A simple climatology of westerly jet streams in global reanalysis datasets part 1: mid-latitude upper tropospheric jets
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A simple closed contour object identification scheme has been applied to the zonal mean monthly mean zonal wind fields from nine global reanalysis data sets for 31 years of the satellite era (1979–2009) to identify objects corresponding to westerly jet streams. The results cluster naturally into six individual jet streams but only the mid-latitude upper-tropospheric jets are considered here. The time series of the jet properties from all reanalyses are decomposed into seasonal means and anomalies, and correlations between variables are evaluated, with the aim of identifying robust features which can form the basis of evaluation metrics for climate model simulations of the twentieth century. There is substantial agreement between all the reanalyses for all jet properties although there are some systematic differences with particular data sets. Some of the results from the object identification applied to the reanalyses are used in a simple example of a model evaluation score for the zonal mean jet seasonal cycle.
KeywordsJet stream climatology Reanalysis data Upper tropospheric jets Object identification Seasonal cycle metric
Twentieth century Reanalysis V2 data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd/. Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE) program, and Office of Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office.
- Dzerdzeevskii BL (1945) Tsirkuliatsionnye skhemy v troposfere. Tsentral’noi Arktiki. Izd. Akad. Nauk [English transl. Sci. Rep. No. 3, Contract AF 19 (122)-3228. UCLA]Google Scholar
- Jones E, Oliphant E, Peterson P et al (2001) SciPy: Open source scientific tools for Python. http://www.scipy.org/. Accessed 05 Nov 2014
- Shapiro MA, Keyser D (1990) Fronts, jet streams, and the tropopause. In: Newton CW, Halopainen EO (eds) Extratropical cyclones: the Erik Palmen Memorial volume. American Meteorological Society, Bostan, MA, pp 167–189 Google Scholar
- Wilks DS (2011) Statistical methods in the atmospheric sciences. International geophysics series, vol 100, 3rd edn. Academic Press, LondonGoogle Scholar
- WMO (1995) Manual on Codes. WMO Publ. 306, Vol. 1.1 World Meteorological Organization, Avenue Giuseppe- Motta 41, CP2300, 1211 Geneva 2, SwitzerlandGoogle Scholar