Moisture Flashcards
Air Mass
- pool of air, same humidity and temperature
- 1000 km^2
How are air masses classified?
by temperature and humidity at source region
Atmospheric River
- 400-600 km wide, 1000 km long
- band of wind transporting moisture
- 30-50% of annual precipitation
Sea Breeze
- day
- cool ocean breeze, high pressure
- flows onto warm land (low pressure)
Land Breeze
- night
- cool land breeze in high pressure area
- flows over to warm, low pressure ocean
Air humidity
- amount of water vapour in the air
- determines rate of condensation, cloud formation, and precipitation
- depends on temperature
Vapour Pressure
-share of air pressure made up by water vapour molecules at given T
Saturation
- evaporation rate = condensation rate
- air is in equilibrium with liquid
Saturated Vapour Pressure
- saturated air’s state
- depends directly on T
- 10 degree increase doubles SVP
Warm Tropical air SVP
- lots of water vapour, releases latent heat
- powers the tropical storms
Cold Polar SVP
- transfers less moisture
- polar deserts created
Mixing Ratio
mass of water vapour per unit mass of dry air
specific humidity
mass of water vapour per unit mass of moist air
Max specific humidity means..
max water vapour per unit air mass
Relative humidity =
amount water vapour in air/max possible at given T *100
Dew Point
-temperature for air mass to become saturated
Condenstation Causes
- addition of water vapour in the air
- cooling of air
Diabatic
physical exchange of heat
Adiabatic
no physical exchange of heat
air stability
-temperature difference between inside air parcel and air surrounding parcel
Atmospheric Stability
-tendency of an air parcel to remain in place / change positions
Stable Atmosphere
-air resists upward displacement
Unstable Atmosphere
-air continues to rise until it reaches it’s own temperature and humidity conditions
Rising air causes
clouds and precipitation
Warm air, Cool Air stability
warm air is unstable
cool air is stable
Dry Adiabatic Lapse Rate, Wet Rate, and Environmental Rate
10 degree/km
6 degree/km
12 degree/km
Cloud Formation (simple steps)
- cooling -> air rises
- cools to dew point
- saturates
- condensation occurs
Cloud (buildup)
buildup of moisture droplets and ice crystals
Cloud Condensation Nuclei
- 10^-4 mm
- comes from volcanoes, ocean, forest fires, dust, clay and silt, combustion products
Cloud drop size vs. Rain drop size
- cloud drop 0.001 mm - 0.2 mm
- rain drop 0.4 mm to 4 mm
Drop Growth : Collision
- droplet T> 0 degrees C
- fall, collide, and coalesce
Drop Growth: Ice Crystal Growth
- T <0 degrees C for ice and drops
- water around drops, vapour pressure gradient towards ice
- net flow, accretion
Clouds: Low
- stratus, cumulus
- cool atmosphere allows low formation
- condensation and precipitation
Cloud: Vertical
- cumulus and cumulonimbus
- high moisture content
- possible precipitation
Stratocumulus Cloud
- warm atmosphere limits condensation
- clear weather
Cloud: Upper
- cirrus
- scarcity of moisture
- limits condensation
Fog (General)
Cloud layer on the ground, when Tdew = Tair
Fog: Radiation
- radiational cooling
- calm clear nights
Fog: Advection
-warm air passes over cool surfaces
Fog:Steam
cool air passes over warm water
Fog: Orographic
air is forced over physical barrier
Fog: Frontal
lifting associated with fronts
Inversion (general)
-warm air over cold surface
Inversion: Radiation
-occurs when evening air is still and no clouds are available to trap heat
Inversion: Sea Breeze
-windward coasts by cold ocean currents
Inversion: Subsidence
Subsiding air undergoes adiabatic heating aloft, air in contact with surface stays cooler
