Chapter 2: Understanding Weather Section 1: Water in the Air

The Water Cycle – the continuous movement of water from Earth’s ______ & _____ into the __________, in the ______, and back into the ______ & _____ oceans rivers atmosphere ground oceans rivers

- Humidity * Amount of __________ in the air * As the __________ increases so does the air’s ability to hold water vapor water vapor temperature

Relative Humidity – measures the amount of __________ in the air compared with the _________ amount of water vapor that the air can hold at a certain temperature * Measured using a ____________ water vapor maximum psychrometer

Condensation – process by which a gas (water vapor) becomes a liquid (water) * The air must be ________ (100% relative humidity) * Can also occur when air cools to its ________ (the temperature at which gas becomes a _____) saturated dew point liquid

Clouds – a collection of small water droplets or ice crystals suspended in the air - Cumulus – puffy, white clouds that tend to have flat bottoms

- ______ – form in layers & cover large areas of the sky & often block out the sun (____ is a stratus cloud that has formed near the ground) Stratus Fog

- Cirrus – thin, feathery clouds found at high altitudes

- Nimbo – or – nimbus indicate clouds that are likely to form __________ precipitation

- Cirro – clouds formed at high altitudes - Alto – clouds formed at middle altitudes

Precipitation – when water returns to Earth’s surface - Rain – most common - _____ – rain falls through freezing air & freezes into ice - _____ – air is so cold that the water vapor freezes directly into ice Sleet Snow

- Hail – forms when raindrops are caught in an updraft & are carried into higher clouds where it freezes. As it starts to fall more water vapor attaches to the ice. The ice may be caught in another updraft & the outer water vapor freezes. This happens again & again until the ice ball is too heavy to be lifted by an updraft. The largest hailstone ever recorded was the size of a softball

Let’s Review Weather is the condition of the atmosphere at a certain time and place. Weather is affected by the amount of water vapor in the air. The water cycle describes the movement of water above, on, and below Earth’s surface. Humidity describes the amount of water vapor in the air. Relative humidity is a way to express humidity. When the temperature of the air cools to its dew point, the air has reached saturation and condensation occurs. Clouds form as air cools to its dew point. Clouds are classified by form and by the altitude at which they form. Precipitation occurs when the water vapor that condenses in the atmosphere falls back to Earth in solid or liquid form.