Cheat Sheet: Pressure Winds Storms And Cyclones

1. Pressure

1.1 Characteristics

1.2 Liquids and Structural Responses

• Liquid pressure at a point depends only on the height of the liquid column above that point
• Liquids exert pressure on container walls in all directions (downwards and sideways)
• Dams are built broad at the base to resist larger horizontal water pressure at greater depth
• Placing water storage tanks at height increases pressure in household pipes due to greater water column height

2. Atmospheric Pressure, Winds, and Pressure Effects

2.1 Formation of Winds

2.2 High-Speed Winds and Pressure Effects

• High-speed wind creates localized low-pressure zones where air flows rapidly
• Higher surrounding pressure pushes toward low-pressure zones, producing net forces on objects
• Low pressure above a roof combined with higher indoor pressure can lift the roof upward
• Keeping doors and windows open during storms helps equalize inside and outside pressure

3. Storms, Thunderstorms, and Lightning

3.1 Formation of Storms

1. Sun heats land; air above land becomes warm and moist
2. Warm, moist air rises, creating a low-pressure area
3. Cooler air from surrounding high-pressure areas moves in and rises after heating
4. Rising air cools; moisture condenses to form water droplets (clouds)
5. Droplets join and fall as rain, hail, or snow
6. Strong moving air with heavy precipitation constitutes a storm

3.2 Thunderstorms and Lightning

3.2.1 Charging and Lightning Process

1. Updrafts and downdrafts carry water droplets to heights where ice forms
2. Rubbing between ice particles and water droplets electrically charges them
3. Lighter positively charged particles move to cloud top; heavier negatively charged particles gather at cloud bottom
4. Charge separation induces positive charge on ground and nearby objects when cloud base approaches ground
5. When air's insulating resistance breaks down, sudden flow of charges produces lightning
6. Lightning can occur within a cloud, between clouds, or between a cloud and the ground
7. Lightning heats air rapidly; expanding air produces thunder
8. A storm with thunder and lightning is a thunderstorm

3.3 Regional Names and Lightning Protection

3.4 Safety During Lightning

• Stay away from tall objects such as trees and poles
• Find a low, open area and crouch; do not lie flat on the ground
• Do not use umbrellas with a metallic rod
• If in water, get out immediately
• Remain inside a car or bus for comparative safety

3.5 Lightning Conductor

4. Cyclone

4.1 Definition

4.2 Formation of Cyclones

1. Warm ocean water heats the air above, making it moist and light
2. Warm, moist air rises, leaving a low-pressure area below
3. Rising air cools and water vapour condenses to form rain; condensation releases heat and warms air further
4. More surrounding air rushes in, rises, and the rotation of the Earth causes the moving air to spin
5. A rapidly spinning system of clouds, winds, and rain forms with a calm eye at the center and high-speed winds and heavy rain around it
6. On landfall the cyclone weakens as it loses its source of warm, moist air but can still cause massive destruction

4.3 Why Cyclones Are Dangerous

• Storm surge: strong winds push ocean water toward land creating a high wall of water 3-12 meters tall
• Heavy rainfall causes rivers to overflow, producing floods and landslides
• Seawater can contaminate drinking water and reduce soil fertility
• Fallen trees and debris can block roads and cause long-lasting power outages

4.4 Staying Safe During a Cyclone

• Stay informed via radio and television for weather warnings from the IMD
• Keep an emergency kit containing food, water, medicines, flashlight, and batteries
• Move to a nearby cyclone shelter or safe building when advised
• Satellite monitoring helps track and predict cyclones
• Authorities coordinate national and international responses to cyclone disasters

5. Key Terms to Remember