geografia

• Weather is the state of the atmosphere at a particular place at a particular time.

  The science that studies it is meteorology.

  Weather is the result of three atmospheric phenomena:

  temperature, atmospheric pressure AND  precipitation.
• CLIMATE IS THE USUAL SUCCESSION OF WEATHER TYPES AT A LOCATION OVER THE COURSE OF THE YEAR.

  THE CLIMATE OF A PLACE IS DETERMINED BY STATISTICAL DATA FROM AT LEAST 30 YEARS OF OBSERVATIONS.

  THE SCIENCE THAT STUDIES IT IS CLIMATOLOGY.
• WEATHER AND CLIMATE ARE THE RESULT OF THREE ELEMENTS:

  TEMPERATURE.

  ATMOSPHERIC PRESSURE.

  PRECIPITATION.
• THE TEMPERATURE OF THE ATMOSPHERE IS NOT THE SAME ALL OVER THE PLANET, AS THERE ARE WARM, TEMPERATE AND COLD ZONES.

  TEMPERATURE CHANGES ARE DETERMINED BY LATITUDE, ALTITUDE AND CONTINENTALITY.
• LATITUDE IS THE DISTANCE OF A POINT ON EARTH FROM THE EQUATOR.

  The further a place is from the equator, the steeper the sun's rays reach it and the less heat the area receives. Temperature is measured in degrees Celsius (ºC).
• There are 3 climatic zones:

  -WARM ZONE, BETWEEN THE TROPIC OF CANCER AND THE TROPIC OF CAPRICORN, WHERE TEMPERATURES ARE HIGH ALL YEAR ROUND.--TEMPERATE ZONES, BETWEEN THE TROPICS AND THE POLAR CIRCLES.-

  -COLD ZONES, IN THE POLAR LANDS AND WITH VERY LOW TEMPERATURES.
• ALTITUDE IS THE VERTICAL DISTANCE OF A PLACE ON EARTH FROM SEA LEVEL.

  TEMPERATURE DECREASES WITH RESPECT TO THE HIGHER YOU GO, AT A RATE OF ABOUT 6.4ºC EVERY 1000 METRES.
• CONTINENTALITY IS DUE TO THE DISTANCE OF A PLACE ON LAND FROM THE COAST.

  -WHEN AN AREA IS CLOSE TO THE SEA, ITS TEMPERATURES ARE MILD.--WHEN IT IS FAR FROM THE SEA, TEMPERATURES ARE MORE CONTRASTED BETWEEN WINTER AND SUMMER.--The difference between maximum and minimum temperatures is called thermal oscillation. High thermal oscillation is also called CONTINENTALITY.
• Atmospheric pressure is the force or pressure of the air above the earth's surface.

  It is measured in a unit called hectopascal (hPa). Normal pressure at sea level is 1015 hPa.
• Areas of low pressure (below 1015 hPa) are called DEPRESSION or BORRASQUE.

  They occur when a warm, moist air mass rises, COOLING and CONDENSING, resulting in cloudy skies and RAINY weather
• High pressure areas (above 1015 hPa) are called ANTICYCLONES and occur when a cold, dry air mass descends, resulting in CLEAR skies and DRY weather
• On weather maps, areas with the same atmospheric pressure are drawn by ISOBARS, LINES CONNECTING POINTS WITH THE SAME PRESSURE.

  HIGH pressure zones or ANTICYCLONES are represented by the letter A, surrounded by a series of concentric ISOBARS.

  LOW pressure zones or DEPRESSIONS are represented by the letter B, surrounded by a series of concentric ISOBARS.
• Humidity is THE AMOUNT OF WATER VAPOUR IN THE AIR.

  When the air RISES, the water vapour COOLS and CONDENSES, forming CLOUDS.

  When the water droplets increase in size, PRECIPITATION (i.e. falling to the ground) occurs. It is measured in litres per square metre (l/m2) or millimetres (mm).

