1. Variability of Winter Extreme Flux Events in the Kuroshio Extension and Gulf Stream Regions Xiaohui Ma 1,2, Ping Chang 1,2,3, R. Saravanan 3 1. Department of Oceanography, Texas A&M University, College Station, TX, US, 77843 2. Ocean University of China, College of Physical and Environmental Oceanography, Qingdao, China, 266100 3. Department of Atmospheric Sciences, Texas A&M University, College Station, TX, US, 77843 Climate Implications of Frontal Scale Air-Sea Interaction (FSASI) Workshop, Boulder, CO, 08/05-08/07,2013 Sponsored by NSF and DOE

2. Datasets: NCEP-CFSR: 1979-2009 NCEP-NCAR: 1948-2009 NOAA 20th Century Reanalysis: 1900-2010 Analysis Domain: Pac: [32°N 42°N], [140°E 160°E] Atl: [30°N 42°N], [70°W 50°W] Definition of Extreme Flux Event: daily (SHF,LHF) > 80 percentile value North PacificNorth Atlantic Shaman et al. (2010): The intraseasonal variability and long term trend of turbulent heat fluxes (THF) in the Gulf Stream extension (GSR) are determined by high flux events related with Cold air outbreaks (CAOs). total Non- event event

3. The average accumulated number of days of the high flux events, which typically last fewer than 3 days, occupies only less than 20% of the winter period, but contributes to more than 30% of the total sensible and latent heat fluxes during the entire winter season in both the Pacific and the Atlantic. In comparison with the Pacific, the extreme flux events in the Atlantic occur more frequently with stronger intensity and shorter duration. Statistics of Extreme Flux Events

4. Event-day composite PAC THF ATL THF PAC SAT & qATL SAT & q PAC SLP & WindsATL SLP & Winds The extreme flux events are characterized by CAOs with northerly wind that brings cold and dry air from the continent.

5. Contribution of Event-Day and Nonevent-Day THF to Total THF During Winter Total Event Non- event Correlation between total THF and event- day THF R>0.9 (95% Sig); Contributions of Var(event THF) to Var(total THF) are 80.0%, 85.2%, 84.8%, respectively PAC/KER THF

6. Total Event Non- event Contribution of Event-Day and Nonevent-Day THF to Total THF During Winter Atl/GSR THF Correlation between total THF and event- day THF R>0.9 (95% Sig); Contributions of Var(event THF) to Var(total THF) are 81.9%, 73.0%, 81.6%, respectively

7. Relationship Between Extreme THF and PDO SVD between extreme THF anomaly and SLP anomaly 1 st EOF of NDJFM SLP (PDO)Var(extreme THF)/Var(total THF) SVD SLP SVD THF

8. SVD between THF and v’v’ at 300hpaSVD between SLP and v’v’ at 300hpa SVD storm SVD THF SVD storm SVD SLP Relationship Between Storm Track and Extreme THF, PDO

9. Event-day and Nonevent-day Storms Propagation Extreme flux events Southeast propagation Storm track (south shift) PDO(+) Non- events Northeast propagation Storm track (north shift) PDO(-) Event Storms Non-event Storms

10. Conclusions and Discussions 1. Extreme flux events associated with synoptic-scale atmospheric CAOs are crucial to the total boreal winter turbulent surface heat fluxes in both the KER and GSR in intra-seasonal, inter-annual and long term time scale. 2. In the Pacific, decadal variations of extreme flux events show a close relationship to the PDO. In contrast, decadal variations of Atlantic extreme flux events is not related to the NAO (Shaman et al., 2010). 3. When extreme flux events occur in the KER, the associated storms tend to propagate southeastward, consistent with southward shift of the downstream storm track, corresponding to positive PDO phase. The causality among extreme flux events, storm track and PDO needs further investigation.

11. SST regressed on to PDO index SVD between extreme THF anomaly and SLP anomaly