Moisture in the Atmosphere Flashcards
What is absolute humidity?
The amount of water vapor in the atmosphre
What is relative humidity?
The ratio of the amount of water vapor in the atmosphere compared to the amount the air can hold at that temperature.
How is relative humidity determined?
Using instruments such as hygrometers, sling psychrometers and thin polymer films.
A parcel of air has a relative humidity of 60%. If the temperature of the air increases, but the amount of water vapor remains constant, what happens to the relative humidity?
Relative humidity will decrease.
Warm air can hold more or less water vapor compared to cold air?
Warm air can hold more water vapor.
What three processes can put water vapor into the atmosphere from Earth’s surface?
Evaporation from surface water, sublimation of snow and ice, and transpiration by plants.
What process converts water vapor to liquid water?
Condensation
What process converts water vapor directly to ice crystals?
Deposition (I will accept sublimation)
What process in the water cycle moves water from the Atmosphere to Earth’s surface?
Precipitation
Under what conditions is the relative humidity 100%?
When the amount of water vapor in the air equals the amount of water vapor that the air can hold at that temperature.
What is saturated air?
When the amount of water vapor in the air equals the amount of water vapor that the air can hold at that temperature.
On Day A, the wet bulb thermometer decreased by 3 degrees. On Day B, the wet bulb thermometer decreased by 5 degrees. The air temperature on both days was the same. Which day had the higher relative humidity?
Day A had the higher relative humidity because less evaporation occurred. The air was already holding more water.
Why do tables listing the percentages of gases in Earth’s atmosphere exclude the amount of water vapor?
Most gases make up a uniform percentage of the atmosphere anywhere on Earth. The percentage of water vapor is different in different locations.
Why does warm air hold more water vapor?
The other gas molecules are spread further apart as they move faster, creating more space for the water vapor to intermingle.
How can the wet bulb and dry bulb thermometer readings determine the relative humidity?
Subtract the wet bulb temperature from the dry bulb temperature to get the temperature difference. Use a chart to find where the dry bulb temperature and the temperature difference meet to determine the relative humidity.
Why is the dry bulb temperature the same or larger than the wet bulb temperature?
Heat energy from the wet bulb thermometer evaporates water from the cloth, which lowers the wet bulb temperature.
What is the relative humidity if the wet bulb temperature is the same as the dry bulb temperature?
Relative humidity would be 100%.
What are some possible condensation nuclei in the atmosphere?
Dust from storms, meteor dust, salt particles, pollen and volcanic dust.
What role do condensation nuclei play in the formation of clouds?
Condensation nuclei are solids upon which water droplets and ice crystals can form.
What can form when the dew point temperature is below freezing?
Frost
What is the dew point temperature?
The temperature at which a parcel of air is saturated.
What is adiabatic cooling?
Heat from the surface will warm a parcel of air, which causes it to rise. As the air rises, less pressure on the air causes it to expand and cool.
Does adiabatic cooling rely on energy transfer from the warm air parcel to the colder air around it?
No
How can moving air masses form clouds?
A cold air mass will move under a warm air mass, causing the warm air mass to rise and cool adiabatically.
How can topography form clouds?
As the sun hits one side of a mountain, it can warm air above it and cause it to rise and cool adiabatically.
What is advective cooling?
Warm moist air loses energy when it moves horizontally over a cold surface.
What factors determine how clouds are named?
Altitude of the cloud and shape
What shape is a cirrus cloud?
Thin and wispy. Named for the Latin word for curl.
What shape is a cumulus cloud?
Puffy cloud. Named for the Latin word for heap.
What shape is a stratus cloud?
Large, flat cloud that covers a lot of the sky. Named for Latin word for sheet
What is a nimbus cloud?
A rain cloud
What is the name of the extremely thick cloud that is associated with thunderstorms?
Cumulonimbus
Low level clouds whose base is at an altitude of 0-2000m above Earth’s surface use which prefix?
Strato-
Middle clouds whose base is at an altitude of 2000-6000m use which prefix?
Alto-
High clouds whose base is above 6000 m use which prefix?
Cirro-
What is fog?
Condensation near the Earth’s surface
How does radiation fog form?
Nightly cooling of Earth’s surface causes air to cool also.
How does advection fog form?
Warm, moist air moves over a cooler surface.
How does steam fog form?
Cool air moves over warm water
What is rain?
Liquid precipitation
What is snow?
Solid precipitation that falls as small crystals or a network of crystals.
What is sleet?
Rain that freezes when it passes through a cold enough layer of air to cause drops to solidify.
What is freezing rain?
Supercooled liquid drops that freeze when they hit the ground. Form glaze ice
What is hail?
Pellets of ice formed in cumulonimbus clouds
How can droplets or crystals in a cloud form precipitation?
The air movement causes droplets or crystals to coalesce and grow larger. Gravity will pull larger drops or crystals to the surface.
What is supercooling?
Air cooled below the freezing point without changing state. The air will need additional freezing nuclei in order to form precipitation.
How is the amount of rain that falls in a given area determined?
With a rain gauge
How is the amount of snow fall in a given area determined?
Measured with a measuring stick
What information does Doppler Radar provide?
Doppler radar measures the intensity and movement of precipitation.
How does Doppler Radar work?
An antenna sends out a radio wave pulse. The amount of returned energy and the wavelength of the returned energy determines the intensity and movement of the precipitation.
