What’s the Story?

El Nino and La NinaThe syllabus requires you to know:• The atmospheric-oceanic interactions

associated with El Nino Southern Oscillation (ENSO)

• The El Nino and El Nina phenomena and their climatic, environmental and economic effects

Starter:

Read and take some notes about El Nino and La Nina – check out the flooding in Oz…..http://www.bbc.co.uk/news/world-asia-21226178 http://www.bbc.co.uk/news/world-asia-20997139

• A disruption of ocean-atmosphere system in the tropical Pacific that has significant impacts for weather both within the Pacific and globally…

El Nino

Idealised atmospheric circulation of the Earth - the Hadley

Cells.

General circulation and wind belts

Air moves from areas of high to low pressure

The normal circulation in the Pacific Ocean

Oceans also have very specific currents which are predominantly driven by wind and temperatures

Ecuador

Peru

Australia

Indonesia

Figure 7z-1: This cross-section of the Pacific ocean, along the equator, illustrates the pattern of atmospheric circulation typically found at the equatorial Pacific. Note the position of the thermocline.

A cross section of a normal year

La Nina

Normal Conditions in the Pacific Ocean – West Pacific•Trade Winds blow towards the west across the tropical Pacific

•Warm surface water is pushed to the west so that the sea surface is approximately half a meter higher at Australia/Indonesia than at Ecuador/Peru and about 5 degrees Celsius warmer

•The warm surface waters heat the atmosphere and a low pressure area develops as warm air rises to form convectional uplift and rainfall in Australia/Indonesia South AmericaIndo-

Australia

Normal Conditions in the Pacific Ocean – East Pacific (1)•The thermocline (the boundary between the cold deep water and the warm upper layer) is shallower in the east Pacific and therefore the trade winds pull up cold water from below

•This causes an upwelling of cold water which is nutrient rich

•The nutrient rich waters allow high level of primary productivity (production of phytoplankton)

Normal Conditions in the Pacific Ocean – East Pacific (2)•This high level of primary productivity sustains diverse marine ecosystems and large stocks of fish

•The air sinks off the west coast of Ecuador/Peru and an area of high pressure develops to give dry stable conditions

So what happens during an El Nino

event?

Figure 7z-2: This cross-section of the Pacific ocean, along the equator, illustrates the pattern of atmospheric circulation that causes the formation of the El Nino. Note how position of the thermocline has changed from Figure 7z-1.

Cross section of an El Nino year.

El Nino Event – Pacific Ocean

•During an El Nino event the pressure systems and weather change•The trade winds weaken in the central and western Pacific and this causes the warm water in the west to travel eastwards •The thermocline deepens in the east and this reduces the efficiency of cold water upwelling•This affects the primary productivity

El Nino Event - Weather

•In the west (Australia/Indonesia) the absence of warm water to heat the atmosphere will lead to dry stable weather conditions (drought/wildfires)

•In the east (Ecuador/Peru) the warmer water will heat the atmosphere and lead to convectional uplift and unstable wet weather conditions (floods)

La Nina Event•As the influence of an El Nino event decreases and conditions return to normal occasionally a third weather condition develops – La Nina

•This is an exaggerated version of the normal conditions where so much warm water has traveled west that intensive rainfall creates flooding in Australia/Indonesia and intensive droughts occur in Ecuador/Peru – right now!

LA NINA AND EL NINO •What does the thermal image of the Pacific Ocean show about the distribution of heat?•Which image do you think is during an El Nino year?

Global Effects of ENSO(El Nino Southern Oscillation)

• The El Nino/La Nina events affect the weather around the world and is therefore a hazard (see your notes).

• Most scientists conclude that global warming is contributing to storms of greater magnitude, but that ENSO has an important impact on frequency.

• During an El Nino event there are less hurricanes in the Atlantic as there are unusually strong winds in the Atlantic which shear off the tops of clouds preventing the convection cells from forming.

• During a La Nina event there are more hurricanes in the Atlantic.

El Nino and La NinaThe syllabus requires you to know:• The atmospheric-oceanic interactions

associated with El Nino Southern Oscillation (ENSO)

• The El Nino and El Nina phenomena and their climatic, environmental and economic effects

Starter:

Read and take some notes about El Nino and La Nina – check out the flooding in Oz…..http

://www.bbc.co.uk/news/world-asia-21226178 http://www.bbc.co.uk/news/world-asia-20997139

Task

• Create a flow diagram explaining what is going on in the photo..

‘Explain El Nino and La Nina phenomena and their climatic, environmental and economic

effects.’

EL NINO AND LA NINA El Nino can happen on different scales of intensity. The last extreme El Nino event was in 1997-8. there have also been moderate El Nino events in 1990-95, 2002-3, 2004-5 and 2006-7 and on ejust recently at the end of 2012. your task is to find out about the climatic, environmental and economic impacts for the extreme El Nino event of 1997-1998 as well as one moderate El Nino event of your choice( less detail for the moderate one). Remember to state the relevance of the points you are making e.g. If you mention that country X’s crop Y failed – also mention that this is problematic because X% of their economy relies on agriculture and it accounts for X amount of their GDP. You also need to identify the environmental, climatic and economic effects of a La Nina event

Australia/Ecuador 2012-late 13

El Nino – extreme event 1997-1998

El Nino moderate event (____________)

La Nina event (___________)

Climatic effects

East Pacific. Loads of rain, torrential, landslides,

Drought in SEAsia and Oz, 15% of normal rainfall

Ecuador increased rain

Se temp in S Amercica up 6degrees

Ecuador june 2013 stark drought after previosu rainfall.

Oz heavy rainfall

Environmental effects

292 from flash floods Ecuador

Forest Fires in Oz

Duststorms, soil erosion

Lake Erie dried up

Heavy rain which led to a malaria epidemic in Africa and 30,000 cases of cholera in Peru alone.

Breeding cycles change due to reduction of krill

Malarisa outbreak in Africa and Cholera in Peru due to flooding

Oz huge flooding Mid 2013

Economic effects

13200 houses destroyed in Peru

Colobia fish income down 20%

Global fiannacial markets destablised (Food)

Cost of rebuilding afdter fires

During this time the cool water off the coast of Peru was replaced with warm water bringing rain to the desert and chaos to the fishing industry. These changes persisted for 12-18 months and for the people of Peru, this was

often a matter of life and death.

4.4 bn to rebuild and 2 bn in insurance costs in Austarlia 2012

Rainfall in Oz destroying crops