Global Circulation
Air is something that we all take for granted. We breathe it every day, we look through it, we pollute it. Most of the time, we don’t even notice it. But it can quickly make its presence known when wind is involved. Wind, in general is just moving air, and although in its stationary state it may seem harmless, once started, it is a force to be reckoned with; it can uproot trees, lift roofs of buildings, and generally wreak havoc. It is caused by differences in air pressure within the atmosphere, and the driving force behind all of that is the solar radiation.
Earth is almost spherical and because of its tilt, the sun’s rays hit the area near the equator at an almost right angle, while the areas further away are hit at a smaller angle. This means that the concentration of heat received at the equator is higher, and therefore the air warms quicker there than in the pole-ward regions. The air molecules expand and lift when they are heated, and that, coupled with differences in temperature sets the atmosphere in motion in a massive global chain reaction. The air lifted from the equator creates a low-pressure zone, and is replaced by winds from higher-pressure zones and then in turn, something has to move the air toward them. This air movement is affected by many factors, which makes it even more complicated and harder to understand, but scientists have come up with idealised models of general circulation.
They separated the sphere into three belts, or cells north and south of the equator – the Hadley cell ranging from the equator to about 30° N and S, the Ferrel cell from about 30° to about 60° N and S and the Polar cell from about 60° N and S toward the poles.
The polar cell is a relatively simple system....
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...nfall deficiency. While the eastern and southern parts receive an ample amout of rainfall during the onset phase, while the northwestern part suffers from a shortage of rain because of a heat low circulation over the region.
Summer Monsoon – Withdrawal Phase (September – November). Summer monsoons usually withdraw the way they cam, but in the reverse direction, although it happens very gradually – it is marked by a weakening in the heat low over the subcontinent, a reversal of the wind from southerly to northerly and a decrease in rainfall. This brings cooler and drier air from the north. It moves very quicly in the beginning, but then slows down after withdrawing over half the subcontinent. Winds from northeast start intruding and cause some more rain to occur in the withdrawal phase.
Works Cited
Ramage, CS (1971) Monsoon Meteorology. Academic Press, New York.
Lackmann, Gary. Midlatitude Synoptic Meteorology: Dynamics, Analysis, and Forecasting. Boston, MA: American Meteorological Society, 2011. Print.
There are numerous stages that take place simultaneously in the hydrologic cycle and this includes evaporation. This is when the water alters from a liquid state into a gas. The damp air from the water rises into the atmosphere and when it cools, the vapor condenses and shapes into clouds. But those billows are not the only form the vapors make; it can also materialize as dew, fog and mist, which blanket the Earth, characteristically on a rainy or humid day. Evaporation takes place when water changes from a liquid state into a gaseous state, and ascents out of the pores of the earth and into the atmosphere as a vapor (“How”). While evaporation is taking place, condensation is also occurring. When the temperature in the air plunges, the clouds become heavy and as a result they relieve themselves of the extra weight, which is called precipitation. This produces rain, hail, snow and sleet, conditioned upon the temperate. As the precipitation falls, it enters the surface of the ground and percolates into the soil, which is called infiltration. The more porous the land is, the more the infiltration can take place. However, the ground cannot hold all of that water and floods. The excess rainfall, which is also called runoff that has not been absorbed makes its way into bodies of water, such as small ponds, rivers, lakes and parts of the ocean (“Summary”).
Second, long term and short term climate changes (e.g. global warming and El Nino) may lead to dryness. Global warming rises
There are three ways the sun's heat and energy are transferred throughout the atmosphere: radiation, conduction and convection. The sun's radiation heats the surface of the earth and the resulting heat is transferred to the atmosphere primarily by convection. Conduction is a minor contributor to the overall process since the transfer of heat via the air is a slow, inefficient process. Convection is the vertical process that carries warm air up from the ground to be replaced by cooler air, which in turn is warmed, and cycles upward again. On a global scale, convection is responsible for the atmospheric circulation which redistributes heat from the warm equatorial regions to the poles. The Coriolis effect, the apparent curvature of winds and ocean currents due to the earth's rotation, causes the atmospheric circulation to be divided into three convective zones per hemisphere: Hadley cells (tropical), Ferrell cell (temperate) and the Polar cell (UXL Encyclopedia of Weather and Natural Disasters). These convection cells along with horizontal advection are responsible for global wind patterns. On a smaller, local scale, convection currents are linked to the development of deep convective clouds and local storm systems. Because precipitation is central to the earth's energy balance, circulation, and water cycle, atmospheric scientists have focused their efforts on understanding how pollution effects the development and intensity of convection currents, cloud cover, precipitation, and thunderstorms.
