes in the northern hemispheric are combined to investigate wave activities in June—October 2019. Dual-station approaches are developed and implemented to diagnose zonal wavenumber $m$ of spectral peaks.  In  September—October, diagnosed are quasi‐10‐ and 6‐day planetary waves (Q10DW and Q6DW, $m=$1), solar semi-diurnal tides with $m=$1, 2, 3 (SW1, SW2, and SW3), lunar semi-diurnal tide, and the upper and lower sidebands (USB and LSB, $m=$ 1 and 3) of Q10DW‐SW2 nonlinear interactions.  During June— September, diagnosed are Rossby-gravity modes ($m=$3 and 4 at periods $T=$ 2.1d and 1.7d), and their USBs and LSBs generated from interactions with diurnal, semi-diurnal, ter-diurnal, and quatra-diurnal migrating tides. These results demonstrate that the planetary wave-tide nonlinear interactions significantly increase the variety of waves in the mesosphere and lower thermosphere region (MLT).</p>

scholarly journals On the Dynamical Control of the Mesosphere–Lower Thermosphere by the Lower and Middle Atmosphere

2017 ◽  
Vol 74 (3) ◽  
pp. 933-947 ◽  
Author(s):  
Anne K. Smith ◽  
Nicholas M. Pedatella ◽  
Daniel R. Marsh ◽  
Tomoko Matsuo
Keyword(s):  
Gravity Wave ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Wave Drag ◽  
Error Growth ◽  
Vertical Range ◽  
Rayleigh Friction ◽  
Mesosphere And Lower Thermosphere ◽  
Dynamical Control

Abstract The NCAR Whole Atmosphere Community Climate Model (WACCM) is used to investigate the dynamical influence of the lower and middle atmosphere on the upper mesosphere and lower thermosphere. In simulations using a methodology adapted from the “specified dynamics” (nudged) version of the model, horizontal winds and temperature over part of the vertical range of the atmosphere are relaxed toward results from a previous simulation that serves as the true simulation, equivalent to meteorological analysis. In the upper mesosphere, the magnitude of the divergence of the constrained simulations from the true simulation depends on the vertical extent and frequency of the data used for nudging the model and grows with altitude. The simulations quantify the error growth of the model dynamical fields when data and forcing terms are known exactly and there are no model biases. The error growth rate and the ultimate discrepancy between the nudged and true fields depend strongly on the method used for representing gravity wave drag. The largest error growth occurs when the gravity wave parameterization uses interactive wave sources that depend on convective activity or fronts. Errors are reduced when the same parameterization is used with smoothly varying specified wave sources. The smallest errors are seen when the parameterized gravity wave drag is replaced by linear Rayleigh friction damping on the wind speed. These comparisons demonstrate the role of gravity waves in transporting the variability of the troposphere into the mesosphere and lower thermosphere.

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