186SL0690152107901 022D 19770322 19840807 2709S 10927W 2 00000R 0000 MM 186SL0690252107901 Easter-D Chile TOGA Sea Level Center 186SL069030001 186SL069030002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL069030003 by the 186SL069030004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL069030005 JOINT ARCHIVE FOR SEA LEVEL 186SL069030006 186SL069030007Station : Easter-D Latitude: 27 09.0S 186SL069030008Country : Chile Longitude: 109 26.9W 186SL069030009JASL # : 022D Time Meridian: 105W (GMT - 7 hr) 186SL069030010GLOSS # : 137 TOGA #: P069 NODC #: 52107901 186SL069030011Contributor : TOGA Sea Level Center 186SL069030012 1000 Pope Rd. MSB 317 186SL069030013 Honolulu, Hawaii 96822 186SL069030014Originator : Dept. of Oceanography 186SL069030015 University of Hawaii 186SL069030016 1000 Pope Rd. MSB 317 186SL069030017 Honolulu, Hawaii 96822 186SL069030018Original Data: digital 186SL069030019Instrmnt Type: Fischer and Porter Analog-to-Digital Recorder 186SL069030020Digitzd Intvl: 15 minutes 186SL069030021Present Data : Hourly, daily, and monthly values obtained by: 186SL069030022 Hourly : Nine-point triangular filter centered 186SL069030023 on the hour with respective periods of the 95, 50, 186SL069030024 and 5% amplitude point of the filter response at 186SL069030025 623.6, 177.0, and 103.7 minutes 186SL069030026 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL069030027 centered on noon applied to the hourly data 186SL069030028 with respective periods of the 95, 50, and 5% 186SL069030029 amplitude points at 124.0, 60.2, and 40.2 hours 186SL069030030 Monthly: Simple average of all daily values; calculated if 186SL069030031 7 or fewer days are missing 186SL069030032Span of data : 22 Mar 1977 - 07 Aug 1984 186SL069030033Gaps > 1 mon : 1 Jan - 1 Feb 1979; 1 Feb - 1 Mar 1983 186SL069030034Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL069030035Units : millimeters Missing Data Flag :99999 186SL069030036Refernce Levl: All heights have been referred to the station tide 186SL069030037 staff zero which is linked to fixed bench marks; 186SL069030038 however, these bench marks are not linked to the 186SL069030039 bench marks used by other tide records at this 186SL069030040 site. Thus, this data set is independent. 186SL069030041Comment : The daily and monthly means reveal no apparent 186SL069030042 changes in the reference level. Large deviations 186SL069030043 with a period from 1 to 3 days occur during the 186SL069030044 winter season associated with weather events. 186SL069030045 186SL069030046 CI MISSING REPLACED GAPS QUESTIONABLE 186SL069030047YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL069030048---- --- -------------------- --------------- -------------------- 186SL0690300491977 77 282-283 none 150,157,351 186SL0690300501978 100 none none none 186SL0690300511979 89 1-32,135-139, none none 186SL069030052 362-365 186SL0690300531980 99 1,247-250 none 138 186SL0690300541981 100 none none none 186SL0690300551982 99 65-67 none none 186SL0690300561983 92 32-60 none none 186SL0690300571984 58 121-128 none none 186SL069030058 186SL069030059 QUALITY ASSESSMENT POLICY 186SL069030060 186SL069030061 The quality assessment is mostly based on the residuals 186SL069030062 (observed data minus predicted tides) of the hourly data. This 186SL069030063 assessment also applies to the daily and monthly data since 186SL069030064 they were derived from the quality-controlled hourly data. 186SL069030065 186SL069030066 The following abbreviations are used in the assessment: 186SL069030067 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL069030068 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL069030069 research program; NODC - National Oceanographic Data Center; 186SL069030070 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL069030071 Gaps > 1 mon - missing data in a span greater than one month; 186SL069030072 Refernce - reference. 186SL069030073 186SL069030074 The following corrections are made to the hourly data 186SL069030075 prior to this assessment: 186SL069030076 1) Gaps or obviously wrong data points in a span less than 186SL069030077 25 hours are filled by the predicted tide method*. 186SL069030078 2) Timing errors of exact increments of an hour are corrected 186SL069030079 by shifting the data. 186SL069030080 3) Reference level shifts are only corrected after information 186SL069030081 from tide staff readings or comparative readings with a fixed 186SL069030082 bench mark are checked to verify that the shift was not a 186SL069030083 natural event. If comparative readings are missing or 186SL069030084 incomplete, comparisons of the data with nearby stations 186SL069030085 may warrant the adjustment of some obvious shifts. 