186SL0800131044001 193B 19821003 19830101 1428S 04041E 2 00000R 0000 MM 186SL0800231044001 Nacala-B Mozambique Inst. Hidro. Marinha 186SL080030001 186SL080030002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL080030003 by the 186SL080030004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL080030005 JOINT ARCHIVE FOR SEA LEVEL 186SL080030006 186SL080030007Station : Nacala-B Latitude: 14 27.8S 186SL080030008Country : Mozambique Longitude: 040 40.8E 186SL080030009JASL # : 193B Time Meridian: 030E (GMT + 2 hr) 186SL080030010GLOSS # : none TOGA #: none NODC #: 31044001 186SL080030011Contributor : Instituto Hidrografico Marinha 186SL080030012 Rua das Trinas 186SL080030013 49-P-1296 Lisboa Codex 186SL080030014 Lisbon, Portugal 186SL080030015Originator : same 186SL080030016Original Data: unconfirmed 186SL080030017Instrmnt Type: unconfirmed 186SL080030018Digitzd Intvl: unconfirmed 186SL080030019Present Data : Hourly, daily, and monthly values obtained by: 186SL080030020 Hourly : unconfirmed 186SL080030021 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL080030022 centered on noon applied to the hourly data 186SL080030023 with respective periods of the 95, 50, and 5% 186SL080030024 amplitude points at 124.0, 60.2, and 40.2 hours 186SL080030025 Monthly: Simple average of all daily values; calculated if 186SL080030026 7 or fewer days are missing 186SL080030027Span of data : 03 Oct 1982 - 01 Jan 1983 186SL080030028Gaps > 1 mon : none 186SL080030029Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL080030030Units : millimeters Missing Data Flag :99999 186SL080030031Refernce Levl: All heights have been referred to the station tide 186SL080030032 staff zero which is linked to fixed bench marks 186SL080030033Comment : The daily means due not reveal any obvious 186SL080030034 reference level problems. Timing errors occur 186SL080030035 throughout. 186SL080030036 186SL080030037 CI MISSING REPLACED GAPS QUESTIONABLE 186SL080030038YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL080030039---- --- -------------------- --------------- -------------------- 186SL0800300401982 25 none none 276-324,327-333, 186SL080030041 337-365 186SL0800300421983 1 none none 1 186SL080030043 186SL080030044 QUALITY ASSESSMENT POLICY 186SL080030045 186SL080030046 The quality assessment is mostly based on the residuals 186SL080030047 (observed data minus predicted tides) of the hourly data. This 186SL080030048 assessment also applies to the daily and monthly data since 186SL080030049 they were derived from the quality-controlled hourly data. 186SL080030050 186SL080030051 The following abbreviations are used in the assessment: 186SL080030052 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL080030053 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL080030054 research program; NODC - National Oceanographic Data Center; 186SL080030055 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL080030056 Gaps > 1 mon - missing data in a span greater than one month; 186SL080030057 Refernce - reference. 186SL080030058 186SL080030059 The following corrections are made to the hourly data 186SL080030060 prior to this assessment: 186SL080030061 1) Gaps or obviously wrong data points in a span less than 186SL080030062 25 hours are filled by the predicted tide method*. 186SL080030063 2) Timing errors of exact increments of an hour are corrected 186SL080030064 by shifting the data. 186SL080030065 3) Reference level shifts are only corrected after information 186SL080030066 from tide staff readings or comparative readings with a fixed 186SL080030067 bench mark are checked to verify that the shift was not a 186SL080030068 natural event. If comparative readings are missing or 186SL080030069 incomplete, comparisons of the data with nearby stations 186SL080030070 may warrant the adjustment of some obvious shifts. 186SL080030071 4) Data with unresolved datum shifts are not disseminated. 186SL080030072 However, if sufficient time spans of data are available before 186SL080030073 or after the year(s) with the unresolved shift(s), a subset of 186SL080030074 quality assured data is made available. Thus, the Span field 186SL080030075 in the Quality Assessment may not match the span of the 186SL080030076 distribution data set. As the questionable datum shifts are 186SL080030077 resolved, the data set will be updated. Although this policy 186SL080030078 adds some complexity, it allows more rapid dissemination of 186SL080030079 at least the quality assured years. 186SL080030080 186SL080030081 For each year, the following information is documented from 186SL080030082 the quality-controlled hourly data with dates given as the nth 186SL080030083 day of the year starting from 1 January: 186SL080030084 1) a Completeness Index (CI) based on the percentage of hours 186SL080030085 with available data, 186SL080030086 2) a list of gaps longer than a day, 186SL080030087 3) a summary of days with consecutive missing or obviously 186SL080030088 wrong data in a time span longer than 6 but less than 25 186SL080030089 hours that have been replaced, with hours in parentheses, and 186SL080030090 4) a summary of days with questionable fluctuations in the 186SL080030091 residual series. Fluctuations within the residuals are 186SL080030092 considered significant and are noted if they are greater than 186SL080030093 25 cm. This policy has changed slightly as of October 1992: 186SL080030094 only suspicious fluctuations due to obvious instrumentation 186SL080030095 problems are noted. Minor timing drifts are no longer 186SL080030096 included in the list of questionable days. 186SL080030097 186SL080030098 Note : If the predicted tides poorly model the observed heights 186SL080030099 due to the inability of the tidal analysis to completely resolv 186SL080030100 the non-linear shallow water effects, the residuals are not 186SL080030101 suitable for assessing the data quality. Instead, a subjective 186SL080030102 comment on the quality of the data is provided. 186SL080030103 186SL080030104 *The predicted tides are obtained with the use of a harmonic 186SL080030105 analysis program (Foreman, 1977) which is executed on a year 186SL080030106 of apparently good data for a given station. The Predicted 186SL080030107 Tide Method for filling gaps consists of statistically 186SL080030108 comparing the predicted tides to the observed data and 186SL080030109 shifting the predicted tides in time to correct for timing 186SL080030110 differences. Then the linear interpolation between hourly 186SL080030111 values at the end points of the gap in the residual series is 186SL080030112 added to the corresponding corrected predicted tide data to 186SL080030113 obtain interpolated values over the span of the gap. 186SL080030114 186SL080030115 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL080030116 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL080030117 186SL080030118 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL080030119 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL080030120 Victoria B.C. Pacific Marine Science Report 77-10. 186SL080030121 186SL08006 19821 999999999999999999999999999999999999999999999999 186SL08006 19822 999999999999999999999999 2545030 2536000 2515000 186SL08006 19831 999999999999999999999999999999999999999999999999 186SL08006 19832 999999999999999999999999999999999999999999999999