Seasonal forecasts of the tropical cyclone activity in .Seasonal forecasts of the tropical cyclone

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  • Seasonal forecasts of the tropical cyclone activity in an ECMWF coupled operational prediction

    system

    Julia Manganello1, Kevin Hodges2 and the Minerva Project Team

    1 COLA, USA

    2 NERC Centre for Earth Observation, University of Reading, UK

    S2S Interna*onal Conference, Feb. 2014

  • ECMWF coupled ensemble systems (1)

    System atmosphere model cycle atmosphere

    spectral trunca2on atmosphere ver2cal

    levels ocean model ocean horizontal res, equatorial refinement

    ocean ver2cal levels

    MINERVA IFS cy 38r1 T319 / T639 / T1279 91 levels, top = 1 hPa NEMO v 3.0/3.1 1 degree, ~ 0.3 deg. Lat. 42 levels

    System 4 IFS cy 36r4 T255 91 levels, top = 1 hPa NEMO v 3.0/3.1 1 degree, ~ 0.3 deg. Lat. 42 levels

    EPS (previous) IFS cy 38r2

    T639 (d 0-10), T319 62 levels, top = 5 hPa NEMO v 3.0/3.1

    1 degree, ~ 0.3 deg. Lat. 42 levels

    ENS (current) IFS cy 40r1

    T639 (d 0-10), T319 91 levels, top = 1 hPa NEMO v 3.4

    1 degree, ~ 0.3 deg. Lat. 42 levels

    S2S Interna*onal Conference, Feb. 2014 Page 1

    Courtesy of Franco Molteni (ECMWF)

  • ECMWF coupled ensemble systems (2)

    System coupler

    2me range of ocean-

    atmosphere coupling

    coupling frequency

    unperturbed ini2al cond. for re-forecasts

    atmospheric perturba2ons

    ocean perturba2ons

    stochas2c model

    perturba2ons

    MINERVA OASIS-3 from start 3 hours ERA-Interim + ORA-S4 SV, EDA from 2011 dates

    5 ocean analyses + SST perturba*ons

    3-*mescale SPPT + KE backsca[er

    System 4 OASIS-3 from start 3 hours ERA-Interim + ORA-S4 SV 5 ocean analyses + SST perturba*ons

    3-*mescale SPPT + KE backsca[er

    EPS (previous) OASIS-3 from day 10 3 hours

    ERA-Interim + ORA-S4

    SV, EDA from current or recent date

    generated by ENS member fluxes during day 1 to 10

    2-*mescale SPPT + KE backsca[er

    ENS (current)

    sequen*al, single executable code

    from start 3 hours ERA-Interim + ORA-S4

    SV, EDA from current or recent date

    5 ocean analyses 2-*mescale SPPT + KE backsca[er

    ORA-S4 : Ocean Re-Analysis for ECMWF System-4 EDA : Ensemble of Data Assimila*ons (low-res 4D-var)

    SV : Singular Vectors of 48-hour linear propagator SPPT : Stochas*c Perturba*on of Physical Tendencies scheme

    S2S Interna*onal Conference, Feb. 2014 Page 2

    Courtesy of Franco Molteni (ECMWF)

  • Minerva Catalog: Base Experiments

    Resolu2on Start Dates Ensembles Length Period of Integra2on

    T319 (65 km) May 1, Nov 1 51 7 months 1980-2013

    T639 (32 km) May 1, Nov 1 15 7 months 1980-2013

    T1279 (16 km) May 1, Nov 1 15 7 months 2000-2013

    S2S Interna*onal Conference, Feb. 2014 Page 3

    For more information, please see a poster Project Minerva: Towards Seamless High-Resolution Climate Prediction by Ben Cash (COLA) Feb. 12 13, Session D

    May-November (MJJASON) mean tropical cyclone (TC) frequency and the accumulated cyclone energy (ACE);

    Northern Hemisphere: North Atlantic and the western North Pacific;

    Analysis periods are 2000-2011 and 1980-2011;

    OBS International Best Track Archive for Climate Stewardship (IBTrACS).

  • Tracking and Identification of TCs

    T1279

    T639

    T319

    1. Surface (10-m) wind speed threshold, m/s

    (intensity threshold)

    15.41

    14.41,2

    13.41,2

    2. Difference in vorticity3 between 850 hPa and 250 hPa

    (a warm core condition).

    larger than zero

    3. Vorticity3 max at each level (6 levels) between 850 hPa and 250 hPa (a coherent vertical structure condition).

    applied

    4. Number of consecutive time steps when criteria 1-3 are satisfied.

    4

    (24 hours)

    5. Cyclogenesis (first identification) occurs between 0-20N over land and 0-30N over oceans.

    applied

    2. TC Identification Criteria:

    1. Hodges Method for detection and tracking of tropical vortices:

    Relative vorticity max of 5x10-6 s-1 at T63 (relative vorticity is averaged over 850, 700 and 600-hPa before detection and tracking),

    Lifetime 2 days.

    1 Observed tropical storm threshold for 10-min max. sustained wind. U10min = 0.88 * U1min

    2 Surface speed threshold is further adjusted for model resolution.

    3 Vorticity is truncated at T319 (N160).

    IBTrACS data are filtered using criteria 1 and 4.

    S2S Interna*onal Conference, Feb. 2014 Page 4

  • RMS Error1 (wrt OBS mean in %) /

    Mean ensemble spread1

    TC Freq.

    ACE

    2000-2011

    IFS T1279

    0.77#

    0.60

    IFS T639

    0.86#

    0.71#

    IFS T319

    -0.18

    0.61#

    1980-2011

    IFS T639

    0.48#

    0.65#

    IFS T319

    -0.37

    0.43#

    Genesis (2000-2011)

    North Atlantic

    Correlation with OBS

    TC Freq.

