1 / 21

Evidence Linking Arctic Amplification with Changing Weather Patterns in Mid-Latitudes

Evidence Linking Arctic Amplification with Changing Weather Patterns in Mid-Latitudes . Jennifer Francis Institute of Marine and Coastal Sciences Rutgers, the State University of New Jersey in collaboration with Steve Vavrus University of Wisconsin-Madison.

zaide
Download Presentation

Evidence Linking Arctic Amplification with Changing Weather Patterns in Mid-Latitudes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evidence Linking Arctic Amplification with Changing Weather Patterns in Mid-Latitudes Jennifer Francis Institute of Marine and Coastal Sciences Rutgers, the State University of New Jersey in collaboration with Steve Vavrus University of Wisconsin-Madison

  2. Chain of Events Linking Arctic Amplification (AA) with Increased Extreme Weather in Mid-Latitudes Poleward temperature gradient weakening Upper-level flow becoming more meridional 500 mb zonal winds decreasing where gradient weakens Amplitude of Rossby waves increasing, blocking more likely Large-scale waves progress more slowly eastward More persistent weather patterns, extremes more likely Arctic Amplification

  3. 1 Winter JFM Spring AMJ Summer JAS Fall OND JAS T 1000mb 90-70oN – 70-30o N Arctic Amplification OND 1000-500mb Thickness 2000 to 2012 2000 to 2012

  4. 2 3 PDO? AMO? Poleward temperature gradient weakening 500 mb zonal winds decreasing where gradient weakens 20 10 0 -10 -20 OND % change in 500 mb zonal winds in 4 x CO2 run of CCSM4 Trends in poleward thickness gradient (1000-500 hPa) from 1979 to 2012 Winter Fall Spring Summer 30oN45oN60oN 500 hPa U anom.

  5. 5 Amplitude of Rossby waves increasing, blocking more likely Francis and Vavrus, GRL 2012

  6. Trends in Amplitude deg/dec 5 OND Northern Hemisphere JAS Northern Hemisphere 500mb heights 2000-2012 Amplitude of Rossby waves increasing, blocking more likely Trends in Amplitude Ridge peaks Blocking More likely? Trend in ridges Trough bottoms from Barnes (2013) Amplitude

  7. Other studies do not find a robust increased frequency of blocking highs… Winter (DJF) Summer (JJA) Difference in frequency of blocking highs in CMIP3 models between end of 21st century (A2) and 20th century From E. Barnes et al, Clim. Dyn., 2012 MERRA Reanalysis 1980-2012 From E. Barnes et al, GRL, in press

  8. 5 Jan 6 2014 “Polar Vortex” Amplitude of Rossby waves increasing, blocking more likely Blocking => “Extreme Waviness” March 2012 Heatwave A typical blocking high Unprecedented Spain flooding Record snowfall in Japan

  9. Types of “Extreme Waviness” Typical blocking pattern “Contour Folding” Extreme Amplitude ID and count “extreme waves” exceeding 40olatitude

  10. 5 1000-500mb Thickness Anomalies Amplitude of Rossby waves increasing, blocking more likely OND Northern Hemisphere U500 r = -0.68 High-amplitude waves Folding contours High-Amp Waves Folding contours

  11. 5 HadGEM CCSM4 Amplitude of Rossby waves increasing, blocking more likely Do GCMs capture this behavior? => 4 members of CMIP5: MPI OND Northern Hemisphere U500 High-amplitude waves GFDL Folding contours Models seem to capture about the right number, some have increasing trends, some not.

  12. 7 More persistent weather patterns, extremes more likely • Winter cold extremes • Fall and winter sea-ice loss associated with cold extremes, but influence of winter ice is stronger • Summer heat waves • Summer loss of sea-ice and snow cover associated with heat waves, but sea-ice influence is stronger Tang, Zhang, Yang, and Francis, ERL (2013) Tang, Zhang, and Francis, Nature Cl. Ch. (2013)

  13. Attack of the Polar Vortex – Early January 2014 Warm Cold Warm

  14. Summary • Some links in the chain are solid: • AA is emerging in all seasons, strongest in fall • Poleward temp. gradients weakening, but seasonally and spatially variable • Where gradients weaken, upper-level zonal winds decreasing, flow becoming more meridional, high-amp waves more frequent • Others not so much: • Changing amplitude and propagation speed of large-scale waves, mechanism linking to AA • Changing frequency of persistence of weather patterns • Interactions among AA and other large-scale influences (ENSO, PDO, NAM, PNA, stratosphere, etc.) • Thank-you! francis@imcs.rutgers.edu

  15. Extras

  16. 4 Upper-level flow becoming more meridional OND CCSM4 4 x CO2 Change in Meridional Wind Fraction @45oN Winter +33% Spring +21% Summer +21% Fall +19% Trends in meridional component of the 500 hPa wind (1979 to 2011) Less wavy More wavy

  17. 6 Large-scale waves progress more slowly eastward From Barnes (2013) “We find a robust decrease in wave phase speeds in OND, which is consistent with the u500 reductions.”

  18. An Artifact of the Methodology? 500 mb height with maximum waviness 1980-1995 1996-2011 500 mb height contour used in FV12 Wave amplitude (deg. latitude) from Barnes (2013)

  19. An Artifact of the Methodology? Typical 500 hPa pattern in Nov 1980-1995 1996-2011 Contour with max waviness has different shape from FV12’s contour in max gradient Wave amplitude (deg. latitude) from Barnes (2013)

  20. An Artifact of the Methodology? Contour with max waviness is 15o farther north, not in max wind zone, not representative of jet stream trajectory. Contour with max waviness has different shape from FV12’s contour in max gradient

  21. Anomalies in zonal-mean heights and zonal winds for OND 2007-2012

More Related