186SL0697110121501 033A 19861214 19901230 0126N 12512E 2 00000R 0000 MM 186SL0697210121501 Bitung Indonesia BAKOSURTANAL 186SL069730001 186SL069730002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL069730003 by the 186SL069730004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL069730005 JOINT ARCHIVE FOR SEA LEVEL 186SL069730006 186SL069730007Station : Bitung Latitude: 01 26.4N 186SL069730008Country : Indonesia Longitude: 125 11.6E 186SL069730009JASL # : 033A Time Meridian: 120E (GMT + 8 hr) 186SL069730010GLOSS # : 069 TOGA #: P007 NODC #: 10121501 186SL069730011Contributor : BAKOSURTANAL, Indonesia 186SL069730012 J. Raya Jakarta - Borog Km 46 186SL069730013 P.O. Box 46 Cibinong, Indonesia 186SL069730014Originator : same 186SL069730015Original Data: digital 186SL069730016Instrmnt Type: Fischer and Porter Analog-to-Digital Recorder 186SL069730017Digitzd Intvl: 15 minutes 186SL069730018Present Data : Hourly, daily, and monthly values obtained by: 186SL069730019 Hourly : (pre-1987) Nine-point triangular filter centered 186SL069730020 on the hour with respective periods of the 95, 50, 186SL069730021 and 5% amplitude point of the filter response at 186SL069730022 623.6, 177.0, and 103.7 minutes;(1987+) three-point 186SL069730023 Hanning filter centered on the hour 186SL069730024 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL069730025 centered on noon applied to the hourly data 186SL069730026 with respective periods of the 95, 50, and 5% 186SL069730027 amplitude points at 124.0, 60.2, and 40.2 hours 186SL069730028 Monthly: Simple average of all daily values; calculated if 186SL069730029 7 or fewer days are missing 186SL069730030Span of data : 14 Dec 1986 - 30 Dec 1990 186SL069730031Gaps > 1 mon : none 186SL069730032Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL069730033Units : millimeters Missing Data Flag :99999 186SL069730034Refernce Levl: All heights have been referred to the station tide 186SL069730035 staff zero which is linked to fixed bench marks 186SL069730036Comment : The daily and monthly means reveal no apparent 186SL069730037 changes in the reference level. The residuals 186SL069730038 (observed data minus predicted tides) have 186SL069730039 spikes periodically. However, the installa- 186SL069730040 tion is in a region with complex tides that the 186SL069730041 harmonic analysis can not completely resolve, 186SL069730042 which may explain this spikey signature. The 186SL069730043 timing accuracy appears to be no better than 186SL069730044 plus/minus 8 minutes. 186SL069730045 186SL069730046 CI MISSING REPLACED GAPS QUESTIONABLE 186SL069730047YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL069730048---- --- -------------------- --------------- -------------------- 186SL0697300491986 5 none none none 186SL0697300501987 100 none none none 186SL0697300511988 95 153-158,304-316 none 184-185,197,298,328- 186SL069730052 333,343-351,357-363 186SL0697300531989 97 273-275,282-287, none 6-13,158-160,184- 186SL069730054 333-337,364-365 187,203-204,306, 186SL069730055 347-349 186SL0697300561990 83 1-8,59-65,91-96, none 12-13,40-45,149-150, 186SL069730057 121-124,151-153, 205-206,233-235,294- 186SL069730058 181-183,201-205, 295,306-307,326-327, 186SL069730059 224-232,251-261, 352-356 186SL069730060 275-281,291-293, 186SL069730061 308-312,322-324, 186SL069730062 334-338,365 186SL069730063 186SL069730064 QUALITY ASSESSMENT POLICY 186SL069730065 186SL069730066 The quality assessment is mostly based on the residuals 186SL069730067 (observed data minus predicted tides) of the hourly data. This 186SL069730068 assessment also applies to the daily and monthly data since 186SL069730069 they were derived from the quality-controlled hourly data. 186SL069730070 186SL069730071 The following abbreviations are used in the assessment: 186SL069730072 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL069730073 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL069730074 research program; NODC - National Oceanographic Data Center; 186SL069730075 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL069730076 Gaps > 1 mon - missing data in a span greater than one month; 186SL069730077 Refernce - reference. 186SL069730078 186SL069730079 The following corrections are made to the hourly data 186SL069730080 prior to this assessment: 186SL069730081 1) Gaps or obviously wrong data points in a span less than 186SL069730082 25 hours are filled by the predicted tide method*. 