El Nino and La Nina
El Niño and La Niña are weather phenomena that occur as a result of interaction between
ocean temperatures and global air circulation. They take place every 6-8 years.
Tropical easterly winds that blow towards LP on equator have an important influence on
Pacific ocean temperatures
- Strong tropical easterlies: water in Eastern Pacific is cold
- Weak tropical easterlies: water in Eastern Pacific is warm
Normal processes
Tropical easterlies blow across Pacific – drag surface water westwards
↓
Upwelling of cold water in Eastern Pacific – nutrients for fish
↓
Cold Peru Humboldt current – flows north along Peruvian coast on west coast of
South America
↓
Cold water is dragged west along equator – heated by tropical conditions – 6°C
warmer than Eastern Pacific
↓
Brings rain to Indonesia and Australia – warm air rises, cools, condenses – LP
↓
Dry on West coast of Peru – subsiding
, El Nino
The temperature of surface waters in eastern Pacific warming
• Occurs at Christmas time every 2-7 years
• Fishing off South America’s west coast is poor – affects economy
• Affects people: when do they plant crops, flooding, drought
Tropical Easterlies weaken
↓
Upwelling of cold water ceases – no more nutrients for fish
↓
Area of warmer water that is usually over western Pacific becomes cooler
↓
Warmer water is displaced eastwards to central Pacific
↓
Normally cold waters of eastern Pacific along South American coast is warmer by 2-
8°C – bad for fishing industry
↓
Normal circulation is altered as a result of changes in Pacific
↓
Convection and rain occurs in eastern and central Pacific
↓
Australia and southern Africa experience drought and cooler conditions – air is
descending
El Niño and La Niña are weather phenomena that occur as a result of interaction between
ocean temperatures and global air circulation. They take place every 6-8 years.
Tropical easterly winds that blow towards LP on equator have an important influence on
Pacific ocean temperatures
- Strong tropical easterlies: water in Eastern Pacific is cold
- Weak tropical easterlies: water in Eastern Pacific is warm
Normal processes
Tropical easterlies blow across Pacific – drag surface water westwards
↓
Upwelling of cold water in Eastern Pacific – nutrients for fish
↓
Cold Peru Humboldt current – flows north along Peruvian coast on west coast of
South America
↓
Cold water is dragged west along equator – heated by tropical conditions – 6°C
warmer than Eastern Pacific
↓
Brings rain to Indonesia and Australia – warm air rises, cools, condenses – LP
↓
Dry on West coast of Peru – subsiding
, El Nino
The temperature of surface waters in eastern Pacific warming
• Occurs at Christmas time every 2-7 years
• Fishing off South America’s west coast is poor – affects economy
• Affects people: when do they plant crops, flooding, drought
Tropical Easterlies weaken
↓
Upwelling of cold water ceases – no more nutrients for fish
↓
Area of warmer water that is usually over western Pacific becomes cooler
↓
Warmer water is displaced eastwards to central Pacific
↓
Normally cold waters of eastern Pacific along South American coast is warmer by 2-
8°C – bad for fishing industry
↓
Normal circulation is altered as a result of changes in Pacific
↓
Convection and rain occurs in eastern and central Pacific
↓
Australia and southern Africa experience drought and cooler conditions – air is
descending
