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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 Roxana Bojariu and Liliana Velea National Institute of Meteorology Bucharest, Romania E-mail:bojariu@meteo.inmh.ro
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)
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.
1st CCA CRU Data Air surface temperature (˚C) and SLP (hPa) anomalies Precipitation (mm/day) and SLP (hPa) anomalies
Hurrell’s NAO index (black) and the time series (green) associated with the 1st CCA of SLP and T (CRU data) r=0.70
CCA patterns of air surface temperature RegCM r=0.95 vslp=50% vT=32% CRU r=0.93 vslp=40% vT=38%
CCA patterns of precipitation RegCM r=0.98 vslp=43% vp=31% CRU r=0.93 vslp=42% vp=26%
The local response to NAO type variability over Romanian territory Observations: difference of high and low NAO composites RegCM: 1st CCA SLP/T
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.