Transcript PowerPoint-presentation

The Air we breath is composed of…….
Nitrogen, Oxygen, Argon, Carbondioxide,
Water vapor and some other gases…
The gases above they all have some weight
and since then they all exert a force, or
pressure, on our bodies = athmospheric
pressure.
What causes wind?
Air moves because of differences in both
temperature and pressure, also called
atmospheric pressure, which is the pressure
exerted by the atmosphere at Earth's
surface due to the weight of the air.
Why is the wind interesting?
Effects on people
and buildings.
Aircraft
Wind power.
Sailing
Air-pollution,
Radioactivity
Etc.
Wind vane
The wind
Wind direction, from which it’s blowing
Direction 0 -360º or N, S, W, E, ”true north”
NNV = 340 º
Speed units:
m/s, kt, mph, km/h, kuling etc.
Cup anemometer
1 m/s = 1.94 kt
1 kt = 0,51 m/s
Pressure….
Characteristics
1)
What are the different units of
pressure? Which unit is used most by
meteorologists?
2)
Which is the correct respons in the
following sentence: ’Pressure
increases/deceases with height’.
Please explain why pressure changes
this way with height.
3)
Draw the symbol that represents a
high pressure center on a weather
map. Do the same for a low pressure
center.
4)
Pictured left are two imaginary
columns of air molecules exerting
pressure on the surface below them.
The left column contains fewer air
molecules than the right column. What
do they represent?
Pressure Gradient Force
directed from high to low pressure
The change in pressure measured
across a given distance is called a
"pressure gradient".
The pressure gradient results in a
net force that is directed from high
to low pressure and this force is
called the "pressure gradient force".
Coriolis Force
Effect of the Earth's rotation on the atmosphere,
oceans, and theoretically all objects moving over
the Earth's surface. In the northern hemisphere it
causes moving objects and currents to be
deflected to the right; in the southern hemisphere
it causes deflection to the left. The effect is named
after its discoverer, French mathematician
Gaspard de Coriolis (1792–1843).
Isobars and weather
current weather
The Geostrophic wind
PGF
C
Gradient wind
Clockwise rotation:
Centrifugal force (Cf) and PGF
are co-operating a C must be
greater in a balanced situation
compared with the Geostrophic
wind
aVgr > Vg, if PGF and latitude
is the same
Gradient wind
Anti-clockwise rotation:
Cf and C are co-operating a
C must be lesser in a balanced
situation compared with the
Geostrophic wind
aVgr < Vg, if PGF and latitude
is the same
Sea breeze
Clouds I
Clouds II
Cumulunimbus
•Showers of rain/snow
•Hail
•Thunder
•Tornados
Precipitation Along Fronts II
Warm front
A layer of thin clouds is occasionally observed
more than a thousand kilometers in advance of
a surface warm front. As the front gets closer,
the clouds thicken and eventually light
precipitation begins to fall. Because the frontal
surface gently slopes up and over the cold air
mass ahead of it, the upward motions
associated with warm fronts are typically not as
strong as the vigorous upward motions that
occur ahead of a cold front.
Precipitation Along Fronts I
Cold Front
Initially, the cold air mass wedges into the warmer
air mass ahead of it, (separated from each other
by the cold front). The lighter warm air is lifted
upwards by the denser cold air and if enough
water vapor condenses, clouds develop.
If condensation of water vapor persists,
precipitation may develop, typically in a narrow
band just ahead of the cold front.
Due to the steep slope of a cold front, vigorous
rising motion is often produced, leading to the
development of showers and occasionally severe
thunderstorms.