Definition: Weather is the state of the atmosphere at a specific time and place. Weather is the result of heat from the sun and earth's air and water.

Air Temperature DEFINITION Measure of the amount of heat (average amount of motion, or kinetic energy, of molecules) in the air

Air Temperature FACTORS THAT AFFECT Location on Earth- how directly the sun’s rays strike the area Amount of radiation from the sun

Air Temperature MESUREMENT Thermometer in degrees Celsius (°C)

Air Pressure (Atmospheric Pressure) DEFINITION The force of air exerted on an area from all directions, including directly down, on Earth

Air Pressure (Atmospheric Pressure) FACTORS THAT AFFECT Gravity pulling on air Altitude Density of the air – how close the molecules are together Temperature of air – kinetic motion of molecules

Air Pressure (Atmospheric Pressure) MEASUREMENT Barometer – average pressure of atmosphere at sea level = 1 bar; unit for reporting air pressure is millibar (1/1000 of a bar)

Wind DEFINITION Movement of air from an area of high pressure to an area of low pressure Described by direction and speed

Wind FACTORS THAT AFFECT Differences in the amount of solar radiation received Coriolis effect- rotation of the Earth

Wind MEASURMENT Wind vane- measures wind direction- arrow points in the direction from which wind is blowing; a compass point may also be used Anemometer- measures wind speed in kilometers (or miles) per hour

MOISTURE: DEFINTION Water in the atmosphere; transitions between any of water’s three states in Earth's normal temperature range

MOISTURE: FACTORS THAT AFFECT Air Temperature

MOISTURE: MEASURMENT Measured as humidity

MOISTURE: Humidity DEFINITION Amount of water vapor in the air

MOISTURE: Humidity FACTORS THAT EFFECT Air temperature- Heat from the sun evaporates water

MOISTURE: Humidity MEASUREMENT Hygrometer– measured in percent

MOISTURE: Relative Humidity DEFINITION Amount of water vapor in volume of air compared to the maximum amount the air can hold (saturation) at a given temperature

MOISTURE: Relative Humidity FACTORS THAT AFFECT Humidity Air Volume Temperature

MOISTURE: Relative Humidity MEASURMENT Psychrometer- measure can range from percent

MOISTURE: Dew Point DEFINITION Temperature at which air is saturated (holding all the moisture it can hold) and condensation (dew or frost) forms

MOISTURE: Dew Point FACTORS THAT EFFECT Humidity Temperature Air Pressure

MOISTURE: Dew Point MEASUREMENT Calculated using humidity, temperature, and air pressure

MOISTURE: Cloud Formation and Type DEFINITION Warm air forced upwards, expands, and cools; When the air is saturated, water vapor condenses around small particles such as dust or salt

MOISTURE: Cloud Formation and Type FACTORS THAT AFFECT Temperature Air Pressure Humidity

MOISTURE: Cloud Formation and Type MEASUREMENT Shape and Height: Stratus- smooth layers at low elevation Cumulus- puffy, white Cirrus- High, thin, white, feathery

MOISTURE: Precipitation DEFINITION Water falling from clouds

MOISTURE: Precipitation FACTORS THAT AFFECT Air Temperature- rain, snow, sleet, hail

MOISTURE: Precipitation MEASUREMENT Rain Gauge- Measured in centimeters or inches