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Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach

Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach. Fred Kucharski, Annalisa Bracco 1 , Jürgen Kröger , Franco Molteni 2, Jin Ho Yoo Earth System Physics, the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy – jkroeger@ictp.it

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Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach

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  1. Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach Fred Kucharski, Annalisa Bracco1, Jürgen Kröger, Franco Molteni2,Jin Ho Yoo Earth System Physics, the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy – jkroeger@ictp.it 1now at Georgia Tech, Atlanta, GA, USA 2now at ECMWF, Reading, England

  2. IMR index Kucharski et al. (2007) ENSO – Asian Summer Monsoon teleconnectionRegression of precipitation onto NINO3.4 (190-240E, 5S-5N) in JJAS

  3. Lead-lag correlations between Indian rain and ENSONINO3 (150-90W, 5S-5N) and JJAS-IMR (70-95E, 10-30N) indices Kucharski et al. (2007)

  4. ICTP atmospheric GCM “SPEEDY” Spectral dynamical core (Held and Suarez 1994) Resolution: T30L8 (~ 3.75 deg x 3.75 deg) Simplified physical parameterizations (Molteni, 2003) MIAMI ocean GCM “MICOM” (v2.9; Bleck et al., 1992) Indian Ocean configuration (30E - 135E, 30S – 30N) 1 deg x 1 deg , 20 isopycnal layers Sponge layer and initialization data from Levitus (1994) Prescribed SST outside ocean GCM domain! The ICTP coupled global climate modelTier1.5: global atmosphere and local ocean

  5. The ICTP coupled global climate modelExperimental set-up: from Tier1 & Tier2 to Tier1.5 1Only the ECMWF, Meteofrance (METF), UK-Metoffice (UKMO) hindcasts (1959-1999) are considered

  6. DEMETER seasonal hindcastspredicted (ECMWF) vs. observed SST

  7. El Nino (> 1 stdv) La Nina (> 1 stdv) Indian summer monsoon rainfall (JJAS)IMR & NINO3.4 indices

  8. El Nino (> 1 stdv) La Nina (> 1 stdv) Indian summer monsoon rainfallhindcasted IMR & NINO3.4 indices

  9. IMR correlationsCorrelation skill (indiv. membrs.) and coefficient (CRU observ.)

  10. ENSO – Asian Monsoon teleconnectionRegression of precipitation onto NINO3.4 in JJAS

  11. DEMETER seasonal hindcastspredicted vs. observed SST

  12. The Tier1.5 approach • considerably improves the DEMETER hindcasts • has great potential to aim as a tool for seasonal predictions of IMR • confirms the importance of coupled air-sea feedbacks in the Indian Ocean

  13. JJAS mean SST bias in the DEMETER models

  14. ICTP AGCM stand-alone model: GCM of intermediate complexity • Spectral dynamical core (Held and Suarez 1994) • Truncation currently at T30 (~3.75x3.75 degrees) • 5, 7 or (recently) 8 vertical levels • Variables: Vor, Div, T, log(ps) and Q • Physical parameterizations of Convection (mass flux) Large-scale condensation (RH criterion) Clouds (diagnosed) Short-wave radiation (two spectral bands) Long-wave radiation (four spectral bands) Surface fluxes of momentum and energy (bulk formulas) Vertical diffusion • Land-temperature calculated in simple model of 1-m soil layer • Mixed-layer option

  15. The ICTP coupled global climate modelExperimental set-up: from Tier1 & Tier2 to Tier1.5 • Ingredients: • SST from HadISST or DEMETER1 as “pacemaker” • Suite of experiments: • OBS-TIER1.5: coupled GCM (Indic) + HadISST elsewhere • DEM-TIER1.5: coupled GCM (Indic) + DEMETER elsewhere • OBS-TIER2: atmospheric GCM + HadISST everywhere 1Only the ECMWF, Meteofrance, UK-Metoffice Tier1 hindcasts are considered

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