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Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach

El Nino (> 1 stdv). El Nino (> 1 stdv). Kucharski et al. (2007). La Nina (> 1 stdv). La Nina (> 1 stdv). IMR index.

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Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach

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  1. El Nino (> 1 stdv) El Nino (> 1 stdv) Kucharski et al. (2007) La Nina (> 1 stdv) La Nina (> 1 stdv) IMR index Correlation Coefficient (CC) between a 4-month average of NINO3 (150-90W, 5S-5N) and the IMR index in JJAS: (circles) observations vs. (crosses) Tier1.5 approach; lagged CCs are established by shifting the averaging window over NINO3 month by month relative to the summer IMR – high negative values at positive lag indicate IMR leading NINO3 by about a season Kucharski et al. (2007) Indian summer monsoon rainfall (cont.)Observed & modeled/hindcasted IMR & NINO3.4 indices Improved hindcasts of Indian monsoon rainfall using a Tier 1.5 approach ENSO – Asian Summer Monsoon teleconnection in DEMETER, our Tier1.5 hindcast, & Tier2 ENSO – Asian Summer Monsoon teleconnectionWarm El Nino events are accompanied by a dry summer season and vice versa 4 DEMETER seasonal hindcasts in the Nino3.4 region Bias correction of predicted (May to Oct..) SST is of utmost importance Indian summer monsoon rainfall (IMR index)Correlation skill (indiv. members) and coefficient (CRU observ.) Regression of precipitation onto NINO3.4 (190-240E, 5S-5N) in JJAS: (left) observations (top) Tier1.5 exp. Lead-lag correlations between Indian rain and ENSOENSO in its developing stage remotely influences the dynamics of IMR Fred Kucharski, Annalisa Bracco1, Jürgen Kröger, Franco Molteni2, Jin Ho Yoo Earth System Physics, the Abdus Salam International Centre for Theoretical Physics, Trieste, ITALY 5 3 1 • 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 model & our Tier1.5 approach Tier1.5: global atmosphere and local ocean Tier2: global atmosphere only 1Only the ECMWF, Meteofrance (METF), UK-Metoffice (UKMO) hindcasts (1959-1999) are considered 2 6 Earth System Physics, the Abdus Salam International Centre for Theoretical Physics, Trieste, ITALY, 1now at Georgia Tech, Atlanta, GA, USA, 2now at ECMWF, Reading, England; Contact: jkroeger@ictp.it

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