QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 02 Jan 2008 Station : Cox's Bazaar Latitude: 21 27.0N Country : Bangladesh Longitude: 091 50.0E JASL # : 136A Time Meridian: 090E (GMT + 6 hr) GLOSS # : none TOGA #: none NODC #: 12091101 Contributor : Bangladesh Inland Water Transport Authority (BIWTA) Dept. of Hydrography 141-143, Motijheel C/A Dhaka - 1000 BANGLADESH Originator : same Original Data: analog Instrmnt Type: float and well type gauge (Munro) Digitzd Intvl: hourly Present Data : Hourly, daily, and monthly values obtained by: Hourly : original data are hourly 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 : 01 Jan 1977 - 31 Dec 2006 Gaps > 1 mon : 22 Nov 1979 - 31 Dec 1979;31 Dec 2000 - 31 Dec 2003 Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : No Distribution : 1983-2006 Refernce Levl: The sea level heights are referred to the zero point assigned to the tide staff. Bench mark information is available upon request from BIWTA. Level shifts were identified in the series and adjusted as follows for a short time segment: value added period (hour)day/month/year to original(mm) ----------------------------- --------------- (18)22/10/1984-(16)31/12/1984 -250 This adjustment is uncertain to a few cm. Comment : The hourly residuals suggest a level shift on 24 Sep 1979 of about +20 cm. The daily difference plot with Hiron Point also shows this suspicious feature. Other level jumps appear on 22 July 1980 (about -40 cm), 1 Dec 1980 (about +20 cm), and 2 Oct 1982 (-20 cm). These features are under investigation by the originators. The following periods contain a substantial amount of interpol- ation of 2-5 hour gaps occurring in succession (day/month/year): 04/06/1980-27/06/1980; 01/12/1981-10/07/1983; 19/09/1985-24/09/1985; 10/03/1986-06/04/1986; 01/05/1987-31/12/2000, 01/01/2004-12/31/2006. The interpolated short gaps do not appear to contaminate the low-frequency information. The reference level appears about 20 cm low from Jan - Apr 1994 with stong 3-day peaks at the end of Mar and beginning of May. The hourly residuals contain large periodic fluctuations. It is not clear whether this is due to phase shifts in the timing of the gauge or due to the inability of the tidal analysis to completely resolve all the tidal constituents at this shallow water site. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1977 98 55-63 none see comment above 1978 98 175-181 none see comment above 1979 89 326-365 none see comment above 1980 100 none none see comment above 1981 100 none none see comment above 1982 100 none none see comment above 1983 100 none (18)364-(17)365 see comment above 1984 100 none none see comment above 1985 100 none none see comment above 1986 87 29-34,58-62,85-90, none see comment above 120-125,148-153,176- 181,211-216,239-244, 302-307,330-335 1987 100 none none see comment above 1988 100 none none see comment above 1989 98 133-141 none see comment above 1990 96 98-112 none see comment above 1991 100 none none see comment above 1992 100 none see comment see comment above 1993 100 none see comment see comment above 1994 100 none see comment see comment above 1995 100 none see comment see comment above 1996 100 none see comment see comment above 1997 100 none see comment see comment above 1998 100 none see comment see comment above 1999 100 none see comment see comment above 2000 99 366 see comment see comment above 2001 0 1-365 see comment see comment above 2002 0 1-365 see comment see comment above 2003 0 1-365 see comment see comment above 2004 100 none see comment see comment above 2005 100 none see comment see comment above 2006 99 365 see comment see comment above