Local Mixing Events in the Upper Troposphere and Lower Stratosphere. Part I: Detection with the Lyapunov Diffusivity

Abstract A new diagnostic (the “Lyapunov diffusivity”) is presented that has the ability to quantify isentropic mixing in diffusion units and detects local mixing events by describing latitude–longitude variability. It is a hybrid diagnostic, combining the tracer-based effective diffusivity with the particle-based Lyapunov exponent calculation. Isentropic mixing on the 350-K surface shows that there is significant longitudinal variation to the strength of mixing at the northern subtropical jet, with a strong mixing barrier over Asia and the western Pacific, a weaker mixing barrier over the western Atlantic, and active mixing regions at the jet exits over the eastern Pacific and Atlantic.

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Local Mixing Events in the Upper Troposphere and Lower Stratosphere. Part II: Seasonal and Interannual Variability

Journal of the Atmospheric Sciences ◽

10.1175/2009jas2983.1 ◽

2009 ◽

Vol 66 (12) ◽

pp. 3695-3706 ◽

Cited By ~ 20

Author(s):

Emily Shuckburgh ◽

Francesco d’Ovidio ◽

Bernard Legras

Keyword(s):

Lower Stratosphere ◽

Southern Oscillation ◽

Positive Phase ◽

Strong Mixing ◽

Atmospheric Variability ◽

Upper Troposphere ◽

Rossby Wave Breaking ◽

The North ◽

Subtropical Jet ◽

The Pacific

Abstract The Lyapunov diffusivity is used to investigate local isentropic mixing events in the upper troposphere–lower stratosphere (UTLS) region. The diagnostic highlights the seasonal cycle of the longitudinally varying mixing properties, in particular those associated with the monsoon circulations and the westerly ducts in the subtropics. The results are broadly consistent with studies of Rossby wave–breaking frequencies. The mixing structure is shown to be modulated by modes of atmospheric variability. El Niño–Southern Oscillation (ENSO) is found to strongly influence the mixing structure throughout the tropics and subtropics. The subtropical jet is associated with longitudinal bands of mixing minima (isentropic mixing barriers) separated by synoptic-scale regions of strong mixing activity. The greatest ENSO modulation in December–February is confined to the Pacific sector, where the barriers associated with the subtropical jets extend farther into the eastern Pacific, and in the western Pacific a barrier is found at the equator during the positive phase. During June–August, the influence is seen to extend beyond the Pacific region, with the barrier at the subtropical jet in the Southern Hemisphere increasing in strength at all longitudes and with an increase in strength (and isolation of) monsoon-related mixing over Asia and North America. The local influence of the North Atlantic Oscillation in wintertime is investigated. During the positive phase, a double-barrier structure is associated with the subtropical jet, the northern branch crosses the Atlantic toward Scandinavia, and the southern branch tends toward North Africa. The Antarctic Oscillation is shown to influence whether the subvortex region is isolated from midlatitudes.

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An Evaluation of Some Condensation Trail Observations

Bulletin of the American Meteorological Society ◽

10.1175/1520-0477-36.2.73 ◽

1955 ◽

Vol 36 (2) ◽

pp. 73-79

Author(s):

Hal H. Dunning ◽

N. E. La Seur

Keyword(s):

Lower Stratosphere ◽

Theoretical Work ◽

Polar Front ◽

Jet Streams ◽

Upper Troposphere ◽

Subtropical Jet ◽

Synoptic Features ◽

Trail Formation ◽

Polar Front Jet

Observations made on ten routine B-47 training missions are used to evaluate present theoretical work on formation of exhaust condensation trails, and these observations are then correlated with the structure of the upper troposphere and lower stratosphere, to determine synoptic features typically associated with favorable and unfavorable conditions for trail formation For the altitudes considered broad areas of trail formation were found to occur only between the polar front and the sub-tropical jet streams. Broad areas unfavorable to trail formation were found to be located on the cyclonic shear side of the polar front jet and on the anticyclonic shear side of the subtropical jet. Agreement between these observations and theory is good.

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Global large-scale stratosphere–troposphere exchange in modern reanalyses

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-5537-2017 ◽

2017 ◽

Vol 17 (9) ◽

pp. 5537-5559 ◽

Cited By ~ 18

Author(s):

Alexander C. Boothe ◽

Cameron R. Homeyer

Keyword(s):

