186SL0956112101901 636A 19750101 19901231 2129N 10905E 2 00000R 0000 MM 186SL0956212101901 Beihai China PRC Nat. Ocean. Data Center 186SL095630001 186SL095630002 QUALITY ASSESSMENT OF SEA LEVEL DATA 186SL095630003 by the 186SL095630004 TOGA SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER 186SL095630005 JOINT ARCHIVE FOR SEA LEVEL 186SL095630006 186SL095630007Station : Beihai Latitude: 21 29.0N 186SL095630008Country : China Longitude: 109 05.0E 186SL095630009JASL # : 636A Time Meridian: 120E (GMT + 8 hr) 186SL095630010GLOSS # : none TOGA #: none NODC #: 12101901 186SL095630011Contributor : PRC National Oceanographic Data Center 186SL095630012 118, Qiwei Road, Hedong 186SL095630013 District Tianjin, China 186SL095630014Originator : same 186SL095630015Original Data: analog 186SL095630016Instrmnt Type: unconfirmed (1975-84); HCJ-1 Float gauge (1985); 186SL095630017 SCA1-1 Float gauge (1986-90) 186SL095630018Digitzd Intvl: hourly 186SL095630019Present Data : Hourly, daily, and monthly values obtained by: 186SL095630020 Hourly : digitized as hourly values 186SL095630021 Daily : 119-point convolution filter (Bloomfield, 1976) 186SL095630022 centered on noon applied to the hourly data 186SL095630023 with respective periods of the 95, 50, and 5% 186SL095630024 amplitude points at 124.0, 60.2, and 40.2 hours 186SL095630025 Monthly: Simple average of all daily values; calculated if 186SL095630026 7 or fewer days are missing 186SL095630027Span of data : 01 Jan 1975 - 31 Dec 1990 186SL095630028Gaps > 1 mon : none 186SL095630029Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 186SL095630030Units : millimeters Missing Data Flag :99999 186SL095630031Refernce Levl: The sea level heights are referred to the Tide 186SL095630032 Gauge Zero (TGZ) which is linked to fixed bench 186SL095630033 marks. Bench mark information is 186SL095630034 available upon request from the contributors. 186SL095630035Comment : The residual series are very noisy which are 186SL095630036 probably due to shallow water tides that are not 186SL095630037 resolved by the harmonic analysis. Also the daily 186SL095630038 plot shows noise due to a great amount of energy 186SL095630039 with periods from 1 to 5 days. The mean level is 186SL095630040 steady. This data set is of good quality. 186SL095630041 186SL095630042 CI MISSING REPLACED GAPS QUESTIONABLE 186SL095630043YEAR (%) DATA OR BAD DATA FLUCTUATIONS 186SL095630044---- --- -------------------- --------------- -------------------- 186SL0956300451975 100 none (01)168-(23)168 see comment above 186SL095630046 (21)196-(04)197 186SL095630047 (05)199-(23)199 186SL095630048 (04)201-(23)201 186SL095630049 (03)240-(23)240 186SL095630050 (11)241-(23)241 186SL095630051 (03)312-(23)312 186SL095630052 (09)317-(00)318 186SL095630053 (04)319-(00)320 186SL0956300541976 97 99-103,114-115, (12)097-(23)097 see comment above 186SL095630055 214-219,289-293 (14)104-(02)105 186SL095630056 (11)105-(00)106 186SL095630057 (16)211-(23)211 186SL095630058 (04)212-(23)212 186SL095630059 (10)213-(23)213 186SL0956300601977 99 205-207 (16)107-(23)107 see comment above 186SL095630061 (16)203-(15)204 186SL095630062 (01)205-(11)205 186SL095630063 (14)207-(00)208 186SL095630064 (11)223-(23)223 186SL0956300651978 100 none none see comment above 186SL0956300661979 100 none (16)090-(23)090 see comment above 186SL0956300671980 100 none (16)203-(23)203 see comment above 186SL0956300681981 100 none (14)298-(23)298 see comment above 186SL0956300691982 100 none none see comment above 186SL0956300701983 100 none (15)071-(23)071 see comment above 186SL0956300711984 100 none none see comment above 186SL0956300721985 100 none (13)289-(23)289 