Weather & Climate, Unit 2

Front 1

What is relative humidity?

Back 1

Relative humidity is the ratio of the air's actual water vapor content compared with the amount of water vapor required for saturation at a given temperature. As a %, indicates proximity to saturation.

Front 2

What two things can influence relative humidity?

Back 2

1) adding/subtracting moisture to the air
2) changing the given temperature

Front 3

In the real atmospheric environment, temperature changes affects RH through what 3 things?

Back 3

1) simple daily temperature changes
2) advection
3) convection
Remember, air temperature and RH have an inverse relationship.

Front 4

What is dew point?

Back 4

Dew point is the temperature to which a parcel of air would need to be cooled to (assuming no change in air pressure or moisture content) in order for the given parcel of air to reach saturation.

Front 5

Dew point is ALWAYS ___ than or ____ to temperature.

Back 5

Dew point is ALWAYS less than or equal to temperature. If they are the same, the air is saturated and RH is at 100%

Front 6

1) What are some things that we use to measure humidity?

Back 6

Dew Cell: directly measures the air's actual water vapor pressure. Chilled Mirror Technology: cooling a surface (mirror) in contact with a sample air until condensation occurs.

Front 7

2) What are some things that we use to measure humidity?

Back 7

Sling Psychrometer: uses dry/wet bulb thermometer. the dry bulb measures actual air temp. wet bulb, after wetting , evaporative cooling yields a wet bulb temp (this is NOT the dew point)

Front 8

3) What are some things that we use to measure humidity?

Back 8

Hair Hygrometer: based on the fact that hair strands will slightly lengthen with higher RH and shrink with lower RH. The stands are attached to an index dial.

Front 9

4) What are some things that we use to measure humidity?

Back 9

Electronic Hygrometer: an electrical conductor coated with a moisture-absorbing chemical; the passage of current varies as RH varies. used in radio/rawinsondes

Front 10

5) What are some things that we use to measure humidity?

Back 10

Infrared Hygrometer: measures the amount of infrared energy absorbed by water vapor ina given sample of air. this is used in wearher satellites.

Front 11

Atmospheric stability refers to the state of ______ of the atmosphere.

Back 11

Atmospheric stability refers to the state of equilibrium of the atmosphere. Stable equil: air is sinking. Unstable equil: air is rising.

Front 12

How do we determine atmospheric stability?

Back 12

To determine atmospheric stability, we look at the temperature of a parcel of air as it rises and/or sinks in the atmosphere and compare that temperature to the temperature of the surrounding environment.

Front 13

Before we can determine atmospheric stability, we must determine the rate of ______ ____ within a parcel of air as it rises or sinks.

Back 13

Before we can determine atmospheric stability, we must determine the rate of temperature change within a parcel of air as it rises or sinks. A parcel of air rising --> expands & cools. A parcel of air sinking --> compresses & sinks.

Front 14

The rate at which air cools/warms depends upon the air's _____ ______, and whether the air is ______ or not.

Back 14

The rate at which air cools/warms depends upon the air's mositure content, and whether the air is saturated or not.

Front 15

What is an adiabatic process?

Back 15

An adiabatic process is when a given parcel of air expands/cools or compresses/warms, with NO interchange of heat with its outside environment.

Front 16

What is a diabatic process?

Back 16

A diabatic process is when a given parcel of air expands/cools or compresses/warms, WITH an interchange of heat with its outside environment.

Front 17

As air parcels rise/sink in the atmosphere, we assume _____ cooling/heating process.

Back 17

As air parcels rise/sink in the atmosphere, we assume adiabatic cooling/heating process.

Front 18

What is the dry adiabatic rate?
What is the wet adiabatic rate?

Back 18

Unsaturated rate: 5.5 F / 1000 ft (possible with saturated air at the poles)
Saturated rate: 3.3 F / 1000 ft (releasing latent heat of condensation)

Front 19

The overall atmospheric temperature profile, ie how quickly it actually cools with height, can determine _____.

