Effective Isentropic Diffusivity of Tropospheric Transport

Chen, Gang; Plumb, R. Alan

doi:10.1175/jas-d-13-0333.1

Cited by 26 publications

(26 citation statements)

References 49 publications

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“…As such, the contribution of mean mass transport versus eddy mixing to tracer transport can be illuminated by modifying the parameters α mean and α eddy , respectively. As shown in Chen and Plumb [], in the limit of α mean =1 and α eddy =0, the tracer is advected only by the residual circulation, and the tracer is expected to be homogenized along the streamline of the zonal mean residual circulation. Conversely, in the limit of α m e a n =0 and α eddy =1, the tracer is advected by eddy stirring but with no diabatic mass transport, and the tracer is expected to be homogenized along isentropic surfaces.…”

Section: Idealized Model and Transport Diagnosticsmentioning

confidence: 99%

“…The effect of mean mass transport versus eddy mixing is diagnosed using the method described in Chen and Plumb []. For a tracer of mixing ratio χ , the mean mass transport and eddy mixing may be separated as

\frac{∂χ}{∂t} = - \frac{1}{ρ} \nabla \cdot (ρ boldu χ) = - \frac{1}{ρ} \nabla \cdot ((), ρ α_{mean} {boldu}_{res} χ) - \frac{1}{ρ} \nabla \cdot ([], ρ α_{eddy} (boldu - {boldu}_{res}) χ)

where ρ is density, ∇ is a 3‐D gradient operator, and u = ( u , v , w ) is the 3‐D velocity.…”

Section: Idealized Model and Transport Diagnosticsmentioning

confidence: 99%

“…Tracer transport in the global atmosphere can be thought of as the consequence of the diabatic overturning circulation and isentropic mixing [e.g., Plumb and Mahlman , ; Bowman and Carrie , ; Bowman and Erukhimova , ; Chen and Plumb , ]. In the tropics, the probability distribution functions of column water vapor and trace gases of different chemical sources/sinks exhibit similar exponential tails, providing observational evidence of tropical convection's influence on tracer distributions [ Neelin et al , ; Lintner et al , ].…”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, the Asian monsoon anticyclone is associated with horizontal eddy shedding and irreversible mixing of trace gases along its southward edge [Popovic and Plumb, 2001], and upper tropospheric Rossby wave breaking is very efficient at mixing air masses across the equator [Waugh et al, 1994]. Since tropospheric transport displays transport barriers in the subtropics [Haynes and Shuckburgh, 2000;Allen and Nakamura, 2001;Chen and Plumb, 2014], interhemispheric transport is also quantified by means of a three-box model, in which the tropical box is sandwiched between two extratropical boxes [Bowman and Carrie, 2002;Bowman and Erukhimova, 2004].…”

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confidence: 99%

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The role of monsoon‐like zonally asymmetric heating in interhemispheric transport

2017

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While the importance of the seasonal migration of the zonally averaged Hadley circulation on interhemispheric transport of trace gases has been recognized, few studies have examined the role of the zonally asymmetric monsoonal circulation. This study investigates the role of monsoon‐like zonally asymmetric heating on interhemispheric transport using a dry atmospheric model that is forced by idealized Newtonian relaxation to a prescribed radiative equilibrium temperature. When only the seasonal cycle of zonally symmetric heating is considered, the mean age of air in the Southern Hemisphere since last contact with the Northern Hemisphere midlatitude boundary layer is much larger than the observations. The introduction of monsoon‐like zonally asymmetric heating not only reduces the mean age of tropospheric air to more realistic values but also produces an upper tropospheric cross‐equatorial transport pathway in boreal summer that resembles the transport pathway simulated in the NASA Global Modeling Initiative Chemistry Transport Model driven with Modern‐Era Retrospective Analysis for Research and Applications meteorological fields. These results highlight that the monsoon‐induced eddy circulation plays an important role in the interhemispheric transport of long‐lived chemical constituents.

