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A radius –depth model for midlatitude cyclones in reanalysis data and simulations
Author(s) -
Schneidereit Andrea,
Blender Richard,
Fraedrich Klaus
Publication year - 2010
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.523
Subject(s) - middle latitudes , geopotential height , climatology , cyclogenesis , atmospheric sciences , cyclone (programming language) , geopotential , geostrophic wind , potential vorticity , extratropical cyclone , environmental science , radius , empirical orthogonal functions , vorticity , meteorology , geology , precipitation , physics , vortex , computer security , field programmable gate array , computer science , computer hardware
Abstract Geometric properties of winter (DJF) and summer (JJA) midlatitude cyclones are analysed in reanalysis data, present‐day and global warming simulations. Cyclone centres are identified by the minima of the 1000 hPa geopotential height. Fitting an azimuthally symmetric Gaussian function to the surrounding height field provides cyclone depth (difference between the cyclone centre and the synoptic environment), radius (standard deviation), geostrophic wind and vorticity. Analysing ERA‐40 reanalysis data of different resolutions and Intergovernmental Panel on Climate Change (IPCC) scenario simulations by the coupled atmosphere–ocean general circulation model ECHAM5/MPI‐OM yields mean radii of 300–500 km in winter and 300–400 km in summer. Depth maxima occur in the storm tracks (determined by the bandpass‐filtered variance of the geopotential height), and the smallest radii characterize oceanic cyclogenesis regions. The geostrophic vorticity, derived from the fitted Gaussian model, agrees reasonably well with the observed relative vorticity. Future warmer climate scenarios exhibit smaller radii and weaker depths during winter and summer. An intense growth of the depth is found during the 2 –10 day cyclone life cycles, while the radii reveal negligible growth. Compositing depths with respect to normalized total lifetime leads to rescaled depth life cycles, which collapse to a simple universal function, ã (1 − ã ), for relative cyclone age ã . Copyright © 2010 Royal Meteorological Society