The climate is the result of numerous factors that act together. Geographical accidents, such as mountains and seas, decisively influence their characteristics.
To determine these characteristics we can consider as essential a small group of elements: temperature, humidity and air pressure.
The combinations of these three elements define both the weather of a particular moment and the climate of an area of the Earth.
The temperature and the thermal sensation
The atmospheric temperature is the indicator of the amount of heat energy accumulated in the air. Although there are other scales for other uses, the air temperature is usually measured in degrees Celsius (ºC) and, for this, an instrument called thermometer.
The temperature depends on various factors, for example, the inclination of the sun's rays. It also depends on the type of substrates (the rock absorbs energy, the ice reflects it), the direction and strength of the winds, latitude, height above sea level, proximity of bodies of water ...
However, we must distinguish between temperature and thermal sensation. Although the thermometer shows the same temperature, the sensation we perceive depends on factors such as humidity and wind force. For example, you can be at 15º in short sleeves in a sunny and windless place. However, at this same temperature in the shade or with a wind of 80 km / h, we feel a sensation of intense cold.
Humidity indicates the amount of water vapor that is present in the air. It depends, in part, on the temperature, since hot air contains more moisture than cold.
Relative humidity is expressed as a percentage (%) of water in the air. Absolute humidity refers to the amount of water vapor present in a unit of air volume and is expressed in grams per cubic centimeter.
Saturation is the point from which a quantity of water vapor cannot continue to grow and remain in a gaseous state, but becomes liquid and precipitates.
To measure humidity an instrument called hygrometer.
Atmospheric pressure is the weight of the mass of air for each surface unit. For this reason, the pressure is usually higher at sea level than at mountain peaks, although it does not depend solely on altitude.
Large pressure differences can be perceived with some ease. With a high pressure we feel more tired, for example, on a sultry summer day. With a pressure that is too low (for example, above 3,000 meters above sea level) we feel lighter, but we also breathe harder.
The "normal" pressure at sea level is about 1,013 millibars or hectopascals (also called "an atmosphere") and decreases progressively as it rises. To measure the pressure we use the barometer.
The differences in atmospheric pressure between different points of the earth's crust cause the air to move from one place to another, causing the winds, fronts, storms and anticyclones. In time maps, points with similar pressures join forming lines that we call isobars.
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