186SL0849170079902 267A 19840101 19931231 0922N 07953W 2 00000R 0000 MM 186SL0849270079902 Coco Solo Panama Panama Canal Commission 186SL084930001 186SL084930002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL084930003 by the 186SL084930004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL084930005 JOINT ARCHIVE FOR SEA LEVEL 186SL084930006 186SL084930007Station : Coco Solo Latitude: 09 22.0N 186SL084930008Country : Panama Longitude: 079 53.0W 186SL084930009JASL # : 267A Time Meridian: 075W (GMT - 5 hr) 186SL084930010GLOSS # : 208 TOGA #: A009 NODC #: 70079902 186SL084930011Contributor : Panama Canal Commission 186SL084930012 Engineering Division 186SL084930013 APO Miami 34011 186SL084930014Originator : same 186SL084930015Original Data: digital and analog 186SL084930016Instrmnt Type: float and well gauges; primary are digital gauges: 186SL084930017 1981-1987:Stevens Digital Model 7001 186SL084930018 1988-present: Handar Digital 550B Hydrologger 186SL084930019 1988-present: Stevens A71 Analog 186SL084930020Digitzd Intvl: 15 minutes (digital), hourly (analog) 186SL084930021Present Data : Hourly, daily, and monthly values obtained by: 186SL084930022 Hourly : three-point Hanning filter centered on the hour 186SL084930023 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL084930024 centered on noon applied to the hourly data 186SL084930025 with respective periods of the 95, 50, and 5% 186SL084930026 amplitude points at 124.0, 60.2, and 40.2 hours 186SL084930027 Monthly: Simple average of all daily values; calculated if 186SL084930028 7 or fewer days are missing 186SL084930029Span of data : 01 Jan 1981 - 31 Dec 1993 186SL084930030Gaps > 1 mon : 30 Oct 1982 - 01 Dec 1982 186SL084930031Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL084930032Units : millimeters Missing Data Flag :99999 186SL084930033Refernce Levl: The data have been linked to a set of fixed bench 186SL084930034 marks by the originators. 186SL084930035Comment : The following periods have reference level shifts: 186SL084930036 1) 01 Jul 1982 (about -18 cm) and 2) 28 Apr 1983 186SL084930037 (about +28 cm). An obvious reference level shift 186SL084930038 was adjusted from (06 GMT) 01 Aug - (06 GMT) 10 Aug 186SL084930039 1984 by adding 29.5 cm to the original data. This 186SL084930040 adjustment is uncertain to a few centimeters. The 186SL084930041 originators have investigated the records and no 186SL084930042 clues for resolving these features could be found. 186SL084930043 Otherwise, the daily and monthly values do not 186SL084930044 reveal any other obvious level shifts or trends and 186SL084930045 the data are of high quality. 186SL084930046 186SL084930047 CI MISSING REPLACED GAPS QUESTIONABLE 186SL084930048YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL084930049---- --- -------------------- --------------- -------------------- 186SL0849300501981 99 128-131 none none 186SL0849300511982 91 302-335 none none 186SL0849300521983 100 none none none 186SL0849300531984 100 none (22)249-(05)250 none 186SL0849300541985 100 none none none 186SL0849300551986 100 none none none 186SL0849300561987 100 none none none 186SL0849300571988 100 none (06)069-(13)069 none 186SL0849300581989 99 10-12 none none 186SL0849300591990 100 none none none 186SL0849300601991 100 none none none 186SL0849300611992 100 none none none 186SL0849300621993 100 none none none 186SL084930063 186SL084930064 QUALITY ASSESSMENT POLICY 186SL084930065 186SL084930066 The quality assessment is mostly based on the residuals 186SL084930067 (observed data minus predicted tides) of the hourly data. This 186SL084930068 assessment also applies to the daily and monthly data since 186SL084930069 they were derived from the quality-controlled hourly data. 186SL084930070 186SL084930071 The following abbreviations are used in the assessment: 186SL084930072 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL084930073 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL084930074 research program; NODC - National Oceanographic Data Center; 186SL084930075 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL084930076 Gaps > 1 mon - missing data in a span greater than one month; 186SL084930077 Refernce - reference. 186SL084930078 186SL084930079 The following corrections are made to the hourly data 186SL084930080 prior to this assessment: 186SL084930081 1) Gaps or obviously wrong data points in a span less than 186SL084930082 25 hours are filled by the predicted tide method*. 