see comment above 186SL0956300731986 100 none none see comment above 186SL0956300741987 100 none none see comment above 186SL0956300751988 100 none none see comment above 186SL0956300761989 100 none (13)157-(23)157 see comment above 186SL0956300771990 100 none none see comment above 186SL095630078 186SL095630079 QUALITY ASSESSMENT POLICY 186SL095630080 186SL095630081 The quality assessment is mostly based on the residuals 186SL095630082 (observed data minus predicted tides) of the hourly data. This 186SL095630083 assessment also applies to the daily and monthly data since 186SL095630084 they were derived from the quality-controlled hourly data. 186SL095630085 186SL095630086 The following abbreviations are used in the assessment: 186SL095630087 JASL - Joint Archive for Sea Level; GLOSS - Global Sea Level 186SL095630088 Observing System; TOGA - Tropical Ocean Global Atmosphere 186SL095630089 research program; NODC - National Oceanographic Data Center; 186SL095630090 Instrmnt - instrument; Digitzd Intvl - digitized interval; 186SL095630091 Gaps > 1 mon - missing data in a span greater than one month; 186SL095630092 Refernce - reference. 186SL095630093 186SL095630094 The following corrections are made to the hourly data 186SL095630095 prior to this assessment: 186SL095630096 1) Gaps or obviously wrong data points in a span less than 186SL095630097 25 hours are filled by the predicted tide method*. 186SL095630098 2) Timing errors of exact increments of an hour are corrected 186SL095630099 by shifting the data. 186SL095630100 3) Reference level shifts are only corrected after information 186SL095630101 from tide staff readings or comparative readings with a fixed 186SL095630102 bench mark are checked to verify that the shift was not a 186SL095630103 natural event. If comparative readings are missing or 186SL095630104 incomplete, comparisons of the data with nearby stations 186SL095630105 may warrant the adjustment of some obvious shifts. 186SL095630106 4) Data with unresolved datum shifts are not disseminated. 186SL095630107 However, if sufficient time spans of data are available before 186SL095630108 or after the year(s) with the unresolved shift(s), a subset of 186SL095630109 quality assured data is made available. Thus, the Span field 186SL095630110 in the Quality Assessment may not match the span of the 186SL095630111 distribution data set. As the questionable datum shifts are 186SL095630112 resolved, the data set will be updated. Although this policy 186SL095630113 adds some complexity, it allows more rapid dissemination of 186SL095630114 at least the quality assured years. 186SL095630115 186SL095630116 For each year, the following information is documented from 186SL095630117 the quality-controlled hourly data with dates given as the nth 186SL095630118 day of the year starting from 1 January: 186SL095630119 1) a Completeness Index (CI) based on the percentage of hours 186SL095630120 with available data, 186SL095630121 2) a list of gaps longer than a day, 186SL095630122 3) a summary of days with consecutive missing or obviously 186SL095630123 wrong data in a time span longer than 6 but less than 25 186SL095630124 hours that have been replaced, with hours in parentheses, and 186SL095630125 4) a summary of days with questionable fluctuations in the 186SL095630126 residual series. Fluctuations within the residuals are 186SL095630127 considered significant and are noted if they are greater than 186SL095630128 25 cm. This policy has changed slightly as of October 1992: 186SL095630129 only suspicious fluctuations due to obvious instrumentation 186SL095630130 problems are noted. Minor timing drifts are no longer 186SL095630131 included in the list of questionable days. 186SL095630132 186SL095630133 Note : If the predicted tides poorly model the observed heights 186SL095630134 due to the inability of the tidal analysis to completely resolv 186SL095630135 the non-linear shallow water effects, the residuals are not 186SL095630136 suitable for assessing the data quality. Instead, a subjective 186SL095630137 comment on the quality of the data is provided. 