Atmospheric Hazards Flashcards
Examples of Atmospheric hazards
Tornado
hurricane
Lightening
Wildfire
flooding
How many degrees has the global mean surface temp. increased by between 1850-1900, and 2011-2020
~1.09 degrees
what is England’s highest ever temperature recorded?
19th july 2022 . 40.3 degrees
what is the difference between weather and climate?
weather = the short-term changes in atmosphere, e.g. changing min to min
Climate = long-term description of variables/conditions
what do we use to measure earth’s weather?
satellites
- they also provide data over decades to monitor how our climate is changing
what is an extreme weather event?
a rare weather occurrence at a particular place and time of year, above or below the threshold value - vary place to place
what is an extreme climate event?
when extreme weather persists for a long period of time
when diagnosing a heatwave, what is considered?
Period,
Threshold (apparent or relative)
Scale
Location
what is relative and apparent temperature?
Relative = actual temp.
Apparent = what the temp feels like
How may apparent temperature differ?
based on:
- Meteorological factors (e.g. wind speed)
- Differences in body composition and shape
- Metabolic differences
- Levels of hydration
What is the heat index?
A measure of ‘how it feels’ (apparent temp.) and factors in relative humidity
What is the UKs definition of a heatwave?
when a location records a period of 3, or more consecutive days with daily maximum temperatures equal to, or exceeding the heatwave temp threshold.
- thresholds vary regionally, and change over time (~10 years), to reflect UKs changing climate
What is the average pressure at mean sea level?
1013.25 hPa (hectopascals)
what is air pressure measured in?
force per unit
what is the difference between horizontal and vertical pressure gradients?
Horizontal pressure gradients are smell compared to vertical pressure gradients, but horizontal pressure gradients are important as they drive wind movement
where is atmospheric pressure the strongest?
Pressure is larger closer to earth’s surface (more atmosphere above), and reduces with increasing height
Why does win flow from regions of high pressure to low pressure?
Earth rotates, so wind doesn’t more in a ‘straight line’. Wind gets deflected due to coriolois effect, creating a spiral effect
Explain convergence and divergence
Convergence = downwards moving wind
Divergence = upward moving wind
what does a high pressure system (anticyclones) involve?
involve downward moving air forming a high pressure area at the surface. Associated with settled conditions and clear skies
what does a low pressure system (depressions) involve?
involve upward movement of air, forming low pressure at the surface. Associated with unsettled weather
what causes heat waves?
heatwaves are more common in summer, and involve high pressure systems
‘blocking’ high pressure alters the passage of weather fronts meaning the same kind of weather is experienced for an extender period
Descending air is persistent in high pressure systems, with stagnant conditions and light winds, so heat is trapped at the surface.
may also be referred to as ‘heat dome’
what is the heat dome?
high pressure pushed warm air towards earth’s surface, as the air sinks, it warms due to compression. Heat is trapped due to low wind and stagnant conditions.
As the surface warms, it loses moisture, makes it easier to heat even more.
when are prominent heatwaves in Europe?
2003, 2006, 2018, 2019, and 2022
what is the urban heat island?
Local factors & micro-climate of a region are important
Tarmac and stone absorbs and stores heat during the daytime then emits heat at night
Waste heat from machinery in urban areas
The urban heat island effect can influence heatwave occurrence and exacerbate heat wave effects
Urban areas are hotter than lesser surrounding area
what factors are looked at when thinking about urban heat island?
Intensity, Duration, Frequency, Arel extent
What are the risks associated with heatwaves
Short-term rise in deaths during heatwaves.
Example: Summer 2003 heatwave in Western Europe caused tens of thousands of deaths.
Extreme heat harms body temperature regulation (the “silent killer”).
Health effects: Heat cramps, exhaustion (37–40°C), heatstroke (>40°C).
Impacts: Strain on healthcare and worsening air pollution.
How many deaths occurred in France due to the 2003 European heatwave?
around 14,000 (60% of which over 75 age)
What happens to infrastructure during extreme heat?
Power outages: In July 2022, sagging conductors and overheating transformers caused power cuts for nearly 8000 properties in Yorkshire, Lincolnshire, and the North East.
Rail disruptions: Hot steel expanded, increasing risks of buckled tracks and derailments. Emergency speed restrictions and train cancellations were implemented in July 2022.
