Réf. Ulbrich & al. 2009 - A

Référence bibliographique complète

ULBRICH, U., LECKEBUSCH, G.C., PINTO, J.G. 2009. Extra-tropical cyclones in the present and future climate: a review. Theoretical and Applied Climatology 96, 117–131. DOI 10.1007/s00704-008-0083-8. [Etude en ligne]

Abstract: Based on the availability of hemispheric gridded data sets from observations, analysis and global climate models, objective cyclone identification methods were developed and applied to these data sets. Due to the large amount of investigation methods combined with the variety of different datasets, a multitude of results exist, not only for the recent climate period but also for the next century, assuming anthropogenic changed conditions. Different thresholds, different physical quantities, and considerations of different atmospheric vertical levels add to a picture that is difficult to combine into a common view of cyclones, their variability and trends, in the real world and in GCM studies. Thus, this paper will give a comprehensive review of the actual knowledge on climatologies of mid-latitude cyclones for the Northern and Southern Hemisphere for the present climate and for its possible changes under anthropogenic climate conditions.

Mots-clés

 

 

Organismes / Contact

• Freie Universität Berlin, Institute for Meteorology, Carl-Heinrich-Becker-Weg 6-10, 12165 Berlin, Germany (ulbrich@met.fu-berlin.de - gcl@met.fu-berlin.de)
• Institute for Geophysics and Meteorology, University of Cologne, Kerpener Str. 13, 50923 Köln, Germany (jpinto@meteo.uni-koeln.de)

This work was partially supported by the European Union Programme Energy, Environment and Sustainable Development under the projects ENSEMBLES (contract GOCE-CT-2003–505593-ENSEMBLES) and CIRCE (contract 036961).

 

(1) - Paramètre(s) atmosphérique(s) modifié(s)

(2) - Elément(s) du milieu impacté(s)

(3) - Type(s) d'aléa impacté(s)

(3) - Sous-type(s) d'aléa

Circulation atmosphérique, cyclogenèse

 

 Tempêtes (cyclones extratropicaux)

 

 

Pays / Zone

Massif / Secteur

Site(s) d'étude

Exposition

Altitude

Période(s) d'observation

 

 

 

 

 

 

 

(1) - Modifications des paramètres atmosphériques

Reconstitutions

 

Observations

Trends and variations in reanalysis data: While reanalysis products are produced with a fixed model and assimilation scheme, changes in the available observational data (data types, spatial, and temporal densities) can impose some inhomogeneity into these sets, and the IPCC AR4 (cf. Trenberth et al. 2007, p. 312) states that the detection of long-term changes in cyclone measures is hampered by incomplete and changing observing systems. Recent studies found, however, a general reliability of results for cyclones on the NH: There are no sudden shifts in intensities that would indicate inhomogeneities, and also a comparison with cyclone activity estimated from regional surface and radiosonde data confirmed the general reliability of the data, even though there may be some effect of increasing density of observations in some datasets. [see references in the study]. In contrast to the NH, several sudden swings occur in the SH, apparently related to changes in the observational data sources available for the reanalysis (Wang et al. 2006a).

Northern Hemisphere: Many recent studies show evidence that cyclone frequencies and characteristics have changed in the recent past [see review in the study]. […] Discrepancies between the statements on trends depend on the specific domain boundaries chosen. An overall result is a northward shift of the mid-latitude storm tracks (Wang et al. 2006a; Trigo 2006). Raible et al. (2008) stress that results are also sensitive to both the choice of the tracking scheme and of the reanalysis dataset. In particular, the NCEP data tend to show more significant trends than ERA-40, and the trends over the NP disagree between the methods (see also Wang et al. 2006a). […]

From the review of work outlined [in this article], there seems to be an actual consensus on the following findings: Two distinct regions of high cyclonic activities can be detected in reanalysis data and in the models, one over the North Pacific and one over the North Atlantic, with a secondary center over the Mediterranean. The representation of the latter center is particularly dependent on the spatial resolution of the data and the model considered.

Modélisations

Many recent studies show evidence of a change in cyclone activity under anthropogenic climate change (ACC) [see references in the study]. A major result from an ensemble of different models forced with different greenhouse gas concentrations is that the number of extreme cyclones (core pressure lower than 970 hPa) increases in winter, whereas the total cyclone number is slightly reduced both in the NH and the SH. According to their simple identification procedure based on MSLP minima, the signal increases towards the end of the 21st century, which corroborates with the sensitivity of the signal to the scenario chosen. A general decrease of the number of all cyclones on a hemispheric scale is confirmed in other studies, as is the increase of signals with intensity of GHG forcing. The hemispherically increasing number of extreme events (as suggested by Lambert and Fyfe 2006) is, however, not a general result. Instead, several studies emphasize that enhanced cyclone intensities are only detected for limited areas. […]

From the review of work outlined [in this article], there seems to be an actual consensus on the following findings: Under ACC conditions, the number of all cyclones will be reduced in winter, but in specific regions (over the Northeast Atlantic and British Isles, and in the North Pacific) the number of intense cyclones increases in most models. For the average over the hemisphere, an increase in the number of extreme cyclones is found only when “extreme” is defined in terms of core pressure, while there is a decrease in several models when defining “extreme” from the Laplacian of surface pressure or vorticity around the core.

Hypothèses

 

 

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

This paper reviews the actual knowledge on the broader scale cyclone occurrence, including its identification and tracking from global data sets with “state-of-the-art” methods. It does not analyze and review the internal dynamical structure of cyclone systems and any classification based on it.

A large number of studies of cyclone activity have become available in the recent years. This increase in interest of the scientific community is partly due to the availability of basically homogeneous gridded datasets for the observational period, which in conjunction with the numerical schemes for the identification of cyclones and the quantification of their activity allow detailed studies that were not possible in earlier times. In addition, many GCM simulations both for present-day climate and climate scenarios have recently become available. Their evaluation with respect to cyclone activity can in principle serve to give confidence in the simulated effects of increasing greenhouse gas forcing on the mid-latitude climate. All ingredients for in-depth studies and multi-model ensemble simulations are available. Still, the picture arising from the review of work outlined [in this article] is mixed.

 

(2) - Effets du changement climatique sur le milieu naturel

Reconstitutions

 

Observations

 

Modélisations

 

Hypothèses

 

 

Sensibilité du milieu à des paramètres climatiques

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

 

 

(3) - Effets du changement climatique sur l'aléa

Reconstitutions

 

Observations

 

Modélisations

 

Hypothèses

 

 

Paramètre de l'aléa

Sensibilité des paramètres de l'aléa à des paramètres climatiques

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

 

 

 

 

(4) - Remarques générales

 

 

(5) - Syntèses et préconisations

 

Références citées :

Lambert SJ, Fyfe JC (2006) Changes in winter cyclone frequencies and strengths simulated in enhanced greenhouse warming experiments: results from the models participating in the IPCC diagnostic exercise. Clim Dyn 26:713–728

Raible CC, Della-Marta P, Schwierz C, Wernli H, Blender R (2008) Northern hemisphere extratropical cyclones: a comparison of detection and tracking methods and different reanalyses. Mon Wea Rev 136:880–897

Trigo IF (2006) Climatology and interannual variability of storm-tracks in the Euro-Atlantic sector: a comparison between ERA-40 and NCEP/NCAR reanalyses. Clim Dyn 26:127–143

Wang XLL, Swail VR, Zwiers FW (2006a) Climatology and changes of extratropical cyclone activity: comparison of ERA40 with NCEP-NCAR reanalysis for 1958-2001. J Clim 19:3145–3166