Key Meteorological and Climatic Concepts

Fundamental Weather and Climate Definitions

Insolation

Insolation is the amount of solar radiation a surface receives. It varies with season and latitude, influencing the angle at which sunlight arrives. In the northern Iberian Peninsula, sunshine is limited, increasing significantly towards the south.

Thermal Amplitude / Thermal Oscillation

Thermal amplitude, also known as thermal oscillation, is the difference between the maximum and minimum temperatures recorded in an area. This can refer to either the annual or daily temperature range. Both tend to increase inland due to the reduced mitigating effect of the sea on temperatures. In Spain, the temperature range is notably high across the two sub-plateaus and reduced along the coasts.

Anticyclone

An anticyclone is a high-pressure area surrounded by lower pressure. Winds within an anticyclone rotate clockwise in the Northern Hemisphere (counter-clockwise in the Southern Hemisphere). Anticyclones generally correspond to periods of stable weather conditions. Notable anticyclones affecting Spain include the Scandinavian Anticyclone and the Azores High.

Polar Front

The polar front is a weather front that separates cold polar air masses from warmer air masses originating from the south. It is typically located around 60 degrees north latitude. Storms associated with the polar front define the humid climate of the Cantabrian coast and, in certain seasons, especially in autumn, significantly affect much of the Iberian Peninsula.

Low-Pressure System (Borrasca)

A low-pressure system, also known as a barometric depression or borrasca, is an area where atmospheric pressure is below normal, leading to unstable weather. These systems typically move from west to east, bringing rainy and windy conditions. In Spain, low-pressure systems are more frequent in late autumn and winter.

Continentality

Continentality is a key factor defining climate. It refers to the effect of a region's remoteness from large bodies of water, which makes it difficult for moist air to reach these areas. Regions with high continentality typically experience an increase in thermal amplitude (temperature range) and a decrease in rainfall due to the absence of a moderating water body.

Atmospheric Pressure

Atmospheric pressure is the weight exerted by the air above a surface. It is considered a key factor in defining the boundary between high and low-pressure systems. Pressure generally decreases with increasing altitude. Not all areas at the same altitude have the same pressure, as hot air is lighter and exerts less pressure than cold air. Atmospheric pressure is measured with a barometer and is expressed in millibars (mb).

Barometer

A barometer is an instrument used to measure atmospheric pressure.

Isobars

Isobars are lines on a weather map connecting points of equal atmospheric pressure.

Annual Rainfall Regime

An annual rainfall regime describes the variations in rainfall patterns throughout the seasons in a given climate, influenced by various factors.

Thermal Regimes

Thermal regimes refer to the variations in temperature throughout the seasons in a climate, determined over different time scales: daily (day-night), monthly, or yearly.

Coastal Breezes (Sea and Land Breezes)

Coastal breezes are a type of local wind system caused by the differential heating and cooling rates of land and sea.

• During the day: The land heats up faster than the sea. Air above the land warms, becomes less dense, and rises. This rising air is replaced by cooler, moist air flowing in from the sea (a sea breeze).
• Overnight: The land cools faster than the sea. The air above the ocean remains warmer and rises. This rising air is replaced by cooler, drier air flowing from the land towards the sea (a land breeze).