GHY 104 1st Edition Lecture 8Ch. 6 Atmospheric & Oceanic CirculationsWind Essentials- Imbalance between equator & polar energy is driving force of weather- Air pressure and its measurement- Key to understanding wind - A product of temperature and density of air- Standard is 1013.2 mb (normal sea level)- Mercury barometer (Torricelli)- Aneroid barometer (no liquid, more compact)- Pressure driving force for wind- Wind: Direction & Measurement- Wind- horizontal movement of air- What produce wind? Different air pressure or density- High pressure – great weather - Low pressure – rain- Anemometer – measures wind speed in kmh, mph, mps, or knots- Knots- nautical mph, covering 1 min. of Earth’s arc in 1 hour- Wind Vane – determines direction: 33 ft off groundWind Direction- Winds named for direction from which they originate Wind Portrait of the Pacific Ocean- 4 Forces- PGF – Pressure Gradient Force- Coriolis- Friction Force- GravityDriving Forces within the Atmosphere- Gravity- Uniform; counteracts centrifugal force- Density decreases, as altitudes increases- Heavy air (cold) SINKS, light air (warm) RISES- Pressure Gradient- Difference in pressure across the Earth’s surface that encourages air flow from one place to another- Drives air from H (more dense) to L (less dense)- Isobar - a line that connects points to equal air pressure across the Earth’s surface- Coriolis Effect- Basically, a deflection or change in direction caused by Earth’s rotation- Deflection regardless of direction is moving - Without CF, winds would move in straight direction- Curve Right in North Hemisphere & Left in Southern Hemisphere- Force increases as speed increases; no affects at small scale- Friction Force- Hinders air flow from one place to another = Drag- Without drag, winds would move in paths parallel to isobars & at high rates of speedIsobars & Pressure Gradient- The closeness of isobars indicates the gradient between High & Low pressure- The closer the isobars, the higher the wind speed- The farther apart they are, the lower the wind speed- Winds at the surface always begin by blowing at right angles to the isobars- Upper Atmosphere Travel Parallel to the isobars- Remember – forces in nature tend to move from areas of surplus to areas of