186SL0874112081901 134A 19770116 19901231 2147N 08928E 2 00000R 0000 MM 186SL0874212081901 Hiron Point Bangladesh BIWTA 186SL087430001 186SL087430002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL087430003 by the 186SL087430004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL087430005 JOINT ARCHIVE FOR SEA LEVEL 186SL087430006 186SL087430007Station : Hiron Point Latitude: 21 47.0N 186SL087430008Country : Bangladesh Longitude: 089 28.0E 186SL087430009JASL # : 134A Time Meridian: 090E (GMT + 6 hr) 186SL087430010GLOSS # : none TOGA #: none NODC #: 12081901 186SL087430011Contributor : Bangladesh Inland Water Transport Authority (BIWTA) 186SL087430012 Dept. of Hydrography 186SL087430013 141-143, Motijheel C/A 186SL087430014 Dhaka - 1000 186SL087430015 BANGLADESH 186SL087430016Originator : same 186SL087430017Original Data: unconfirmed 186SL087430018Instrmnt Type: float and well type gauge 186SL087430019Digitzd Intvl: unconfirmed 186SL087430020Present Data : Hourly, daily, and monthly values obtained by: 186SL087430021 Hourly : unconfirmed 186SL087430022 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL087430023 centered on noon applied to the hourly data 186SL087430024 with respective periods of the 95, 50, and 5% 186SL087430025 amplitude points at 124.0, 60.2, and 40.2 hours 186SL087430026 Monthly: Simple average of all daily values; calculated if 186SL087430027 7 or fewer days are missing 186SL087430028Span of data : 16 Jan 1977 - 31 Dec 1990 186SL087430029Gaps > 1 mon : none 186SL087430030Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL087430031Units : millimeters Missing Data Flag :99999 186SL087430032Refernce Levl: The sea level heights are referred to the zero 186SL087430033 point assigned to the tide staff. Bench mark 186SL087430034 information is available upon request from BIWTA. 186SL087430035 Level shifts were identified in the series and 186SL087430036 adjusted as follows for a short time segment: 186SL087430037 value added 186SL087430038 period (hour)day/month/year to original(mm) 186SL087430039 ----------------------------- --------------- 186SL087430040 (18)31/10/1982-(16)31/12/1982 430 186SL087430041 This adjustment is uncertain to a few cm. 186SL087430042Comment : The daily and monthly means do not reveal any 186SL087430043 reference level shifts or trends. The data are 186SL087430044 of good quality. Numerous short gaps were inter- 186SL087430045 polated during July-August 1977. Occassional 186SL087430046 minor timing drifts occurred throughout the record. 186SL087430047 186SL087430048 CI MISSING REPLACED GAPS QUESTIONABLE 186SL087430049YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL087430050---- --- -------------------- --------------- -------------------- 186SL0874300511977 96 151-152 (08)156-(01)157 122-125,137-140,152- 186SL087430052 (13)178-(23)178 154 186SL087430053 (13)179-(23)179 186SL087430054 (13)180-(00)181 186SL087430055 (13)181-(23)181 186SL087430056 (13)182-(23)182 186SL087430057 (13)183-(00)184 186SL087430058 (12)184-(23)184 186SL087430059 (08)185-(23)185 186SL087430060 (13)186-(23)186 186SL087430061 (13)187-(23)187 186SL087430062 (13)188-(23)188 186SL087430063 (13)189-(23)189 186SL087430064 (13)190-(23)190 186SL087430065 (13)191-(23)191 186SL087430066 (13)192-(23)192 186SL087430067 (12)193-(23)193 186SL087430068 (13)194-(23)194 186SL087430069 (13)195-(23)195 186SL087430070 (13)196-(23)196 186SL087430071 (13)197-(23)197 186SL087430072 (13)198-(00)199 186SL087430073 (13)199-(23)199 186SL087430074 (13)200-(23)200 186SL087430075 (13)201-(23)201 186SL087430076 (13)202-(23)202 186SL087430077 (13)203-(23)203 186SL087430078 (12)204-(23)204 186SL087430079 (12)205-(23)205 186SL087430080 (12)206-(23)206 186SL087430081 (13)207-(00)208 186SL087430082 (13)208-(00)209 186SL087430083 (13)209-(23)209 186SL087430084 (12)210-(00)211 186SL087430085 (12)211-(00)212 186SL087430086 (13)212-(23)212 186SL087430087 (13)213-(00)214 186SL087430088 (13)214-(23)214 186SL087430089 (13)215-(23)215 186SL087430090 (13)216-(00)217 186SL087430091 (13)217-(23)217 186SL087430092 (13)218-(23)218 186SL087430093 (13)219-(00)220 186SL087430094 (13)220-(23)220 186SL087430095 (13)221-(23)221 186SL087430096 (13)222-(23)222 186SL087430097 (13)223-(23)223 186SL087430098 (13)224-(23)224 186SL087430099 (13)225-(00)226 186SL087430100 (12)226-(23)226 186SL087430101 (12)227-(23)227 186SL087430102 (15)284-(23)284 186SL0874301031978 100 none (15)239-(01)240 none 186SL087430104 (14)242-(03)243 186SL087430105 (13)257-(01)258 186SL087430106 (21)263-(09)264 186SL087430107 (19)283-(07)284 186SL087430108 (06)298-(22)298 186SL0874301091979 98 44-45,325-330, (14)105-(02)106 160-165 186SL087430110 352-353 (03)183-(01)184 186SL087430111 (13)201-(01)202 186SL087430112 (05)234-(03)235 186SL087430113 (04)239-(03)240 186SL087430114 (05)286-(03)287 186SL0874301151980 96 9-11,166-175,265- (11)022-(04)023 none 186SL087430116 267,357-360 (12)035-(00)036 186SL087430117 (11)036-(01)037 186SL087430118 (13)037-(01)038 186SL087430119 (13)038-(00)039 186SL087430120 (15)138-(22)138 186SL087430121 (08)335-(17)335 186SL0874301221981 99 52-54,107-108,179- none none 186SL087430123 181 186SL0874301241982 99 52-53,313-314 (09)304-(20)304 none 186SL0874301251983 100 none (19)155-(05)156 77-82,323 186SL087430126 (21)156-(06)157 186SL087430127 (21)157-(06)158 186SL0874301281984 99 159-160 (08)051-(16)051 none 186SL087430129 (05)285-(04)286 186SL0874301301985 100 none (13)137-(21)137 none 186SL087430131 (05)265-(18)265 186SL0874301321986 100 none none none 186SL0874301331987 99 321-324 (21)161-(17)162 119-120,123 186SL0874301341988 99 244-245 (07)265-(01)266 55 186SL0874301351989 99 198-199,200-201 (06)038-(17)038 93-97 186SL087430136 (08)100-(06)101 186SL087430137 (11)211-(18)211 186SL087430138 (16)218-(23)218 186SL087430139 (15)219-(23)219 186SL0874301401990 99 126-129,365 none none 186SL087430141 186SL087430142 QUALITY ASSESSMENT POLICY 186SL087430143 186SL087430144 The quality assessment is mostly based on the residuals 186SL087430145 (observed data minus predicted tides) of the hourly data. This 186SL087430146 assessment also applies to the daily and monthly data since 186SL087430147 they were derived from the quality-controlled hourly data. 186SL087430148 186SL087430149 The following abbreviations are used in the assessment: 186SL087430150 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL087430151 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL087430152 research program; NODC - National Oceanographic Data Center; 186SL087430153 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL087430154 Gaps > 1 mon - missing data in a span greater than one month; 186SL087430155 Refernce - reference. 186SL087430156 186SL087430157 The following corrections are made to the hourly data 186SL087430158 prior to this assessment: 186SL087430159 1) Gaps or obviously wrong data points in a span less than 186SL087430160 25 hours are filled by the predicted tide method*. 186SL087430161 2) Timing errors of exact increments of an hour are corrected 186SL087430162 by shifting the data. 186SL087430163 3) Reference level shifts are only corrected after information 186SL087430164 from tide staff readings or comparative readings with a fixed 186SL087430165 bench mark are checked to verify that the shift was not a 186SL087430166 natural event. If comparative readings are missing or 186SL087430167 incomplete, comparisons of the data with nearby stations 186SL087430168 may warrant the adjustment of some obvious shifts. 186SL087430169 4) Data with unresolved datum shifts are not disseminated. 186SL087430170 However, if sufficient time spans of data are available before 186SL087430171 or after the year(s) with the unresolved shift(s), a subset of 186SL087430172 quality assured data is made available. Thus, the Span field 186SL087430173 in the Quality Assessment may not match the span of the 186SL087430174 distribution data set. As the questionable datum shifts are 186SL087430175 resolved, the data set will be updated. Although this policy 186SL087430176 adds some complexity, it allows more rapid dissemination of 186SL087430177 at least the quality assured years. 