186SL0764130034901 101A 19860617 19931231 0404S 03939E 2 00000R 0000 MM 186SL0764230034901 Mombasa Kenya Kenya Marine and Fisheries 186SL076430001 186SL076430002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL076430003 by the 186SL076430004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL076430005 JOINT ARCHIVE FOR SEA LEVEL 186SL076430006 186SL076430007Station : Mombasa Latitude: 04 04.2S 186SL076430008Country : Kenya Longitude: 039 39.4E 186SL076430009JASL # : 101A Time Meridian: 045E (GMT + 3 hr) 186SL076430010GLOSS # : 008 TOGA #: I005 NODC #: 30034901 186SL076430011Contributor : Kenya Marine and Fisheries Institute 186SL076430012 P. O. Box 81651 186SL076430013 Mombasa, Kenya 186SL076430014Originator : same 186SL076430015Original Data: analog 186SL076430016Instrmnt Type: Leupold and Stevens, model A-71, float gauge 186SL076430017Digitzd Intvl: one hour spot reading 186SL076430018Present Data : Hourly, daily, and monthly values obtained by: 186SL076430019 Hourly : The original digitizing interval was hourly 186SL076430020 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL076430021 centered on noon applied to the hourly data 186SL076430022 with respective periods of the 95, 50, and 5% 186SL076430023 amplitude points at 124.0, 60.2, and 40.2 hours 186SL076430024 Monthly: Simple average of all daily values; calculated if 186SL076430025 7 or fewer days are missing 186SL076430026Span of data : 17 Jun 1986 - 31 Dec 1993 186SL076430027Gaps > 1 mon : 06 Nov 1987 - 29 Feb 1988;01 Dec 1990 - 04 Aug 1991 186SL076430028Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL076430029Units : millimeters Missing Data Flag :99999 186SL076430030Refernce Levl: The sea level heights are referred to the zero 186SL076430031 point assigned to the tide staff. Bench mark 186SL076430032 information is available upon request. 186SL076430033Comment : The daily and monthly means do not reveal any 186SL076430034 reference level shifts and agree well with an 186SL076430035 adjacent station, Zanzibar, except for about a 186SL076430036 10 day period of 9-20 Feb 1990 when the daily 186SL076430037 values show a suspicious drop. This feature is 186SL076430038 not identifiable in the tide staff observations. 186SL076430039 The timing of the hourly data is uncertain to 186SL076430040 about 4 minutes for most of the record with 186SL076430041 periods of less accurracy as noted below under 186SL076430042 questionable fluctuations. The timing is more 186SL076430043 accurate in 1992. 186SL076430044 186SL076430045 CI MISSING REPLACED GAPS QUESTIONABLE 186SL076430046YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL076430047---- --- -------------------- --------------- -------------------- 186SL0764300481986 51 254-258,304-308, (13)216-(00)217 175,214-215,231-233, 186SL076430049 333-335,355-357 (15)217-(23)217 260-264,282,317-319, 186SL076430050 (19)219-(06)220 358-360 186SL076430051 (23)222-(08)223 186SL076430052 (02)320-(19)320 186SL076430053 (01)324-(19)324 186SL0764300541987 78 37-40,130-132, (13)048-(21)048 59-60,67,73-74,80- 186SL076430055 147-159,215-222, (17)050-(03)051 84,88-89,91,93,106, 186SL076430056 310-365 (20)052-(05)053 134,142-147,168-169, 186SL076430057 (12)136-(22)136 173,177-178,194-195, 186SL076430058 (00)137-(10)137 214,222,224,227-228, 186SL076430059 (18)160-(05)161 275-278,281 186SL076430060 (14)161-(23)161 186SL076430061 (04)171-(23)171 186SL0764300621988 93 1-59,94-96, none 79-81,83-84,93-94, 186SL076430063 151-154,232-243, 100-103,108-110,129- 186SL076430064 245-252,332-335 130,139-142,150-151, 186SL076430065 245,268-270,319,337, 186SL076430066 344-345 186SL0764300671989 98 104-107,122-124, none 6-7,27,39,66-67,69, 186SL076430068 242-244 78-79,87,97-99,126, 186SL076430069 137-139,152-162,164, 186SL076430070 166,169-178,183-184, 186SL076430071 186-191,200-201,213- 186SL076430072 214,216-218,228-232, 186SL076430073 241,286-291,341-342 186SL0764300741990 75 17-22,53-59, none 10,23,29,40-41,61- 186SL076430075 145-150,161-164, 62,66,69-73,84,86- 186SL076430076 199-218,226-236, 91,94-95,97,100-106, 186SL076430077 255-263,290-292, 117-120,125-126,130- 186SL076430078 305-309 131,138-139,150-159, 186SL076430079 164-181,187-190,192- 186SL076430080 198,237-239,247-152, 186SL076430081 275-280,288-290,300- 186SL076430082 302,304,309-310,314- 186SL076430083 315,318,322-323,327- 186SL076430084 328,333 186SL0764300851991 41 1-216 none 221-226,238-241,253- 186SL076430086 256 186SL0764300871992 99 11-13 none none 186SL0764300881993 99 151-153,303-304 none none 186SL076430089 186SL076430090 QUALITY ASSESSMENT POLICY 186SL076430091 186SL076430092 The quality assessment is mostly based on the residuals 186SL076430093 (observed data minus predicted tides) of the hourly data. This 186SL076430094 assessment also applies to the daily and monthly data since 186SL076430095 they were derived from the quality-controlled hourly data. 186SL076430096 186SL076430097 The following abbreviations are used in the assessment: 186SL076430098 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL076430099 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL076430100 research program; NODC - National Oceanographic Data Center; 186SL076430101 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL076430102 Gaps > 1 mon - missing data in a span greater than one month; 186SL076430103 Refernce - reference. 