186SL095630138 186SL095630139 *The predicted tides are obtained with the use of a harmonic 186SL095630140 analysis program (Foreman, 1977) which is executed on a year 186SL095630141 of apparently good data for a given station. The Predicted 186SL095630142 Tide Method for filling gaps consists of statistically 186SL095630143 comparing the predicted tides to the observed data and 186SL095630144 shifting the predicted tides in time to correct for timing 186SL095630145 differences. Then the linear interpolation between hourly 186SL095630146 values at the end points of the gap in the residual series is 186SL095630147 added to the corresponding corrected predicted tide data to 186SL095630148 obtain interpolated values over the span of the gap. 186SL095630149 186SL095630150 Bloomfield, P., 1976. Fourier Analysis of Time Series: An 186SL095630151 Introduction. New York: John Wiley and Sons. pp 129-137. 186SL095630152 186SL095630153 Foreman, M., 1977. Manual For Tidal Height Analysis and 186SL095630154 Prediction. Institute of Ocean Sciences, Patricia Bay, 186SL095630155 Victoria B.C. Pacific Marine Science Report 77-10. 186SL095630156 186SL09566 19751 2489000 2484000 2534000 2512000 2569000 2533000 186SL09566 19752 2504000 2529000 2590000 2584000 2613000 2500000 186SL09566 19761 2485000 2512000 2469000 2548060 2582000 2573000 186SL09566 19762 2633000 2610050 2624000 2667040 2632000 2521000 186SL09566 19771 2435000 2413000 2409000 2487000 2547000 2563000 186SL09566 19772 2637030 2577000 2658000 2674000 2589000 2554000 186SL09566 19781 2384000 2343000 2428000 2434000 2503000 2515000 186SL09566 19782 2506000 2547000 2582000 2686000 2620000 2567000 186SL09566 19791 2393000 2441000 2477000 2488000 2569000 2602000 186SL09566 19792 2638000 2632000 2603000 2790000 2636000 2535000 186SL09566 19801 2437000 2425000 2456000 2487000 2580000 2554000 186SL09566 19802 2594000 2602000 2726000 2735000 2729000 2599000 186SL09566 19811 2564000 2514000 2489000 2565000 2529000 2638000 186SL09566 19812 2657000 2642000 2625000 2733000 2691000 2556000 186SL09566 19821 2505000 2436000 2456000 2522000 2555000 2593000 186SL09566 19822 2600000 2557000 2672000 2688000 2603000 2511000 186SL09566 19831 2451000 2418000 2453000 2493000 2545000 2601000 186SL09566 19832 2612000 2595000 2587000 2671000 2659000 2546000 186SL09566 19841 2425000 2396000 2441000 2507000 2556000 2594000 186SL09566 19842 2582000 2605000 2543000 2673000 2684000 2499000 186SL09566 19851 2344000 2453000 2428000 2434000 2514000 2627000 186SL09566 19852 2576000 2604000 2566000 2643000 2642000 2563000 186SL09566 19861 2484000 2412000 2476000 2486000 2493000 2557000 186SL09566 19862 2612000 2652000 2625000 2665000 2636000 2549000 186SL09566 19871 2507000 2482000 2485000 2496000 2545000 2569000 186SL09566 19872 2574000 2562000 2608000 2631000 2553000 2528000 186SL09566 19881 2482000 2443000 2433000 2480000 2541000 2579000 186SL09566 19882 2568000 2584000 2607000 2693000 2609000 2535000 186SL09566 19891 2473000 2449000 2483000 2481000 2548000 2585000 186SL09566 19892 2612000 2630000 2601000 2684000 2651000 2590000 186SL09566 19901 2542000 2444000 2472000 2539000 2526000 2610000 186SL09566 19902 2618000 2616000 2638000 2715000 2632000 2586010