General Objective: to improve the quality of SST products used by EU-MERSEA modeling and assimilation centres and produce Mediterranean Sea analyzed SST fields needed for MERSEA models The potential for L2P uptake by Mediterranean users: validation, intercomparison and improvements of Medspiration and MFS L4 products and processors

CNR work within EU-MERSEA project concerns : Inter-comparison and validation of MEDSPIRATION L4 and MFSTEP SST products. Tuning of Medspiration L4_processor Improvement of MFSTEP analyses Ref. MERSEA deliverable: Report on the inter-comparison of MEDSPIRATION and MFSTEP SST analyses over the Mediterranean Sea.

Could Medspiration L4 sub-sampled over MFS grid be used in the assimilation? Could the present MFS analysis be improved by including Medspiration L2P data? or: Can it be run only with Medspiration L2P? Can the Medspiration L4 software be run directly to interpolate on the model grid, with stable results, possibly improving MFS?

MFS L4 using GHRSST products f l o w c h a r t Data mergingISAC Optimal Interpolation Data delivery on the GOS-ISAC web-site Data quality controll Night-time SST using MF algorithm Cloud detection SST daily composite binning on model grid (1/16x1/16) MF AVHRR acquisition Atlantic buffer zone + west Med Night-time SST using Pathfinder algorithm Cloud detection SST daily composite binning on model grid (1/16x1/16) ISAC AVHRR acquisition Entire Mediterranean L2P Medspiration Products

Period examined: jan-oct 2005 Methods: Evaluation of processor performance: -qualitative -quantitative  Comparison of SST L4 against quality controlled in situ XBT data acquired within MFSTEP Test performed: MFS at 1/16°  AVHRR by CNR+CMS  merging MFS data and SEVIRI/AATSR L2P  only L2P (all infrared) original configuration Medspiration L4 at 2 km resampled at 1/16°  L2P original configuration Medspiration L4 at 1/16° (hereafter MERSEA L4)  L2P different configurations starting from parameters similar to MFS ones

REMARKS: MFS and Medspiration processors have different data editing and selection criteria/strategies -bias between sensors -selection of valid input (confidence values, clouds) -selection of influential observations within the bubble but the different OI configurations can be tuned to have - similar spatial and temporal influential radius (‘bubble’)… - same correlation function - same grid/resolution

MFSTEP –spatial distribution of XBT measurements Evaluation of SENSOR BIASES  needed to choose a reference sensor for data merging with MFS processor  impact on quality of MERSEA L4

Evaluation of SENSOR BIASES: results

L =180 km τ =7 days MERSEA: SELMS_LIST > NAR17_SST AVHRR17_L NAR16_SST AVHRR16_L X_BUL_RATIO=2.0 Y_BUL_RATIO=2.0 T_BUL_RATIO=1.0 OAN_KEEP_ALL_MEAS = 0 #For each sensor, in each cell of the collated file, only the nearest #measurement to the processing date is kept. There is only one #observation file created per sensor. # #OAN_KEEP_ALL_MEAS = 1 # For each sensor, in each cell of the collated file, the whole #measurements are kept. There is one observation file per sensor and #per days created. MFS: Reference sensor priority: AATSR NAR17 AVHRR17_L SEVIRI NAR16 AVHRR16_L DIST=200starting spatial influential radius for data selection. RMAXDIST=600maximum spatial influential radius for data selection (the influential radius is incremented if data selected within DIST are less then LIMIT). NPIX=3number of values selected in time for each pixel. Medspiration results:

MFS and Medspiration L4 original configuration MFS (only AVHRR) MEDSPIRATION L4 subsampled at 1/16°

MFS with new INPUT data MFS (MFS+infrared L2P)MFS (infrared L2P only)

MERSEA L4 (CLS processor with new configuration) MERSEA (no bias) MERSEA (bias correction)

MFS and Medspiration L4 original configuration

MFS with new input data

MERSEA L4 (CLS processor with new configuration)

MFS and MERSEA new L4 configuration

MFS and Medspiration L4 original configuration

MFS with new INPUT data

MERSEA L4 (CLS processor with new configuration)

MFS and MERSEA new L4 configuration

No bias correction Bias correction applied Impact of bias correction on MERSEA L4

(A1d) bias, OAN_KEEP_ALL_MEAS=1 (A2e) bias, OAN_KEEP_ALL_MEAS=0 Impact of the number of observations per sensor

One possible evolution #OAN_KEEP_ALL_MEAS = N #For each sensor, in each cell of the collated file, only the first N nearest in time #measurements are kept. There is one observation file per sensor and #per days created???? other possible evolution: data reduction strategy?

CONCLUSIONS Could Medspiration L4 sub-sampled over MFS grid be used in the assimilation? not with original configuration Could the present MFS analysis be improved by including Medspiration L2P data? Yes, to be implemented operationally Can it be run only with Medspiration L2P? Yes, to be implemented operationally Can the Medspiration L4 software be run to interpolate directly on the model grid, with stable results, possibly improving MFS? Possibly yes, but more work has to be done (understand biases, reduce computation time)