SCIN 137 AMU week 1 lesson EARTH’S ATMOSPHERE & WARMING THE EARTH AND THE ATMOSPHERE Introduction to Meteorology American Military university
- WEEK 1: EARTH’S ATMOSPHERE & WARMING THE EARTH AND THE ATMOSPHERE
- The first lesson introduces the concept of meteorology and defines some of its branches. It also deals with the composition and structure of the Earth’s atmosphere, and sets the stage for the subsequent discussion regarding atmospheric warming and heat transfer. In particular, this lesson examines in broad brushstrokes how the Earth’s surface and the atmosphere receive, absorb and lose the Sun’s heat energy, thereby creating an annual energy balance that makes life possible. Topics to be covered include:
- The branches of meteorology
- Composition of Earth’s atmosphere
- Major layers of Earth’s atmosphere
- Heat energy, temperature and latent heat
- Temperature scales and conversion formulas
- Transfer of energy and electromagnetic radiation
- Role of greenhouse gases
- Earth’s annual energy balance
Getting Started in Meteorology
Meteorology is the science of the atmospheric phenomena. The term meteorology dates back to the prolific Greek philosopher, Aristotle, who wrote the first documented book on the subject called Meteorologica. At that time everything that fell from the sky or was airborne was called a meteor, which is the origin of the word meteorology. Aristotle’s ideas dominated meteorological thinking for about two thousand years until the invention of new instruments such as the barometer in the sixteenth century. Using the barometer and other new instruments, scientists could test the validity of earlier meteorological claims. Later, with the use of air balloons and high flying military aircraft, scientists acquired more data to advance the science further. Today we use automated instruments and satellites to gather weather data and then use supercomputers to predict meteorological phenomena. Humans still continue to play a crucial role in the collection and interpretation of weather data.
Weather vs. Climate
Weather refers to the atmospheric conditions of the atmosphere at a particular place at a particular time, the changing temperature, pressure, humidity, wind speed, visibility, etc. It may include variations in these conditions over periods up to a few months. Climate refers to the long-term (usually 30-year) records of atmospheric behavior of a particular region. It does not just include the ‘average weather’ values but also the extremes of weather such as heat waves in the summer and cold spells in the winter. The climate of a particular locale may either stay stable over a period of decades, even centuries, or it may change quite significantly.
Molecules within the atmosphere are constantly bumping and reflecting off of each other. This state of motion is brought on by kinetic energy – the energy of motion. Temperature is a measure of the average kinetic energy of a substance, for example, the average air temperature of an area is the average kinetic energy of all the molecules in the air in that area. The higher the average kinetic energy of the molecules, the higher is the temperature. There is no upper bound when it comes to temperature, but there is a lower limit to the temperature of a substance, called absolute zero (–273.15°C or 0°K). Nothing in the universe can achieve this or a lower temperature.
A body at a higher temperature loses energy to a body at a lower temperature. This transferred energy is heat. The total energy stored in the molecules is called the internal energy. When a warm body is near a cooler body, the internal energy and temperature of the first body decreases while that of the second one increases.
Latent heat is heat energy that is either absorbed or emitted when an object changes its phase. The molecules in ice are moving much slower than the molecules in liquid water. The ice molecules need additional energy to make this change. During the change from solid ice to liquid water, the water absorbs heat from the environment. This heat absorbed during the change of state is latent heat. Similarly, water absorbs latent heat to change from liquid water to gas. The latent heat of evaporation is absorbed from the environment when water changes from a liquid to water vapor.
When the reverse process happens, latent heat is released into the environment. – when water goes from gas to liquid water or from liquid water to solid ice. During all these processes, the temperature of the water does not change during the change of state. Latent heat changes the phase not the temperature. Of course, if water condenses on your yard as dew in the evening, the temperature of the water will probably continue to fall as the night air grows more cool.
Scientists and engineers use a variety of different temperature scales to express the temperature of an object. They choose the most convenient temperature scale based upon what temperature they are describing and the particular audience for which the information is intended.
Three temperature scales are commonly used in meteorology and other branches of science. As indicated in the table below, the temperature scales named after Gabriel Fahrenheit [German physicist and chemist (1686 – 1736)], Anders Celsius [Swedish astronomer (1701 – 1744)], and Lord William Thomson Kelvin [Scottish mathematician and physicist (1824 – 1907)] are defined in terms of the freezing and boiling points of pure water and the temperature of absolute zero.
Although the general public in the United States is most familiar with temperatures expressed in degrees Fahrenheit, the Celsius temperature scale is used almost universally throughout most of the rest of the world. The Celsius scale is the temperature scale for the International System of Units, also known as the SI system, which is widely used by scientists and engineers.
Conversions between Temperature Scales
The difference in temperature between the freezing point of water (32°F) and the boiling point of water (212°F) is 180 Fahrenheit-sized degrees. That same difference in temperature from the freezing point of water (0°C) and the boiling point of water (100°C) is 100 Celsius-sized degrees. Thus the Fahrenheit-sized degree is only five-ninths as large as the Celsius-sized degree. This fact is used in the conversions among the various temperature scales.