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2 nd RASM Workshop 2012 Spring

2 nd RASM Workshop 2012 Spring. Brandon J. Fisel Iowa State University Department of Geological and Atmospheric Sciences Monterey, CA 14-18 May. overview. Sea ice – atmosphere interactions recent, rapid sea-ice decline Model circulation regimes exist Goal sea-ice area changes

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2 nd RASM Workshop 2012 Spring

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  1. 2nd RASM Workshop 2012 Spring Brandon J. Fisel Iowa State University Department of Geological and Atmospheric Sciences Monterey, CA 14-18 May

  2. overview • Sea ice – atmosphere interactions • recent, rapid sea-ice decline • Model circulation regimes exist • Goal • sea-ice area changes • affects persistent circulation regimes • implications for predictability of future • atmospheric circulation • seasonal T extremes 2nd RASM May 2012

  3. methodology • WRF-ARW 3.1 • CORDEX domain 50 km resolution Analysis region 2nd RASM May 2012

  4. methodology (cont…) • ECMWF (ERA-Interim); 6-hr • SST and sea ice; prescribed; 12-hr • 1 Ensemble; 16 members • June – December, 2007 • 1 or 2 regimes • Model-based clustering • model selection; BIC • model fit; penalty for model complexity • Time windows • > synoptic time frame; 7 & 11 days 2nd RASM May 2012

  5. methodology (cont…) • Seasonal T extremes • JJA and OND; 1st and 99th percentile • regions; ANC, AS1 and SC • land points only ANC AS1 SC 2nd RASM May 2012

  6. regimes 1 regime 2 regimes;significantly separated 2 regimes;differingtrends 2nd RASM May 2012

  7. regimes (cont…) significantly separated high MSLP low MSLP differing trends c) high MSLP d) low MSLP 2nd RASM May 2012

  8. regimes (cont…) • Model variability < 8 hPa > 8 hPa 2nd RASM May 2012

  9. regimes (cont…) • BIC2 > BIC1 2nd RASM May 2012

  10. regimes (cont…) • Regime streaks • JJA: tendency to remain in one mode of regime behavior • Slower evolving atmospheric flow 2nd RASM May 2012

  11. regimes (cont….) 2-Regime JJA How persistent do days fall into a 1 or 2-regime window? 2-Regime OND More persistent days a calendar date falls into a 2-regime window. 2nd RASM May 2012

  12. extremes 2-Regime JJA [1st P] Cold extremes preferred in 2-regime behavior. 2-Regime OND [99th P] Warm extremes preferred in 1-regime behavior. 2nd RASM May 2012

  13. summary • Multiple dynamic regimes • persistent, multiple regimes (JJA) • less persistent, multiple regimes (OND) • persistent, 1-regime (September) • Implications • changing sea-ice area affects regime persistence • future predictability of atmosphere • future decline in summer sea ice • more persistent regime behavior? 2nd RASM May 2012

  14. summary (cont…) • Temperature extremes • tendency for more cold (warm) extremes with 2(1)-regime behavior • Future work • regimes: coupled model; modeled vs. prescribed SST’s; similar behavior? • T extremes: 20-year simulation (uncoupled WRF, RASM) • change in energy/moisture budgets allow for a more extreme, future arctic? 2nd RASM May 2012

  15. ? questions E-mail: bjfisel@gmail.com 2nd RASM May 2012

  16. regimes Ensemble MSLP Model Estimated Mean 95% CI

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  29. regimes 2-Regime September More persistent 1-regime behavior vs. JJA and OND. 2nd RASM May 2012

  30. extremes 2-Regime Sept. [1st P] Cold extremes preferred in 2-regime behavior. 2-Regime Sept. [99th P] Warm extremes preferred in 1-regime behavior. 2nd RASM May 2012

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