Chapter 7 Weather The condition of the atmosphere at a certain time and place. is affected by the amount of water in the air. Water in liquid, solid, and gaseous states is constantly being recycled through the water cycle. Section 1 Water in the Air

Chapter 7 The Water Cycle The water cycle is the continuous movement of water from sources on Earth’s surface into the air, onto and over land, into the ground, and back to the surface. Section 1 Water in the Air

Chapter 7 Humidity Humidity is the amount of water vapor in the air. The air’s ability to hold water vapor changes as the temperature of the air changes. Warmer air can hold more water vapor than cooler air can. Section 1 Water in the Air

Chapter 7 Humidity, continued Relative Humidity is the amount of water vapor in the air compared to the maximum amount of water vapor that the air can hold at a certain temperature. Temperature and humidity can affect relative humidity. As humidity increases, relative humidity increases if the temperature stays the same. If the humidity stays the same, the relative humidity decreases as temperature rises and increases as temperature decreases Section 1 Water in the Air

Chapter 7 Humidity, continued Measuring Relative Humidity A psychrometer is an instrument that is used to measure relative humidity. A psychrometer consists of two thermometers, one of which is a wet-bulb thermometer and the other is a dry bulb thermometer. The difference in temperature readings between the thermometers indicates the amount of water vapor in the air. Section 1 Water in the Air

Chapter 7 Condensation Condensation is the process by which a gas, such as water vapor, becomes a liquid. Dew Point is the temperature at which a gas condenses into a liquid. This happens when the relative humidity reaches 100% and the air is saturated with water vapor. Section 1 Water in the Air

Chapter 7 Clouds A cloud is a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs when they water droplets stick together with dust particles in the air. Clouds are classified by form or shape, altitude and precipitation. Section 1 Water in the Air

Chapter 7 Clouds, continued Three main cloud shapes: Cumulus Clouds are puffy, white clouds that tend to have flat bottoms. Stratus Clouds are clouds that form in layers. Cirrus Clouds are thin, feathery, white clouds found at high altitudes. Section 1 Water in the Air

Chapter 7 Clouds, continued Section 1 Water in the Air

Chapter 7 High Clouds Section 1 Water in the Air -High cloud -Blown by high winds into long, thin wispy streamers -White -Fair weather, but weather is about to change

Chapter 7 High Clouds Section 1 Water in the Air - Sheet like, thin, covers sky - Made of ice crystals -White -Appears before rain or snow storm -Signals that a warm front is approaching -Formed when a large layer of air is lifted

Chapter 7 High Clouds Section 1 Water in the Air -Small rounded puffs in long rows -Made of ice crystals -White or gray -Brings fair but cold weather -Signals that a cold front is approaching

Chapter 7 Middle Clouds Section 1 Water in the Air -Covers whole sky -Made of ice crystals or water droplets -Gray/blue gray sky -Brings storms with continuous rain or snow

Chapter 7 Middle Clouds Section 1 Water in the Air -Form in groups or parallel bands -Made of ice crystals or water droplets -grayish white, thick -Brings thunderstorms -Formed by convection -Cold front is approaching

Chapter 7 Low Clouds Section 1 Water in the Air -Blankets whole sky -Made of water droplets -Light gray -Light mist or drizzling rain or snow -Fog is an example, but forms at the ground -can be formed from the lifting of a thick fog

Chapter 7 Low Clouds Section 1 Water in the Air -Low, lumpy in rows or spread out with clear sky between them -Made of water droplets -Gray -Fair weather or a light drizzle

Chapter 7 Low Clouds Section 1 Water in the Air -Blankets sky, ragged base -Made with water droplets -Dark gray -Steady rain or snow

Chapter 7 Vertical Clouds Section 1 Water in the Air -Puffy, like cotton, with flat base -Made with water droplets or ice crystals -White means fair weather -Darker means light to heavy showers

Chapter 7 Vertical Clouds Section 1 Water in the Air -Thick, tall -Made of water droplets and ice crystals -White to gray -Rain, hail, thunderstorms, tornadoes -Referred to as thunderheads

Chapter 7 Precipitation Precipitation is solid or liquid water that falls to Earth’s surface from a cloud. Rain is the most common form of precipitation Sleet and Snow Sleet forms when rain falls through a layer of freezing air. Snow forms when temperatures are so cold that water vapor changes directly to a solid. Hail are balls or lumps of ice that fall from clouds. Freezing Rain is rain that freezes into ice as it hits a surface. Section 1 Water in the Air

Chapter 7 Precipitation Section 1 Water in the Air