Why do we care about heat waves?
Heat-related illness and death
Pressure on services
Heat-related economic impacts
Water/energy demand
Critical infrastructure impacts
Ecological impacts (including droughts, forest fires)
Co-occurrence of heatwaves and air pollution episodes
*Vulnerable groups most at risk
Who are the most at risk during heatwaves?
Very old and very young
Chronic and severe illness
Inability to adapt behaviour to keep cool
Environmental factors and overexposure (e.g. jobs that can’t get out of heat)
In particularly ‘bad’ heatwaves, groups that might be considered not at high risk are increasingly affected
What is the heat-health alert system (uk)
Provided by UKHSA & operates from June to September in the UK (in place since 2004)
Forewarns of upcoming hot weather based on Met Office forecasts and data
There are 5 heatwave plans alert levels reflecting degrees of preparedness and action needed
Mitigation tac tics on reducing heatwaves/their risks
educate & alert public + health providers
Identify & protect most at risk groups
Healthcare capacity
Protect critical infrastructure (airports, roads, rail, power)
Address urban heat islands
Address problematic buildings (e.g. those poorly ventilated)
Promote water efficiency and a water-saving culture
Optimise forecasting capability
How is climate change affecting heat waves?
Frequency, and intensity of hot extremes have increased
Human-induced greenhouse gasses is the main driver of the observed changes in hot and cold extremes on the global scale
*as climate warms, temp distribution is shifting, increasing likelihood of hot extremes
Characteristics of a hurricane
~300 miles wide
Has an organised structure, rotating systems of clouds and a warm core
Often comes with rain
Rotation depends on hemisphere (southern - clockwise, northern - anti-clockwise) due to Coriolis effect
low pressure at centre
wind speed >74 mph
form over oceans (and not all reach land)
what is the difference between hurricanes, cyclones and typhoons?
They are the same weather system, just depends on where you are.
called typhoons in SE Asia
called cyclones in Australia and Indian Ocean
called hurricanes around the Americas and Atlantic ocean
what are hurricanes?
Very severe tropical storms with winds about 74 mph characterised by its rotating cloud system and core
what is a tropical storm
a low pressure weather system with high winds and heavy rainfall
winds below 74mph but more than 39mph
*not all tropical storms turn into hurricanes
List 4 out of 7 basins where tropical cyclones occur
North Atlantic Ocean (inc. Gulf of Mexico, Caribbean sea)
Northeast Pacific
Norwest Pacific
North Indian
Southwest Indian
Southeast Indian/Australian
Australian/Southwest Pacific
Explain the seasonality of hurricanes
- they form at preferred times when environmental conditions are favourable
Hurricane ‘season’ in the Atlantic Basin is from the 1st June to 30th November with peak activity in September.
Majorly affected regions include Southern USA states, Mexico and parts of central America
*in the UK we hear most about hurricanes in the North Atlantic Basin (even though we don’t get them, but may get leftover winds after it has disipated)
Where is the location occurance of HUrricanes?
latitudes between 5-30 degrees north and south of the equator (tropics and subtropics)
can occur at less than 5 degrees of equator but this is extremely rare due to no Coriolis effect (creates the wind rotation)
Explain the formation of a hurricane
Low pressure zone (inward converging winds, counter clockwise in NH)
Warm oceans (>27°C)
High relative humidity
Atmospheric instability
Location more than 5° from equator (sufficient Coriolis force)
Low vertical wind shear (i.e. change in wind speed with height)
Weaken over land.
*powered by humid air and latent heat released from condensation. Allowing air to remain buoyant, and continue to rise. Contributing to clouds and an unstable atmosphere
Formaton of a hurricane in terms of a positive feedback loop
Wind blows over warm ocean
Sucks up heat and water vapes
Warm moist air rises
Water vapour condenses to form clouds
Condensation releases latent heat
Causes air to expand and rise even more
Decreases air pressure at the surface
Increases wind speed
(cycles)
What is the ‘general behaviour’ of hurricanes?
Takes several hours, to days to form. May last for many days and even weeks
Travel several thousand miles - sometimes in a very erratic path (steered by winds)
Decay after passing over cooler water or land (due to being cut off by energy source)
Important to differentiate between speed of rotating winds and speed of forward propagation.
what is the difference between torpical storms and hurricanes?
