186SL0903110114701 385A 19870626 19921231 0414N 11753E 2 00000R 0000 MM 186SL0903210114701 Tawau Malaysia Dept. of Survey and Mapping 186SL090330001 186SL090330002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL090330003 by the 186SL090330004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL090330005 JOINT ARCHIVE FOR SEA LEVEL 186SL090330006 186SL090330007Station : Tawau Latitude: 04 14.0N 186SL090330008Country : Malaysia Longitude: 117 53.0E 186SL090330009JASL # : 385A Time Meridian: 120E (GMT + 8 hr) 186SL090330010GLOSS # : none TOGA #: none NODC #: 10114701 186SL090330011Contributor : Dept. of Survey and Mapping 186SL090330012 Jalan Gurney 186SL090330013 50578 Kuala Lumpur, Malaysia 186SL090330014Originator : same 186SL090330015Original Data: digital; samples taken every 10 sec; 50 sec average 186SL090330016Instrmnt Type: Magnetic Tape Type Tide Gauge, Model LLT- 186SL090330017 3AD (Kyowa Shoko Co. LTD, Japan) 186SL090330018Digitzd Intvl: one hour 186SL090330019Present Data : Hourly, daily, and monthly values obtained by: 186SL090330020 Hourly : Five-point least squares approximation (more 186SL090330021 information available from the address above) 186SL090330022 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL090330023 centered on noon applied to the hourly data 186SL090330024 with respective periods of the 95, 50, and 5% 186SL090330025 amplitude points at 124.0, 60.2, and 40.2 hours 186SL090330026 Monthly: Simple average of all daily values; calculated if 186SL090330027 7 or fewer days are missing 186SL090330028Span of data : 26 Jun 1987 - 31 Dec 1992 186SL090330029Gaps > 1 mon : 31 Jan - 05 Mar 1990;07 Jun - 06 Jul 1991; 186SL090330030 03 Aug - 05 Sep 1992 186SL090330031Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL090330032Units : millimeters Missing Data Flag :99999 186SL090330033Refernce Levl: The sea level heights are referred to the zero 186SL090330034 point assigned to the tide gauge. Bench mark 186SL090330035 information is available upon request from the 186SL090330036 contributors. 186SL090330037Comment : A sharp drop of about 15 cm from 30 Sep - 4 Oct, 186SL090330038 1989 is present. The originators report no obvious 186SL090330039 errors. The feature is most likely the result of 186SL090330040 a meteorological or oceanographical event. Periodic 186SL090330041 signatures in the residuals are believed to be due 186SL090330042 to the inability of the harmonic analysis to 186SL090330043 resolve completely some of the tidal constituents. 186SL090330044 Only extreme fluctuations in the residuals are 186SL090330045 noted below which may be due to phase shifts in 186SL090330046 the timing. The daily and monthly values agree 186SL090330047 fairly well with Bitung, Indonesia. 186SL090330048 186SL090330049 CI MISSING REPLACED GAPS QUESTIONABLE 186SL090330050YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL090330051---- --- -------------------- --------------- -------------------- 186SL0903300521987 51 347-350 none none 186SL0903300531988 94 41-62 none none 186SL0903300541989 96 212-214,215-216, (19)174-(03)175 302-304 186SL090330055 238-248,248-252 186SL0903300561990 92 31-64 none 95-99 186SL0903300571991 92 158-187 none none 186SL0903300581992 89 216-249,270-276 none none 186SL090330059 186SL090330060 QUALITY ASSESSMENT POLICY 186SL090330061 186SL090330062 The quality assessment is mostly based on the residuals 186SL090330063 (observed data minus predicted tides) of the hourly data. This 186SL090330064 assessment also applies to the daily and monthly data since 186SL090330065 they were derived from the quality-controlled hourly data. 186SL090330066 186SL090330067 The following abbreviations are used in the assessment: 186SL090330068 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL090330069 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL090330070 research program; NODC - National Oceanographic Data Center; 186SL090330071 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL090330072 Gaps > 1 mon - missing data in a span greater than one month; 186SL090330073 Refernce - reference. 186SL090330074 186SL090330075 The following corrections are made to the hourly data 186SL090330076 prior to this assessment: 186SL090330077 1) Gaps or obviously wrong data points in a span less than 186SL090330078 25 hours are filled by the predicted tide method*. 