186SL0938173062401 259A 19850101 19921231 3222N 06442W 2 00000R 0000 MM 186SL0938273062401 Bermuda United Kingdom National Ocean Service 186SL093830001 186SL093830002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL093830003 by the 186SL093830004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL093830005 JOINT ARCHIVE FOR SEA LEVEL 186SL093830006 186SL093830007Station : Bermuda Latitude: 32 22.4N 186SL093830008Country : United Kingdom Longitude: 064 42.2W 186SL093830009JASL # : 259A Time Meridian: 060W (GMT - 4 hr) 186SL093830010GLOSS # : 221 TOGA #: none NODC #: 73062401 186SL093830011Contributor : National Ocean Service (NOS) 186SL093830012 National Ocean. and Atmos. Administration (NOAA) 186SL093830013 N/OES22 186SL093830014 SSMC4, STATION 7109 186SL093830015 1305 East West Highway 186SL093830016 Silver Spring, MD. 20910-3233 186SL093830017Originator : same 186SL093830018Original Data: Digital 186SL093830019Instrmnt Type: 1) 1985-9/1989, Analog-to-Digital Recorder (ADR) 186SL093830020 2) 10/1989-12/1991,Digital Bubbler (BUB) 186SL093830021 2) 1992-, Aquatrak acoustic gauge, NOAA Next 186SL093830022 Generation Water Level Measuring System (NGWLMS) 186SL093830023Digitzd Intvl: 6 minute 186SL093830024Present Data : Hourly, daily, and monthly values obtained by: 186SL093830025 Hourly : Discrete sampling on the hour 186SL093830026 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL093830027 centered on noon applied to the hourly data 186SL093830028 with respective periods of the 95, 50, and 5% 186SL093830029 amplitude points at 124.0, 60.2, and 40.2 hours 186SL093830030 Monthly: Simple average of all daily values; calculated if 186SL093830031 7 or fewer days are missing 186SL093830032Span of data : 01 Jan 1985 - 31 Dec 1992 186SL093830033Gaps > 1 mon : 01 Jul - 01 Aug 1988;02 Oct - 31 Dec 1988 186SL093830034 01 Apr - 31 May 1989 186SL093830035Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL093830036Units : millimeters Missing Data Flag :99999 186SL093830037Refernce Levl: All heights have been referred to the station tide 186SL093830038 staff zero which is linked to fixed bench marks 186SL093830039 of the Bermuda Biological Station (32 22.2N, 186SL093830040 064 41.7W). Starting 1/1/92, the series is from 186SL093830041 the Esso Pier, which has been leveled to the 186SL093830042 Biological Station. 509 mm was subtracted from 186SL093830043 the Esso data to relate it to the historical 186SL093830044 datum of the original site. 186SL093830045Comment : The daily and monthly values do not show any 186SL093830046 obvious shifts or trends. 186SL093830047 186SL093830048 CI MISSING REPLACED GAPS QUESTIONABLE 186SL093830049YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL093830050---- --- -------------------- --------------- -------------------- 186SL0938300511985 99 1 (07)110-(13)112 none 186SL0938300521986 100 none (10)096-(04)097 none 186SL0938300531987 100 none (14)208-(17)210 none 186SL093830054 (02)294-(23)296 186SL093830055 (23)327-(18)328 186SL093830056 (03)335-(14)335 186SL093830057 (04)337-(12)338 186SL0938300581988 67 183-214,276-366 (18)249-(17)250 none 186SL093830059 (14)262-(21)263 186SL0938300601989 81 91-151,182-191 (15)003-(11)005 none 186SL093830061 (03)058-(16)059 186SL093830062 (18)180-(14)182 186SL093830063 (17)224-(17)226 186SL093830064 (23)232-(14)233 186SL093830065 (18)243-(18)244 186SL093830066 (03)273-(02)274 186SL093830067 (03)353-(02)356 186SL0938300681990 100 none none none 186SL0938300691991 98 182-190 (21)225-(06)227 none 186SL0938300701992 100 none none none 186SL093830071 186SL093830072 QUALITY ASSESSMENT POLICY 186SL093830073 186SL093830074 The quality assessment is mostly based on the residuals 186SL093830075 (observed data minus predicted tides) of the hourly data. This 186SL093830076 assessment also applies to the daily and monthly data since 186SL093830077 they were derived from the quality-controlled hourly data. 186SL093830078 186SL093830079 The following abbreviations are used in the assessment: 186SL093830080 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL093830081 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL093830082 research program; NODC - National Oceanographic Data Center; 186SL093830083 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL093830084 Gaps > 1 mon - missing data in a span greater than one month; 186SL093830085 Refernce - reference. 186SL093830086 186SL093830087 The following corrections are made to the hourly data 186SL093830088 prior to this assessment: 186SL093830089 1) Gaps or obviously wrong data points in a span less than 186SL093830090 25 hours are filled by the predicted tide method*. 