Large Scale ◽

Lower Stratosphere ◽

Radiative Properties ◽

Lapse Rate ◽

Polar Regions ◽

Transport Mechanisms ◽

Upper Troposphere ◽

Subtropical Jet ◽

The Tropics

Abstract. Stratosphere–troposphere exchange (STE) has important impacts on the chemical and radiative properties of the upper troposphere and lower stratosphere. This study presents a 15-year climatology of global large-scale STE from four modern reanalyses: ERA-Interim, JRA-55, MERRA-2, and MERRA. STE is separated into three regions (tropics, subtropics, and extratropics) and two transport directions (stratosphere-to-troposphere transport or STT and troposphere-to-stratosphere transport or TST) in an attempt to identify the significance of known transport mechanisms. The extratropics and tropics are separated by the tropopause break. Any STE occurring between the tropics and the extratropics through the tropopause break is considered subtropical exchange (i.e., in the vicinity of the subtropical jet). In addition, this study employs a method to identify STE as that which crosses the lapse-rate tropopause (LRT), while most previous studies have used a potential vorticity (PV) isosurface as the troposphere–stratosphere boundary. PV-based and LRT-based STE climatologies are compared using the ERA-Interim reanalysis output. The comparison reveals quantitative and qualitative differences, particularly for TST in the polar regions. Based upon spatiotemporal integrations, we find STE to be STT dominant in ERA-Interim and JRA-55 and TST dominant in MERRA and MERRA-2. The sources of the differences are mainly attributed to inconsistencies in the representation of STE in the subtropics and extratropics. Time series during the 15-year analysis period show long-term changes that are argued to correspond with changes in the Brewer–Dobson circulation.

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Unsteady vortex behavior in the Asian monsoon anticyclone

10.5194/egusphere-egu21-10490 ◽

2021 ◽

Author(s):

Leong Wai Siu ◽

Kenneth Bowman

Keyword(s):

Vortex Shedding ◽

Diabatic Heating ◽

Asian Monsoon ◽

Lower Stratosphere ◽

Synoptic Scale ◽

Single Vortex ◽

Summer Circulation ◽

Upper Troposphere ◽

Subtropical Jet ◽

Heat Released

<p>The Asian monsoon anticyclone (AMA), which is primarily driven by the latent heat released by monsoon precipitation, is one of the dominant features of the Northern Hemisphere summer circulation in the upper troposphere and lower stratosphere. Due to variations in the diabatic heating, interactions with Rossby waves propagating along the subtropical jet, and internal dynamics within the anticyclone, the circulation of the AMA is unsteady. Here we use the ERA-Interim dataset and trajectories computed with ERA-Interim winds to show that the AMA contains two or three distinct synoptic-scale subvortices 69% of the time, while a single circulation center is present only 23% of the time. More than three simultaneous subvortices are uncommon. Observed behaviors of the subvortices include 1) splitting of a single vortex into two vortices; 2) merger of two vortices into a single vortex; 3) vortex shedding in the eastward direction; 4) vortex shedding in the westward direction; and 5) formation, movement, and dissipation of a vortex. The evolution of the subvortices is closely tied to stirring and transport.</p>

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Unsteady Vortex Behavior in the Asian Monsoon Anticyclone

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0349.1 ◽

2020 ◽

Vol 77 (12) ◽

pp. 4067-4088

Author(s):

Leong Wai Siu ◽

Kenneth P. Bowman

Keyword(s):

Vortex Shedding ◽

Diabatic Heating ◽

Asian Monsoon ◽

Lower Stratosphere ◽

Synoptic Scale ◽

Single Vortex ◽

Summer Circulation ◽

Upper Troposphere ◽

Subtropical Jet ◽

Heat Released

AbstractThe Asian monsoon anticyclone (AMA), which is primarily driven by the latent heat released by monsoon precipitation, is one of the dominant features of the Northern Hemisphere summer circulation in the upper troposphere and lower stratosphere. Due to variations in the diabatic heating, interactions with Rossby waves propagating along the subtropical jet, and internal dynamics within the anticyclone, the circulation of the AMA is unsteady. Here we use the ERA-Interim dataset and trajectories computed with ERA-Interim winds to show that the AMA contains two or three distinct synoptic-scale subvortices 69% of the time, while a single circulation center is present only 23% of the time. More than three simultaneous subvortices are uncommon. Observed behaviors of the subvortices include 1) splitting of a single vortex into two vortices; 2) merger of two vortices into a single vortex; 3) vortex shedding in the eastward direction; 4) vortex shedding in the westward direction; and 5) formation, movement, and dissipation of a vortex. The evolution of the subvortices is closely tied to stirring and transport.

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Interannual variability in effective diffusivity in the upper troposphere/lower stratosphere from reanalysis data

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.2779 ◽

2016 ◽

Vol 142 (697) ◽

pp. 1847-1861 ◽

Cited By ~ 13

Author(s):

Marta Abalos ◽

Bernard Legras ◽

Emily Shuckburgh

Keyword(s):

Interannual Variability ◽

Lower Stratosphere ◽

Effective Diffusivity ◽

Reanalysis Data ◽

Upper Troposphere

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Transport of trace gases via eddy shedding from the Asian summer monsoon anticyclone and associated impacts on ozone heating rates

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-11493-2018 ◽

2018 ◽

Vol 18 (15) ◽

pp. 11493-11506 ◽

Cited By ~ 9

Author(s):

Suvarna Fadnavis ◽

Chaitri Roy ◽

Rajib Chattopadhyay ◽

Christopher E. Sioris ◽

Alexandru Rap ◽

...

