Exam II Flashcards
About what percent of Earth’s water can be found in the oceans?
70%
The amount of water vapor in the air (by volume) usually doesn’t exceed…?
4%
Relative humidity indicates the…?
Nearness to saturation.
Assume that the actual vapor content of the air remains constant over the course of the day. How does the relative humidity at 2pm probably compare to the RH at 5am?
The RH at 2pm is lower.
An instrument used to measure relative humidity?
Hygrometer.
The most common reason why dew forms on the grass at night?
Temperatures are coolest on the grass.
RH depends on the water vapor present in the air and…?
Temperature.
A radiation fog requires what in order to form?
High RH and clear nighttime skies.
The type of fog produced when cold air moves over a warm, moist surface?
Steam fog.
Which type of fog occurs during nights when skies are clear and RH is high?
Radiation fog.
When warm moist air moves over a cold surface, _____ fog may result?
Advection.
As the temperature of the air is reduced to its dew point, what’s most likely to occur?
Condensation.
An air parcel rises over a mountain and cools adiabatically. Which lifting mechanism has acted on this parcel?
Orographic lifting.
Which type of lifting mechanism results from warm air lifting over cold air?
Frontal wedging.
A stable atmosphere is one in which…?
Vertical motions are resisted.
Collision-coalescence is the predominant cause of precipitation in this region?
The Tropics.
Most of the precipitation that falls in the middle latitudes is formed by…?
The Bergeron Process.
The collision-coalescence process occurs when the entire cloud is?
Above freezing.
The raindrops that fall to Earth from a warm cloud contains about 1 million times the water in a typical cloud droplets. This growth from cloud droplets to raindrops occur mainly because of…?
The collision-coalescence process.
The largest form of precipitation is…?
Hail.
Sources of condensation nuclei?
Forest fires, wind erosion of soil and dust from industries and agriculture.
Rain droplets are initially what shape?
Spherical.
The process by which supercooled water droplets freeze onto falling ice crystals is called?
Riming.
Freezing rain…?
Requires a layer of cold air near the surface.
In the western part of N. America, snowfall distribution is primarily dependent upon what?
The presence of major north-south mt. ranges.
Coldest cloud type?
Cirrus.
A raindrop that freezes before reaching the ground is called?
Sleet.
Orographic uplifting is usually associated with the rising air…?
Along the windward side of mt.
Globally, annual precipitation amounts are highest in the…?
Tropical rain forests of S. America and Africa.
Lake effect snowfall requires…?
That the lake be relatively warm.
Lake effect precipitation?
Is caused by the wind blowing over an unfrozen lake surface.
Supercooled water is water which is…?
Still liquid at temperatures below 0 degrees C.
Hail is most commonly associated with?
Cumulonimbus clouds.
The wind belts between 30 and 60 degrees are the…?
Westerlies.
The doldrums refer to the same region as the?
Intertropical Convergence Zone.
The Hadley cell…?
Originates with strong solar heating at the equator.
The Subtropical High often causes…?
Dry, desert-like conditions.
The Bermuda is associated with the…?
Development of El Niño.
Describe the rainfall distribution at a station located along the equator?
Adequate precipitation all year round.
The Sahara and Australian deserts (among others) are associated with which pressure belt?
Subtropical High.
Chinook (foehn) winds are warm because?
They are warmed adiabatically as they sink downslope.
Summertime wildfires in Cali are fanned by…?
The Santa Ana winds.
Most of the US is situated in which zone of prevailing winds?
Trade Winds.
The term Hadley Cell applies to…
0 to 30 degrees latitude.
Surface high pressure zones are usually associated with…?
Clear or nearly clear weather.
The region where the northeast trades meet the southeast trades is known as the…?
ITCZ
The definition of the word monsoon means…?
Seasonal wind shifts.
The process that brings cold, nutrient-rich water to the surface along the coasts of Peru and Ecuador is called..?
Upwelling.
El Niño events are characterized by?
Pooling of unusually warm water in the eastern tropical Pacific.
A cT air mass is…?
Warm & dry.
The ____ air mass provides much of the moisture for precipitation in the central and eastern US?
mT
Lake effect snow is associated with the ____ air mass.
cP
The area where an air mass originates is called a…?
Source region.
The cP air mass in N. America originates in?
Canada.
Hydrologic cycle?
Movement of water through the atmosphere.
Saturation?
Equilibrium between evaporation & condensation.
Deposition?
The reverse process of changing a vapor to a solid.
Humidity?
Refers to the amount of water vapor in the air.
Dew Point Temperature?
A measure of actual moisture content.
Upslope Fog?
Created when RH air moves up a sloping landform or up the steep slopes of a mt.
The upward flow causes the air to expand and cool adiabatically.
Ex.
Rocky Mt.
Cool air…?
Expands.
Heated air…?
Compresses.
WAR (wet adiabatic rate)
When air cools; saturated `
5 degrees C/ 1000 m or 3.3 degrees F/ 1000 ft.
DAR (dry adiabatic rate)
Unsaturated air cool at a rate of 10 degrees C/ 1000 m or 5.5 degrees F/ 1000 ft.
LCL (lifting condensation level)?
Condensation is triggered when air rises high enough to reach saturation point and clouds form.
Frontal wedging?
Warm and cold air collides = fronts; cooler denser air acts as a barrier which the warmer, less dense air rises.
Convergence?
Converging horizontal air flow results in upward movement.
Localized convectional lifting?
Unequal surface heating causes localized pockets of air to rise.
Stable air?
Resist vertical movement.
Unstable air?
Rises due to buoyancy.
Environmental Lapse Rate (ELR)?
The actual temperature of the atmosphere.
Supercooled water?
Water existing in the liquid phase with a temperature less than 0 degrees C.
Freezing rain?
A form of precipitation in which rain droplets freeze as they fall below an inversion and pass into the air having a temperature below 0 degrees C.
Zontal-flow?
Flow parallel to the lines of latitude.
Meridional-flow?
Flow parallel to the lines of longitude.
Polar cell (thermal)?
Driven by heating at 50 degrees latitude and cooling at the poles (N. Pole - 30 degrees).
Ferrel (dynamical)?
Dynamical response to Hadley and Polar cells. (60 degrees - 30)
Jet Stream?
Found in the upper troposphere above the polar front, a result of the string temperature contrast across the front.
Rossby waves?
Great waving undulation within the Westerly flow of geostrophic winds instrumental in the transport of energy and storm development from subtropical regions to high latitude.
Monsoon?
Seasonal reversal in surface winds.
Sea breeze?
Stronger in the afternoon (caused by differential heating of land/sea).
Land breeze?
Cooler air over land flow offshore over warm water air is lifted over the water.
Valley breeze?
Gains heat energy rapidly during the day (warm air rises upslope during the day).
Mountain breeze?
Occurs when mt. air cools rapidly at night; cooler air subsides down slope into the valley during the night.
Air mass?
An immense body of air (1200 plus km by several km thick).
How is air mass classified?
The latitude of the source region (temp.) and the nature of the surface (moisture) in the area of origin.
cA (continental Arctic) =
Very cold and very dry.
cP (continental Polar) =
Cold and dry.
cT (Continental tropic) =
Warm and dry.
mA (marine arctic) =
Cold and wet.
mT (marine tropic) =
Warm and wet.
