4.4.1 TAC and δ-HAT results

We now move from basin-wide surveys to a more tightly focused regional analysis of the Hong Kong waters, where 12 closely spaced tide gauges are available. For gauge names and locations, the reader is directed to refer to Figure 6.

#### Figure 17.

Tidal anomaly correlations (TACs) of detrended K1 amplitude to detrended MSL in Hong Kong [11], with the marker size showing the relative magnitude according to the legend, in units of mm m<sup>1</sup> . Markers are as in Figure 16. Maps were generated using MATLAB version R2011a (www.mathworks.com).

#### Figure 18.

δ-HAT map in Hong Kong [11], with the marker size showing the relative magnitude according to the legend, in units of mm m<sup>1</sup> . Markers are as in Figure 16. Maps were generated using MATLAB version R2011a (www.mathworks.com).

The strongest positive M2 TACs are seen at Quarry Bay (+218 mm m<sup>1</sup> ), and at Tai Po Kau (+267 mm m<sup>1</sup> ), with a smaller positive TAC seen at Shek Pik (Figure 16). In the waters west of Victoria Harbor, all gauges except Kwai Chung exhibit moderate negative TACs. The diurnal TACs in Hong Kong generally exhibit a largermagnitude and more spatially coherent response than semidiurnal TACs. Like M2, the strongest K1 values in Hong Kong (Figure 17) are seen at Quarry Bay (+220 mm m<sup>1</sup> ) and Tai Po Kau (+190 mm m<sup>1</sup> ).

The TACs are widely observed in Hong Kong, but the δ-HATs are only of significance at a few locations (Figure 18). Five stations exhibit significant δ-HAT values, with Quarry Bay and Tai Po Kau having very large positive magnitudes (+665 mm m<sup>1</sup> and +612 mm m<sup>1</sup> , respectively), and Shek Pik having a lesser magnitude of +138 mm m<sup>1</sup> . Conversely, Ma Wan and Chi Ma Wan exhibit moderate negative <sup>δ</sup>-HAT values (approx. 100 mm m<sup>1</sup> ). The remainder of gauges (which are mainly open-water locations) have statistically insignificant results for the combined tidal amplitudes, even where some large individual TACs were observed. This shows that the combined tidal amplitude effect as expressed by the δ-HATs is most important in semi-enclosed harbors.
