# Climatic zones

> Overview of the world climatic zones and their impact on global aviation operations.

- **Subject:** 050 — Meteorology
- **Section:** 050-08 — Climatology
- **Topic code:** 050-08-01
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/meteorology/climatology/climatic-zones/

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Climatology studies long-term weather patterns. One of the most widely used classifications is the **Köppen** system, which divides the world's climates into five main groups based on temperature and precipitation.

![Köppen Climate Classification Map](https://upload.wikimedia.org/wikipedia/commons/3/32/K%C3%B6ppen-Geiger_Climate_Classification_Map_%281980%E2%80%932016%29_no_borders.png)
*Köppen-Geiger Climate Classification global map.*

## Köppen Climate Classification

### Class A: Tropical Rain Climate
*   **Location**: 0° - 10° N/S (Equatorial regions).
*   **Characteristics**:
    *   Mean temperature of the coldest month **> 18°C**.
    *   Mean monthly precipitation **> 60 mm**.
    *   No dry season.
    *   High relative humidity (~80%).
    *   High freezing level (~15,000 ft).
*   **Examples**: Amazon Rainforest (Brazil), Congo Basin.

### Class B: Dry Climate
*   **Location**: 20° - 35° N/S (Subtropical high-pressure belts).
*   **Characteristics**:
    *   Evaporation and transpiration exceed precipitation.
    *   No permanent watercourses.
    *   Influenced by subtropical anticyclones.
*   **Examples**: Sahara Desert, Kalahari Desert.

### Class C: Mid-latitude / Warm Temperate Climate
*   **Location**: 40° - 70° N/S.
*   **Characteristics**:
    *   Defined summer and winter seasons.
    *   Mean temperature of the coldest month between **-3°C and 18°C**.
*   **Examples**: Northwest Europe, New Zealand, Southeast USA.

### Class D: Sub-arctic or Boreal Climate
*   **Location**: 50°N - 70°N (Northern Hemisphere only, large landmasses).
*   **Characteristics**:
    *   Mean temperature of the warmest month **> 10°C**.
    *   Mean temperature of the coldest month **< -3°C**.
*   **Examples**: Northern Eurasia, Canada.

### Class E: Polar or Snow Climate
*   **Location**: > 70° N/S.
*   **Characteristics**:
    *   Mean temperature of the warmest month **< 10°C**.
    *   Dry and anticyclonic winters.
    *   Permafrost soil.
*   **Examples**: Greenland, Antarctica.

## Transitional Climatic Zones

Between the main zones, there are transition areas with mixed characteristics:

### Tropical Transition Climate (Savanna)
*   **Location**: 10° - 20° N/S.
*   **Characteristics**:
    *   **Winter**: Warm and dry (Trade Winds).
    *   **Summer**: Warm and wet (Equatorial rains).
*   **Examples**: Northwest Africa, Ghana.

### Temperate Transition Climate (Mediterranean)
*   **Location**: 35° - 40° N/S.
*   **Characteristics**:
    *   **Winter**: Cool and wet (frontal depressions).
    *   **Summer**: Hot and dry (subtropical anticyclonic influence).
*   **Examples**: Mediterranean Basin, California, Central Chile.

## Global Circulation and Winds

Global climate is determined by latitude, air masses, heat exchange from ocean currents, and mountain barriers.

### Trade Winds
Persistent winds blowing from the subtropical high-pressure belts towards the Intertropical Convergence Zone (ITCZ).
*   **Northern Hemisphere**: Northeast Trades (NE Trades).
*   **Southern Hemisphere**: Southeast Trades (SE Trades).
*   In summer, over the oceans, they usually bring fair weather with cumulus or stratocumulus (Trade Wind inversion).

### Monsoons
Seasonal wind systems caused by thermal differences between large landmasses and the ocean.

1.  **NE Monsoon (Asian Winter)**:
    *   Blows from the **Siberian High**.
    *   **Cool and dry** air.
    *   Brings clear weather to India, Burma, and Thailand.

2.  **SW Monsoon (Asian Summer)**:
    *   Produced by SE Trades crossing the equator and turning SW.
    *   **Warm and very moist** air.
    *   Brings clouds of vertical development (Cu, Cb), heavy thunderstorms, and severe turbulence.
    *   Affects India, Sri Lanka, Burma, and the West African coast.

### ITCZ Movement
The Intertropical Convergence Zone shifts with the sun:
*   **NH Summer**: Shifts North.
*   **NH Winter**: Shifts South.
This movement causes the seasonal displacement of circulation cells and rain belts.

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