An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys
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An evaluation of a hybrid satellite and NWP based turbulent fluxes with TAO buoys. ChuanLi Jiang, Meghan F. Cronin , Kathryn A. Kelly, LuAnne Thompson University of Washington May,11 2005. Method. QuikSCAT winds : ; TAO & NWP :

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An evaluation of a hybrid satellite and NWP based turbulent fluxes with TAO buoys

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An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

An evaluation of a hybrid satellite and NWP based turbulent fluxes with TAO buoys

ChuanLi Jiang, Meghan F. Cronin, Kathryn A. Kelly, LuAnne Thompson

University of Washington

May,11 2005


Method

Method

  • QuikSCAT winds: ; TAO & NWP:

  • Microwave SST (MW/OI) can see through clouds, compared to AVHRR.

  • Bulk algorithm:

  • State variables: ;

    ;

  • Strategy: COARE v3.0 algorithm

    Most accurate state variables evaluated by TAO buoys


Tao buoys

+

64 buoys for

38 buoys for

TAO buoys


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Data

  • 2-year: Jan.2000 – Dec.2001

  • Smooth all variables to 4day, QuikSCAT winds map (kelly et al. 1999)

  • Vector-averaged relative wind speed:

  • Zonal ocean currentfrom altimeter (kelly et al. 2004)

  • Bulk SST is used, instead of skin SST


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Wind speed comparison…

NCEP1 too weak

NCEP2 better than NCEP1

ERA40 better than NCEP

QuikSCAT best,

Strong along 165E & 8N

bias=mean(Products -TAO)


Histograms of wind speed near itcz

lacks low wind speed

Weak zonal currents

rain contamination

match best

Histograms of wind speed near ITCZ


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Air specific humidity comparison…

ERA40 has best humidity

Dry along 165E

NCEP2 worse than NCEP1

Better along 8N


State variables evaluation averaged over tao buoys

State variables evaluation averaged over TAO buoys…

QuikSCAT

Hybrid

ERA40

ERA40

MW/OI


Errors of lhf to variables products averaged over tao buoys

3

1

2

Products

Bias

SDD

Bias

SDD

Bias

SDD

Bias

SDD

NCEP1

2.3

11.6

-0.8

1.4

-6.3

18.3

15.0

13.0

NCEP2

1.6

11.6

0.2

1.4

-3.1

18.4

2.5

13.8

ERA40

-0.5

10.4

-0.4

1.0

-4.8

11.0

4.4

8.3

MW/OI

3.7

8.5

QuikSCAT

-4.0

6.9

Errors of LHF to variables productsaveraged over TAO buoys…

LHF ERRORHUMIDITY+WINDS+SST


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

LHF evaluation on TAO buoys:


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

LHF comparison…

Fields

NCEP1C

NCEP2C

ERA40C

Hybrid

NCEP1C underestimate

Bias

SDD

Bias

SDD

Bias

SDD

Bias

SDD

NCEP2C overestimate

LHF

10.7

24.8

-8.9

26.6

-1.5

18.1

-5.8

16.2

ERA40C good

Fields

NCEP1

NCEP2

ERA40

Hybrid best in the east

Overestimate along 165E,8N

Bias

SDD

Bias

SDD

Bias

SDD

LHF

-4.7

26.8

-28.6

32.0

-13.6

18.1


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

LHF map comparison…

Hybrid LHF

Larger than NWPC

Hybrid LHF is similar to

NCEP1 off the equator


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Evaluation

(TAO BUOYS)

U

r

ERA40

SCAT

MW/OI

ERA40

VOTE

-Hybrid~ERA40C, but better for models studies

-Hybrid~TAO LHF, accuracy 10-15 (Cronin et al. 1997)

-COARE improved NCEP2 & ERA40

-NCEP algorithm tuned to NCEP1 variables

Summary

  • Evaluation of state variables:

  • Evaluation of LHF: VOTE -- Hybrid

  • Map Comparison:

-Mean Hybrid structure similar to NCEP1

  • Combining QuikSCAT winds and microwave SST to

  • produce turbulent heat fluxes products is promising.


Outline

Outline

1. Motivation

2. Method & Data

3. TAO buoys comparisons

4. Heat flux maps comparisons

5. Applications (See Thompson et al. poster)


Motivation

Motivation

  • Intra-seasonal mixed layer heat budget in the equatorial Pacific plays an essential role in studying the physical processes that contribute to the ENSO variability and climate change. (McPhaden, 2002; Kessler et al. 1995; Zhang, 2001).

  • NWP winds and heat flux products have shown problems.

  • Satellite measurements provide accurate variables to calculate both momentum and turbulent heat fluxes.

  • A new turbulent heat flux product calculated from QuikSCAT winds and Microwave SST is promising (Jiang, Cronin, Kelly and Thompson, under revision to J.G.R).


Quikscat winds

QuikSCAT winds…

  • Obtain relative wind vector to ocean surface using model function that relates 10m wind vector to surface roughness.

  • QuikSCAT:

    TAO & NWP:

Passive microwave TMI SST (MW/OI)…

  • Compared to infrared AVHRR, MW/OI can see through clouds, need less atmosphere correction.

  • 1-2mm SST

  • 25km resolution

  • 40S-40N


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Data

  • 2-year: Jan.2000 – Dec.2001

  • Smooth all variables to 4day, QuikSCAT winds map (kelly et al. 1999)

  • Vector-averaged relative wind speed:

  • Zonal ocean currentfrom altimeter (kelly et al. 2004)

  • Bulk SST is used, instead of skin SST


Nwp sst warm in the cold tongue cold off the equator mw oi consistently cold

SST comparison…

Bias=mean(Products - TAO)

SDD=STD(Products - TAO)

NWP SST: warm in the cold tongue; cold off the equatorMW/OI: consistently cold


Histograms of wind speeds in eastern pacific

match best

NWP lacks high winds

Histograms of wind speeds in eastern Pacific


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Error of LHF to state variables:

Error to VAR=mean{LHF(VAR+all other TAO)-LHF(all TAO variables)}


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

Along 165E…

LHF bias

Sens to

Sens to

Sens to

Sens to

Sens to

ERA40 overcompensates better LHF

Hybrid dry humidity+strong winds  larger LHF


An evaluation of a hybrid satellite and nwp based turbulent fluxes with tao buoys

LHF evaluation averaged over TAO buoys:

Fields

NCEP1C

NCEP2C

ERA40C

Hybrid

Bias

SDD

Bias

SDD

Bias

SDD

Bias

SDD

LHF

10.7

24.8

-8.9

26.6

-1.5

18.1

-5.8

16.2

Fields

NCEP1

NCEP2

ERA40

Bias

SDD

Bias

SDD

Bias

SDD

LHF

-4.7

26.8

-28.6

32.0

-13.6

18.1

Algorithm

tuned to

observation

Same

algorithm

as NCEP1

COARE

algorithm

improved

Difference=Algorithm + State variables + Temporal resolution of input variables


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