WeatherWhat is the weather?

• Day-to-day atmospheric conditions, caused by short-term changes in air density, pressure, temperature, and humidity.

• Includes: Air TemperatureAir Pressure

HumidityCloud CoverPrecipitation

Wind Speed and Direction

WeatherWhat causes weather?

• The instability of the troposphere (due to strong, frequent convection currents) is the main, underlying cause of short-term changes in atmospheric conditions. This causes weather patters on Earth.

Weather

WeatherWhat causes weather?

• Weather is fueled and controlled by the flow and movement of heat energy in the atmosphere.

• This flow is a global system that covers the entire Earth.

As convection currents move air vertically in the atmosphere, areas of different air pressure and temperature form. These differences cause movement of air from region to region.

WeatherHow does weather change?

• Weather is fueled and controlled by the flow and movement of heat energy in the atmosphere.

• This flow is a global system that covers the entire Earth.

As convection currents move air vertically in the atmosphere, areas of different air pressure and temperature form. These differences cause movement of air from region to region.

The energy the Earth receives from the sun changes as you move from the equator to the poles. This change in energy causes changes in air temperature and pressure, which in turn causes a flow toward the north and south of the planet. Combined with the impact of the spinning of the Earth, this breaks the flow of air in the atmosphere into three major regions from equator to pole.

WeatherHow does weather change?

• Weather is fueled and controlled by the flow and movement of heat energy in the atmosphere.

• This flow is a global system that covers the entire Earth.

As convection currents move air vertically in the atmosphere, areas of different air pressure and temperature form. These differences cause movement of air from region to region.

The energy the Earth receives from the sun changes as you move from the equator to the poles. This change in energy causes changes in air temperature and pressure, which in turn causes a flow toward the north and south of the planet. Combined with the impact of the spinning of the Earth, this breaks the flow of air in the atmosphere into three major regions from equator to pole.

This global pattern is called the Coriolis effect, and affects the movement of air masses in the atmosphere and water currents in the Earth’s oceans.

WeatherWhat causes weather?

• Wind is the movement of air in the atmosphere.

• Air moves due to changes in pressure and temperature in the atmosphere.

When air masses of different pressures and temperatures get close to each other, they create a gradient. These close-by differences force air to move from high pressure to low pressure, and high temperature to low temperature.

• Air Density• Air Pressure• Air Temperature• Humidity

Convection

Changing and moving masses of air in the lower atmosphere

Coriolis effect(due to the spin

of the Earth)

Global wind patterns(called “belts,”

such as jet streams)

Movement of large weather systems

around continents and the globe

Low Pressure:Warm, humid

air rises

High Pressure:Cool, dryair sinks

WeatherWhat is the weather?

• Day-to-day atmospheric conditions, caused by short-term changes in air density, pressure, temperature, and humidity.

• Includes:Air Temperature

Air PressureHumidity

Cloud CoverPrecipitation

Wind Speed and Direction

WeatherWhat is the weather?

• Day-to-day atmospheric conditions, caused by short-term changes in air density, pressure, temperature, and humidity.

• Includes:Air Temperature

Air PressureHumidity

Cloud CoverPrecipitation

Wind Speed and Direction

Weather describes the day-to-day conditions that change on an hourly/daily/weekly basis. Climate describes the long-term patterns from season to season and year to year. Climate describes patterns in weather over the cycle of a long period of time.

WeatherWhat is the weather?

• Day-to-day atmospheric conditions, caused by short-term changes in air density, pressure, temperature, and humidity.

• Includes: Air TemperatureAir Pressure

HumidityCloud CoverPrecipitation

Wind Speed and Direction

WeatherPrecipitation

• Water (solid or liquid) falling from clouds• Depending on temperature between cloud and ground, might be liquid

or solid

Droplets grow and move due to air currents that keep them suspended in the atmosphere. Eventually, they fall as precipitation when they are too heavy for air currents to support their weight. It takes about 1 million droplets to make a single drop of rain.

Rain Snow Sleet

Glaze Dew/Frost Hail

WeatherPrecipitation

• The instability of the troposphere (due to strong, frequent convection currents) is the main, underlying cause of short-term changes in atmospheric conditions. This causes weather patters on Earth.

WeatherPrecipitation

• The instability of the troposphere (due to strong, frequent convection currents) is the main, underlying cause of short-term changes in atmospheric conditions. This causes weather patters on Earth.

WeatherCloud Cover

• Formed when warm, humid air moves upward, cools, and releases water vapor

• Influence weather by• blocking sun’s energy (less heat reaches surface)• absorbing heat from Earth’s surface (less heat recirculates via

convection)• source of precipitation

Clouds tend to create a smaller range (mediate) in temperature changes from day to night.

WeatherCloud Cover

• Formed when warm, humid air moves upward, cools, and releases water vapor

• Influence weather by• blocking sun’s energy (less heat reaches surface)• absorbing heat from Earth’s surface (less heat recirculates via

convection)• source of precipitation

Clouds tend to create a smaller range (mediate) in temperature changes from day to night.

WeatherCloud Cover

• Formed when warm, humid air moves upward, cools, and releases water vapor

• Influence weather by• blocking sun’s energy (less heat reaches surface)• absorbing heat from Earth’s surface (less heat recirculates via

convection)• source of precipitation

Clouds tend to create a smaller range (mediate) in temperature changes from day to night.

WeatherWhat causes changes in weather?

• An air mass is a large volume of air with generally consistent temperature and humidity

• Air masses move altogether as a part of a larger convection cell

Where an air mass forms determines its general temperature and humidity. Air masses form in high pressure regions over arctic, polar, tropic, or equatorial regions (temperature), over land or sea (humidity).

WeatherWhat causes changes in weather?

• An air mass is a large volume of air with generally consistent temperature and humidity

• Air masses move altogether as a part of a larger convection cell

Where an air mass forms determines its general temperature and humidity. Air masses form in high pressure regions over arctic, polar, tropic, or equatorial regions (temperature), over land or sea (humidity).

c = continental (forms over land – dry)m = maritime (forms over ocean – humid, wet)

A = arctic (cold) P = polar (coldest)T = tropical (warm) p = equatorial (warmest)

WeatherWhat causes changes in weather?

• The boundary between two air masses is called a “front.”

• Fronts lead to storms when an arriving air mass has very different temperature, pressure, and humidity than the surface it is moving over (the previous air mass)

There are four types of fronts:cold, warm, stationary, and occluded.

WeatherWhat causes changes in weather?

• Storms are fast changes in atmospheric conditions that cause high winds, large vertical clouds, and lots of precipitation.