Week 1 through Week 4 Flashcards Preview

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Flashcards in Week 1 through Week 4 Deck (112):
1

what is the atmosphere?

mixture of gas molecules, small suspended particles of solid and liquid, and falling precipitation

2

what is the difference between climate and weather?

Weather refers to the short-term phenomena.
Meanwhile, climate refers to the long-term pattern.

3

Which way does air pressure go?

From high pressure centers to low pressure centers

4

In low pressure areas, what are there?

rising air and clouds

5

In high pressure areas, what are there?

sinking air and clear skies

6

what is density?

mass (kg) per unit volume (m3)

7

As altitude increases, what occurs to density.

As altitude increases, density decreases. This may be expressed in terms of the mean free path, or average distance a molecule travels before colliding with another molecule. Due to compressibility, atmospheric mass gradually “thins out” with height.

8

what occurs when molecules bounce around?

they have a velocity and kinetic energy associated with it.
KE= 1/2 * m * v^2

9

As kinetic energy increases, what does temperature do?

As kinetic energy increases, temperature increases. When the temperature is high, it just means that air molecules are moving slightly faster than usual!

10

What relationship do kinetic energy and temperature have?

direct relationship.

11

what is pressure?

pressure is force divided by unit area

12

Which direction does pressure go in?

Molecules move in all directions, so pressure is exerted in all directions.

13

how is force produced?

the collision of molecules

14

What relationship do density and pressure have?

Direct relationship

15

Suppose that instead we keep the density constant and increase the temperature of the gas. What happens to the pressure of the gas?

Pressure increases as we increase temperature

16

What happens if we increase the temperature of the gas?

Higher temperatures increase kinetic energy, and pressure results from the force cause by collisions of molecules with the surface. If we increase the temperature, there will be stronger collisions and higher pressure.

17

What relationship do pressure and temperature have?

direct relationship.

18

What is the ideal gas law?

pressure= density* gas constant * temperature

19

If density decreases with height, what occurs w/ pressure at low elevations and higher elevations?

pressure decreases most rapidly at low elevations and gradually tapers off at greater altitudes

20

What is in the troposphere?

Layer of virtually all weather processes.
• Warmed at the surface by solar radiation.
• Steady temperature decrease with height.
• The top of the troposphere is called tropopause.

21

What is in the stratosphere?

ozone layer

22

What is in the mesosphere?

coldest layer

23

What is in the thermosphere?

low density, almost no mass

24

Name three ways in which energy/heat transfer can be transferred from one place to another.

Radiation, conduction, convection

25

Radiation

•The transfer of energy by electromagnetic waves.
•Continually emitted by all substances.
•requires no physical medium (can occur through empty space).
example: the sun heats the ground

26

Conduction:

The transfer of energy between objects that are in physical contact.
Example: the ground heats the air

27

Convection:

the transfer of energy between an object and its environment due to fluid motion
example: the warm air rises

28

PGF is related to:

Newton's second law which states acceleration implies action of a net force

29

What relationship to PGF have to distance between isobars?

direct relationship
PGF goes from high to low pressure

30

What is hydrostatic balance?

The balance between the vertical pressure gradient force and the gravitational force

31

What do local imbalances do (in relation to hydrostatic balance)?

Local imbalances create vertical motion
(updrafts and downdrafts)
In zones of sinking air, PGF is less than gravitational force. In zones of rising air, PGF is greater than gravitational force.

32

If you heat a column of air, what will occur?

the density will decrease because heating decreases density. the column contains the same amount of air, but has a lower density to compensate for its greater height.
"warmer atmosphere is deeper"

33

What can the height of isobaric surfaces show?

Constant pressure surfaces of cooler air will be lower in altitude than those of warmer air.

34

High heights of isobaric surfaces (e.g., 500-mb surface) correspond to ______ pressure on a nearby constant- height surface.

high

35

Is PGF the only force affecting the winds?

No, there are additional forces affecting winds.

36

How are winds initiated?

PGF

37

Once air is in motion, two additional forces come into play which are:

1. Coriolis force–Not a “real” force, but rather an effect due to observations made in a rotating reference frame
2. Frictional force-A force of opposition which slows air in motion

38

Explain the Coriolis force

1. The Coriolis force produces an apparent deflection of moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
2. The Coriolis force is zero at the equator and increases with increasing latitude
3. The Coriolis force acting on any object increases with object’s speed
4. The Coriolis force changes only the direction of the object, not its speed

39

Explain frictional force

A force of opposition which slows air in motion.
• Initiated at the surface.
• Important for air within 1.5 km (1 mi) of the surface (the planetary boundary layer), and negligible aloft (the free atmosphere).
• Friction reduces wind speed, so it also reduces Coriolis force.

