Identifying robust transport features of the upper tropical troposphere

Bergman, John W.; Pfister, Leonhard; Yang, Qiong

doi:10.1002/2015jd023523

Cited by 10 publications

(26 citation statements)

References 68 publications

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“…Bergman et al . [] examined how trajectories differ from these same models in order to isolate robust features of transport to the tropical tropopause. They found that intermodel variations of parcel densities often (though not typically) exceed 50%.…”

Section: Resultsmentioning

confidence: 99%

“…These calculations were used by Bergman et al . [] to identify robust features of source distributions for air entering the tropical stratosphere. The comparison between dispersion from the multimodel approach and the other ensemble approaches reveals the impact of wind data uncertainty on trajectory dispersion and, thus, complements the analysis of Bergman et al .…”

Section: Experimental Design Models and Input Datamentioning

confidence: 99%

“…[] by examining how quickly the potential resolution of source features decays with trajectory length. The MULTIMODEL ensemble is comprised of four kinematic and four diabatic trajectory calculations (details in section 2.2) [see also Bergman et al ., , Table 1].…”

Section: Experimental Design Models and Input Datamentioning

confidence: 99%

“…This paper is the second of two that address the issue of scale limitations for trajectory analyses. Part I [ Bergman et al ., ] analyzed “multimodel ensembles” of trajectories comprised of calculations using different forcing data and trajectory “formulations” (i.e., diabatic trajectories that are formulated in potential temperature coordinates and kinematic trajectories that are formulated in pressure coordinates) to identify features of parcel source distributions that are robust to analysis uncertainty. That study demonstrated that large‐scale features (horizontal scales ~30° and larger) are robust provided sufficient time averaging (typically on monthly scales and longer) is applied.…”

Section: Introductionmentioning

confidence: 99%

“…That study demonstrated that large-scale features (horizontal scales~30°and larger) are robust provided sufficient time averaging (typically on monthly scales and longer) is applied. To complement the work of Bergman et al [2015], this study examines dispersion as it applies to the spread of trajectories that are initialized from within the same "small" region of space (one-grid space of the analysis data; see Figure 1). We compare dispersion from three different ensemble approaches using backward trajectories that allow us to obtain insight into the individual roles of the resolved and unresolved wind fluctuations as well as the impact of uncertainties in the analyzed wind fields.…”

Section: Introductionmentioning

confidence: 99%

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Air parcel trajectory dispersion near the tropical tropopause

et al. 2016

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Dispersion of backward air parcel trajectories that are initially tightly grouped near the tropical tropopause is examined using three ensemble approaches: “RANWIND,” in which different ensemble members use identical resolved wind fluctuations but different realizations of stochastic, multifractal simulations of unresolved winds; “PERTLOC,” in which members use identical resolved wind fields but initial locations are perturbed 2° in latitude and longitude; and a multimodel ensemble (“MULTIMODEL”) that uses identical initial conditions but different resolved wind fields and/or trajectory formulations. Comparisons among the approaches distinguish, to some degree, physical dispersion from that due to data uncertainty and the impacts of unresolved wind fluctuations from those of resolved variability. Dispersion rates are robust properties of trajectories near the tropical tropopause. Horizontal dispersion rates are typically ~3°/d, which is large enough to spread parcels throughout the tropics within typical tropical tropopause layer transport times (30–60 days) and underscores the importance of averaging large collections of trajectories to obtain reliable parcel source and pathway distributions. Vertical dispersion rates away from convection are ~2–3 hPa/d. Dispersion is primarily carried out by the resolved flow, and the RANWIND approach provides a plausible representation of actual trajectory dispersion rates, while PERTLOC provides a reasonable and inexpensive alternative to RANWIND. In contrast, dispersion from the MULTIMODEL calculations is important because it reflects systematic differences in resolved wind fields from different reanalysis data sets.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Design Models and Input Datamentioning

confidence: 99%

Section: Experimental Design Models and Input Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Air parcel trajectory dispersion near the tropical tropopause

et al. 2016

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The viability of trajectory analysis for diagnosing dynamical and chemical influences on ozone concentrations in the UTLS

