Mezquita
The climatology , connects physical Géographie, is the study of the Climat, i.e. the succession of the weather conditions over long periods in time. The study of short-term time is the field of the Météorologie.
In general, the climate does not vary, or rather little, in a given place of the sphere, over one duration of the scale of the Siècle. But over geological times, the climate can change considerably. For example, the Scandinavia knew several glacial periods in the last million years. The study of the last climates is the Paléoclimatologie. This study according to the human history is called historical climatology .
Climatology rests on historical weather statements, as measurements raised by satellite, but also the thickness of the snowy coat, the retreat of the glaciers, the chemical analysis of the air imprisoned in the ice, etc
The knowledge of many parameters, like the temperature at various altitudes, the influence of the Gas to greenhouse effect, the relative humidity, oceanic evaporation, is necessary to produce numerical climatic models and to anticipate the changes of the climate which one can provide with more or less long run (30 years).
If climatology is interested primarily in the study and classification of the existing climates on ground, part of the discipline treats also interaction between Climat and company; that it is the influence of the climate on the Man or the Man on the climate.
The Man and climate: history of climatology
August 1st
Large elements of the climatic system
Atmosphere
See also: Terrestrial atmosphere
August 1st
Atmosphere . of the Greek atmos - wet vapor and sphere One often understands by the term atmosphere, the first of his layers, namely troposphere. The atmosphere is a fundamental gas envelope with the existence of the Living beings and Life in terrestrial environment. This one also plays an important role in the cycle of water. (evaporation=precipitation)
The AIR in its center is defined in term of temperature, pressure, wet load and movements or direction (horizontal and vertical).
The part of the atmosphere nearest to the Earth is thus the troposphere, in which the principal weather phenomena are played. This layer of the atmosphere does not appear regular in measurement or one observes a greater thickness on the level of the equator (17 with 18km).
atmospheric termic Structure and layers. ----
The presence of gradians will be noted termic which varies on a horizontal scale of troposphere to the ionosphere. Until approximately 15 km of altitude the temperature decreases (higher troposphere)
The air, in this low layer (8 with 9km) is subjected to important turbulences. This instability with for origin reliefs as well as the contrasts termic generated by the great continental and oceanic units. The tropopause constitutes the higher limit of troposphere. The average temperature is there of -57°C.
stratosphere .
of 15km with 50. The temperature recovers to increase gently. The cause is simple and comes from the absorbtion by the ozone which it contains of the rays Ultra-violet. The jet stream, current horizontal major finds its place in this stratosphere. The stratopause is the higher limit of this layer.
the mésosphère .
from 50 with 80km.
The gradian termic becomes again negative. It is with 80km of altitude of approximately - 65°C. The mésopause constitutes its higher limit.
the ionosphere .ou termosphère from 80 with 100km approximately. The temperature strongly increase. One attends inside this atmospheric layer the phenomenon of dissociation of the molecules of hydrogen and of dioxygène.*La termopause, limit superior remains vague.
The role of solar energy
August 1st
The greenhouse effect
See also: Greenhouse effect
Atmospheric circulation
See also: atmospheric Circulation
Climatic diversity
the climatological scale.space scales of the climate.
regional climates.
the scale of the regional climates or mésoclimats, which applies to areas of several thousands of square kilometers, subjected to certain quite particular weather phenomena (Sirocco, wind come from the desert) because of interaction between general circulation and the relief. The climate of Alsace, drained by the effect of foehn, provides a typical example of regional climate.
local climates .
the scale of these climates applies to sites which extend on a few tens of square kilometers at most on average. This scale of the climate remains in close connection with the environmental characteristics of a not very wide space. The presence of reliefs (mounts induisants of the valleys, relief of cuesta,…), of watery extents (lakes, ocean, river,…) will influence the phenomena of winds, moisture and variations in temperature. In bottom of valley for example, with the survey of the day, the temperature will be much less high than at the top of the slopes in adret, however located a few kilometres from there. Circulation, the exchanges between local masses of air will thus not be the same ones as in the close valley, can be directed differently compared to the sun. These characteristics can have a human origin - it is primarily about the urban climate - or being maintained by a natural environment such as a marine or lake shore or a forest.
the microclimates .
This scale, finally, relates to large not very wide sites of a hundred square meters, sometimes much less. Features specific of topography and the environment to small scales - various buildings and obstacles, vegetable cover, rock niches… - modify in this case on reduced surfaces, but in a very notable way sometimes, the general characteristics of the airstream, sunning, temperature and moisture.
How to classify the climates?
August 1stThe system of Köppen
See also: Classification of Köppen
In the years 1920, the climatologist Wladimir Peter Köppen develops a system classification of the climates based only on precipitations and the temperatures. A climate is thus located by a code of two or three letters.
Examples:
- the the Sahara, or the Arabian desert , are of type BWh (B = dry Climat; W = Climate desert; H = annual Average temperature > 18°C)
- the equatorial Zone is of type Af (has = tropical Climat; F = Climat wet without season dries)
- the France of north east of the type Cfb (C = hot moderate Climat; F = Climat wet without season dries; B = be moderate)
The system of Martonne
In first half of the 20th century, the French geographer Emmanuel de Martonne works out a system of classification of the Climat S by a statistical method. He uses an aggregative index gathering of the hydrometric and thermal data. This statistical method will be taken again thereafter for the classification climatic and improved thanks to the development of average the information and measurement techniques on the climate.
Climate changes
See also: Climate change
Risk, risks and vulnerability of the companies vis-a-vis the climate
August 1st
See too
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