curves, such as Southern California; or where there are inland marine regions, such as Puget Sound, San Francisco Bay, and southeast Alaska.

In the coastal zone it is not necessary to have an upstream velocity directed toward the mountains for the orography to influence coastal winds. If a localized region of high or low pressure is generated in the coastal zone, it will, under certain conditions, be trapped and propagate along the coastline within the coastal zone. This is a common phenomenon, for example, along the coasts of California and Australia.

The Froude number considers the relative importance of vertical displacement of isentropic surfaces in flow around and over obstacles. A second factor is the influence of the earth's rotation on upstream flow deceleration (Queney, 1948). One can consider the influence of rotation through a Rossby number:

where U is the upstream velocity, f the Coriolis force, and l_m is the half-width of the ridge; little flow deceleration is found when R_m is less than unity. Numerical simulations by Pierrehumbert and Wyman (1985) and trajectory analyses by Chen and Smith (1987) suggest that in the region of steep topography the deceleration zone will grow upstream to a width of:

This parameter l_R is known as the radius of deformation. Steep topography is defined by the nondimensional slope, (h_m/l_m)(N/f), being greater than 1. For the coastal case, l_R is often on the order of 50 to 150 km and l_R >> l_m; this contrasts with broad mountain ranges such as the Rockies with l_m on the order of 500 km. In the broad mountain case, l_m >> l_R, the flow stays quasi-geostrophic with R_m < 1 (i.e., wind blows perpendicular to the pressure gradient as it flows over the topography, with little upstream influence). The coastal region, however, is often in the knife-edge mountain case, l_R >> l_m, where R_m >> 1. Here one expects the coastal mountains to represent a wall, and the momentum balance in the along-shore direction near the wall is not expected to be geostrophic. The smoothed topographies in current-generation numerical weather prediction (NWP) models do not even qualitatively represent knife-edge slopes and thus do not correctly include coastal phenomena.

To further delineate the influence of orography on coastal meteorology, let L be the scale for motion in the along-coast (y) direction, and l be the scale in the cross-shore direction (-x), where

We can nondimensionalize the equations of motion in the following manner. The cross-shore wind component, u, and along-shore wind component, v, are scaled by UL/l, time by l/U, vertical distances by D = fl/N , and

Front Matter (R1-R12)

Executive Summary (1-4)

1. Introduction (5-8)

2. Boundary Layer Processes (9-18)

3. Thermally Driven Effects (19-30)

4. The Influence of Orography (31-44)

5. Interactions With Larger-Scale Weather Systems (45-50)

6. The Influence of the Atmospheric Boundary Layer on the Coastal Ocean (51-62)

7. Air Quality (63-70)

8. Capabilities and Opportunities (71-80)

9. Educational and Human Resources (81-84)

References (85-100)