186SL076430104 186SL076430105 The following corrections are made to the hourly data 186SL076430106 prior to this assessment: 186SL076430107 1) Gaps or obviously wrong data points in a span less than 186SL076430108 25 hours are filled by the predicted tide method*. 186SL076430109 2) Timing errors of exact increments of an hour are corrected 186SL076430110 by shifting the data. 186SL076430111 3) Reference level shifts are only corrected after information 186SL076430112 from tide staff readings or comparative readings with a fixed 186SL076430113 bench mark are checked to verify that the shift was not a 186SL076430114 natural event. If comparative readings are missing or 186SL076430115 incomplete, comparisons of the data with nearby stations 186SL076430116 may warrant the adjustment of some obvious shifts. 186SL076430117 4) Data with unresolved datum shifts are not disseminated. 186SL076430118 However, if sufficient time spans of data are available before 186SL076430119 or after the year(s) with the unresolved shift(s), a subset of 186SL076430120 quality assured data is made available. Thus, the Span field 186SL076430121 in the Quality Assessment may not match the span of the 186SL076430122 distribution data set. As the questionable datum shifts are 186SL076430123 resolved, the data set will be updated. Although this policy 186SL076430124 adds some complexity, it allows more rapid dissemination of 186SL076430125 at least the quality assured years. 186SL076430126 186SL076430127 For each year, the following information is documented from 186SL076430128 the quality-controlled hourly data with dates given as the nth 186SL076430129 day of the year starting from 1 January: 186SL076430130 1) a Completeness Index (CI) based on the percentage of hours 186SL076430131 with available data, 186SL076430132 2) a list of gaps longer than a day, 186SL076430133 3) a summary of days with consecutive missing or obviously 186SL076430134 wrong data in a time span longer than 6 but less than 25 186SL076430135 hours that have been replaced, with hours in parentheses, and 186SL076430136 4) a summary of days with questionable fluctuations in the 186SL076430137 residual series. Fluctuations within the residuals are 186SL076430138 considered significant and are noted if they are greater than 186SL076430139 25 cm. This policy has changed slightly as of October 1992: 186SL076430140 only suspicious fluctuations due to obvious instrumentation 186SL076430141 problems are noted. Minor timing drifts are no longer 186SL076430142 included in the list of questionable days. 186SL076430143 186SL076430144 Note : If the predicted tides poorly model the observed heights 186SL076430145 due to the inability of the tidal analysis to completely resolv 186SL076430146 the non-linear shallow water effects, the residuals are not 186SL076430147 suitable for assessing the data quality. Instead, a subjective 186SL076430148 comment on the quality of the data is provided. 186SL076430149 186SL076430150 *The predicted tides are obtained with the use of a harmonic 186SL076430151 analysis program (Foreman, 1977) which is executed on a year 186SL076430152 of apparently good data for a given station. The Predicted 186SL076430153 Tide Method for filling gaps consists of statistically 186SL076430154 comparing the predicted tides to the observed data and 186SL076430155 shifting the predicted tides in time to correct for timing 186SL076430156 differences. Then the linear interpolation between hourly 186SL076430157 values at the end points of the gap in the residual series is 186SL076430158 added to the corresponding corrected predicted tide data to 186SL076430159 obtain interpolated values over the span of the gap. 186SL076430160 186SL076430161 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL076430162 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL076430163 186SL076430164 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL076430165 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL076430166 Victoria B.C. Pacific Marine Science Report 77-10. 186SL076430167 186SL07646 19861 999999999999999999999999999999999999999999999999 186SL07646 19862 2806000 2794000 2840050 2840010 2815060 2780040 186SL07646 19871 2757000 2828040 2889000 29460009999999999999999 186SL07646 19872 288700099999999 2834000 28940009999999999999999 186SL07646 19881 9999999999999999 2902000 2913030 2951020 2884020 186SL07646 19882 28860009999999999999999 2837000 2817040 2828000 186SL07646 19891 2801000 2786000 2880000 2918040 2901030 2858000 186SL07646 19892 2823000 2819020 2883010 2882000 2873000 2857000 186SL07646 19901 2827060 2781070 2865000 2936000 2927060 2852040 186SL07646 19902 999999999999999999999999 2880030 284705099999999 186SL07646 19911 999999999999999999999999999999999999999999999999 186SL07646 19912 99999999 2821040 2847000 2879000 2846000 2867000 186SL07646 19921 2799030 2858000 2890000 2916000 2912000 2905000 186SL07646 19922 2888000 2872000 2842000 2857000 2861000 2844000 186SL07646 19931 2870000 2863000 2875000 2916000 2920010 2889020 186SL07646 19932 2864000 2854000 2853000 28490209999999999999999