Mesoscale variability in statistics
Computation of EKE
Using geostrophic current components, mesoscale variability can be measured by Eddy Kinetic Energy (EKE, cm²/s²):
EKE=1/2x(u²+v²)
EKE is commonly used as a key indicator of mesoscale variability, as high EKE values correspond to areas of intense activity (fig 5).
Seasonal SLA variations in the Kuroshio system
Several mean seasonal SLAs can be computed, respectively from January to March, April to June, July to September and October to December:
mean SLA=(1/n)x(Sum SLA(t))
This mean SLA represents the mean seasonal status of mesoscale structures in the Kuroshio and enables us to study variations from one period to another (fig 6).
Computation of RMS
Root Mean Square (RMS, fig 7) is given by:
RMS=[[Sum SLA(t)]/n]½
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fig 5: EKE, Kuroshio area, cm²/s²
 
 
fig 6: Seasonal variations of mean SLA for 2002, Kuroshio current, Winter, Spring, Summer, Autumn, cm
 
 
fig 7: Seasonal variations of MSLA RMS for 2002, Kuroshio current, Winter, Spring, Summer, Autumn, cm
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