1. 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) Climate Implications of Frontal Scale Air-Sea Interaction (August 5-7, 2013 / NCAR) Support from the NASA Physical Oceanography Program is gratefully acknowledged.

2. Meridional heat transport by ocean and atmosphere Large heat is handed over to the atmosphere from ocean near the western boundary current regions Trenberth and Caron (2001)

3. 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)

4. 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 ( ) and latent ( ) for each time scale.  Climatological mean and interannual standard deviation.

5. 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 ]

6. JFM mean northward heat flux by transient eddies (1) (sensible+latent, vertically integrated from surface to 50 hPa) Synoptic (2-8 days) Mean WBC positions:  Gulf Stream /  Kuroshio Extension /  Oyashio Extension (from Joyce et al. 2009 & Frankignoul et al. 2011) Contour Interval : 2  10 7 W m -1 Intra-seasonal (8-90 days)

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

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

9. Lateral divergence of transient eddy heat fluxes (3)( Vertically integrated climatological mean for JFM) SynopticIntra-seasonalSynoptic+Intra-seasonal Black contours: SST isotherms for 6, 8, 10  C

10. Interannual standard deviation of JFM lateral divergence of heat flux by transient eddies (3) SynopticIntra-seasonalSynoptic+Intra-seasonal

11. Northward heat transport by synoptic transient eddies regressed on the GSI, KEI, OEI GSIKEIOEI Bjerknes Compensation or Coupled Oscillation?

12. 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 and interannual 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.

13. Thank you

14. Regression of intra-seasonal daily 850 hPa variables on 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  10 6 W m -2 )  = H regression (C.I. 10m / gray: negative ) Red: positive regressions / Blue: negative regressions

15. Regression of intra-seasonal daily 850 hPa variables on 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  10 6 W m -2 )  = H regression (C.I. 10m / gray: negative ) Red: positive regressions / Blue: negative regressions

16. Indices for the meridional position of the Gulf 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)

17. Interannual standard deviation of JFM northward heat fluxes by transient eddies (1) SynopticIntra-seasonal Mean contour interval: 4  10 7 W m -1