Lecture 3 Vertical Structure of the Atmosphere. Average Vertical Temperature profile.
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Transcript of Lecture 3 Vertical Structure of the Atmosphere. Average Vertical Temperature profile.
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Lecture 3Lecture 3
Vertical Structure of the Vertical Structure of the AtmosphereAtmosphere
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Average Vertical Temperature profile
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Atmospheric LayersAtmospheric Layers
TroposphereTroposphere On average, temperature decreases with On average, temperature decreases with
heightheight
StratosphereStratosphere On average, temperature increases with On average, temperature increases with
heightheight
MesosphereMesosphere
ThermosphereThermosphere
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Lapse RateLapse Rate
Lapse rate is rate that temperature Lapse rate is rate that temperature decreases with heightdecreases with height
z
T
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SoundingsSoundings
Actual vertical temperature profiles are Actual vertical temperature profiles are called called soundingssoundings
A sounding is obtained using an A sounding is obtained using an instrument package called a instrument package called a radiosonderadiosonde
Radiosondes are carried aloft using Radiosondes are carried aloft using balloons filled with hydrogen or heliumballoons filled with hydrogen or helium
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Radiosonde
http://www.srh.noaa.gov/mob/balloon.shtml
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Application: Reduction to Sea LevelApplication: Reduction to Sea Level(See Ahrens, Ch. 6)(See Ahrens, Ch. 6)
Surface pressure here
proportional to weight of this column of air
Surface pressure also called station pressure (if there is a weather station there!)
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MathMath
sfcz
sfc dzgp
Obtained by integrating the hydrostatic equation from the surface to top of atmosphere.
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Deficiencies of Surface PressureDeficiencies of Surface Pressure
Spatial variations in surface pressure Spatial variations in surface pressure mainly due to topography, not meteorologymainly due to topography, not meteorology
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900
950
1000
1050
Height contours on topographic map
Units: m
It’s a mountain!
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Put a bunch of barometers on the mountain.
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Surface pressure (approximately)
885
890
895
900
Isobar pattern looks just like height-contour pattern!
Units: hPa
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““Reduction to Sea Level”Reduction to Sea Level”
Sea Level
Surface pressure here
is proportional to weight of this column of air
Let T = sfc. temp. (12-hour avg.)
For sea level pressure
add weight of isothermal column of air
temp = T.
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Pressure as Vertical CoordinatePressure as Vertical Coordinate
Pressure is a 1-1 function of heightPressure is a 1-1 function of height i.e., a given pressure occurs at a unique i.e., a given pressure occurs at a unique
heightheight
Thus, the pressure can be used to specify Thus, the pressure can be used to specify the vertical position of a pointthe vertical position of a point
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Given p
At what height is the pressure equal to p?
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Pressure SurfacesPressure Surfaces
Let the pressure, pLet the pressure, p11, be given., be given.
At a given instant, consider all points (x, y, z) At a given instant, consider all points (x, y, z) where p = pwhere p = p11
This set of points defines a This set of points defines a surfacesurface
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x
z
p = p1
x1 x2
z(x1) z(x2)
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Height ContoursHeight Contours
Heights indicated in dekameters (dam) 1dam = 10m
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Two Pressure SurfacesTwo Pressure Surfacesz
p = p1
p = p2
z2
z1
z2 – z1
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ThicknessThickness
zz22 – z – z11 is called the is called the thicknessthickness of the layer
Hypsometric equation thickness proportional to mean temperature of layer
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Thickness GradientsThickness Gradientsz
p = p1
p = p2
Small thicknessLarge thickness
Coldwarm
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ExerciseExerciseSuppose that the mean temperature Suppose that the mean temperature between 1000 hPa and 500 hPa is -10between 1000 hPa and 500 hPa is -10C.C.
Calculate the thickness (in dam)Calculate the thickness (in dam)
dammKKm
Ksm
Ksm
Ksm
K
Tg
Rzz
534534015.2633.20
15.26320.3
15.263693.081.9
kg287J
2ln
1
2
122
2
11-
12
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Repeat, for T = -20Repeat, for T = -20CC
damm
KKmzz
5145140
15.2533.20 112
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Thickness MapsThickness Maps