QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL Station : Praia-A,Cape Verde Latitude: 14 55.0N Country : Portugal Longitude: 023 30.0W JASL # : 222A Time Meridian: 015W (GMT - 1) GLOSS # : none TOGA #: none NODC #: 71024301 Contributor : ORSTOM LOP Museum 43-45 rue Cuvier 75231 Paris Cedex 05 FRANCE Originator : same Original Data: digital Instrmnt Type: Aanderaa WLR5 (bottom-mounted pressure gauge) 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 : 02 Mar 1984 - 11 Oct 1985 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 : 1984-1985 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 meters. Techniques of data processing by the originator are discussed in the second reference below. The Praia pressure gauge records consist of two separate segments: Praia-A: 02 Mar 1984 - 11 Oct 1985 Praia-B: 11 Oct 1985 - 16 Feb 1989 The series was broken into segments because the site was moved by less than 1 mile on 11 Oct 1985. Eight hours of overlap were available between Praia-A and Praia-B, with a mean difference of 2.35 meters in the original data (for processing at the TOGA Sea Level Center, 1 meter was subtracted from the original data of Praia-B). 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 Praia-A 1984/03/02/18 - 1984/12/17/11 Praia-A 1984/12/17/12 - 1985/10/11/19 Praia-B 1985/10/11/12 - 1986/06/02/16 Praia-B 1986/12/18/16 - 1988/05/10/16 Praia-B 1988/11/15/18 - 1989/02/16/21 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. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1984 83 none none none 1985 78 none none none