QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 25 Oct 2011 Station : Karachi-A Latitude: 24 48.0N Country : Pakistan Longitude: 066 58.0E JASL # : 147A Time Meridian: 075E (GMT + 5.0 hr) GLOSS # : 030 TOGA #: I018 NODC #: 12064601 Contributor : for the 1985-1987 data: Pakistan National Institute of Oceanography 37 K. Block 6 P.E.C.H.S. Karachi, 29 PAKISTAN for the 1988-1992 data: National Hydrographic Data Bank 11, Liaquat Barracks Shahra -i-Faisal Karachi, PAKISTAN Originator : same Original Data: analog Instrmnt Type: Float type S.No. 23 Digitzd Intvl: spot hourly or half-hourly Present Data : Hourly, daily, and monthly values obtained by: Hourly : spot on hour 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 1985 - 30 Jun 1994 Gaps > 1 mon : 02 Sep 1985 - 01 Oct 1985;01 Nov 1985 - 04 Dec 1985 14 Mar 1989 - 16 Jul 1989;31 Oct 1990 - 30 Nov 1990 30 Jun 1992 - 01 Aug 1992;01 May 1993 - 01 Feb 1994 Time Refernce: GMT (hours 00-23) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : No Distribution : 1985-1994 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 the contributors. Bench mark associated with Tidal data is BM `A', established in 1880. It is located about 110 yards SW of Tidal Observatory a Manra. Chart Datum is associated with same BM. Datum is 14.14 feet ~ 4.309 m below the BM. Karachi-A appears about 20cm low relative to Karachi-B. It is intended to try to link the two time segments to the same datum. Comment : The daily and monthly means do not show any signs of reference level shifts or trends. Significant timing errors occur 01-15 Nov 1985 and 01 Jul - 31 Dec 1987. These errors were not correctable because the shifts in the timing were not integer increments of an hour. Random spikes were corrected, yet spikes with a periodic occurrence were left intact. The residuals show some time segments with large periodic fluctuations. It is not clear whether timing errors existed or if the tidal analysis was not able to resolve all the harmonics components. Only extreme fluctuations are noted below. The missing data for 1989-1990 will likely become available. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1985 82 244-274,305-338 (03)042-(21)042 95-98,109-116,124- (04)128-(19)128 127 (07)230-(23)230 1986 95 244-263 (01)070-(23)070 24-31,41-46,68-75, 87-89,144-146,195- 196,220-224,235-237, 305-319 1987 95 244-263 (01)118-(17)118 182-365 1988 100 none (02)107-(17)107 137-138,149-154,252- 259,267-269 1989 62 73-197,212-228 (23)048-(21)049 197-212,349-350 (21)231-(12)232 (09)269-(20)269 (07)289-(16)289 (19)310-(18)311 (22)326-(07)327 1990 92 304-334 none 1,29-31,46,67-87, 104-106,112-116,157- 163,190-209,216-217, 268,354-358 1991 100 none (07)134-(23)134 62-64,103-108,164- (02)181-(21)181 167,211-212,238-243, 267-271 1992 91 182-214 (11)065-(18)065 227,242-244,298-299 1993 33 120-365 none 32-42,53-74,84-86, 91-96,109-120 1994 41 1-32 none 41-46,56-62,67-77, 82-90,100-105,115, 128-166