As the warm air mass rises it condenses into a series of clouds. The warm front brings light rain and also light snow. All this is followed by warmer and milder weather.
During El Nino there is less precipitation over Australia. During La Nina there is increased humidity and precipitation inland over Australia. During the neutral phase the air rising in the west and falling in the east can be further described as Walker Circulation (an atmospheric loop where the trade winds blue from east to west in the Pacific).
Water vapor goes into the air, and releases latent heat of condensation. The water vapor turn into clouds and rain warming the surrounding air. The hurricanes winds then spiral around and around and push the water vapor into the
The atmosphere rises to 500 km above Earth's surface. The atmosphere is divided into four parts based on temperature change in relation to change in altitude. The four parts are the: Troposphere, Stratosphere, Mesosphere, and Thermosphere. This paper will be discussing instability in the Troposphere, the lowest level, since it is where the Earth's weather takes place. Tropospheric instability often times yields severe weather, such as tornadoes. A Tornado is a violently rotating column of air in contact with the ground and pendent from a cumulonimbus cloud. A tornado's fierce winds have the ability to severely impact the lives of humans by: turning innocent stationary objects into flying missiles, collapsing buildings, and even throwing people hundreds of yards. One researcher summarized tornadoes well when he said "Tornadoes are one of the World's strongest forces, and they will not stop at anything that will get in their way!"(Elias Demakes).
season, and what season it comes in either a dry winter or a dry summer. The
A hurricane is caused when a large mass of air is warmed up and the
An El Nino happens in intervals of 3-7 years. The formation of this is related to the Pacific Southern Oscillation which is also the cycling of the Pacific Ocean circulation. The Pacific Southern Oscillation (the change of atmospheric pressures) happens when the easterly trade winds collapse, weaken, or even reverse. As this happens, the upwelling stops. The slight weakening of the winds cause a small change in sea surface temperatures, and the wind and pressure changes increase. The warm water of the western Pacific Ocean flow eastward and sea surface temperatures increase on the western coast of South America. When this occurs, the wet weather conditions (originally in the western Pacific) move east, and dry conditions (normally in the east) appear in the west.
a change in the water cycle. Some places may experience more rain. Warmer temperatures will
Air is composed of molecules. Air is matter. It has mass and takes up space. Air is composed of different gases such as nitrogen, oxygen, carbon dioxide, water vapor, and other gases. Air molecules are in constant motion. As they move, they come in contact with surfaces. Air molecules push and press on the surfaces they contact. The amount of force per unit area that air molecules exert on a surface is called air pressure. (What is Air Pressure 6) Air pressure is caused by all of the air molecules in the Earth's atmosphere pressing down on the Earth's surfaces. We can measure air pressure to help us predict weather conditions around the world. Temperature also affects air pressure because air contracts when it cools and expands when it is heated. So if air above a region of Earth cools, it does not extend to as high an altitude as the surrounding air. In this case, its pressure at higher temperature is lower than in the surroundings even when the pressure at the surface is the same as in surrounding areas. Then air flows into the cooler region at high altitude, making the total weight of air above the region greater than in the surroundings. This is a "high". The cool air descends to the earth's surface. Near the surface, the falling air spreads out,
The thermohaline circulation cycle (THC) delivers heat to the North Atlantic. In the winter the heat from the water is released into the eastward moving air masses like the Gulf Stream, thereby warming much of western and northern Europe. Cooling in the North Atlantic increases the density of the 'upper ocean water' to the point at which it becomes so dense that it sinks to the bottom and flows south towards the Antarctic, forming the 'lower limb' of this conveyor belt of North Atlantic Deep Water (NADW) (1583 Broecker).