The Abdus Salam International Centre for Theoretical Physics RegCM3 sensitivity to driving data, resolution and large scale circulation forcing over the Black Sea domain C. Boroneant (Romania), V. Barabanov (Ukraine), V. Alexandrov (Bulgaria) V. Alexandrov (Bulgaria) Group 17 Trieste, 2003

MOTIVATION Geographic domain with complex topography Geographic domain with complex topography Improve understanding of regional climate Improve understanding of regional climate Interest in selection of best data sets to drive the model (initial and boundary conditions) Interest in selection of best data sets to drive the model (initial and boundary conditions) Interest in seasonal anomalies related to the large scale forcing (in the North Atlantic, Mediterranean) Interest in seasonal anomalies related to the large scale forcing (in the North Atlantic, Mediterranean) Domain Topograhy (in m)

PROJECT OBJECTIVES  Examine the influence of the input boundary conditions on model results  Examine the model ability in simulating the regional climate over the Black Sea & adjacent regions  Examine the precipitation field under different NAO phases

MODEL SETTINGS  iy = 34 (68) - grid points on latitude  jx = 51 (102) - grid points on longitude  kz=18 - sigma levels  ds = 50 (25) - resolution 50 (25) km)  clat =  clon =  ntypec = 36 (10’ resolution for global terrain and land-use)  iproj = ‘LAMCON’ (Lambert conformal map projection)  Grell Cummulus parametrization scheme

January 1993, 1994, 1995, 1996, 1997 MODEL RUNS  3 different driving data ECMWF + OISST (1993, 1994, 1995, 1996, 1997) NNRP2 + OISST (1993) ECMWF + GISST (1995)  2 different resolutions (the same domain size) 34x51x18 (50 km) (1995; ECMWF+OISST) 68x102x18 (25km)  2 different large scale circulation conditions NAO+ 1993; 1994, 1995 (ECMWF+OISST) NAO- 1996, 1997 NAO- 1996, 1997

Comparison CRU –data RegCM (ECMWF+OISST) CRU –data RegCM (ECMWF+OISST)

RegCM Precipitation rate (mm/day) January 1993 ECMWF +OISST NNRP2 +OISST

RegCM Precipitation rate (mm/day) January 1995 ECMWF +OISST ECMWF +GISST

RegCM - different resolutions (the same domain ) January 1995; ECMWF+OISST 50 km 25 km 50 km 25 km precipitation rate (mm/day)

spatial avg. Jan RegCM3 precipitation rate (mm/day) Res 50 Km ; res 25 km

SLP RMSE (RegCM vs ECMWF), 25 km

NAO Index and related weather conditions

Correlation map between surface precipitation rate (Dec-Feb) and the NAO Index,

Comparison between RegCM (ECMWF+OISST) and CRU driven by different large scale circulation conditions Jan Comparison between RegCM (ECMWF+OISST) and CRU driven by different large scale circulation conditions Jan 1993 NAO+ Jan 1996 NAO-

Concluding remarks  No significant differences in precipitation when using ECMWF or NNRP2 datasets neither for OISST or GISST have been found  Some differences between observations in CRU data and RegCM precipitation are shown in our simulations  Mezoscale features of precipitation are better represented in the higher resolution simulations  RegCM is able to reproduce different regional precipitation patterns according to the large scale circulation regime related to the NAO phases, but shows some differences in comparison to CRU observations.

Interest in further work … Enlarge the domain Longer period (20-30 years) Look at seasonal variability (DJF, JJA) in the domain forced by circulation regimes in the North Atlantic and the Mediterranean Climate change scenarios in the region