Hypothesis for ESPC Demo #1: Flow-followingfinite-volume. Icosahedral

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1 Blocking Error in 10 day to 1 year Global Model Forecasts, Dependency on Resolution and Numerics Stan Benjamin, Shan Sun, Rainer Bleck, John Brown NOAA Earth System Research Laboratory, Boulder CO USA Episodic Weather Extremes from Blocking Longer-term weather anomalies from atmospheric blocking -Defined here as either ridge or trough quasistationary events with duration of at least 4 days to 2+ months Related papers in S2S Workshop -Wed-330pm - Shan Sun 1-y tests of FIM/HYCOM AMIP/CMIP -Tues-950am - Rainer Bleck New blocking diagnostic 1 WMO Intl. Conf Subseasonal to Seasonal Prediction ESPC demo #1 target: improved 1-6 month forecasts of blocking and related weather extremes 2 Blocking frequency as a function of global model resolution Jung et al., 2012, J. Climate: High-res ECMWF experiments for Project ATHENA T511 necessary T511 topo necessary AMIP Tibaldi-Molteni Index 3 ESPC demo target: improved 1-6 month fcst of blocking Processes related to blocking onset, cessation, prolongation Extratropical wave interaction MJO life cycle Other tropical procs/enso Tropical storms and their extratropical transitions Sudden stratospheric warming events Snow cover anomalies Soil moisture anomalies Model component sensitivity 4 Hypothesis for ESPC Demo #1: X-section location Suitably configured coupled global models are capable of usefully skillful forecasts of the probability of blocking / stationary waves and related significant weather events for seasonal forecasts What s new Next generation global AMIP/CMIP models (e.g., Dynamic Core Model Intercomparison Project) 5 Flow-followingfinite-volume Icosahedral Model FIM Key developers ESRL - Rainer Bleck, Shan Sun, Ning Wang, Jian-Wen Bao, John Brown, Stan Benjamin, Georg Grell, (Jin Lee, Sandy MacDonald) Weather NWP Evaluation Temp at lowest level NCEP Fanglin Yang Seasonal Evaluation (planned) ESRL-PSD Kathy Pegion, George Kiladis MJO evaluation Randy Dole, Judith Perlwitz blocking/ssw eval CPC compare with NMME 6

2 FIM design vertical coordinate Hybrid (sigma/ isentropic) vertical coordinate Improved conservation using quasi-material surfaces, reduced vertical dispersion. Improved transport by reducing numerical dispersion from vertical crosscoordinate transport, improved stratospheric/tropospheric exchange. Used in NCEP Rapid Update Cycle Used in HYCOM ocean model Installed as generalized s vertical coordinate - can be replaced with sigma-p or other coordinates. (RUC) model 7 FIM numerical atmospheric model Horizontal grid Icosahedral, Δx=240km/120km / 60km/30km/15km/10km Vertical grid ptop = 0.5 hpa, θtop ~2200K Generalized vertical coordinate Hybrid option (64L, 38L, 21L options currently) GFS-like option (64 levels) Physics GFS physics suite (May 2011 version, May 2013 McICA radiation), options for Grell-Freitas cumulus, WRF opts Coupled model extensions Chem WRF-chem/GOCART Ocean icosahedral HYCOM (no coupler), tri-polar HYCOM (with coupler) (Shan Sun, Wed 330 paper) hPa Height Anomaly Correlation FIM-30km vs. GFS T574 (27km) NCEP operational 12 month NWP test August 2012 July year ( ) Atlantic hurricane track error results % forecast error (FE) improvement over HFIP baseline (Larger is better.) Both FIM and GFS used the same GFS hybrid-enkf initial conditions FIM used r3162, same config as 1-yr retro ( ) NH, dieoff FIM minus GFS Aug 12 Jul 13 SH, dieoff FIM minus GFS Aug 12 Jul 13 95% stat signif diff SH, dieoff Jun12 May13 12h 24h 36h 48h 72h 96h 120h 2d 4d 6d 8d 10d 2d 4d 6d 8d 10d FIM better skill than GFS for 5+ day duration in N. Hemisphere, 4+ day duration for S. Hemisphere, 9 statistically significant in both SH and NH Typhoon Megi Oct 2010 Extratropical transition leading to Pac/NA block via Rossby wave breaking over Pacific 15km FIM forecast ( vert coord) October 2010 Record extratropical SLP over US (958 hpa Minnesota 26 Oct 10) Dynamic tropopause: Potential temp on potential vorticity=2 surface 11 Experiment design just started FIM 1 year AMIP runs Initialized December 2008 from GFS Horizontal resolution exps with 240, 120, 60, 30km 64 levels, experiments with 2 vertical coordinates hybrid isentropic sigma θ σ sigma pressure σ p May 2011 GFS physics (incl. updated shallow cu), McICA from CFSv2) 3 runs for each Δx experiment Initialized 00z 1 Dec, 2 Dec, 3 Dec GFS analyses Evaluation Blocking frequency Percentage of anomaly (500 hpa ht) days per month 12

