Climate Factors and Atmospheric Dynamics in the Iberian Peninsula

Key Factors Influencing the Climate of the Iberian Peninsula

Latitude: Situated between 35º and 43º North, the Iberian Peninsula lies within the temperate zone, experiencing four distinct seasons. Location: Nestled between the Atlantic Ocean (more open and cooler) and the Mediterranean Sea (smaller, enclosed, and warmer). Water bodies cool and heat more slowly than continents, so the coasts are affected by the sea's thermoregulatory effect, preventing excessively high temperatures. Influence of the Sea: Relatively low, with continental influence being more significant. The Peninsula behaves climatically like a small continent; the land cools and heats rapidly, leading to significant temperature variations both daily and annually. In winter, high-pressure centers form, bringing down temperatures, while in summer, low-pressure centers develop, leading to storms. Altitude: The Peninsula's high average altitude influences temperature, decreasing it by approximately 0.65°C per 100m. It also causes orographic rainfall. Relief: Besides lowering temperatures, the terrain also influences precipitation. The Foehn effect dries leeward slopes. It also affects insolation, creating areas with more sunshine and shade. Arrangement of Relief: The parallel layout to the coast hinders the sea's influence, except in the Guadalquivir Valley. Eastbound Position of Mountains: This blocks the influence of air masses originating from the north or south, favoring western air masses. Catchment Areas Enclosed by Mountains: Areas like the Duero and Ebro basins experience low rainfall and frequent fog due to stagnant air.

Atmospheric Circulation and its Impact on the Iberian Peninsula

General Principles: In temperate latitudes, atmospheric circulation is regulated in altitude by the "jet stream."

Surface Circulation: Dominated by dynamic action centers (high and low pressure), air masses, and fronts. Circulation at Altitude: Jet Stream (I): A strong wind flow with a tubular structure, circulating west to east between 9,000 and 11,000 meters in altitude, in the height difference between the polar and tropical tropopause. It separates the low pressure present at the pole from the tropical high pressure. It influences surface weather depending on its latitude and the seasonal variations of its velocity. Circulation at Altitude: Jet Stream: When its speed is high (from 150 km/h), it describes a zonal path (west-east) with gentle undulations corresponding in size with the polar front and its associated storms. When it loses speed, it forms deep undulations: crests or ridges give rise to high pressures, reflected in surface anticyclones. Troughs originate low pressures, resulting in surface storms. These undulations allow polar air to penetrate deeply into the south in the temperate zone, resulting in unsettled weather. The seasonal movements of the jet stream cause it to affect the Peninsula more in winter, with reduced influence in summer (when it mainly affects the Cantabrian Sea).

Action Centers, Air Masses, and Fronts

Action Centers: Areas of high and low pressure. High Pressure or Anticyclone: A high-pressure zone (above 1013.5 mb) surrounded by lower pressure. Winds circulate clockwise, producing stable weather. Low Pressure or Storm: A low-pressure area (below 1013.5 mb) surrounded by higher pressure. Winds circulate counterclockwise, producing unstable, often rainy weather. Origin of Action Centers: Action centers can have a thermal or dynamic origin. Thermal Action Centers: Formed by cooling or warming air. Thermal Anticyclone: Forms when an air mass cools; the heavier cold air descends, exerting high pressure. Thermal Low: Forms when air is heated; the lighter warm air rises, creating low pressure. Dynamic Action Centers: Formed from crests and troughs in the jet stream, reflected on the surface. Crests generate anticyclones, while troughs generate depressions or storms. Air Masses: Volumes of air with specific temperature, humidity, and pressure characteristics. They acquire these properties in their source regions. Spain is influenced by these air masses: Cold Air Masses: Arctic (A), Polar (P). Warm Air Masses: Tropical (T). Depending on the surface over which they form: Maritime (wet, m), Continental (dry, c). Fronts: Surfaces separating two air masses with different characteristics. The polar front is the most significant in the Iberian Peninsula, separating tropical and polar air masses. The undulations of the polar front generate winds responsible for precipitation.