WEBVTT 00:00:00.500 --> 00:00:03.975 Welcome to GCSE A Q A Geography revision. 00:00:04.125 --> 00:00:06.407 Topic G 3: Weather hazards. 00:00:06.557 --> 00:00:11.411 Use your school’s selected case studies if they differ from these revision examples. 00:00:14.067 --> 00:00:17.063 The Sun heats the equator more strongly than the poles. 00:00:17.213 --> 00:00:22.919 This uneven heating drives a global circulation system that transfers heat through the atmosphere. 00:00:25.600 --> 00:00:29.604 Near the equator, warm moist air rises, creating low pressure. 00:00:29.754 --> 00:00:35.236 As air rises it cools; water vapour condenses into clouds and frequent heavy rain. 00:00:37.900 --> 00:00:43.359 Air moves towards higher latitudes at altitude and sinks around 30 degrees north and south. 00:00:43.509 --> 00:00:50.762 Descending air warms and becomes relatively dry, producing high pressure and helping explain subtropical desert belts. 00:00:53.433 --> 00:00:57.444 The Hadley cells operate between the equator and about 30 degrees, 00:00:57.594 --> 00:01:01.370 the Ferrel cells between about 30 degrees and 60 degrees, 00:01:01.520 --> 00:01:04.931 and the Polar cells between about 60 degrees and the poles. 00:01:05.081 --> 00:01:09.584 These are a simplified average model; their positions change with seasons. 00:01:09.734 --> 00:01:12.207 Simplified atmospheric pressure belts. 00:01:12.357 --> 00:01:15.765 Approximate average positions; belts shift seasonally. 00:01:15.915 --> 00:01:20.385 The model links rising air with low pressure and sinking air with high pressure. 00:01:25.067 --> 00:01:31.860 Around 60 degrees, warmer and colder air meet and air tends to rise, giving low pressure and changeable weather. 00:01:32.010 --> 00:01:35.536 At the poles, cold dense air sinks and creates high pressure. 00:01:38.200 --> 00:01:43.756 Surface winds flow broadly from high to low pressure and are deflected by Earth's rotation. 00:01:43.906 --> 00:01:51.809 Trade winds blow towards the equator, prevailing westerlies affect mid-latitudes, and polar easterlies flow from polar high pressure. 00:01:54.467 --> 00:02:01.389 Tropical storms form over warm tropical oceans, usually between about 5 degrees and 30 degrees north and south. 00:02:01.539 --> 00:02:09.101 They are called hurricanes in the Atlantic and northeast Pacific, typhoons in the northwest Pacific, and cyclones in other basins. 00:02:11.767 --> 00:02:14.199 Storm formation needs warm water, 00:02:14.349 --> 00:02:19.095 typically at least about 26.5 degrees Celsius through a sufficient depth, 00:02:19.245 --> 00:02:20.823 abundant moisture, 00:02:20.973 --> 00:02:27.031 a starting disturbance and low vertical wind shear (little change in wind speed or direction with height). 00:02:29.700 --> 00:02:32.449 Warm seawater supplies heat and water vapour. 00:02:32.599 --> 00:02:40.277 Warm moist air rises and condenses; condensation releases heat, encouraging more rising air and lowering surface pressure. 00:02:42.933 --> 00:02:45.546 More air flows into the low-pressure centre. 00:02:45.696 --> 00:02:50.943 Earth's rotation makes the system rotate, and thunderstorms organise around the centre. 00:02:51.093 --> 00:02:56.041 Rotation is too weak at the equator for tropical cyclones normally to form there. 00:02:58.700 --> 00:03:02.787 The eye is a relatively calm central area with descending air. 00:03:02.937 --> 00:03:09.367 The eyewall around it contains the strongest winds and intense rain; spiral rainbands extend farther out. 00:03:09.517 --> 00:03:10.914 Eye and eyewall. 00:03:11.064 --> 00:03:13.539 The central eye is relatively calm. 00:03:13.689 --> 00:03:18.521 Strong upward motion occurs in the surrounding eyewall; the sketch is not to scale. 00:03:23.200 --> 00:03:29.001 A storm strengthens while it has a supply of warm moist air and favourable atmospheric conditions. 00:03:29.151 --> 00:03:36.093 It weakens over land, cooler water or stronger wind shear because its energy supply or structure is disrupted. 00:03:38.767 --> 00:03:46.371 A storm surge is a rise in sea level mainly caused by winds pushing seawater towards land, with low pressure also contributing. 00:03:46.521 --> 00:03:50.821 Surge, high tide and waves together can cause severe coastal flooding. 00:03:53.500 --> 00:03:59.003 Primary effects include wind damage, storm-surge flooding and river flooding from heavy rain. 00:03:59.153 --> 00:04:02.745 Deaths, injuries and damage to buildings can occur directly. 00:04:05.400 --> 00:04:12.779 Secondary effects include contaminated water, disease risk, disrupted transport, loss of income and food shortages. 00:04:12.929 --> 00:04:17.911 Flooded farmland or damaged fishing boats can affect livelihoods long after the storm. 00:04:20.567 --> 00:04:27.232 Immediate responses include evacuation, rescue, emergency shelter, medical care and food and water. 00:04:27.382 --> 00:04:33.631 Long-term responses include restoring livelihoods, rebuilding homes and strengthening coastal protection. 00:04:36.300 --> 00:04:41.441 Satellites, ocean buoys, radar and aircraft observations help monitor storms. 00:04:41.591 --> 00:04:47.818 Computer models predict possible tracks and intensity, but forecasts change as new information arrives. 00:04:50.500 --> 00:04:54.780 Protection includes storm shelters, strong roofs and coastal defences. 