Back 19

The overall atmospheric temperature profile, ie how quickly it actually cools with height, can determine stability.

Front 20

When the ELR (environmental lapse rate) is > the DALR (dry adiabatic lapse rate: 5.5 F / 1000ft), the atmosphere is said to be _______.

Back 20

When the ELR (environmental lapse rate) is > the DALR (dry adiabatic lapse rate: 5.5 F / 1000 ft), the atmosphere is said to be "absolutely unstable." Environment air is cooling faster with hieght than rising parcel.

Front 21

When the MALR (3.3 F / 1000ft) < ELR < DALR (5.5 F / 1000ft), the atmosphere is said to be ________.

Back 21

When the MALR (3.3 F / 1000ft) < ELR < DALR (5.5 F / 1000ft), the atmosphere is said to be "conditionally unstable."

Front 22

When the ELR (environmental lapse rate) is < the MALR (wet adiabatic lapse rate: 3.3 F / 1000ft), the atmosphere is said to be _______.

Back 22

When the ELR (environmental lapse rate) is < the MALR (wet adiabatic lapse rate: 3.3 F / 1000ft), the atmosphere is said to be "absolutely stable."

Front 23

If the ELR < MALR or DALR, then the atmosphere must be _______.

Back 23

If the ELR < MALR or DALR, then the atmosphere must be stable.

Front 24

Air resists change. Stability in the atmosphere is enhanced by what 3 factors?

Back 24

1) radiational cooling of the earth's surface after sunset; 2) cooling of an air mass from below as it traverses a colder surface (think of a warm front over snow-covered ground); 3) subsidence of an air column.

Front 25

Instabiity is enhanced by what 4 factors:

Back 25

1) intense solar heating; 2) heating of an air mass from below as it traverses a warmer surface; 3) mechanical lift: forceful lifting of air (orographic & frontal); 4) upward motion with surface air convergence.

Front 26

Dew: water that has ______ onto objects near the ground when the _______ of those objects has cooled below the ___ _____ temperature of the surrounding air.

Back 26

Dew: water that has condensed onto objects near the ground when the temperature of those objects has cooled below the dew point temperature of the surrounding air.

Front 27

What is the difference between frozen dew and frost?

Back 27

Frozen dew is what happens when the air temperature falls below freezing after dew has formed. Frost actually goes from vapor to solid before deposition.

Front 28

What is frost?

Back 28

Frost is a covering of ice crystals produced by deposition on exposed surfaces when the air temperature falls below the freezing point AND the temperature of the exposed objects fall below the surrounding air's dew point (or frost point) temperature.

Front 29

How do most clouds form?

Back 29

Most clouds form as air rises, expands and cools.

Front 30

What are the two requirements for condensation to occur (cloud formation)?

Back 30

1) the air must become saturated; 2) there must be a surface on which condensation can occur, ie condensation nuclei

Front 31

What are 4 cloud formation processes?

Back 31

1) surface heating & free convection; 2) topographic lift (mtns, Balcones Fault...); 3) widespread lifting (ascent) due to surface convergence; 4) uplift along weather fronts (moisture must be present!)

Front 32

What is fog? Name 4 types.

Back 32

Fog is a cloud with its base at the Earth's surface.
Radiation, Advection, Evaporation/Mixing, Upslope

Front 33

What is radiation fog?

Back 33

When you radiate heat from earth's surface and you reach dew point temperature. Prefers wind 1-3mph. This is the fog that tends to "burn" off when the sun comes up and raises air temperature.

Front 34

What is advection fog?

Back 34

Fog that is moving horizontally. Think of the San Francisco and how the fog just pours in.

Front 35

What is evaporative/mixing fog?

Back 35

This is the fog that occurs when it is very cold outside and you breathe, which puts moisture into the air. Same thing occurs with Barton Springs in the winter.

Front 36

What is slope fog?

Back 36

Also known as the fog within cloud forests; it is the for on mountain slopes.

