El Nino and Natural Hazards Flashcards
What is El Nino?
Climate pattern- unusual warming of surface waters along the tropical west coast of South America.
What does El Nino have an impact on?
Ocean temperatures
Speed and strength of ocean currents
Health of coastal fisheries
Local weather from Australia to South America.
What happens during El Nino years?
Pressure systems and weather patterns reverse.
Warmer waters develop in the eastern Pacific- due to trade winds collapsing so theres low pressure over sea.
Warm, moist air rises, creating heavy rainfall over the eastern Pacific.
The air circulates west in the upper atmosphere.
Around Northern Australia and Indonesia the descending air gives drier conditions than usual and can cause drought.
What is La Nina?
La Nina is where the ‘normal’ situation intensifies.
What happens during a La Nina event?
Low pressure over the western Pacific becomes even lower, and high pressure over the eastern Pacific even higher.
Rainfall increases over South-East Asia, and South America suffers drought.
Trade winds become stronger due to the increased difference in pressure between the two areas.
La Nina can occur just before, or just after, El Nino.
What have the most extreme results of an El Nino been?
Flooding from Ecuador to the Gulf of Mexico.
Massive marine life die offs in the Pacific.
Hurricanes in Tahiti and Hawaii.
Concurrent droughts in many other parts of the world from Southern India to Australia to Central America.
How is La Nina beneficial for marine organisms?
During La Nina, currents bring nutrients up from the deep water, providing feast, rather than famine, for marine organisms.
How is Global Warming Related to El Nino and La Nina?
Some scientists believe that the increased intensity and frequency- now every two to three years- of El Nino and La Nina events in recent decades is due to warmer ocean temperatures resulting from global warming. In a 1998 reports, scientists explained that higher global temperatures might be increasing evaporation from land and adding moisture to the air, thus intensifying the storms and floods associated with El Nino.
El Nino: normal year
The trade winds move warm surface water towards the western Pacific
Cold water wells up along the west coast of South America (near Peru)
Upwelling important for fish stocks in Peru