186SL090330079 2) Timing errors of exact increments of an hour are corrected 186SL090330080 by shifting the data. 186SL090330081 3) Reference level shifts are only corrected after information 186SL090330082 from tide staff readings or comparative readings with a fixed 186SL090330083 bench mark are checked to verify that the shift was not a 186SL090330084 natural event. If comparative readings are missing or 186SL090330085 incomplete, comparisons of the data with nearby stations 186SL090330086 may warrant the adjustment of some obvious shifts. 186SL090330087 4) Data with unresolved datum shifts are not disseminated. 186SL090330088 However, if sufficient time spans of data are available before 186SL090330089 or after the year(s) with the unresolved shift(s), a subset of 186SL090330090 quality assured data is made available. Thus, the Span field 186SL090330091 in the Quality Assessment may not match the span of the 186SL090330092 distribution data set. As the questionable datum shifts are 186SL090330093 resolved, the data set will be updated. Although this policy 186SL090330094 adds some complexity, it allows more rapid dissemination of 186SL090330095 at least the quality assured years. 186SL090330096 186SL090330097 For each year, the following information is documented from 186SL090330098 the quality-controlled hourly data with dates given as the nth 186SL090330099 day of the year starting from 1 January: 186SL090330100 1) a Completeness Index (CI) based on the percentage of hours 186SL090330101 with available data, 186SL090330102 2) a list of gaps longer than a day, 186SL090330103 3) a summary of days with consecutive missing or obviously 186SL090330104 wrong data in a time span longer than 6 but less than 25 186SL090330105 hours that have been replaced, with hours in parentheses, and 186SL090330106 4) a summary of days with questionable fluctuations in the 186SL090330107 residual series. Fluctuations within the residuals are 186SL090330108 considered significant and are noted if they are greater than 186SL090330109 25 cm. This policy has changed slightly as of October 1992: 186SL090330110 only suspicious fluctuations due to obvious instrumentation 186SL090330111 problems are noted. Minor timing drifts are no longer 186SL090330112 included in the list of questionable days. 186SL090330113 186SL090330114 Note : If the predicted tides poorly model the observed heights 186SL090330115 due to the inability of the tidal analysis to completely resolv 186SL090330116 the non-linear shallow water effects, the residuals are not 186SL090330117 suitable for assessing the data quality. Instead, a subjective 186SL090330118 comment on the quality of the data is provided. 186SL090330119 186SL090330120 *The predicted tides are obtained with the use of a harmonic 186SL090330121 analysis program (Foreman, 1977) which is executed on a year 186SL090330122 of apparently good data for a given station. The Predicted 186SL090330123 Tide Method for filling gaps consists of statistically 186SL090330124 comparing the predicted tides to the observed data and 186SL090330125 shifting the predicted tides in time to correct for timing 186SL090330126 differences. Then the linear interpolation between hourly 186SL090330127 values at the end points of the gap in the residual series is 186SL090330128 added to the corresponding corrected predicted tide data to 186SL090330129 obtain interpolated values over the span of the gap. 186SL090330130 186SL090330131 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL090330132 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL090330133 186SL090330134 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL090330135 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL090330136 Victoria B.C. Pacific Marine Science Report 77-10. 186SL090330137 186SL09036 19871 999999999999999999999999999999999999999999999999 186SL09036 19872 2633000 2640000 2643000 2667000 2699000 2677040 186SL09036 19881 267900099999999 2738020 2728000 2725000 2716000 186SL09036 19882 2702000 2730000 2791000 2798000 2767000 2762000 186SL09036 19891 2750000 2713000 2753000 2772000 2765000 2745000 186SL09036 19892 27670109999999999999999 2737000 2730000 2664000 186SL09036 19901 266401099999999 2643050 2672000 2664000 2694000 186SL09036 19902 2648000 2677000 2687000 2670000 2646000 2637000 186SL09036 19911 2624000 2642000 2672000 2673000 266800099999999 186SL09036 19912 2640060 2633000 2645000 2643000 2616000 2611000 186SL09036 19921 2581000 2619000 2627000 2656000 2663000 2671000 186SL09036 19922 26460009999999999999999 2720020 2723000 2633000