Answer :
**Why It Rains Over Mountains:**
Rainfall over mountains is often explained by a process known as orographic lift. Here's how it works:
1. **Wind and Moisture:** Moist air masses are carried by the wind towards mountain ranges.
2. **Forced Ascent:** As the air mass encounters the mountains, it is forced to rise over them because the terrain acts as a barrier.
3. **Cooling and Condensation:** As the air rises, it cools down. Cooler air can hold less moisture than warm air, leading to condensation.
4. **Cloud Formation:** The condensed moisture forms clouds.
5. **Precipitation:** When the moisture in the clouds becomes too heavy, it falls as precipitation – rain or snow, depending on the temperature.
This process is why areas on the windward side of mountains often receive more rainfall than areas on the leeward side, which can be in the rain shadow and receive significantly less precipitation.
**Why We Get Downpours in Summer in the UK:**
The UK's summer downpours are typically due to convective rain. This happens when the land heats up due to the stronger summer sun, warming the air above it. The process includes:
1. **Surface Heating:** During summer, the sun heats the Earth's surface more intensely.
2. **Thermal Updrafts:** This heat causes the air close to the ground to warm up and become less dense, creating updrafts as the warmer air rises.
3. **Moisture and Instability:** As this warm air rises, it carries moisture from the surface with it. The atmosphere can become unstable, especially if the upper atmosphere is cooler.
4. **Condensation and Cloud Formation:** As the air rises, it cools and the moisture condenses into cloud droplets, forming cumulus clouds. These clouds can develop into cumulonimbus clouds if conditions are right.
5. **Heavy Rainfall:** Cumulonimbus clouds are responsible for heavy showers and thunderstorms. The UK is particularly prone to this type of rainfall in the summer due to the island's maritime climate and the convergence of different air masses, including warm air from the tropics and cooler air from the polar regions.
These factors contribute to the sudden and heavy downpours characteristic of British summers.
