Weather 101 and beyond

Hot Airventure 1

Weather 101 and beyondWeather 101 and beyond

Edward J. HopkinsEdward J. HopkinsDept. of Atmospheric &Dept. of Atmospheric &

Oceanic Sciences Oceanic Sciences

Univ. of Wisconsin-MadisonUniv. of Wisconsin-Madison

Midwest Hot Air Balloon Safety SeminarMidwest Hot Air Balloon Safety Seminar““Hot Aireventure”Hot Aireventure”

Oshkosh 3 March 2001Oshkosh 3 March 2001

Hot Airventure 2

Concerns of BalloonistsConcerns of Balloonists

The Weather

The Terrain (or Surface)

Hot Airventure 3

Hot Airventure 4

QuizQuiz

Ballooning (Fair) Weather is associated with High or Low Pressure?

Which way do winds blow around:

High pressure?– Low pressure?

Hot Airventure 5

Hot Airventure 6

Hot Airventure 7

WINDWIND

What is Wind?Why the wind?Review of basic concepts

Hot Airventure 8

ASOS Wind InstrumentsWind Vane (left) & Cup Anemometer (right)

Hot Airventure 9

Aerovane Measures wind speed & direction

Hot Airventure 10

BEAUFORT WIND FORCE SCALE[Modern version, Source: Federal Meteorological Handbook I]

Scale Description Land & Sea Observations Knots

0 Calm Smoke rises vertically.Sea surface is like mirror.

< 1

1 Light air Smoke, but not wind vane, shows direction ofwind.Slight ripples on sea.

1-3

2 Light breeze Wind felt on face, leaves rustle, wind vanesmove.Small, short wavelets.

4-6

3 Gentle breeze Leaves and small twigs moving constantly,small flags extended.Large wavelets, scattered whitecaps.

7-10

4 Moderatebreeze

Dust and loose paper raised, small branchesmoved.Small waves, frequent whitecaps.

11-16

5 Fresh breeze Small leafy trees swayed.Moderate waves.

17-21

Hot Airventure 11

BEAUFORT WIND FORCE SCALE (con’t.)Scale Description Land & Sea Observations Knots

6 Strongbreeze

Large branches in motion, whistling heard inutility wires. Large waves, some spray.

22-27

7 Near gale Whole trees in motion.White foam from breaking waves.

28-33

8 Gale Twigs break off trees.Moderately high waves of great length.

34-40

9 Strong gale Slight structural damage occurs. Crests ofwaves begin to roll over. Spray may impedevisibility.

41-47

10 Storm Trees uprooted, considerable structuraldamage.Sea white with foam, heavy tumbling of sea.

48-55

11 Violentstorm

Very rare; widespread damage.Unusually high waves.

56-63

12 Hurricane Very rare; much foam and spray greatly reducevisibility.

>63

Hot Airventure 12

The wind responds to a Difference The wind responds to a Difference in air pressure in air pressure

Hot Airventure 13

BASIC CONCEPTS Air Pressure BASIC CONCEPTS Air Pressure (con’t.)(con’t.)

Hot Airventure 14

Explaining Differences inExplaining Differences in Air Pressure Air Pressure

Low Pressure High Pressure

Hot Airventure 15

Display of Pressure Differences on Display of Pressure Differences on a Weather Map - Isobarsa Weather Map - Isobars

Hot Airventure 16

Isobars -Isobars -- - lines of equal barometric pressurelines of equal barometric pressure- use sea level corrected pressure- use sea level corrected pressure

Hot Airventure 17

US STANDARD ATMOSPHERE, 1976

0

10

20

30

40

50

0 200 400 600 800 1000

AIR PRESSURE [millibars]

ALT

ITU

DE

[km

]

AIR PRESSURE in the Vertical (con’t.)

Hot Airventure 18

As a Sidebar… Altimetry

Since pressure decreases at a “reasonably” known rate of 1 mb decrease per 10 meter rise

or 0.01 inch of Hg per 10 feet, then… pressure altimeters are

barometers made to read in altitude.But...

Hot Airventure 19

Pressure Change with height depends Pressure Change with height depends upon Temperature of columnupon Temperature of column

- (It is really the density!)

Hot Airventure 20

WHY THE WIND? WHY THE WIND? (con’t.)(con’t.)

