186SL0759110101304 327A 19820101 19881231 0116N 10349E 2 00000R 0000 MM 186SL0759210101304 Keppel Harbour Singapore Port of Singapore Authority 186SL075930001 186SL075930002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL075930003 by the 186SL075930004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL075930005 JOINT ARCHIVE FOR SEA LEVEL 186SL075930006 186SL075930007Station : Keppel Harbour Latitude: 01 15.8N 186SL075930008Country : Singapore Longitude: 103 49.3E 186SL075930009JASL # : 327A Time Meridian: 120E (GMT + 8 hr) 186SL075930010GLOSS # : 044 TOGA #: none NODC #: 10101304 186SL075930011Contributor : Port of Singapore Authority 186SL075930012 PSA Building 186SL075930013 460 Alexandra Road 186SL075930014 Singapore 0511 186SL075930015Originator : same 186SL075930016Original Data: analog 186SL075930017Instrmnt Type: A.OTT Float Type 186SL075930018Digitzd Intvl: 1 hour 186SL075930019Present Data : Hourly, daily, and monthly values obtained by: 186SL075930020 Hourly : digitized from chart paper 186SL075930021 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL075930022 centered on noon applied to the hourly data 186SL075930023 with respective periods of the 95, 50, and 5% 186SL075930024 amplitude points at 124.0, 60.2, and 40.2 hours 186SL075930025 Monthly: Simple average of all daily values; calculated if 186SL075930026 7 or fewer days are missing 186SL075930027Span of data : 01 Jan 1982 - 31 Dec 1988 186SL075930028Gaps > 1 mon : none 186SL075930029Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL075930030Units : millimeters Missing Data Flag :99999 186SL075930031Refernce Levl: The sea level heights are referred to the chart 186SL075930032 datum which is also the zero level of the tide 186SL075930033 gauge. Bench mark information is available upon 186SL075930034 request from the contributors. 186SL075930035Comment : The residual series are very noisy, which is 186SL075930036 probably due to shallow water tides that are not 186SL075930037 resolved by the harmonic analysis or due to timing 186SL075930038 drifts of less than 15 minutes. The daily and 186SL075930039 monthly means of Keppel Harbour agree well with 186SL075930040 a nearby station, Johor Baharu. No reference level 186SL075930041 shifts are apparent; however, there appears to be 186SL075930042 an upward trend. 186SL075930043 186SL075930044 CI MISSING REPLACED GAPS QUESTIONABLE 186SL075930045YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL075930046---- --- -------------------- --------------- -------------------- 186SL0759300471982 100 none (11)118-(22)118 see comment above 186SL0759300481983 96 350-365 none " " " 186SL0759300491984 100 none none " " " 186SL0759300501985 100 none none " " " 186SL0759300511986 100 none none " " " 186SL0759300521987 100 none (16)265-(15)266 " " " 186SL0759300531988 94 89-93,291-299, none " " " 186SL075930054 328-336,366 186SL075930055 186SL075930056 QUALITY ASSESSMENT POLICY 186SL075930057 186SL075930058 The quality assessment is mostly based on the residuals 186SL075930059 (observed data minus predicted tides) of the hourly data. This 186SL075930060 assessment also applies to the daily and monthly data since 186SL075930061 they were derived from the quality-controlled hourly data. 186SL075930062 186SL075930063 The following abbreviations are used in the assessment: 186SL075930064 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL075930065 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL075930066 research program; NODC - National Oceanographic Data Center; 186SL075930067 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL075930068 Gaps > 1 mon - missing data in a span greater than one month; 186SL075930069 Refernce - reference. 186SL075930070 186SL075930071 The following corrections are made to the hourly data 186SL075930072 prior to this assessment: 186SL075930073 1) Gaps or obviously wrong data points in a span less than 186SL075930074 25 hours are filled by the predicted tide method*. 186SL075930075 2) Timing errors of exact increments of an hour are corrected 186SL075930076 by shifting the data. 186SL075930077 3) Reference level shifts are only corrected after information 186SL075930078 from tide staff readings or comparative readings with a fixed 186SL075930079 bench mark are checked to verify that the shift was not a 186SL075930080 natural event. If comparative readings are missing or 186SL075930081 incomplete, comparisons of the data with nearby stations 186SL075930082 may warrant the adjustment of some obvious shifts. 