# Turbulence

> Understand the different types of turbulence in aviation: convective, mechanical, wind shear, and wake turbulence for EASA ATPL meteorology exams.

- **Subject:** 050 — Meteorology
- **Section:** 050-02 — Wind
- **Topic code:** 050-02-06
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/meteorology/wind/turbulence/

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Turbulence is the irregular and violent movement of air that causes the aircraft to shake.

## Types of Turbulence

### 1. Convective Turbulence (Thermal)
*   **Cause:** Uneven heating of the Earth's surface generating updrafts and downdrafts.
*   **Associated with:** Vertically developed clouds (**Cumulus** and Cumulonimbus).
*   **Critical time:** Early afternoon (when solar heating is maximum).
*   **Location:** Below cumulus clouds (rising air) and inside them.

### 2. Mechanical Turbulence (Frictional)
*   **Cause:** Physical obstructions to wind flow (buildings, trees, hills).
*   **Location:** Friction layer (up to 2000-3000 ft).
*   **Factors:**
    *   Wind speed (generally > 20 kt).
    *   Terrain roughness.
    *   Air stability.

### 3. Orographic Turbulence (Mountain Waves)
*   See previous section ([050-02-05](../mountain-waves-standing-waves-lee-waves/en/page.md)).
*   The most dangerous zone is the **Rotor**, on the leeward side of the mountain.

### 4. Clear Air Turbulence (CAT)
*   **Definition:** Severe turbulence in cloudless air (or outside convective clouds), generally at high altitude (> 20,000 ft).
*   **Cause:** Wind shear associated with **Jet Streams**.
*   **Detection:**
    *   **Invisible** to weather radar and satellites (no water/ice particles to reflect the signal).
    *   **Only reliable source:** Reports from other pilots (**AIREPs** / PIREPs).

## Wind Shear
It is a sudden change in wind direction and/or speed over a short distance (vertical or horizontal). It can occur at any level, but is critical at low altitude during takeoffs and landings.

## Gusts
Sudden and brief increases in wind speed.
*   Reported when the speed exceeds the mean wind by at least **10 kt**.
*   Typical duration: a few seconds (average of 3 seconds).

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Free study notes from pilotsyllabus.com. Not a substitute for training at an approved ATO.