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WG2 MEETING 2008 AUGSBURG

WG2 MEETING 2008 AUGSBURG. DOMINGO F. RASILLA ÁLVAREZ Dpto. de Geografía, Urbanismo y OT Universidad de Cantabria Spain. QUESTION 1: VARIABLES SLP, Z500, Z850. Regional air pollution analysis. Multipurpose climate analysis. S MODE. WINDOW SIZE DENSITY OF GRID POINTS ¿Weighting?

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WG2 MEETING 2008 AUGSBURG

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  1. WG2 MEETING 2008 AUGSBURG DOMINGO F. RASILLA ÁLVAREZ Dpto. de Geografía, Urbanismo y OT Universidad de Cantabria Spain

  2. QUESTION 1: VARIABLES SLP, Z500, Z850 Regional air pollution analysis Multipurpose climate analysis S MODE WINDOW SIZE DENSITY OF GRID POINTS ¿Weighting? ¿Re-gridding? PREPROCESSING STANDARIZATION OF GRID POINTS

  3. SPATIAL PATTERNS OF VARIABILITY PRINCIPAL COMPONENT ANALYSIS NUMBER PCs Scree test-LEV Rule N North et al ROTATION VARIMAX

  4. QUESTION 8: SIMILARITY MATRIX EUCLIDEAN DISTANCE CLUSTER ALGORITHM Hierarchical (Ward) Agglomerative (K-means) Cluster Analysis NUMBER OF CLUSTERS Following slides OUTCOME

  5. PETISCO’S PROCEDURE HOW TO SELECT THE NUMBER OF CLUSTERS TRACK OF THE LOW !!

  6. HOW TO SELECT THE NUMBER OF CLUSTERS • Hybrid method (Rasilla 2000) • Predefined number of groups (manual or subjective) • Spanish climatology tradition on Syn Class • Seed days selected through manual classification of a subset (10 years!!) + DA (statistical confirmation of reliability of the classification) • K-means of the complete dataset (1946-1998) • Too much time consuming!!!

  7. Pure statistical method (Rasilla 2006) • Several K-means solutions with algorithm (reduces the influence of the initial partition) • number of groups: subjective (analysis of climate fields) + mathematics (Pseudo-t CCC…) • Disc Ann (validation CA classification) • Cross-validation (bootstraping 2 halves) • External validation: • Climate fields • Other classifications • ¿Common sense? HOW TO SELECT THE NUMBER OF CLUSTERS ftp://ftp.sas.com/techsup/download/sample/samp_lib/

  8. Sea level pressure fields Daily precipitation fields

  9. QUESTION 2. Is a specific program/software available for the application and use of the method, or a program must be developed by the user? (addition: if not availabe, can we produce the code to be published ("open source") or is it too complicated or are there not enough details known about the technique?) SPSS with syntax file, SAS. QUESTION 3. Must the researcher have a computer programming background for the application of the method (e.g. in order to develop software)? NO QUESTION 4. How much time and computer power is roughly required for the computations? NO MORE THAN 5´ An example of a SPSS syntax file developing the procedure

  10. Related papers • Yarnal B (1993): Synoptic climatology in environmental analysis. Belhaven Press, London • Comrie AC (1996): An all-season synoptic climatology of air pollution in the U.S.-Mexico border region. Professional Geographer 48(3), 237-251. • Ekström M, Jönsson P & Bärring L (2002): Synoptic pressure patterns associated with major wind erosion events in southern Sweden (1973–1991). Climate Research, 23: 51–66.

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