186SL075930083 4) Data with unresolved datum shifts are not disseminated. 186SL075930084 However, if sufficient time spans of data are available before 186SL075930085 or after the year(s) with the unresolved shift(s), a subset of 186SL075930086 quality assured data is made available. Thus, the Span field 186SL075930087 in the Quality Assessment may not match the span of the 186SL075930088 distribution data set. As the questionable datum shifts are 186SL075930089 resolved, the data set will be updated. Although this policy 186SL075930090 adds some complexity, it allows more rapid dissemination of 186SL075930091 at least the quality assured years. 186SL075930092 186SL075930093 For each year, the following information is documented from 186SL075930094 the quality-controlled hourly data with dates given as the nth 186SL075930095 day of the year starting from 1 January: 186SL075930096 1) a Completeness Index (CI) based on the percentage of hours 186SL075930097 with available data, 186SL075930098 2) a list of gaps longer than a day, 186SL075930099 3) a summary of days with consecutive missing or obviously 186SL075930100 wrong data in a time span longer than 6 but less than 25 186SL075930101 hours that have been replaced, with hours in parentheses, and 186SL075930102 4) a summary of days with questionable fluctuations in the 186SL075930103 residual series. Fluctuations within the residuals are 186SL075930104 considered significant and are noted if they are greater than 186SL075930105 25 cm. This policy has changed slightly as of October 1992: 186SL075930106 only suspicious fluctuations due to obvious instrumentation 186SL075930107 problems are noted. Minor timing drifts are no longer 186SL075930108 included in the list of questionable days. 186SL075930109 186SL075930110 Note : If the predicted tides poorly model the observed heights 186SL075930111 due to the inability of the tidal analysis to completely resolv 186SL075930112 the non-linear shallow water effects, the residuals are not 186SL075930113 suitable for assessing the data quality. Instead, a subjective 186SL075930114 comment on the quality of the data is provided. 186SL075930115 186SL075930116 *The predicted tides are obtained with the use of a harmonic 186SL075930117 analysis program (Foreman, 1977) which is executed on a year 186SL075930118 of apparently good data for a given station. The Predicted 186SL075930119 Tide Method for filling gaps consists of statistically 186SL075930120 comparing the predicted tides to the observed data and 186SL075930121 shifting the predicted tides in time to correct for timing 186SL075930122 differences. Then the linear interpolation between hourly 186SL075930123 values at the end points of the gap in the residual series is 186SL075930124 added to the corresponding corrected predicted tide data to 186SL075930125 obtain interpolated values over the span of the gap. 186SL075930126 186SL075930127 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL075930128 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL075930129 186SL075930130 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL075930131 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL075930132 Victoria B.C. Pacific Marine Science Report 77-10. 186SL075930133 186SL07596 19821 1596000 1529000 1500000 1524000 1469000 1445000 186SL07596 19822 1427000 1433000 1455000 1514000 1534000 1627000 186SL07596 19831 1597000 1466000 1515000 1509000 1483000 1482000 186SL07596 19832 1466000 1478000 1496000 1575000 172200099999999 186SL07596 19841 1660000 1619000 1579000 1524000 1558000 1512000 186SL07596 19842 1515000 1505000 1571000 1627000 1681000 1702000 186SL07596 19851 1624000 1600000 1646000 1536000 1534000 1508000 186SL07596 19852 1516000 1476000 1530000 1575000 1647000 1701000 186SL07596 19861 1717000 1581000 1617000 1549000 1550000 1537000 186SL07596 19862 1520000 1533000 1568000 1624000 1722000 1705000 186SL07596 19871 1702000 1608000 1529000 1509000 1503000 1506000 186SL07596 19872 1512000 1514000 1519000 1590000 1661000 1839000 186SL07596 19881 1687000 1636000 1620030 1590020 1532000 1528000 186SL07596 19882 1534000 1550000 15590009999999999999999 1759020