Warm Cool Return flow Land breeze Warm Cool Return flow Sea breeze Figure 4-14.  Land-sea breezes. Local and Small-Scale Winds  Gradient Winds Orographic Winds Anabatic Winds  The term “orographic” has multiple meanings, when placed  in the context of weather phenomena. In a general sense,  according to the American Meteorological Society, wind  flows that are caused, affected, or influenced by mountains  may be said to be orographic winds flows. The term has  come to mean any winds that are affected by terrain, not just  mountains; this definition is probably the most frequently  used, when discussing balloon flight. Pressure gradients initiate the movement of air and as soon  as the air acquires velocity, the Coriolis force deflects it to  the right in the Northern Hemisphere. As the speed of the air  along the isobars increases, the Coriolis force becomes equal  and opposite to the pressure gradient force. After a period of  time, the air moves directly parallel to the curved isobars if  there is no frictional drag with the surface. The air no longer  moves toward lower pressure because the pressure gradient  force is completely neutralized by the Coriolis force and the  centrifugal force. As a specific term, “orographic lifting” is defined as an  ascending air flow caused by mountains. The mechanisms  that produce the orographic lifting fall into two broad  categories: This definition, while strictly referring only to lifting by  mountains, is sometimes extended to include the effects  of hills or long sloping terrain. When sufficient moisture  is present in the rising air, Orographic fog or clouds may  form.  Anabatic winds are those that blow up a steep slope or  mountain side. It is sometimes referred to as an upslope flow.  These winds typically occur during the daytime in calm,  1.  The upward deflection of horizontal large-scale air  flow by the terrain acting as an obstacle or barrier,  or 2.  The daytime heating of mountain surfaces to produce  an anabatic flow (see below) along the slopes and  updrafts in the vicinity of mountain peaks.  4-14