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Seasonal Climate Discussion - Summer 2009 -

Seasonal Climate Discussion - Summer 2009 -. Mike Blackburn, Andy Turner, Brian Hoskins with input from Nick Klingaman, Jane Strachan, Pier Luigi Vidale Met Office Seasonal Forecast Adam Scaife. Reading, Grantham, IIS Bangalore discussion, 25 November 2009. Summary. Global overview

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Seasonal Climate Discussion - Summer 2009 -

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  1. Seasonal Climate Discussion - Summer 2009 - Mike Blackburn, Andy Turner, Brian Hoskins with input from Nick Klingaman, Jane Strachan, Pier Luigi Vidale Met OfficeSeasonal Forecast Adam Scaife Reading, Grantham, IIS Bangalore discussion, 25 November 2009

  2. Summary Global overview Tropics, with focus on Asia Indian Monsoon very weak Strong East Asian monsoon circulation? Consistent with warm west/central Pacific SSTs Tropical cyclone activity – (contrast active W + E Pacific with quiet Atlantic) Extra-tropics & global teleconnections Monsoon / Mediterranean link Northern Hemisphere extra-tropics – (circulation, impact on UK) Met Office seasonal forecast Hemispheric wave patterns: observational + modelling studies

  3. Global Summary JJA 2009 Wind 150hPa (total) Geopotential Height 200hPa (anom) Surface wind (total) OLR (anomaly)

  4. Global Summary JJA 2009 Wind 150hPa (anomaly) Geopotential Height 200hPa (anom) Surface wind (anomaly) OLR (anomaly)

  5. Developing El Niño – SST anomalies June July August Source: NOAA Climate Diagnostics Bulletin

  6. Developing El Niño – impacts? El Niño impacts (northern summer) OLR anomaly (JJA 2009) NOAA: Climate Prediction Center & ESRL

  7. Transition to El Niño Source: NOAA Climate Diagnostics Bulletin Equatorial anomalies averaged 5N – 5S

  8. Tropics – intraseasonal variability June June July July August August Source: NOAA Climate Diagnostics Bulletin

  9. Tropics – intraseasonal variability June July August x106m2s-1 x106m2s-1  = -2 = -2D , V Source: NOAA Climate Diagnostics Bulletin

  10. June June July July August August Tropics – intraseasonal variability ms-1 m s-1 Source: NOAA Climate Diagnostics Bulletin

  11. Summary Global overview Tropics, with focus on Asia Indian Monsoon very weak Strong East Asian monsoon circulation? Consistent with warm west/central Pacific SSTs Tropical cyclone activity – (contrast active W + E Pacific with quiet Atlantic) Extra-tropics & global teleconnections Monsoon / Mediterranean link Northern Hemisphere extra-tropics – (circulation, impact on UK) Met Office seasonal forecast Hemispheric wave patterns: observational + modelling studies

  12. Dynamical seasonal mean indices Webster-Yang index U850’-U200’ 40-110E, 5-20N JJA JUN JUL 1989 2009 AUG Goswami - Meridional Hadley index V850’-V200’ 70-110E, 10-30N Wang & Fan western index U850south-U850north All dynamical indices show considerable weakening in 2009 Monthly-mean ERA-Interim data

  13. Wang & Fan (western index) Webster-Yang Wang et al (East Asia) Goswami (meridional) Asian Monsoon – daily dynamical indices Source: NCEP – CDAS data

  14. Asian Monsoon – dynamical indices Wang & Fan dynamical monsoon indices

  15. Indian Monsoon – precipitation (IMD)

  16. Indian Monsoon – onset to August Daily OLR anomalies + ‘MJO’ modal projection (Mat Wheeler, BMRC) Symmetric Anti-symmetric ‘MJO’ mode by filtering in the zonal wavenumber / frequency domain, Wheeler & Weickmann (2001)

  17. Indian Monsoon – mid-July to Sept. Daily OLR anomalies + ‘MJO’ modal projection (Mat Wheeler, BMRC)

  18. JUN BMRC filtered OLR data shows clear evidence of eastward propagating “MJO”-type anomalies in the northern tropics (2.5N – 17.5N). JUL AUG SEP OCT { INDIA