00:04:54.930 --> 00:05:01.809 Planning includes warnings, evacuation routes, practice drills and keeping new buildings away from areas at highest risk. 00:05:04.467 --> 00:05:09.084 A warning only helps if people receive it, understand it and can act on it. 00:05:09.234 --> 00:05:14.519 Transport, trust, shelter space and accessible communication affect evacuation. 00:05:17.200 --> 00:05:24.996 Warmer oceans and a warmer atmosphere can increase tropical cyclone rainfall and the potential intensity of the strongest storms. 00:05:25.146 --> 00:05:32.461 The proportion of very intense storms is expected to increase, but total global storm frequency is not certain to increase. 00:05:35.133 --> 00:05:38.982 Sea-level rise increases coastal flooding risk from storms. 00:05:39.132 --> 00:05:45.371 Where storms occur can also shift; climate change does not mean every ocean will develop tropical storms. 00:05:48.033 --> 00:05:54.661 U K hazards include heavy rain and flooding, strong winds, snow and ice, thunderstorms, drought and heatwaves. 00:05:54.811 --> 00:05:59.771 Their effects depend on duration, intensity, season and local vulnerability. 00:06:02.433 --> 00:06:05.609 Flooding can damage homes, transport and farmland. 00:06:05.759 --> 00:06:08.703 Drought can reduce river flows and water supplies. 00:06:08.853 --> 00:06:14.880 Heatwaves can increase illness and wildfire risk; snow and ice can interrupt travel and electricity. 00:06:17.533 --> 00:06:21.462 The U K has warmed, and extreme heat is becoming more likely. 00:06:21.612 --> 00:06:31.105 Climate change also increases the potential for heavy rainfall because warmer air can hold more moisture, although rainfall trends vary by season and region. 00:06:33.767 --> 00:06:36.668 A single event does not prove a long-term trend. 00:06:36.818 --> 00:06:45.500 Compare observations over many years and use attribution studies to assess how climate change has altered an event's likelihood or intensity. 00:06:48.167 --> 00:06:59.107 For a U K extreme-weather example, explain its atmospheric causes, separate social, economic and environmental effects, then link management actions to the risks they reduce. 00:07:01.767 --> 00:07:07.897 Typhoon Haiyan, known locally as Yolanda, crossed the Philippines on 8 November 2013. 00:07:08.047 --> 00:07:16.717 Warm western Pacific waters helped support an exceptionally powerful storm, and low-lying coastal settlements were exposed to its winds and surge. 00:07:19.367 --> 00:07:26.523 Strong winds destroyed buildings and storm-surge flooding devastated parts of Tacloban and surrounding coastal areas. 00:07:26.673 --> 00:07:32.239 W H O reports 6,300 deaths and more than 28,000 injuries. 00:07:34.900 --> 00:07:38.767 Damaged water supplies and health facilities increased health risks. 00:07:38.917 --> 00:07:46.807 Loss of homes, fishing boats, crops and businesses disrupted livelihoods, while damaged transport and communication delayed assistance. 00:07:49.467 --> 00:07:55.417 Immediate responses included rescue, food, clean water, temporary shelter and medical care. 00:07:55.567 --> 00:08:03.619 Philippine authorities and international agencies worked together; W H O helped coordinate emergency medical teams and supplies. 00:08:06.300 --> 00:08:15.845 Longer-term recovery included rebuilding health services, housing and livelihoods, alongside efforts to improve warning, evacuation and safer construction. 00:08:15.995 --> 00:08:21.583 Moving housing away from exposed coasts can reduce risk but may separate people from work. 00:08:24.233 --> 00:08:27.977 Haiyan shows why predicting a storm is only one part of protection. 00:08:28.127 --> 00:08:33.694 People also need to understand surge warnings and reach shelters that are safe from wind and flooding. 00:08:36.367 --> 00:08:45.346 During 16 to 19 July 2022, very hot air moved north from continental Europe and strong sunshine intensified the heat. 00:08:45.496 --> 00:08:54.679 On 19 July, Coningsby in Lincolnshire recorded 40.3 degrees Celsius, the U K's first recorded temperature above 40 degrees Celsius. 00:08:57.333 --> 00:09:02.059 Social impacts included heat illness and extra pressure on health services. 00:09:02.209 --> 00:09:08.874 Older people, people with existing health conditions and those unable to cool their homes were especially vulnerable. 00:09:11.533 --> 00:09:20.107 Transport and working conditions were affected: high temperatures can buckle rails and damage road surfaces, causing delays and extra costs. 00:09:20.257 --> 00:09:24.779 Businesses and schools had to adapt activities and protect people from heat. 00:09:27.433 --> 00:09:30.888 Dry vegetation and extreme heat increased fire risk. 00:09:31.038 --> 00:09:37.127 Fires damaged homes and habitats, while low water availability and heat stress affected wildlife. 00:09:37.277 --> 00:09:42.503 Separate the July event from longer-lasting drought conditions that developed during the summer. 00:09:45.167 --> 00:09:51.459 Warnings, health advice, checking vulnerable people and changing work or travel plans reduced exposure. 00:09:51.609 --> 00:09:57.760 Shading, cool spaces, water access and longer-term building adaptations can reduce future risk. 00:10:00.433 --> 00:10:04.665 Human-caused warming made such exceptional U K heat much more likely. 00:10:04.815 --> 00:10:11.598 A record temperature provides event evidence, while long-term temperature observations establish the wider trend. 00:10:14.267 --> 00:10:16.251 That completes Weather hazards. 00:10:16.401 --> 00:10:19.746 Revisit the notes and test yourself on the revision website.