![]() ![]() The land breeze continues until midmorning, when the sea-breeze cycle starts over again. A weak land-breeze convergence line and associated line of cumulus clouds develop offshore near sunrise. ![]() After land again becomes cooler than the water, a land breeze becomes well developed by 0300 LST and reaches its maximum intensity near 0600 LST. At this time, a temperature inversion and occasionally fog appear over land. By midnight or 0000 LST, the sea breeze is barely evident aloft, and the surface wind is nearly calm over land. At 18 LST, the sea breeze is still clearly present but is gradually weakening in intensity. Because of a low-level velocity divergence, there is a pronounced subsidence and thus a clear sky near the coastal area at this time. At 1500 LST, the sea breeze is fully developed, and rain showers may be observed at the convergence zone, 30 to 40 km inland. At this time, a line of small cumulus may mark the sea-breeze front. By 1200 LST, the land has become warmer than the water, and the circulation has reversed. At 0900 LST ( local standard time), the air temperature over land is still cooler than over the sea and the land breeze is still blowing. The dashed horizontal line represents the 900-mb pressure surface (approximately the convective condensation level). The elliptical shapes in the figure illustrate the horizontal and vertical extent of the land–sea breeze circulation. The maximum wind speed and its approximate height in each current are depicted by arrows. The lower portion of the onshore flow is the sea breeze and that of the offshore flow is the land breeze. The onshore and offshore wind components are shown at 3-hr time intervals during the day. An example of the land- and sea-breeze system is shown in Fig. At specific locations, large and abrupt temperature and relative humidity changes can occur with the passage of the sea-breeze front. Typical horizontal speeds of the sea breeze are of the order of meters per second, while the vertical components are only a few centimeters per second. In contrast, the nocturnal land breeze is usually rather shallow, being only a few hundred meters deep. In the vertical, the sea breeze reaches altitudes of 1300–1400 m in tropical coastal areas, with a maximum speed at a few hundred meters above the ground. The sea breeze may extend up to 50 or 100 km inland, but the seaward range of the land breeze is much smaller. ![]() Later, a seaward-blowing land breeze appears and continues until after sunrise. A sea breeze develops a few hours after sunrise, continues during the daylight hours, and dies down after sunset. ![]()
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