QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 25 Apr 2002 Station : Nuku'alofa Latitude: 21 08.0S Country : Tonga Longitude: 175 10.0W JASL # : 038A Time Meridian: 195E (GMT + 13 hr) GLOSS # : none TOGA #: none NODC #: 52171501 Contributor : The National Tidal Facility (NTF) Flinders University of South Australia GPO Box 2100 Adelaide, 5001, South Australia AUSTRALIA For the 1990-1994 data: UH Sea Level Center 1000 Pope Rd. MSB 317 Honolulu, Hawaii 96822 Originator : The National Tidal Facility Flinders University of South Australia GPO Box 2100 Adelaide, 5001, South Australia AUSTRALIA For the 1990-1994 data: Ministry of Lands, Survey & Natural Resources P. O. Box 5 Nuku'alofa KINGDOM OF TONGA Original Data: analog (Ott); digital (SEAFRAME) Instrmnt Type: A.Ott float and well gauge (1990-1994) located at same latitude as above, but 175 12.0W; Aquatrak acoustic gauge (SEAFRAME) (1993-) Digitzd Intvl: hourly (Ott); 6 minute (SEAFRAME) Present Data : Hourly, daily, and monthly values obtained by: Hourly : spot hourly (Ott); filter (SEAFRAME) 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 : 20 Jun 1990 - 31 Dec 2001 Gaps > 1 mon : none Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : Yes Distribution : 1990-2001 Refernce Levl: The sea level heights are referred to the zero point assigned to the NTF tide gauge, which is linked to fixed points on land. Benchmark information is available upon request from the originators. The 1990-1994 Ott data were adjusted to the NTF series by adding -450 mm. Comment : The series is based on Ott data from 1990 to 21 Jan 1993. Gaps in the 1993-94 NTF were replaced by Ott data as noted by * below. The daily and monthly means agree well with an adjacent station, Suva, Fiji and reveal no apparent changes in the reference level except the following: the residuals show a sharp drop during the data gap of 3-5 January, 1993 and the mean level appears low during 1993 and 1994. However, the sharp drop in early January 1993 agrees with the signature at Noumea and Rarotonga and the low trend through 1994 agrees well with Noumea. No evidence was found in tide staff readings to suggest a shift. We assume the drop is real. SPECIAL NOTE FROM THE DATA ORIGINATORS (OTT GAUGE): Supply of sea level data subject to the following conditions: i) Data are available for scientific use only. Any other type of use, specifically commercial use, is forbidden. For a copy of the data, non-scientific (commercial) users must contact the originators directly: Tonga Defence Services Hydrographic Unit P.O. Box 72 Nuku'alofa TONGA ii) When any data supplied by the Tonga Defence Services Hydrographic Unit is used in any publication or report, the origin of such data shall be acknowledged in that publication or report in the following approved form:-- "Tidal {predictions) for {port} {are} supplied {constants} {station} {is} {material} {...} by the Tonga Defence Services Hydrographic Unit Copyright reserved." iii) All material is supplied in good faith and is believed to be correct. It is supplied on the condition that no warranty is given in relation thereto, that no responsibility or liability for errors or omissions is, or will be, accepted and that the recipient will hold the Tonga Defence Services Hydrographic Unit free from all such responsibility or liability and from all loss or damage incurred as a consequence of any error or omission. iv) The acceptance of material and computations from the Tonga Defence Services Hydrographic Unit will be deemed to include acceptance of the conditions of supply. SPECIAL NOTE FROM THE NTF: Supply of sea level data subject to the following conditions: i) When any data supplied by the National Tidal Facility is used in any publication or report, the origin of such data shall be acknowledged in that publication or report in the following approved form:-- "Tidal {predictions) for {port} {are} supplied {constants} {station} {is} {material} {...} by the National Tidal Facility, The Flinders University of South Australia, Copyright reserved." ii) All material is supplied in good faith and is believed to be correct. It is supplied on the condition that no warranty is given in relation thereto, that no responsibility or liability for errors or omissions is, or will be, accepted and that the recipient will hold the Flinders Univer- sity of South Australia and the National Tidal Facility free from all such responsibility or liability and from all loss or damage incurred as a consequence of any error or omission. iii) The acceptance of material and computations from the National Tidal Facility of the Flinders University of South Australia will be deemed to include acceptance of the conditions of supply. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1990 50 none none none 1991 97 293-304 none 306,308,335 1992 96 35-42,118-126 none none 1993 99 3-5 *(00)322-(00)326 none *(00)110-(00)113 1994 100 none none none 1995 96 325-342 *(00)259-(23)264 none 1996 100 none none none 1997 100 none none none 1998 100 none none none 1999 100 none none none 2000 100 none none none 2001 88 12-30,328-354 none none