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Request:1. Post either asks a question related to the corresponding module or shares/describes something interesting (any sources are cited) and weather related. The post is thoughtful, well written, and is of substantial meaning to the discussion as a whole. The post doesn’t just regurgitate course material, but expresses your understanding and reflection of the material.2. Reply to someone else’s post, either answering their question, or building on the information provided in the original post.Once, you finish first part, and give the first part to me I will give back some’s discussion to write the second part.Each discussion should be more than 50 words
Meteorology 10
Terrence J. Mullens
Meteorology 10
Terrence J. Mullens
What Are they?
Why Do We Care?
Microscale
Less than a few meters and lasts only a few seconds to a few minutes.
Turbulent eddies (such as in smoke stacks).
Mesoscale
A few miles up to about 20 km; can last minutes to hours.
Rotating thunderstorms, Tornados, Dust Devils, The Sea Breeze.
Synoptic Scale
Hundreds to Thousands of miles, and can last for days.
Weather Systems (mid-latitude cyclones, Hurricanes, Pressure systems,
etc).
Global Scale
Can span across thousands of miles and cover the globe; can last weeks
or even longer (some are permanent)
Troughs/Ridges (Longwaves), Hadley Cells, Ocean currents, etc.
El Niño and La Niña
Turbulent Eddies and Waves
In stable weather, a strong wind blowing over a
mountain can produce a series of waves and
eddies that blow many kilometers downwind of
the mountain.
Form when there is vertical wind shear…
The boundary between weaker winds (below) and
stronger winds (aloft) deforms, creating waves.
Examples of Local Wind Circulations include:
Sea Breeze (Already talked about!)
Monsoon Circulations
Land Breezes
Most Local Wind Circulations are Thermally
Driven.
A thermally-driven circulation.
Steps to formation
Step 1: Land heats up more than the Ocean
Step 2: “Column” over land grows while “column”
over the ocean shrinks.
High pressure aloft develops over land, low pressure
develops over the ocean.
Step 3: Air aloft travels from land to ocean.
Surface pressure lowers over land while it increases over
the ocean.
Step 4: Air at the surface travels from the ocean to
the land.
The air over land cools more than the ocean…
This causes the circulation to reverse.
The reversed circulation is called the Land Breeze.
Often present over small islands and peninsulas.
Sea breezes occur on both sides of the
peninsula.
They converge in the middle.
If the ocean is warm and the air is hot/moist,
thunderstorms are produced from the convergent
sea breezes.
The same principle as sea breezes also occurs
seasonally!
Monsoonal winds change directions seasonally
(rather than between day and night)
Monsoonal winds can also extend well inland
unlike seabreezes.
Obviously, larger weather patterns are partially
responsible!
Winter time: Air over land is almost always
colder than air over water: Winds blow
offshore!
Summer time: Air over land is much warmer
than air over water: Winds blow onshore!
The geography of the region, location to water,
and the temperature (and thus heat storage) of
the water are all important!
Mid-Latitude Cyclones
Hurricanes and Tropical Systems
We’ll talk more about these in the next few
days…
Meteorology 10
Terrence J. Mullens
The General Circulation of the Atmosphere
The single biggest TERRESTRIAL (on Earth) cause of
climate!
These next slides only represent the average air
flow around the world… THIS SHIFTS a little!
What causes this? UNEVEN HEATING OF THE
EARTH!
Warm air is transported Poleward, Cool air Equatorward!
Single Celled Models
Used to describe the BASICS of atmospheric
circulation.
Earth’s surface is uniformly covered with Water.
Sun is always directly over the equator
Earth does not rotate… so we only deal with PGF.
DON’T WORRY ABOUT THE SUN BEATING DOWN ON ONE
SIDE AND NOT ON THE OTHER… this is just a model!
Warm Air rises at the Equator (Low surface pressure), and sinks at
the Poles as cold air (High surface pressure).
The cells (circulation between Equator and Pole)
are called Hadley Cells
While this model is extremely crude, doesn’t it
give a pretty accurate generalization of the
Earth’s climates?
Now, let’s make the model more complex:
We allow the earth to rotate so CF is back in the
mix
The single cell now breaks up into three cells
because of the influence of the CF.
Still many similarities to the Single Cell Model:
Tropics get most of the heat, but now the Coriolis force
aids convergence, leading to stormy weather at the
tropics.