3 Resolution experiments on blocking (Tibaldi-Molteni) 2009 Blocking Frequency from NCEP Reanalysis (black) and 3-mem FIM AMIP forecast ensembles (color red, green, blue)km 120km 240km Mean 500z anomaly Mar 2012 Percentage of 500hPa height anomaly days per month Useful complement to blocking per Tibaldi-Molteni (or Pelly-Hoskins) Focuses on daily consistency % of anomaly days/mon Mar FIM-30km 1-yr AMIP runs started on consecutive days Run 1 Run 2 Run 3 Average of 3 runs NCEP Reanalysis: 500 hpa: Percentage of Anomaly Days Dec08-Nov09 Dec Jan FIM 1-yr AMIP runs - DJF Dec - 3 FIM 1-yr AMIP runs - MAM Mar Jan Apr May 17 18

4 - 3 FIM 1-yr AMIP runs - JJA Jun - 3 FIM 1-yr AMIP runs - SON Sep Jul Oct Aug Nov vs. FIM 1-yr AMIP runs - December - vs. FIM 1-yr AMIP runs Jan vs. FIM 1-yr AMIP runs vs. FIM 1-yr AMIP runs MAM Obs Mar Apr May 23 24

5 - vs. FIM 1-yr AMIP runs JJA Obs Jun - vs. FIM 1-yr AMIP runs SON Obs Sep Jul Oct Aug Nov Preliminary Results / Plans 1 year FIM AMIP resolution experiments FIM isentropic sigma vertical coordinate, icosahedral horizontal grid Resolution More realistic blocking (% anomaly days/month) from higher res (30, 60km) than coarser res (120, 240) versions in some seasons (DJF), not in others Cold bias (in 500 heights) at coarser resolution (120km, 240km) Vertical coordinate (θ σ vs. σ p ) Cold bias (in 500 heights) evident with σ p coordinate, less so with θ σ Hypotheses: 1) Cold bias in climate models from vertical diffusion in quasihorizontal vertical coordinates (Johnson, 1997, J. Climate, or 2) Difference in precipitation/cloud processes from different vertical coord. Upcoming (with NOAA/ESRL/PSD, CPC, NMME) Frequency plots for blocking and % anom days/mo Experiments for YOTC, DYNAMO periods with CFSv2, FIM, (CMIP), blocking processes (MJO, SSW, etc), physics (CPT) Increase to members per month for exps Compare with CFSv2 and other seasonal forecast models (National Multi Model Ensemble) Related papers with online presentations in S2S Conference -Wed 3:30 - Shan Sun 1-y tests of FIM/HYCOM AMIP/CMIP -Tues 9:50 - Rainer Bleck Blocking diagnostic w/ streamline curvature 27