MESOSCALE NOCTURNAL JETLIKE WINDS WITHIN THE PLANETARY BOUNDARY-LAYER OVER A FLAT, OPEN COAST

Mesoscale nocturnal jetlike winds have been observed over a flat, open coast. They occur within the planetary boundary layer between 100 and 600 m. At times the wind shear may reach 15 m s-1 per 100 m. Unlike the common low-level jet that occurs most often at the top of the nocturnal inversion and only with a wind from the southerly quadrant, this second kind of jet exists between nocturnal ground-based inversion layers formed by the 'cool pool', or mesohigh, and the elevated mesoscale inversion layer over the coast. It occurs mostly when light {Mathematical expression} geostrophic winds blow from land to sea and when the air temperature over adjacent seas is more than 5 °C warmer than that over the coast. This phenomenon may be explained by combined Venturi and gravity-wind effects existing in a region from just above the area a few kilometres offshore to 100-600 m in height approximately 40-50 km inland because this region is 'sandwiched' between the aforementioned two inversion layers. © 1979 D. Reidel Publishing Co.