Weather is a term that encompasses phenomena in the atmosphere of a planet. The term usually refers the activity of these phenomena over short periods, such as hours or days. Average atmospheric conditions over significantly longer periods are known as climate.
Weather most often results from temperature differences from one place to another. On large scales, temperature differences occur mainly because areas closer to Earth's equator receive more energy per unit area from the Sun than do regions closer to Earth's poles. On local scales, temperature differences can occur because different surfaces (such as oceans, forests, or ice sheets) have differing physical characteristics such as reflectivity, roughness, or moisture content.
Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure. The resulting horizontal pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation then causes curvature of the flow via the Coriolis effect. The simple systems thus formed can then display emergent behaviour to produce more complex systems and thus other weather phenomena. Large scale examples include the Hadley cell while a smaller scale example would be coastal breezes.
The strong temperature contrast between polar and tropical air gives rise to the jet stream. Most weather systems in the mid-latitudes are caused by instabilities of the jet stream flow (see baroclinic instability). Weather systems in the tropics are caused by different processes, such as monsoons or organized thunderstorm systems.
Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December (see Effect of sun angle on climate). This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate (see Milankovitch cycles).
Weather forecasting is the application of science and technology to predict the state of the atmosphere at a future time. Prior to the advent of scientific methods of weather forecasting, a large body of weather folklore developed to explain the weather. An example is the Groundhog Day celebration near the end of winter in parts of the United States and Canada. Today, weather forecasts are made by collecting data that describe the current state of the atmosphere (particularly the temperature, humidity and wind) and using physically-based mathematical models to determine how the atmosphere is expected to change in the future. The chaotic nature of the atmosphere means that perfect forecasts are impossible, and that forecasts become less accurate as the range of the forecast increases.
2007-02-06 01:58:43
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answer #1
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answered by NIKKO23_99 3
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Weather is an all-encompassing term used to describe all of the many and varied phenomena that can occur in the atmosphere of a planet. The term is normally taken to mean the activity of these phenomena over short periods of time, usually no more than a few days in length. Average atmospheric conditions over significantly longer periods are known as climate. Usage of the two terms often overlaps as the concepts are obviously very closely related.
2007-02-06 19:06:49
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answer #2
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answered by razov 2
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Weather is a term that encompasses phenomena in the atmosphere of a planet. The term usually refers the activity of these phenomena over short periods, such as hours or days. Average atmospheric conditions over significantly longer periods are known as climate.
Weather most often results from temperature differences from one place to another. On large scales, temperature differences occur mainly because areas closer to Earth's equator receive more energy per unit area from the Sun than do regions closer to Earth's poles. On local scales, temperature differences can occur because different surfaces (such as oceans, forests, or ice sheets) have differing physical characteristics such as reflectivity, roughness, or moisture content.
Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure. The resulting horizontal pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation then causes curvature of the flow via the Coriolis effect. The simple systems thus formed can then display emergent behaviour to produce more complex systems and thus other weather phenomena. Large scale examples include the Hadley cell while a smaller scale example would be coastal breezes.
The strong temperature contrast between polar and tropical air gives rise to the jet stream. Most weather systems in the mid-latitudes are caused by instabilities of the jet stream flow (see baroclinic instability). Weather systems in the tropics are caused by different processes, such as monsoons or organized thunderstorm systems.
Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December (see Effect of sun angle on climate). This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate (see Milankovitch cycles).
Weather forecasting is the application of science and technology to predict the state of the atmosphere at a future time. Prior to the advent of scientific methods of weather forecasting, a large body of weather folklore developed to explain the weather. An example is the Groundhog Day celebration near the end of winter in parts of the United States and Canada. Today, weather forecasts are made by collecting data that describe the current state of the atmosphere (particularly the temperature, humidity and wind) and using physically-based mathematical models to determine how the atmosphere is expected to change in the future. The chaotic nature of the atmosphere means that perfect forecasts are impossible, and that forecasts become less accurate as the range of the forecast increases.
2007-02-08 00:02:30
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answer #3
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answered by Anonymous
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Yes. The sun is a source of vitamin B and people are generally happier and more confident in the summer. Sufferers of depression are more likely to be affected in gloomy weather. It affects some more than others though.
2016-03-29 07:29:05
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answer #4
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answered by Anonymous
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better look in a geographical site or a book.
or just go on observing the nature and its processes.
2007-02-06 00:16:12
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answer #5
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answered by lively 2
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Time to do your own homework.
2007-02-06 00:25:55
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answer #6
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answered by Gene 7
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