  1 l/m2 = 1 mm (1 mm high column of water).
• Precipitation can take several forms: the most frequent and important is in the form of RAIN. When the temperature is COLD OR VERY LOW the precipitation is in the form of SNOW or HAIL
• For precipitation to occur, there must always be a RISE OF AN AIR MASS. This rise can be due to several causes: 

  • RAINFORCE RAINS: These are the most important. They are caused by the action of a squall (low pressure area).
• CONVECTIVE RAINS: These are intense and brief rains (thunderstorms) caused by a rapid rise of an air mass due to the intense heating of the ground, typical of summer
• OROGRAPHIC RAINS: These occur in some areas when a mountain range impedes the passage of humid air masses, forcing them to rise.
• RAINFALL DISTRIBUTION VARIES ACCORDING TO CLIMATIC ZONES.

  -IN THE WARM ZONE, PRECIPITATION IS VERY AFFORDABLE. NEAR THE EQUATOR, RAINFALL IS SPREAD THROUGHOUT THE YEAR AND NEAR THE TROPICS, THERE ARE TWO SEASONS: THE WET AND THE DRY.--IN THE TEMPERATE ZONES, PRECIPITATION IS GENERALLY PROMINENT NEAR THE SEA AND HEAVY INLAND. INSOME CASES THEY ARE ABUNDANT.--IN COLD AREAS, RAINFALL IS LOW BECAUSE THERE IS HARDLY ANY EVAPORATION AS THERE IS LITTLE SUNSHINE, THE WATER FREEZES AND DOES NOT EVAPORATE.
• Temperate climates are located between 30 and 60 degrees latitude in both hemispheres
• Temperate climates have 4 distinct seasons according to their temperature and a precipitation between 400 and 1000 mm
• There are 3 types of temperate climates:

  • Oceanic climate: abundant and regular rainfall, mild temperatures with cold but not too cold winters and cool summers, little thermal oscillation. Occurs on the Atlantic coast of Europe, the Pacific coast of North America, and parts of Australia and New Zealand
  • Mediterranean climate: less abundant rainfall than oceanic, more irregular with rainier spring and autumn and little rain in summer, warmer temperatures with hot summers and very mild winters. Occurs around the Mediterranean Sea, California, Southern Africa, parts of Australia, Argentina, and Chile
  • Continental climate: hot summers and very cold winters with strong thermal oscillation. Occurs in the northern hemisphere: inland Europe, Asia, and North America
• WARM CLIMATES: They are located in the area between the Tropics of Cancer and Capricorn, i.e. from 30ºN to 30ºS. Temperatures are very warm all year round, with no cold season. Rainfall is abundant (except in the desert climate). There are 3 types:

          ■ Equatorial climate: located in areas north and south of the Equator (10ºN to 10ºS). Very warm and very rainy, all year round, there are no seasons. Thermal oscillation is very low.  Occurs in New Guinea, Congo and Amazon rainforests.
• Tropical climate:

  • Located north and south of the equator, around the tropics
  • Similar temperatures to the equatorial climate
  • Two distinct seasons: wet season in summer (very rainy) and dry season in winter
  • Found in central Africa, the Caribbean, most of South America, and South and East Asia
• Hot desert climate:

  • Located to the north and south of the tropical climate
  • Areas affected by anticyclones, receiving little rainfall
  • Warm temperatures year-round with strong temperature oscillation between day and night
  • Found in the Sahara, Arabian, Gobi, Australian, and Kalahari deserts
• COLD CLIMATES:

            ■ Polar climate: located in the polar zones of both hemispheres (60º - 90º N and S). very cold temperatures, always below zero. Very low precipitation in the form of snow.

           ■  High mountain climate: Occurs in the great mountain ranges at altitudes above 2500m. Very cold temperatures, although in summer they can rise above 0. Very abundant precipitation, in winter in the form of snow
• Oceanic climate:

  • Location: Galicia and the Cantabrian Coast
  • Characteristic: Very rainy all year round
• Coastal Mediterranean climate:

  • Locations: Balearic Islands, Guadalquivir Valley, and Extremadura
  • Characteristics: Hot summers and mild winters
• Continental Mediterranean climate:

  • Location: throughout the interior of the Iberian Peninsula
  • Factors: High average altitude (Central Plateau) and distance from the sea (continentality) result in cold winters
• Mountain climate:

  • Location: highest areas (above 1,500 m) of the great mountain ranges
• Subtropical climate in the Canary Islands:

  • Characteristics: Mild temperatures all year round, with hardly any seasonal differences