186SL0840110006301 233A 19610525 19691231 0625N 00327E 2 00000R 0000 MM 186SL0840210006301 Lagos-A Nigeria POL 186SL084030001 186SL084030002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL084030003 by the 186SL084030004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL084030005 JOINT ARCHIVE FOR SEA LEVEL 186SL084030006 186SL084030007Station : Lagos-A Latitude: 06 25.0N 186SL084030008Country : Nigeria Longitude: 003 27.0E 186SL084030009JASL # : 233A Time Meridian: 015E (GMT + 1 hour) 186SL084030010GLOSS # : 259 TOGA #: A032 NODC #: 10006301 186SL084030011Contributor : Proudman Oceanographic Laboratory 186SL084030012 Bidston Observatory, Birkenhead 186SL084030013 Merseyside L43 7RA 186SL084030014Originator : Nigerian Institute for Oceanographic and 186SL084030015 Marine Research 186SL084030016 Victoria Island, P. M. B. 12729, Lagos 186SL084030017 NIGERIA 186SL084030018Original Data: unconfirmed 186SL084030019Instrmnt Type: unconfirmed 186SL084030020Digitzd Intvl: unconfirmed 186SL084030021Present Data : Hourly, daily, and monthly values obtained by: 186SL084030022 Hourly : unconfirmed 186SL084030023 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL084030024 centered on noon applied to the hourly data 186SL084030025 with respective periods of the 95, 50, and 5% 186SL084030026 amplitude points at 124.0, 60.2, and 40.2 hours 186SL084030027 Monthly: Simple average of all daily values; calculated if 186SL084030028 7 or fewer days are missing 186SL084030029Span of data : 25 May 1961 - 17 Dec 1970 186SL084030030Gaps > 1 mon : 20 Nov 1961 - 29 Dec 1961;01 Aug 1962 - 04 Jan 1963 186SL084030031 04 Dec 1963 - 22 Jun 1964;11 Aug 1964 - 31 Dec 1964 186SL084030032 16 Jul 1965 - 06 May 1966;30 Sep 1966 - 02 Dec 1966 186SL084030033 02 Aug 1968 - 03 Sep 1968;25 Oct 1968 - 12 Dec 1968 186SL084030034 27 Sep 1969 - 19 Feb 1970 186SL084030035Time Refernce: GMT (00-23 hours) Space-filler Flag :-9999 186SL084030036Units : millimeters Missing Data Flag :99999 186SL084030037Refernce Levl: It is assumed that the data have been linked to 186SL084030038 tide staff zero and fixed bench marks by the 186SL084030039 originators. 186SL084030040Comment : The daily and monthly means look reasonable with 186SL084030041 no obvious shifts or trends except for the segment 186SL084030042 after the gap in 1970 when the reference level 186SL084030043 is suspiciously low. The hourly residuals contain 186SL084030044 a large amount of questionable fluctuations due to 186SL084030045 complex tides that were not resolved by the tidal 186SL084030046 analysis; thus, the timing uncertainty is not 186SL084030047 clear. In 1970, the tidal range is different than 186SL084030048 the previous years; this year will not be made 186SL084030049 available for international distribution due to 186SL084030050 th high uncertainty in the data. 186SL084030051 186SL084030052 CI MISSING REPLACED GAPS QUESTIONABLE 186SL084030053YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL084030054---- --- -------------------- --------------- -------------------- 186SL0840300551961 50 324-363 none see comment above 186SL0840300561962 56 26-32,213-365 none see comment above 186SL0840300571963 86 1-4,115-117, (13)261-(23)261 see comment above 186SL084030058 195-204,275-290, 186SL084030059 338-365 186SL0840300601964 13 1-174,223-366 none see comment above 186SL0840300611965 51 156-163,197-365 none see comment above 186SL0840300621966 48 1-126,273-336 none see comment above 186SL0840300631967 88 158-160,211-215, (23)088-(22)089 see comment above 186SL084030064 272-281,305-334, 186SL084030065 364-365 186SL0840300661968 75 1-4,180-187, none see comment above 186SL084030067 215-247,298-346 186SL0840300681969 65 34-39,94-98, (12)059-(22)059 see comment above 186SL084030069 135-156,214-216, 186SL084030070 270-365 186SL0840300711970 76 1-50,131-145, none see comment above 186SL084030072 234-243,351-365 186SL084030073 186SL084030074 QUALITY ASSESSMENT POLICY 186SL084030075 186SL084030076 The quality assessment is mostly based on the residuals 186SL084030077 (observed data minus predicted tides) of the hourly data. This 186SL084030078 assessment also applies to the daily and monthly data since 186SL084030079 they were derived from the quality-controlled hourly data. 186SL084030080 186SL084030081 The following abbreviations are used in the assessment: 186SL084030082 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL084030083 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL084030084 research program; NODC - National Oceanographic Data Center; 186SL084030085 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL084030086 Gaps > 1 mon - missing data in a span greater than one month; 186SL084030087 Refernce - reference. 186SL084030088 186SL084030089 The following corrections are made to the hourly data 186SL084030090 prior to this assessment: 186SL084030091 1) Gaps or obviously wrong data points in a span less than 186SL084030092 25 hours are filled by the predicted tide method*. 