186SL0817153073801 021B 19850904 19881231 3337S 07850W 2 00000R 0000 MM 186SL0817253073801 Juan Fernandez-B Chile SHOA 186SL081730001 186SL081730002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL081730003 by the 186SL081730004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL081730005 JOINT ARCHIVE FOR SEA LEVEL 186SL081730006 186SL081730007Station : Juan Fernandez-B Latitude: 33 37.3S 186SL081730008Country : Chile Longitude: 078 50.0W 186SL081730009JASL # : 021B Time Meridian: 060W (GMT - 4 hr) 186SL081730010GLOSS # : 176 TOGA #: P086 NODC #: 53073801 186SL081730011Contributor : Servicio Hidrografico y Oceanografico de la 186SL081730012 Armada (SHOA) 186SL081730013 Casilla 324 186SL081730014 Valparaiso, Chile 186SL081730015Originator : same 186SL081730016Original Data: analog 186SL081730017Instrmnt Type: Metercraft bubbler gauge 186SL081730018Digitzd Intvl: one hour 186SL081730019Present Data : Hourly, daily, and monthly values obtained by: 186SL081730020 Hourly : The original digitizing interval was hourly 186SL081730021 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL081730022 centered on noon applied to the hourly data 186SL081730023 with respective periods of the 95, 50, and 5% 186SL081730024 amplitude points at 124.0, 60.2, and 40.2 hours 186SL081730025 Monthly: Simple average of all daily values; calculated if 186SL081730026 7 or fewer days are missing 186SL081730027Span of data : 04 Sep 1985 - 31 Dec 1989 186SL081730028Gaps > 1 mon : 20 Aug 1986 - 18 Sep 1987 186SL081730029Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL081730030Units : millimeters Missing Data Flag :99999 186SL081730031Refernce Levl: The tide staff zero has been linked to fixed bench 186SL081730032 marks by the contributors. The documentation 186SL081730033 shows the tide staff to be stable relative to the 186SL081730034 bench marks through out the period. However, the 186SL081730035 data reveal numerous level shifts between 186SL081730036 02 Apr - 31 Dec 1989. After investigation by 186SL081730037 the originators into the tide staff readings 186SL081730038 and original analog rolls, it has been determined 186SL081730039 that these shifts are not correctable. 186SL081730040Comment : This data set is of marginal quality due to the 186SL081730041 numerous gaps and reference level shifts. 186SL081730042 186SL081730043 186SL081730044 CI MISSING REPLACED GAPS QUESTIONABLE 186SL081730045YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL081730046---- --- -------------------- --------------- -------------------- 186SL0817300471985 31 314-315,318-322 (06)266-(15)266 none 186SL081730048 (14)360-(13)361 186SL0817300491986 63 53-55,77-78, (14)006-(11)007 32,43-44 186SL081730050 233-365 (19)032-(14)033 186SL081730051 (14)072-(13)073 186SL081730052 (16)088-(14)089 186SL081730053 (15)099-(13)100 186SL081730054 (15)123-(13)124 186SL081730055 (07)177-(14)177 186SL0817300561987 28 1-261,357-358 (20)288-(14)289 none 186SL081730057 (16)334-(23)334 186SL081730058 (01)335-(12)335 186SL081730059 (04)365-(15)365 186SL0817300601988 98 82-84,106-109, (17)028-(14)029 none 186SL081730061 130-131,261-262 (20)043-(13)044 186SL081730062 (03)061-(12)061 186SL081730063 (21)135-(20)136 186SL081730064 (16)199-(12)200 186SL081730065 (14)263-(22)263 186SL081730066 (19)264-(03)265 186SL081730067 (00)273-(12)273 186SL081730068 (16)274-(23)274 186SL081730069 (01)275-(15)275 186SL0817300701989 93 47-49,237-238, (03)032-(12)032 122,245-246,257, 186SL081730071 286-289,294-312, (22)039-(12)040 259,262-263,270- 186SL081730072 365 (22)041-(13)042 271,318,322-328 186SL081730073 (00)043-(15)043 186SL081730074 (20)051-(13)052 186SL081730075 (15)091-(14)092 186SL081730076 (17)096-(14)097 186SL081730077 (04)185-(20)185 186SL081730078 (04)244-(14)244 186SL081730079 186SL081730080 QUALITY ASSESSMENT POLICY 186SL081730081 186SL081730082 The quality assessment is mostly based on the residuals 186SL081730083 (observed data minus predicted tides) of the hourly data. This 186SL081730084 assessment also applies to the daily and monthly data since 186SL081730085 they were derived from the quality-controlled hourly data. 186SL081730086 186SL081730087 The following abbreviations are used in the assessment: 186SL081730088 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL081730089 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL081730090 research program; NODC - National Oceanographic Data Center; 186SL081730091 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL081730092 Gaps > 1 mon - missing data in a span greater than one month; 186SL081730093 Refernce - reference. 