186SL0789132050701 103B 19640301 19651231 2009S 05729E 2 00000R 0000 MM 186SL0789232050701 Port Louis-B Mauritius Inst. Ocean. Science 186SL078930001 186SL078930002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL078930003 by the 186SL078930004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL078930005 JOINT ARCHIVE FOR SEA LEVEL 186SL078930006 186SL078930007Station : Port Louis-B Latitude: 20 09.2S 186SL078930008Country : Mauritius Longitude: 057 29.4E 186SL078930009JASL # : 103B Time Meridian: 060E (GMT + 4 hr) 186SL078930010GLOSS # : 018 TOGA #: I057 NODC #: 32050701 186SL078930011Contributor : Institute of Oceanographic Sciences (IOS) 186SL078930012 Bidston Observatory, Birkenhead 186SL078930013 Merseyside L43 7RA 186SL078930014Originator : same 186SL078930015Original Data: analog 186SL078930016Instrmnt Type: Munroe, float and stilling well 186SL078930017Digitzd Intvl: one hour spot reading 186SL078930018Present Data : Hourly, daily, and monthly values obtained by: 186SL078930019 Hourly : The original digitizing interval was hourly 186SL078930020 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL078930021 centered on noon applied to the hourly data 186SL078930022 with respective periods of the 95, 50, and 5% 186SL078930023 amplitude points at 124.0, 60.2, and 40.2 hours 186SL078930024 Monthly: Simple average of all daily values; calculated if 186SL078930025 7 or fewer days are missing 186SL078930026Span of data : 01 Mar 1964 - 31 Dec 1965 186SL078930027Gaps > 1 mon : none 186SL078930028Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL078930029Units : millimeters Missing Data Flag :99999 186SL078930030Refernce Levl: The sea level heights are referred to the zero 186SL078930031 point assigned to the tide gauge. 186SL078930032Comment : The daily or monthly means do not reveal any 186SL078930033 obvious reference level changes or trends. 186SL078930034 186SL078930035 CI MISSING REPLACED GAPS QUESTIONABLE 186SL078930036YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL078930037---- --- -------------------- --------------- -------------------- 186SL0789300381964 74 86-91,102-104, none 76-78,118-119,173 186SL078930039 157-159,219-223, 186SL078930040 227-229,251-254, 186SL078930041 256-260,263-266, 186SL078930042 270-272,277-279, 186SL078930043 304-306,309-311, 186SL078930044 354-356 186SL0789300451965 83 10-12,13-15,18- (20)224-(19)225 18,135-137,211-212, 186SL078930046 20,32-35,51-53, (20)238-(19)239 243,296 186SL078930047 57-61,86-88, (20)258-(19)259 186SL078930048 114-116,121-123, 186SL078930049 138-140,145-147, 186SL078930050 156-158,162-164, 186SL078930051 167-169,177-182, 186SL078930052 183-186,196-200, 186SL078930053 212-214,219-221, 186SL078930054 233-236,268-270, 186SL078930055 310-312,345-348, 186SL078930056 352-354,358-360, 186SL078930057 365 186SL078930058 186SL078930059 QUALITY ASSESSMENT POLICY 186SL078930060 186SL078930061 The quality assessment is mostly based on the residuals 186SL078930062 (observed data minus predicted tides) of the hourly data. This 186SL078930063 assessment also applies to the daily and monthly data since 186SL078930064 they were derived from the quality-controlled hourly data. 186SL078930065 186SL078930066 The following abbreviations are used in the assessment: 186SL078930067 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL078930068 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL078930069 research program; NODC - National Oceanographic Data Center; 186SL078930070 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL078930071 Gaps > 1 mon - missing data in a span greater than one month; 186SL078930072 Refernce - reference. 186SL078930073 186SL078930074 The following corrections are made to the hourly data 186SL078930075 prior to this assessment: 186SL078930076 1) Gaps or obviously wrong data points in a span less than 186SL078930077 25 hours are filled by the predicted tide method*. 186SL078930078 2) Timing errors of exact increments of an hour are corrected 186SL078930079 by shifting the data. 186SL078930080 3) Reference level shifts are only corrected after information 186SL078930081 from tide staff readings or comparative readings with a fixed 186SL078930082 bench mark are checked to verify that the shift was not a 186SL078930083 natural event. If comparative readings are missing or 186SL078930084 incomplete, comparisons of the data with nearby stations 186SL078930085 may warrant the adjustment of some obvious shifts. 186SL078930086 4) Data with unresolved datum shifts are not disseminated. 186SL078930087 However, if sufficient time spans of data are available before 186SL078930088 or after the year(s) with the unresolved shift(s), a subset of 186SL078930089 quality assured data is made available. Thus, the Span field 186SL078930090 in the Quality Assessment may not match the span of the 186SL078930091 distribution data set. As the questionable datum shifts are 186SL078930092 resolved, the data set will be updated. Although this policy 186SL078930093 adds some complexity, it allows more rapid dissemination of 186SL078930094 at least the quality assured years. 186SL078930095 186SL078930096 For each year, the following information is documented from 186SL078930097 the quality-controlled hourly data with dates given as the nth 186SL078930098 day of the year starting from 1 January: 186SL078930099 1) a Completeness Index (CI) based on the percentage of hours 186SL078930100 with available data, 186SL078930101 2) a list of gaps longer than a day, 186SL078930102 3) a summary of days with consecutive missing or obviously 186SL078930103 wrong data in a time span longer than 6 but less than 25 186SL078930104 hours that have been replaced, with hours in parentheses, and 186SL078930105 4) a summary of days with questionable fluctuations in the 186SL078930106 residual series. Fluctuations within the residuals are 186SL078930107 considered significant and are noted if they are greater than 186SL078930108 25 cm. This policy has changed slightly as of October 1992: 186SL078930109 only suspicious fluctuations due to obvious instrumentation 186SL078930110 problems are noted. Minor timing drifts are no longer 186SL078930111 included in the list of questionable days. 186SL078930112 186SL078930113 Note : If the predicted tides poorly model the observed heights 186SL078930114 due to the inability of the tidal analysis to completely resolv 186SL078930115 the non-linear shallow water effects, the residuals are not 186SL078930116 suitable for assessing the data quality. Instead, a subjective 186SL078930117 comment on the quality of the data is provided. 186SL078930118 186SL078930119 *The predicted tides are obtained with the use of a harmonic 186SL078930120 analysis program (Foreman, 1977) which is executed on a year 186SL078930121 of apparently good data for a given station. The Predicted 186SL078930122 Tide Method for filling gaps consists of statistically 186SL078930123 comparing the predicted tides to the observed data and 186SL078930124 shifting the predicted tides in time to correct for timing 186SL078930125 differences. Then the linear interpolation between hourly 186SL078930126 values at the end points of the gap in the residual series is 186SL078930127 added to the corresponding corrected predicted tide data to 186SL078930128 obtain interpolated values over the span of the gap. 186SL078930129 186SL078930130 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL078930131 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL078930132 186SL078930133 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL078930134 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL078930135 Victoria B.C. Pacific Marine Science Report 77-10. 186SL078930136 186SL07896 19641 9999999999999999 3294070 3380030 3362000 3332030 186SL07896 19642 33220009999999999999999 3332050 3423040 3438030 186SL07896 19651 9999999999999999 3404050 34220309999999999999999 186SL07896 19652 9999999999999999 3296030 3348000 340403099999999