chapter 5

- Tornadoes

(form over land) - Swirling, funnel-shaped clouds that form over land - Spinning is caused by interaction of colder air near the ground and the rapidly rising warmer air above - Midwest in the spring and summer because cold fronts from the north penetrate deeply into the Great Plains + Midwest

Tropical cyclones

(form over warm ocean water, occasionally pass over coastal land areas) - Spawned by the formation of low-pressure cells of air over warm tropical seas - Atl: hurricane - Pac: typhoon - Take a long time to form and gain strength, unlike tornado - Therefore easier to monitor and prepare

Low

- A low-pressure air mass - Contains low-density, warm air at its center - This air rises, expands, and cools - When its temperature drops below a certain level, called the dew point, moisture in the air condenses and forms the cloud - The condensation process requires that the air contain suspended tiny particles of dust, smoke, sea salts, or volcanic ash, called condensation nuclei, around which water droplets can form - If the droplets coalesce into larger drops or snowflakes heavy enough to fall from the sky, precipitation occurs - That's why a low tends to produce cloudy/stormy weather

warm air process

- An advancing warm air mass rises up over a mass of cool air - As the warm air rises, its moisture begins condensing into droplets - Forming layers of clouds at different altitudes - Gradually the clouds thicken, descend to a lower altitude, and often release their moisture as rainfall

High

- An air mass with high pressure - Contains cool, dense air that descends slowly toward the earth's surface and becomes warmer - Because of the warming, water molecules in the air do not form droplets, or condensation - As a result of this, clouds (made out of droplets) do not form in the presence of a high - Results in fair weather with clear skies

cold air process

- Cold air is denser than warm air so advancing cold front stays close to the ground and wedges beneath less dense warmer air - Cold air pushes the warm, moist air up, which produces rapidly moving, towering clouds called thunderheads - As it passes through, it can cause high surface winds and thunderstorms followed by cooler temperatures and a clear sky

jet streams

- Influences movement of the air masses - Powerful winds that circle the globe near the top of the troposphere - Similar to fast-flowing rivers of air moving west to east, one in each hemisphere somewhere above and below the equator - Form because of temperature difference between the equator and the poles, this causes the air to move - As the air moves away from the equator, north and south, it is deflected by the earth's rotation and flows generally west to east - The greater the temperature difference, the faster the flow of these winds - Jet streams can influence weather by moving moist air masses from one area to another

Atmospheric pressure

- Results from molecules of gases in the atmosphere (nitrogen and oxygen mostly) zipping around at very high speeds and bouncing off everything they encounter - Greater near the earth's surface because the molecules in the atmosphere are squeezed together under the weight of the air above them

Meteorologists

- Use equipment (radars and stationary sensors) to obtain data on weather variables - Feed the data into computer models to draw weather maps for different geographic locations - Some computer models project upcoming weather conditions based on probabilities that air masses, winds, and other factors will change in certain ways

front

- the boundary between two air masses with different temperatures and densities - most dramatic changes occur here

Which of the plants below is probably found in deserts?

A fleshy plant with spines and a waxy covering

____ is characterized by permafrost.

Arctic tundra

El Niño-Southern Oscillation (ESNO)

Disrupts normal wind patterns in the Pacific Ocean, affecting weather globally

Cold front

Leading edge of an advancing mass of cold air

Much of which biome has disappeared from the earth because it has been converted to farmland for growing crops and grazing cattle?

Temperate grassland

Warm front

The boundary between an advancing air mass and the cooler one replacing it

Weather

The set of physical conditions of the lower atmosphere including temperature, precipitation, humidity, wind speed, cloud cover, etc. in a given area over a period of hours to days

warm air vs. cool air

Warm air is less dense than cool air (weighs less per unit)

Which of the following are examples of greenhouse gases?

Water vapor, methane, and nitrous oxide

A forest in northern Canada would be an example of ____.

a boreal forest

most important factors in the weather in any area

atmospheric temperature and precipitation

Large terrestrial regions characterized by a particular type of climate and a certain combination of dominant plant life are called ____.

biomes

Lizards that live in the desert have tough, scaly skin that helps them to ____.

conserve water

Temperate deciduous forests typically have ____.

cool summers, cold winters, and little precipitation

The rain shadow effect refers to ____.

drier conditions on the leeward (facing away from the wind) side of mountain ranges

Succulent plants are most likely to be found in ____.

dry conditions, such as those in temperate deserts

The transition zone between two ecosystems or biomes is called a(n) ____.

ecotone

In the western United States, an area called the Great Basin contains many mountain ranges that are separated from each other by high desert. Because these mountain ranges provide sanctuary for some species, they could be called ____.

islands of biodiversity

weather changes when

one air mass replaces or meets another

weather we experience

results from interactions between the leading edges of moving masses of warm air and cold air

Some animals living in tropical rainforests have stratified niches that are ____ to ____ competition for resources.

specialized; minimize

Cone-bearing trees are characteristic of the ____.

temperate deciduous forest

In tropical rainforests, vegetation layers are structured according to ____.

the plants' needs for sunlight

One explanation for why polar regions are colder than equatorial regions is that ____.

the sun never reaches these areas because of the tilt of Earth on its axis

The equator is warmer than the poles because ____.

the sun's rays strike directly at the equator

During El Niño conditions, ____.

the thermocline in the eastern Pacific Ocean deepens, disrupting upwelling

Weather Extremes

tornadoes and cyclones

A forest that is known for its year-round uniformly warm temperature is the ____.

tropical rainforest

Ocean currents are most significantly affected by ____.

variation in winds over the ocean and changes in the shapes of land masses

A grassland with widely scattered clumps of trees located near the equator would be called a ____.

warm grassland