Reasons for Atmospheric Motions:Reasons for Atmospheric Motions:– Buoyancy Effects Buoyancy Effects oror Dynamic Effects Dynamic Effects

Hot Airventure 21

Hot Airventure 22

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

6:00 12:00 18:00 23:00 5:00

Time

No

rmal

ized

Hea

t F

lux

Daily HeatingDaily Heating

Hot Airventure 23

10

12

14

16

18

20

22

24

26

0 3 6 9 12 15 18 21 24

HOURS CST

TE

MP

ER

AT

UR

E (

deg

F)

January Temperatures - January Temperatures - Madison, WI (1981-90)Madison, WI (1981-90)

Hot Airventure 24

January Wind Speeds - January Wind Speeds - Madison, WI (1981-90)Madison, WI (1981-90)

0

2

4

6

8

10

12

14

3 6 9 12 15 18 21 24

HOURS CST

AV

ER

AG

E W

IND

SP

EE

D [

mp

h]

Hot Airventure 25

July Temperatures - July Temperatures - Madison, WI Madison, WI (1981-90)(1981-90)

55

60

65

70

75

80

85

0 3 6 9 12 15 18 21 24

HOURS CST

TE

MP

ER

AT

UR

E (

deg

F)

Hot Airventure 26

July Wind Speeds - July Wind Speeds - Madison, WI (1981-90)Madison, WI (1981-90)

0

2

4

6

8

10

12

3 6 9 12 15 18 21 24

HOURS CST

AV

ER

AG

E W

IND

SP

EE

D [

mp

h]

Hot Airventure 27

ENERGY TRANSPORT: ENERGY TRANSPORT: CONVECTIONCONVECTION

Hot Airventure 28

LAPSE CONDITIONSTemperature decreases with height

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0. 5. 10. 15. 20.

Temperature [deg C]

Alt

itu

de

[km

]

Hot Airventure 29

ISOTHERMAL CONDITIONS Temperature remains constant with height

0.00.51.01.52.02.53.03.5

0. 5. 10. 15.

Temperature [deg C]

Alt

itu

de

[km

]

Hot Airventure 30

INVERSION CONDITIONS Temperature increases with height

0.00.51.01.52.02.53.03.5

0. 5. 10. 15.

Temperature [deg C]

Alt

itu

de

[km

]

Hot Airventure 31

U.S. STANDARD ATMOSPHERE See Fig. 1.9 Moran & Morgan (1997)

0.

20.

40.

60.

80.

100.

120.

140.

-100. -50. 0. 50. 100.

Temperature [deg C]

Alt

itu

de

[km

]

Troposphere

Stratosphere

Mesosphere

Thermosphere

Tropopause

Stratopause

Mesopause

Hot Airventure 32

Hot Airventure 33

WHY THE WIND? WHY THE WIND? (con’t.)(con’t.)

Reasons for Atmospheric Motions:Reasons for Atmospheric Motions:– Buoyancy Effects Buoyancy Effects oror Dynamic Effects Dynamic Effects

Hot Airventure 34

Air Converging AloftAir Converging Aloft

Hot Airventure 35

Hot Airventure 36

Air Diverging AloftAir Diverging Aloft

Hot Airventure 37

Hot Airventure 38

The SurfaceThe Surface

The “Obvious”– Obstacles to take-off and landing

(e.g., trees, power lines, animals)The Surface and the Winds

– Affects the Boundary Layer wind flow

– Can produce local wind regimes

Hot Airventure 39

Boundary LayerBoundary LayerWhere we liveExtends from surface to approximately

3000 ft. (1000 m)Consists of

– Surface Boundary Layer (30 to 60 ft. & includes Anemometer Level)

– Ekman or Spiral Layer (above 60 ft. to Free Atmosphere)

Hot Airventure 40

Relative Surface RoughnessRelative Surface RoughnessSource: Stull, 1995

Classification LandscapeSmooth Snow-covered fieldsOpen Prairies, grass farm fields, airportsRoughly open Low crops w/ occasional obstaclesVery rough Mixed fields, small woods, orchardsClosed Mature forests, suburbs, villagesChaotic Large towns, irregular forests

Hot Airventure 41

B. EXPLANATIONS of ATMOSPHERIC MOTION

Practical ProblemsHistorical ConceptsForces of Motion & Newton's Laws

Hot Airventure 42

An example of an equation of motionNASA

Hot Airventure 43

PRESSURE GRADIENT FORCEPRESSURE GRADIENT FORCE

Hot Airventure 44

PRESSURE GRADIENT FORCE (con’t.)