Front 37

In 1803, English Nationalist, ____ _______ employed latin words to describe clouds as they appear to ground observers.

Back 37

In 1803, English Nationalist, Luke Howard employed latin words to describe clouds as they appear to ground observers.

Front 38

Latin Roots: Stratus, Nimbus, Cumulus, Cirrus

Back 38

Status (stable): layered
Nimbus (very unstable): "violent rain"
Cumulus (unstable): "heap"
Cirrus (stable): "curl of hair"

Front 39

Give the "octas" of cloud coverage. And remember, perception is cummulative from the ground up.

Back 39

0/8 CLR
1/8 - 2/8 FEW
3/8 - 4/8 SCT
5/8 - 7/8 BKN
8/8 OVC

Front 40

Geostationary satellites are about ______ miles above the ground and show images of the same geographic area _________.

Back 40

Geostationary satellites are about 22,500 miles above the ground and show images of the same geographic area continuously.

Front 41

Polar orbiting satellites are about ____ miles above the ground and constantly passing over the _____.

Back 41

Polar orbiting satellites are about 532 miles above the ground and constantly passing over the poles.

Front 42

What do the following kinds of satellites tell us: WV, IR, VI, LP, IM?

Back 42

IM-image; LP-loop; VI-visible satellite imagery; IR-infrared --> measure cloud-top temperature; WV-water vapor --> indicates atmospheric in mid/high upper levels

Front 43

Precipitation formation leading to deposition is a result of what two processes?

Back 43

Collision-Coalescence Process (warmer temperature process)
Bergeron Process (Colder temperature process

Front 44

What are three standard instruments for measuring rainfall?

Back 44

Standard Raingauge, Tipping Bucket Rain Gauge, Weighing Type Rain Gauge

Front 45

What are three rules to follow when measuring snowfall?

Back 45

1) avoid areas with drifting/blowing snow; 2) away from trees/buildings; 3) measure three places with a ruler and average

Front 46

What is the equivalancy ratio for water to snow?

Back 46

Average 1" liquid rainfall = 10" snowfall, though varies greatly

Front 47

What are 5 forms of weather/precipitation modification?

Back 47

1) seeding of clouds for more rain; 2) fog dispersal; 3) hail suspension; 4) tropical cyclone suppression; protection from colder temperatures

Front 48

What is air pressure?

Back 48

Air pressure is the weight of the air above a given surface.

Front 49

As you climb in elevation, there are ____ air molecules above you, therefore, air pressure ______ ______ with height (and very rapidly).

Back 49

As you climb in elevation, there are fewer air molecules above you, therefore, air pressure ALWAYS decreases with height (and very rapidly).

Front 50

What are 3 common High Clouds?

Back 50

Cirrus (Ci)
Cirrocumulus (Cc)
Cirrostratus (Cs)
think white and ~20K ft

Front 51

Ci

Back 51

Cirrus: ~20K ft high, white, wispy streamers (mares tales), usually fair-weather, though may indicate an approaching storm, does NOT block the sun

Front 52

Cc

Back 52

Cirrocumulus: ~20K ft, white, very small cumulus puffs (mackerel sky), smaller than thumb, can indicate instability

Front 53

Cs

Back 53

Cirrostratus: ~20K ft, white, stratified cirrus, often covers entire sky, sun/moon CAN be seen with halo effect, shadows are cast, fair weather clouds

Front 54

What are two Middle Clouds?

Back 54

Altocumulus (Ac)
Altostratus (As)
think gray and 6,500-20,000 ft

Front 55

Ac

Back 55

Altocumulus: gray, puffy, gray (not uniform), dark, bases 8,000-12,000 ft, same size as thumb, "rising castles", indicate instability

Front 56

As

Back 56

Alstostratus: gray to blue (never white), cloud often covers entire sky, base 8,000-12,000 ft, NO HALO NO SHADOW, sun will be dull round disk

Front 57

What are 3 common Low Clouds?