186SL087430178 186SL087430179 For each year, the following information is documented from 186SL087430180 the quality-controlled hourly data with dates given as the nth 186SL087430181 day of the year starting from 1 January: 186SL087430182 1) a Completeness Index (CI) based on the percentage of hours 186SL087430183 with available data, 186SL087430184 2) a list of gaps longer than a day, 186SL087430185 3) a summary of days with consecutive missing or obviously 186SL087430186 wrong data in a time span longer than 6 but less than 25 186SL087430187 hours that have been replaced, with hours in parentheses, and 186SL087430188 4) a summary of days with questionable fluctuations in the 186SL087430189 residual series. Fluctuations within the residuals are 186SL087430190 considered significant and are noted if they are greater than 186SL087430191 25 cm. This policy has changed slightly as of October 1992: 186SL087430192 only suspicious fluctuations due to obvious instrumentation 186SL087430193 problems are noted. Minor timing drifts are no longer 186SL087430194 included in the list of questionable days. 186SL087430195 186SL087430196 Note : If the predicted tides poorly model the observed heights 186SL087430197 due to the inability of the tidal analysis to completely resolv 186SL087430198 the non-linear shallow water effects, the residuals are not 186SL087430199 suitable for assessing the data quality. Instead, a subjective 186SL087430200 comment on the quality of the data is provided. 186SL087430201 186SL087430202 *The predicted tides are obtained with the use of a harmonic 186SL087430203 analysis program (Foreman, 1977) which is executed on a year 186SL087430204 of apparently good data for a given station. The Predicted 186SL087430205 Tide Method for filling gaps consists of statistically 186SL087430206 comparing the predicted tides to the observed data and 186SL087430207 shifting the predicted tides in time to correct for timing 186SL087430208 differences. Then the linear interpolation between hourly 186SL087430209 values at the end points of the gap in the residual series is 186SL087430210 added to the corresponding corrected predicted tide data to 186SL087430211 obtain interpolated values over the span of the gap. 186SL087430212 186SL087430213 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL087430214 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL087430215 186SL087430216 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL087430217 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL087430218 Victoria B.C. Pacific Marine Science Report 77-10. 186SL087430219 186SL08746 19771 99999999 1322000 1365000 1538000 1795010 1986010 186SL08746 19772 2035000 2004000 1922000 1731000 1654000 1580000 186SL08746 19781 1359000 1373000 1339000 1565000 1866000 1997000 186SL08746 19782 1984000 2219000 1972000 1924000 1690000 1490000 186SL08746 19791 1424000 1324020 1400000 1586000 1762000 1872000 186SL08746 19792 1998000 2065000 2023000 1985000 1786060 1665020 186SL08746 19801 1457030 1431000 1486000 1636000 189300099999999 186SL08746 19802 2150000 2130000 2132030 2065000 1769000 1672040 186SL08746 19811 1472000 1353030 1419000 1617020 1812000 2101030 186SL08746 19812 2018000 2150000 1976000 1836000 1953000 1687000 186SL08746 19821 1454000 1415020 1436000 1685000 1731000 2062000 186SL08746 19822 2026000 2075000 1931000 1671000 1535020 1396000 186SL08746 19831 1401000 1347000 1495000 1591000 1780000 2005000 186SL08746 19832 2020000 2091000 2014000 1936000 2079000 1707000 186SL08746 19841 1638000 1508000 1599000 1717000 1967000 2145020 186SL08746 19842 2167000 2173000 2099000 2071000 1707000 1668000 186SL08746 19851 1495000 1464000 1590000 1540000 1875000 2148000 186SL08746 19852 2098000 2110000 2062000 2067000 1917000 1700000 186SL08746 19861 1511000 1446000 1485000 1707000 1859000 1967000 186SL08746 19862 2108000 2145000 2176000 2048000 1892000 1534000 186SL08746 19871 1424000 1508000 1426000 1584000 1775000 2072000 186SL08746 19872 2155000 2117000 2014000 1931000 1987040 1797000 186SL08746 19881 1542000 1554000 1516000 1701000 1996000 2177000 186SL08746 19882 2081000 2134010 2073010 2009000 1912000 1718000 186SL08746 19891 1440000 1488000 1474000 1613000 1959000 2135000 186SL08746 19892 2060040 2114000 1991000 1972000 1836000 1557000 186SL08746 19901 1419000 1452000 1479000 1647000 1819040 2120000 186SL08746 19902 1982000 2259000 2065000 1946000 1900000 1637010