Climate Factors and Atmospheric Circulation Dynamics

Climatic Diversity and Influencing Factors

The diversity of climate is determined by several factors:

• Latitude: Determines the existence of seasons (winter, summer, and the two transition seasons: autumn and spring).
• Location: Situated between two major bodies of water (the Mediterranean and the Atlantic) and two continents (Europe and Africa), this location acts as a crossroads, influencing air masses.
• Sea Influence: The influence of the sea is scarce in the peninsula compared to peripheral areas and archipelagos.
• Relief: Relief has a marked influence. The disposition of mountain systems acts as a barrier, limiting maritime influence only to the west, penetrating the Guadalquivir valley. Mountains also form air basins (north) and enclosed areas (south).
• Mountain Ranges (Duero, Ebro): These ranges often experience scarce precipitation because air masses develop their humidity over the mountains themselves.
• Altitude: Altitude causes precipitation when air masses are forced to rise (windward side).
• Guidance (Orientation): Climatic contrasts originate from the effect of sun exposure (sunshine) and shade (Umbria).

Thermodynamic Factors and Atmospheric Circulation

Thermodynamic factors are responsible for the atmospheric circulation, which is governed by:

Circulation in Height: The Jet Stream

This circulation occurs in the temperate zone and is known as the Jet Stream (or current). It is a strong current flowing from west to east.

The Jet Stream is responsible for the weather, which depends on its speed:

• When traveling faster, it causes mild circulations.
• When its velocity decreases, it describes dorsal ridges or anticyclones, leading to storms (borrascas).

The seasonal movements of the Jet Stream affect the climate. In winter, it circulates further south. In summer, it moves north and influences the Cantabrian region.

Surface Circulation: Centers of Action, Air Masses, and Fronts

Surface circulation is directed by Centers of Action (areas of high and low pressure).

Atmospheric Pressure Systems

Atmospheric pressure is the weight of air above a unit surface area. It is represented on weather maps by isobars (lines joining points of equal pressure).

High Pressure (Anticyclone)

An anticyclone is an area of high pressure surrounded by lower pressures. Winds circulate in a clockwise direction (in the Northern Hemisphere), producing stable weather.

Low Pressure (Storm or Cyclone)

A storm or cyclone is an area of low pressure surrounded by higher pressures. Winds circulate counter-clockwise (in the Northern Hemisphere), producing unstable, often rainy weather.

Origin of Centers of Action

Centers of action can be:

• Thermal: Formed by the cooling or heating of air.
  • A thermal anticyclone forms when an air mass cools, weighs more, and increases pressure.
  • A thermal low forms when air is heated, rises, weighs less, and has less pressure.
• Dynamic: Generated from peaks and valleys (e.g., dynamic anticyclones and cyclones).

Main Centers of Action

The main centers of action include:

• Anticyclones (High Pressure):
  • Azores Anticyclone (in summer and winter, moving south).
  • Polar Anticyclone.
  • Scandinavian Anticyclone.
  • Anticyclones over the European continent and the interior of the peninsula.
• Depressions (Low Pressure):
  • Icelandic Depression.
  • Gulf of Genoa Depression.
  • Depressions over North Africa and the interior of the peninsula.

Air Masses and Fronts

Air Masses are large bodies of air with concrete characteristics. They can be continental or maritime.

Fronts are surfaces that separate two different air masses. The most important is the Polar Front, which separates tropical air masses and polar air masses. Storm waves and rainfall originate along the Polar Front.