Weather vs. ClimateAtmosphere Physical Science (We are at the home stretch now!)
Weather and Climate • Weather • the state of the atmosphere at a given time and place • constantly changing • Climate • an aggregate of weather conditions, the sum of all statistical weather information that helps describe a place or region. • The nature of both weather and climate is expressed in terms of the same basic “elements”, those quantities or properties measured regularly.
Elements of Weather The most important elements are: (1) air temperature, (2) humidity, (3) type and amount of cloudiness, (4) type and amount of precipitation, (5) air pressure, and (6) the speed and direction of the wind.
The Relevance of Weather Events Catastrophic Events and Associated Deaths
Earth’s Spheres Earth's four spheres include: • the atmosphere (gaseous envelope), • the lithosphere (solid Earth), • the hydrosphere (water portion), and • the biosphere (life).
Systems The two primary sources of the energy that power this system are: (1) solar energy that drives the external processes that occur at, or above, Earth's surface, and (2) Earth's interior, heat remaining from when the planet formed and heat that is continuously generated by radioactive decay.
Our Air • After water vapor, dust, and other variable components are removed, two gases, nitrogen and oxygen, make up 99 percent of the volume of the remaining clean, dry air. • Carbon dioxide, although present in only minute amounts (0.036 percent), is thought to be an efficient absorber of energy emitted by Earth and thus, influences the heating of the atmosphere. • Because of the rising level of carbon dioxide in the atmosphere during the past century (since the Industrial Revolution) attributed to the burning of ever increasing quantities of fossil fuels, many scientists believe that a warming of the lower atmosphere will trigger global climate change. • However, we will explore new, more scientific conceptions of the “Global Warming” theory in this course.
Variable Air Components The variable components of air include: • water vapor, • dust particles, and • ozone. Like carbon dioxide, water vapor absorbs heat given off by Earth as well as some solar energy. When water vapor changes from one state to another, it absorbs or releases heat.
Ozone • Ozone, a form of oxygen that combines three oxygen atoms into each molecule (O3), is an important gas concentrated in the 10 to 50 kilometer height in the atmosphere that absorbs the potentially harmful ultraviolet (UV) radiation from the Sun. • Over the past half century, people have placed Earth's ozone layer in jeopardy by polluting the atmosphere with chlorofluorocarbons (CFCs) which remove some of the gas. • Ozone concentrations take an especially sharp drop over Antarctica during the Southern Hemisphere spring (September and October).
Investigating the Atmosphere • Balloons play a significant role in the systematic investigation of the atmosphere by carrying radiosondes(lightweight packages of instruments that send back data on temperature, pressure, and relative humidity) into the lower atmosphere. • Rockets, airplanes, satellites, and weather radar are also among the methods used to study the atmosphere.
“Layers” of Our Atmosphere • Atmospheric temperature drops with increasing height above Earth's surface. • The temperature decrease in the troposphere, the bottom layer in which we live, is called the environmental lapse rate. • Its average value is 6.5°C per kilometer, a figure known as the normal lapse rate. The environmental lapse rate is not a constant and must be regularly measured using radiosondes.
Temperature Inversion • A temperature inversion, where temperatures increase with height, is sometimes observed in shallow layers in the troposphere. • The thickness of the troposphere is generally greater in the tropics than in polar regions. • Essentially all important weather phenomena occur in the troposphere.
The Stratosphere Beyond the troposphere lies the stratosphere; The boundary between the troposphere and stratosphere is known as the tropopause. In the stratosphere, the temperature at first remains constant to a height of about 20 kilometers (12 miles) before it begins a sharp increase due to the absorption of ultraviolet radiation from the Sun by ozone.
Mesosphere and Thermosphere The temperatures continue to increase until the stratopause is encountered at a height of about 50 kilometers (30 miles). In the mesosphere, the third layer, temperatures again decrease with height until the mesopause, some 80 kilometers (50 miles) above the surface. The fourth layer, the thermosphere, with no well-defined upper limit, consists of extremely rarefied air that extends outward from the mesopause.
Water Cycle • The movement of water between the atmosphere and Earth’s surface • 97% of Earth’s water is salt water found in oceans • Only 3% is fresh water • Out of that 3%: • 76% is trapped in Ice • Shallow groundwater – 12% • Deep groundwater – 11% • Lakes and rivers – 0.34% • Water vapor – 0.037%
Humidity Amount of H2O in air. The % of water vapor in the air compared to maximum amount the air could hold is called relative humidity.
How Clouds Form They form when water vapor in the air becomes liquid water or ice crystals Condensation – The process by which molecules of water vapor in air become liquid water. As warm air rises, it cools, and cold air can’t “hold” the water vapor anymore. Dew Point
Types of clouds • Cumulus • Stratus • Cirrus • Each one is associated with different type of weather, and altitude.
Cumulus Cotton balls Form less than 2 km above the ground, but may extend up to 18 km Fair weather Cumulonimbus – TAAAAAALL clouds with flat tops Thunderstorms
SUPERCELLS Great Plains, Canada THUNDERSTORMS convection, overshoot tops, outflow, and anvil formation
Stratus • “spread out” • Cover most of the sky • Drizzle, rain, or snow when thickened • Then called nimbosratus
Cirrus • Wispy, feathery • Form only at very high levels, above 6 km • Made of ice crystals
Morning Glory • What causes these long, strange clouds? No one is sure. A rare type of cloud known as a Morning Glory cloud can stretch 1,000 kilometers long and occur at altitudes up to two kilometers high. Although similar roll clouds have been seen at specific places across the world, the ones over Burketown, Queensland Australia occur predictably every spring. Long, horizontal, circulating tubes of air might form when flowing, moist, cooling air encounters an inversion layer, an atmospheric layer where air temperature atypically increases with height. These tubes and surrounding air could cause dangerous turbulence for airplanes when clear. Morning Glory clouds can reportedly achieve an airspeed of 60 kilometers per hour over a surface with little discernible wind.