Tropical Storms (>39 mph)
Hurricanes (>74mph)
Explain the structure of a hurricane
The Eye
The central innermost area (20-40 miles across) with calm, clear skies, low air pressure, low wind speed, low rin, dry air descending.
The Eyewall
10-25 miles wide, dense thunderstorms. Rainfall and wind speed at maximum
Rainbands
Intensive clouds and rainfall extending several hundred miles from the eye. Wind speeds progressively decrease towards the edge of the storm.
*Low pressure in eye, and increases as you move away from the centre
what are the hurricane wind velocity characteristics?
Speed of rotating winds within hurricane
Categories 1-5 on Saffir-Simpson scale
Minimum 74 mph (below this: Beaufort Scale 0-11)
Maximum > ~160 mph
What are the hurricane storm centre velocity characteristics?
Speed of entire storm – typically 15–20 mph
Affected by wider atmospheric flows that steer the storm system
Can reduce to near 0 mph if hurricane stalls
Can exceed 60 mph, particularly at high latitudes
Explain what is meant by hurricane intensity
Intensity is strongest where storm centre velocity and hurricane wind velocity are in the same direction
For a northward travelling hurricane in the northern hemisphere, highest intensity is on the eastern side.
what is the Saffir-Simpson Scale
classifies tropical cyclones based on wind speed and its impacts
It has a 5 category system
1. 74-95mph - very dangerous winds, some damage (e.g. power cuts)
- 96-110 mph - extremely dangerous winds. Extensive damage
- 111-129mph - devastating damage occurs (e.g. well built homes damaged)
- 130-156 mph - extreme damage (e.g. severe dame to well-built homes)
- > 157 mph - catastrophic damage (e.g. many buildings destroyed, major roads cut off)
What are hurricane hazards?
Extreme wind speed
Storm surges
Torrential rainfall and flooding
Rip currents (even when miles from shore)
Tornadoes
Loss of life from other causal factors (e.g. disease transmission, loss of facilities and infrastructure)
What is a storms surge?
A change in sea level - is caused by high winds and low pressure
Flooding and heavy waves can damage coastal areas 6-12 hours before landfall
E.g. Bangladesh 1970
Explaint he hazard of extreme rainfall.
Tropical cyclones may produce copious amount of rainfall leading to destructive flooding (6-12 inches or more) +/- 6 hours from landfall
Slower moving (<10 mph or ‘stalled) and larger storms produce the most rainfall
Can induce coastal and inland flash floods with more longer term flooding of rivers/streams lasting for days
Can trigger devastating mudslides in mountainous regions
How will hurricanes change in the future?
No strong evidence to suggest that the frequency of hurricanes will increase in the future.
But, strong evidence that the intensity of hurricanes will increase, with more hurricanes expected to reach category 4 and 5
How will climate change exacerbate the impacts of hurricanes?
Rising sea levels worsen storm surges
More water vapour in the atmosphere, more rain
Potentially change the path of tropical cyclones
What are the benefits of forecasting and monitoring hurricanes in reducing vulnerability?
E.g. NOAA National Hurricane Centre (Florida)
Detect hurricanes as they form using satellite imagery
Issue a ‘hurricane watch’ alert (~ 48 h before landfall) and monitor closely.
Analyse observational data (air pressure / temp / humidity / wind speed) from land, sea, aircraft and satellites)
Feed observational data into process/statistical models, to predict path, landfall, and height of storm surge (e.g., SLOSH – Sea, Lake & Overland Surges from Hurricanes).
Issue a ‘Hurricane Warning’ to vulnerable communities – usually 24-36 hours before landfall – so they can initiate evacuation and other preparedness plans
A 72-hour forecast has a margin of error of about 160 km. Reduces to 65 km for a 24-hr forecast.
<24-hour warning increases the accuracy and minimises unnecessary evacuation (BUT expensive!)
What are the benefits of wind and storm surge defences in reducing vulnerability?
Natural defences
- wide beaches, high dunes, mangrove forests.
Artificial defences
- raised mounds, concrete shelters, sea walls, levees, river flood barriers.
Building regulations
- structures can be elevated and designed to withstand high winds:
> rounded walls and pitched roofs to promote wind flow around structure
> anchor bolts between foundations, walls and roofs
> cross bracing
> shutters on windows
