What’s the Story?

El Nino and La Nina The 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…

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.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 America Indo-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. thermocline 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 Nina The 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…

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 there have also been moderate El Nino events in , , and and on ejust recently at the end of your task is to find out about the climatic, environmental and economic impacts for the extreme El Nino event of 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 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 Environment al 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 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 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