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Singular Vectors - SV

The Singular Vector(SV) technique seeks perturbations for wind, temperature and pressure that will maximize their impact on a 48 hour forecast as measured by the total energy over the hemisphere outside the tropics.  This maximization does not mean that SVs only intensify weather systems; just as often they weaken or displace them.

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• Average SV total energy charts can be used to identify unstable regions. 
• SV perturbations tend to be localized in areas of strong barotropic and baroclinic instability.
• SV growth tends to be characterized during the model run by:
  • an upscale energy transfer.
  • an upward energy transfer (most rapid for smaller scales).
  • initial potential energy being converted into kinetic energy.
• Information for the final-time synoptic-scale structure is contained in the sub-synoptic scale SVs.  At initial time:
  
  • SVs with sub-synoptic scale wave numbers may grow very rapidly to reach synoptic scales.
    
  • SVs with large scale wave numbers grow much more slowly than unconstrained, smaller-scale perturbations.  The presence or absence of large scales has little effect on SV growth. 
• The atmospheric flow structure in winter tends to be more baroclinically unstable than in summer.  During winter the flow over Pacific and Atlantic sectors is on average more unstable than in other regions.

Additional Sources of Information

(Note: In older material there may be references to issues that have subsequently been addressed)

• Read more about quantifying forecast uncertainty.
• Read more on singular vectors.
• Read more on tropical singular vectors.

(FUG Associated with Cy49r1)