Convection process in the North Pacific from ARGO data

Convection process in the North Pacific from ARGO data

1Eunjeong Lee, Yign Noh, 2Bo Qiu

1Department of atmospheric sciences, Yonsei University

2Department of Oceanography, University of Hawaii

Department of Atmospheric Sciences, Yonsei University

Contents

• Objective

• About ARGO

• Data analysis

- ARGO

- NCEP/NCAR reanalysis I• Results

PartⅠ - Response of the ocean to the surface cooling - Deepening of MLD - In the KE region (Eddy process)

PartⅡ - Correlation - Efficiency (deepening, heating & cooling)• Conclusion


Objective

• Analysis of the convection process in the upper ocean to the

atmospheric forcing using ARGO data

- How are the variations of the MLD and SST related to the surface

forcing?

i) Understanding the air-sea interaction in the North Pacific

ii) Providing the information for the parameterization of

convection in the mixed layer model


About ARGO

• Profile data, metadata, trajectories and technical data

• An ascending profile with measurements

(e.g. pressure, temperature, salinity)

• Data mode (e.g. R : Real time, D : Delayed mode, A : adjusted values)

• Quality control (e.g. 1:good data, 4:bed data, 9:missing value)

Position of float Processing


Data analysis : ARGO

Area : North Pacific (130-240˚E, 20-60˚N)

0-500m depth

Period : 2001 - 2007

27 different locations

• Data processing

- use data with quality control 1 or 2.

- semi-monthly averaging

- mixed layer depth : z = z [T(0)-0.5]


• Surface heat flux

LSLWSWNET QQQQQ

fluxheatlatentandsensibleQQ

fluxheatradiationlongwaveandsolarwaveQQ

fluxheatnetQ

LS

LWSW

NET

:,

:,

:

Data analysis : NCEP data

– (+) : direction from atmosphere to ocean

• Data processing

– semi-monthly averaging

– 2001-2007 data on an average compare with each year value

• NCEP reanlaysis I – surface heat flux, SST


Part Ⅰ : Response of the ocean to the surface cooling

2005-2006 년

• 135-140˚E, 28-30˚N2005-2006 년

• 150-155˚E, 28-30˚N

Location

Heat Flux

SST

MLD

Reduce

Mean Each year


Part Ⅰ : Deepening of MLD in winter

2005-2006 년2004-2005 년

135-140˚E, 28-30˚N

Location

Heat Flux

SST

MLD

slower deepening faster deepening


Part Ⅰ : Deepening of MLD in winter

2002-2003 년2003-2004 년

175-180˚W, 42-44˚N

Location

Heat Flux

SST

MLD

Insensitive to surface heat flux


The KE region

• Near 145˚E, 35˚N

• High T & S (20°, 34.5‰), 50~300m/s velocity

• Eddy process


The KE region


PDO index

EKE level

• Center of action of wind forcing is in the eastern half of the N Pacific basin

• Positive (negative) phase of PDO generates – (+) local SSH through Ekman divergence (convergence)

[Qiu et al.(2008)]

Part Ⅰ : Eddy process

2005-2006 년2004-2005 년

145-150˚E, 32-34˚N

Location

Heat Flux

SST

MLD


Part Ⅰ : Eddy process

2005-2006 년

Kuroshio Extension

• 155-160˚E, 32-34˚N

Location

MLD

the effect of internal ocean dynamics is important

→ eddy process

Eddy processing

interrupt

MLD deepening

Due to eddy processing


d(MLD) vs. Qdt[225-230 lon, 50-52 lat]

d(MLD) [m]

-150 -100 -50 0 50 100 150

Qd

t [W

/m2

]

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

JAN & FEBMAY & JUNJUL & AUGNOV & DEC

d(SST) vs. Qdt[225-230 lon, 50-52 lat]

d(SST) [C]

-4 -3 -2 -1 0 1 2 3 4

Qd

t [W

/m2

]

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000


SST vs. MLD[225-230 lon, 50-52 lat]

SST [C]

0 2 4 6 8 10 12 14 16 18 20

ML

D [

m]

50

100

150

200

250

300

350DECJANFEBMAR

Part Ⅱ : Relation

•130-135˚W, 50-52˚N

No horizontal advection

d(MLD)&Qdt

d(SST)&Qdt SST&MLD


d(MLD)=MLD(t+15)-MLD(t)

d(MLD) vs. Qdt[155-160 lon, 32-34 lat]

d(MLD) [m]

-150 -100 -50 0 50 100 150

Qdt [W

/m2]

-8000

-6000

-4000

-2000

0

2000

4000JAN & FEBMAY & JUNJUL & AUGNOV & DEC

SST vs. MLD[155-160 lon, 32-34 lat]

SST [C]

0 2 4 6 8 10 12 14 16 18 20

ML

D [m

]

50

100

150

200

250

300

350DECJANFEBMAR


d(SST) [C]

