Climatology: Elements, Factors and Types of Climate

Elements of Climate

Insolation

• Definition: quantity of solar radiation received by Earth’s surface.
• Controls the energy budget that drives temperature, evaporation, cloud formation, and atmospheric circulation.

Cloudiness (Nubosidad)

• Amount of cloud cover observed in the sky (fully overcast ↔ clear).
• Directly modulates insolation by reflecting (albedo) and absorbing radiation.
• High cloudiness → softer diurnal thermal oscillation; low cloudiness → larger day-night contrast.

Temperature

• Expresses the degree of heat contained in the air.
• Key descriptive qualifiers that appear in Spanish climatology:
  • suaves (mild),
  • extremas (extreme),
  • altas (high),
  • bajas (low / cold).
• Fundamental indices:
  • Mean annual temperature: $T<em>{mean}=\frac{\sum</em>{i=1}^{12}T_i}{12}$
  • Annual thermal amplitude: $\Delta T = T<em>{max\,(year)}-T</em>{min\,(year)}$
• Spatial rules within Iberia:
  • Maritime facade → reduced amplitude, milder winters/summers.
  • Interior plateaus → increased amplitude, hotter summers, colder winters.
  • North–south gradient: temperatures rise southward.

Irradiation & Night Cooling

• High daytime insolation followed by rapid nocturnal radiative loss favours strong cooling (esp. in clear, calm situations).

Frosts (Heladas)

• Occur when air temperature falls below $0\,^{\circ}C$.
• Two mechanisms:
  • Radiation frost: intense ground cooling under clear skies & calm winds.
  • Advection frost: arrival of a very cold air mass.

Humidity of the Air

• Quantity of water vapour present.
• Controls formation of:
  • Fog (niebla): suspension of tiny water droplets that reduce visibility. Radiation & advection varieties mirror the frost mechanisms.
  • Calima: dry dust-laden haze, typical of subsiding, very dry air, greatly reducing visibility.

Atmospheric Pressure

• Weight of the air column per unit surface area.
• High-pressure centre (anticyclone): $\uparrow$ pressure; sinking, diverging air → stable, clear weather.
• Low-pressure centre (depression/borrasca): $\downarrow$ pressure; rising, converging air → clouds & precipitation.

Wind

• Horizontal displacement of air from high toward low pressure.
• Local example: Levante (easterly wind along the Strait of Gibraltar).

Precipitation

• General definition: water (liquid or solid) falling from clouds due to lifting, cooling & condensation.
• Orographic: air mass ascends a mountain slope.
• Convective: intense surface heating triggers vertical motion.
• Frontal: warm and cold air masses meet along a front.

Evaporation

• Process by which water is transformed into vapour; tightly linked to temperature and humidity balance.

Climatic Factors (Conditioning Agents)

Latitude

• Iberian Peninsula lies mid-latitudes of the Northern Hemisphere ⇒ classical alternation of four seasons.
• Practically, two contrasted seasons dominate (summer & winter) with two transitional ones (spring & autumn).

Maritime Influence

• Marked along coasts (temperature moderation & moisture supply).
• Very limited in the interior due to mountain barriers that run parallel to the shoreline.

Relief

• Orientation & disposition of ranges condition climate:
  • Parallel coastal chains block humid maritime air.
  • Windward slopes → enhanced orographic rainfall.
  • Leeward (rain-shadow) slopes → drier, warmer by adiabatic warming.
• Altitude effect: temperature decreases with height (≈ $0.6\,^{\circ}C/100\,m$); precipitation generally increases and may fall as snow above $\sim1000\,m$.

Jet Stream (Upper-level Circulation)

• High-speed westerly current at ≈ $9\,km$ altitude.
• Winter position displaced southward; summer displaced northward.
• Controls the succession of highs/lows at the surface; meanders create ridges (surface anticyclones) and troughs (surface lows).

Surface Circulation: Centres of Action, Air Masses & Fronts

• Formation:
  • Cooling → anticyclone (cold-core high).
  • Heating → depression (warm-core low).
• Principal air masses affecting Spain:
  • Polar/Arctic maritime & continental (cold).
  • Tropical maritime & continental (warm).
• Polar front separates tropical and polar air.
• Front types:
  • Warm front: warm air glides up over retreating cold air.
  • Cold front: cold air undercuts & uplifts warm air.
  • Occluded front: cold front overtakes warm front.

