186SL0945171100901 391B 19860421 19881021 1017N 10913W 2 00000R 0000 MM 186SL0945271100901 Clipperton-B France NOAA/PMEL 186SL094530001 186SL094530002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL094530003 by the 186SL094530004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL094530005 JOINT ARCHIVE FOR SEA LEVEL 186SL094530006 186SL094530007Station : Clipperton-B Latitude: 10 16.8N 186SL094530008Country : France Longitude: 109 13.3W 186SL094530009JASL # : 391B Time Meridian: 105W (GMT - 7 hr) 186SL094530010GLOSS # : 165 TOGA #: P070 NODC #: 71100901 186SL094530011Contributor : NOAA/PMEL 186SL094530012 7600 Sand Point Way NE 186SL094530013 Seattle, WA 98115-0070 186SL094530014Originator : same 186SL094530015Original Data: unconfirmed 186SL094530016Instrmnt Type: unconfirmed 186SL094530017Digitzd Intvl: unconfirmed 186SL094530018Present Data : Hourly, daily, and monthly values obtained by: 186SL094530019 Hourly : unconfirmed 186SL094530020 Daily : unconfirmed 186SL094530021 Monthly: Simple average of all daily values; calculated if 186SL094530022 7 or fewer days are missing 186SL094530023Span of data : 21 Apr 1986 - 21 Oct 1988 186SL094530024Gaps > 1 mon : none 186SL094530025Time Refernce: GMT (00-23 hours) Space-filler Flag :-9999 186SL094530026Units : millimeters Missing Data Flag :99999 186SL094530027Refernce Levl: Due to the nature of the bottom-mounted pressure 186SL094530028 gauges, no link could be established between the 186SL094530029 zero of the gauge values and fixed points on land. 186SL094530030 Also, tide staff observations or the like were 186SL094530031 unavailable. This series has no long-term 186SL094530032 reference level. 186SL094530033Comment : The depth of the instrument in the water was 186SL094530034 unconfirmed. Techniques of data processing 186SL094530035 by the originator are unconfirmed. Only daily 186SL094530036 data received at the TOGA Sea Level Center. 186SL094530037 186SL094530038 The short period variations appear reasonable 186SL094530039 however there appears to be a positive trend. 186SL094530040 186SL094530041 Originator indicates no trend removed from 186SL094530042 the series. 186SL094530043 186SL094530044 Due to the tendency for pressure gauge sensors 186SL094530045 to drift, it is beneficial for investigators 186SL094530046 to know the time span of each instrument 186SL094530047 deployment. However, this information was 186SL094530048 not supplied. Thus it is assumed that the 186SL094530049 time span above represents the span of a 186SL094530050 single instrument deployment. 186SL094530051 186SL094530052 CI MISSING REPLACED GAPS QUESTIONABLE 186SL094530053YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL094530054---- --- -------------------- --------------- -------------------- 186SL0945300551986 70 none none none 186SL0945300561987 100 none none none 186SL0945300571988 81 none none none 186SL094530058 186SL094530059 QUALITY ASSESSMENT POLICY 186SL094530060 186SL094530061 The quality assessment is mostly based on the residuals 186SL094530062 (observed data minus predicted tides) of the hourly data. This 186SL094530063 assessment also applies to the daily and monthly data since 186SL094530064 they were derived from the quality-controlled hourly data. 186SL094530065 186SL094530066 The following abbreviations are used in the assessment: 186SL094530067 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL094530068 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL094530069 research program; NODC - National Oceanographic Data Center; 186SL094530070 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL094530071 Gaps > 1 mon - missing data in a span greater than one month; 186SL094530072 Refernce - reference. 186SL094530073 186SL094530074 The following corrections are made to the hourly data 186SL094530075 prior to this assessment: 186SL094530076 1) Gaps or obviously wrong data points in a span less than 186SL094530077 25 hours are filled by the predicted tide method*. 186SL094530078 2) Timing errors of exact increments of an hour are corrected 186SL094530079 by shifting the data. 186SL094530080 3) Reference level shifts are only corrected after information 186SL094530081 from tide staff readings or comparative readings with a fixed 186SL094530082 bench mark are checked to verify that the shift was not a 186SL094530083 natural event. If comparative readings are missing or 186SL094530084 incomplete, comparisons of the data with nearby stations 186SL094530085 may warrant the adjustment of some obvious shifts. 186SL094530086 4) Data with unresolved datum shifts are not disseminated. 186SL094530087 However, if sufficient time spans of data are available before 186SL094530088 or after the year(s) with the unresolved shift(s), a subset of 186SL094530089 quality assured data is made available. Thus, the Span field 186SL094530090 in the Quality Assessment may not match the span of the 186SL094530091 distribution data set. As the questionable datum shifts are 186SL094530092 resolved, the data set will be updated. Although this policy 186SL094530093 adds some complexity, it allows more rapid dissemination of 186SL094530094 at least the quality assured years. 186SL094530095 186SL094530096 For each year, the following information is documented from 186SL094530097 the quality-controlled hourly data with dates given as the nth 186SL094530098 day of the year starting from 1 January: 186SL094530099 1) a Completeness Index (CI) based on the percentage of hours 186SL094530100 with available data, 186SL094530101 2) a list of gaps longer than a day, 186SL094530102 3) a summary of days with consecutive missing or obviously 186SL094530103 wrong data in a time span longer than 6 but less than 25 186SL094530104 hours that have been replaced, with hours in parentheses, and 186SL094530105 4) a summary of days with questionable fluctuations in the 186SL094530106 residual series. Fluctuations within the residuals are 186SL094530107 considered significant and are noted if they are greater than 186SL094530108 25 cm. This policy has changed slightly as of October 1992: 186SL094530109 only suspicious fluctuations due to obvious instrumentation 186SL094530110 problems are noted. Minor timing drifts are no longer 186SL094530111 included in the list of questionable days. 186SL094530112 186SL094530113 Note : If the predicted tides poorly model the observed heights 186SL094530114 due to the inability of the tidal analysis to completely resolv 186SL094530115 the non-linear shallow water effects, the residuals are not 186SL094530116 suitable for assessing the data quality. Instead, a subjective 186SL094530117 comment on the quality of the data is provided. 186SL094530118 186SL094530119 *The predicted tides are obtained with the use of a harmonic 186SL094530120 analysis program (Foreman, 1977) which is executed on a year 186SL094530121 of apparently good data for a given station. The Predicted 186SL094530122 Tide Method for filling gaps consists of statistically 186SL094530123 comparing the predicted tides to the observed data and 186SL094530124 shifting the predicted tides in time to correct for timing 186SL094530125 differences. Then the linear interpolation between hourly 186SL094530126 values at the end points of the gap in the residual series is 186SL094530127 added to the corresponding corrected predicted tide data to 186SL094530128 obtain interpolated values over the span of the gap. 186SL094530129 186SL094530130 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL094530131 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL094530132 186SL094530133 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL094530134 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL094530135 Victoria B.C. Pacific Marine Science Report 77-10. 186SL094530136 186SL09456 19861 99999999999999999999999999999999 106000 -13000 186SL09456 19862 -10000 -54000 -14000 -64000 -87000 -91000 186SL09456 19871 -46000 62000 20000 60000 165000 46000 186SL09456 19872 23000 46000 54000 44000 12000 -21000 186SL09456 19881 149000 57000 100000 270000 281000 161000 186SL09456 19882 115000 62000 83000999999999999999999999999