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Showing total 38 results
38 results

7. Vb Cyclones Synchronized With the Arctic‐/North Atlantic Oscillation

Author

M. Hofstätter and Günter Blöschl

Subjects
Western Mediterranean, Atmospheric Science, 010504 meteorology & atmospheric sciences, 02 engineering and technology, 01 natural sciences, Oceans, Earth and Planetary Sciences (miscellaneous), Stochastic Phenomena, 020701 environmental engineering, Research Articles, Climatology, teleconnection, Climate and Dynamics, Climate and Interannual Variability, Synoptic‐scale Meteorology, Vb track, Jet stream, Oceanography: General, mid latitude cyclones, climate change, Geophysics, Atmospheric Processes, Cyclone, Ocean Monitoring with Geodetic Techniques, Mathematical Geophysics, Fronts and Jets, Geology, Oceanography: Physical, Research Article, clustering, Persistence, Memory, Correlations, Clustering, Atmospheric circulation, 0207 environmental engineering, Climate change, Hiatus, Decadal Ocean Variability, Extreme Events, Geodesy and Gravity, Global Change, 0105 earth and related environmental sciences, Climate Change and Variability, Stochastic Processes, Climate Variability, General Circulation, Mass Balance, Arctic oscillation, 13. Climate action, Space and Planetary Science, North Atlantic oscillation, Space Plasma Physics, Natural Hazards, Teleconnection
Abstract

Vb cyclones typically emerge in the Western Mediterranean and propagate to the Northeast into Central Europe. This paper explores the temporal characteristics of Vb cyclone occurrence based on cyclone tracks identified at the atmospheric levels of Z700 and sea level pressure, using JRA‐55 reanalysis data for the period 1959–2015. The risk of Vb occurrence was significantly high in the 1960s and has remained at a lower level since then. Vb cyclones do not occur fully randomly according to a Poisson point process. Eleven well‐separated and distinct clusters as well as 11 hiatus periods are identified, with average occurrence rates of 21.5 and 5.2 yrea−1, respectively. During the event of Vb, the large‐scale atmospheric circulation is changed into a state favoring the development of successive Vb cyclones. Clustering is very prominent in the case of Genoan Vb cyclones in summer as well as those Vb cyclones developing over the Iberian Peninsula or the North African Coast in winter. Superposition of the polar and the subtropical jet stream over the Western Mediterranean is identified as a main feature at the onset of Vb cyclones. Vb cyclone occurrence appears to be synchronized with the Northern Atlantic Oscillation (NAO; at Z500) and Arctic Oscillation (AO; at Z1000). Clusters have occurred when both NAO and AO were negative. This relation applies to Western Mediterranean cyclones not following a Vb track as well, however to a much weaker extent. In contrast, Vb cyclone frequency was particularly low from 1988 to 1997 during a sustained positive phase of both NAO and AO., Key Points In the past 50 years, the frequency of Vb cyclones was high in the 1960s and lower since thenVb cyclones were strongly synchronized with NAO and AO; high frequency clusters occurred when NAO and AO were negativeThe coupling of the polar and the subtropical jet stream over the Western Mediterranean is a driving mechanism of the onset of Vb cyclones

Published
2019

29. Atlantic Climate Variability and Predictability : A CLIVAR Perspective

Author

Hurrell, J. W., Visbeck, M., Busalacchi, A., Clarke, R. A., Delworth, T. L., Dickson, R. R., Johns, W. E., Koltermann, K. P., Kushnir, Y., Marshall, D., Mauritzen, C., McCartney, M. S., Piola, A., Reason, C., Reverdin, G., Schott, F., Sutton, R., Wainer, I., and Wright, D.

Published
2006