QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 14 Jul 1999 Station : Easter-E Latitude: 27 09.0S Country : Chile Longitude: 109 26.9W JASL # : 022E Time Meridian: 105W (GMT - 7 hr) GLOSS # : 137 Originator #:0305 NODC #: 52107901 Contributor : Servicio Hidrografico y Oceanografico de la Armada (SHOA) Valparaiso CHILE and for 1994-1996 data also from National Ocean Service (NOS) National Ocean. and Atmos. Administration (NOAA) N/OES22 SSMC4, STATION 7109 1305 East West Highway Silver Spring, MD. 20910-3233 Originator : same Original Data: analog (BUB); digital (PRS and BWL) Instrmnt Type: 1) Bristol bubbler gauge (BUB) (primary gauge 1985-01/1994,07/01/97+) 2) NOAA "digibub" water level gauge (PRS) (primary gauge 03/1994 - 06/30/97) this gauge uses a nitrogen-driven bubbler oriface below the water line connected to a Para- scientific pressure transducer located at the DCP housing. The pressure transducers are vented to the atmosphere so no atmospheric corrections are required. 3) NOAA backup pressure water level gauge (BWL) Digitzd Intvl: one hour (BUB); 6 min (PRS); 30 min (BWL) Present Data : Hourly, daily, and monthly values obtained by: Hourly : The original digitizing interval was hourly (BUB); 3-point Hanning filter centered on the hour (PRS) Daily : 119-point convolution filter (Bloomfield, 1976) centered on noon applied to the hourly data with respective periods of the 95, 50, and 5% amplitude points at 124.0, 60.2, and 40.2 hours Monthly: Simple average of all daily values; calculated if 7 or fewer days are missing Span of data : 01 Jan 1985 - 31 Dec 1998 Gaps > 1 mon : 05 Feb 1989 - 08 Mar 1989;18 Feb - 27 Jul 1991 Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : Yes Distribution : 1985-1998 Refernce Levl: The data have been linked to tide staff zero which is leveled to fixed bench marks. These bench marks are not linked to the bench marks used by other data sets for Easter Island; thus, this data record is independent. A reference level shift has been identified in the analog rolls by the originators and an adjustment was applied: value added period( (hh)day/month/year) to original(mm) --------------------------- --------------- (06)01/11/1988-(00)06/02/89 +100 The period after the long gap in 1991 appears to have a lower mean level although data received via satellite also show this feature. It is not clear if a reference shift occurred during the gap. Comment : Some questionable fluctuations of nearly a one-day duration during the winter months are related to weather events. The daily and monthly means reveal no apparent changes in the reference level. However, in comparison with the satellite- received data at the University of Hawaii, the difference plot of daily means shows a possible shift around 27 Aug 1986 (+7 cm). This difference plot also shows some other subtle shifts. The originators have checked the tide staff observation sheets and the analog rolls and found no problems. The gaps filled below (*) used redundant satellite- received data that were decimated to hourly with a spot sample technique. $ below denotes that the PRS series was filled with BUB data. # denotes gaps filled with satellite-received BUB data. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1985 98 1,127-128, (18)091-(06)092 132-133,154-155, 249-250 (21)112-(13)113 176-181 (16)131-(00)132 (12)347-(19)347 (14)361-(00)362 1986 100 none none 63-64,66,93-95 1987 100 none (23)335-(16)336 24-27,96-98,163, (20)342-(19)343 255,276 *(16)121-(21)123 *(17)365-(22)001 1988 100 none (06)182-(23)182 21-22,42,45-47, (23)271-(16)272 73-77,111,129-130, (10)289-(19)289 135 (08)305-(15)305 *(09)068-(18)069 *(00)093-(15)094 *(16)153-(23)155 *(20)253-(23)255 *(06)301-(14)302 1989 92 36-67 (07)067-(02)068 324-325 (12)121-(23)121 (11)274-(05)275 (14)318-(19)318 1990 98 58-66 (05)010-(17)010 none (17)357-(13)358 (05)360-(16)360 *(01)125-(15)134 *(02)361-(17)362 *(03)363-(23)365 1991 57 49-208 (18)030-(13)031 243 (07)034-(14)034 (03)040-(14)040 (01)043-(16)043 (00)227-(13)227 (17)243-(23)243 (01)244-(15)244 (20)259-(16)260 1992 100 none none none 1993 100 none (18)252-(04)253 256-257,261-265 (16)349-(15)350 *(07)017-(07)020 *(15)031-(21)035 *(20)047-(12)049 *(22)074-(16)076 *(16)103-(15)105 1994 100 none $(18)032-(21)059 33-37,92-93 $(20)091-(08)094 1995 100 none none none 1996 100 none none none 1997 100 none #(12)212-(23)227 none #(00)260-(23)262 1998 99 60-62 (07)032-(17)032 none (07)091-(15)091 #(18)306-(00)308 #(01)333-(05)335 (21)338-(15)339