Assessment of the NCEP CFS Hindcast Runs on Predicting by ito20106

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									 Assessment of the NCEP CFS
Hindcast Runs on Predicting the
   North American Monsoon
       Lindsey Long and Jae Schemm
           NOAA/NWS/NCEP/CPC
       Lindsey.N.Williams@noaa.gov

      Runs courtesy of Suranjana Saha
          NOAA/NWS/NCEP/EMC
                   Introduction
   Focus on Precipitation and Atmospheric
    Circulation
   Look at both seasonal and interannual
    variability
   Five varying runs allow us to look at the
    affect of:
       Lead Time
       Updates to the CFS model
       Horizontal Resolution
               Description of Runs
   5 different hindcast runs from 1981-2006
   Two 15-member ensemble mean hindcasts
    from current operational CFS
       1-month lead (May)
       3-month lead (March)
   Three single runs with differing horizontal
    resolutions using an updated CFS
       T62
       T126
       T382
            Summary of Runs
Run    CFS Version      Resolution    Initial    # of Runs
                                     Condition
 1    GFS 2007 / MOM3     T382       May 15th      Single

 2    GFS 2007 / MOM3     T126       May 15th      Single

 3    GFS 2007 / MOM3      T62       May 15th      Single

 4     Operational         T62         May       15-Member
                                                  Ensemble
                                                    Mean
 5     Operational         T62        March      15-Member
                                                  Ensemble
                                                    Mean
        Complex Terrain
Demonstrates the need for finer horizontal resolution




  Baja
California
                                         Gulf of
  Gulf of                                Mexico
 California


              Sierra Madre
               Occidental
                  NAME Sub Regions

   Arizona/New
    Mexico Region
    (AZNM) ;
    (Higgins et al.                  TIER 1.5
    1998)                            CORE

   CORE Region                      AZNM
    (Gutzler 2004)
   Tier 1.5
    Region
    (NAMAP2)
        CFS JJAS Precipitation [cm], 1981-2006
URD (1x1)                T382                    T126




  T62              Oper T62 May Ensm    Oper T62 March Ensm
CFS JJAS Precipitation Model Minus Obs [cm], 1981-2006
 URD (1x1)              T382                  T126




   T62            Oper T62 May Ensm    Oper T62 March Ensm
Seasonal Cycle
                          a) AZNM




of Precipitation
   CORE Region shows
    good example of
                          b) CORE


    increased accuracy
    with resolution and
    model upgrade
   TIER 1.5 shows less
    improvement with      c) TIER 1.5
    new model runs




                                URD     T382   T126   T62   T62    T62
                                                            May   March
Seasonal Cycle
                           a) AZNM




of Precipitation
   CORE Region shows
    good example of
                           b) CORE


    increased accuracy
    with resolution and
    model upgrade
   TIER 1.5 shows less
    improvement with       c) TIER 1.5
    new model runs
   In all regions, T382
    run does well
    capturing monsoon
    onset (June-July)

                                 URD     T382   T126   T62   T62    T62
                                                             May   March
CFS Diurnal Cycle of Precipitation JJAS (mm/day)
 South East         Great Plains            Mountain




  AZNM        l        CORE


                                      T62
                                      T126
                                      T382
                                      NARR
Interannual
                    a) AZNM




 Variability
                    b) CORE


   Anomalous
    Precipitation
    for JJAS
                    c) TIER 1.5




                              URD   T382   T126   T62   T62    T62
                                                        May   March
Interannual
                    a) AZNM




 Variability
                    b) CORE


   Anomalous
    Precipitation
    for JJAS
   Decadal Trend   c) TIER 1.5

    present in
    observations
    and CFS

                              URD   T382   T126   T62   T62    T62
                                                        May   March
                      Precipitation Correlations to URD
a) AZNM Monthly                            d) AZNM Seasonal




b) CORE Monthly                            e) CORE Seasonal




c) TIER 1.5 Monthly                        f) TIER 1.5 Seasonal




                      T382   T126    T62     T62         T62
                                             May        March
            Atmospheric Circulation

   Prominent upper-air features in the NAME
    region:
       Anticyclonic flow over the region
       Low-level jet over the Gulf of Mexico
       Low-level jet over the Gulf of California
Atmospheric Circulation (JJA)
         300 mb Streamlines, 850 mb Wind Vectors
  NARR                   T382                 T126




   T62             Oper T62 May Ensm   Oper T62 March Ensm
Atmospheric Circulation (JAS)
         300 mb Streamlines, 850 mb Wind Vectors
   NARR                  T382                 T126




   T62             Oper T62 May Ensm   Oper T62 March Ensm
Gulf of California LLJ, 850 mb Winds
  Strong Southerly Flow   Weak Westerly Flow
          NARR                   T382
                       Conclusions
   As expected with the complex terrain of the NAMS,
    increased resolution does improve the precipitation
    forecast.
       Correlations show Interannual Variability is improving with
        resolution
       Improvement also seen at the Seasonal and Diurnal time scales.

   Comparisons of the T62 runs highlight the improvement
    provided by the updated atmospheric GCM model.

   Change in lead time for Ensemble Mean hindcasts show
    only a slight improvement in May versus March

   The general circulation is still a problem area.
       Missing anticyclonic flow over the monsoon area
       Lacking the southerly flow associated with the LLJ; therefore,
        the warm moisture brought into the region by this jet is missing.
Thank you!

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