186SL0820110074302 108B 19890827 19931231 0411N 07332E 2 00000R 0000 MM 186SL0820210074302 Male-B,Hulule Rep. of Maldives Dept. of Meteorology 186SL082030001 186SL082030002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL082030003 by the 186SL082030004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL082030005 JOINT ARCHIVE FOR SEA LEVEL 186SL082030006 186SL082030007Station : Male-B,Hulule Latitude: 04 11.4N 186SL082030008Country : Rep. of Maldives Longitude: 073 31.6E 186SL082030009JASL # : 108B Time Meridian: 075E (GMT + 5 hr) 186SL082030010GLOSS # : 028 TOGA #: I052 NODC #: 10074302 186SL082030011Contributor : Dept. of Meteorology 186SL082030012 Male, Republic of Maldives 186SL082030013Originator : same 186SL082030014Original Data: analog 186SL082030015Instrmnt Type: Metercraft Bubbler 186SL082030016Digitzd Intvl: hourly 186SL082030017Present Data : Hourly, daily, and monthly values obtained by: 186SL082030018 Hourly : Original data were spot hourly 186SL082030019 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL082030020 centered on noon applied to the hourly data 186SL082030021 with respective periods of the 95, 50, and 5% 186SL082030022 amplitude points at 124.0, 60.2, and 40.2 hours 186SL082030023 Monthly: Simple average of all daily values; calculated if 186SL082030024 7 or fewer days are missing 186SL082030025Span of data : 27 Aug 1989 - 31 Dec 1993 186SL082030026Gaps > 1 mon : 14 Jan 1990 - 09 May 1990;04 Sep 1990 - 05 Nov 1990 186SL082030027 28 Nov 1991 - 07 Jan 1992 186SL082030028Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL082030029Units : millimeters Missing Data Flag :99999 186SL082030030Refernce Levl: The sea level heights are referred to the zero 186SL082030031 point assigned to the tide gauge. 186SL082030032Comment : The daily and monthly means do not reveal any 186SL082030033 suspicious reference level changes. The 186SL082030034 timing is no better than about +/- 7 minutes. 186SL082030035 This station has not been linked via surveys to 186SL082030036 Male-A, which is on a nearby separate atoll. 186SL082030037 186SL082030038 CI MISSING REPLACED GAPS QUESTIONABLE 186SL082030039YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL082030040---- --- -------------------- --------------- -------------------- 186SL0820300411989 24 249-251,256-283, none 239-249,252-256,283- 186SL082030042 303-313, 288,294-298,313 186SL0820300431990 38 14-129,133-135, none 206-207,217-218,243- 186SL082030044 164-176,181-191, 247,313-314 186SL082030045 198-200,207-212, 186SL082030046 214-216,223-225, 186SL082030047 227-242,247-309, 186SL082030048 319-322 186SL0820300491991 88 32-36,46-48,195-198, none 36-113,231-306 186SL082030050 332-365 186SL0820300511992 96 1-7,15-18,141-145 none 11-120,200-298 186SL0820300521993 100 none (16)043-(04)044 44-91,244-287 186SL082030053 (11)057-(05)058 186SL082030054 (07)137-(06)138 186SL082030055 (11)179-(04)180 186SL082030056 (14)213-(07)214 186SL082030057 (11)239-(07)240 186SL082030058 (16)278-(08)279 186SL082030059 (00)323-(23)323 186SL082030060 186SL082030061 QUALITY ASSESSMENT POLICY 186SL082030062 186SL082030063 The quality assessment is mostly based on the residuals 186SL082030064 (observed data minus predicted tides) of the hourly data. This 186SL082030065 assessment also applies to the daily and monthly data since 186SL082030066 they were derived from the quality-controlled hourly data. 186SL082030067 186SL082030068 The following abbreviations are used in the assessment: 186SL082030069 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL082030070 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL082030071 research program; NODC - National Oceanographic Data Center; 186SL082030072 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL082030073 Gaps > 1 mon - missing data in a span greater than one month; 186SL082030074 Refernce - reference. 186SL082030075 186SL082030076 The following corrections are made to the hourly data 186SL082030077 prior to this assessment: 186SL082030078 1) Gaps or obviously wrong data points in a span less than 186SL082030079 25 hours are filled by the predicted tide method*. 