A Technique for Representing Three-Dimensional Vertical Circulations in Baroclinic Disturbances

Keyser, Daniel; Schmidt, Brian D.; Duffy, Dean G.

doi:10.1175/1520-0493(1989)117<2463:atfrtd>2.0.co;2

Cited by 50 publications

(33 citation statements)

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“…To apply the Helmholtz decomposition (Keyser et al, ; Schwendike et al, ), we calculate the overturning stream function at each longitude as

Ψ_{ϕ} = \frac{1}{g} \int \frac{p}{0} v_{d} italicdp

, where v d is the meridional component of the divergent wind only. Here dp is calculated as the pressure at each level minus the pressure of the level above (or minus zero in the case of the topmost pressure level).…”

Section: Methodsmentioning

confidence: 99%

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Regional Widening of Tropical Overturning: Forced Change, Natural Variability, and Recent Trends

et al. 2019

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The width of the tropical Hadley circulation (HC) has garnered intense interest in recent decades, owing to the emerging evidence for its expansion in observations and models and to the anticipated impacts on surface climate in its descending branches. To better clarify the causes and impacts of tropical widening, this work generalizes the zonal mean HC to the regional level by defining meridional overturning cells (RC) using the horizontally divergent wind. The edges of the RC are more closely connected to surface hydroclimate than more traditional metrics of regional tropical width (such as the sea level pressure ridge) or even than the zonal mean HC. Simulations reveal a robust weakening of the RC in response to greenhouse gas increases, along with a widening of the RC in some regions. For example, simulated widening of the zonal mean HC in the Southern Hemisphere appears to arise in large part from regional overturning anomalies over the Eastern Pacific, where there is no clear RC. Unforced interannual variability in the position of the zonal mean HC edge is associated with a more general regional widening. These distinct regional signatures suggest that the RCs may be well suited for the attribution of observed circulation trends. The spatial pattern of regional meridional overturning trends in reanalyses corresponds more closely to the pattern associated with unforced interannual variability than to the pattern associated with CO2 forcing, suggesting a large contribution of natural variability to the recent observed tropical widening trends.

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“…To apply the Helmholtz decomposition (Keyser et al, ; Schwendike et al, ), we calculate the overturning stream function at each longitude as

Ψ_{ϕ} = \frac{1}{g} \int \frac{p}{0} v_{d} italicdp

Section: Methodsmentioning

confidence: 99%

“…To apply the Helmholtz decomposition (Keyser et al, 1989;Schwendike et al, 2014), we calculate the overturning stream function at each longitude as…”

Section: The Helmholtz Decompositionmentioning

confidence: 99%

Regional Widening of Tropical Overturning: Forced Change, Natural Variability, and Recent Trends

et al. 2019

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“…Our objective is to check whether the above interpretations of the classical ageostrophic circulations are still valid, despite the subtropical jet streak being embedded in a slight cyclonically curved flow. Readers are referred to Keyser et al [1989] and Loughe et al [1995] for full details on the method. January 12 (Figure 10a), and at 0000 UTC, January 13 (Figure 10b).…”

Section: The Low-level Return Branch Of This Direct Circulation Occursmentioning

confidence: 99%

Ozone peaks associated with a subtropical tropopause fold and with the trade wind inversion: A case study from the airborne campaign TROPOZ II over the Caribbean in winter

Gouget¹,

Cammas²,

Marenco³

et al. 1996

J. Geophys. Res.

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Aircraft measurements of ozone, methane, carbon monoxide, relative humidity, and equivalent potential temperature were performed during the TROPOZ II campaign. During the aircraft descent down to Pointe-h-Pitre (16.3øN, 61.5øW), at 2100 UTC on January 12, 1991, two ozone peaks (75 ppb) are observed, one at an altitude of 7.5 km and the other at 3.0 km. A physicochemical interpretation for each ozone peak is proposed in connection with the meteorological context, using radiosounding data, total ozone content from TOMS/NIMBUS 7 and diagnoses issued from analyses by the European Centre for Medium-Range Weather Forecasts, Reading, England. The stratospheric origin of the 7.5-km ozone peak is inferred from negative correlations between ozone and its precursors and from diagnoses based on potential vorticity and ageostrophic circulations depicting the structure of the tropopause fold embedded in the subtropical jet front system. Using an appropriate method to isolate cross-and along-front ageostrophic circulations, we show that much of the observed structure of the tropopause fold can be ascribed to transverse and vertical circulations associated with the irrotational part of the flow. Though the downward extent of the subtropical tropopause fold (400 hPa) is restricted in comparison with typical extratropical tropopause ones (700 hPa), the present results suggest that subtropical tropopause folds may significantly contribute to the global stratosphere-troposphere ozone exchange. The origin of the 3.0-km ozone peak trapped just below the trade wind inversion cannot be ascribed precisely. Analogies with other measurements of dust and aerosols transported over the Atlantic or Pacific in the summer season are discussed. Various possibilities are examined:(1) an earlier stratospheric intrusion event, (2) long-range transport by the trade winds of biomass burning species emitted over West Africa, and (3) fast photochemical ozone formation occurring just below the trade wind inversion within already polluted air parcels originating from remote regions (United States and Gulf of Mexico) after eastward and southward transport around the western Atlantic anticyclone.

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“…Keyser et al [] have addressed the problem of partitioning three‐dimensional circulations into orthogonal two‐dimensional circulations. Their formalism is termed the “ ψ vector” method and has been applied to good effect in diagnosing the vertical circulations in midlatitude baroclinic systems [ Keyser et al , , ; Reeder et al , ]. Loughe et al [] have generalized the ψ vector method to limited domains and conformal map projections.…”

Section: Introductionmentioning

confidence: 99%

Local partitioning of the overturning circulation in the tropics and the connection to the Hadley and Walker circulations

et al. 2014

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Conceptually, it is useful to partition the three-dimensional tropical circulation into meridional and zonal components, namely, the Hadley and Walker circulations. The averaging involved in their definitions can introduce ambiguities. These problems can be circumvented by first partitioning the total vertical mass flux into components associated with overturning in the meridional and zonal directions, respectively, called here the local Hadley and local Walker circulations. Defining the local Hadley and local Walker circulations this way ensures the pair of two-dimensional overturning circulations can be added to give the original three-dimensional circulation, even when the averages are taken over limited domains. The method is applied to the vertical motion from the ERA-Interim reanalysis for the period 1979 to 2009. One important result is that the local Hadley circulation responds much more strongly to ENSO than the local Walker circulation, even though the local Walker circulation in the central Pacific weakens during El Niño years and strengthens and widens during La Niña years.

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A Technique for Representing Three-Dimensional Vertical Circulations in Baroclinic Disturbances

Cited by 50 publications

References 0 publications

Regional Widening of Tropical Overturning: Forced Change, Natural Variability, and Recent Trends

Regional Widening of Tropical Overturning: Forced Change, Natural Variability, and Recent Trends

Ozone peaks associated with a subtropical tropopause fold and with the trade wind inversion: A case study from the airborne campaign TROPOZ II over the Caribbean in winter

Local partitioning of the overturning circulation in the tropics and the connection to the Hadley and Walker circulations

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