Computation of changes in explosive weather systems during the 20th century

• Main Authors: Osbrough, Stacey Lee, Fredericksen, Jorgen Segerlund
• Format: Article in Journal/Newspaper
• Language: English
• Published: Australian Mathematical Society 2017
• Subjects: instability; stochastic models; filtering; atmospheric flows; Fluid dynamics; Hydrodynamic stability; Stability and instability of geophysical and astrophysical flows; Baxter; North Atlantic
• Online Access: https://journal.austms.org.au/ojs/index.php/ANZIAMJ/article/view/11784

We present a new computational technique for extracting growing weather modes of different frequencies and growth rates from instantaneous six hourly observed atmospheric data. The methodology is applied to examine the changes in the statistics of growing storms and extreme weather events between the mid and late 20th century. The structures of weather modes in different frequency and growth rate bands are determined from the leading (maximum variance) eigenvectors of the associated covariance matrices. A matrix stochastic model is also fitted to the data, with the associated leading eigenvectors related to the dynamical developments. References M. Baxter and R. G. King, Measuring business cycles: Approximate band-pass filters for economic time series. The Review of Economics and Statistics 81(4):575–593, 1999. doi:10.1162/003465399558454 J. S. Frederiksen and R. C. Bell, North Atlantic blocking during January 1979: Linear theory, Q. J. R. Meteorol. Soc. 116:1289–1313, 1990. doi:10.1002/qj.49711649603 J. S. Frederiksen and G. Branstator, Seasonal variability of teleconnection patterns. J. Atmos. Sci. 63:1346–1365, 2005. doi:10.1175/JAS3405.1 J. S. Frederiksen and C. S. Frederiksen, Interdecadal changes in southern hemisphere winter storm track modes. Tellus, A 59:599–617, 2007. doi:10.1111/j.1600-0870.2007.00264.x J. S. Frederiksen and C. S. Frederiksen, Role of dynamical modes in changing southern hemisphere climate. ANZIAM J. 52:C56–C72, 2011. doi:10.21914/anziamj.v52i0.3892 C. S. Frederiksen, J. S. Frederiksen, J. M. Sisson and S. L. Osbrough, Trends and projections of storm formation in coupled climate models. ANZIAM J. 56:C279–C295, 2014. doi:10.21914/anziamj.v56i0.9406 C. S. Frederiksen, J. S. Frederiksen, J. M. Sisson and S. L. Osbrough, Trends and projections of southern hemisphere baroclinicity: the role of external forcing and impact on Australian rainfall. Clim Dyn. 48:3261–3282, 2017. doi:10.1007/s00382-016-3263-8