SMOS AlgoVal meeting #16, Brest, 8-9 July, 2009

Computing TbBOA and Tbsurf

C. Gabarró, J. FontSMOS Barcelona Expert CentrePg. Marítim de la Barceloneta 37-49, Barcelona SPAINE-mail: email@icm.csic.esURL: www.smos-bec.icm.csic.es

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20092 / 10

Gal + cosmic

atm

osp

here

Geom

etr

icio

nosp

here

Tb_gal

Tb_Atm_upTb_Atm_dn

Tb_Toa – earth ref

Tb_XY – antennaref

Tb_boa

Tb_surf =Tb_flat+Tb_roughReflection

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20093 / 10

Why to compute Tbboa and Tbsurf

From L1c -> TBX,Y

Tbboa and Tb surface useful for:

Calibration/Validation as pointed out by Cal/Val teams Comparisons with insitu are more intuitive and could help on

decision between Full vs Dual pol For assimilation of Tbboa in general circulation models

Evaluation of roughness models To derive roughness model 3 from the ECMWF parameters

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20094 / 10

Equations to compute TbBOA

flatsurf

rough

τDNBOAsurf

τUPTOABOA

y

x

TOA

TOA

VTOA

HTOA

y

x

VTOA

HTOA

TbF

foamTbTbTb

egalTbTbTbTb

eTbTbTb

T

T

T

T

IMR

Tb

Tb

Tb

Tb

T

TIMR

Tb

Tb

atm

atm

1

_

)_(

)(

4

2

4

3

4_

3_

_

_

_

_

How to compute it?

4

3

4_

3_

_

_

4

)_(

)1)(

T

T

T

T

IMR

Tb

Tb

Tb

Tb

TbeTbTb

egalTbTbTbTb

TbFTbroughTbTb

y

x

TOA

TOA

VTOA

HTOA

UPτ

BOATOAEARTH

τDNseaBOA

foamflatsurf

atm

atm

From sea to antennaFrom antenna to sea

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20095 / 10

Data needed to compute Tb_boa and Tb_surf:

BP_FOM_8-1: TbAtmUp(H,rough_model=1) =TbAtmDn

TbFoam(H & V,rough_model=[1->2])

TbGal(H & V, rough_model=[1,4]) ; Why different for RGH1 and 4?

Trans (rough_model=1) Theta (rough_model=1) Ffoam (rough_model=[1,2])

TbFlat (H & V pol,rough_model=1)

TbRough(H & V & 3rd & 4th,rough_model=[1->4])

BP_FOM_9-1: a (is the angle for geometry and faraday, H)

BP_MAP_3_3-1 A_cor (corrected measured antenna TB, only for valid meas. H&V)

For comparison purpose only

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20096 / 10

Problems and questions:

TEC is retrieved at L2. It is possible to use TEC from L1c or from L2 – UDP.

Should Tb_gal be rotated by geometry and Faraday (Joe)? What to do for θ=+/-45? -> Singularity for dual-pol -> θ ± ε

If I (Th+Tv) is used -> avoid problems on rotation

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20097 / 10

How to compute the Fresnel reflection coefficient? -> problem only for Tbsurf not for TbBOA

Compute Γ from a flat sea or from 2-scale or SSA?

Is it acceptable to use those with the other models?

SSTTbTb roughflat /)(1

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20098 / 10

Figure, Intercomparison between Small Slope Approx.: (triangles) with Kudryavtsev sea surface spectrum (without foam), the WISE measurements (stars + dotted line for error bars) and Hollinger’s measurements (diamonds + solid error bars) of the TB sensitivity towind speed [Reul et al., 2006] from Camps et al, 2008.

Figure from Zine et al. 2008.

Figure from Camps et al. 2004.

SMOS AlgoVal meeting #16, Brest, 8-9 July, 20099 / 10

Critical case:

Tbrough=0.5 *WS(15m/s)=7.5K

SST=288 K Tbflat=110K

Γtbrough=0=0.6180 Γtbrough=7.5=0.592

Γtbrough=0 *TBDN(6K)=3.708 Γtbrough=0 *TBgal(10K)=6.18 Γtbrough=7.5 *TBDN(6K)=3.552 Γtbrough=7.5 *TBgal(10K)=5.95

ΔTBDN =0.156 K ΔTBgal =0.23 K

So any roughness model could be used for computing Γ*Tb_gal and Γ*Tbatm with ECMWF roughness param. -> small impact

Is there a LUT for Tbgal_refl? And a LUT for Γ ?

SMOS AlgoVal meeting #16, Brest, 8-9 July, 200910 / 10

How to do this operational?

Now, impossible since files of 8G for only 5º of lat. (15 h, for 1 it.) -> Need to find a solution.

Create new breakpoints containing only the needed info? May be to obtain Tb_gal_ref, TBatm, trans, Tb_foam, Ffoam ->

from Ingo MATLAB mex code?

May be to retain information of N GPs, and then write in several breakpoints --> avoid to write every GP.

Or if memory permits, to write info at the end of processing, as it is done with UDP and DAP.

SD: there is a tool (Brockman consult) for having SMOS L1c only for a defined area

SMOS Barcelona Expert Centre (SMOS-BEC)Pg. Marítim de la Barceloneta 37-49, E-08003 Barcelona, SPAINTel. (+34) 93 230 95 00; Fax. (+34) 93 230 95 55URL: www.smos-bec.icm.csic.es