Intensive observations over the Kuroshio Extension front in the Baiu season
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Intensive observations over the Kuroshio Extension front
in the Baiu season
Yoshimi Kawai (JAMSTEC)& Y. Tachibana, T. Miyama, A. Manda, S. Iizuka, M. Yoshioka,
H. Nakamura10:05-10:25, 5 Aug. 2013
Frontal Scale Air-Sea Interaction Workshop
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Unique Observations in Our Project1) Three-vessel simultaneous observations across
the KE front in the Baiu/Meiyu Season of 2012
2) Intensive observations across the Subarctic front in April 2013
3) Aircraft-vessel simultaneous observations across the KE front in July 2013
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Why three vessels?• We need to clearly separate spatial distribution
across the front from temporal variations
Why Baiu/Meiyu season?• Relatively calm (if not, we have to escape!)
• Response of low clouds on the SST front• Is the atmospheric response on SST really weak in
summer?
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Simultaneous observations (2-6 July)
Seisui-maru
Wakataka-maru
Tansei-maru
Microwave OISST by RSS
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Tansei-maru
Wakataka-maru
Seisui-maru
Radiosonde diagram
Every 2 hours
4hr
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• Calm condition throughout the observation period• It rained on 2 and 4 July
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L
L
Surface wind speed
Surface Air Temp. (SAT)
Meridional wind speed
northerly
southerly
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Latent heat flux and distance from the SST front
South North
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11:00-15:00, 2 July (JST) 03:00-07:00, 3 July (JST)
Cloud base height 03:00-15:00, 3 July
Color: Relative humidity (%)Dot: cloud base height
L
15:00-19:00, 2 July (JST)
Tanimoto et al. (2009)
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Model experimentsControl
Smoothed SST
JCOPE2SST
Obs.
Smoothed JCOPE2
JCOPE2: 3D-VAR ocean reanalysis, 1/12º (by Dr. Miyazawa, JAMSTEC)
on 3 July 2012
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NOAA OISST v.2 Observation
JMA MGDSST JCOPE2 Reanalysis
143ºE SST
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WRF, nestingBy Dr. Manda
IPRC-RAMBy Dr. Miyama
Cloud Liquid Water in CTL
Red dot: observed cloud base height
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SST Smoothed
SST smoothed → cloud height lowered south of the front
Smoothed – Control IPRC-RAMBy Dr. Miyama
WRF, nestingBy Dr. Manda
Cloud Liquid Water
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Reference height = 400m
Mean PVT during 0300-1900 on 3 July
ps ps’
Δp =
p s’-p s
0.3 hPa
pref = pref
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Summary• We successfully observed fine structure of SST, air
temperature, and cloud base height across the KE front• Turbulent heat flux showed clear meridional contrast, the
maximum around 50 km away from the front.• Slope structure of cloud base height was observed • Regional models successfully simulated the slope
structure of cloud base height across the front• Smoothed SST lowered cloud base height on the southern
side, and reduced the gradient of cloud base• Direct effect of the front was limited within about 500 m
height • Contribution of the differential heating to SLP was about
0.3 hPa in this case
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For future studies• Does the horizontal difference in SLP of a few tenths
hPa significantly affect synoptic-scale phenomena? • Can we capture evidence of the deep heating
(Minobe et al., 2010) over the Kuroshio/KE by in situ observations?
• Is the existing OI (or 3D-Var) SST enough for simulating frontal-scale atmospheric phenomena?
• Model results depends on types of SST and lateral boundary condition