Local and Global weather
Firstly we need to look at some basic principals of weather (and physics)
Hot air rises
Cold air sinks
Air moves from high to low pressure
Airspace needs to be filled when air is displaced
Air does not move in straight lines
The sea moderates temperature
Local weather phenomena only occurs when air is stable
Hot Air Rises – Cold air sinks
It’s a rule, warm air is lighter and less dense so will rise into the atmosphere and cold air will descend to the ground
What will often happen, is that as it rises it cools and sinks again
Air moves from high to low pressure
Airspace needs to be filled when air is displaced
Air at ground level flows out of a high and into a low
Air does not move in straight lines
The sea moderates temperature
The land cools more quickly and holds the cold so therefore keeps the air cold
The sea cools slower and changes less from summer to winter
Local weather phenomena only occurs when air is stable
Katabatic winds
Sea breeze
Valley winds
Thermals
Planetary Processes
Regions of the Planet
There are a number of distinct regions on Planet Earth and they all have a large influence on what grows there, who lives there and activities that can be carried out there
Image taken from: http://geolt14.wordpress.com/2012/01/06/factors-affecting-climate/
Planetary or Global Influences on Weather
Global Air Circulation
Remember the basics of weather, warm air rises because it is less dense and cold air sinks as it is more dense
Global Air Circulation
Image: http://facweb.bhc.edu/academics/science/harwoodr/geog101/study/images/cells2.jpg
This means that we in NZ/ Aotearoa are in the Ferrel Cell
Image: http://cals.arizona.edu/watershedsteward/resources/module/Climate/images/cells-highs-lows.jpg
Weather Systems travel this way
H
L
Sub Tropical low
Sub Antarctic low
Temperate zone High Pressure System
Image: http://www.meteor.iastate.edu/gccourse/ocean/images/image2.jpg
There is also a global water circulation system that delivers cold water from the poles and warms it through the tropics
Other larger scale influences on Weather and Climate - Click the links to explore
What drives our weather?
The Water Cycle
The Water Cycle is the circulation of water through the Earth's system
Highs and Lows
How do Highs and Lows form?
H L
Void of air sucking air up to fill it
High pressure forcing down on the earth’s surface
Once the air hits the surface, it spreads out in a circular pattern according the coriolis force
The air is sucked in a circular pattern into a low pressure system and it rises to the upper atmosphere
Adiabatic Lapse Rate
This is the concept where air gets cooler the higher up in the atmosphere
Image from: http://www.atmos.umd.edu/~meto200/2_25_03_lecture_files/v3_document.htm
Inversions
As the previous slide said, it gets colder as you go higher into the atmosphere.... Most of the time!
Local Influences on the Weather
Fronts
Fronts are the meeting of two bodies of air and the resultant effect is rain and cloud formation
Warm air Cold air
Cold Air Warm Air
Cold Front
Remember the golden rules:
Warm Front
Stationary front
Occluded front
Surface Heating / Cooling – Uphill Breeze - Thermal
Surface heating
These winds are often used by Hang gliders and normal gliders as they provide uplift
Surface Cooling – Katabatic Wind
Get into groups of 5 and lets tell the story of the Greymouth Barber – you can use any props you want including yourselves
Topography
In Aotearoa / New Zealand, there is a lot of dramatic topography which influences the weather
Norwester Video
Features of New Zealand / Aotearoa’s Climate
Clouds
Cumulus
Cumulonimbus
Stratus
Cirrus
Stratocumulus
Nimbostratus
Cirrocumulus
Altostratus
Lenticular