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SECONDARY VALIDATION - RAINFALL DATA PowerPoint Presentation
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SECONDARY VALIDATION - RAINFALL DATA

SECONDARY VALIDATION - RAINFALL DATA

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SECONDARY VALIDATION - RAINFALL DATA

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  1. SECONDARY VALIDATION - RAINFALL DATA • PRIMARY VALIDATION ALREADY DONE • ON INDIVIDUAL STATION BASIS • SECONDARY VALIDATION • IDENTIFY SUSPECT VALUES BY HAVING COMPARISON WITH NEIGHBOURING STATIONS • DIVISIONAL DPCs • TO CONTINUE AT SDPCs • RAINFALL NOT HIGHLY CORRELATED IN SPACE & TIME !! • NOT A ONE-TO-ONE - COMPARISON DIFFICULT • BETTER CORRELATION - LARGER TIME INTERVALS • MISTAKES & SUSTAINED SYSTEMATIC ERRORS OHS - 1

  2. SPATIAL CORRELATION • MAJOR INFLUENCING FACTORS • LEVEL OF AGGREGATION IN TIME • DISTANCE • TYPE OF PRECIPITATION • PHYSIOGRAPHIC FACTORS OHS - 2

  3. KHEDA CATCHMENT - SABARMATI OHS - 3

  4. OHS - 4

  5. OHS - 5

  6. OHS - 6

  7. OHS - 7

  8. REGION A OHS - 8

  9. OHS - 9

  10. EXTENDED REGION OHS - 10

  11. USE OF SPATIAL CORRELATION • PREVAILING SPATIAL CORRELATION • AS BASIS FOR TESTING SPATIAL CONSISTENCY • SPATIAL INTERPOLATION • THERE IS LIKELIHOOD OF • REJECTING GOOD BUT ANAMOLOUS DATA • ACCEPTING BAD DATA • RELIANCE ON STATION REPUTATION • TYPE OF STATION • PAST RECORD ON QUALITY • OBSERVER SINCERITY & PAST RECORDS OHS - 11

  12. SECONDARY DATA VALIDATION • SCREENING OF DATA • MULTIPLE TIME SERIES GRAPHS • DAILY RAINFALL TABULATION FOR NEIGHBOURING STATIONS • APPLYING DATA LIMITS AT LONGER DURATIONS • SPATIAL HOMOGENEITY TEST • VERY COMMON ERRORS • ACCUMULATION OF RAINFALL OR MISSED ENTRY • MISSED RAINFALL ON LOW RAINFALL DAYS • DOUBLE MASS ANALYSIS • LONG TERM SYSTEMATIC SHIFTS OHS - 12

  13. DATA VALIDATION • SCREENING OF DATA • SCREENING AGAINST DATA LIMITS • TABULAR OUTPUT • BASIC STATISTICS • OBJECTIVES • REVIEW PRIMARY VALIDATION • HARD COPY • MEDIUM FOR SCRIBBLING REMARKS/ DATA VALIDATION NOTES OHS - 13

  14. OHS - 14

  15. OHS - 15

  16. OHS - 16

  17. SCRUTINY BY TABULATION OHS - 17

  18. OHS - 18

  19. SPATIAL HOMOGENEITY TESTING • SPATIAL CORRELATION • CONSISTENCY BETWEEN NEIGHBOURING STATIONS • COMPARISON OF • OBSERVED VALUE • VALUE ESTIMATED ON THE BASIS OF NEARBY STATIONS OHS - 19

  20. I + II Test station + + + + Neighbouring stations + Selected neighbouring stations + + + + II etc. + Quadrant + + + + + IV III + TEST & BASE (NEIGHBOUR) STATIONS OHS - 20

  21. SPATIAL ESTIMATE - WEIGHTED AVERAGE • WEIGHTS : INVERSE OF DISTANCE POWER • TEST : ABSOLUTE & RELATIVE OHS - 21

  22. OHS - 22

  23. OHS - 23

  24. COMMON ERRORS - SHIFT IN ENTRIES OHS - 24

  25. OHS - 25

  26. COMMON ERRORS - ACCUMULATIONS • RAINFALL OBSERVATIONS • TO BE MADE DAILY WITHOUT FAIL • ABSENCE DUE TO PRACTICAL REASONS • SICKNESS • HOLIDAY(S)/WEEKENDS • OBSERVERS TENDENCY • DISTRIBUTE RAINFALL BASED ON OWN GUESS • RECORD ACCUMULATED VALUE ON THE LAST DAY WITHOUT MENTIONING IT • RECORD ACCUMULATED VALUE ON THE LAST DAY WITH PROPER REMARKS (NOT PRACTICED NORMALLY) • DETECTION OF SUCH ERRORS • USING RECORDS OF NEARBY STATIONS OHS - 26

  27. OHS - 27

  28. OHS - 28

  29. COMMON ERRORS - MISSED ENTRIES OHS - 29

  30. OHS - 30

  31. DOUBLE MASS ANALYSIS • DETECTION OF SYSTEMATIC SHIFTS IN TIME • PERSISTENCE FOR LONG TIME PERIODS • ABRUPT OR GRADUAL CHANGE • TEMPORAL INCONSISTENCY: FACTORS • SHIFTING OF STATION TO ANOTHER LOCATION • CHANGE IN EXPOSURE CONDITION • CHANGE IN EQUIPMENT OR PRACTICES • UNATTENDED FAULT IN EQUIPMENT • CHANGE IN REGIME: MAN-MADE TOO • IN-HOMOGENEITY IN DATA SET • NOT ACCEPTABLE IN STATISTICAL ANALYSIS • RELATING SERIES TO DESIRED SITE/REGIME OHS - 31

  32. DETECTION OF INHOMOGENEITY • COMPARING BEHAVIOUR OF TEST STATION WITH RESPECT TO NEARBY STATIONS • BASE STATION(S) ASSUMED TO HOMOGENEOUS • ANY SIGNIFICANT & PERSISTENT DIFFERENCES IN MUTUAL RELATIONSHIP INDICATES SHIFT • RANDOM VARIATION IN RELATIONSHIP TEND TO COMPENSATE IF AGGREGATED IN TIME • SYSTEMATIC VARIATION TENDS TO SHOW UP OHS - 32

  33. DOUBLE MASS CURVE • SIMPLE TEST PROCEDURE • ACCUMULATE IN TIME • OBSEREVED TEST SERIES • ESTIMATED BASE SERIES • COMPARE THE TWO ACCUMULATED SERIES • SIGNIFICANT & PERSISTENT DEVIATION SHOWS IN-HOMOGENEITY IN THE TEST SERIES OHS - 33

  34. OHS - 34

  35. OHS - 35