Harlass, Jan

Latif, Mojib

Park, Wonsun

OceanRep

Enhanced vertical atmosphere resolution improvesclimate model simulation of tropical Atlantic SST andinterannual variabilityApril 16, 2015, ViennaOS1.7: Tropical & Subtropical Ocean Circulation,Equatorial to Mid-Latitude Air-Sea InteractionsJan Harlaß, Mojib Latif, Wonsun Parkjharlass@geomar.deGEOMAR Helmholtz Centre for Ocean Research Kiel, Germany13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan Harlaß1 MotivationModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DETropical Atlantic SST biasin CMIP 3 & 5[Xu et al. 2014]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan Harlaß2 MotivationModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DESubsurface temperature bias1◦ wide band along the coast[Xu et al. 2014]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan Harlaß3 MotivationModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEAtmospheric biasesMarch-May, CMIP3Contours: precipitation bias (mm/day), Vectors: surface wind bias (m/s)[Richter & Xie 2008]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan Harlaß4 MotivationModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEHigher model resolutionAnnual mean SST biasCM 2.1, ATM: 200 km L24, Ocean: 100km L50CM 2.5, ATM: 50 km L32, Ocean: 28km L50[Delworth et al. 2014]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivation5 ModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEModel designKiel Climate Model (KCM)ORCA2I 2◦x 2◦I latitudinalrefinementI 31 levelsI No changes[Park et al. 2009]ECHAM5I T42 (2.8◦, ~300km) L31 / L62 LR / LR_VI T159 (0.75◦, ~80km) L31 / L62 HR / HR_V13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivation5 ModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEModel designKiel Climate Model (KCM)ORCA2I 2◦x 2◦I latitudinalrefinementI 31 levelsI No changes[Park et al. 2009]ECHAM5I T42 (2.8◦, ~300km) L31 / L62 LR / LR_VI T159 (0.75◦, ~80km) L31 / L62 HR / HR_V13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivation5 ModelSSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEModel designKiel Climate Model (KCM)ORCA2I 2◦x 2◦I latitudinalrefinementI 31 levelsI No changes[Park et al. 2009]ECHAM5I T42 (2.8◦, ~300km) L31 / L62 LR / LR_VI T159 (0.75◦, ~80km) L31 / L62 HR / HR_V13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModel6 SSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DESST biasJuly-September [JAS]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModel6 SSTPrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DESST biasJuly-September [JAS]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSST7 PrecipitationEquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DETotal Precipitation biasJAS13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitation8 EquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEZonal section along the equator3◦S-3◦N, JASHadISSTLRLR_VHRHR_V13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitation9 EquatorBenguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DETemperature bias5◦S-5◦N, annual average13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquator10 Benguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEMeridional velocityZonally averaged over 3 gridpoints from the coast, annual average[Xu et al. 2014]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquator10 Benguela RegionVariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEMeridional velocityZonally averaged over 3 gridpoints from the coast, annual average[Xu et al. 2014]13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquatorBenguela Region11 VariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DEInterannual variabilityStandard deviation of SST in ATL3 (20◦W -0◦E , 3◦S-3◦N)HadISST LR LR_V HR HR_V13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquatorBenguela Region12 VariabilitySummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DERegression ATL3 index on SSTJAS, Contours: HadISST, Shading: bias13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquatorBenguela RegionVariability13 SummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DESummaryI Increased atmospheric horizontal resolution reducesTropical Atlantic SST bias (T42->T159)I Spatial bias pattern remainsI High resolution in both the horizontal and verticalstrongly reduced biases in the Tropical Atlantic (T159 L62)I Improved mean state in the ocean and the atmosphereI Improved interannual variabilityI Consistent choice of horizontal and vertical resolution!13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquatorBenguela RegionVariability13 SummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DESummaryI Increased atmospheric horizontal resolution reducesTropical Atlantic SST bias (T42->T159)I Spatial bias pattern remainsI High resolution in both the horizontal and verticalstrongly reduced biases in the Tropical Atlantic (T159 L62)I Improved mean state in the ocean and the atmosphereI Improved interannual variabilityI Consistent choice of horizontal and vertical resolution!13Enhanced VerticalAtmosphereResolution ImprovesClimate ModelSimulationJan HarlaßMotivationModelSSTPrecipitationEquatorBenguela RegionVariability13 SummaryGEOMAR Helmholtz Centrefor Ocean Research Kiel, DESummaryI Increased atmospheric horizontal resolution reducesTropical Atlantic SST bias (T42->T159)I Spatial bias pattern remainsI High resolution in both the horizontal and verticalstrongly reduced biases in the Tropical Atlantic (T159 L62)I Improved mean state in the ocean and the atmosphereI Improved interannual variabilityI Consistent choice of horizontal and vertical resolution!Thank you for your attention!Harlaß, J., Latif, M., Park, W. (2015). Improving Climate ModelSimulation of Tropical Atlantic Sea Surface Temperature: TheImportance of Enhanced Vertical Atmosphere Model Resolution,Geophys. Res. Lett., 42, doi:10.1002/2015GL063310http://www.geomar.de/~jharlass-ejharlass@geomar.deI Delworth, T. L., Rosati, A., Anderson, ... (2012). Simulated Climate and Climate Changein the GFDL CM2.5 High-Resolution Coupled Climate Model. Journal of Climate, 25(8),2755–2781. doi:10.1175/JCLI-D-11-00316.1I Park, W., Keenlyside, N., Latif, ... (2009). Tropical Pacific Climate and Its Response toGlobal Warming in the Kiel Climate Model. Journal of Climate, 22(1), 71–92.doi:10.1175/2008JCLI2261.1I Richter, I., & Xie, S.-P. (2008). On the origin of equatorial Atlantic biases in coupledgeneral circulation models. Climate Dynamics, 31(5), 587–598.doi:10.1007/s00382-008-0364-zI Xu, Z., Chang, P., Richter, I., ... (2014). Diagnosing southeast tropical Atlantic SST andocean circulation biases in the CMIP5 ensemble. Climate Dynamics, 43(11), 3123–3145.doi:10.1007/s00382-014-2247-9

Enhanced vertical atmosphere resolution improves climate model simulation of tropical Atlantic SST and interannual variability

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