Presentation on theme: "The Air we breath is composed of……. The gases above they all have some weight and since then they all exert a force, or pressure, on our bodies = athmospheric."— Presentation transcript:
The Air we breath is composed of……. The gases above they all have some weight and since then they all exert a force, or pressure, on our bodies = athmospheric pressure. Air moves because of differences in both temperature and pressure, also called atmospheric pressure, which is the pressure exerted by the atmosphere at Earth's surface due to the weight of the air. What causes wind? Nitrogen, Oxygen, Argon, Carbondioxide, Water vapor and some other gases…
Why is the wind interesting? Effects on people and buildings. Aircraft Wind power. Sailing Air-pollution, Radioactivity Etc.
Cup anemometer The wind Wind direction, from which it’s blowing Direction 0 -360º or N, S, W, E, ”true north” NNV = 340 º Speed units: m/s, kt, mph, km/h, kuling etc. 1 m/s = 1.94 kt 1 kt = 0,51 m/s Wind vane
1)What are the different units of pressure? Which unit is used most by meteorologists? 2)Which is the correct respons in the following sentence: ’Pressure increases/deceases with height’. Please explain why pressure changes this way with height. 3)Draw the symbol that represents a high pressure center on a weather map. Do the same for a low pressure center. 4)Pictured left are two imaginary columns of air molecules exerting pressure on the surface below them. The left column contains fewer air molecules than the right column. What do they represent? Pressure…. Characteristics
Pressure Gradient Force directed from high to low pressure The change in pressure measured across a given distance is called a "pressure gradient". The pressure gradient results in a net force that is directed from high to low pressure and this force is called the "pressure gradient force".
Coriolis Force Effect of the Earth's rotation on the atmosphere, oceans, and theoretically all objects moving over the Earth's surface. In the northern hemisphere it causes moving objects and currents to be deflected to the right; in the southern hemisphere it causes deflection to the left. The effect is named after its discoverer, French mathematician Gaspard de Coriolis (1792–1843).
Gradient wind Clockwise rotation: Centrifugal force (Cf) and PGF are co-operating C must be greater in a balanced situation compared with the Geostrophic wind Vgr > Vg, if PGF and latitude is the same
Gradient wind Anti-clockwise rotation: Cf and C are co-operating C must be lesser in a balanced situation compared with the Geostrophic wind Vgr < Vg, if PGF and latitude is the same
Cumulunimbus Showers of rain/snow Hail Thunder Tornados
Precipitation Along Fronts II Warm front A layer of thin clouds is occasionally observed more than a thousand kilometers in advance of a surface warm front. As the front gets closer, the clouds thicken and eventually light precipitation begins to fall. Because the frontal surface gently slopes up and over the cold air mass ahead of it, the upward motions associated with warm fronts are typically not as strong as the vigorous upward motions that occur ahead of a cold front.
Precipitation Along Fronts I Cold Front Initially, the cold air mass wedges into the warmer air mass ahead of it, (separated from each other by the cold front). The lighter warm air is lifted upwards by the denser cold air and if enough water vapor condenses, clouds develop. If condensation of water vapor persists, precipitation may develop, typically in a narrow band just ahead of the cold front. Due to the steep slope of a cold front, vigorous rising motion is often produced, leading to the development of showers and occasionally severe thunderstorms.