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Utorok, 30. septembra 2014
Weather and climate
Dátum pridania:03.05.2010Oznámkuj:12345
Autor referátu:24MoNi24
 
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WEATHER

Weather is given by state of all atmospheric phenomenon, watched on some place in some short period of time. This phenomenon is described by values of meteorological factors, which are measured by meteorological instruments or found out by observers.

Weather we usually understand as state of troposphere, because troposphere is the nearest and surrounds people.

Weather studies meteorology, or we can say physics of atmosphere. The thing, which forms weather on Earth is Sun, and Earth’s movement. Seasons are changing, because intensity of sunlight on the Earth’s surface is changing too. The Sun heats land and oceans, and it causes air turbulence. This energy influences also our weather.

Main factors which influences weather: sunlight, air pressure, air temperature, moisture, evaporation, wind direction and speed, cloudiness and the height of the snow blanket.

CLOUDINESS:

Cloudiness in meteorology means degree of clouds covering on the sky. It is important meteorological factor, which has big amount on the temperature of the Earth. Cloudiness is also not very exact name for group of clouds, we know for example frontal cloudiness, heap cloudiness, stratiform and high cloudiness.

On meteorological stations are defined volume, type, discernment of shapes and high of clouds. Cloud is visible system of little cells of water or ice – this water then rains on the Earth’s surface. This influences water cycles and also weather. From clouds we can know about temperature, humidity and movement in atmosphere.

EVAPORATION:

Evaporation is the slow vaporization of a liquid and the reverse of condensation. It is part of the water cycle. Solar energy drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water.

AIR PRESSURE:
In nature, pressure variations across the Earth´s surface are created by mechanical or thermal means. Heating and cooling the air (thermal mechanisms) create variations in air pressure. When air is heated it rises, and if pushed away in air, surface air pressure decreases. So if air is cooled, it subsides toward the surface causing air pressure increasing.

WEATHER FORECAST:
Very important is weather forecast, because weather influences all human activities. People depend on weather forecasts.

Weather forecasting is the process of science and technology to predict the state of the atmosphere for a future time and a given location. People tried to predict the weather informally for thousands of years, and formally since at least the nineteenth century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will develop. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe.

CLIMATE
Climate is commonly defined as the average of weather during long period of time. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, for example the magnitudes of day-to-day or year-to-year variations. Climate in a wider sense is the state, including a statistical description, of the climate system.
Over time spans there are a number of static variables that determine climate, for example latitude, altitude, proportion of land to water, and nearness to oceans and mountains. Other climate determinants are more dynamic: for example, the thermohaline circulation of the ocean, warming of the northern Atlantic ocean compared to other oceans. Other ocean currents redistribute heat between land and water on a more regional scale. Alterations in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming or global cooling.
Climate change refers to the variation in the Earth's global climate or in regional climates over time. It describes changes in the average state of the atmosphere. These changes can be caused by processes internal to the Earth, external forces or nowadays human activities.
In recent usage, especially in the context of environmental policy, the term "climate change" often refers only to changes in modern climate, including the rise in average surface temperature known as global warming. In the past, on the Earth were also other climates – including four ice ages.
Main influencing factors:

LATITUDE:

Latitude describes position on the Earth’s surface, on the north or south from equator. We measure latitude in degrees – on equator is zero latitude, and to poles the number of degrees is increasing. But with sunlight its opposite – from equator to poles, the sunlight is decreasing.
OCEAN CURRENTS:
An ocean current is a continuous, directed movement of ocean water formed by the forces which are acting upon the water, such as the Earth's rotation, wind, temperature, salinity differences and tides.
Ocean currents can flow for thousands of kilometers, and together they create the great flow of the global conveyor belt which plays a dominant part in determining the climate of many of the Earth’s regions. Perhaps the best example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude.
ALTITUDE:
Altitude is distance (altitudinal difference) of some place, according to sea level. Altitude is measured in meters above the sea level. High of sea level is given by long-lasting and regular observation of tides. On the map, altitude is written with contour lines, altitude which is under sea level is expressed like negative number.

HUMAN ACTIVITY:

Most scientists believe that human activity is changing the composition of the atmosphere by increasing the concentration of greenhouse gases (GHGs). Greenhouse gases occur naturally in the atmosphere and their results is the greenhouse effect. We must remember that the greenhouse effect is what keeps the Earth warm enough for living.
The recent attention given to the greenhouse effect and global warming is based on the recorded increases in concentrations of some of the greenhouse gases due to human activity. Of particular interest are water vapor, carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone. With the exception of chlorofluorocarbons, all of these gases occur naturally and are also produced by human activity.

CLIMATIC ZONES IN THE WORLD

1.equatorial climate – high humidity, high average temperature, day and night have the same length (Indonesia, about rivers Congo and Amazon)
2.subequatorial climate – changing of season of rain and dry season, savannas, zone of equatorial monsoons (southern-east Asia)
3.tropical climate – deserts, 3 types of seasons: hot rainy, hot dry and cool dry, low precipitations (Sahara, Atacama, Kalahari)
4.subtropical climate – dry and hot summers, moderate winters, higher humidity, moderate precipitations (California, South of Europe, South of Australia)
5.temperate zone – 4 seasons are changing, moderate precipitations (Europe, North America, Russia, Canada, Mongolia)
6.sub-arctic zone – short summer and long winter, tundra, low precipitations (North America, north of Europe)
7.arctic zone – precipitations are low, always snow and ice (Greenland, Antarctica)

 
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