    ACE

    2000-2011

    IFS T1279

    2.85 (22.2%) / 3.40

    39.9 (34.2%) / 39.1

    IFS T639

    2.66 (20.8%) / 3.21

    35.9 (30.8%) / 40.9

    IFS T319

    4.51 (35.1%) / 3.43

    42.0 (36.1%) / 38.6

    1980-2011

    IFS T639

    3.76 (37.7%) / 2.72

    43.4 (48.7%) / 33.2

    IFS T319

    4.77 (47.8%) / 2.92

    51.3 (57.6%) / 30.3

    OBS

    T1279

    T639

    T319

    mean=12.8

    mean=10.7

    mean=9.8

    mean=11.5

    # (bold) - statistical significance at the 95% (90%) confidence level.

    1 - after mean bias correction

    S2S Interna*onal Conference, Feb. 2014 Page 5

  • RMS Error1 (wrt OBS mean in %) /

    Mean ensemble spread1

    TC Freq.

    ACE

    2000-2011

    IFS T1279

    0.56

    0.69#

    IFS T639

    0.70#

    0.84#

    IFS T319

    0.75#

    0.70#

    1980-2011

    IFS T639

    0.46#

    0.76#

    IFS T319

    0.52#

    0.68#

    Genesis (2000-2011)

    Western North Pacific

    Correlation with OBS

    TC Freq.

    ACE

    2000-2011

    IFS T1279

    2.36 (11.5%) / 3.46

    34.9 (18.9%) / 40.4

    IFS T639

    2.01 (9.8%) / 3.31

    28.4 (15.4%) / 35.4

    IFS T319

    1.88 (9.2%) / 3.37

    35.5 (19.2%) / 32.2

    1980-2011

    IFS T639

    3.41 (15.2%) / 3.45

    43.2 (20.9%) / 40.2

    IFS T319

    3.27 (14.5%) / 3.68

    47.9 (23.2%) / 35.2

    OBS

    T1279

    T639

    T319

    mean=20.4

    mean=26.3#

    mean=28.9#

    mean=30.1#

    S2S Interna*onal Conference, Feb. 2014 Page 6

    # (bold) - statistical significance at the 95% (90%) confidence level.

    1 - after mean bias correction

  • TC frequency (North Atlantic, 1980-2011)

    IBTrACS T639 (bias-corrected)

    T639

    r = 0.48

    25-75 percentile

    10-90 percentile

    r = -0.28

    r = 0.74

    r = 0.86

    Corr.:

    0.48

    RMSE:

    3.76

    SPRD:

    2.72

    Ratio:

    1.38

    S2S Interna*onal Conference, Feb. 2014 Page 7

  • ACE (North Atlantic, 1980-2011)

    r = 0.65

    r = 0.34

    r = 0.79

    r = 0.71

    IBTrACS T639 (bias-corrected)

    T639

    25-75 percentile

    10-90 percentile

    Corr.:

    0.65

    RMSE:

    43.4

    SPRD:

    33.2

    Ratio:

    1.31

    S2S Interna*onal Conference, Feb. 2014 Page 8

  • Biases wrt ERA-Interim (2000-2010)

    VWS

    SST OBS

    T1279

    T639

    T319

    Genesis (2000-2011)

    Mid-trop.

    RH

    500-hPa

    Neg. Omega

    S2S Interna*onal Conference, Feb. 2014 Page 9

    mean=12.8

    mean=10.7

    mean=9.8

    mean=11.5

  • North Atlantic T639 Biases wrt ERA-I (1980-2010)

    (TC frequency)

    (SSTMDR SSTGlobTrop)

    -1.0*(VWSMDR)

    Time series smoothed, mean bias subtracted

    OBS

    T639

    SSTMDR SSTGlobTrop

    0.66#

    0.86#

    -1.0*VWSMDR

    0.65#

    0.87#

    Correlation of the TC frequency with climatological indices

    MDR (80W-20W, 7.5N-22.5N)

    Bias

    Corr.

    w/ ERA-I

    Trend*

    T639

    ERA-I

    SSTMDR

    -0.12 C

    0.86#

    0.13#

    0.16#

    SSTGlobTrop

    -0.22 C

    0.84#

    0.086#

    0.076#

    SSTMDR SSTGlobTrop

    0.10C

    0.83#

    0.045

    0.086

    VWSMDR

    -0.38 m/s

    0.69#

    -0.082

    -0.52

    * Units are C/decade and m/s/decade

    - statistical significance at the 95% confidence level.

    Comparison of T639 climatological indices with ERA-I

    S2S Interna*onal Conference, Feb. 2014 Page 10

  • TC frequency (Western North Pacific, 1980-2011)

    IBTrACS T639 (bias-corrected)

    T639

    25-75 percentile

    10-90 percentile

    r = 0.46

    r = 0.22

    r = 0.54

    r = 0.70

    Corr.:

    0.46

    RMSE:

    3.41

    SPRD:

    3.45

    Ratio:

    0.99

    S2S Interna*onal Conference, Feb. 2014 Page 11

  • ACE (Western North Pacific, 1980-2011)

    IBTrACS T639 (bias-corrected)

    T639

    25-75 percentile

    10-90 percentile

    r = 0.76

    r = 0.52

    r = 0.85

    r = 0.84

    Corr.:

    0.76

    RMSE:

    43.2

    SPRD:

    40.2

    Ratio:

    1.07

    S2S Interna*onal Conference, Feb. 2014 Page 12

  • Summary and Conclusions

    Overall, the forecast skill of the seasonal mean TC frequency and the ACE in Minerva can be considered as good, particularly for the western North Pacific basin.

    The largest errors in the North Atlantic are associated with the inability of the model to reproduce decadal scale cha