Nuku'alofa (Tonga) Site History

History Summary

Station Name Nuku'alofa
Country Tonga
Latitude 21° 08.0' S
Longitude 175° 10.0' W
WOCE No. 9051
Time Reference GMT (hours 00-23)
Contributor The National Tidal Facility (NTF),
Flinders University of South Australia
GPO Box 2100,
Adelaide, 5001, South Australia
Instrument Type (1990-1994)A.Ott float and well gauge located at same latitude as above, but 175° 12.0' W;
(1993-)Aquatrak acoustic gauge (SEAFRAME)
Site of Gauge  
Observational Period 1990 - 2001

Reference Level

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.

Quality Assessment by the UH Sea Level Center


The series is based on Ott data from 1990 to 21 January 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.

Year CI(%) Missing Data Replaced Gaps or Bad Data Questionable 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 *(00)110-(00)113 none
1994 100 none none none
1995 96 325-342 *(00)259-(23)264 none
1996 100 none none none
1997 99 09 none none
1998 100 none 359(21)-360(05) none
1999 100 none none none
2000 100 none none none
2001 88 12-30,328-354 none 316-321