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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