  19. The Wheeler-Hendon multivariate MJO index Based on U850, U200, OLR data in near-real time. Near-equatorial. Little evidence for (equatorial) MJO at onset time or during August, unlike OLR index. Strong MJO activity during November (blue)

  20. Northward propagations seen in daily OLR / precip MAY Early onset OLR (anomaly) MAY JUNE JUN JULY ? AUG JUL SEP OCT AUG 70-90E average. Source: NOAA/ESRL

  21. Tropical Cyclone activity North Indian Ocean Basin (No official bounds, most form May-Nov) • First system start: 15 April • 3 depressions; 2 tropical storms • All three made landfall • Aila caused over $40million damage, 330 fatalities (deadliest storm this year) Aila, 25 May, well-defined eye visible (NASA/TRMM)

  22. Summary Global overview Tropics, with focus on Asia Indian Monsoon very weak Strong East Asian monsoon circulation? Consistent with warm west/central Pacific SSTs Tropical cyclone activity – (contrast active W + E Pacific with quiet Atlantic) Extra-tropics & global teleconnections Monsoon / Mediterranean link Northern Hemisphere extra-tropics – (circulation, impact on UK) Met Office seasonal forecast Hemispheric wave patterns: observational + modelling studies

  23. Indian Monsoon impact on Mediterranean? Rodwell & Hoskins (1996): monsoon influence on Mediterranean summer descent

  24. Global Summary JJA 2009 Wind 150hPa (total) Geopotential Height 200hPa (anom) Surface wind (total) OLR (anomaly)

  25. V 250 (total) Z 200 (anomaly) 2009 June July August

  26. Z250 Hovmöller, 45-60° latitude Variable June July Persistent Mobile August

  27. Dynamical Tropopause (weekly averages) June July ~12 days Aug.

  28. JJA09 Met Office Seasonal Forecasts from April / May Ensemble mean – April f/c Ensemble mean – May f/c Analyses (NCEP/NCAR) Z500 Pmsl SST

  29. JJA09 Met Office Seasonal Forecasts from April / May Ensemble mean – April f/c Ensemble mean – May f/c Analyses (NCEP/NCAR) SST T2m Precip !model estimate!

  30. Origin of the 2009 extra-tropical anomalies? Similarity of N.Hem wavetrain pattern in summer 2007/8/9 Is the observed pattern likely to recur? Is it related to a particular forcing? If so, what timescale? Hypotheses & evidence 1) Tropics – (a) ENSO; (b) Asian Monsoon 2) AMO – decadal variability of Atlantic SSTs (Sutton & Hodson, Knight et al) 3) Arctic sea-ice loss (Balmaseda et al, 2009) Idealised experiments for 2007 (Hoskins, Fonseca, Blackburn) Direct Rossby wave response to tropical heating Diagnosis of anomalous forcing – importance of eddy feedback Comparison with ECMWF relaxed seasonal hindcasts

  31. 1b) Tropics: Asian Summer Monsoon Observational evidence of circum-global wavetrain associated with Asian/Indian monsoon (Ding & Wang, 2005) Idealised modelling, including transient eddy feedbacks (Lin, 2009) Observed Z200 composite differences

  32. 1b) Tropics: Asian Summer Monsoon Observed correlation between 200hPa streamfunction and Arabian Sea precipitation (PI1) Model heating and Z 200hPa response Lin (2009)

  33. Origin of the 2007/8/9 anomalies? Remains an open question: Possibility of quasi-resonance, triggered by a number of forcings Hypotheses & evidence: 1) Tropics – (a) ENSO; (b) Asian Monsoon 2) AMO – decadal variability of Atlantic SSTs 3) Arctic sea-ice loss Idealised experiments for 2007: Direct Rossby wave response to tropical heating Diagnosis of anomalous forcing – eddy feedback? Comparison with ECMWF relaxed seasonal hindcasts

  34. - End -

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