186SL069730083 2) Timing errors of exact increments of an hour are corrected 186SL069730084 by shifting the data. 186SL069730085 3) Reference level shifts are only corrected after information 186SL069730086 from tide staff readings or comparative readings with a fixed 186SL069730087 bench mark are checked to verify that the shift was not a 186SL069730088 natural event. If comparative readings are missing or 186SL069730089 incomplete, comparisons of the data with nearby stations 186SL069730090 may warrant the adjustment of some obvious shifts. 186SL069730091 4) Data with unresolved datum shifts are not disseminated. 186SL069730092 However, if sufficient time spans of data are available before 186SL069730093 or after the year(s) with the unresolved shift(s), a subset of 186SL069730094 quality assured data is made available. Thus, the Span field 186SL069730095 in the Quality Assessment may not match the span of the 186SL069730096 distribution data set. As the questionable datum shifts are 186SL069730097 resolved, the data set will be updated. Although this policy 186SL069730098 adds some complexity, it allows more rapid dissemination of 186SL069730099 at least the quality assured years. 186SL069730100 186SL069730101 For each year, the following information is documented from 186SL069730102 the quality-controlled hourly data with dates given as the nth 186SL069730103 day of the year starting from 1 January: 186SL069730104 1) a Completeness Index (CI) based on the percentage of hours 186SL069730105 with available data, 186SL069730106 2) a list of gaps longer than a day, 186SL069730107 3) a summary of days with consecutive missing or obviously 186SL069730108 wrong data in a time span longer than 6 but less than 25 186SL069730109 hours that have been replaced, with hours in parentheses, and 186SL069730110 4) a summary of days with questionable fluctuations in the 186SL069730111 residual series. Fluctuations within the residuals are 186SL069730112 considered significant and are noted if they are greater than 186SL069730113 25 cm. This policy has changed slightly as of October 1992: 186SL069730114 only suspicious fluctuations due to obvious instrumentation 186SL069730115 problems are noted. Minor timing drifts are no longer 186SL069730116 included in the list of questionable days. 186SL069730117 186SL069730118 Note : If the predicted tides poorly model the observed heights 186SL069730119 due to the inability of the tidal analysis to completely resolv 186SL069730120 the non-linear shallow water effects, the residuals are not 186SL069730121 suitable for assessing the data quality. Instead, a subjective 186SL069730122 comment on the quality of the data is provided. 186SL069730123 186SL069730124 *The predicted tides are obtained with the use of a harmonic 186SL069730125 analysis program (Foreman, 1977) which is executed on a year 186SL069730126 of apparently good data for a given station. The Predicted 186SL069730127 Tide Method for filling gaps consists of statistically 186SL069730128 comparing the predicted tides to the observed data and 186SL069730129 shifting the predicted tides in time to correct for timing 186SL069730130 differences. Then the linear interpolation between hourly 186SL069730131 values at the end points of the gap in the residual series is 186SL069730132 added to the corresponding corrected predicted tide data to 186SL069730133 obtain interpolated values over the span of the gap. 186SL069730134 186SL069730135 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL069730136 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL069730137 186SL069730138 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL069730139 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL069730140 Victoria B.C. Pacific Marine Science Report 77-10. 186SL069730141 186SL06976 19861 999999999999999999999999999999999999999999999999 186SL06976 19862 999999999999999999999999999999999999999999999999 186SL06976 19871 1346000 1402000 1370000 1372000 1360000 1360000 186SL06976 19872 1352000 1328000 1300000 1339000 1386000 1410000 186SL06976 19881 1405000 1424000 1439000 1481000 1466000 1468050 186SL06976 19882 1454000 1463000 1481000 152602099999999 1603010 186SL06976 19891 1552000 1465000 1490000 1542000 1540000 1563000 186SL06976 19892 1515000 1484000 1491010 1545070 1534020 1481050 186SL06976 19901 99999999 1452010 1449060 1460050 1478040 1474020 186SL06976 19902 142205099999999999999999999999999999999 1417050