HR: 1330h
AN: A42B-0761    [PDF]
TI: On the Low-frequency North Pacific Climate Modulations Induced by the Mid-latitude Mixed Layer Heat Flux Convergence Anomalies.
AU: * Yulaeva, E
EM: eyulaeva@ucsd.edu
AF: Climate Research Division, Scripps Institution of Oceanography, Climate Research Division, SIO, UCSD, Mail Stop 0224,, La Jolla, CA 92093-0224 United States
AU: Schneider, N
EM: nschneid@hawaii.edu
AF: School of Ocean & Earth Science & Technology, International Pacific Research Center, University of Hawaii, Honolulu, HI 96822 United States
AB: In order to determine the role of the mid latitude mixed layer heat flux convergence anomalies in maintaining the observed low frequency climate variability we used the climate system that hindcasted anomalies of heat flux convergence of the tropical and North Pacific oceanic mixed layer and converted them into the northern hemisphere climate anomalies. The underlying philosophy states that North Pacific/North American climate anomalies on time scales of years to decades result from anomalous conditions in the Pacific equatorial upwelling regions, and the North Pacific Kuroshio-Oyashio extension (KOE), where anomalies in the ocean's thermocline are efficiently coupled to the surface. In response to this forcing, the coupled atmosphere - ocean mixed layer system adjusts and generates anomalies over the entire Pacific. We hindcasted the air-sea heat flux by forcing the ocean general circulation model (MIT OGCM) with the NCAR/NCEP reanalysis wind stress, while relaxing sea surface temperature (SST) and sea surface salinity (SSS) to their climatological values. The hindcasted monthly oceanic heat flux convergence anomalies for the period of January 1960 to December 1999 in the KOE region and in the tropical Pacific were then applied as anomalous forcing to the coupled CCM3/slab ocean (SOM) model. We performed a 40-year integration of the five-member ensemble of the CCM3/SOM forced with heat budget anomalies (the Delta Q forcing in the tropical Pacific and in the KOE region) obtained from the ocean hindcast. To identify the atmospheric response to the mid-latitude forcing and to validate the statistical analysis, we repeated the five-member CCM3/SOM ensemble integration, but applied the Delta Q forcing in the tropics only. We will discuss the differences between this integration and the corresponding CCM3/SOM integration with both tropical and KOE forcing. These differences indicate the effect of the KOE Delta Q forcing on the mean atmospheric state and on the pdf of the intrinsic atmospheric modes. As expected, the anomalous Delta Q forcing over the tropical Pacific sets the global anomalous climate patterns over North Pacific/North America. These patterns include the SST and air-sea heat flux anomalies over North Pacific. Over the KOE region the SST and heat flux anomalies are strongly correlated with the heat flux forcing of the tropical Pacific. However, when the KOE forcing is added, the relationship between the SST and air-sea heat flux anomalies changes. The air-to-sea heat flux anomalies over the KOE region are not correlated with the tropical heat flux anomalies. Our findings show that the mid-latitude forcing augments the teleconnection patterns from the tropics. In particular, it intensifies the regression patterns of the 500 mb geopotential height and surface pressure onto the tropical mixed layer heat flux convergence anomalies (though the anomalies themselves are identical in both cases). We will show the changes exhibited in the surface variables as well as in the free atmosphere. We will also discuss the changes in the storm tracks and the role of the transient eddy forcing in maintaining the mean atmospheric patterns.
UR: http://meteora.ucsd.edu/~yulaeva/CM/coupled.html
DE: 1620 Climate dynamics (3309)
DE: 3309 Climatology (1620)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4215 Climate and interannual variability (3309)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting