Variability of Winter Extreme Flux Events in the Kuroshio Extension

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

Climate Implications of Frontal Scale Air-Sea Interaction (FSASI) Workshop, Boulder, CO, 08/05-08/07,2013

Sponsored by NSF and DOE

Datasets:NCEP-CFSR: 1979-2009NCEP-NCAR: 1948-2009NOAA 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 Pacific North 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

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

Event-day compositePAC THF ATL THF

PAC SAT & q ATL SAT & q

PAC SLP & Winds ATL SLP & Winds

The extreme flux events are characterized by CAOs with northerly wind that brings cold and dry air from the continent.

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

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

Relationship Between Extreme THF and PDOSVD between extreme THF anomaly and SLP anomaly

1st EOF of NDJFM SLP (PDO)Var(extreme THF)/Var(total THF)

SVDSLP

SVDTHF

SVD between THF and v’v’ at 300hpa SVD between SLP and v’v’ at 300hpa

SVD storm

SVD THF

SVDstorm

SVDSLP

Relationship Between Storm Track and Extreme THF, PDO

Event-day and Nonevent-day Storms Propagation

Extreme fluxevents

Southeastpropagation

Storm track(south shift)PDO(+)

Non-events

Northeastpropagation

Storm track(north shift)PDO(-)

Event Storms

Non-event Storms

？

？

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.

SST regressed on to PDO index

SVD between extreme THF anomaly and SLP anomaly