7/11,6:00 ～ 7/12,18:00,2005 （ LINE-I ）. 38N. Meiyu front. 37N. 36N. 35N. 34N. 33N. 136E. 138E. 140E. 142E. 144E. 146E. 148E. 7/13,6:00 ～ 7/14,12:00,2005 （ LINE-J ）. 38N. 37N. 36N. 35N. Meiyu front. 34N. 33N. 136E. 138E. 140E. 142E. 144E. 146E. 148E. 150E. 10m/s. ℃.
Near Kuroshio and its extension
The Kuroshio Extension (KE) is an inertial jet originated from the Kuroshio, the western boundary current of the subtropical gyre. It transports and releases large amounts of heat to the atmosphere, forming a strong sea surface temperature (SST) front. The KE displays large decadal variability in response to basin-scale changes in wind. The deep ocean mixed layer in winter near the KE enables ocean subsurface anomalies, often remotely forced, to affect SST variability.
The KE front may help intensify atmospheric baroclinicity and thereby maintain the North Pacific storm track. Recent satellite observations show that surface wind speed increases over the KE’s warm meanders while decreasing over detached cold eddies, a relationship indicative of an ocean-to-atmospheric influence.
Extensive low-cloud deck over the subpolar North Pacific. Cloud variability in its southern edge along the KE has been shown to interact with summer SST.
SAT [color]、SURFACE WIND [vector],
Stations [green dots]
COADS Cloudiness in June
QL+QS = 864 W/m2
Large undulations in MBL height from virtually 0 m to 2 km, in response to variations in surface stability. The strongest ocean heat flux (>800 W/m2) and deepest MBL (>2 km) are observed in a warm meander of the KE front around 152E, 37N
The SST front south of the recirculation remains strong in June but weakens rapidly toward July.
Fog was observed in KESS soundings around June 18.
Nonaka & Xie (2003, JC)
Scatter plots of surface stability, MBL Height, surface heat flux, and meridional wind
Acknowledgments. This work is supported by NASA, NSF, JSPS, JAMSTEC, and Japan Fisheries Research Agency.
We have carried out the first joint ocean-atmospheric sounding surveys onboard Japan Fisheries Agency research vessels during the 2003-04 winter, launching a total of 96 Global Positioning System (GPS) sondes to observe the KE’s influence on atmospheric marine boundary layer (MBL).
Contact [email protected] for more information.
Nonaka, M. and S.-P. Xie, 2003: Co-variations of sea surface temperature and wind over the Kuroshio and its extension: Evidence for ocean-to-atmospheric feedback. J. Climate, 16, 1404-1413.
Tokinaga, H., Y. Tanimoto, M. Nonaka, B. Taguchi, T. Fukamachi, S.-P. Xie, H. Nakamura, T. Watanabe, and I. Yasuda, 2006: Atmospheric sounding over the winter Kuroshio Extension: Effect of surface stability on atmospheric boundary layer structure. Geophys. Res. Lett., 33, doi: 10.1029/2005GL025102.
Xie, S.-P., 2004: Satellite observations of cool ocean-atmosphere interaction. Bull. Amer. Meteor. Soc., 85, 195-208.
R/V Roger Revelle
The Kuroshio Extension maintains a strong SST front along 35-36N in the 2005 summer. R/V Revelle cruised across the KE front eight times during June 17-July 17, 2005 as part of the CLIVAR Kuroshio Extension System Study (KESS). A total of 116 GPS sondes were launched, along with ocean hydrographic observations.
Because of short cruise durations, surface stability is largely controlled by cross-SST frontal advection by atmospheric synoptic disturbances.
Role of cross-frontal advection
Stratus cloud capped by a primary inversion
Sounding stationswith SST & wind speed
Relative HUMIDITY (color), TEMPERATAURE (contour) &
CLOUD BASE (red dots)
Kaiyo-maru (2/24 - 3/17/2004)
SST – SAT ≤ 1 oC
SST – SAT ≥ 5 oC
1< SST – SAT < 5 oC
Shoyo-maru (12/18/2003 - 1/8/2004)
Fog capped by a surface inversion
SST - SAT
In-situ Observations of Kuroshio Extension's Influence on the Atmosphere
Shang-Ping Xie1,Y. Tanimoto2, H. Tokinaga3, B. Taguchi1, K. Kai2, M. Nonaka3, H. Nakamura4, and T. Watanabe5
1 University of Hawaii, USA 2 Hokkaido University, Japan 3 Japan Agency for Ocean-Earth Science and Technology, Japan
4 University of Tokyo, Japan 5 Fisheries Research Agency, Japan