Hot Airventure 45

ASSUMPTIONS

For convenience, assume that:For convenience, assume that: Winds are nearly horizontal;Winds are nearly horizontal; Atmosphere is in nearlyAtmosphere is in nearly

“hydrostatic balance” “hydrostatic balance” i.e., air parcels do not accelerate i.e., air parcels do not accelerate upward or downward; upward or downward;

Hot Airventure 46

HYDROSTATIC BALANCE CONCEPT

See Fig. 9.11 Moran & Morgan (1997)

Hot Airventure 47

HORIZONTAL PRESSURE GRADIENT FORCE (con’t.)

Direction is from High to Low pressure!

Hot Airventure 48

HORIZONTAL PRESSURE GRADIENT FORCE (con’t.)

See Fig. 9.1 Moran & Morgan (1997) Magnitude depends on isobar spacing!

Hot Airventure 49

LOCAL WINDSFLOW RESPONDING TO PRESSURE

GRADIENT FORCE - LOCAL WINDS

Assumptions:– Only Pressure gradient force operates;– Results from temperature differences– Acts for short time & short distances.

Examples:– Sea-Land Breeze Circulation– Mountain-Valley Breeze Circulation– City-Country Circulation

Hot Airventure 50

Sea (Lake) Breeze(Graphics from UIUC WW2010)

Hot Airventure 51

VERTICAL PRESSURE GRADIENTS - Dependency on density (temperature)

Hot Airventure 52

Sea (Lake) Breeze (con’t.)

Hot Airventure 53


Hot Airventure 54


Hot Airventure 55


Hot Airventure 56


Hot Airventure 57


(Lake)

Hot Airventure 58


See Fig. 12.2 A Moran & Morgan (1997)

Hot Airventure 59

Land Breeze

Hot Airventure 60

Land Breeze (con’t.)

Hot Airventure 61


Hot Airventure 62


See Fig. 12.2 B Moran & Morgan (1997)

Hot Airventure 63

Mountain BreezeMountain Breeze


Hot Airventure 64

Valley BreezeValley Breeze


Hot Airventure 65

Larger Scale FlowLarger Scale FlowObservation:

Hot Airventure 66

Right with HeightRight with Height

Hot Airventure 67

PRESSURE GRADIENT FORCEPRESSURE GRADIENT FORCE

Hot Airventure 68

Reason for the ProblemReason for the Problem Because the earth turns:

Hot Airventure 69

CORIOLIS EFFECT CORIOLIS EFFECT oror FORCE FORCE (con’t.)

Hot Airventure 70

Hot Airventure 71

Geostrophic AdjustmentGeostrophic Adjustment

Hot Airventure 72

Geostrophic Wind See Fig. 9.12 Moran & Morgan (1997)

Hot Airventure 73

Flow in Friction LayerFlow in Friction Layer

Hot Airventure 74

Variation of Friction Effects with Variation of Friction Effects with HeightHeight

Hot Airventure 75

Right with HeightRight with Height

Hot Airventure 76

Varying effects of Surface RoughnessVarying effects of Surface Roughness

Hot Airventure 77

Hot Airventure 78

Curved Flow

Hot Airventure 79

Features in a Surface Low Features in a Surface Low (Convergence & Ascent)(Convergence & Ascent)

Hot Airventure 80

Features in a Surface HighFeatures in a Surface High (Sinking & Divergence)(Sinking & Divergence)

Hot Airventure 81

Numerical Weather Prediction

Hot Airventure 82


Hot Airventure 83


Hot Airventure 84

My office: Dept. of Atmospheric & My office: Dept. of Atmospheric & Oceanic Sciences Oceanic Sciences

[email protected]@meteor.wisc.edu

Hot Airventure 85

Hot Airventure 86

NORMALIZED DENSITY PROFILEUS STANDARD ATMOSPHERE 1976

0

20

40

60

80

0.0% 20.0% 40.0% 60.0% 80.0% 100.0%

PERCENT OF SEA LEVEL DENSITY

ALTI

TUD

E [k

m]

Hot Airventure 87

UNSTABLE CONDITIONS Compare Environment with DALRWarmer parcel continues upward

-500

0

500

1000

1500

2000

2500

0 5 10 15 20 25 30

Weather 101 and beyond

Documents

Transcript of Weather 101 and beyond