Back 57

Stratus (St)
Stratocumulus (Sc)
NImbostratus (Ns)

Front 58

St

Back 58

Stratus: uniform gray, stratified, w/in 2,000 ft, can cover portions of entire sky, only light rain/drizzle, cause fog when on ground, uniform cloud bases

Front 59

Sc

Back 59

Stratuscumulus: white-dark gray, lumpy patches, little to no precipitation expected, larger than thumb

Front 60

Ns

Back 60

Nimbostratus: dark, gray wet-looking, continuously falling precipitation (light to moderate; never heavy), NO thunder/lightning/hail, bases is almost impossible to identify, NO sun/moon visible

Front 61

What is virga?

Back 61

Virga is when clouds precipitate but water evaporates before reaching the ground.

Front 62

What are 2 clouds of vertical extent?

Back 62

Cumulus (Cu)
Cumulonimbus (Cb)
These are dependent upon stability!

Front 63

Cu

Back 63

Cumulus: detached domes/towers, dense and well defined, flat bases with bulging top, genereally fair weather, indicate rising air motions, surface to 7,500 ft

Front 64

What are 4 kinds of cumulus clouds associated with instability?

Back 64

Cumulus Humilis: limited instability
Moderate, Towering, Building Cumulus (all Cumulus Congestus): sign that the air is a bit more unstable

Front 65

Cb

Back 65

Cumulonimbus: large, towering, thunder, lightning and rain, 2,000 up to 70,000 ft

Front 66

Lenticularis
Fractus
Humilis ----->
Congestus
Undulatus

Back 66

Lens like (Ac)
Broken or fractured (St, Cu, Ns)
Of small size (Cu)
To pile up; become congested (Cu)
Having waves (Ac)

Front 67

Translucidus
Mammatus
Pileus ------->
Castellanus
Contrails

Back 67

Sun to shine through (Cs)
Bag/pouch like; Mammary (Cb)
Cap (Ac)
Small Castle (Ac)
Condensation trails

Front 68

Define drizzle

Back 68

very small, numerous, uniformly dispersed, apear to float, often associated with low stratus/fog, drizzle < 0.02in

Front 69

Intensity of drizzle

Back 69

very light- surface never completely wet
light- trace to .01" /hr
moderate- .01"-.02" /hr
heavy- .02"-.04" /hr

Front 70

Define rain

Back 70

precipitation in the form of liquid water drops, which have diameters > 0.02 in (may be less if widely scattered). usually from Cb or Ns.

Front 71

Intensity of rain

Back 71

very light- sct drops don't cover entire surface
light- 0.10" /hr (< .01" in 6 min)
moderate- 0.11"-0.3" /hr (< .03" in 6 min)
heavy- > 0.3" /hr in 6 minutes

Front 72

Define freezing rain

Back 72

rain that falls in liquid form but freezes upon impact to form a glaze. state is between rain and ice pellets

Front 73

Define freezing drizzle

Back 73

drizzle that falls in liquid form but freezes upon impact (same as freezing rain but droplets are smaller)

Front 74

Define ice pellets

Back 74

transparent/translucent pellets of ice, < 0.2" in diameter, tis the re-freezing of precipitation. requires a deep, cold atmosphere

Front 75

Define snow

Back 75

white/translucent ice crystals, remian frozen during entire descent, can be up to 0.8" in diameter, requires a deeper, colder atmosphere

Front 76

Intensity of snow

Back 76

light- visibility is > 5/8 mile
moderate- visibility 5/16 - 5/8 mile
heavy- visibility < 5/16 mile

Front 77

Define hail

Back 77

Hail is precipitation in the form of balls or lumps of ice, ALWAYS produced by convective clouds (cumulonimbus), diameter > 0.2"

Front 78

If you have 0.75" hail coming from clouds, you've got a _____.

Back 78

If you have 0.75" hail coming from clouds, you've got a thunderstorm caused by a cumulonimbus cloud.