A Diagnostic Study of the Isentropic Zonally Averaged Mass Circulation during the First GARP Global Experiment

Townsend, Raymond J.; Johnson, Donald R.

doi:10.1175/1520-0469(1985)042<1565:adsoti>2.0.co;2

Cited by 85 publications

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“…Climatological mean meridional circulation for the troposphere calculated in this work based on 10 years of analysis has to be compared with the four seasonal means calculated by Townsend and Johnson (1985) from the FGGE data set covering a 12-month period in 1978±1979. It turns out that both results are in qualitative agreement with respect to seasons, branch structure and order of magnitude.…”

Section: Discussionmentioning

confidence: 99%

“…With the steady-state assumption the isentropic mass streamfunction is de®ned according to Townsend and Johnson (1985) by…”

Section: Zonally Averaged Equations and Parameterizationmentioning

confidence: 99%

“…The ratio of those parts increases with decreasing height. Those grounded isentropes are treated with the procedure of Lorenz (1955) and Andrews (1983) [see also Juckes et al (1994) and Townsend and Johnson (1985) …”

Section: Zonally Averaged Equations and Parameterizationmentioning

confidence: 99%

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Climatological Ertel's potential-vorticity flux and mean meridional circulation in the extratropical troposphere − lower stratosphere

Bartels

Peters²,

Schmitz³

1998

Ann. Geophys.

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Abstract.We investigated to what extent the isentropic, non-geostrophic formulation of zonally averaged circulation derived for stratospheric conditions is applicable to climatological transport in the extratropical troposphere and lower stratosphere. The study is based on 10 years of daily data of ECMWF analysis and on the ECHAM3 climate model of the German Climate Computing Centre. The main result is a scalar isentropic mixing coecient, u yy , and a mean meridional transport circulation consistently derived from the same data base. For both data sources, isentropic mean meridional circulation is derived from horizontal mass¯ow rate for 4 representative months. Alternatively, a mean meridional circulation is calculated from total diabatic heating rates of the ECHAM3 model. It is shown that only the latter is in good agreement with the ECMWF mean meridional circulation. Isentropic analysis also comprises the seasonal cycle of the climatological meridional gradient and¯ux of Ertel's potential vorticity (PV). Application of Tung's¯ux-gradient relation yields that for all seasons u yy is positive in heightlatitude regions where statistical signi®cance is reached. Large u yy values, marking regions of more ecient mixing, have been found in the subtropical vertical band of weak westerly wind and in mid-latitudes in regions of upward-propagating baroclinic wave activity in the middle and upper troposphere. Based on the ECMWF data and results of baroclinic-wave behaviour, strong indications are presented that positive zonally averaged PV¯ux polewards of the jet core in the NH is strengthened by stationary waves and nonlinear eects. Reduced eddy transport is apparent in winter and spring slightly below the subtropical tropopause jet. The seasonal cycle of u yy from ECHAM3 data is to a great extent in agreement with the result based on ECMWF analysis. In the model, reduced interannual variability enlarges the height-latitude range where sign of u yy is signi®cant.

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Section: Discussionmentioning

confidence: 99%

“…With the steady-state assumption the isentropic mass streamfunction is de®ned according to Townsend and Johnson (1985) by…”

Section: Zonally Averaged Equations and Parameterizationmentioning

confidence: 99%

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Climatological Ertel's potential-vorticity flux and mean meridional circulation in the extratropical troposphere − lower stratosphere

Bartels

Peters²,

Schmitz³

1998

Ann. Geophys.

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“…These considerations of Charney's mode account well for the structure of the extratropical direct circulation and the EP flux divergence obtained in this analysis, particularly in very thin equatorward flows near the lower boundary. Townsend and Johnson (1985) obtained mean mass circulations on isentropic surface from wind and temperature fields of the FGGE datasets. Their results showed an extratropical direct cell in the winter hemispheric troposphere in accordance with the present result.…”

Section: Discussionmentioning

confidence: 99%

General Circulation Diagnosis in the Pressure-Isentrope Hybrid Vertical Coordinate

Iwasaki

1992

Journal of the Meteorological Society of Japan

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The mean-meridional circulation and wave-mean flow interactions in the pressure-isentrope hybrid coordinate (pt) are investigated through an analysis of an annual run of a general circulation model (NCAR CCM1). Special attention is paid to seasonal variations of the circulation and their comparisons between the northern and southern hemispheres.In the troposphere, there are two types of direct circulations, namely, the Hadley cells in low latitudes and direct cells in the extratropics. The latter are almost confined to the troposphere, become strong in winter and have nearly equal magnitude in the two winter hemispheres. These findings indicate that the extratropical cells come mainly from baroclinic instability waves.The stratospheric circulation is of the Brewer-Dobson type and, however, its seasonal evolution is considerably different between the two hemispheres due to the difference in wave activity. The extratropical downward flows in the NH winter are stronger than those in the SH winter and, hence, the global stratosphere-troposphere exchange rate of the air mass has a maximum in the NH winter. Especially inside of the SH circumpolar vortex, downward flows are so weak that the lower stratospheric temperature becomes very low. Such NH-SH asymmetries of downward flows in winter may cause the seasonal variation of the stratospheric temperature even in the tropics through changing tropical upward flows.

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“…The mass-weighted isentropic zonal mean (MIM) enables us to describe the Lagrangian mean meridional circulation (Gallimore et al 1981;Andrews 1983;Townsend et al 1985;Tung 1986;Iwasaki 1989Iwasaki , 1990Iwasaki and 1992Juckes et al 1994;Juckes 2001). In MIM, very differently from the conventional zonal mean, the mass stream function has a distinct extratropical tropospheric direct (ETD) circulation in the winter hemispheres, in addition to the Hadley circulation (Iwasaki 1989 and1992;Juckes et al 1994;Juckes 2001).…”

Section: Introductionmentioning

confidence: 99%

Mass-Weighted Isentropic Zonal Mean Equatorward Flow in the Northern Hemispheric Winter

Iwasaki

Mochizuki

2012

SOLA

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In the diagnosis of mass-weighted isentropic zonal mean (MIM), the mean-meridional circulation has a strong extratropical direct (ETD) cell in the northern-hemispheric winter, which turns from downward to equatorward around 45°N and isentropic zonal mean pressure of 850 hPa. The January mean equatorward flow in the extratopical lower troposphere is almost in balance with Eliassen-Palm (E-P) flux divergence for both climatology and interannual variability. This means that the zonal mean equatorward flow in the extratropical lower troposphere is the wave-induced circulation as well as the poleward flow in the stratosphere is.The interannual variation of January mean mass stream functions at (45°N, 850 hPa) positively (negatively) correlates with the zonal mean temperature in the lower troposphere north (south) of about 45°N, respectively. This is consistent with a simple thermodynamic consideration that the strong ETD circulation adiabatically warms up the lower troposphere due to the descending flow in the higher latitudes but cools it down due to the heat advection by the equatorward flow in the middle latitudes (~35°N).

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A Diagnostic Study of the Isentropic Zonally Averaged Mass Circulation during the First GARP Global Experiment

Cited by 85 publications

References 0 publications

Climatological Ertel's potential-vorticity flux and mean meridional circulation in the extratropical troposphere − lower stratosphere

Climatological Ertel's potential-vorticity flux and mean meridional circulation in the extratropical troposphere − lower stratosphere

General Circulation Diagnosis in the Pressure-Isentrope Hybrid Vertical Coordinate

Mass-Weighted Isentropic Zonal Mean Equatorward Flow in the Northern Hemispheric Winter

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