Increase of upper troposphere/lower stratosphere wave baroclinicity during the second half of the 20th century

Castanheira, J. M.; Añel, Juan Antonio; Marques, Carlos; Antuña, Juan Carlos; Liberato, Margarida L. R.; Torre, Laura de la; Gimeno, Luis

doi:10.5194/acp-9-9143-2009

Cited by 27 publications

(14 citation statements)

References 16 publications

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“…A possible explanation is that folds in these regions develop in conjunction with PV streamers characteristic of Rossby wave breaking. This hypothesis is supported by Wernli and Sprenger [2007], who found maxima of PV streamer frequencies at 350 K over the eastern North Pacific and the North Atlantic in DJF (most shallow folds are centered around this isentrope; see section 4.2 and Figure 6), and Castanheira et al [2009], who reported on a link between baroclinic wave activity and double tropopause frequency. The high fold frequency and the distinct double-peak structure over the Mediterranean and Middle East in JJA are results of a complex interplay between the STJ and the Asian monsoon anticyclone [Traub and Lelieveld, 2003].…”

Section: Geographical Distributionmentioning

confidence: 99%

Tropopause folds in ERA‐Interim: Global climatology and relation to extreme weather events

et al. 2015

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Tropopause folds are intimately linked to upper level frontogenesis and jet stream dynamics.They play an important role for stratosphere-troposphere exchange, the dynamical coupling of upper and lower tropospheric levels, and for generating severe weather events. This study presents a global climatology of tropopause folds using ERA-Interim reanalysis data from 1979 to 2012 and a refined version of a previously developed 3-D labeling and fold identification algorithm. This algorithm objectively separates stratospheric and tropospheric air in complex situations, e.g., in regions with strong low-level inversions, and in extratropical cyclones where diabatically generated potential vorticity anomalies typically occur. Three classes of tropopause folds are defined (shallow, medium, and deep), and their geographical distribution, vertical extent, and seasonal cycle are investigated. Most shallow folds occur along the subtropical jet stream, in agreement with previous studies. Hot spots of medium and deep tropopause folds are found west of Australia and along the coast of Antarctica in the Southern Hemisphere and around the east coast of North America in the Northern Hemisphere. Seasonal cycles show maxima in winter for all fold classes. Medium and deep folds are frequently associated with surface wind gust and precipitation extremes, as quantified for folds over the southern Indian Ocean. Wind gust extremes occur mainly in an elongated band upstream and equatorward of folds, whereas precipitation extremes occur mainly east and poleward of folds. Overall, in the considered region, about 20% of medium folds and 33% of deep folds are associated with surface wind or precipitation extremes in the vicinity of the fold.

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Section: Geographical Distributionmentioning

confidence: 99%

Tropopause folds in ERA‐Interim: Global climatology and relation to extreme weather events

et al. 2015

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“…[3] Randel et al [2007] and Pan et al [2009] suggested that the mechanisms responsible for the formation of double tropopause structures may include contributions from a thermally direct secondary circulation around the subtropical jet, which is associated with developing baroclinic waves and is accompanied by an excursion of the tropical tropopause over the extratropical one. Castanheira et al [2009] suggested that DT events must be associated with baroclinic waves in the subtropical upper troposphere/lower stratosphere (UTLS). Such an association would explain the significant positive trends in the frequency of DT events identified in radiosonde data, concurrent with significant positive trends in the energy of baroclinic waves as seen in reanalysis data.…”

Section: Introductionmentioning

confidence: 99%

Association of double tropopause events with baroclinic waves

Castanheira

Gimeno

2011

J. Geophys. Res.

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[1] We herein propose a method for identifying breaks in the subtropical tropopause as found in the ERA Interim reanalysis data. The method uses the identification of double tropopauses and allows the quantification of the extension of the overlap between the tropical and extratropical tropopauses. The correlations between the meridional extension of the superposition of tropopauses and the fields of geopotential, potential vorticity, or potential temperature, reveal baroclinic wave patterns. Similar wave patterns were also identified in the potential temperature fields derived from GPS radio occultation COSMIC data. The zonal propagation velocity of the anomalies in the meridional extension of the overlap was estimated using Hovmöller diagrams. The estimated zonal velocities suggest that the variability in the superposition of the tropopauses is associated with baroclinic Rossby wave patterns in the subtropical upper troposphere and lower stratosphere.Citation: Castanheira, J. M., and L. Gimeno (2011), Association of double tropopause events with baroclinic waves,

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“…Sausen and Santer [2003], Santer et al [2003a], and Añel et al [2006] have suggested that changes in the altitude of the tropopause caused by cooling in the stratosphere and warming in the troposphere [Santer et al, 2003b] may be a sensitive indicator of anthropogenic climate change. Recently, Castanheira et al [2009] presented observational evidence of increases in wave baroclinicity in the upper troposphere and lower stratosphere (UTLS) at midlatitudes due to increase in greenhouse gas radiative forcing. They also interpreted significant positive trends in the frequency of double tropopause events in the radiosonde data as a manifestation of an increase in UTLS baroclinicity.…”

Section: Introductionmentioning

confidence: 99%

Multiple tropopauses in the tropics: A cold point approach

Mehta¹,

Ratnam²,

Murthy³

2011

J. Geophys. Res.

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[1] New criteria for the identification of multiple tropopauses (MTs) in the tropics are proposed using COSMIC GPS RO data during 2006-2008 in the tropical belt (±30°latitude) and radiosonde data from 5 tropical stations during 1999 to 2008 in the ±15°latitude. In the present study, we emphasized that many times the WMO definition is not able to identify all the complex structures, such as MTs, and developed alternate criteria to delineate the MTs over the tropics effectively. The new criteria are based on the cold point tropopause (CPT) and its neighborhood points of inflection in the temperature profile rather than on lapse rate, which is used in the WMO definition. The method using the new criteria (called the cold point method) identifies MTs that occur below (referred to as Lower Tropopause, LT) and above (referred to as Second Tropopause, ST; and Third Tropopause, TT) the CPT. The percentage occurrences of MTs determined using the cold point method differ from those found using the WMO definition. The percentage occurrence of MTs within the tropics maximizes at the equator, reaching higher values in the northern hemisphere (NH) summer and lower values in the NH winter. Among the MTs, the percentage occurrence of the ST is the highest, followed by that of the LT. The percentage occurrence of MTs within the tropics also shows large longitudinal variability.

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Increase of upper troposphere/lower stratosphere wave baroclinicity during the second half of the 20th century

Cited by 27 publications

References 16 publications

Tropopause folds in ERA‐Interim: Global climatology and relation to extreme weather events

Tropopause folds in ERA‐Interim: Global climatology and relation to extreme weather events

Association of double tropopause events with baroclinic waves

Multiple tropopauses in the tropics: A cold point approach

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