Climate Implications of Frontal Scale Air-Sea Interaction
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Climate Implications of Frontal Scale Air-Sea Interaction (August 5-7, 2013 / NCAR). Northern Hemisphere Atmospheric Transient Eddy Fluxes and their Co-variability with the Gulf Stream and Kuroshio-Oyashio Extensions. Young-Oh Kwon and Terrence M. Joyce

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Climate Implications of Frontal Scale Air-Sea Interaction

(August 5-7, 2013 / NCAR)

Northern Hemisphere Atmospheric Transient Eddy Fluxes and their Co-variability with the Gulf Stream and Kuroshio-Oyashio Extensions

Young-Oh Kwon and Terrence M. Joyce

(Woods Hole Oceanographic Institution)

Support from the NASA Physical Oceanography Program

is gratefully acknowledged.


Meridional heat transport by ocean and atmosphere
Meridional heat transport by ocean and atmosphere

Trenberth and Caron (2001)

Large heat is handed over to the atmosphere from ocean near the western boundary current regions


Data atmospheric transient eddy heat fluxes
Data: atmospheric transient eddy heat fluxes

  • Source:

    NASA MERRA (Modern Era Retrospective-analysis for Research and Applications)

  • Period and temporal resolution:

    Daily mean for 1979-2009 (31 years)

  • Season: Winter (JFM:all the analysis shown here is for the winter only!)

  • Spatial domain and resolution:

    1/2lat  2/3long in the Northern Hemisphere only.

  • Levels:

    Sea-level, 850 hPa, 500 hPa, 250 hPa, 200 hPa, and 100 hPa

  • Variables:

    Winds (u, v), temperature (T), and specific humidity (q)


Calculation atmospheric transient eddy heat fluxes
Calculation: atmospheric transient eddy heat fluxes

(1) Two time scales: synoptic (2-8days)and intra-seasonal (8days-3months)

 Daily variables for each winter (e.g. JFM 1979) at each level

(2) Covariances: for each winter (JFM) and for the two time scales:

Synoptic

transient eddy flux

Intra-seasonal transient eddy flux

(3) 31-yr time-series: sensible (<vT>) and latent (<vq>) for each time scale.

 Climatological mean and interannual standard deviation.


Variables examined
Variables examined

(1) Northward heat flux by transient eddies

(Vertically integrated from the surface to 50 hPa)

= [unit: W m-1]

(2) Northward heat transport by transient eddies

(Vertically and zonally integrated)

= [unit: PW]

(3) Lateral divergence of vertically integrated eddy heat fluxes

= [W m-2]


JFM mean northward heat flux by transient eddies (1)(sensible+latent, vertically integrated from surface to 50 hPa)

Synoptic (2-8 days)

Intra-seasonal (8-90 days)

Contour Interval : 2  107 W m-1

Mean WBC positions:  Gulf Stream /  Kuroshio Extension /  Oyashio Extension

(from Joyce et al. 2009 & Frankignoul et al. 2011)


Vertical structures of northward heat flux by transient eddies average over a zonal band in 30 50 n
Vertical structures of northward heat flux by transient eddies (Average over a zonal band in 30-50N)


Zonally integrated northward heat transport by transient eddies (2) (Climatological JFM mean and interannual standard deviation)


Lateral divergence of transient eddy heat fluxes (3)(Vertically integrated climatological mean for JFM)

Synoptic

Intra-seasonal

Synoptic+Intra-seasonal

Black contours: SST isotherms for 6, 8, 10C


Interannual standard deviation of jfm lateral divergence of heat flux by transient eddies 3
Interannual standard deviation of JFM lateral divergence of heat flux by transient eddies (3)

Synoptic

Intra-seasonal

Synoptic+Intra-seasonal


Northward heat transport by synoptic transient eddies regressed on the gsi kei oei
Northward heat transport by synoptic transient eddiesregressed on the GSI, KEI, OEI

GSI

KEI

OEI

BjerknesCompensation or Coupled Oscillation?


Summary
Summary

  • Synoptic and intra-seasonal time scales contribute comparably to the zonally integrated northward heat transport by transient eddies, though with very distinct spatial patterns.

  • Lateral divergence of transient eddy heat fluxes : synoptic+intra-seasonal mean distribution andinterannual variability are remarkably coincident with the ocean fronts.

  • Greater than 50% of the interannual variance of the winter northward heat flux and transport by transient eddies in the synoptic bands are correlated with interannual variability for the positions of the KE, OE and GS as the forcing as well as the response to the ocean front changes.



Regression of intra-seasonal daily 850 hPa variableson the Pacific-North America (PNA) teleconnection index

v regression

(C.I.= 0.5 m s-1)

T regression

(C.I.=0.5 K)

v regression  T regression

(C.I.=0.5  106 W m-2)

 =

H regression

(C.I. 10m / gray: negative )

Red: positive regressions / Blue: negative regressions


Regression of intra seasonal daily 850 hpa variables on the arctic oscillation ao index
Regression of intra-seasonal daily 850 hPa variableson the Arctic Oscillation (AO) index

v regression

(C.I.= 0.5 m s-1)

T regression

(C.I.=0.5 K)

v regression  T regression

(C.I.=0.5  106 W m-2)

 =

H regression

(C.I. 10m / gray: negative )

Red: positive regressions / Blue: negative regressions


Indices for the meridional position of the gulf stream kuroshio extension oyashio extension
Indices for the meridional position of theGulf Stream, Kuroshio Extension & Oyashio Extension

Gulf Stream Index: 15C at 200 m (1954-2006; Joyce et al. 2000)

Kuroshio Extension Index: 14C at 200 m (1980-2006; Joyce et al. 2009)

Oyashio Extension Index: maximum dSST/dy based on 1/4 SST (1983-2007; Frankignoul et al. 2011)


Interannual standard deviation of jfm northward heat fluxes by transient eddies 1
Interannual standard deviation of JFM northward heat fluxes by transient eddies (1)

Synoptic

Intra-seasonal

Mean contour interval: 4  107 W m-1


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