1. Earth Science

2.  Big Idea: Protecting the human interests of health, safety and resource management depends upon an understanding of natural hazards and human impact on Earth systems.

3.  Weather influences each day’s activities, jobs, our health, and comfort. Weather can change the plans for a day or add enjoyment.  The U.S. has the biggest variety of weather in the world. The weather influences us, and we influence it.

4.  Weather is the state of the atmosphere at any given time. It can change hourly, daily, or seasonally.  Climate is an aggregate of weather. It is at minimum 30 years of weather data for an area.

5.  The most important aspects of weather and climate are:  Temperature  Precipitation  Humidity  Air pressure  Cloudiness  Wind  All of these variables, although separate, are related to one another.

6.  The atmosphere is a mixture of gasses. Most of it is nitrogen, followed by oxygen, Argon, Carbon dioxide and a small amount of others.

7.  Carbon dioxide and water vapor are the major greenhouse gasses, even though CO 2 only makes up 0.036% of the entire atmosphere. Water vapor fluctuates, but can be up to 4% by volume.  Latent heat is heat that is stored often in water vapor. Where there is a lot of water vapor, there is a lot of heat stored in the atmosphere.

8.  The layers of the atmosphere:  Troposphere  Stratosphere  Mesosphere  Thermosphere  Exosphere  ionosphere  The troposphere is where all weather occurs.

9.  The temperature decrease in this layer is called the environmental lapse rate. This means that the temperature drops approximately 6.5  C per kilometer, or 3.5  F/1000ft. At the boundary of the troposphere we find the tropopause.

10.  The stratosphere has stable temperatures until reaching the ozone layer or stratopause where temperatures begin to increase, or warm up.  The stratosphere contains the ozone layer. It’s important because it protects us from UV radiation. Its thickness fluctuates by area.

11.  Ozone depletion occurs when O 3 (ozone) molecules are broken down by substances that are not naturally found in the atmosphere, like CFC’s, or chlorofluorocarbons. These travel up to the ozone layer where they separate an oxygen molecule from the ozone molecule creating O and O 2. This thins and depletes the ozone layer.

12.  In the 1970’s the US banned the use of CFC’s. However, it is estimated that it can take up to 15 years for the chemicals to reach the ozone layer.  Depletion of the ozone layer can cause cataracts and skin cancer in humans, damage crops, and affect the oceanic food chain.

13.  The mesosphere finds temperatures decreasing again until the mesopause.

14.  The fourth layer the thermosphere has no upper defined limit, but temperatures increase here due to absorption of short- wave, high-energy solar energy.  The atmosphere thins as you travel away from earth, and just like anything else is held here by gravity.

15.  The temperature changes with altitude also. The layers of the atmosphere are based on major temperature changes.

16.  Almost all of the energy that drives the weather comes from the sun. However, that energy is not distributed evenly over Earth’s surface.  Unequal heating of the Earth causes ocean currents, winds, and all weather.

17.  Earth rotates and revolves. Rotation causes day and night, while revolution causes years and seasons.  Seasonal variations are due to the tilt of the Earth.

18.  In summer months the Earth is tilted toward the sun, receiving radiation that is more direct.  In winter months Earth received less direct radiation causing the energy to be spread out over a greater area, thus delivering less heat.

19.  There are 4 important days when considering Earth’s heat balance.  These days are called either solstices or equinoxes. Each year there is two of each and they have special importance in the Earth/sun relationship.

20.  The vernal equinox occurs on March 21/22 at signals that the Sun’s rays are at a 90  angle at the equator. This is the first day of spring. 12 hours of daylight and darkness for the entire Earth!

21.  The summer solstice signifies that the Sun’s rays are at a 90  angle at the Tropic of Cancer. This is the first day of summer in the Northern Hemisphere. It occurs on June 21/22. The longest day of the year sunshine-wise for us! Not the hottest!?

22.  The autumnal equinox occurs on September 22/23. It signifies the first day of fall and that the Sun’s rays are at 90  on the equator once again. 12 hours of daylight and darkness for the entire Earth!

