New methods on satellite image New methods on satellite image processing for the instantaneous processing for the instantaneous

estimation of velocity fields and their estimation of velocity fields and their utility in the perspective of reanalysisutility in the perspective of reanalysis

Antonio Turiel, Jordi Isern-Fontanet, Emilio García-Ladona & Jordi Font

Grupo de Oceanografía Física

ICM-CMIMA (CSIC)CMIMA

Summary

• Context

• Multiscale techniques

• Applications to satellite imagery

• Relevance for data reanalysis

Context

+ These data provide global coverage, synopticity and steady rate

+ Specific tools are needed for:

• Reanalysis of global scale historical datasets ( 20 years)• Operational uses

+ We have now historical time series of satellite images (Pathfinder, Medspiration project, MeteoSat, etc)

Multiscale techniques

+ Link image processing with thermodynamics and turbulence

+ Do not fix an observation scale (scale invariance)

+ The resulting sets have a precise, physical meaning

+ It is well adapted to study geophysical flows: atmosphere and ocean

Applications to satellite imagery

1.- Identification of physical patterns

Based on:

• Multifractal analysis

• Multiscale features

Meteosat IR image

Multifractal classification

Most Singular Manifold(MSM)

Multiscale entropy

Local Entropy

2.- Estimation of QG streamfunctions

• The MSM is identified with the main current lines

• We fix the gradient of the streamfunction over the MSM assuming flow advection

• The streamfunction is reconstructed assuming some statistical invariances

SST (IFREMER LAS) Most Singular Manifold

Most Singular StreamfunctionAltimetry (Jason-ENVISAT)

Altimetry level sets overimposed to MSS

Excerpt on velocity fields

3.- Detection of vertical movement

Advection dominated Areas (ADA)

Convection dominated areas (CDA)

Area without any observed

structure

Meteosat IR in West Africa during strong tropical storms

Images are« comparable»

Original MeteoSat IR image

MSM MSS

Original MeteoSat IR image

Images have a very different

aspect

MSM MSS

Original image MSS

Sources HyperfrequencyDivergence MCC

Relevance for data reanalysis

+ Multiscale techniques provide synoptic, global, instantaneous estimates of:

• Wind fields on atmospheric ADAs, detection of precipitation areas and, eventually, rain intensity

• Surface currents on ocean ADAs

We can evaluate statistical properties of climatic fields