Summer SchoolRio de JaneiroMarch 2009

5. MODELING MARITIME PBL

Amauri Pereira de Oliveira

Group of Micrometeorology

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Topics

1. Micrometeorology

2. PBL properties

3. PBL modeling

4. Modeling surface-biosphere interaction

5. Modeling Maritime PBL

6. Modeling Convective PBL

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Modeling Maritime PBL

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Maritime PBL

Sjöblom, A. and Smedam, A.S., 2003: Vertical structure in the marine atmospheric boundary layer and its implication for the inertial dissipation method, Boundary-Layer Meteorology, 109, 1-25

•Inertial layer;•Roughness layer.

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What is going on beneath the ocean surface

Thorpe, S.A., 2004: Recent developments in the study of ocean turbulence. Ann. Rew. Earth Planet. Science., 32, 91-102.

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Oceanic mixed layer

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Air-Sea Interaction

Edson et al., 1999: Coupled Marine Boundary Layers and Air-Sea Interaction Initiative: Combining Process Studies, Simulations, and Numerical Models.

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Some important discrepancies

Wainer, et al., 2003: Intercomparison of Heat Fluxes in the South Atlantic. Part I: The Seasonal Cycle. Journal of Climate.

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Convective PBL over Cabo Frio

• Cabo Frio – upwelling area• Upwelling - Stable PBL• Cold Front passage disrupt upwelling • Upwelling give place to a downwelling• Dowelling - Convective PBL

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References

Dourado, M.S. and Oliveira, A.P., 2008: A numerical investigation of the atmosphere-ocean thermal contrast over the coastal upwelling region of Cabo Frio , Brazil, Atmosfera , 21(1) ,13-34.

Dourado, M., and Oliveira, A.P., 2001: Observational description of the atmospheric and oceanic boundary layers over the Atlantic Ocean. Revista Brasileira de Oceanografia, 49, 49-64.

Available at:

http://www.iag.usp.br/meteo/labmicro

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Cabo Frio upwelling

SST

AVHRR NOAA(Dutra et al. 2006, XV CBMET)

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Upwelling Downwelling

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Cold Front July 6, 21GMT

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Cold Front

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upwellingdownwellin

g

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Second Order Closure Model

Oceanic mixed layer model

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Mean equations

z

´w´u)vV(f

t

uG

z

´w´v)uU(f

t

vG

z

R

cρ

1

z

´w'θ

t

θ N

P

vV

z

´w´q

t

q

Momentum

Thermodynamic

Specific Humidity

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Second Order Closure Model

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Oceanic Mixed Layer Model

(i) The turbulent mixing is strong enough so that upper ocean is characterized by a mixed layer where the temperature does not vary in the vertical direction;

(ii) Transition layer between the mixed layer and the stratified non turbulent ocean bellow is much smaller than the mixed layer so that the vertical variation of temperature can be indicated by a temperature jump;

(iii) The energy required to sustain turbulent mixing is provided by convergence of the vertical flux of TKE.

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Oceanic Mixed Layer Model

Mixed layer

ocean

atmosphere

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Oceanic Mixed Layer ModelTemperature (To)

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Derivation of OML Temperature equation

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Oceanic Mixed Layer Modeldepth (h) and temperature jump

(ΔT)

BT

0T13*1

Tαg

´w´TαgBhνA

h

1

td

hd

h

1´w´TII

cρ

1

td

hd

h

T

td

)T(d0Nh0N

ww

BB

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Turbulent heat flux effects

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Boundary (coupling) conditions

ww

000N0N0

c

LEHIR´w´T

Energy

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Oceanic Mixed Layer

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**P00 θucρH

**e00 quLρLE

Atmospheric turbulent fluxes

CH, CE and CD are transfer coefficient of sensible, latent and momentum (drag coefficient).

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Atmospheric turbulent fluxes

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Radiation balance at the surface

00000N LWULWDSWUSWDR

ZcosISWD 00

00 SWDSWU

Short wave down

Short wave up

Zcos2.06.0

rZtan

rZtan

rZsin

rZsin50.0

2

2

2

2

Broadband transmissivity

Albedo

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Radiation balance at the surface

Long wave contribution

Long wave up

Long wave down

ε = 0.98 Surface emissivity

a = 0.52 and b = 0.064

4000 TσεLWU

4RR0 Tσ)eba(LWD

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Boundary and coupling conditions

w0** u Stress

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MIXING LAYER MODEL CLOSURE

w

pe

zw

g

zd

vdwv

zd

udwu

t

e

00

Applying TKE equation to transition layer

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MIXING LAYER MODEL CLOSURE

i

0i0

wp

ez

wg

0

In the interface

Dimensional analysis

hw

pe

z

3

w

i0

hg

1w

3

w

0

i

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MIXING LAYER MODEL CLOSURE

1. Stationary:

2. Shear production, molecular dissipation and pressure term are neglected in transition layer is neglected because:

0t

e

0zd

udwu

zd

udwu

0

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Mixing Layer Model

TransitionLayer

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i)w(t

h

hh

h

h

)w()w(zdt

Thermodynamic Equation

Limit 0

z

)w(

t

ewt

h

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MIXING LAYER MODEL CLOSURE

hg

1w

3

w

0

i

2.0w

3

*

3

w

Thermal mixing Mechanical Mixing

3*

3w uA

hwg

w 0

0

3

*

gh

uAw 0*

i

0i w2.0w

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Stable and Convective Run

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Upwelling – Stable PBL

Downwelling - Convective PBL

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Upwelling – Stable PBL

Downwelling - Convective PBL

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Upwelling – Stable PBL

Downwelling - Convective PBL

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Upwelling – Stable PBL

Downwelling - Convective PBL

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PBL Time Evolution

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Fluxes and Variances

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Observations

• FluTuA– Campaign May 2002– Campaign December 2008

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FluTuAObservational campaign May

2002

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Bacellar, S., Oliveira, A. P., Soares, J., and Servain, J., 2009:

Assessing the diurnal evolution surface radiation balance over the

Tropical Atlantic Ocean using in situ measurements carried out

during the FluTuA Project. Meteorological Application.

http://dx.doi.org/10.1002/met.111

Available at:

http://www.iag.usp.br/meteo/labmicro/index_arquivos/Page779.htm

References

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Surface Emissivity

ε = 0.97 Surface emissivity

ε = 0.97

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Broadband atmospheric transmissivity

Zcos3.05.0

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Surface albedo

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Net radiation

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Comparison with satellite estimate (SRB/NASA project)

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Conclusion

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Flutua 2008

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Archipelago St Peter and St Paul

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Air Temperature and SST

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Turbulence – Nighttime conditions (20 Hz)

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Turbulence – Daytime Conditions (20 Hz)

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http://www.iag.usp.br/meteo/labmicro