Key Meteorological Factors and Climate Elements Explained

1. Solar Radiation and Cloudiness

Solar radiation is the amount of energy received by the Earth's surface. Cloudiness refers to the state of the atmosphere when the sky is covered by clouds.

2. Air Temperature and Thermal Variations

Air temperature is the degree of heat in the atmosphere, represented by isotherms—lines connecting points with the same temperature. The annual temperature range is the difference between the average temperatures of the warmest and coldest months.

Frosts occur when air temperatures drop to 0°C. They are categorized as:

• Irradiation frost: Caused by soil cooling the air in direct contact with it.
• Advection frost: Caused by the arrival of a very cold air mass.

3. Atmospheric Humidity, Fog, and Haze

Air humidity is the amount of water vapor present, resulting from evaporation. It depends on proximity to the sea and temperature.

Fog is the suspension of water droplets in the lower atmosphere, limiting visibility to less than 1 km. It occurs when moist air condenses. Types include:

• Irradiation fog: Caused by heat loss from the ground.
• Advection fog: Caused by warm, moist air moving over a cold surface, or cold air moving over a warmer, wetter surface.

Haze is an atmospheric phenomenon that reduces visibility due to the presence of fine dust particles in the lower layers of the atmosphere.

4. Barometric Pressure and Wind Systems

Barometric pressure depends on the characteristics of air masses. In Spain, high pressures dominate in winter and summer, while low pressures are more common in spring.

Winds are horizontal movements of air caused by pressure differences, flowing from high to low-pressure areas. Spain is primarily influenced by westerly winds.

5. Precipitation Patterns

Precipitation refers to water falling from clouds in liquid or solid form. It is represented on maps by isohyets and is caused by the elevation, cooling, and condensation of water vapor. Depending on the cause of rising air, precipitation is classified as orographic, convective, or frontal.

6. Evaporation, Evapotranspiration, and Aridity

Evaporation is the process by which water transforms into vapor at room temperature; the rate increases with higher temperatures. Evapotranspiration is the loss of moisture from the Earth's surface due to solar radiation and plant transpiration. It is measured as actual or potential evapotranspiration.

Aridity is the relationship between heat and humidity. It increases with higher temperatures and lower precipitation. Key indices include:

• Gaussen's Table: Measures monthly aridity. A month is considered arid when twice its mean temperature is greater than or equal to its total rainfall.
• Lautensach-Meyer Table: Determines general regional aridity based on the number of months with a water deficit (less than 30 mm of precipitation).

These indices define zones of humidity, semi-aridity (1–3 dry months), and extreme semi-aridity (7–11 arid months).