186SL082030080 2) Timing errors of exact increments of an hour are corrected 186SL082030081 by shifting the data. 186SL082030082 3) Reference level shifts are only corrected after information 186SL082030083 from tide staff readings or comparative readings with a fixed 186SL082030084 bench mark are checked to verify that the shift was not a 186SL082030085 natural event. If comparative readings are missing or 186SL082030086 incomplete, comparisons of the data with nearby stations 186SL082030087 may warrant the adjustment of some obvious shifts. 186SL082030088 4) Data with unresolved datum shifts are not disseminated. 186SL082030089 However, if sufficient time spans of data are available before 186SL082030090 or after the year(s) with the unresolved shift(s), a subset of 186SL082030091 quality assured data is made available. Thus, the Span field 186SL082030092 in the Quality Assessment may not match the span of the 186SL082030093 distribution data set. As the questionable datum shifts are 186SL082030094 resolved, the data set will be updated. Although this policy 186SL082030095 adds some complexity, it allows more rapid dissemination of 186SL082030096 at least the quality assured years. 186SL082030097 186SL082030098 For each year, the following information is documented from 186SL082030099 the quality-controlled hourly data with dates given as the nth 186SL082030100 day of the year starting from 1 January: 186SL082030101 1) a Completeness Index (CI) based on the percentage of hours 186SL082030102 with available data, 186SL082030103 2) a list of gaps longer than a day, 186SL082030104 3) a summary of days with consecutive missing or obviously 186SL082030105 wrong data in a time span longer than 6 but less than 25 186SL082030106 hours that have been replaced, with hours in parentheses, and 186SL082030107 4) a summary of days with questionable fluctuations in the 186SL082030108 residual series. Fluctuations within the residuals are 186SL082030109 considered significant and are noted if they are greater than 186SL082030110 25 cm. This policy has changed slightly as of October 1992: 186SL082030111 only suspicious fluctuations due to obvious instrumentation 186SL082030112 problems are noted. Minor timing drifts are no longer 186SL082030113 included in the list of questionable days. 186SL082030114 186SL082030115 Note : If the predicted tides poorly model the observed heights 186SL082030116 due to the inability of the tidal analysis to completely resolv 186SL082030117 the non-linear shallow water effects, the residuals are not 186SL082030118 suitable for assessing the data quality. Instead, a subjective 186SL082030119 comment on the quality of the data is provided. 186SL082030120 186SL082030121 *The predicted tides are obtained with the use of a harmonic 186SL082030122 analysis program (Foreman, 1977) which is executed on a year 186SL082030123 of apparently good data for a given station. The Predicted 186SL082030124 Tide Method for filling gaps consists of statistically 186SL082030125 comparing the predicted tides to the observed data and 186SL082030126 shifting the predicted tides in time to correct for timing 186SL082030127 differences. Then the linear interpolation between hourly 186SL082030128 values at the end points of the gap in the residual series is 186SL082030129 added to the corresponding corrected predicted tide data to 186SL082030130 obtain interpolated values over the span of the gap. 186SL082030131 186SL082030132 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL082030133 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL082030134 186SL082030135 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL082030136 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL082030137 Victoria B.C. Pacific Marine Science Report 77-10. 186SL082030138 186SL08206 19891 999999999999999999999999999999999999999999999999 186SL08206 19892 9999999999999999999999999999999999999999 1847000 186SL08206 19901 999999999999999999999999999999999999999999999999 186SL08206 19902 9999999999999999999999999999999999999999 1868000 186SL08206 19911 189500099999999 1901000 1907000 1903000 1892000 186SL08206 19912 1948040 1893000 1835000 1855000 181103099999999 186SL08206 19921 99999999 1869000 1901000 1924000 1906050 1882000 186SL08206 19922 1925000 1863000 1858000 1804000 1864000 1878000 186SL08206 19931 1894000 1865000 1899000 1913000 1905000 1892000 186SL08206 19932 1902030 1821020 1851050 1843000 1833030 1834000