Forces that Influence Winds Pressure Gradient Force: difference in pressure over distance Directed perpendicular to isobars from high to low. Large change in pressure over s short distance is a strong pressure gradient and vice versa. The force that causes the wind to blow.
Forces that Influence Winds Coriolis Force Apparent deflection due to rotation of the Earth (the rotation rate of Venus is so slow that the Coriolis force is extremely small on Venus) Right in northern hemisphere and left in southern hemisphere Stronger wind = greater deflection No Coriolis effect at the equator greatest at poles. Only influence direction, not speed Only has significant impact over long distances
Forces that Influence Winds Geostrophic Winds Earth turning winds Travel parallel to isobars Spacing of isobars indicates speed; close = fast, spread out = slow Topic: Math & Geostrophic Winds V g = 1 x Δp fρd
Forces that Influence Winds Gradient Winds Aloft Cyclonic: counterclockwise Anticyclonic: clockwise Gradient wind parallel to curved isobars Cyclostrophic near Equator Observation: Estimates Aloft Clouds indicate direction of winds, place pressure in location consistent with cloud location.
Forces that Influence Winds Winds on Upper-level Charts Winds parallel to contour lines and flow west to east Heights decrease from north to south Surface Winds Friction reduces the wind speed which in turn decrease the Coriolis effect. Winds cross the isobars at about 30° into low pressure and out of high pressure Buys-Ballots Law
Winds and Vertical Motion Replacement of lateral spreading of air results in the rise of air over a low pressure and subsidence over high pressure Hydrostatic equilibrium and equation Topic: Hydrostatic equation Δp = -ρg Δz