186SL081730094 186SL081730095 The following corrections are made to the hourly data 186SL081730096 prior to this assessment: 186SL081730097 1) Gaps or obviously wrong data points in a span less than 186SL081730098 25 hours are filled by the predicted tide method*. 186SL081730099 2) Timing errors of exact increments of an hour are corrected 186SL081730100 by shifting the data. 186SL081730101 3) Reference level shifts are only corrected after information 186SL081730102 from tide staff readings or comparative readings with a fixed 186SL081730103 bench mark are checked to verify that the shift was not a 186SL081730104 natural event. If comparative readings are missing or 186SL081730105 incomplete, comparisons of the data with nearby stations 186SL081730106 may warrant the adjustment of some obvious shifts. 186SL081730107 4) Data with unresolved datum shifts are not disseminated. 186SL081730108 However, if sufficient time spans of data are available before 186SL081730109 or after the year(s) with the unresolved shift(s), a subset of 186SL081730110 quality assured data is made available. Thus, the Span field 186SL081730111 in the Quality Assessment may not match the span of the 186SL081730112 distribution data set. As the questionable datum shifts are 186SL081730113 resolved, the data set will be updated. Although this policy 186SL081730114 adds some complexity, it allows more rapid dissemination of 186SL081730115 at least the quality assured years. 186SL081730116 186SL081730117 For each year, the following information is documented from 186SL081730118 the quality-controlled hourly data with dates given as the nth 186SL081730119 day of the year starting from 1 January: 186SL081730120 1) a Completeness Index (CI) based on the percentage of hours 186SL081730121 with available data, 186SL081730122 2) a list of gaps longer than a day, 186SL081730123 3) a summary of days with consecutive missing or obviously 186SL081730124 wrong data in a time span longer than 6 but less than 25 186SL081730125 hours that have been replaced, with hours in parentheses, and 186SL081730126 4) a summary of days with questionable fluctuations in the 186SL081730127 residual series. Fluctuations within the residuals are 186SL081730128 considered significant and are noted if they are greater than 186SL081730129 25 cm. This policy has changed slightly as of October 1992: 186SL081730130 only suspicious fluctuations due to obvious instrumentation 186SL081730131 problems are noted. Minor timing drifts are no longer 186SL081730132 included in the list of questionable days. 186SL081730133 186SL081730134 Note : If the predicted tides poorly model the observed heights 186SL081730135 due to the inability of the tidal analysis to completely resolv 186SL081730136 the non-linear shallow water effects, the residuals are not 186SL081730137 suitable for assessing the data quality. Instead, a subjective 186SL081730138 comment on the quality of the data is provided. 186SL081730139 186SL081730140 *The predicted tides are obtained with the use of a harmonic 186SL081730141 analysis program (Foreman, 1977) which is executed on a year 186SL081730142 of apparently good data for a given station. The Predicted 186SL081730143 Tide Method for filling gaps consists of statistically 186SL081730144 comparing the predicted tides to the observed data and 186SL081730145 shifting the predicted tides in time to correct for timing 186SL081730146 differences. Then the linear interpolation between hourly 186SL081730147 values at the end points of the gap in the residual series is 186SL081730148 added to the corresponding corrected predicted tide data to 186SL081730149 obtain interpolated values over the span of the gap. 186SL081730150 186SL081730151 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL081730152 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL081730153 186SL081730154 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL081730155 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL081730156 Victoria B.C. Pacific Marine Science Report 77-10. 186SL081730157 186SL08176 19851 999999999999999999999999999999999999999999999999 186SL08176 19852 9999999999999999 2257040 2280000 2307070 2322000 186SL08176 19861 2352000 2350030 2426020 2498000 2563000 2464000 186SL08176 19862 24680009999999999999999999999999999999999999999 186SL08176 19871 999999999999999999999999999999999999999999999999 186SL08176 19872 999999999999999999999999 2370000 2366000 2405020 186SL08176 19881 2521000 2560000 2565030 2566040 2551020 2513000 186SL08176 19882 2488000 2476000 2416020 2489000 2501000 2579000