Climatology of migrating and non-migrating tides observed by three meteor radars in the southern equatorial region

Abstract. We present a study of migrating and non-migrating tidal winds observed simultaneously by three meteor radars situated in the southern equatorial region. The radars are located at Cariri (7.4° S, 36.5° W), Brazil, Kototabang (0.2° S, 100.3° E), Indonesia and Darwin (12.3° S, 130.8° E), Australia. Harmonic analysis was used to obtain amplitudes and phases for diurnal and semidiurnal solar migrating and non-migrating tides between 80 and 100 km altitude during the period 2005 to 2008. They include the important tidal components of diurnal westward-propagating zonal wavenumber 1 (DW1), diurnal eastward-propagating zonal wavenumber 3 (DE3), semidiurnal westward-propagating zonal wavenumber 2 (SW2), and semidiurnal eastward-propagating zonal wavenumber 2 (SE2). In addition, we also present a climatology of these wind tides and analyze the reliability of the fitting through the reference to Whole Atmosphere Community Climate Model (WACCM) winds. The analysis suggests that the migrating tides could be well fitted by the three different radars, but the non-migrating tides might be overestimated. The results based on observations were also compared with the Climatological Tidal Model of the Thermosphere (CTMT). In general, climatic features between observations and model migrating tides were satisfactory in both wind components. However, the features of the DW1, DE3 and SW2 amplitudes in both wind components were slightly different from the results of the CTMT models. This result is probably because tides could be enhanced by the 2006 northern hemisphere stratospheric sudden warming (NH-SSW) event.

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On the Momentum Budget of the Quasi-Biennial Oscillation in the Whole Atmosphere Community Climate Model

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0088.1 ◽

2018 ◽

Vol 76 (1) ◽

pp. 69-87 ◽

Cited By ~ 24

Author(s):

Rolando R. Garcia ◽

Jadwiga H. Richter

Keyword(s):

Gravity Waves ◽

Climate Model ◽

Equatorial Waves ◽

Quasi Biennial Oscillation ◽

Community Climate Model ◽

Westerly Jet ◽

Momentum Budget ◽

Zonal Wavenumber ◽

Biennial Oscillation ◽

Community Climate

Abstract This study documents the contribution of equatorial waves and mesoscale gravity waves to the momentum budget of the quasi-biennial oscillation (QBO) in a 110-level version of the Whole Atmosphere Community Climate Model. The model has high vertical resolution, 500 m, above the boundary layer and through the lower and middle stratosphere, decreasing gradually to about 1.5 km near the stratopause. Parameterized mesoscale gravity waves and resolved equatorial waves contribute comparable easterly and westerly accelerations near the equator. Westerly acceleration by resolved waves is due mainly to Kelvin waves of zonal wavenumber in the range k = 1–15 and is broadly distributed about the equator. Easterly acceleration near the equator is due mainly to Rossby–gravity (RG) waves with zonal wavenumbers in the range k = 4–12. These RG waves appear to be generated in situ during both the easterly and westerly phases of the QBO, wherever the meridional curvature of the equatorial westerly jet is large enough to produce reversals of the zonal-mean barotropic vorticity gradient, suggesting that they are excited by the instability of the jet. The RG waves produce a characteristic pattern of Eliassen–Palm flux divergence that includes strong easterly acceleration close to the equator and westerly acceleration farther from the equator, suggesting that the role of the RG waves is to redistribute zonal-mean vorticity such as to neutralize the instability of the westerly jet. Insofar as unstable RG waves might be present in the real atmosphere, mixing due to these waves could have important implications for transport in the tropical stratosphere.

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Middle Atmosphere Response to ENSO Events in Northern Hemisphere Winter by the Whole Atmosphere Community Climate Model

ATMOSPHERE-OCEAN ◽

10.1080/07055900.2011.576451 ◽

2011 ◽

Vol 49 (2) ◽

pp. 95-111 ◽

Cited By ~ 2

Author(s):

Chunhui Lu ◽

Yi Liu ◽

Chuanxi Liu

Keyword(s):

Northern Hemisphere ◽

Climate Model ◽

Middle Atmosphere ◽

Community Climate Model ◽

Enso Events ◽

Hemisphere Winter ◽

Northern Hemisphere Winter ◽

Community Climate

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Quasi-Stationary Regimes in the Northern Hemisphere of the NCAR Community Climate Model

Journal of Climate ◽

10.1175/1520-0442(1988)001<0406:qsritn>2.0.co;2 ◽

1988 ◽

Vol 1 (4) ◽

pp. 406-417 ◽

Cited By ~ 2

Author(s):

Timothy W. Barker ◽

John D. Horel

Keyword(s):

Northern Hemisphere ◽

Climate Model ◽

Community Climate Model ◽

Community Climate

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Wintertime Northern Hemisphere Response in the Stratosphere to the Pacific Decadal Oscillation Using the Whole Atmosphere Community Climate Model

Journal of Climate ◽

10.1175/jcli-d-15-0176.1 ◽

2016 ◽

Vol 29 (3) ◽

pp. 1031-1049 ◽

Cited By ~ 24

Author(s):

A. C. Kren ◽

D. R. Marsh ◽

A. K. Smith ◽

P. Pilewskie

Keyword(s):

Northern Hemisphere ◽

Pacific Decadal Oscillation ◽

El Niño ◽

Climate Model ◽

El Nino ◽

Positive Phase ◽

Late Winter ◽

Community Climate Model ◽

The Pacific ◽

Community Climate

Abstract The response of the Northern Hemisphere winter stratosphere to the Pacific decadal oscillation (PDO) is examined using the Whole Atmosphere Community Climate Model. A 200-yr preindustrial control simulation that includes fully interactive chemistry, ocean and sea ice, constant solar forcing, and greenhouse gases fixed to 1850 levels is analyzed. Based on principal component analysis, the PDO spatial pattern, frequency, and amplitude agree well with the observed PDO over the period 1900–2014. Consistent with previous studies, the positive phase of the PDO is marked by a strengthened Aleutian low and a wave train of geopotential height anomalies reminiscent of the Pacific–North American pattern in the troposphere. In addition to a tropospheric signal, a zonal-mean warming of about 2 K in the northern polar stratosphere and a zonal-mean zonal wind decrease of about 4 m s−1 in the PDO positive phase are found. When compositing PDO positive or negative winters during neutral El Niño years, the magnitude is reduced and depicts an early winter forcing of the stratosphere compared to a late winter response from El Niño. Contamination between PDO and ENSO signals is also discussed. Stratospheric sudden warmings occur 63% of the time in the PDO positive phase compared to 40% in the negative phase. Although this sudden warming frequency is not statistically significant, it is quantitatively consistent with NCEP–NCAR reanalysis data and recent observational evidence linking the PDO positive phase to weak stratospheric vortex events.

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