23.  Lastly the winter solstice occurs December 21/22. The Sun’s rays are hitting the Earth at 90  on the Tropic of Capricorn in the southern hemisphere. This is our shortest day of the year sunshine-wise. After this day the amount of daylight we get begins to get longer until June 21/22. Not the coldest day of the year, just the most darkness?!

24.  All locations at the same latitude receive the same amount of solar radiation. However, differences between locations on Earth can affect the weather of a locality.

25.  In the atmosphere heat transfers by conduction, convection and radiation.  The sun heats up the Earth, which through conduction heats up the atmosphere that is touching it.

26.  Convection is the transfer of heat through currents in a fluid (liquid or gas). The air that is heated by conduction is then transferred by convection to other areas.  Radiation heat transfer occurs when the Earth receives and emits energy in electromagnetic wavelengths.

27.  The energy received from the Sun has more than one path. Only about 25% of incoming radiation makes it to Earth’s surface. Other radiation is absorbed, scattered or reflected.  Scattering occurs when incoming radiation is redirected by dust, gasses or pollution in the atmosphere.  Reflection occurs when radiation is reflected by clouds, water, snow, and other Earth surfaces.

28.  Albedo is the term for the total radiation reflected from a surface. Water*, snow, and sand have a high rate of albedo, or reflect a lot of radiation.  Absorption occurs when substances absorb a lot of the radiation that falls on them.

29.  Water vapor and CO 2 are good absorbers. They are often called the major greenhouse gasses.

30.  Most of the heat in our weather system is due to the Earth absorbing radiation and reradiating it into the atmosphere.  About 50% of the energy that reaches Earth’s surface is absorbed. Water vapor can absorb 5x more radiation than other gasses.

31.  When the gasses absorb Earth radiation, they warm, and emit radiation away. Some head for space, and some are sent back toward earth and absorbed by Earth again. This is the greenhouse effect, although it is not how an actual greenhouse works.

32.  We can measure temperatures in many different ways, generally (warm, cold) or specifically. We can take many measurements and compare them to get averages and ranges, also.

33.  Daily mean: the average of the highest and lowest temperatures for a day.  Daily range: the difference between the highest and lowest temps. for a day.  Monthly mean: adding the daily means together and dividing by the # of days  Annual mean: average of the 12 monthly means.  Annual range: the difference between the highest and lowest monthly means.

34.  Temperature can be affected by many different things.

35.  Solar radiation is the most important, but others can cause big changes in temperature which is based on latitude, discussed earlier.  If latitude was the only control than locations that had the same latitude would have identical temps.

36.  Locations that are landlocked, or on the western side of a body of water (in the prevailing westerlies) will experience colder winter temperatures and warmer summer temperatures, due to the quick heating and cooling of land.  Examples: Eastern U.S. coastline, Lake Michigan coast of Wisconsin, Idaho, WY, etc.

37.  Locations that are located on the eastern side of a body of water will experience more moderate temperatures in winter and summer.  Examples: Western Michigan, the US west coast, Buffalo NY, etc.

38.  Altitude also affects the temperatures of a location.  The farther a location is from sea level the cooler it will be. Cities located in the mountains are much cooler than areas that are located below sea level, due to the concentration of the atmosphere.  Examples: Denver, CO vs. Death Valley, Quito vs. Guayaquil, Ecuador

39.  Whether a city is on the leeward or windward side of a coastline or mountain range can affect temperatures, too.  Mountains can act as barriers, blocking cooling winds and rain.  A city on a windward coastline can be much cooler than a city on a leeward coastline even at the same latitude. The windward city will receive cool air off of the water, while a leeward coastline receives its winds off of the continent.

40.  Cloud cover can affect temperatures by reflecting warming radiation away from an area or keeping it close to the Earth.  Lastly, the albedo of an area affects its temperatures. An example of this is the city. A city can become a “heat island” due to increased absorption of heat.

41.  Worldwide temperatures maps (isothermal maps) show near linear patterns.

42.  Warm temperatures are located at the equator and then decrease as one moves toward the poles.  There are shifts when changing from continental locations to oceanic locations and vice versa, and there are seasonal shifts during the year.

43.  There are also differences between the Northern and Southern Hemispheres. The Southern Hemisphere is mostly water so it has straighter isotherms, or lines of equal temperature.

44.  Isotherms also reflect ocean current affects.