186SL0770112053801 110A 19870403 19930812 2338N 05834E 2 00000R 0000 MM 186SL0770212053801 Muscat Oman Dir. of Meteorology CIVAIR 186SL077030001 186SL077030002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL077030003 by the 186SL077030004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL077030005 JOINT ARCHIVE FOR SEA LEVEL 186SL077030006 186SL077030007Station : Muscat Latitude: 23 37.7N 186SL077030008Country : Oman Longitude: 058 33.9E 186SL077030009JASL # : 110A Time Meridian: 060E (GMT + 4 hr) 186SL077030010GLOSS # : 005 TOGA #: I016 NODC #: 12053801 186SL077030011Contributor : Director of Meteorology CIVAIR 186SL077030012 SEEB International Airport 186SL077030013 P. O. Box 204 186SL077030014 Muscat, Sultanate of Oman 186SL077030015Originator : same 186SL077030016Original Data: analog (L&S); digital (F&P) 186SL077030017Instrmnt Type: (04/1987-07/1989) Leupold and Stevens Analog gauge; 186SL077030018 (08/1989-present) Fischer and Porter Analog-to- 186SL077030019 Digital Recorder, model 1551 186SL077030020Digitzd Intvl: hourly (L&S); 15 minutes (F&P) 186SL077030021Present Data : Hourly, daily, and monthly values obtained by: 186SL077030022 Hourly : Original data were spot hourly (L&S); A three- 186SL077030023 point Hanning filter centered on the hour (F&P) 186SL077030024 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL077030025 centered on noon applied to the hourly data 186SL077030026 with respective periods of the 95, 50, and 5% 186SL077030027 amplitude points at 124.0, 60.2, and 40.2 hours 186SL077030028 Monthly: Simple average of all daily values; calculated if 186SL077030029 7 or fewer days are missing 186SL077030030Span of data : 03 Apr 1987 - 12 Aug 1993 186SL077030031Gaps > 1 mon : 02 Oct - 27 Nov 1987; 18 Aug - 08 Oct 1990 186SL077030032 23 Jan - 25 Nov 1992; 02 Jan - 06 Mar 1993 186SL077030033Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL077030034Units : millimeters Missing Data Flag :99999 186SL077030035Refernce Levl: The sea level heights are referred to the zero 186SL077030036 point assigned to the tide gauge. 186SL077030037Comment : The daily and monthly values do not reveal any 186SL077030038 obvious reference level shifts or trends. The 186SL077030039 analog hourly data contain many timing errors as 186SL077030040 noted below under questionable fluctuations. 186SL077030041 The accuracy of the timing improves significantly 186SL077030042 in 1991. 186SL077030043 186SL077030044 CI MISSING REPLACED GAPS QUESTIONABLE 186SL077030045YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL077030046---- --- -------------------- --------------- -------------------- 186SL0770300471987 54 150-153,159-163, (01)156-(17)156 131,139-140,149-150, 186SL077030048 177-179,217-222, (12)163-(23)163 153,169,171,197-199, 186SL077030049 275-332,344-346, (11)234-(06)235 204-205,211-212,214- 186SL077030050 356-359 (12)247-(03)248 217,225-230,233,237- 186SL077030051 (02)336-(23)336 243,245-274,332-335, 186SL077030052 339-343,346-356,359- 186SL077030053 361,364 186SL0770300541988 100 none (18)043-(03)044 1-11,16-20,22-23,33, 186SL077030055 (13)055-(04)056 35-37,39,44-47,50- 186SL077030056 (11)118-(08)119 51,53,60,63-64,68- 186SL077030057 69,76-80,92-95,99- 186SL077030058 101,103,106-109,125- 186SL077030059 126,131-132,134,136- 186SL077030060 138,190,143-144,154- 186SL077030061 157,159,182,240-242 186SL0770300621989 93 119-121,158-168, none 124-130,136-138,141, 186SL077030063 199-213 150,152 186SL0770300641990 83 133-145,231-281 none 1,112,130-131,146- 186SL077030065 148,219,222,229-230 186SL0770300661991 98 108-117 none none 186SL0770300671992 16 23-330 none none 186SL0770300681993 44 2-65 none none 186SL077030069 186SL077030070 QUALITY ASSESSMENT POLICY 186SL077030071 186SL077030072 The quality assessment is mostly based on the residuals 186SL077030073 (observed data minus predicted tides) of the hourly data. This 186SL077030074 assessment also applies to the daily and monthly data since 186SL077030075 they were derived from the quality-controlled hourly data. 186SL077030076 186SL077030077 The following abbreviations are used in the assessment: 186SL077030078 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL077030079 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL077030080 research program; NODC - National Oceanographic Data Center; 186SL077030081 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL077030082 Gaps > 1 mon - missing data in a span greater than one month; 186SL077030083 Refernce - reference. 186SL077030084 186SL077030085 The following corrections are made to the hourly data 186SL077030086 prior to this assessment: 186SL077030087 1) Gaps or obviously wrong data points in a span less than 186SL077030088 25 hours are filled by the predicted tide method*. 