SMOS AlgoVal meeting #16, Brest, 8-9 July, 2009 Computing Tb BOA and Tb surf C. Gabarró, J. Font SMOS Barcelona Expert Centre Pg. Marítim de la Barceloneta 37-49, Barcelona SPAIN URL:

SMOS AlgoVal meeting #16, Brest, 8-9 July, / 10 Gal + cosmic atmosphere Geometric ionosphere Tb_gal Tb_Atm_up Tb_Atm_dn Tb_Toa – earth ref Tb_XY – antenna ref Tb_boa Tb_surf =Tb_flat+Tb_rough Reflection

SMOS AlgoVal meeting #16, Brest, 8-9 July, / 10 Why to compute Tb boa and Tb surf  From L1c -> TBX,Y  Tb boa 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 Tb boa 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, / 10 Equations to compute Tb BOA How to compute it? From sea to antenna From antenna to sea

SMOS AlgoVal meeting #16, Brest, 8-9 July, / 10  Data needed to compute Tb_boa and Tb_surf:  BP_FOM_8-1:  Tb AtmUp (H,rough_model=1) =Tb AtmDn  Tb Foam (H & V,rough_model=[1->2])  Tb Gal (H & V, rough_model=[1,4]) ; Why different for RGH1 and 4?  Trans (rough_model=1)  Theta (rough_model=1)  F foam (rough_model=[1,2])  Tb Flat (H & V pol,rough_model=1)  Tb Rough (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, / 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, / 10  How to compute the Fresnel reflection coefficient? -> problem only for Tb surf not for Tb BOA  Compute Γ from a flat sea or from 2-scale or SSA? Is it acceptable to use those with the other models?

SMOS AlgoVal meeting #16, Brest, 8-9 July, / 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 to wind speed [Reul et al., 2006] from Camps et al, Figure from Zine et al Figure from Camps et al

SMOS AlgoVal meeting #16, Brest, 8-9 July, / 10 Critical case: Tb rough =0.5 *WS(15m/s)=7.5K SST=288 K Tb flat =110K Γ tbrough=0 = Γ tbrough=7.5 =0.592 Γ tbrough=0 *TB DN (6K)=3.708 Γ tbrough=0 *TB gal (10K)=6.18 Γ tbrough=7.5 *TB DN (6K)=3.552 Γ tbrough=7.5 *TB gal (10K)=5.95 ΔTB DN =0.156 K ΔTB gal =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, / 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, F foam -> 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 Barcelona, SPAIN Tel. (+34) ; Fax. (+34) URL: