Weather and Climate: Ch. 4 Flashcards
Moving water molecules from a liquid to vapor and back to liquid
Hydrologic Cycle
Solid directly to gas (without passing through liquid state)
Sublimation
What is an example of sublimation?
shrinking of ice or snow
Water vapor directly to a solid
Deposition
What is an example of deposition?
frost
Amount of water vapor in air
Humidity
Measures how near the air is to saturation
Relative Humidity (RH)
Air at 100% relative humidity = …
air is completely saturated
Relative humidity _______
changes
RH varies _____ with temp
inversely
RH ________ as temp drops and __________ as temp rises
increases; decreases
Temp at which water vapor begins to condense
Dew Point Temp
Air reaches saturation at the …
dew point temp
What is a good measure of amount of water vapor in air
Dew Point Temp
High dew points = …
high water vapor content
low dew points = …
low water vapor content
When air temp and dew point are far apart, RH is _____
low
When air temp and dew point are close, RH is ____
high
When air temp and dew point are equal, RH is ________
100% (saturated)
Where are dew points highest?
over Gulf Coast states
Dew points are lowest over _______
interior
Dew point <55:
pleasant
Dew point 56-60:
comfortable
Dew point 61-65:
getting sticky
Dew point 66-70:
uncomfortable
Dew point 71-75:
opppressive
Dew point 76+:
miserable
In cold, polar air, low dew points = ____ air
dry
In cold, polar air, low dew points = _____ RH
high
During winter, RH inside a home can drop to extremely ___ values
low
Low RH inside a home can cause:
dry skin and chapped lips
Temp changes that result from changes in pressure
Adiabatic Temperature Changes
Imaginary volume of air
Parcel
Has no interchange of heat with its surroundings
Parcel
Characteristics of Adiabatic cooling:
- Rising parcel of air expands and cools
- Sinking parcel is compressed and warms
- Clouds form as air rises and cools
Unsaturated parcel of air (RH < 100%)
Dry Adiabatic Rate (DAR)
What is the DAR rate of heating or cooling?
10℃ for every 1000 meters (5.5℉ every 1000’)
DAR is ______
constant
Altitude at which parcel reaches saturation and clouds form
Lifting Condensation Level (LCL)
Rate of temp decrease for a saturated (RH = 100%) parcel of air
Wet Adiabatic Rate (WAR)
What does lifting result in?
cooling, condensation, cloud formation, and release of latent heat
WAR is less than ___ and not _____
DAR; constant
Why is WAR not constant?
due to release of latent heat
WAR average at:
6℃/1000m or 3.3℉/1000’
How do clouds develop?
As an air parcel rises and cools below dew point
What are the 4 triggers for cloud development?
- Orographic Lifting
- Frontal Lifting
- Convergence
- Convection and Clouds
Characteristics of Orographic Lifting
- Air is forced upward by elevated terrain (mountains)
- Air descends leeward slopes (downwind side)
- Mountain ranges create different climates
- Rain Shadow Desert
Air is forced upward by elevated terrain (mountains):
- Ascends windward slopes
- Expands and cools, increasing RH
- Clouds and precipitation can develop (LCL)
Air descends leeward slopes (downwind side):
- Compressed and warms
- Existing clouds vaporize and RH decreases
In orographic lifting, moist climates on ___________ slopes
windward
In orographic lifting, dry climates on ___________ slopes
leeward
Dry conditions that extend many miles downwind of a mountain range
Rain Shadow Desert
Characteristics of Frontal Lifting
- Warmer, less dense air is forced over cooler, denser air
- Cloud development and possible precipitation
- Responsible for most precipitation in mid-latitudes
Characteristics of Convergence
- Horizontal inflow of air that results in vertical lifting of air
- Responsible for clouds and precipitation in a low pressure system
Sea breeze convergence produces thunderstorms in ________ _________
central Florida
In the convection and clouds trigger, unequal surface heating causes pockets of air (thermals) to ____
rise
In the convection and clouds trigger, when warm parcels of air rise above LCL, …
clouds and afternoon showers may form
Stable air = …
parcel resists vertical motion
In stable air, parcel is ______ than surrounding air
cooler
In stable air, parcel more ______ and sinks to its original position
dense
Unstable air = …
parcel rises to an altitude where temp equals its surroundings
In unstable air, parcel is ________ than surrounding air
warmer
Rate of temp change in atmosphere with height
Environment Lapse Rate (ELR)
Characteristics of Environmental Lapse Rate (ELR)
- Air surrounding parcel
- Has to be given to you
What are the 3 types of stability?
- Absolute Stability
- Absolute Instability
- Conditional Instability
Lifting parcel of air is colder and heavier than surrounding air
Absolute Stability
Absolute stability resists _______ motion
vertical
In absolute stability, ELR _____ than WAR or DAR
less
In absolute stability, if parcel is forced to rise, clouds will be…
thin and widespread
There are _____ skies in absolute stability
clear
Stability enhanced by…
- Radiational cooling at night
- Cooling of air mass traveling over a cold surface
- Sinking of air
Rising air parcels are warmer and less dense than surrounding air
Absolute Instability
In absolute instability, ELR _______ than DAR or WAR
greater
When does absolute instability occur?
on warm, humid summer days when solar heating is intense
Absolute instability brings…
pop-up thunderstorms
Instability enhanced by…
- Warming lower atmosphere during day
- Heating cold air mass as it passes over a warm surface
- Upward movement of air
In conditional instability, ELR is ______ WAR and DAR
between
Altitude at which air rises because of its own buoyancy
Level of free convection (LFC)
LFC is a part of…
conditional instability
In conditional instability, stability (unsaturated) occurs _____ cloud
below
In conditional instability, unstable (saturated) occurs _____ cloud base
above
Conditional instability brings ________
thunderstorms
In conditional instability, thunderstorms seldom extend into stratosphere = _______
stable
In conditional instability thunderstorms spread ________ forming an _____ top
horizontally; anvil
