Time series analysis of 25 hour records of water elevation in Pattani Bay

Time series analysis of 25 hour records of water elevation in Pattani Bay
การวิเคราะห์อนุกรมเวลา การเปลี่ยนแปลงระดับน้ำในอ่าวปัตตานี ในรอบ 25 ชั่วโมง

Boonsanong Khumpai, Demonstration School, F. of Education, PSU.
Don McNeil, Prof., D. of Statistics, Macquarie U., Sydney, NSW, Australia
Naiyana Srichai, D. of Sci., F. of Sci. and Tech., PSU.

Published : Songklanakarin J Sci Technol 2000, 22(2) : 215-227
Key words : Pattani Bay, tides, surface current, time series

Water levels (at 5-minute intervals) and surface current velocities (at 15-minute intervals) were measured at five locations around the shore of Pattani Bay over two periods, each of 25 hours dura- tion, and one week apart in mid-1996. Ribbon plots are used to show how the direction and speed of the surface current change with time at each location. Univariate time series analysis, based on fitting signals containing a small number of low-frequency sinusoidal components and modelling the resi- dual noise as simple autoregressive processes, accounts for close to 100% of the variation. Bivariate time series analysis, based on cross-correlations between series at different lags, is used to estimate the times taken by tidal water to elevate at different locations. As a result, a simple model showing time lag of water elevation at selected locations in Pattani Bay under the influence of the tidal ebb and flood was developed.

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