Stan Benjamin, Shan Sun, Rainer Bleck, John BrownNOAA Earth System Research Laboratory, Boulder CO USA

Blocking Error in 10‐day to 1‐year Global Model Forecasts, Dependency on Resolution and Numerics

Related papers in S2S Workshop-Wed-330pm - Shan Sun – 1-y tests of FIM/HYCOM – AMIP/CMIP-Tues-950am - Rainer Bleck – New blocking diagnostic

WMO Intl. Conf Subseasonal to Seasonal Prediction – 11 Feb 20141

Episodic Weather Extremes from BlockingLonger-term weather anomalies from atmospheric blocking -Defined here as either ridge or trough quasi-stationary events with duration of at least 4 days to 2+ months

ESPC demo #1 target: improved 1-6 month forecasts of blocking and related weather extremes

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Blocking frequency as a function of global model resolutionJung et al., 2012, J. Climate: High-res ECMWF experiments for Project ATHENA

T511 necessary

T511 topo necessary

AMIP

Tibaldi-Molteni Index

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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 ESPC demo target: improved 1-6 month fcst of blocking

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Hypothesis for ESPC Demo #1:

• 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)

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Flow-following-finite-volume

Icosahedral Model FIM

X-section location

Temp at lowest level

http://fim.noaa.gov

Key developers

ESRL - Rainer Bleck, Shan Sun, Ning Wang, Jian-Wen Bao, John Brown, Stan Benjamin, Georg Grell, (Jin Lee, Sandy MacDonald)

Weather NWP EvaluationNCEP – Fanglin YangSeasonal Evaluation (planned)ESRL-PSD – Kathy Pegion, George Kiladis – MJO evaluationRandy Dole, Judith Perlwitz –

blocking/SSW evalCPC – compare with NMME

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FIM design – vertical coordinateHybrid (sigma/ isentropic) vertical coordinate • Improved conservation using quasi-material surfaces, reduced vertical dispersion.

Improved transport by reducing numerical dispersion from vertical cross-coordinate transport, improved stratospheric/tropospheric exchange.

• Used in NCEP Rapid Update Cycle (RUC) model

• Used in HYCOM ocean model

Installed as

generalized “s” vertical

coordinate- can be replaced with

sigma-p or other coordinates.

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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 θ-σ option (64L, 38L, 21L options currently)• GFS-like σ-p 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)8

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500-hPa Height Anomaly CorrelationFIM-30km vs.

GFS T574 (27km) NCEP operational

SH, dieoffJun12 – May13

12‐month NWP testAugust 2012 ‐July 2013

NH, dieoffFIM minus GFSAug 12 – Jul 13

SH, dieoffFIM minus GFSAug 12 – Jul 13

95% stat signif diff

2d 4d 6d 8d 10d 2d 4d 6d 8d 10dFIM better skill than GFS for 5+ day duration in N. Hemisphere, 4+ day duration for S. Hemisphere, statistically significant in both SH and NH

3-year (2010-2012) 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 (2012-13)

12h 24h 36h 48h 72h 96h 120h

15km FIM forecast (θ-σ vert coord)21-26 October 2010Record extratropical SLP over US(958 hPa – Minnesota – 26 Oct 10)

Typhoon Megi – Oct 2010Extratropical transition leading to Pac/NA block

via Rossby wave breaking over Pacific

Dynamic tropopause:Potential temp on potential vorticity=2 surface

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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 month12

Resolution experiments on blocking (Tibaldi-Molteni)2009 Blocking Frequency from NCEP Reanalysis (black) and 3-mem FIM AMIP forecast ensembles (color – red, green, blue)30km 60km 120km 240km

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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/monMar 2012

Mean 500z anomalyMar 2012

Monthly % of 500 hPa height anomaly days- 3 FIM-30km 1-yr AMIP runs started on consecutive days

Average of 3 runsRun 1 Run 2 Run 3

Dec

Jan

Feb

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NCEP Reanalysis: 500 hPa: Percentage of Anomaly Days Dec08-Nov09

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Dec

Jan

Feb

Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- 3 FIM 1-yr AMIP runs - DJF30km 60km 120km 240km Obs

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Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- 3 FIM 1-yr AMIP runs - MAM

Mar

Apr

May

30km 60km 120km 240km Obs

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Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- 3 FIM 1-yr AMIP runs - JJA30km 60km 120km 240km Obs

Jun

Jul

Aug

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Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- 3 FIM 1-yr AMIP runs - SON30km 60km 120km 240km Obs

Sep

Oct

Nov

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θ-σ

σ-p

Feb

Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- θ-σ vs. σ-p FIM 1-yr AMIP runs - December30km 60km 120km 240km Obs

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Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- θ-σ vs. σ-p FIM 1-yr AMIP runs – Jan 200930km 60km 120km 240km Obs

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θ-σ

σ-p

Feb

θ-σ

σ-p

Feb

Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- θ-σ vs. σ-p FIM 1-yr AMIP runs – Feb 200930km 60km 120km 240km Obs

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Mar

Apr

May

θ-σ30km 60 120 240 30km 60 120 240 Obs

Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- θ-σ vs. σ-p FIM 1-yr AMIP runs – MAM

σ-p

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θ-σ30km 60 120 240 30km 60 120 240 Obs

Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- θ-σ vs. σ-p FIM 1-yr AMIP runs – JJAσ-p

Jun

Jul

Aug

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θ-σ30km 60 120 240 30km 60 120 240 Obs

Monthly % of 500 hPa height anomaly days(relative to 30-year mean from Reanalysis)

- θ-σ vs. σ-p FIM 1-yr AMIP runs – SON

σ-p

Sep

Oct

Nov

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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 quasi‐horizontal 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 10‐20 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

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