186SL084930083 2) Timing errors of exact increments of an hour are corrected 186SL084930084 by shifting the data. 186SL084930085 3) Reference level shifts are only corrected after information 186SL084930086 from tide staff readings or comparative readings with a fixed 186SL084930087 bench mark are checked to verify that the shift was not a 186SL084930088 natural event. If comparative readings are missing or 186SL084930089 incomplete, comparisons of the data with nearby stations 186SL084930090 may warrant the adjustment of some obvious shifts. 186SL084930091 4) Data with unresolved datum shifts are not disseminated. 186SL084930092 However, if sufficient time spans of data are available before 186SL084930093 or after the year(s) with the unresolved shift(s), a subset of 186SL084930094 quality assured data is made available. Thus, the Span field 186SL084930095 in the Quality Assessment may not match the span of the 186SL084930096 distribution data set. As the questionable datum shifts are 186SL084930097 resolved, the data set will be updated. Although this policy 186SL084930098 adds some complexity, it allows more rapid dissemination of 186SL084930099 at least the quality assured years. 186SL084930100 186SL084930101 For each year, the following information is documented from 186SL084930102 the quality-controlled hourly data with dates given as the nth 186SL084930103 day of the year starting from 1 January: 186SL084930104 1) a Completeness Index (CI) based on the percentage of hours 186SL084930105 with available data, 186SL084930106 2) a list of gaps longer than a day, 186SL084930107 3) a summary of days with consecutive missing or obviously 186SL084930108 wrong data in a time span longer than 6 but less than 25 186SL084930109 hours that have been replaced, with hours in parentheses, and 186SL084930110 4) a summary of days with questionable fluctuations in the 186SL084930111 residual series. Fluctuations within the residuals are 186SL084930112 considered significant and are noted if they are greater than 186SL084930113 25 cm. This policy has changed slightly as of October 1992: 186SL084930114 only suspicious fluctuations due to obvious instrumentation 186SL084930115 problems are noted. Minor timing drifts are no longer 186SL084930116 included in the list of questionable days. 186SL084930117 186SL084930118 Note : If the predicted tides poorly model the observed heights 186SL084930119 due to the inability of the tidal analysis to completely resolv 186SL084930120 the non-linear shallow water effects, the residuals are not 186SL084930121 suitable for assessing the data quality. Instead, a subjective 186SL084930122 comment on the quality of the data is provided. 186SL084930123 186SL084930124 *The predicted tides are obtained with the use of a harmonic 186SL084930125 analysis program (Foreman, 1977) which is executed on a year 186SL084930126 of apparently good data for a given station. The Predicted 186SL084930127 Tide Method for filling gaps consists of statistically 186SL084930128 comparing the predicted tides to the observed data and 186SL084930129 shifting the predicted tides in time to correct for timing 186SL084930130 differences. Then the linear interpolation between hourly 186SL084930131 values at the end points of the gap in the residual series is 186SL084930132 added to the corresponding corrected predicted tide data to 186SL084930133 obtain interpolated values over the span of the gap. 186SL084930134 186SL084930135 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL084930136 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL084930137 186SL084930138 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL084930139 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL084930140 Victoria B.C. Pacific Marine Science Report 77-10. 186SL084930141 186SL08496 19841 802000 785000 744000 720000 749000 774000 186SL08496 19842 782000 733000 738000 826000 811000 739000 186SL08496 19851 748000 771000 728000 704000 732000 739000 186SL08496 19852 729000 724000 812000 791000 748000 749000 186SL08496 19861 768000 720000 722000 732000 762000 769000 186SL08496 19862 794000 780000 809000 805000 814000 742000 186SL08496 19871 781000 765000 723000 826000 780000 724000 186SL08496 19872 790000 824000 811000 797000 832000 783000 186SL08496 19881 745000 769000 690000 685000 701000 691000 186SL08496 19882 736000 701000 670000 792000 748000 750000 186SL08496 19891 711030 750000 695000 665000 700000 712000 186SL08496 19892 714000 744000 768000 801000 788000 758000 186SL08496 19901 743000 686000 729000 723000 775000 758000 186SL08496 19902 752000 789000 800000 816000 842000 778000 186SL08496 19911 736000 717000 698000 704000 764000 734000 186SL08496 19912 741000 802000 853000 855000 846000 745000 186SL08496 19921 768000 745000 730000 763000 792000 773000 186SL08496 19922 752000 811000 832000 857000 820000 800000 186SL08496 19931 763000 770000 733000 730000 745000 756000 186SL08496 19932 748000 740000 771000 801000 803000 792000