QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL update: 28 Aug 2013 Station : Kerguelen Latitude: 49 20.7S Country : France Longitude: 070 13.2E JASL # : 180A Time Meridian: 075E (GMT + 5 hr) GLOSS # : 023 TOGA #: none NODC #: 34079001 Contributor : Service d'Observation ROSAME, LEGOS/OMP 14 Ave. Edouard Belin 31400 Toulouse FRANCE Originator : same Original Data: digital Instrmnt Type: Aanderaa WLR7 tide recorder. The gauge is installed along the wharf of Port-aux-France. This bottom pressure sensor is at the base of a stilling well which is used to filter waves. The recorder is triggered by a central unit where the barometric pressure is measured at the same time. Digitzd Intvl: hourly Present Data : Hourly, daily, and monthly values obtained by: Hourly : Four minute integration time centered on the hour is used for the bottom pressure measurement. Data are transmitted via ARGOSS to Toulouse. The data are then processed to decrypt the messages and compute sea level based on i) relative bottom pressure, ii) water temperature, and iii) barometric pressure. From this set of data in combination with salinity, which is periodically measured but is assumed to be constant over extended periods, one computes water density based on the UNESCO formula for the sea-water equation; thus, the sea level is deduced. THIS DATA SET IS THE DIRECT MEASURE OF SEA LEVEL, assuming the water density has been properly estimated. The data set DOES include variations caused by atmospheric pressure changes on sea level; i.e., it DOES include the inverse barometer effects in the signal. 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 : 05 Apr 1993 - 31 Dec 2012 Gaps > 1 mon : none Time Refernce: GMT (00-23 hours) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : Yes Distribution : 1993-2012 Refernce Levl: Presently no link is established between the tide gauge and fixed bench marks. Please refer to the originator for the up-to-date status. A GPS "pilar" has been established, but presently has not been linked to the tide station. A DORIS station for satellite tracking is established at Kerguelen. Comment : Pressure transducers typically have long-term tendencies to drift. However, the originators have calibrated the instrument before deployment and due to the shallow resting level of the pressure sensor, the potential drift would be very small. Post-retrieval calibrations have not been performed. Please refer to the originators for the up-to-date status. For this data set, no explicit correction has been applied in this regards. The plot of the hourly data minus the predicted tides reveals some period fluctuations around the frequencies of the tides. This is most likely due to the inability of the tidal analysis to resolve all the components of the tide. These plots also reveal strong weather influences which dominates the short-term variability (beyond the tides). In May 2011, data for the period 05 Apr 1993 - 01 Mar 1998 were replaced with corrections as provided by the originators. An adjustment of +181 mm was made for 01 Jan 2011- 31 Dec 2012 based on information provided by the originators. This adjustment may be temporary as the originators investigate the level change. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1993 74 none none none 1994 99 221-222 none none 1995 99 327-328 none none 1996 100 none (10)209-(17)209 none (00)306-(17)306 (08)319-(17)319 1997 100 none none none 1998 99 34-35 (00)099-(18)099 none (01)348-(10)348 1999 99 356-358,362-364 (01)362-(10)362 none 2000 96 14-29 (16)004-(07)005 none 2001 94 204-225 (05)014-(13)014 none 2002 100 none (10)014-(17)014 none 2003 100 none none none 2004 100 none none none 2005 100 none (14)322-(00)323 none 2006 96 48-62 (18)120-(02)121 none 2007 100 none (17)171-(02)172 none 2008 100 none (16)193-(00)194 none (16)222-(01)223 2009 99 230-233 (02)168-(11)168 none (18)168-(10)169 (18)211-(04)212 (05)229-(12)229 (04)285-(11)285 2010 98 14-15,33-34,79-80, (20)119-(05)120 none 152-155,178-180,365 (02)150-(16)150 (15)170-(02)171 (07)171-(00)172 (09)183-(00)184 (19)206-(07)207 (10)207-(20)207 (20)211-(04)212 (13)245-(01)246 (19)246-(03)247 (14)327-(02)328 (19)362-(05)363 (00)365-(08)365 2011 99 4-5,254-256,270-271 (06)101-(19)101 none (02)131-(13)131 (15)192-(04)193 (05)234-(19)234 (04)235-(20)235 (05)248-(17)248 (17)266-(05)267 2012 100 none (14)146-(03)147 none (13)186-(02)187