Weather Variables: Air Pressure, Temperature & Density - Video & Lesson Transcript | jogglerwiki.info
pressure patterns drive wind patterns which in turn drive oceanic circulation patterns. atmospheric & oceanic circulation: major mechanisms for. The wind blows because of differences in air pressure from one location to another. Wind blows from areas of high pressure toward areas of low pressure. 15 Lessons in Chapter 5: Atmospheric Pressure and Wind In this video lesson, we'll go one step further, examining how to rearrange the equation to solve for.
The basic pattern of surface ocean circulation, including the large-scale gyres, is caused by wind and the factors that produce large-scale wind patterns.
We need to start by seeing how solar energy input on Earth and poleward transport of heat by winds sets up large-scale atmospheric cells that produce Easterly and Westerly winds in three main bands from the equator to the poles.
The Coriolis effect, produced by Earth's rotation and conservation of momentum, plays an important role here. Ocean structure also plays an important role and we need to look at density driven circulation in the ocean as produced by temperature and salinity: Ocean circulation is three-dimensional and both surface currents and deep water currents play an important role in heat transport.
5. Atmospheric Pressure & Wind
Large-scale ocean currents are impacted by the Coriolis effect, and depth-variations in coupling between surface flow and wind stress produce another important effect, known as Ekman transport, which we will discuss. Ultimately, when we put all the pieces together, the goal is to arrive at a coherent picture of how solar energy, winds, and ocean circulation combine to produce a global thermostat for Earth.
Note the three-dimensionality of the circulation. On the right-hand side of the image the arrows show vertical and horizontal air flow as part of six convection cells, three in each of the Northern and Southern hemispheres.
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The central part of the image shows surface winds blowing from the east the Trade winds or the west The Westerlies --note that the Polar Easterlies are not easily seen in this image. Atmospheric Circulation and the Trade Winds Source: NASA Hadley circulation One of the most important things to understand from this image is that everything is driven by unequal solar heating as a function of latitude.Air Pressure and wind
The energy from our Sun is focused on the equatorial region and spread comparatively thinly over the polar regions.
This is true on an average annual basis, Earth receives more solar energy at the equator than at the poles. As a result, the land, water, and air, over the equator are warm, and air rises over the equator. This warm air rises through the atmosphere and flows poleward as an upper atmosphere wind that is, essentially, an air-mail package of heat known as a Hadley Cell. The image here has arrows showing circulation in a vertical plane along a line of longitude just to the east of the African continent but, of course, this circulation occurs at all longitudes.
Hadley circulation is 3D; heat moves poleward in upper atmosphere winds and there is a return flow from north to south in the Northern hemisphere that sets up the Northeasterly Trade winds with the help of the Coriolis effect, as we'll see below. Pressure belts The Hadley Cell is set up by rising air over the equator. It begins with warming of air surrounding the equator, which creates a large region of lower surface pressures due in part to the fact that columns of warm air weigh less than columns of cold air.
The convergence of warm, moist air over the equator transports large volumes of air aloft, to the top of the troposphere. This air is confined vertically by the base of the stratosphere and thus spreads out north and south toward the poles. Because of Earth's spherical shape, the poleward-flowing air is compressed into an increasingly smaller volume as it moves away from the equatorial region.
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The airmasses also cool as they move poleward. This should be mostly review, as these concepts were covered in the Snow Sports Learning Goals e. On a weather map, cold fronts are indicated by a blue line with blue triangles, a warm front is indicated by a red line with red half circles, and an occluded front is indicated with a solid purple line with alternating triangles and half circles.
A stationary front is represented by a mixed red and blue line with triangles and half circles pointing in opposite directions. The triangles and circles are pointing in the direction of movement.
Weather Variables: Air Pressure, Temperature & Density
An occluded front is a cold front that has caught up with and overtaken a warm front, which is sometimes observed around low pressure centres. A stationary front develops when neither the warm or cold air mass has sufficient energy to displace the other, and so a non-moving boundary develops.
In the image below, note how the fronts connect near centres of low pressure, and yet centres of high pressure are generally without fronts: NOAA The concentric circles or lines on the map are called isobars and indicate a specific air pressure see Learning Goal 5d for more info on isobars.
The isobars closest to the middle of a circle will have the highest pressure, with isobars of decreasing pressure radiating out from the centre. Wind likes to travel from high to low pressure, but it does not move directly across isobars, due to the Coriolis effect.
It curves around areas of high or low pressure. Remember, in the Northern Hemisphere, wind spirals counter-clockwise around points of low pressure and clockwise around high pressure, and the opposite is true in the Southern Hemisphere. Much like tightly spaced contours on land maps indicate steeper terrain, closely spaced isobars indicate more dramatic differences in air pressure, and thus faster wind speeds.
Areas of low pressure are also called depressions. In the image below, you will see a high pressure system approaching the coast of BC and Washington.
A low has just passed over the Vancouver area and is moving south. Each one tells you something about the conditions at that exact location.