Weather and Atmosphere

Weather Composed of Moisture Temperature Pressure How these move through the atmosphere

Layers of the Atmosphere Troposphere Weather Occurs Here Stratosphere Ozone Layer Mesosphere Coldest Place in Atmosphere Thermosphere Hottest place in atmosphere

Why Is There Weather? Earth rotates Atmosphere contains water Sun heats the Earth unevenly

Earth Rotates The Earth’s tilt changes the amount of sunshine received through the seasons In June the northern hemisphere is tipped toward the Sun, in December, the southern does

Earth’s Atmosphere Contains Water Vapor Water in our atmosphere undergoes changes between liquid, solid and gas phases as it is heated or cooled The heating and cooling may come from many sources, not just the Sun

Air Properties Warm air is lighter and tends to move quicker than cold air Warm air less dense than cold air Buoyancy- less dense material moves to the top of denser material Thermal expansion-when things get hot, expand and gases (air) gets lighter and moves upward, also how a thermometer works

Ascent and Descent Air rising cools Air descending warms This causes an area of lower pressure Air descending warms This causes an area of higher pressure Convection-warm gas rising, makes the wind

Why does air cool as it rises? Pressures are lower as we rise higher in the atmosphere As air rises, it expands because it is moving into an area of lower pressure. Expansion takes energy, and so the rising air gives up some of its thermal energy to expand, and becomes cooler The opposite applies to descending air

Wind movement

Sun Heats the Earth Unevenly This is how temperature would look if there were no continents or oceans Equatorial latitudes receive more energy than Polar, and are warmer The Earth’s atmosphere attempts to equalize the temperature around the globe by carrying warm air north and cold air south, and mixing them together COLD HOT COLD

Sun Heats the Earth Unevenly Land absorbs and releases energy faster than water or ice does

Earth Rotates As the air parcel moves southward, it is deflected so much that eventually It is moving west. It cannot reach the equator. Coriolis movement

Weather Zone Because the winds cannot flow directly from the poles to the equator, cold air must be carried in stages from north to south The “stages” or cells are climatic zones around the Earth There are three cells between pole and equator: temperate zone doldrums tropics

The Earth’s Circulation Cells At some boundaries, air is rising,others it descends Areas of ascent form lows and areas of descent highs

Low Pressure Caused when fronts meet and spin counter clockwise in the northern hemisphere Think of a counter-top being low- counter clockwise Air is rising, forms clouds Weather- clouds and possible precipitation, strong winds, warmer temperatures

Low Pressure System

High Pressure Sinking air, moves clockwise in the northern hemisphere Think of the clock which is up high-clockwise Weather- weak winds, bright, clear, heavy dew or frost, temperature inversions and traps pollution

High Pressure System

Clouds A.k.a.- high fog, mist, haze Forms when air cools below the dew point (water vapor condenses) Shape- depends on air movement Horizontal air- layered clouds Vertical air- upward clouds Temperature Above freezing- rain Below freezing- snow

Cloud Names Cirrus- thin, high, icy Stratus- sheets or layers Cumulus- vertical and thick, fluffy Alto- medium height Nimbus- rain Flat base of a cloud is the condensation level or dew point