PRIMARY VALIDATION - RAINFALL DATA DATA VALIDATION *FINAL VALUE STORED IN “HIS” IS BEST REPRESENTATION COMPREHENSIVE MANUAL VALIDATION *PROHIBITIVE IN THE PAST, IF NOT IMPOSSIBLE PRIMARY VALIDATION *SUB-DIV. DPCs USING PRIMARY MODULE *DATA COMPARISON AT SINGLE STATION DATA ENTRY CHECKS ALREADY DONE *TRANSCRIPTION ERRORS REMOVED RAINFALL - HIGH VARIABILITY MORE CHECKS SUBSEQUENTLY *SECONDARY VALIDATION, DIV. DPCs *NEIGHBOURING STATIONS OHS - 1

INSTRUMENTS & OBSERVATIONAL METHODS WHY CERTAIN DATA IS SUSPECT ?? –OBSERVATIONAL PROCESS TO BE KNOWN *METHOD OF MEASUREMENT *TYPICAL ERRORS OF EQUIPMENT USED DATA VALIDATION –NOT A MERE STATISTICAL EXERCISE 3 BASIC EQUIPMENT –STANDARD RAINGAUGE (SRG) –SYPHON TYPE RECORDING RAINGAUGE (ARG) –TIPPING BUCKET RAINAGAUGE (TBR) OHS - 2

SRG INSTRUMENT & PROCEDURE *CIRCULAR COLLECTOR FUNNEL (200 / 100 SQ.CMS) *COLLECTOR BOTTLE *BASE UNIT - PARTLY EMBEDDED –GAUGE READ ONCE OR TWICE IN A DAY *MEASURING GLASS TYPICAL ERRORS *INCORRECT READING OF MEASURING GLASS *RECORDING INCORRECTLY IN THE FIELD SHEET *OBSERVATION AT NON STANDARD TIMES *WRONG MEASURING GLASS *GAUGE RIM DAMAGED, BLOCKAGE/LEAKAGE IN FUNNEL *COLLECTOR BOTTLE NOT PROPER *NON-STANDARD EXPOSURE CONDITIONS OHS - 3

ARG INSTRUMENT & PROCEDURE *CIRCULAR COLLECTOR FUNNEL (324 SQ. CMS) *FLOAT CHAMBER & FLOAT SPINDLE *SYPHON CHAMBER *PEN, CHART, DRUM, CLOCK –CHART IS CHANGED ONCE IN A DAY *TABULATION OF ANALOGUE RECORD TYPICAL ERRORS *BLOCKAGE/LEAKAGE IN FUNNEL *IMPERFECT SYPHONING OR FLOAT MOVEMENT *CLUTTERING IN PEN TRACE FOR HIGH INTENSITY *CLOCK IMPROPER *IMPROPER TABULATION *NON-STANDARD EXPOSURE CONDITIONS OHS - 4

TBR INSTRUMENT & PROCEDURE *CIRCULAR COLLECTOR FUNNEL *TIPPING BUCKET ARRANGEMENT - KNIFE EDGE *REED SWITCH REGISTER EACH TIP *DATA LOGGER –CONTINUOUS RECORDING *PRE-SET TIME INTERVAL OR REGISTER TIPS TYPICAL ERRORS *BLOCKAGE/LEAKAGE IN FUNNEL *BUCKET DAMAGED OR IMBALANCED *REED SWITCH NOT EFFICIENT *NON-STANDARD EXPOSURE CONDITIONS OHS - 5

DATA VALIDATION - INDEPENDENT SOURCES COMPARING DAILY RAINFALL –OBSERVED AT SAME STATION BY SRG AND ARG –MUTUAL DIFFERENCES *CHANGE IN EXPOSURE *INSTRUMENT ACCURACY *PRECISION IN TABULATING ARG CHART *MUST BE LESS THAN 5% –SIGNIFICANT DIFFERENCES BE PROBED FURTHER SRG RECORD - GENERAL MORE RELIABLE ERRORS IN ARG - NORMALLY SYSTEMATIC OHS - 6

OHS - 7

OHS - 8

OHS - 9 SRGARGSRGARGSRGARG

BEWAREBEWARE OHS - 10

SRG - ARG : POSSIBLE SCENARIOS ARG - CONSISTENTLY HIGHER OR LOWER –ARG OUT OF CALIBRATION *ACCEPT SRG AND ADJUST ARG INCREASED DIFFERENCES AT HIGH INTENSITY –ARG WORKING IMPERFECTLY AT HIGH INTENSITY *ACCEPT SRG AND ADJUST ARG ALTERNATE + & - DIFFERENCES –SRG READ AT NON-STANDARD TIMES *ACCEPT ARG AND ADJUST SRG –INCORRECT TABULATION *ACCEPT SRG AND ADJUST ARG HIGH DIFFERENCES ONLY ON ISOLATED DAYS *DATE, TABULATION OR DATA ENTRY ERRORS OHS - 11

CHECKING AGAINST DATA LIMITS MAXIMUM LIMIT –ABSOLUTE MAXIMUM LIMIT *HIGHEST EVER RECORDED *PMP MAPS - 1DAY *50 YEAR - 1HR ISOLINES *GENERAL PERCEPTION / EXPERIENCE –VERY BROAD LIMIT *DEFINES THE BOUNDARY - ALMOST ABSOLUTELY *RARE OCASSIONS!! - NEW MAXIMA EXPERIENCED OHS - 12

OHS - 13

CHECKING AGAINST DATA LIMITS UPPER WARNING LEVEL –OPERATIONAL LIMIT *TO FLAG A FEW HIGH DATA VALUES –DERIVABLE USING SUITABLE STATISTICS *99 %ILE OF NON-ZERO RAINFALL VALUES *1 IN 100 VALUES WILL BE FLAGGED *1 OR 2 VALUES A YEAR (DAILY DATA) –PROVIDES A CROSS CHECK ON DATA ENTRY CHECKS OHS - 14

OHS - 13