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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. ℃.

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slide1

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 [email protected] 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

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