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The local response to the NAO in a RegCM 30-year run

The local response to the NAO in a RegCM 30-year run. Roxana Bojariu and Liliana Velea National Institute of Meteorology Bucharest, Romania E-mail:bojariu@meteo.inmh.ro. Large scale NAO features. Data. Simulated data:

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The local response to the NAO in a RegCM 30-year run

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  1. The local response to the NAO in a RegCM 30-year run Roxana Bojariu and Liliana Velea National Institute of Meteorology Bucharest, Romania E-mail:bojariu@meteo.inmh.ro

  2. Large scale NAO features

  3. Data • Simulated data: • air surface temperature, precipitation and sea level pressure from the control run of RegCM forced by the HadCM 3 run (with observed SSTs and sea-ice for the interval 1960-1990). • Resolution 50 km • 119 grids in longitude and 98 in latitude (PRUDENCE domain) • Winter (December to February) • Observed data: • air surface temperature and precipitation from CRU (1960-1990) • air surface and temperature from 59 stations over the Romanian territory (1960-2000)

  4. Analysis methodology Canonical correlation analysis (CCA): • The CCA selects a pair of spatial patterns of two variables such that their time evolution is optimally correlated (Preisendorfer 1988; Zorita et al. 1992; Bretherton, 1992; Kharin 1994; Von Storch 1995). • Before canonical correlation analysis, the original data are usually projected onto their Empirical Orthogonal Functions (EOFs), retaining only a limited number of them in order to minimize the noise. • The CCA patterns are normalized such that the coefficients have standard deviation units, so the patterns represent typical anomalies in their specific units.

  5. 1st CCA CRU Data Air surface temperature (˚C) and SLP (hPa) anomalies Precipitation (mm/day) and SLP (hPa) anomalies

  6. Hurrell’s NAO index (black) and the time series (green) associated with the 1st CCA of SLP and T (CRU data) r=0.70

  7. CCA patterns of air surface temperature RegCM r=0.95 vslp=50% vT=32% CRU r=0.93 vslp=40% vT=38%

  8. CCA patterns of precipitation RegCM r=0.98 vslp=43% vp=31% CRU r=0.93 vslp=42% vp=26%

  9. The local response to NAO type variability over Romanian territory Observations: difference of high and low NAO composites RegCM: 1st CCA SLP/T

  10. Conclusions • The data simulated by RegCM capture features of the local response to NAO type circulation. • In this context, the downscaling of climate change scenarios becomes more reliable for European area. Follow up • The analysis of other sources of variability for the European regions (e.g. Eastern Atlantic pattern). • The analysis of other fields (e.g. snow cover) • The analysis of climate change scenarios.

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