186SL069030086 4) Data with unresolved datum shifts are not disseminated. 186SL069030087 However, if sufficient time spans of data are available before 186SL069030088 or after the year(s) with the unresolved shift(s), a subset of 186SL069030089 quality assured data is made available. Thus, the Span field 186SL069030090 in the Quality Assessment may not match the span of the 186SL069030091 distribution data set. As the questionable datum shifts are 186SL069030092 resolved, the data set will be updated. Although this policy 186SL069030093 adds some complexity, it allows more rapid dissemination of 186SL069030094 at least the quality assured years. 186SL069030095 186SL069030096 For each year, the following information is documented from 186SL069030097 the quality-controlled hourly data with dates given as the nth 186SL069030098 day of the year starting from 1 January: 186SL069030099 1) a Completeness Index (CI) based on the percentage of hours 186SL069030100 with available data, 186SL069030101 2) a list of gaps longer than a day, 186SL069030102 3) a summary of days with consecutive missing or obviously 186SL069030103 wrong data in a time span longer than 6 but less than 25 186SL069030104 hours that have been replaced, with hours in parentheses, and 186SL069030105 4) a summary of days with questionable fluctuations in the 186SL069030106 residual series. Fluctuations within the residuals are 186SL069030107 considered significant and are noted if they are greater than 186SL069030108 25 cm. This policy has changed slightly as of October 1992: 186SL069030109 only suspicious fluctuations due to obvious instrumentation 186SL069030110 problems are noted. Minor timing drifts are no longer 186SL069030111 included in the list of questionable days. 186SL069030112 186SL069030113 Note : If the predicted tides poorly model the observed heights 186SL069030114 due to the inability of the tidal analysis to completely resolv 186SL069030115 the non-linear shallow water effects, the residuals are not 186SL069030116 suitable for assessing the data quality. Instead, a subjective 186SL069030117 comment on the quality of the data is provided. 186SL069030118 186SL069030119 *The predicted tides are obtained with the use of a harmonic 186SL069030120 analysis program (Foreman, 1977) which is executed on a year 186SL069030121 of apparently good data for a given station. The Predicted 186SL069030122 Tide Method for filling gaps consists of statistically 186SL069030123 comparing the predicted tides to the observed data and 186SL069030124 shifting the predicted tides in time to correct for timing 186SL069030125 differences. Then the linear interpolation between hourly 186SL069030126 values at the end points of the gap in the residual series is 186SL069030127 added to the corresponding corrected predicted tide data to 186SL069030128 obtain interpolated values over the span of the gap. 186SL069030129 186SL069030130 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL069030131 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL069030132 186SL069030133 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL069030134 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL069030135 Victoria B.C. Pacific Marine Science Report 77-10. 186SL069030136 186SL06906 19771 999999999999999999999999 965000 925000 853000 186SL06906 19772 776000 740000 811000 811030 827000 862000 186SL06906 19781 841000 874000 897000 925000 897000 839000 186SL06906 19782 885000 769000 843000 834000 813000 806000 186SL06906 19791 99999999 830010 921000 954000 913050 807000 186SL06906 19792 926000 918000 744000 785000 864000 833040 186SL06906 19801 779020 862000 937000 938000 888000 920000 186SL06906 19802 821000 827000 863040 821000 852000 834000 186SL06906 19811 765000 849000 884000 904000 915000 900000 186SL06906 19812 771000 838000 830000 796000 843000 868000 186SL06906 19821 800000 784000 868030 935000 851000 808000 186SL06906 19822 848000 856000 848000 816000 834000 883000 186SL06906 19831 89000099999999 972010 906000 780000 733000 186SL06906 19832 768000 699000 676000 666000 718000 765000 186SL06906 19841 806000 809000 834000 849010 786070 732000 186SL06906 19842 7140009999999999999999999999999999999999999999