QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 20 Mar 2000 Station : Fernando de Noronha-C Latitude: 03 49.7S Country : Brazil Longitude: 032 24.2W JASL # : 203C Time Meridian: 030W (GMT - 2 hr) GLOSS # : 198 TOGA #: A021 NODC #: 50033201 Contributor : LPAO/INPE Oceanografia Av. Dos Astronautas 1758 Sao Jose Dos Campos BRAZIL Originator : ORSTOM LOP Museum 43-45 rue Cuvier 75231 Paris Cedex 05 FRANCE Original Data: digital Instrmnt Type: Aanderaa WLR5 (bottom-mounted pressure gauge) Serial number 643/05-- It was a separate instrument which was deployed 13 Nov 1985 - 31 Dec 1986. It was placed in the same cement hole as 203A (1982-1983). The instrument was recovered by Dr. Marcio Vianna of LPAO. Digitzd Intvl: one hour Present Data : Hourly, daily, and monthly values obtained by: Hourly : direct digitization, no filter 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 : 13 Nov 1985 - 31 Dec 1986 Gaps > 1 mon : none Time Refernce: GMT (00-23 hours) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : No Operational : No Sat. Trans. : No Distribution : 1985-1986 Refernce Levl: Due to the nature of the bottom-mounted pressure gauges, no link could be established between the zero of the gauge values and fixed points on land. Also, tide staff observations or the like were unavailable. This series has no long-term reference level. Comment : Although this data set is within the sea level archive, the user must acknowledge that these data represent inferred sea level from a sub- surface pressure gauge, which measures the combined weight of the column of water and air above it. A constant atmospheric pressure has been subtracted, but variations in atmospheric pressure, which would not be sensed by a conventional float/ well gauge, would affect the measurement of the sub-surface pressure gauge. The depth of the instrument in the water was about 7.9 m. Techniques of data processing by the originator are discussed in the second reference below. The original gauge was destroyed in June 1983 and a new gauge was installed in 1984 about a mile away. The original series is called Fernando de Noronha-A (203A) and the second as Fern.-B (203B). Due to the tendency for pressure gauge sensors to drift, it is beneficial for investigators to know the time span of each instrument deployment (time/date as yyyy/mm/dd/hh(GMT)): Series start stop 203A 1982/11/07/19 - 1983/06/28/12 203B 1984/04/17/15 - 1985/11/13/12 203C 1985/11/13/13 - 1986/12/31/23 For more information: Verstraete, J.M., 1988. Sea level variations in the tropical Atlantic. Time series of ocean measurements, Technical series, UNESCO,4,33-47. Verstraete, J.M., 1992. Accuracy of shallow pressure gauges. Joint IAPSO-IOC Workshop on Sea Level Measurements and Quality Control, Paris, 12-13 October, 1992. IOC Workshop Report No. 81, UNESCO. pp. 70-76. The hourly data from 1985/11/13/13-1986/12/31/23 were tied to the previous data based on an overlap from 1984/04/17-1985/11/13. A constant offset of 5000 mm was added to the 1985/11/13-end data to link it to the original series. The data are of good quality. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1985 13 none none none 1986 100 none none none