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Section: Idealized Model and Transport Diagnosticsmentioning

confidence: 99%

\frac{∂χ}{∂t} = - \frac{1}{ρ} \nabla \cdot (ρ boldu χ) = - \frac{1}{ρ} \nabla \cdot ((), ρ α_{mean} {boldu}_{res} χ) - \frac{1}{ρ} \nabla \cdot ([], ρ α_{eddy} (boldu - {boldu}_{res}) χ)

where ρ is density, ∇ is a 3‐D gradient operator, and u = ( u , v , w ) is the 3‐D velocity.…”

Section: Idealized Model and Transport Diagnosticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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The role of monsoon‐like zonally asymmetric heating in interhemispheric transport

2017

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“…Applying the eddy operator

scriptA (X)

to equation , the FAWA is mathematically related to the lateral eddy fluxes across the latitude φ e through the divergence theorem (see Figure b and the proof for

\overset{scriptA (boldv \cdot \nabla q)}{false} = \overset{v^{'} q^{'}}{false}

in supporting information Text S2) [ Nakamura and Zhu , ; Chen and Plumb , ; Lu et al , ]

\frac{\partial \overset{A}{false}}{∂t} + \overset{v^{'} q^{'}}{false} = \overset{scriptA (\overset{q}{true})}{false} .

…”

Section: Theory Of Wave Activitymentioning

confidence: 99%

Local finite‐amplitude wave activity as an objective diagnostic of midlatitude extreme weather

Chen

Burrows

et al. 2015

Geophysical Research Letters

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Midlatitude extreme weather events are responsible for a large part of climate‐related damage, yet our understanding of these extreme events is limited, partly due to the lack of a theoretical basis for midlatitude extreme weather. In this letter, the local finite‐amplitude wave activity (LWA) of Huang and Nakamura (2015) is introduced as a diagnostic of the 500 hPa geopotential height for characterizing midlatitude weather events. It is found that the LWA climatology and its variability associated with the Arctic Oscillation agree broadly with the previously reported blocking frequency in the literature. There is a strong seasonal and spatial dependence in the trends of LWA in recent decades. While there is no observational evidence for a hemispheric‐scale increase in wave amplitude, robust trends in wave activity can be identified at the regional scales, with important implications for regional climate change.

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Constraining the Varied Response of Northern Hemisphere Winter Circulation Waviness to Climate Change

Nie

Chen

et al. 2023

Geophysical Research Letters

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The extratropical westerly circulation exhibits frequent latitudinal displacements on the synoptic timescale, manifesting as Rossby waves with alternating ridges and troughs. Under certain circumstances, a large meandering of the westerly jet induces stagnant weather patterns such as atmospheric blocking, resulting in regional temperature extremes or severe air pollution (Buehler et al., 2011;Pfahl & Wernli, 2012;W. Sun et al., 2019). It was hypothesized that Arctic amplification, the enhanced surface warming in the Arctic region relative to lower latitudes under increasing greenhouse gases, slows down the midlatitude westerly flow, which, in turn, causes an increase in circulation waviness and associated weather extremes (Francis & Vavrus, 2012). While there is observational evidence for the coincidence between Arctic amplification and increasing waviness (Francis et al., 2017;Vavrus, 2018), the observed multidecadal trends in waviness are rather weak and largely obscured by internal variability of the climate system (Blackport & Screen, 2020). Using large ensembles from multiple climate models, Smith et al. ( 2022) conclude a robust, weak winter circulation response to future Arctic sea ice loss, but models also exhibit substantial internal variability, for which even a 100-member ensemble may be insufficient to detect robust midlatitude circulation response to Arctic warming (Peings et al., 2021;L. Sun et al., 2022). Moreover, the weakened midlatitude jet stream due to Arctic warming can be offset by tropical upper-tropospheric warming that strengthens the jet, producing a net effect of small decreases in waviness at the end of the 21st century, albeit with considerable model spread (

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Effective Isentropic Diffusivity of Tropospheric Transport

Cited by 26 publications

References 49 publications

The role of monsoon‐like zonally asymmetric heating in interhemispheric transport

The role of monsoon‐like zonally asymmetric heating in interhemispheric transport

Local finite‐amplitude wave activity as an objective diagnostic of midlatitude extreme weather

Constraining the Varied Response of Northern Hemisphere Winter Circulation Waviness to Climate Change

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