Types of Climate on Spanish Territory

1. Oceanic (Atlantic) Climate

• Spatial domain: Cantabrian & Galician coasts (northern fringe).
• Precipitation: very abundant (>$1000\,mm/yr$), evenly distributed; no summer drought.
• Temperature: mild year-round; low thermal amplitude; winters cool/fresh, summers also fresh.
• Key driver: continuous passage of polar-front depressions & immediate sea proximity.
• Oceanic of transition: situated just inland; rainfall lower, amplitude a bit higher.

2. Mediterranean Climate (general family trait: pronounced summer drought)

2.a. Coastal Mediterranean

• Area: Balearic Islands, Valencian & Catalan coast (except Almería sector).
• $T_{mean}$ rises north→south, typically $14–18\,^{\circ}C$.
• Moderate thermal amplitude; winters mild, summers hot.
• Precipitation: scarce (≈ $300–600\,mm/yr$), highly irregular, maxima in autumn & spring; marked summer aridity.
• Local nuances:
  • Catalan sector: slightly higher rainfall & lower summer heat.
  • Andalusian sector: hottest summer values of the peninsula.

2.b. Interior (Continentalised) Mediterranean

• Area: both Mesetas, Ebro depression, interior Andalusia & Extremadura.
• Very high annual thermal range: cold winters, hot summers.
• Overall $T_{mean}$ lower than coast.
• Precipitation: scarce/irregular; bulk in spring & autumn; summer drought accentuated.
  • Sub-meseta Norte: cold winters, relatively cool summers.
  • Sub-meseta Sur & Ebro basin: winters less cold, summers very hot.
  • Interior Andalusia/Extremadura: mild winters, torrid summers.

2.c. Dry Mediterranean / Sub-desert (SE Arid Belt)

• Core: Almería-Murcia sector; enclaves in the Ebro valley & eastern Zamora.
• Annual rainfall extremely low (often <250\,mm).
• Drivers: shielding from Atlantic storms + prevailing subsidence.
• Thermal character:
  • Coastal strip: warm all year, intense summer heat.
  • Interior pockets: cold winter nights, hot summer days.

3. Mountain Climate

• Defined for terrains above $\sim1000\,m$ a.s.l.
• Temperature: sharp decline with height; short cool summers, long cold winters.
• Precipitation: plentiful, much of it as snow.
• Local variability tied to slope orientation and valley-basin topography.

4. Canary Islands Climate

• Geographic setting: subtropical latitude, open ocean.
• Dominant controls: NE trade winds + Azores anticyclone.
• Temperature: warm throughout the year, minimal annual range.
• Precipitation: scarce in lowlands; strong vertical (altitudinal) contrasts.
  • Low zones: xerophytic shrubland.
  • Mid-altitude, windward slopes: laurisilva (humid evergreen cloud forest) sustained by trade-wind orographic lifting.
  • High mountain: open broom & alpine shrub.
• Frequent temperature inversion traps clouds between $600–1500\,m$, reinforcing ecological stratification.

Vegetation & Human Relevance (Cross-cutting)

• Oceanic climate → deciduous broadleaf forests (oak, beech).
• Mediterranean → evergreen sclerophyllous woodland (holm/ cork oak), shrubland (maquis, garrigue) adapted to summer drought.
• Dry Mediterranean → steppe, esparto grass, halophytic communities.
• Mountain → altitudinal belts: montane conifer/deciduous, sub-alpine shrub, alpine meadow.
• Canary Islands → endemic laurel forest, dragon-tree, cardonal-tabaibal (cactus-like) assemblages.
• Agricultural implications: water management crucial across Mediterranean & sub-desert zones; oceanic north suitable for pasture & dairy.

Summary Equations & Numbers Mentioned

• $T_{mean}=\frac{\text{Sum of monthly temperatures}}{12}$
• $\Delta T=T<em>{hottest\,month}-T</em>{coldest\,month}$ (annual thermal amplitude).
• Standard vertical temperature lapse rate: $\approx 0.6^{\circ}C/100\,m$.
• Threshold for frost: T<0^{\circ}C.
• Orographically induced uplift enhances precipitation, esp. windward slopes.