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CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 1 Extracting Dynamics of Multiple Indicators for Spatial recognition of Ecoclimatic zones in Circum-

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Presentation on theme: "CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 1 Extracting Dynamics of Multiple Indicators for Spatial recognition of Ecoclimatic zones in Circum-"— Presentation transcript:

1 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 1 Extracting Dynamics of Multiple Indicators for Spatial recognition of Ecoclimatic zones in Circum- Saharan Africa Didier Leibovici and Gilbert Quillevere Centre for Geospatial Sciences, University of Nottingham, Nottingham UK IRD-US166 Désertification, Maison de la Télédétection, Montpellier France didier.leibovici@nottingham.ac.uk

2 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 2 ROSELT network www.roselt-oss.org long term monitoring of desertification representativeness of 30 observatories arid, semi-arid, dry sub-humid circum-Saharan region BiophysicalEcologicalSocio-economical Spatio-temporal variations Ecoregion delineation homogeneous zones

3 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 3 focusing on ecoclimatic variations (physical climatic aspects) arid semi-arid dry sub-humid indicators aridity index P/ETo~0.10 ~0.35 ~0.50(annual) mensual variations !? (see ombrothermal diagrams Le Houérou) e.g. WORLDCLIM1950-2000 www.worldclim.org/current.htm FAO www.fao.org averages over 50 years

4 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 4 clustering the dy n amics capturing spatio-temporal variations 12 x 10 values at 298249 pixels (grid 5’’) meaningful correlations among 120 variables ?! 120 indicators 298249 locations kmeans or PCA + kmeans ? 12 months 298249 locations 10 indicators tensorial structure analysing interactions space x time x indicators PTAk + kmeans P rincipal T ensor A nalysis on k -modes (k=3) offers a generalisation of PCA

5 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 5 Principal Tensor Analysis on k-modes (k=3) R add-on package www.r-project.org PCA PTAk 1st principal tensor of a 2-way table, of 3-way table matrix calculus to tensor algebra

6 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 6 { { { 298249 x 10 x 12 decomposition of Sum of Squares like PCA but a multi-level hierarchy PCA of 298249 x 10 (63.66%)23.15% 6.95% 3.31% … recursive algorithm

7 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 7 s latitude gradients from Sahara (<>) i drought/extreme conditions ETo, dM, Tmax <> rain related indicators Q3, P, PETo m all year more during months 5 to 10 s sea shore and low relief<>high relief i temperature Tmin, Tave but also Q3 <> altitude Alt m all year more during months 5 to 10 vs111 39.15% 12vs111 298249 10 14.24%

8 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 8 s Maghreb and equatorial <> Sudan-Sahel zone i temperature Tmin, Tave, Tmax, and altitude Alt <> rain and aridity indicators Q3, P, PETo, dM m wet hot months 7, 8, 9 and dry months 12, 1, 2 <> mid seasons months 4, 5, 10 s oceanic equatorial <> gradient North-South in Maghreb i (<>) temperature Tmin, Tave, Tmax, and evapotranspiration ETo m 6, 7, 8, 9 <> dry months 11, 12, 1, 2 vs333 1.64% Vs222 16.33%

9 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 9 s gradiant N&S Sudan-Sahel zone<> north Maghreb and equatorial i rain related indicators Q3, P, PETo, dM (<>) m 6, 7, 8, 9 <> dry months 11, 12, 1, 2 12vs222 298249 10 3.53% 10 vs222 298249 12 0.84% s north Maghreb and Guinea area(<>) i (<>) temperature Tmin, Tave, Tmax, evapotranspiration ETo m end of dry months 3, 4, 5 <> 7, 8

10 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 10 kmeans clustering of selected (s) in 15 classes shapefile on Catalogue Service Web mdweb.roselt-oss.org classes proximity from hierarchical clustering ecoclimatic pattern ROSELT covers all the classes in arid, semi arid, sub humid zones observatories mainly of one class (but 1/3 of 2 calsses: 80% area in 1 class) 0.08dd is between 9km and 7.5km

11 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 11 Some drawbacks resolution (1’) relatively to observatory size (~20 pixels … ) 50 years average (WORLDCLIM) … periods number of classes only ecoclimatic delineation Some solutions better resolutions available introducing periods (within the 50 years) and performing a PTA4 space x months x period x indicators multilevel classification (cutting the tree) : e.g. kmeans with 40 +hierachical tree of them intercepting classes from same methodology on different domains ecolimatic  soil-vegetation  socio-economic or using all indicators together (allowing correlation between domains) months locations indicators months locations indicators period

12 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 12 Extracting Dynamics of Multiple Indicators for Spatial recognition of Ecoclimatic zones in Circum-Saharan Africa Didier Leibovici and Gilbert Quillevere Centre for Geospatial Sciences, University of Nottingham, Nottingham UK IRD-US166 Désertification, Maison de la Télédétection, Montpellier France didier.leibovici@nottingham.ac.uk Merci – Questions? months locations indicators


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