Understanding Climate and Weather Phenomena
Climate and Weather Phenomena
Understanding Key Concepts
Dryness
Dryness occurs when evapotranspiration exceeds precipitation, meaning the land loses more water to the atmosphere than it receives. This can happen even without a complete absence of rain.
Mediterranean Climate
A temperate climate characterized by hot, dry summers with low rainfall (where evapotranspiration surpasses precipitation) and mild, dry winters. Rainfall is scarce and primarily occurs in spring and autumn. Average annual temperatures range from 16 to 18°C, with abundant sunshine and clear days.
Climate
The set of average annual meteorological parameters that characterize the weather in a specific location over an extended period (20-30 years). It varies depending on latitude, altitude, and continentality.
Climograph
A graphical representation of the average monthly temperature and precipitation over a long period (20-30 years). It provides a simplified visualization of a region’s climate.
Sustainable Development
Activity that meets the needs of the present without compromising the ability of future generations to meet their own needs. This involves exploiting ecosystems at a rate lower than their carrying capacity, with a renewal rate exceeding the exploitation rate and waste emission below the assimilative capacity.
Foehn Effect
Occurs on the leeward side of mountain ridges. After orographic lifting and precipitation, the descending air mass, devoid of moisture and warmed adiabatically, not only brings no rainfall but also absorbs soil moisture, causing dryness.
Greenhouse Effect
A beneficial natural process that maintains Earth’s average temperature at approximately 15°C. Atmospheric gases are transparent to visible solar radiation, but some (CO2, CH4) absorb infrared radiation emitted by the warmed surface, contributing to global warming.
Fronts
Contact zones between two moving air masses with different temperatures and humidity. These air masses behave as isolated systems and do not mix. At the front, the warmer air rises, potentially leading to condensation, cloud formation, and precipitation. Fronts can be cold, warm, or occluded.
Cold Drop (Gota Fría)
A phenomenon occurring in late summer, typically in Spain’s eastern region. It involves the entry of a cold air mass aloft from the subpolar region interacting with warmer, moist air from the Mediterranean, heated intensely during summer. This interaction causes heavy rainfall, sometimes hail, and frequent flooding.
Drought
A decrease in precipitation over a specific area and period. It poses a climate risk, reducing agricultural and livestock production, leading to famines, impacting water resources, and increasing the risk of forest fires.
Cloud Formation and Precipitation
Precipitation happens when water vapor condenses around condensation nuclei, forming droplets that fall to the surface as rain (liquid) or snow/sleet (solid). Dew and frost occur when condensation happens on surface plants and rocks. Cloud formation precedes precipitation and occurs in three ways:
- Thermal Convection: In unstable atmospheric conditions, rising warm, moist air reaches the condensation level, forming cumulus clouds. With sufficient heat and moisture, these can grow into towering cumulonimbus clouds, producing rain through the collision and coalescence of water droplets.
- Orographic Ascent: Moist air forced upwards by a mountain reaches its condensation level, forming clouds and precipitation on the windward side. The descending air on the leeward side becomes warmer and drier, creating a rain shadow effect.
- Frontal Lifting: Occurs at the boundary (front) between two air masses with different temperatures and humidity. The warmer air rises over the colder air, leading to cloud formation and frontal precipitation.
Types of Fronts
- Cold Front: A cold air mass moves faster than a warm air mass, forcing the warm air upwards, resulting in rapid condensation and heavy precipitation.
- Warm Front: A warm air mass moves over a cold air mass, causing gradual condensation and widespread, lighter precipitation.
- Occluded Front: A cold front overtakes a warm front, lifting the warm air completely off the ground, leading to a combination of precipitation patterns.
Types of Precipitation
- Rain: Liquid precipitation. Torrential rain exceeds 200 L/m² in 24 hours. Storms involve intense convection currents and electrical activity, typically lasting 30-60 minutes, common in small areas during summer.
- Snow: At low temperatures, water vapor condenses into ice crystals, forming snowflakes. If temperatures are high enough near the ground, snow melts into rain.
- Hail: Formed in spring or summer storms when ice crystals are repeatedly lifted and lowered within the cloud, accumulating layers of ice. Large hailstones pose a risk to agriculture.