186SL0894131015201 238A 19710630 19750513 1512S 01209E 2 00000R 0000 MM 186SL0894231015201 Mocamedes Angola Inst. Hidro. Marinha 186SL089430001 186SL089430002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL089430003 by the 186SL089430004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL089430005 JOINT ARCHIVE FOR SEA LEVEL 186SL089430006 186SL089430007Station : Mocamedes Latitude: 15 11.5S 186SL089430008Country : Angola Longitude: 012 08.7E 186SL089430009JASL # : 238A Time Meridian: 015E (GMT + 1 hr) 186SL089430010GLOSS # : none TOGA #: none NODC #: 31015201 186SL089430011Contributor : Instituto Hidrografico Marinha 186SL089430012 Rua das Trinas 186SL089430013 49-P-1296 Lisboa Codex 186SL089430014 Lisbon 186SL089430015 PORTUGAL 186SL089430016Originator : same 186SL089430017Original Data: analog 186SL089430018Instrmnt Type: Float and well, A.OTT 186SL089430019Digitzd Intvl: hourly 186SL089430020Present Data : Hourly, daily, and monthly values obtained by: 186SL089430021 Hourly : the original data were hourly 186SL089430022 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL089430023 centered on noon applied to the hourly data 186SL089430024 with respective periods of the 95, 50, and 5% 186SL089430025 amplitude points at 124.0, 60.2, and 40.2 hours 186SL089430026 Monthly: Simple average of all daily values; calculated if 186SL089430027 7 or fewer days are missing 186SL089430028Span of data : 30 Jun 1971 - 13 May 1975 186SL089430029Gaps > 1 mon : none 186SL089430030Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL089430031Units : millimeters Missing Data Flag :99999 186SL089430032Refernce Levl: All heights have been referred to the station tide 186SL089430033 staff zero which is linked to fixed bench marks 186SL089430034Comment : The daily and monthly means reveal no 186SL089430035 apparent reference level changes or trends and 186SL089430036 agree well with Lobito for same period. 186SL089430037 186SL089430038 CI MISSING REPLACED GAPS QUESTIONABLE 186SL089430039YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL089430040---- --- -------------------- --------------- -------------------- 186SL0894300411971 49 186-188,362-365 (23)271-(22)272 336-339,352-362 186SL0894300421972 94 1-18,326-330 none 32-33,47-48,58-63, 186SL089430043 71-78,321-325 186SL0894300441973 100 none (18)066-(07)067 none 186SL0894300451974 100 none none none 186SL0894300461975 36 none none none 186SL089430047 186SL089430048 QUALITY ASSESSMENT POLICY 186SL089430049 186SL089430050 The quality assessment is mostly based on the residuals 186SL089430051 (observed data minus predicted tides) of the hourly data. This 186SL089430052 assessment also applies to the daily and monthly data since 186SL089430053 they were derived from the quality-controlled hourly data. 186SL089430054 186SL089430055 The following abbreviations are used in the assessment: 186SL089430056 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL089430057 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL089430058 research program; NODC - National Oceanographic Data Center; 186SL089430059 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL089430060 Gaps > 1 mon - missing data in a span greater than one month; 186SL089430061 Refernce - reference. 186SL089430062 186SL089430063 The following corrections are made to the hourly data 186SL089430064 prior to this assessment: 186SL089430065 1) Gaps or obviously wrong data points in a span less than 186SL089430066 25 hours are filled by the predicted tide method*. 186SL089430067 2) Timing errors of exact increments of an hour are corrected 186SL089430068 by shifting the data. 186SL089430069 3) Reference level shifts are only corrected after information 186SL089430070 from tide staff readings or comparative readings with a fixed 186SL089430071 bench mark are checked to verify that the shift was not a 186SL089430072 natural event. If comparative readings are missing or 186SL089430073 incomplete, comparisons of the data with nearby stations 186SL089430074 may warrant the adjustment of some obvious shifts. 186SL089430075 4) Data with unresolved datum shifts are not disseminated. 186SL089430076 However, if sufficient time spans of data are available before 186SL089430077 or after the year(s) with the unresolved shift(s), a subset of 186SL089430078 quality assured data is made available. Thus, the Span field 186SL089430079 in the Quality Assessment may not match the span of the 186SL089430080 distribution data set. As the questionable datum shifts are 186SL089430081 resolved, the data set will be updated. Although this policy 186SL089430082 adds some complexity, it allows more rapid dissemination of 186SL089430083 at least the quality assured years. 186SL089430084 186SL089430085 For each year, the following information is documented from 186SL089430086 the quality-controlled hourly data with dates given as the nth 186SL089430087 day of the year starting from 1 January: 186SL089430088 1) a Completeness Index (CI) based on the percentage of hours 186SL089430089 with available data, 186SL089430090 2) a list of gaps longer than a day, 186SL089430091 3) a summary of days with consecutive missing or obviously 186SL089430092 wrong data in a time span longer than 6 but less than 25 186SL089430093 hours that have been replaced, with hours in parentheses, and 186SL089430094 4) a summary of days with questionable fluctuations in the 186SL089430095 residual series. Fluctuations within the residuals are 186SL089430096 considered significant and are noted if they are greater than 186SL089430097 25 cm. This policy has changed slightly as of October 1992: 186SL089430098 only suspicious fluctuations due to obvious instrumentation 186SL089430099 problems are noted. Minor timing drifts are no longer 186SL089430100 included in the list of questionable days. 186SL089430101 186SL089430102 Note : If the predicted tides poorly model the observed heights 186SL089430103 due to the inability of the tidal analysis to completely resolv 186SL089430104 the non-linear shallow water effects, the residuals are not 186SL089430105 suitable for assessing the data quality. Instead, a subjective 186SL089430106 comment on the quality of the data is provided. 186SL089430107 186SL089430108 *The predicted tides are obtained with the use of a harmonic 186SL089430109 analysis program (Foreman, 1977) which is executed on a year 186SL089430110 of apparently good data for a given station. The Predicted 186SL089430111 Tide Method for filling gaps consists of statistically 186SL089430112 comparing the predicted tides to the observed data and 186SL089430113 shifting the predicted tides in time to correct for timing 186SL089430114 differences. Then the linear interpolation between hourly 186SL089430115 values at the end points of the gap in the residual series is 186SL089430116 added to the corresponding corrected predicted tide data to 186SL089430117 obtain interpolated values over the span of the gap. 186SL089430118 186SL089430119 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL089430120 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL089430121 186SL089430122 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL089430123 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL089430124 Victoria B.C. Pacific Marine Science Report 77-10. 186SL089430125 186SL08946 19711 999999999999999999999999999999999999999999999999 186SL08946 19712 1060030 1088000 1115000 1133000 1128000 1144040 186SL08946 19721 99999999 1139000 1141000 1123000 1089000 1035000 186SL08946 19722 1032000 1048000 1081000 1101000 1152050 1151000 186SL08946 19731 1181000 1196000 1183000 1157000 1108000 1056000 186SL08946 19732 1078000 1056000 1109000 1157000 1143000 1081000 186SL08946 19741 1130000 1163000 1178000 1238000 1132000 1066000 186SL08946 19742 1058000 1058000 1088000 1115000 1104000 1102000 186SL08946 19751 1107000 1141000 1164000 11710009999999999999999 186SL08946 19752 999999999999999999999999999999999999999999999999