186SL084030093 2) Timing errors of exact increments of an hour are corrected 186SL084030094 by shifting the data. 186SL084030095 3) Reference level shifts are only corrected after information 186SL084030096 from tide staff readings or comparative readings with a fixed 186SL084030097 bench mark are checked to verify that the shift was not a 186SL084030098 natural event. If comparative readings are missing or 186SL084030099 incomplete, comparisons of the data with nearby stations 186SL084030100 may warrant the adjustment of some obvious shifts. 186SL084030101 4) Data with unresolved datum shifts are not disseminated. 186SL084030102 However, if sufficient time spans of data are available before 186SL084030103 or after the year(s) with the unresolved shift(s), a subset of 186SL084030104 quality assured data is made available. Thus, the Span field 186SL084030105 in the Quality Assessment may not match the span of the 186SL084030106 distribution data set. As the questionable datum shifts are 186SL084030107 resolved, the data set will be updated. Although this policy 186SL084030108 adds some complexity, it allows more rapid dissemination of 186SL084030109 at least the quality assured years. 186SL084030110 186SL084030111 For each year, the following information is documented from 186SL084030112 the quality-controlled hourly data with dates given as the nth 186SL084030113 day of the year starting from 1 January: 186SL084030114 1) a Completeness Index (CI) based on the percentage of hours 186SL084030115 with available data, 186SL084030116 2) a list of gaps longer than a day, 186SL084030117 3) a summary of days with consecutive missing or obviously 186SL084030118 wrong data in a time span longer than 6 but less than 25 186SL084030119 hours that have been replaced, with hours in parentheses, and 186SL084030120 4) a summary of days with questionable fluctuations in the 186SL084030121 residual series. Fluctuations within the residuals are 186SL084030122 considered significant and are noted if they are greater than 186SL084030123 25 cm. This policy has changed slightly as of October 1992: 186SL084030124 only suspicious fluctuations due to obvious instrumentation 186SL084030125 problems are noted. Minor timing drifts are no longer 186SL084030126 included in the list of questionable days. 186SL084030127 186SL084030128 Note : If the predicted tides poorly model the observed heights 186SL084030129 due to the inability of the tidal analysis to completely resolv 186SL084030130 the non-linear shallow water effects, the residuals are not 186SL084030131 suitable for assessing the data quality. Instead, a subjective 186SL084030132 comment on the quality of the data is provided. 186SL084030133 186SL084030134 *The predicted tides are obtained with the use of a harmonic 186SL084030135 analysis program (Foreman, 1977) which is executed on a year 186SL084030136 of apparently good data for a given station. The Predicted 186SL084030137 Tide Method for filling gaps consists of statistically 186SL084030138 comparing the predicted tides to the observed data and 186SL084030139 shifting the predicted tides in time to correct for timing 186SL084030140 differences. Then the linear interpolation between hourly 186SL084030141 values at the end points of the gap in the residual series is 186SL084030142 added to the corresponding corrected predicted tide data to 186SL084030143 obtain interpolated values over the span of the gap. 186SL084030144 186SL084030145 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL084030146 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL084030147 186SL084030148 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL084030149 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL084030150 Victoria B.C. Pacific Marine Science Report 77-10. 186SL084030151 186SL08406 19611 9999999999999999999999999999999999999999 484000 186SL08406 19612 425000 350000 389000 5760009999999999999999 186SL08406 19621 423060 458010 484000 474000 447000 528000 186SL08406 19622 5660009999999999999999999999999999999999999999 186SL08406 19631 455040 441000 463000 474030 531000 491000 186SL08406 19632 99999999 602000 62400099999999 60000099999999 186SL08406 19641 999999999999999999999999999999999999999999999999 186SL08406 19642 3350009999999999999999999999999999999999999999 186SL08406 19651 364000 404000 419000 390000 37800099999999 186SL08406 19652 999999999999999999999999999999999999999999999999 186SL08406 19661 99999999999999999999999999999999 478060 452000 186SL08406 19662 487000 459000 4710109999999999999999 450020 186SL08406 19671 429000 479000 477000 517000 488000 441030 186SL08406 19672 430020 376030 427020 56707099999999 459020 186SL08406 19681 418040 418000 468000 410000 417000 448030 186SL08406 19682 50805099999999 597030999999999999999999999999 186SL08406 19691 404000 455060 490000 45505099999999 421050 186SL08406 19692 414000 420030 478040999999999999999999999999