Weather Hazards Flashcards
Tri-cellular model of atmospheric circulation
-starts at the top
-Polar Cell
-Ferrel cell
-Hadley cell
then
-Hadley cell
-Ferrel cell
-Polar cell
Air Pressure & Surface winds
Air Pressure: the weight of the air
low=light
high=heavy
light rising air from low pressure creates clouds, rain and strong winds
heay sinking air from high pressure creates sunny, clear skies
Pressure Belts
N downwards
Polar HIGH- cold&dry
sub-polar LOW- mild&wet (England)
Sub-tropical HIGH- hot&dry
Tropical LOW- hot&wet (the tropics have high rates of insolation so get the most heat and convectional uplift) and tropical revolving storms ( like Typhoon Haiyan)
Air Masses & Weather Fronts
Air Mass- a large body of air with uniform characteristics, moisture and temp They take on the characteristics of the plcae where they formed. when 2 air masses meet they create a weather front
Weather Front-
cold&dry formed over land
warm&wet formed over the sea
they meet and the warm air rises creating rain
Rainfall (3)
Mechanisms of Uplift
1-convectional- the sun warms the Earth’s crust, warm air rises, condenses at DEW POINT forming clouds, rain occurs.
2-frontal- two air masses meet, warm air rises, reaches DEW POINT and condenses forming clouds, rain occurs
3-relief/orographic- warm moist air travels in from the sea, rises up the mountain range by force, reached DEW POINT, condenses, forms clouds
Tropical storms/ hurricanes
an extensive area of extreme low pressure that gives rise to circular inward spiralling winds
form in the pressure belt: Tropical Low
ONLY FORM IN WARM OCEANS
=IN the Tropics 0+-5’ N/S never exactly on the equatoras the CORIOLIS EFFECT is too weak.
=form end of summer early autumn when sea is warmest
=they move out of the tropics
=Northern hemishpere they spiral ANTI-clockwise
=Southern hemisphere they spiral CLOCKwise**
=rotation occurs around the eye of the storm which is calm, surrounded by swirling mass of cloud
=Ocean surface temp needs to be 26-27’C to depth of 10 metres
=
STAGES OF DEVELOPMENT FOR
Tropical storms
1- GENESIS
warm ocean in the tropics (27’C depth 10m)
MORE convectional uplift
MORE evaporation
2-DEVELOPMENT
cumulonimbus clouds form as the ocean is still warming creating LOW ATMOSPHERIC PRESSURE
wind sweeps over to replace the air rising MORE evaporation & convection
creates clouds
3-MATURITY
Tropical storms Northern rotate aNticlockwise
Southern rotate clockwise
=swirling winds caused by the Coriolis effect(the Earth’s rotation) create a central eye 30-50km
the eye is an area of subsiding air, light winds, high temp, surrounded by cloud
WInd speeds 100-150mph
as the storms travels over warm ocean it gathers more strength.
4-DECAY-
once the hurricane reaches land they decline in strength
=loss of heat and moisture from the ocean
=increased friction with land
=reaching cooler waters away from the tropics
life span 7-14 days
How will Climate Change affect tropical storms?
Climate change will NOT result in more tropical storms but the ones that DO develop could be stronger, wetter and more devastating
-move more slowly staying in one area for longer
-if the atmosphere is warmer:
1-higher rates of evaporation/more rain
2-stronger convectional uplift
3-stronger winds
What are the UK’s extreme weather hazards?
-Drought
-Flooding ( River Severn )
-Heat waves
-blizzards
Extreme weather hazards in the UK in the last few decades
1-Boscastle floods 2004
2-Somerset floods 2014
3-Coastal storms in SW England 2014
4-Beast from the East 2018
5-UK Heatwave 2018,2022
Why are extreme weather hazards incresing for the UK?
evidence suggests climate change as a warmer atmosphere is more unpredictable.
The weather front that sits over the UK (jet stream) that brings in storms and low-pressure weather events is staying over the UK for longer due to global warming!
