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