186SL093830091 2) Timing errors of exact increments of an hour are corrected 186SL093830092 by shifting the data. 186SL093830093 3) Reference level shifts are only corrected after information 186SL093830094 from tide staff readings or comparative readings with a fixed 186SL093830095 bench mark are checked to verify that the shift was not a 186SL093830096 natural event. If comparative readings are missing or 186SL093830097 incomplete, comparisons of the data with nearby stations 186SL093830098 may warrant the adjustment of some obvious shifts. 186SL093830099 4) Data with unresolved datum shifts are not disseminated. 186SL093830100 However, if sufficient time spans of data are available before 186SL093830101 or after the year(s) with the unresolved shift(s), a subset of 186SL093830102 quality assured data is made available. Thus, the Span field 186SL093830103 in the Quality Assessment may not match the span of the 186SL093830104 distribution data set. As the questionable datum shifts are 186SL093830105 resolved, the data set will be updated. Although this policy 186SL093830106 adds some complexity, it allows more rapid dissemination of 186SL093830107 at least the quality assured years. 186SL093830108 186SL093830109 For each year, the following information is documented from 186SL093830110 the quality-controlled hourly data with dates given as the nth 186SL093830111 day of the year starting from 1 January: 186SL093830112 1) a Completeness Index (CI) based on the percentage of hours 186SL093830113 with available data, 186SL093830114 2) a list of gaps longer than a day, 186SL093830115 3) a summary of days with consecutive missing or obviously 186SL093830116 wrong data in a time span longer than 6 but less than 25 186SL093830117 hours that have been replaced, with hours in parentheses, and 186SL093830118 4) a summary of days with questionable fluctuations in the 186SL093830119 residual series. Fluctuations within the residuals are 186SL093830120 considered significant and are noted if they are greater than 186SL093830121 25 cm. This policy has changed slightly as of October 1992: 186SL093830122 only suspicious fluctuations due to obvious instrumentation 186SL093830123 problems are noted. Minor timing drifts are no longer 186SL093830124 included in the list of questionable days. 186SL093830125 186SL093830126 Note : If the predicted tides poorly model the observed heights 186SL093830127 due to the inability of the tidal analysis to completely resolv 186SL093830128 the non-linear shallow water effects, the residuals are not 186SL093830129 suitable for assessing the data quality. Instead, a subjective 186SL093830130 comment on the quality of the data is provided. 186SL093830131 186SL093830132 *The predicted tides are obtained with the use of a harmonic 186SL093830133 analysis program (Foreman, 1977) which is executed on a year 186SL093830134 of apparently good data for a given station. The Predicted 186SL093830135 Tide Method for filling gaps consists of statistically 186SL093830136 comparing the predicted tides to the observed data and 186SL093830137 shifting the predicted tides in time to correct for timing 186SL093830138 differences. Then the linear interpolation between hourly 186SL093830139 values at the end points of the gap in the residual series is 186SL093830140 added to the corresponding corrected predicted tide data to 186SL093830141 obtain interpolated values over the span of the gap. 186SL093830142 186SL093830143 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL093830144 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL093830145 186SL093830146 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL093830147 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL093830148 Victoria B.C. Pacific Marine Science Report 77-10. 186SL093830149 186SL09386 19851 1302010 1250000 1323000 1191000 1139000 1325000 186SL09386 19852 1344000 1418000 1557000 1624000 1565000 1443000 186SL09386 19861 1386000 1442000 1487000 1454000 1340000 1395000 186SL09386 19862 1427000 1397000 1356000 1460000 1457000 1397000 186SL09386 19871 1424000 1459000 1345000 1447000 1481000 1444000 186SL09386 19872 1397000 1458000 1492000 1508000 1317000 1271000 186SL09386 19881 1307000 1245000 1258000 1392000 1251000 1291000 186SL09386 19882 99999999 1456010 1557000999999999999999999999999 186SL09386 19891 1366000 1409000 14030009999999999999999 1217000 186SL09386 19892 99999999 1478000 1469000 1436000 1542000 1473000 186SL09386 19901 1353000 1372000 1405000 1361000 1280000 1328000 186SL09386 19902 1393000 1397000 1350000 1461000 1488000 1476000 186SL09386 19911 1466000 1401000 1434000 1400000 1189000 1357000 186SL09386 19912 99999999 1364000 1478000 1397000 1213000 1348000 186SL09386 19921 1530000 1457000 1385000 1414000 1449000 1452000 186SL09386 19922 1401000 1511000 1457000 1356000 1360000 1390000