-4 -3 -2 -1 0 1 2 3 4

Qd

t [W

/m2

]

-8000

-6000

-4000

-2000

0

2000

4000



d(SST) [C]

-4 -3 -2 -1 0 1 2 3 4

Qd

t [W

/m2

]

-8000

-6000

-4000

-2000

0

2000

4000


Part Ⅱ : Relation

•155-160˚E, 32-34˚N

d(SST)&Qdt

d(MLD)&Qdt

SST&MLD

horizontal advection


• Strong heating→strong stratification

→ shallower MLD

• Weak correlation in the KE region duo to advection effect

• d(MLD) & Qdt

Part Ⅱ : Correlation

JUL & AUGMAY & JUN

• Already shallow MLD

→ no longer weakening of MLD

d(SST)Qdt

-0.8 -0.5-0.6 -0.4 -0.2-0.3 -0.1 -0.05 0 0.1 0.2 0.3 0.50.4 0.6 0.80.05

summer


• d(MLD) & Qdt


-0.8 -0.5-0.6 -0.4 -0.2-0.3 -0.1 -0.05 0 0.1 0.2 0.3 0.50.4 0.6 0.80.05

Early summer


Strong eddyWeak eddy

• Strong cooling →weak stratification

→ rapid convective deepening

• Weak correlation in the KE region duo to advection effect

• d(MLD) & Qdt


JAN & FEBNOV & DEC

• Already deep MLD

→ no longer deepening of MLD

: Maximum MLD is insensitive to surface cooling

d(SST)Qdt

-0.8 -0.5-0.6 -0.4 -0.2-0.3 -0.1 -0.05 0 0.1 0.2 0.3 0.50.4 0.6 0.80.05

winter


• d(MLD) & Qdt


-0.8 -0.5-0.6 -0.4 -0.2-0.3 -0.1 -0.05 0 0.1 0.2 0.3 0.50.4 0.6 0.80.05


Early winter

Strong eddyWeak eddy

• Deepening efficiency

Part Ⅱ : Deepening efficiency

Qdt

MLDd )(


• Overall positive efficiency

• Deepening efficiency

Part Ⅱ : Deepening efficiency

JAN & FEBNOV & DEC

11

12

-0.02 -0.01 -0.005-0.007 -0.004 -0.003 -0.002 0.001 0.007 0.02-0.001 0.010.002 0.003 0.004 0.0050

• Negative efficiency in the KE region

• Stronger efficiency than NOV& DEC except KE region

winter


• Heating(Cooling) efficiency

Part Ⅱ : Heating(Cooling) efficiency

Qdt

SSTd )(


• Heating efficiency


MAY & JUN

summer

JUL & AUG

Low heating efficiencyAdvection + heating effect

11

12

-0.02 -0.01 -0.005-0.007 -0.004 -0.003 -0.002 0.001 0.007 0.02-0.001 0.010.002 0.003 0.004 0.0050


• Cooling efficiency


JAN & FEB

winter

NOV & DEC

Advection + heating effectAdvection + cooling effect Low cooling efficiency

11

12

-0.02 -0.01 -0.005-0.007 -0.004 -0.003 -0.002 0.001 0.007 0.02-0.001 0.010.002 0.003 0.004 0.0050


Conclusion

• The response of the ocean mixed layer and sea surface temperature to

surface forcing in the Pacific was investigated by analyzing ARGO data.

The d(SST) and d(MLD) has high correlation and efficiency with surface

cooling except in the KE region in early summer and winter.

The d(MLD) are more sensitive to the surface heat flux in late summer and

winter.

The initial convective deepening shows large variability, but the maximum

MLD does not show much variability.

In the KE region,

- the MLD increase is interrupted by mesoscale eddies

- the heat transport by the Kuroshio is important to determine SSTDepartment of Atmospheric Sciences, Yonsei University

Reference

• Argo Data Management Team (2004), Argo quality control manual, version 2.0b, p. 23, Argo Data Manage., Toulouse, France.

• Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, M. Chelliah, W. Ebisuzaki, W. Higgins, J. Janowiak, K. C. Mo, C. Ropelewski, J. Wang, A. Leetmaa, R. Reynolds, R. Jenne, and D. Joseph (1996), The NCEP/NCAR 40-Year Reanalysis Project, Bull. Am. Meteorol. Soc., 77, 437- 471.

• Qiu, B., S. Chen, and P. Hacker (2007), Effect of mesoscale eddies on Subtropical Mode Water variability from the Kuroshio Extension System Study (KESS), J. Phys. Oceanogr., 37, 982-1000.


Thank you


(a) Upstream KE path length (141-153°E)

(b) Eddy kinetic energy (141-153°E, 32-38°N)

Stable yrs: 1993-94, 2002-04

Unstable yrs: 1996-2001, 2006-07

Convection process in the North Pacific from ARGO data

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