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SECONDARY VALIDATION - RAINFALL DATA

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 !!

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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

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