Where the Jet
Stream forms!
Average position of the polar jet stream and the subtropical jet stream,
with respect to a model of the general circulation in winter. Both jet
streams are flowing from west to east.
A band of extremely
fast (higher than 200
miles per hour) wind in
the upper atmosphere
(at approximately 10
kilometers).
A boundary between
warm air from the
equator, with cold air
from the poles.
The Equator
The Poles
Meteorology 10
Terrence J. Mullens
The ocean does not just remain stagnate!
Rather, the ocean consists of massive bodies of
water that are constantly on the move!
These are referred to as ocean currents.
Ocean currents carry large amounts of water from
one place to another, often transferring heat and
matter with them!
Ocean currents occur both at the surface, and deep
below.
On the surface, ocean water currents rotate in a
series of ocean gyres, with the ocean
movement occurring along coastlines.
In the Northern Hemisphere, this results in a
series of gyres that spin clockwise and in the
Southern Hemisphere, they spin counterclockwise.
There are five primary gyres: North Atlantic,
North Pacific, South Atlantic, South Pacific, and
South Indian Ocean Gyres.
Continent Prospective: We are on the West
Coast of the United States!
Oceanic Prospective: We are on the Eastern End
of the Pacific Ocean!
Confused? Find a map of the Pacific and put
your finger on Hawaii… Move your finger to the
east (right) across the pacific until you hit land.
Where do you end up?
North America!
Moving West
Moving East
Western Boundary Currents: On the Western End
of the Ocean Basin
Carry warm water poleward
Famous Examples: The Gulf Stream and the Kuroshio
current.
Eastern Boundary Currents: On the Eastern End of
the Ocean Basin
Carry cold water equatorward
Famous Examples: The California Current (off our
coast).
Equatorial Currents: Over the Equator.
Carry water from East to West.
Western Boundary Currents
Eastern Boundary Currents
Equatorial Currents
WIND!!!
Between the Equator and 30°N/S: Trade Winds
blow from East to West.
Between 30°N/S and 60°N/S: Mid-Latitude
Westerlies blow from West to East.
Between 60°N/S and the poles: Polar Easterlies
blow from East to West.
Remember, ocean currents carry water of different
temperatures from one location to another:
In other words, ocean currents are a form of heat
transport.
These currents travel along coastlines, releasing
their heat to the land through sea breezes. Because
of this:
Warm Ocean Currents are related to Warm, Wet
weather.
Cold Ocean Currents are related to Cooler, Dryer
weather.
Important indicator of the development of El
Nino/La Nina in the Equatorial Pacific.
In a “Normal” (aka neither El Nino nor La Nina)
year, warm water is pushed Westward, leaving
cooler waters in the Eastern Pacific.
As a result, there is:
More rising air, lower pressure, and stormier
weather in the Western Pacific
More sinking air, higher pressure, and dry weather
in the Eastern Pacific.
The Slang Term for when Equatorial Pacific Ocean
Temperatures are near normal, and thus they have
little additional impact on Global Circulation.
It is believed that the ocean circulation is in a
constant state of oscillation between El Ninos and
La Ninas.
In the normal set-up, the East-West Equatorial
Trade winds blow warm water towards the coasts
of Asia and Australia, giving them substantial
rainfall.
The Eastern Pacific, on the other hand, is much cooler,
more stable, and drier.
Named after the Baby Jesus (translated as The
Small Boy).
Occurs when the equatorial trade winds (which
blow from East to West) slacken off, or reverse,
allowing warm water to collect along the Eastern
Pacific Basin.
This region usually has cooler water, and thus drier
weather.
In an El Nino, this region has torrential rains, more
hurricanes, and warmer temperatures while the West
Pacific experiences severe droughts.
The opposite of El Nino (hence, La Nina = The
Little Girl)
Occurs when normal trade winds strengthen
and blow additional warm water to the West
Pacific.
This results in even wetter than average rainfall
in the Western Pacific, and drier than average
rainfall in the Eastern Pacific
Affected 2012-2015 California Rain Seasons
Occurred because of a giant ridge of high
pressure developed, which prevented storm
systems from reaching California.
A large body of
warm water over
the northern
Pacific Ocean.
Warm water leads
to warm air, which
could create a
ridge.
What came first,
the ridge or the
blob?
Air Masses, Fronts, and
Mid-Latitude Cyclones!
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