40

Does friction only reduce wind speed or does it reduce wind speed and the coriolis force?

Friction reduces wind speed, so it also reduces Coriolis force.

41

An airplane is flying forward at constant speed. At a given moment the forces acting on the airplane are such that Thrust is balanced by Air Friction, but Lift is smaller than the Weight. How is the airplane motion going to respond?

Airplane will continue moving forward at the same speed, but will accelerate downward

42

What is PGF caused by?

PGF caused by differential heating of equator and poles

43

What is geostrophic balance?

PGF and Coriolis Force are in balance, so the wind does not change anymore!

44

Hydrostatic balance (in the vertical)

PGF=gravitational force

45

Geostrophic balance (in the horizontal)

Coriolis Force = PGF (also, there is wind pointing to the right and the wind is proportional to the coriolis force)

46

If wind is faster than geostrophic balance, what is it called?

supergeostrophic

47

If wind is slower than geostrophic balance, what is it called?

subgeostrophic

48

Upper level winds (no friction)

PGF=Coriolis (with wind going to the right)

49

Near-surface winds (with friction)

PGF > Coriolis
Friction goes to left, wind goes to right

50

What occurs to winds near the surface?

•Winds near the surface slow due to friction and therefore are not parallel to the isobars
• Coriolis deflection still occurs but it is reduced
• Winds cross the isobars directed into low pressure regions

51

What are cyclones?

•Low pressure centers (cyclones), have counterclockwise airflow in the Northern Hemisphere
•This occurs as air converges to the low pressure areas at the surface and is deflected by Coriolis force

52

What are anti-cyclones?

•High pressure centers (anticyclones), have clockwise airflow in the Northern Hemisphere
•This occurs as air diverges from the high pressure areas at the surface and is deflected by Coriolis force

53

What are troughs and ridges?

-In the upper atmosphere, low and high pressure systems occur as elongated areas called troughs (low pressure) and ridges (high pressure)
-Pressure is distributed as cyclones and anticyclones at the surface and gradually give way to ridges and troughs in the upper atmosphere

54

What is evaporation?

Molecules escape from liquid into the overlying volume as water vapor
Evaporation rate is proportional to the temperature of the liquid

55

What is the relationship between evaporation and the temperature of the liquid?

direct relationship

56

What is condensation?

Water vapor molecules randomly collide with the water surface and bond with adjacent molecules

57

What is the relationship between condensation and the amount of vapor?

Direct relationship

58

When evaporation rate = condensation rate, the system is..

in a state of equilibrium called saturation

59

What is "amount of water vapor"?

humidity

60

What are several ways to quantify humidity?

vapor pressure, specific humidity, mixing ratio

61

What is vapor pressure?

pressure exerted on the atmopshere by water vapor molecules (mb)

62

what is specific humidity?

mass of water vapor in a unit mass of air (g/kg)

63

what is mixing ratio?

Mixing ratio: mass of water vapor in a unit mass of dry air (g/kg)

64

We know that evaporation rate increases with temperature. How does temperature affect vapor pressure at saturation?

Vapor pressure at saturation increases with increasing temperature

65

Considering that the rate of evaporation depends on temperature and the rate of condensation depends mostly on how many water vapor molecules are in the air, what occurs if we raise the temperature?

-Evaporation rate increases
-Need higher "humidity" for condensation rate to match evaporation rate – saturation vapor pressure increases!

66

Clausius-Clapeyron Curve

“Water-holding capacity” of the atmosphere increases by about 7% for every 1 °C rise in temperature
Shows the equilibrium curve. At the curve, it is clouds. To the left of the curve is liquid, and to the right of the curve is all vapor.

67

What is relative humidity?

amount of water vapor in relation to saturation point
RH = (vapor pressure/saturation vapor pressure) * 100%

68

Can the term be used to compare moisture content at different locations having different temperatures?

Because of temperature dependency, the term cannot be used to compare moisture content at different locations having different temperatures

69

When does the highest RH occur?

occurs in the morning, during the coolest time of the day

70

When does the lowest RH occur?

occurs in late afternoon, during the warmest time of the day

71

What is dew point temperature?

temperature to which air must be cooled to reach saturation (without changing vapor pressure)

72

What do infrared satellites cover?

Cloud-top temperature
• High clouds are white
• Low clouds are grey
• Dry areas are hard to identify

73

What do water vapor satellites occur?

• Uses infrared band
affected by water vapor
• Dry air stands out as dark regions

74

What are processes that cause saturation?

Three possible mechanisms:
1. The addition of water vapor
2. Cooling the air to dew point (most clouds)
3. Mixing cold air with warm moist air

75

Suppose we do our “saturation” experiment. Assume the air, the container, and the liquid water are all at the same temperature. Where is the condensation going to occur?

