Sea breezes in South Australia
|
E. Linacre and B. Geerts |
1/'99 |
The inland penetration and strength of the sea breezes along the southern coasts of Australia from Perth to eastern Victoria is notorious (Section 14.2). For instance on the east-west coast of South Australia, from Port Gambier to Adelaide, they can reach 11 m/s, and remain that strong through to the early evening (1). They are enhanced when the gradient wind is weak or aligned with the coast (i.e. the isobars lie northwest-to-southeast). A southeasterly gradient wind prevails there in summer, between the high over the Great Australian Bight and an inland trough. Such wind induces coastal upwelling, which tends to stabilise the coastal SST at 17ºC throughout summer. This allows considerable difference between land and sea temperatures, e.g. 35ºC and 17ºC, respectively, on summer afternoons. This temperature difference drives the sea breeze, which attempts to destroy the temperature difference.
The sea breeze does not always penetrate inland in Adelaide. On days with north(west)erly flow, in advance of a cold front, Adelaide may reach 40ºC. When a sea breeze does occur, the maximum is 22-26ºC. As a result, the Adelaide maxima assume a bimodal distribution in summer: either agreeable or hot days occur, but the 'in-between' days are rare.
The leading edge of the sea breeze is often well-defined as the circulation is strong and the land near the mouth of the Murray River flat. The sea breeze front has the typical characteristics of a density current (Note 14.D), which sometimes runs away and cuts off from the marine flow and dissipates, before being consumed in a new front (2).
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