Variability of Winter Extreme Flux Events in the Kuroshio Extension and Gulf Stream Regions

1. Variability of Winter Extreme Flux Events in the KuroshioExtension and Gulf Stream Regions Xiaohui Ma1,2, Ping Chang1,2,3, R. Saravanan3 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 Sponsored by NSF and DOE Climate Implications of Frontal Scale Air-Sea Interaction (FSASI) Workshop, Boulder, CO, 08/05-08/07,2013

2. North Pacific North Atlantic total 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). Non-event 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] event Definition of Extreme Flux Event: daily (SHF,LHF) > 80 percentile value

3. Statistics of Extreme Flux Events 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 withthe Pacific, the extreme flux events in the Atlantic occur more frequently with stronger intensity and shorter duration.

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

5. Contribution of Event-Day and Nonevent-Day THF to Total THF During Winter PAC/KER THF 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 Total Non-event Event

6. 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) are81.9%, 73.0%, 81.6% , respectively Total Non-event Event

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

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

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

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, decadalvariationsof 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