Weather and Climate Exam 2

When air cannot hold any more moisture it is:

Saturated

Amount of moisture air can hold is dependent on what atmospheric variable?

Temperature

what is dew point and how does it relate to relative humidity?

The temperature where saturation occurs in the air. As the air temp drops to meet the dew point, relative humidity increased toward 100%

How does temperature affect relative humidity?

temp and relative humidity have an inverse relationship. as temp goes up, airs capacity to hold water decreases.

When air rises, does it expand or contract? does it cool or heat up?

As air rises, it expands and cools.

what is a psychrometer and how does it work?

It’s an instrument used to measure atmospheric humidity. as the psychrometer is slung around, wter evaporates from the wet bulb, cooling it off. the greater the temperature difference, the drier the air.

what is the lifting condensation level?

The height in the sky where rising air cools down enough to its dew point temp and becomes saturated, causing water vapor to turn into clouds.

what happens when warm, moist air mixes with cool air?

Frontal lifting occurs as the lighter warm air is pushed upward over the cooler, denser air. this causes warm air to cool to saturation and condenses water vapor to form clouds and precipitation.

what is adiabatic process?

Process where temperature changes solely because of pressure changes, without heat being added or removed.

define orographic lifting.

Air is forced upward when horizontal winds encounter elevated terrain, such as a mountain range.

how does orographic lifting create a rainshadow?

As moist air gets pushed up a mountain, it cools and drops its moisture as rain on the front side. the now-dry air moves over the peak and warms as it descends the back side, leaving that area dry and creating a rainshadow.

what ultimately determines the buoyancy of a parcel of air

The buoyancy of air is determined by its temperature relative to the surrounding air. if air is warmer than surroundings, its lighter and rises. opposite for colder.

define absolutely stable air

occurs when a rising parcel of air becomes colder and denser than the surrounding atmospheric air.

define absolutely unstable air

when a rising air parcel cools more slowly than the surrounding environment. because the parcel is less dense than the air around it, it continues to rise on its own.

define conditionally stable air

occurs when an air parcel is stable when unsaturated but becomes unstable if it is forced to rise high enough to reach saturation.

What are the most common mechanisms that cause air to lift

1. orographic lift

2. frontal lifting

3. convergence

4. localized convection

Define frontal lifting

Warmer, lighter air meets cold air and is pushed upward over the colder, denser air along weather fronts

Define convergence

when winds from different directions flow together horizontally, forcing the meeting air upward.

Define localized convection

Solar heating warms the ground, creating buoyant pockets of warm air that rise.

what two phases are clouds made up of?

liquid water and solid ice crystals.

define Stratus clouds

low-level clouds, occurring at or below 2,000 meters. forms flat, uniform, featureless gray layers covering much or all of the sky

Define Nimbus clouds

low-level clouds, occurring below or at 2,000 meters. dark, dense clouds that produce precipitation

Define cumulus clouds

fair weather fluffy, individual clouds. Low-level clouds usually below or at 2,000 m

Cumulonimbus clouds

tall, towering clouds that produce severe weather. They start low in the atmosphere and extend into the higher levels, often reaching the troposphere. has an anvil shaped head.

Why do some water droplets float while others fall to earth?

Small droplets float because they are light enough for rising air currents to hold them suspended in the atmosphere. they fall to earth only when they grow larger through collision-coalescence into larger, heavier collector drops whose weight overcomes air currents.

define collision-coalescence

Process in warm clouds where larger falling water droplets collide with smaller droplets and merge (coalesce) with them, causing them to grow.

define sleet

frozen raindrops. it happens when falling snow melts into rain, and then refreezes into small ice pellets before hitting the ground.

define rain

Liquid water droplets that fall from clouds to the ground when they become too heavy to stay suspended in the air.

define freezing rain

rain that falls as liquid water but freezes instantly upon touching cold ground or surface objects.

define snow

solid precipitation formed of ice crystals that grow in subfreezing cloud layers and fall to the ground without melting along the way

What is lake-effect snow? How do the Great Lakes result in increased precipitation in northern Indiana, Michigan, Ohio, Pennsylvania, and New York?

This happens when very cold air blows across the warmer waters of the Great Lakes. As the air moves over the water, it picks up heat and mosture to form snow clouds, dumping heavy snowfall on the lands directly downwind in indiana, michigan, ohio, pennsylvania, and new york.

what is the intertropical convergence zone (ITCZ)? is it stationary?

belt of low pressure near the equator where trade winds from the Northern and Southern hemispheres meet and force air upward to form clouds and rain. it is NOT stationary; it shifts seasonally with the position of the sun as it moves northward in July and south in January.

what weather is typical of the ITCZ

warm, highly humid and rainy with frequent heavy thunderstorms

What causes the subtropical high-pressure belts to exist?

they form around 30 degrees latitude, where air in the Hadley cell sinks back toward Earth’s surface.

what is the weather typically like in subtropical high-pressure belts?

Sinking air prevents clouds and rain from forming so the weather in these regions is typically sunny, warm, and dry with light.

what is the jet stream?

fast-moving flow of air high up in the atmosphere. it acts as a powerful wind current that carries weather systems, heat, and moisture across the globe.

what is the polar front?

boundary in the midlatitudes that separates cold polar air from warm air

What kind of air movement and temperature conditions happen in the polar front

cold polar air meets warm air to create a sharp temperature boundary between hot and cold. High above this boundary, a fast-moving ribbon of air known as the polar jet stream flows through the atmosphere.

what is a gyre and what causes this circulation

A giant, circular loop of ocean currents. it forms as global surface winds push oceans water across the sea, surviving into large spinning loops when the water hits land.

low pressure is associated with what type of weather?

cloudy, wet, or stormy weather.

high pressure is associated with what type of weather?

fair, clear, and dry weather

what is a monsoon climate

a monsoon climate has a rainy summer and a dry winter. this happens because seasonal winds shift direction, blowing moist ocean air inland during summer and dry air out to sea during winter.

what continents best exhibits the monsoon climate

Asia best exhibits the monsoon climate.

what factors lead to sea breezes

during the day, land heats up faster than the water, causing warm air over the land to rise. Cool air from over the ocean then blows inland to take its place.

what factors lead to land breezes

At night, land cools down faster than the ocean. cool air over the land then blows out to sea to replace the warm air rising over the water.

define ridges

elongated areas of high atmospheric pressure in the upper atmosphere that forms when warm air pushes toward the poles. associated with warm air.

define trough

a long dip or valley of low pressure high in the sky that extends toward the equator. associated with cold air