Keyword(s):

Lower Stratosphere ◽

Asian Summer Monsoon ◽

Trace Gases ◽

Western Pacific ◽

Heating Rates ◽

Upper Troposphere ◽

Western Africa ◽

Asian Summer ◽

The Western Pacific ◽

Eddy Shedding

Abstract. The highly vibrant Asian summer monsoon (ASM) anticyclone plays an important role in efficient transport of Asian tropospheric air masses to the extratropical upper troposphere and lower stratosphere (UTLS). In this paper, we demonstrate long-range transport of Asian trace gases via eddy-shedding events using MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) satellite observations, ERA-Interim reanalysis data and the ECHAM5–HAMMOZ global chemistry-climate model. Model simulations and observations consistently show that Asian boundary layer trace gases are lifted to UTLS altitudes in the monsoon anticyclone and are further transported horizontally eastward and westward by eddies detached from the anticyclone. We present an event of eddy shedding during 1–8 July 2003 and discuss a 1995–2016 climatology of eddy-shedding events. Our analysis indicates that eddies detached from the anticyclone contribute to the transport of Asian trace gases away from the Asian region to the western Pacific (20–30∘ N, 120–150∘ E) and western Africa (20–30∘ N, 0–30∘ E). Over the last two decades, the estimated frequency of occurrence of eddy-shedding events is ∼68 % towards western Africa and ∼25 % towards the western Pacific. Model sensitivity experiments considering a 10 % reduction in Asian emissions of non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOx) were performed with ECHAM5–HAMMOZ to understand the impact of Asian emissions on the UTLS. The model simulations show that transport of Asian emissions due to eddy shedding significantly affects the chemical composition of the upper troposphere (∼100–400 hPa) and lower stratosphere (∼100–80 hPa) over western Africa and the western Pacific. The 10 % reduction of NMVOCs and NOx Asian emissions leads to decreases in peroxyacetyl nitrate (PAN) (2 %–10 % near 200–80 hPa), ozone (1 %–4.5 % near ∼150 hPa) and ozone heating rates (0.001–0.004 K day−1 near 300–150 hPa) in the upper troposphere over western Africa and the western Pacific.

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Measurements of the upper troposphere and lower stratosphere during tropical cyclones using the GPS radio occultation technique

Advances in Space Research ◽

10.1016/j.asr.2010.05.031 ◽

2011 ◽

Vol 47 (2) ◽

pp. 348-355 ◽

Cited By ~ 7

Author(s):

Riccardo Biondi ◽

Torsten Neubert ◽

Stig Syndergaard ◽

Johannes Nielsen

Keyword(s):

Tropical Cyclones ◽

Radio Occultation ◽

Lower Stratosphere ◽

Upper Troposphere ◽

Gps Radio Occultation

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A Case Study of Mass Transport during the East-West Oscillation of the Asian Summer Monsoon Anticyclone

Advances in Meteorology ◽

10.1155/2017/5174025 ◽

2017 ◽

Vol 2017 ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Jiali Luo ◽

Jiayao Song ◽

Hongying Tian ◽

Lei Liu ◽

Xinlei Liang

Keyword(s):

Lower Stratosphere ◽

Asian Summer Monsoon ◽

Chemical Transport ◽

Upward Motion ◽

High Concentration ◽

Upper Troposphere ◽

Asian Summer ◽

Mode Tm ◽

East West

We use ERA-Interim reanalysis, MLS observations, and a trajectory model to examine the chemical transport and tracers distribution in the Upper Troposphere and Lower Stratosphere (UTLS) associated with an east-west oscillation case of the anticyclone in 2016. The results show that the spatial distribution of water vapor (H2O) was more consistent with the location of the anticyclone than carbon monoxide (CO) at 100 hPa, and an independent relative high concentration center was only found in H2O field. At 215 hPa, although the anticyclone center also migrated from the Tibetan Mode (TM) to the Iranian Mode (IM), the relative high concentration centers of both tracers were always colocated with regions where upward motion was strong in the UTLS. When the anticyclone migrated from the TM, air within the anticyclone over Tibetan Plateau may transport both westward and eastward but was always within the UTLS. The relative high concentration of tropospheric tracers within the anticyclone in the IM was from the east and transported by the westward propagation of the anticyclone rather than being lifted from surface directly. Air within the relative high geopotential height centers over Western Pacific was partly from the main anticyclone and partly from lower levels.

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