Near Kuroshio and its extension Positive SST-Wind Correlation

1. 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 ℃ 17 18 19 20 21 22 23 24 25 26 27 Shoyo-Maru Summary • Winter • Surface stability (SST-SAT) exerts a strong control over surface heat flux, MBL height, and vertical wind shear. • With a small sample size (96 soundings), atmospheric advection dominates stability variations, but the maximum turbulent heat flux is observed in a warm meander of the KE front, with a mixed layer more than 2 km deep. • Summer • Clear transition is observed in the marine boundary layer across the Kuroshio Extension front along 35-36N. A primary inversion at 1 km. • Near the front, fog tends to form under southerly conditions (warm advection) while stratocumulus with elevated cloud base under northerly cold advection. • Future cruises: winter (1/12-26/2006) and summer (around 05-06/2006) Near Kuroshio and its extension PositiveSST-Wind Correlation along 37oN 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. Summer Climate 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] Ocean-to-atmos. feedback COADS Cloudiness in June TMI SST QL+QS = 864 W/m2 LINE-I Meiyu/Baiu front 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 Wind 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. LINE-J Nonaka & Xie (2003, JC) Summer Cruise Winter Cruises 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 xie@hawaii.edu for more information. References 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. Composite Transect Typical Soundings Role of cross-frontal advection 8090939598 % Northernmost Stratus cloud capped by a primary inversion Composite Profiles Sounding stationswith SST & wind speed #72(7/04,18:34) Relative HUMIDITY (color), TEMPERATAURE (contour) & CLOUD BASE (red dots) LINE-J LINE-I Kaiyo-maru (2/24 - 3/17/2004) • Unstable MBL develops deep in height with weak wind shear in the vertical. Stronger surface winds due to enhanced vertical mixing. • Stable MBL is strongly stratified with large wind shear in the vertical. Winds above the frictional surface layer are considerably stronger than in an unstable MBL. Surface stability SST – SAT ≤ 1 oC SST – SAT ≥ 5 oC 1< SST – SAT < 5 oC Shoyo-maru (12/18/2003 - 1/8/2004) SST Southernmost #6(6/18, 17:32) Fog capped by a surface inversion T SST - SAT Td V • Southerly warm advection • stable surface layer  fog • Northerly cold advection • unstable MBL  elevated stratocumulus 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