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End Warm-up What instrument is used to measure air pressure? What are condensation nuclei and why are they important? This bar timer, will start when anywhere on the slide is clicked. The bar will move from left to right and the word ‘End’ will appear at the end, accompanied by a ‘Deep Gong’ sound. It is possible to change the duration of this timer to any time, by entering the animation settings, and changing the timing for ‘rectangle 3’. Note the time has to be entered as a number of seconds – so if you want 2mins & 30secs – this is entered as 150 (60X2 + 30 = 150). End

Tuesday, January 10, 2017 Warm-up Review air pressure, precipitation, water cycle, and clouds Work on Midterm Review Homework: Midterm Exam Review due 1/17

AIR PRESSURE

Keeping an Atmosphere Atmosphere is kept by the world’s gravity Low mass (small) worlds = low gravity =almost no atm. High mass (large) worlds = high gravity = thick atm. Gravity and pressure Air pressure depends on how much gas there is i.e. The atmospheric thickness.

Gravity and Atmospheric Pressure The stronger the gravity, the more gas is held by the world and the greater the weight of atm. on a point

Earth’s Atmosphere About 10 km thick Consists mostly of molecular nitrogen (N2) and oxygen (O2)

The air is made up of molecules.

Gravity pulls the air molecules toward the earth, giving them weight Gravity pulls the air molecules toward the earth, giving them weight. The weight of the air molecules all around us is called the air pressure. Your weight is the result of gravity pulling your mass down on the bathroom scales. Note that weight has units of a force, such as pounds.

High altitudes = lower pressure Air pressure can be thought of as the column of air rising above us. As we go up in altitude, we get closer to the top of the column. Thus there are fewer molecules of air above us to be pulled down by gravity, so the air “weighs” less. Therefore, pressure always decreases as one goes up. Low altitudes = higher pressure

Atmospheric Pressure Gas pressure depends on both density and temperature. Adding air molecules increases the pressure in a balloon. Heating the air also increases the pressure.

Air pressure is equal in all directions. Because air is a fluid, force applied in one direction is distributed equally in all directions. Thus the downward pull of gravity on air molecules produces air pressure in all directions. Pressure = force per unit area

Barometric pressure goes down. As elevation goes up Barometric pressure goes down. This is an inverse relationship.

A Barometer is used to measure air pressure.

As we have noted earlier, higher elevations have fewer air molecules pressing downward, and so atmospheric pressure is lower. This means a barometer will read lower as it is carried to a higher elevation. Airplanes use a special type of barometer, called an altimeter, to measure altitude.

Changing Pressure A rising barometer = increasing air pressure. This usually means: Rising barometer readings indicate that a high pressure system is approaching. Higher atmospheric pressure is usually associated with fair weather and clearing skies. Rising barometer readings indicate that a high pressure system is approaching. Higher atmospheric pressure is usually associated with fair weather and clearing skies.

Changing Pressure A falling barometer = decreasing air pressure. This usually means: Falling barometer readings usually indicate the approach of an area of low pressure. Low pressure readings are usually associated with storm systems. Tornadoes and hurricanes can produce very low barometric readings. Falling barometer readings usually indicate the approach of an area of low pressure. Low pressure readings are usually associated with storm systems. Tornadoes and hurricanes can produce very low barometric readings.

PRECIPITATION

What is Precipitation? Rain Snow Sleet Hail Freezing Rain Precipitation is the falling of any form of water from the air to Earth’s surface. Examples: Rain Snow Sleet Hail Freezing Rain Condensation Nuclei anything water vapor can condense onto such as dust, smoke, salt, etc.

Types of Precipitation RAIN: (Condensation) Forms when condensed water vapor forms tiny water droplets in clouds. When the droplets get big enough (Coalesce), they fall to the Earth.

Types of Precipitation 2. SNOW (Deposition) Forms when the air temperature is below freezing, water vapor turns directly into a solid. These ice crystals fall to Earth as Snow.

Types of Precipitation 3. SLEET: (Snow-Rain-Freeze) Forms when rain passes through a layer of air which is below freezing. The rain then freezes into ice and falls to the Earth.

Types of Precipitation 4. FREEZING RAIN: (Snow-Rain) Forms when the Earth’s surface is below freezing but the atmosphere is warm. When rain hits the surface, it freezes on contact creating a layer of ice on the ground, trees, cars, power lines, etc.

Types of Precipitation 5. HAIL: (Summer-Time) Forms when a rain drop in a cumulonimbus cloud is blown to the top of the cloud and freezes. This frozen drop then falls down through the cloud where it “grows” by collecting more liquid water. This process continues until the hail stone is too heavy to stay in the cloud and falls to Earth.

Water Processes Liquid water turns into a Solid (ice) FREEZING Solid water (ice) turns into a liquid MELTING Liquid water turns into a gas (water vapor) EVAPORATION Water vapor (gas) turns into a liquid CONDENSATION Water vapor (gas) turns into a solid (ice) DEPOSITION Solid Water (ice) turns into water vapor (gas) SUBLIMATION

The Water Cycle The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again. The Sun evaporates water from the Earth's surface (oceans, lakes, etc.). The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) begins. The water flows downhill as runoff (above ground or underground), eventually returning to the seas where the process begins again.

CLOUDS Chapter 11.3 notes Mr.Allbee

Cloud Formation Clouds form as warm moist air is forced upwards, cools and water vapor condenses to form tiny water droplets. Millions of tiny water droplets gather together to form a cloud

Moist Adiabatic Rate - how fast saturated air cools above the LCL Cloud Formation Dry Adiabatic Lapse Rate – how fast unsaturated air will cool as it rises DAR = 100C for every 1000m rise The height at which the dew point is reached and a cloud begins to form, the Lifted Condensation Level (LCL) has been reached. Usually, the LCL is marked by the base or bottom of the cloud Moist Adiabatic Rate - how fast saturated air cools above the LCL MAR = avg. 60C for every 1000m rise

Cloud Formation Orographic Clouds are clouds that are formed as moist air rises over mountains or other major geographic features. The air floats up the side of the mountain and cools quickly, condensing and turning into a cloud.

Cloud Classification 1. By Their Shape 2. By Their Height Stratus Two common ways to classify clouds: 1. By Their Shape Stratus Cumulus Cirrus 2. By Their Height Cirro Alto Strato

Stratus Clouds

3 Cloud Types Based on Shape 1. Stratus Form in layers or smooth even sheets Usually low altitude clouds Associated with fair weather or drizzle Sometimes forms a gray blanket covering the entire sky and produces light rain or drizzle

Cumulus Clouds

3 Cloud Types Based on Shape 2. Cumulus Masses of puffy white clouds Associated with fair weather but may possibly produce thunderstorms

Cirrus Clouds

3 Cloud Types Based on Shape 3. Cirrus High, thin, white, feathery clouds Associated with fair weather Indicate that bad weather may be approaching

Height – Prefixes for Cloud Base Cirro – High Level Clouds Alto – Middle Level Clouds Strato – Low Level Clouds

Other Types of Clouds Dark clouds associated with heavy rain and storm Vertical Development High, towering clouds usually with a low altitude base Nimbus Dark clouds associated with heavy rain and storm

10 Common Cloud Names Cirrus Cirrostratus Cirrocumulus AltoStratus Altocumulus Cumulus Stratocumulus Nimbostratus Cumulonimbus

Altocumulus Clouds

Altostratus Clouds

Cirrocumulus

Cirrostratus Clouds

Cirrus Clouds

Cumulonimbus Clouds

Cumulus Clouds

Stratus Clouds

Nimbostratus Clouds

Stratocumulus Clouds