Water enters the atmosphere… ► Evaporation – Water changes from a liquid to a gas. Most water evaporates from the oceans. Latent heat is stored. Wind and high temps speed up evaporation. ► Transpiration – water in plants evaporates ► Evapotranspiration – all evaporation from earth and plants.
Water leaves the atmosphere… ► Condensation – Water changes from a gas to liquid to form clouds. Latent heat is released. ► Precipitation – any form of water that falls from clouds (rain, snow, sleet, hail)
► Runoff –water that flows over the ground, eventually leads back to a larger body of water ► Accumulation – when water collects into large bodies, or falls directly into it Where does it go?
► Infiltration – when water seeps (sinks) into the ground to be stored as groundwater ► Groundwater flow – when water moves while underground
Factors that affect infiltration ► 1. Porosity: ► 1. Porosity: the size of the spaces between sediments in the ground or in the rocks themselves. ► 2. Permeability: ► 2. Permeability: how fast water will pass through the soil material. The ability to pass through sediments in the ground.
Permeability: ► Permeable: water passes through fast (gravel and sand) ► Impermeable: water passes through very slowly (silt and clay) PermeabilityPermeability animation
Gravel and Sand: High porosity, high permeability Because there are larger spaces between the pieces of gravel and grains of sand where water can go through easily. Silt and Clay: Low porosity, low permeability Silt and clay are tightly packed together and have very small spaces between them. Why did the water pass through the gravel and sand faster?
What is the relationship between sediment size and porosity? ► The larger the sediment, the more porous because the spaces will be bigger. ► The smaller the sediment, the less porous because the spaces will be smaller. http://www.brainpop.com/science/earthsystem/groundwater/
Factors that affect runoff: ► Permeability of the soil- type of soil ► Slope – steeper will cause more runoff ► Saturation of the ground – wetter ground will decrease permeability and cause more to run off ► Groundcover – vegetation decreases runoff, concrete increases runoff.
How much water is in the air? ► Relative humidity –% of water vapor in the air compared to the max it can hold ► Example: If the air is half filled to its capacity, it’s relative humidity is 50%. ► A basic rule is that warm air holds more moisture than cool air
How much water can the air “hold” before it rains? ► Dew point – the temperature that the air needs to reach for precipitation to happen, it’s the point that condensation occurs ► Example: Air temp = 75 o Dew Point = 75 o Relative humidity = 100% and it is raining!
How does relative humidity change with air temperature? ► Air at different temperatures will hold more or less amounts of water vapor. ► Warm air can hold more water vapor before it is saturated than cold air. ► www.weather.com www.weather.com
Measuring relative humidity ► Psychrometer – a type of hygrometer ► Has 2 thermometers: A Dry bulb thermometer A Wet bulb thermometer covered in damp cloth (evaporation causes cooling)
Example #1 ► What are the relative humidity and dew points? ► Wet bulb temp = 12 o C ► Dry bulb temp = 16 oC ► Wet bulb depression = 16 - 12 = 4 oC
Water Cycle Movie The EPA Global Warming Kids Page--Water Cycle Animation
Why do clouds form? ► Clouds exist in the atmosphere because of rising air. ► As air rises and cools the water in it will release heat and turn to liquid or ice crystals forming clouds. (condensation) ► Tiny particles of dust, salt, and smoke in the air are needed for the water to condense onto.
What do clouds do? ► Clouds influence the Earth's climate: Reflect incoming solar radiation back to space Block outgoing heat from the Earth's surface. At night, clouds act as a "blanket," keeping some of the day's heat near the surface. Carry moisture around the globe as part of the water cycle
What are the different types of clouds? ► There are three basic types: Stratus – spread out in flat layers Cumulous – fluffy piles of cotton Cirrus – wispy feathery clouds made of ice crystals When you add the suffix nimbus to a cloud type it means “rain”
Look out the window… ► What kind of clouds do you see today? ► What is the weather expected today? ► Is there a lot of moisture in the air or a little?
What are man-made clouds? ► Contrails are the condensation trail that is left behind by a passing jet plane. Contrails form when hot moist air from jet exhaust mixes with the cold air in the high altitudes.
What is fog? ► Fog happens when a stratus cloud forms near the ground. When warmer air passes over cooler ground. ► Observe images of advection fog. Observe images of advection fog. Observe images of advection fog.
► Cloud matching game Cloud matching game Cloud matching game