et al. 2017

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To evaluate the utility of trajectory analysis in the tropical upper troposphere/lower stratosphere, Lagrangian predictions of ozone mixing ratio are compared to observations from the Airborne Tropical TRopopause EXperiment. Model predictions are based on backward trajectories that are initiated along flight tracks. Ozone mixing ratios from analysis data interpolated onto “source locations” (at trajectory termini) provide initial conditions for chemical production models that are integrated forward in time along parcel trajectories. Model sensitivities are derived from ensembles of predictions using two sets of dynamical forcing fields, four sets of source ozone mixing ratios, three trajectory formulations (adiabatic, diabatic, and kinematic), and two chemical production models. Direct comparisons of analysis ozone mixing ratios to observations have large random errors that are reduced by averaging over 75 min (~800 km) long flight tracks. These averaged values have systematic errors that motivate a similarly systematic adjustment to source ozone mixing ratios. Sensitivity experiments reveal a prediction error minimum in parameter space and, thus, a consistent diagnostic picture: The best predictions utilize the source ozone adjustment and a chemical production model derived from Whole Atmosphere Community Climate Model (a chemistry‐climate model) chemistry. There seems to be slight advantages to using ERA‐Interim winds compared to Modern‐Era Retrospective Analysis for Research and Applications and to using kinematic trajectories compared to diabatic; however, both diabatic and kinematic formulations are clearly preferable to adiabatic trajectories. For these predictions, correlations with observations typically decrease as model error is reduced and, thus, fail as a model comparison metric.

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Impact of different Asian source regions on the composition of the Asian monsoon anticyclone and of the extratropical lowermost stratosphere

et al. 2015

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Abstract. The impact of different boundary layer source regions in Asia on the chemical composition of the Asian monsoon anticyclone, considering its intraseasonal variability in 2012, is analysed by simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS) using artificial emission tracers. The horizontal distribution of simulated CO, O3, and artificial emission tracers for India/China are in good agreement with patterns found in satellite measurements of O3 and CO by the Aura Microwave Limb Sounder (MLS). Using in addition, correlations of artificial emission tracers with potential vorticity demonstrates that the emission tracer for India/China is a very good proxy for spatial distribution of trace gases within the Asian monsoon anticyclone. The Asian monsoon anticyclone constitutes a horizontal transport barrier for emission tracers and is highly variable in location and shape. From the end of June to early August, a northward movement of the anticyclone and, during September, a strong broadening of the spatial distribution of the emission tracer for India/China towards the tropics are found. In addition to the change of the location of the anticyclone, the contribution of different boundary source regions to the composition of the Asian monsoon anticyclone in the upper troposphere strongly depends on its intraseasonal variability and is therefore more complex than hitherto believed. The largest contributions to the composition of the air mass in the anticyclone are found from northern India and Southeast Asia at a potential temperature of 380 K. In the early (mid-June to mid-July) and late (September) period of the 2012 monsoon season, contributions of emissions from Southeast Asia are highest; in the intervening period (early August), emissions from northern India have the largest impact. Our findings show that the temporal variation of the contribution of different convective regions is imprinted in the chemical composition of the Asian monsoon anticyclone. Air masses originating in Southeast Asia are found both within and outside of the Asian monsoon anticyclone because these air masses experience, in addition to transport within the anticyclone, upward transport at the southeastern flank of the anticyclone and in the tropics. Subsequently, isentropic poleward transport of these air masses occurs at around 380 K with the result that the extratropical lowermost stratosphere in the Northern Hemisphere is flooded by the end of September with air masses originating in Southeast Asia. Even after the breakup of the anticyclonic circulation (around the end of September), significant contributions of air masses originating in India/China are still found in the upper troposphere over Asia. Our results demonstrate that emissions from India, China, and Southeast Asia have a significant impact on the chemical composition of the lowermost stratosphere of the Northern Hemisphere, in particular at the end of the monsoon season in September/October 2012.

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Identifying robust transport features of the upper tropical troposphere

Cited by 10 publications

References 68 publications

Air parcel trajectory dispersion near the tropical tropopause

Air parcel trajectory dispersion near the tropical tropopause

The viability of trajectory analysis for diagnosing dynamical and chemical influences on ozone concentrations in the UTLS

Impact of different Asian source regions on the composition of the Asian monsoon anticyclone and of the extratropical lowermost stratosphere

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