Vertstructofatmosph

Vertstructofatmosph - Vertical Structure of the Atmosphere

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Unformatted text preview: Vertical Structure of the Atmosphere Forecast
Challenge 
 Available 
 on
WebVista
Today 
 Submission
due
by 
 th
at
5
pm this
Friday
29 
 Be
sure
to
complete
the
 course
survey
on
WebVista 
 Weather
Briefing 
 Recap 
 Definitions The condition of the atmosphere at a given time & location with respect to – temperature, pressure, humidity, and wind. •  Weather record of average •  Climate – Historical weather events. daily & seasonal Pictorial View of the Atmosphere Atmospheric Composition •  See Table 1.1 (p. 3) •  Nitrogen •  Oxygen •  Trace Gases –  –  –  –  –  Water vapor Carbon dioxide Ozone Methane Nitrous oxide ATMS 100 8 Our
Present
Atmosphere 
 •  Current atmospheric composition is only 250 million years old •  Big “little” changes now going on – GH gases How do we describe atmospheric conditions? •  Pressure (p) •  Temperature (T) •  Moisture (water vapor) - humidity •  Wind Pressure (p) •  Definition: Force exerted on Earth's surface by air molecules Always decreases with height Varies more in the vertical than the horizontal Measured with a barometer Mercury Barometer •  Units: millibars (mb) Pressure •  Range of values at sea level •  Variation with height Temperature (T) •  Definition: Average kinetic energy of air molecules Usually decreases with height Large variations in the horizontal and vertical •  Units: °F and °C Temperature (T) Range of values at sea level Variation with height 14 Vertical
Structure
of
the
 Atmosphere 
 •  Can be divided into a series of layers •  Most often divided by temperature changes •  Also can be divided based on chemical composition and the processes that occur Thermodynamic
State
of
the
 Atmosphere 
 Measured
by
its
temperature,
density,
and
pressure
 What
is
temperature?
 Parcel
of
Air
 Thermodynamic
State
of
the
 Atmosphere 
 1.
Temperature
 -
Degree
of
“hotness”
or
“coldness”
of
a
substance
 - Measure
of
the
average
kinetic
energy
of
any
substance
 Parcel
of
Air
 Thermodynamic
State
of
the
 Atmosphere 
 2.
Density
 -
Mass
of
air
molecules
in
a
 given
volume
 mass kg Density = =3 volume m € Thermodynamic
State
of
the
 Atmosphere 
 3.
Pressure
 Force Newton Pressure = = = Pascal 2 Area m m Force = mass × acceleration = kg ⋅ 2 = N s What
is
atmospheric
pressure? 
 The
mass
of
the
air
molecules
over
our
 heads
being
acted
on
by
gravity.
 altitude
 How
much
air
is
over
your
head
right
now
(in
kg/m2)?
 Standard
atmospheric
pressure
at
sea
level:
 1013.25
mbar
=
1013.25
hPa
=101325
Pa
 Pressure
=
Force
/
Area
 Force
=
mass
x
acceleration
 g
 Sea
level
 How
are
pressure
and
density
 related? 
 Why?
 The
Equation
of
State: 
 The
Ideal
Gas
Law 
 States
that
air
pressure,
air
density
and

 air
temperature
are
all
interrelated

 *
a
change
in
one
will
cause
a
change
in
the
other
 P = ρRT air pressure J m-3 (Pascal) air temperature (Kelvin) € air density kg m-3 gas constant 287 J K-1 kg-1 What
happens
to
pressure
when
 we
increase
the
temperature? 
 Air
parcel
 P = ρRT air pressure J m-3 (Pascal) air temperature (Kelvin) € air density kg m-3 gas constant 287 J K-1 kg-1 Atmospheric
Pressure
Profile 
 24 The
“Lazy
W” 
 25 Atmospheric
Temperature
Profile 
 •  Atmospheric temperature and density decrease uniformly with height •  Temperature does not •  Letʼs take a vertical tour The
Troposphere 
 •  Surface to ~11 km (7 mi) •  Where all the weather happens •  On average, temperature decreases with height – rate referred to as Lapse Rate (Γ) •  Average rate is: •  Γ = 6.5 °C / km •  Γ = 3.6 °F / 1000 ft The
Tropopause 
 •  Just above the troposphere •  Temperature stops decreasing with height – remains nearly constant •  Γ ≈ 0 °C / km •  Termed Isothermal •  The height varies in the atmosphere: •  Higher over tropics •  Lower over polar regions The
Stratosphere 
 •  From top of tropopause to ~ 50 km (30 mi) •  Temperature increases with height •  Termed a Temperature Inversion •  Warming due to UV radiation interacting with Ozone •  Inhibits vertical currents in the troposphere from spreading into the stratosphere Anvil
Head 
 The
Mesosphere 
 •  From top of stratopause to ~ 85 km (53 mi) •  Temperature again decreases with height •  Air is “thin” w/ low pressure – few molecules •  Very cold The
Thermosphere 
 •  From top of mesopause to ~ 500 km (310 mi) •  Few atoms & molecules present •  Temperature again increases with height (max of 500 °C +) •  O2 molecules absorb energetic solar radiation and warm the air •  For humans it would be cold – why? The
Exosphere 
 •  From top of thermopause to ~ ??? So
how
do
we
get
information
 about
the
vertical
structure
of
 the
atmosphere? 
 Atmospheric
Soundings 
 How
We
Probe
the
Atmosphere 
 Radiosondes 
 NWS
Soundings 
 The
 National
 Weather
 Service
 (NWS)
 Upper-air
 Observations
 Program
 is
 managed
 by
 the
 Observing
 Systems
 Branch
 (OSB),
 which
 is
 part
 of
 NWS
 Headquarters
located
in
Silver
Spring,
Maryland.
 Upper-air
 Program
 staff
 oversee
 the
 operation
 of
 92
 Radiosonde
 
 stations
 in
 North
 America
 and
 the
 Pacific
 islands.
It
also
supports
the
operation
of
10
stations
in
the
 Caribbean.
 Radiosonde
Facts 
 The
 radiosonde
 flight
 can
 last
 in
 excess
 of
 two
 hours,
 and
 during
 this
 time
 the
 radiosonde
 can
 ascend
 to
 over
 35
 km
 (about
115,000
feet)
and
drift
more
than
300
km
(about
180
 miles)
from
the
release
point.
 During
the
flight,
the
 radiosonde
is
exposed
to
temperatures
 as
 cold
 as
 -90oC
 (-130oF)
 and
 an
 air
 pressure
 only
 few
 thousandths
of
what
is
found
on
the
Earth's
surface.
 If
 the
 radiosonde
 enters
 a
 strong
 jet
 stream
 it
 can
 travel
 at
 speeds
exceeding
400
km/hr
(250
mph).


 Radiosonde
Facts 
 When
released, 
the
balloon
is
about
2
meters
(about
6
feet)
 in
diameter
and
gradually
expands
as
it
rises.
 When
the
balloon
reaches
a
diameter
of
6
to
8
meters
(20
to
 25
feet)
in
diameter,
it
bursts.
 A
small, 
orange
colored
parachute
slows
the
descent
of
the
 radiosonde,
minimizing
the
danger
to
lives
and
property.
 Radiosonde
Facts 
 Although
all
the
data
from
the
flight
are
used,
data
from
the
 surface
to
the
400
hPa
pressure
level
(about
7
km
or
23,000
 feet)
 are
 considered
 minimally
 acceptable
 for
 NWS
 operations.
 Thus,
 a
 flight
 may
 be
 deemed
 a
 failure
 and
 a
 second
 radiosonde
released
if
the
balloon
bursts
before
reaching
the
 400
hPa
pressure
level
or
if
more
than
6
minutes
of
pressure
 and/or
 temperature
 data
 between
 the
 surface
 and
 400
 hPa
 are
missing.
 Less
 than
 20
 percent
 of
 the
 approximately
 75,000
 radiosondes
released
by
the
NWS
each
year
are
found
and
 returned
to
the
NWS
for
reconditioning.
 A
Typical
Sounding 
 QUIZ: Weather or Climate? [18] The layer of the atmosphere where all the weather occurs is called the: a)  b)  c)  d)  Troposphere Tropopause Stratosphere Mesopause QUIZ: Weather or Climate? [19] The temperature profile in the stratosphere is characterized by: a)  b)  c)  d)  A standard lapse rate A temperature inversion An isothermal atmosphere None of the above QUIZ: Weather or Climate? [20] Radiosondes are launched how many times each day? a)  b)  c)  d)  2 4 1 3 QUIZ: Weather or Climate? [21] An isothermal atmosphere is one in which temperature __________ with height. a)  Remains constant b)  Decreases c)  Increases ...
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