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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

2 CENTRE FOR GEOSPATIAL SCIENCE Dr Didier Leibovici 2 ROSELT network 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. WORLDCLIM FAO 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 pixels (grid 5’’) meaningful correlations among 120 variables ?! 120 indicators locations kmeans or PCA + kmeans ? 12 months 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 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 { { { x 10 x 12 decomposition of Sum of Squares like PCA but a multi-level hierarchy PCA of 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 vs % 12vs %

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 vs % Vs %

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 12vs % 10 vs % 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 Merci – Questions? months locations indicators


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