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(Si฀ tfr฀Temperatur e฀ Sea surface temperatures generally follow those of the air, wit h a sligh t tim e la g i n summer , s o tha t th e mea n minimum temperatur e o f 16.6° C i s recorded i n Februar y and th e mea n maximu m o f 28.8° C i n September . Se a surface temperature is not wholly dictated by the prevailing air temperature because of the interplay of water currents. The northeas t monsoo n pushe s dow n col d Eas t Chin a Coast Water s (th e Taiwa n Current ) i n winte r whil e th e southeast monsoo n pushe s u p war m Sout h Chin a Se a Water (th e Haina n Current ) fro m th e Gulf of Hainan i n summer. Similarly, a finger of the warm Kuroshio Curren t may ente r th e Sout h Chin a Se a vi a th e Luzo n Strait s i n winter, pushin g westward s toward s Hon g Kon g an d imparting a slight warmin g effec t upo n th e water s of th e southern coas t of China . ^ Salinit y mmammmmmmmmmmmmmmm The wester n water s o f Hon g Kon g ar e influence d dramatically by the outflow of low salinity, sediment-laden, freshwater from the Pearl River, especially in summer when heavy rainfall causes the river to flood. The eastern oceanic waters o f Hong Kong , o n th e othe r hand , ar e no t unde r the influenc e o f th e Pear l River , s o tha t salinitie s ar e relatively stable, at ~35%o year round, and reflect the larger picture o f th e Sout h Chin a Sea . Thes e water s ar e rela tively well-oxygenated an d transparent, for the same oceanic reasons. Hong Kong's eastern waters are our cleanes t and i t i s n o coincidenc e tha t man y loca l recreationa l beaches ar e locate d i n thes e areas . These water s ar e als o home to Hong Kong's reef-building corals , which flouris h in the protection o f bays. The water s of Hong Kong can be divided int o thre e zones, as described by Morton (1982) (Figure 3B) who also gives an overview of the hydrography of Hong Kong waters. To the west is an estuarine zone under the influence o f the Pearl River, and to the east a fully oceani c zone. Betwee n the two , ther e i s a transitio n zon e whic h represent s a n area o f variabl e hydrography . Th e water s o f thi s centra l zone are also heavily polluted by the sewage and industria l discharges fro m th e citie s o f Kowloo n an d Victoria , encompassing Victori a Harbour , an d Shati n an d Ta i P o on th e shore s of Tolo Harbour . Waves฀ The easter n water s o f Hon g Kon g are , a s w e hav e seen, exposed to the prevailing northeasterly, easterly and southeasterly wind s (Plat e 5) . Seasonal change s i n win d speed an d directio n impar t a powerfu l effec t upo n th e t฀ Plate 5. Waves smash through the gap into Lobster Bay (Photo: E. Stokes). eastern shore s o f Hong Kon g tha t i s manifested i n the m being subjecte d t o th e equall y dynami c effect s o f waves . As a wave approache s a shore an d becaus e o f its circula r motion, i t will 'touch' the sea bed. This is when th e wav e appears t o 'break' . Th e breakin g wav e crashe s ont o th e shore as the swash, the receding wave being the backwash. A wav e carrie s immens e powe r i n it s swash , exertin g a force upon any line of weakness in the rock upon which i t breaks, o f u p t o abou t 14 0 kg-cm' 2 . Suc h wave s are , therefore, destructive. This force is, however, compounde d by the fact tha...

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