A global blended tropopause based on ERA data. Part I: Climatology

Wilcox, Laura; Hoskins, Brian J.; Shine, Keith P.

doi:10.1002/qj.951

Cited by 68 publications

(78 citation statements)

References 35 publications

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“…It should be noted that the dynamical tropopause is slightly elevated around the reference longitude of the anticyclonic PV anomaly, which is consistent with a theoretical study by Wirth (2000). UCs are observed around and even slightly above the elevated tropopause (i.e., in the stratosphere).…”

Section: Role Of Tropospheric Anticyclones In Simultaneous Appearancesupporting

confidence: 91%

“…They concluded that anticyclones near the tropopause have a primary role in the occurrence of Arctic PSCs. Fromm et al (2003), who used long-term satellite observations that included the Stratospheric Aerosol Measurement II, Stratospheric Aerosol and Gas Measurement II, and Polar Ozone and Aerosol Measurement II/III, also confirmed that Arctic PSCs are frequently associated with an elevated tropopause (∼ 10 km), which is attributable to anticyclones near the tropopause (Wirth, 2000). Anticyclonic potential vorticity (PV) anomalies near the tropopause are associated with low temperatures above the tropopause (e.g., Holton, 2004): a PV anomaly at one level yields nonzero geopotential anomalies at levels above and below this level.…”

Section: Kohma and K Sato: Polar Stratospheric Clouds And Upper-tmentioning

confidence: 81%

“…However, the definition of the thermal tropopause frequently gives inappropriate estimations for polar night region as the static stability is quite low in the lower stratosphere there. It is well known that discontinuity of tropopause heights and multivalued tropopause heights are seen (e.g., Wilcox et al, 2012). Thus, the definition of the tropopause that was proposed by Wilcox et al (2012) was used.…”

Section: Tropopause Height Definitionsmentioning

confidence: 99%

“…It is well known that discontinuity of tropopause heights and multivalued tropopause heights are seen (e.g., Wilcox et al, 2012). Thus, the definition of the tropopause that was proposed by Wilcox et al (2012) was used. This tropopause comprises both thermal and dynamical tropopause; it is defined as…”

Section: Tropopause Height Definitionsmentioning

confidence: 99%

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Simultaneous occurrence of polar stratospheric clouds and upper-tropospheric clouds caused by blocking anticyclones in the Southern Hemisphere

Kohma

Sato

2013

Atmos. Chem. Phys.

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Previous studies have reported that polar stratospheric clouds (PSCs) are frequently observed simultaneously with upper-tropospheric clouds (UCs) in the Southern Hemisphere. However, it has not yet been examined whether the UCs that simultaneously occur with PSCs are actually located below the height of the tropopause, which is modified by tropospheric disturbances. Furthermore, the mechanism of this simultaneous occurrence has not yet been clarified. This study statistically examines the simultaneous appearance of PSCs and UCs using the Cloud-Aerosol Lidar and Pathfinder Satellite Observation (CALIPSO) for the five austral winters of 2007–2011. From correlation analyses and statistical dependence tests, it is shown that the simultaneous occurrence frequencies of clouds with an altitude range of 15–25 km and 9–11 km are significant. The analyses based on tropopause-relative altitude suggest that the occurrence frequency of clouds at altitudes higher than 6 km above the local tropopause (i.e., PSCs) is significantly correlated with that of clouds around and slightly above the tropopause. These results indicate that the UCs observed simultaneously with PSCs reported in previous case studies are likely located around and slightly above the tropopause rather than in the troposphere. It is also shown that the simultaneous occurrence of PSCs and UCs is frequently associated with blocking highs that have large horizontal scales (several thousand kilometers) and tall structure (up to a height of ~15 km). The longitudinal variation of blocking high frequency accords well with that of the simultaneous occurrence frequency of PSCs and UCs. This fact suggests that the blocking highs provide a preferable condition for such simultaneous occurrences. Moreover, the composition of PSCs is investigated as a function of relative longitude of the anticyclones including blocking highs. It was discovered that relatively high proportions of STS (super-cooled ternary solutions), Ice, and Mix2 (mixture of nitric acid trihydrate and STS) types are distributed towards the windward, near, and leeward side of anticyclones in westerly background flows, respectively

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Section: Role Of Tropospheric Anticyclones In Simultaneous Appearancesupporting

confidence: 91%

Section: Kohma and K Sato: Polar Stratospheric Clouds And Upper-tmentioning

confidence: 81%

Section: Tropopause Height Definitionsmentioning

confidence: 99%

Section: Tropopause Height Definitionsmentioning

confidence: 99%

See 2 more Smart Citations

Simultaneous occurrence of polar stratospheric clouds and upper-tropospheric clouds caused by blocking anticyclones in the Southern Hemisphere

Kohma

Sato

2013

Atmos. Chem. Phys.

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“…Changes in tropopause height and morphology associated with climate change (e.g. Wilcox et al, 2012) suggest that there may be very important chemistry-climate feedbacks related to ozone, such as those related to changes in the Brewer-Dobson circulation (e.g. Hegglin and Shepherd, 2009;Nowack et al, 2015).…”

Section: Impact Of Ozone On Climatementioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

et al. 2015

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Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

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On the linkage between the Asian summer monsoon and tropopause fold activity over the eastern Mediterranean and the Middle East

Tyrlis

Škerlak

Sprenger

et al. 2014

J. Geophys. Res. Atmos.

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A climatology of tropopause folds occurring over the Eastern Mediterranean and the Middle East (EMME) has been established using the ERA-Interim reanalyses for the years 1979-2012. The methodology employs an algorithm that detects folds at grid points where the vertical profile features multiple crossings of the dynamical tropopause and allows their classification according to their vertical extent. Our results confirm the findings of an earlier 1 year climatology that recognized a global "hot spot" of summertime fold activity between the eastern Mediterranean and central Asia, in the vicinity of the subtropical jet. Two distinct maxima of activity are identified over Turkey and Iran-Afghanistan where fold frequency exceeds 25%. Occasionally, medium and deep folds form over the two regions at surprisingly low latitudes. This summertime peak in fold activity diverges from the zonal mean seasonal cycle over the subtropics and is driven by the South Asian Monsoon. Starting in late spring, the EMME is gradually brought under the influence of the zonally asymmetric background state induced by the monsoon. As areas of sharply sloping isentropes develop especially over the eastern Mediterranean and Iran-Afghanistan, subsidence and fold formation are favored. Further investigation of the reanalysis data provided empirical evidence that the monsoon also drives the interannual variability of EMME fold activity. An upward trend in fold activity is identified, especially in May, attributed to the recent advanced monsoon onset and the deepening convective activity throughout summer, which promotes upper-level baroclinicity over the EMME and favors folding.

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A global blended tropopause based on ERA data. Part I: Climatology

Cited by 68 publications

References 35 publications

Simultaneous occurrence of polar stratospheric clouds and upper-tropospheric clouds caused by blocking anticyclones in the Southern Hemisphere

Simultaneous occurrence of polar stratospheric clouds and upper-tropospheric clouds caused by blocking anticyclones in the Southern Hemisphere

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

On the linkage between the Asian summer monsoon and tropopause fold activity over the eastern Mediterranean and the Middle East

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