At the liquid surface and at the walls of the container

76

What are the two ways of nucleating water from vapor?

Homogeneous nucleation & Heterogeneous nucleation

77

What is homogeneous nucleation?

only water vapor molecules coming together to form water (effect of curvature, requires supersaturation with RH=400%, so it never happens in practice)

78

What is heterogeneous nucleation?

water vapor molecules adhere to a solid surface (hygroscopic aerosols) on a condensation nucleus (cloud condensation nuclei, CCN)

79

How do you nucleate ice from liquid water?

Pure water must be supercooled to T < -20oC in order to get it to freeze
• Ice crystal formation requires ice nuclei, a rare temperature-dependent substance similar in shape to ice (six-sided).
• Examples: clay, ice fragments, bacteria, etc.
• Ice nuclei become active at temperatures below -4°C

80

What are two processes that can cool air to reach saturation?

Adiabatic and diabatic processes

81

What is a diabatic process?

Changes in temperature caused by heat transfer into or out of the air parcel

82

What is an adiabatic process?

Changes in temperature caused by expansion or contraction due to changes in pressure
(no heat transfer)

83

What is the adiabatic lapse rate?

Rate at which temperature decreases with increasing altitude
LR= (final temp - initial temp/final height - initial height)

84

What is the DALR?

"Dry” adiabatic lapse rate (Dry = air + water vapor)

85

What is the SALR?

SALR - “Saturated” adiabatic lapse rate
(Saturated = air + water vapor + liquid water droplets)

86

What causes Santa Ana winds?

Synoptic pattern: high pressure system (anticyclone with clockwise rotation) over the Great Basin
-Adiabatic heating is the key for the high temperature and the low relative humidity
-Air descending from the high deserts:
• warms by adiabatic compression
• temperature increases reduces RH (by increasing saturation vapor pressure)

87

What is dew?

liquid condensation on surface often occurring during the early morning hours
• Surface air becomes saturated and condensation forms on objects acting as condensation nuclei

88

What is frost?

similar to dew except that it forms when surface temperatures are below freezing.
• Deposition (vapor to solid) occurs instead of condensation.

89

What is frozen dew?

Frozen dew occurs when normal dew formation processes occur, followed by a drop in temperature to below freezing.
• Causes “black ice” on roadways

90

What is fog?

surface cloud when air either cools to the dew point, has moisture added, or when cooler air is mixed with warmer moister air.

91

what types of fogs are there?

radiation fog, advection fog, and upslope fog

92

what type of fog occurs in SF and Santa Monica?

Advection fog

93

How can we calculate
the height of cloud formation?

LCL = (Tsfc- DPsfc)/ 8

94

What are mechanisms that lift air?

orographic lifting
frontal lifting
surface convergence
convection

95

What causes convection?

vertical motions caused by buoyancy

96

what is buoyancy

An air parcel that is more dense than its environment sinks, while an air parcel that is less dense rises

97

What are the three stabilities?

stable, indifferent, unstable

98

How do we find out the stability?

In the atmosphere we characterize stability by comparing lapse rates.

99

If the air parcel is “dry”, what do we compare the DALR with?

If the air parcel is “dry”, we compare the DALR with the ELR

100

If DARL>ERL1
at new position Tp < Te, the air parcel will...

the air parcel sinks back to original position and equilibrium is STABLE

101

If DARL Te, the air parcel will...

the parcel rises away from original position and equilibrium is UNSTABLE

102

If DARL=ERL3
at new position Tp = Te, the air parcel will,

the air parcel stays at new position and equilibrium is NEUTRAL

103

If the air parcel is saturated, how do you calculate its stability?

Use SALR

104

What Determines the ELR?

1. Heating or cooling of the lower
atmosphere
2. Advection of cold and warm air at different levels
3. Advection of an air mass with a
different ELR

105

What type of clouds are there?

stratus, cumulus, nimbus

106

Stratus clouds:

Wide flat layer of clouds (stable ELR, no vertical motion)

107

Cumulus clouds:

Puffs/piles of clouds (unstable ELR, vertical motion)

108

Nimbus clouds:

Precipitating cloud (i.e. rain)

109

High clouds: cirrus

Bases above 19,000 ft
• Mostly ice crystals
• Wispy appearance (low water content)

110

Middle clouds (Alto)

• Bases between 6,000 and 19000 ft
• Mostly liquid droplets

111

Low clouds

• Bases below 6,000 ft
• Mostly liquid droplets

112

Vertical clouds (Cumuliform)

•Can have violent updrafts, heavy precipitation, and large temperature differences