Residual Mean Meridional Circulation in the Stratosphere and Upper Troposphere

Seol, Dong-Il; Yamazaki, Koji

doi:10.2151/jmsj1965.77.5_985

Cited by 8 publications

(9 citation statements)

References 16 publications

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“…An intriguing point is that w tr is roughly constant in July. The values are in accordance with other results [ Eluszkiewicz et al , 1996; Seol and Yamazaki , 1999; Randel and Newman , 1999] (Table 1). A tendency to underestimate the seasonal amplitude is observed below 45 hPa in our results.…”

Section: Variability Of Ascent Ratessupporting

confidence: 93%

Seasonal and QBO variations of ascent rate in the tropical lower stratosphere as inferred from UARS HALOE trace gas data

2003

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[1] Seasonal and interannual variations in ascent rates are investigated as a function of latitude and height, using water vapor (H 2 O) and methane (CH 4 ) data from the stratospheric measurements of the Halogen Occultation Experiment (HALOE). The ascent rate is inferred from the ascending signal of variations in the entry value of [H 2 O] + 2[CH 4 ] (Ĥ ). Within ±15°of the equator the derived ascent rate exhibits two kinds of dominant variations with a clear latitudinal structure, seasonal variation, and the quasibiennial oscillation (QBO). The seasonal cycle exhibits a vertically in-phase variation, with a northern winter maximum of 0.2-0.4 mm s À1 and a summer minimum of $0.2 mm s À1 in the 20-60 hPa layer. The latitudinal structure is characterized by an early appearance of a subtropical summer maximum of the ascent rate and by double peaks at 10-15°N and S during the northern winter season. The QBO component of the ascent rate shows tropically confined anomalies with a rapid downward propagation, but mass attenuation anomalies estimated from the ascent rate show a much slower downward propagation. The descent anomalies exhibit a well-structured and equatorially symmetric variation, while the ascent anomalies have a tendency to propagate latitudinally. This might be connected with the phase dependency of the QBO acceleration. An examination of the phase and amplitude of the ascent rate and temperature for both the seasonal and QBO components emphasizes that the radiative damping timescale is considerably long (40-100 days) below 40 hPa.

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Section: Variability Of Ascent Ratessupporting

confidence: 93%

Seasonal and QBO variations of ascent rate in the tropical lower stratosphere as inferred from UARS HALOE trace gas data

2003

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“…It should be noted that the Eliassen-Palm (E-P) flux, residual velocity, and wave-activity flux by Plumb (1985) are calculated from five-day mean data and the monthly average is taken thereafter. The residual velocity is estimated based on the downward control principle (Haynes et al 1991) by integrating transformed Eulerian mean (TEM) equation with the boundary condition of null upward velocity at 0.5 hPa level similar to Soel and Yamazaki (1999). Solar activity on the 11-year time scale is measured using the monthly mean solar microwave flux (with the unit of 10 À22 Wm 2 /Hz) with the wave length of 10.7 cm (called the solar index), produced by the U.S. National Oceanic and Atmospheric Administration (NOAA)/ National Geophysical Data Center (NGDC).…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

Effect of Solar Activity on the Polar-night Jet Oscillation in the Northern and Southern Hemisphere Winter.

Kuroda¹,

Kodera²

2002

JMSJ

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Effect of the modulation of the Polar-night jet oscillation (PJO) in winter time by the 11-year solar cycle is examined by the observational data from 1979 to 1999. It is found that zonal wind and the E-P flux anomalies appear commonly in the subtropical upper stratosphere in early winter of both the Northern and Southern Hemispheres as a response to meridional UV heating contrast. These zonal wind anomalies are found to propagate poleward and downward with development as a seasonal march in both hemispheres. Although the length of the record is limited, it is suggested from the available data that the signal due to solar activity appears as the time evolution of the PJO triggered by solar forcing at early winter in both hemispheres. Differences in the signals between the Northern and Southern Hemispheres during late winter are explained in terms of the different characteristics of the PJO in each hemisphere. A significant temperature signal is also found to appear in the Southern Hemisphere in late winter under a solar maximum condition.

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“…Residual circulation is calculated by iteratively solving the transformed Eulerian momentum and continuity , as by Soel and Yamazaki [1999]. All variables here are the zonal mean.…”

Section: Datamentioning

confidence: 99%

“…It is not always possible to obtain reasonable values in the lower latitudes. One method is to use only recent periods, as by Soel and Yamazaki [1999]. However, at least two solar cycles are needed to distinguish a solar cycle variation from a long‐term trend.…”

Section: Datamentioning

confidence: 99%

Dynamical response to the solar cycle

Kodera¹,

Kuroda²

2002

J.‐Geophys.‐Res.

438

586

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[1] The dynamical impact of the 11-year solar cycle is investigated with the focus on the stratopause region where solar ultraviolet heating is greatest. The most important variation in solar forcing longer than the diurnal cycle is the annual cycle. Thus the climatological features of the zonal wind variation associated with the annual cycle were first studied to characterize the basic features of the atmosphere's dynamical response to changes in solar radiative forcing. The 11-year solar cycle effect was then investigated. The results of the analysis suggest that in a climatological mean state the stratopause circulation evolves from a radiatively controlled state to one dynamically controlled during winter in both hemispheres. The transition period is characterized by a poleward shift of the westerly jet. The solar cycle effect appears as a change in the balance between the radiatively and dynamically controlled states. The radiatively controlled state lasts longer during the solar maximum phase, and the stratopause subtropical jet reaches a higher speed. The large dynamical response to relatively weak radiative forcing may be understood by the bimodal nature of the winter atmosphere due to interaction with meridionaly propagating planetary waves and zonal mean zonal winds. It is suggested that the solar influence produced in the upper stratosphere and stratopause region is transmitted to the lower stratosphere through (1) modulation of the internal mode of variation in the polar night jet and (2) a change in the Brewer-Dobson circulation. The first process is significant in the middle and high latitudes, whereas the latter is prominent in the equatorial region.

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Residual Mean Meridional Circulation in the Stratosphere and Upper Troposphere

Cited by 8 publications

References 16 publications

Seasonal and QBO variations of ascent rate in the tropical lower stratosphere as inferred from UARS HALOE trace gas data

Seasonal and QBO variations of ascent rate in the tropical lower stratosphere as inferred from UARS HALOE trace gas data

Effect of Solar Activity on the Polar-night Jet Oscillation in the Northern and Southern Hemisphere Winter.

Dynamical response to the solar cycle

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