CLOUDS AND PERCIPITATION

BY SARAH MURPHY

Adiabatic Temperature Changes and Expansion and Cooling

• Temperature changes even though heat isn't added or subtracted.

• When air expands, it cools. When air compresses, it warms up.

• Dry adiabatic rate:Rate of adiabatic warming or cooling of unsaturated (dry) air.• Wet adiabatic rate:Rate of adiabatic temperaturechanges in saturated air.http://www.kidsgeo.com/geography-

for-kids/0070-adiabatic-temperature-changes.php

Orographic Lifting

• Places that are elevated act as barriers, or walls, to air flow, making air rise.

• Air cools, which may result in clouds appearing, and even precipitation.

http://www.nc-climate.ncsu.edu/edu/k12/.LiftingMechanisms

Frontal Wedging

• When masses of warm and cold air collide, it creates a front.

http://santasusana.org/pakelly/ES9CP/ES9%20clouds.htm

Convergence

• The collision of contrasting air masses make air rise. When air in the lower atmosphere flow together, air rises.

• Air can’t go down, so it goes up, which leads to cooling, and sometimes makes clouds form.

http://www.thekeytoislam.com/en/scientific-explanations/clouds-and-rains.shtml

Localized Convective Lifting

• Air above a paved parking lot will warm up more than a wooded area. Air above the parking lot is less dense than the surrounding air.

• During the summer, unequal heating of Earth’s surface causes some spots of air to be warmed up more than the rest of the surrounding air.

http://rst.gsfc.nasa.gov/Sect14/Sect14_1c.html

Stability (Density Differences and Stability and Daily Weather)

• Temperatures that are warmer than the surrounding air rise until it reaches an altitude where the temperature is equal.

• Stable air stays in same place, unstable air rises.

• Clouds won’t form when there is stable conditions in the atmosphere.

http://stabilitycloud.com/

Condensation

• The air must be saturated in order for water vapor in the air to form dew, fog or clouds.

• Saturation occurs when air is cooled to its dew point, but saturation doesn’t really occur when water vapor is in the air.

http://decorating.visitacasas.com/how-to-combat-condensation/

Types of Clouds• Cumulus clouds:Round, individual clouds.Flat based, rising into dome or tower-like

shapes.• Cirrus clouds:White and thin, high in the sky.• Stratus clouds:Layers that cover up most of the sky.No distinct individuality.

http://www.xconomy.com/boston/2011/03/22/clouds-clean-air-cancer-and-cardio-some-massachusetts-companies-on-the-rise/

High Clouds

• Cirrus, cirrostratus, and cirrocumulus. • Thin and white.• Made of ice crystals, due to low

temperature, and high altitude.

http://scienceray.com/earth-sciences/meteorology/clouds-types-and-how-they-are-formed/

Middle Clouds

• Ranges from 2000 – 6000 meters high.

• Altocumulus clouds.• Larger and denser than cirrocumulus

clouds.

http://scienceray.com/earth-sciences/meteorology/clouds-types-and-how-they-are-formed/

Low Clouds

• Stratus, stratocumulus, and nimbostratus clouds.

• Fog-like, covers most of the sky.• Nimbostratus clouds produce

precipitation.

http://scienceray.com/earth-sciences/meteorology/clouds-types-and-how-they-are-formed/

Clouds of Vertical Development

• Clouds that do not fall in the 3 height categories are associated with unstable air.

• The end result of clouds with great vertical forms are rain showers or thunderstorm. http://www.uwgb.edu/

dutchs/EarthSC102Notes/102Clouds.htm

Fog by Cooling and by Evaporation

• Fog is clouds that are very low to the ground.

• Fog that is caused by cooling usually forms where moist and warm air is carried to the shorelines by prevailing winds.

• Fog that is caused by evaporationforms when cool air moves overwarm air, which rises due to the different kinds of air meeting.

http://www.brainharmonycenter.com/brain-fog.html

Cold Cloud Precipitation (Bergeron Process)

• The Bergeron Process relies on supercooling and supersaturation to freeze the water in the air.

• Pure water in the air doesn’t freeze until it reaches -40 degrees Celsius, instead of 0 degrees Celsius.

http://alibanfm.wordpress.com/

Warm Cloud Precipitation (Collision-Coalescence Process)

• Water absorbing particles can remove water vapor from the air, which forms droplets that are big.

• The big drops collide with smaller droplets in the air.

http://www.cbs6albany.com/sections/weather/research/topics/topicfive/

Rain and Snow

• The term rain means drops of water that fall from a cloud and have a diameter of about 0.5 mm. Anything smaller is called a drizzle.

• Snowflakes usually melt before they hit the ground.

• Snow is made up of 6 sided ice crystals.http://warebuzz.com/dx-winter-snow-screensaver.html

Sleet, Glaze and Hail

• Glaze is supercooled freezing rain.• Hail is made in cumulonimbus

clouds.• Sleet is the fall of small particles of

clear or transparent ice.

http://cocorahs.org/Content.aspx?page=hail