186SL077030089 2) Timing errors of exact increments of an hour are corrected 186SL077030090 by shifting the data. 186SL077030091 3) Reference level shifts are only corrected after information 186SL077030092 from tide staff readings or comparative readings with a fixed 186SL077030093 bench mark are checked to verify that the shift was not a 186SL077030094 natural event. If comparative readings are missing or 186SL077030095 incomplete, comparisons of the data with nearby stations 186SL077030096 may warrant the adjustment of some obvious shifts. 186SL077030097 4) Data with unresolved datum shifts are not disseminated. 186SL077030098 However, if sufficient time spans of data are available before 186SL077030099 or after the year(s) with the unresolved shift(s), a subset of 186SL077030100 quality assured data is made available. Thus, the Span field 186SL077030101 in the Quality Assessment may not match the span of the 186SL077030102 distribution data set. As the questionable datum shifts are 186SL077030103 resolved, the data set will be updated. Although this policy 186SL077030104 adds some complexity, it allows more rapid dissemination of 186SL077030105 at least the quality assured years. 186SL077030106 186SL077030107 For each year, the following information is documented from 186SL077030108 the quality-controlled hourly data with dates given as the nth 186SL077030109 day of the year starting from 1 January: 186SL077030110 1) a Completeness Index (CI) based on the percentage of hours 186SL077030111 with available data, 186SL077030112 2) a list of gaps longer than a day, 186SL077030113 3) a summary of days with consecutive missing or obviously 186SL077030114 wrong data in a time span longer than 6 but less than 25 186SL077030115 hours that have been replaced, with hours in parentheses, and 186SL077030116 4) a summary of days with questionable fluctuations in the 186SL077030117 residual series. Fluctuations within the residuals are 186SL077030118 considered significant and are noted if they are greater than 186SL077030119 25 cm. This policy has changed slightly as of October 1992: 186SL077030120 only suspicious fluctuations due to obvious instrumentation 186SL077030121 problems are noted. Minor timing drifts are no longer 186SL077030122 included in the list of questionable days. 186SL077030123 186SL077030124 Note : If the predicted tides poorly model the observed heights 186SL077030125 due to the inability of the tidal analysis to completely resolv 186SL077030126 the non-linear shallow water effects, the residuals are not 186SL077030127 suitable for assessing the data quality. Instead, a subjective 186SL077030128 comment on the quality of the data is provided. 186SL077030129 186SL077030130 *The predicted tides are obtained with the use of a harmonic 186SL077030131 analysis program (Foreman, 1977) which is executed on a year 186SL077030132 of apparently good data for a given station. The Predicted 186SL077030133 Tide Method for filling gaps consists of statistically 186SL077030134 comparing the predicted tides to the observed data and 186SL077030135 shifting the predicted tides in time to correct for timing 186SL077030136 differences. Then the linear interpolation between hourly 186SL077030137 values at the end points of the gap in the residual series is 186SL077030138 added to the corresponding corrected predicted tide data to 186SL077030139 obtain interpolated values over the span of the gap. 186SL077030140 186SL077030141 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL077030142 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL077030143 186SL077030144 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL077030145 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL077030146 Victoria B.C. Pacific Marine Science Report 77-10. 186SL077030147 186SL07706 19871 999999999999999999999999 2223030 231602099999999 186SL07706 19872 2384000 2311060 23230009999999999999999 2158070 186SL07706 19881 2197000 2229000 2259000 2282000 2346000 2453000 186SL07706 19882 2436000 2360000 2366000 2296000 2343000 2360000 186SL07706 19891 2313000 2261000 2302000 2318020 228501099999999 186SL07706 19892 99999999 2405000 2372000 2351000 2373000 2418000 186SL07706 19901 2347000 2361000 2325000 238900099999999 2420000 186SL07706 19902 2461000999999999999999999999999 2247000 2296000 186SL07706 19911 2285000 2227000 227400099999999 2362000 2329000 186SL07706 19912 2351000 2317000 2252000 2239000 2267000 2290000 186SL07706 19921 999999999999999999999999999999999999999999999999 186SL07706 19922 9999999999999999999999999999999999999999 2296000 186SL07706 19931 9999999999999999 2209050 2239000 2363000 2402000 186SL07706 19932 23980009999999999999999999999999999999999999999