From the spec Today we will investigate – Drought – what is it (definition) and where does it occur? To investigate the causes and the links with the El Nino effect. To investigate the frequency of drought and whether human activities are affecting their frequency. Resource Text book page 13 – 15 Main skill Visual literacy – describing the explaining the global pattern of high risk drought regions.

TITLE: Drought and El Nino Aim: to understand drought (definition) and where it occurs To investigate the frequency of drought and whether human activities are affecting their frequency. Challenge:To investigate the links with the El Nino effect.

What is drought? Can you come up with a definition?

Drought is not the same as dry areas or deserts. There are many dry (arid) regions in the world. All regions of the world can go through a period of drought. Africa California U.K

How much below ‘normal’? 1) What is drought? Definition: A prolonged period of time of below normal rainfall. How long the time scale? (1 month? 6 months? 2 years?) How much below ‘normal’? 10% less? 50% less? https://www.youtube.com/watch?v=coeHw6QCxJ8

‘How much time is needed before it is a drought’? How much below normal’ does it have to be? A place that usually gets rain every week (e.g. south England) might declare a drought after 3 months of below normal rainfall. On the other hand, a place that rarely gets rain (e.g. parts of Africa or Australia) may not declare a drought until a few years of below normal rainfall.

When does a drought begin? Drought has a slow, creeping onset. It will only be recognised once the effects begin to be noticed e.g. dry ground, vegetation turning brown; low river levels, etc. A drought is difficult to detect until it has already happened!

2) Where does drought occur? What parts of the world have extreme or exceptional drought? Are there any surprises with this map?

2) Where does drought occur? Remember - all parts of the world can have drought. However, extreme droughts are NOT in the hot desert areas – these places are always dry (arid). The most extreme droughts are on the fringes of the hot deserts, where people may expect some seasonal rain, and then it doesn’t happen!

2) Where does drought occur? This map is different. It shows the regions of the world at risk of death from drought (see also Fig 29 page 15) Grade 6 Grade 8 Describe the distribution of drought high & medium death risk areas. Name regions and countries Explain the distribution of drought high & medium death risk areas. Describe the pattern. Give reasons why some places are more at risk of death. Try to make 3 specific points.

Regions of the world at risk of death from drought Grade 6 Grade 8 Describe the distribution of drought high & medium death risk areas. The regions of the world with the greatest risk of death from drought tend to be within the tropics and on the fringes of the hot deserts. Places such as NE Brazil, central and southern Africa, India, China and parts of SE Asia. Explain the distribution of drought high & medium death risk areas. See grade 6 description plus – - These regions are very poor EDCs and LIDCs. They cannot afford investment in infrastructures to combat drought e.g. large reservoirs, desalination plants. - Many people live in these regions, increasing the risk. - These regions usually have a seasonal rain pattern. If the rains fail, a drought will result.

3) What causes drought? Drought is associated with areas of high pressure . Air is descending, creating high pressure. As it descends it warms up, absorbing any moisture in the air. Clouds disappear. Rain is unlikely. TIF: High pressure areas tend to bring settled weather. When they get established they may persist for a long time, blocking low pressure areas from moving in and bringing rain.

Droughts are often linked to a weather event called El Nino. What causes drought? TIF. Drought and the El Nino effect. Droughts are often linked to a weather event called El Nino. https://www.youtube.com/watch?v=7FVZrw7bk1w

Normal weather and El Nino weather. Normal air circulation – wet weather in Indonesia and Australia (low pressure) , with a cool sea and dry conditions (high pressure) over Peru. El Nino – the pattern is reversed. Warm water near Peru causes low pressure and heavy rain. In contrast over Australia and Indonesia the air is descending (high pressure) causing no clouds and no rain. Drought is the outcome.

El Nino weather. Literally means – ‘little child’ Refers to ‘Christ child’. So called because it occurred around December and the term was used by Peruvian fishermen who noticed sea temperatures were unusually warm and fish stocks were consequently low. The El Nino effect tends to occur on 3-7 year intervals. Why? – difficult to explain! How does El Nino affect other parts of the world beyond the Pacific? El Nino gets blamed for a lot of unusual weather. The connections are not always easy to see.

How can human activities make drought worse? 4) How can human activities make drought worse? See fig 27 page 14 How can human activities make drought worse?

Droughts will vary in their intensity and duration 5) The frequency of drought. Droughts will vary in their intensity and duration

The frequency and impact of drought is likely to increase in the future. There are more people on the planet Each person is using more water Climate change may be leading to more intense but irregular rainfall. (the evidence for this is debated)

Review: with your neighbour. Drought is …… You might not know there is a drought until …. The risk of death from drought is highest in … because … Droughts are likely to become more frequent because ...

Homework: GCSE workbook pages 9&10 El Nino & Drought