SCIN 137 AMU week 3 lesson CLOUD DEVELOPMENT AND PRECIPITATION & AIR PRESSURE AND WINDS Introduction to Meteorology American Military university
- Lesson Overview
- Welcome to Week 3! This week we investigate concepts of air pressure and winds. Many people do not realize that wind is really the result of uneven heating and cooling of the Earth’s surface, which creates varying air pressures. Air always seeks to equilibrate (like if you spill a liquid, it will seek to fill the lowest points), so as air flows from higher pressure to lower pressure winds are created! Simple, no? Well, of course not, there are many factors that influence that “simple” process, but pressure differential is at the heart of all wind flow. A neat experiment you can do when the weather is cool is simple and available to most. On a very cool day (winter works best) turn on the hot water in a shower that has a shower curtain, and close the bathroom door. As the water heats the air in the shower, the pressure of that air lowers and the air begins to rise. In order for the air in the room to equilibrate, the cooler (denser and heavier) air outside the shower curtain will try to flow into the space left by the rising air inside the shower. The shower curtain will move into the shower area as that cool air pushes inward. This is why when we take hot showers in cold weather the shower curtain seems to attack us and stick to our legs – the air is simply trying to equilibrate and is creating wind in the process!
Students will be able to:LO-19. Understand what is meant by atmospheric stability. LO-20. Understand how clouds develop. LO-21. Understand what causes precipitation. LO-22. Explain what is meant by air pressure. LO-23. Understand what produces horizontal and vertical air flow. LO-24. Discuss pressure gradient force and Coriolis force. LO-25. Discuss how winds are different at the surface than in the upper atmosphere.
The following activities and assessments need to be completed this week:
- Read Barry and Chorley: Chapter 5
- Week 3 Lesson
- Week 3 Forum
- Week 3 Lab
- Week 3 Quiz
- COMET Modules (Optional):
- Urban Flooding: It Can Happen in a Flash!
- Rain Gauges: Are They Really Ground Truth?
- Skew-T Mastery
Topics to be covered include:
- Lapse rate and stability
- How clouds develop
- Pressure gradient force
- Coriolis force
In meteorology it is often convenient to refer to a parcel of air – a balloon-like mass of air that we can think of moving together as a unit. As a parcel of air rises, it moves to an area with lower atmospheric pressure. The molecules in the parcel will spread out and the size of the parcel will grow. As it expands, it cools as the energy in the parcel is now more spread out. If the parcel descends back to its original position, the atmospheric pressure around the parcel increases and the parcel becomes smaller and warmer. This is a very important concept to remember: going up the parcel spreads out and cools, going down the parcel becomes more compact and warmer.
If the atmosphere is stable, the parcel rises to a point where it is cooler than the surrounding atmosphere, and it stops going up. If the environment is unstable, the temperature of the parcel will be warmer than its surroundings, and will continue to rise.
Absolutely Stable Air
The figure illustrates the relationship between the dry adiabatic lapse rate, the saturated lapse rate, and the environmental lapse rate when the air is absolutely stable. The slope of the environmental lapse rate indicates that the temperature of the air is decreasing with increased altitude, but this actual rate of cooling is less than either the dry adiabatic lapse rate or the saturated lapse rate.
Suppose a parcel of air is nudged upward from the ground. Recall that the parcel cools as it gains altitude, and how rapidly it cools with increasing altitude depends on whether the parcel is dry or moist. By the time the parcel of air reaches the altitude of the dashed horizontal line, the temperature of the parcel will be cooler than the surrounding air. It will be somewhat cooler if the air is moist, and it will be much cooler if it is dry. In either case, the parcel of air will be cooler and thus denser than the air surrounding it, so it will sink back down to the ground.
Qualities of Credible, Academic Sources
Most background research involves peer-reviewed scientific journals and other related primary sources, which are defined as original materials that have not been interpreted or evaluated by a second party (University Libraries, 2017). Scientific primary sources include studies published in peer-reviewed journals, conference papers, dissertations, lab notebooks, and theses (University Libraries, 2017). Secondary sources, on the other hand, contain commentary about a primary source and consist of review articles, books, and websites that cite the primary source in question (University Libraries, 2017).
Scientific Questions are Focused and Testable
In general, the best scientific questions are focused, testable, and verifiable. First, a question should focus on a relatively narrow field of research and contribute to a well-designed hypothesis and experiment. For example, if you were conducting research on cancer, you would focus specifically on the efficacy of a single new treatment or a single variable that may impact the growth and spread of a specific type of cancer. Testable questions ask about phenomena of the natural world that a researcher can investigate through experiments and quantitative observations (Mansfield Middle School, n.d.). A researcher should be able to test a question through repeated experiments and observations.
What are the Building Blocks of Living Organisms?
Robert Hooke’s microscope
Robert Hooke first observed cells in the 1600s, and his discovery led to the development of cell theory, which states that all living organisms are made of cells. He did not pursue a study for the sole purpose of discovering cells but stumbled across them as part of a royal commission to study insects. In 1661, King Charles II of England commissioned Sir Christopher Wren to conduct a series of microscope studies on insects, but he later turned the study over to 26-year-old Robert Hooke, who joined the Royal Society for Scientists (House, 2009).
A self-educated prodigy, Hooke taught himself technical drawing and invented new strategies for controlling the height, angle, and illumination of microscopes. In his writings, he explained that the purpose was to answer questions and discover the visible world and many things that were unknown. Hooke conducted additional studies beyond insects and examined fabric, leaves, and glass. He discovered cells by viewing a thin cutting of cork and discovered that the sample consisted of thousands of tiny empty spaces contained by walls, which he named cells (House, 2009). Hooke received credit for discovering the building blocks of living organisms and later inspired studies that developed cell theory because he was driven to ask questions and discover.
How are Traits Passed from One Generation to the Next?
Charles Darwin recognized that reproduction allowed beneficial adaptations to persist in a species, although he worked in the question for many years he was not able to find a biological mechanism to explain how inheritance occurred that worked. Gregor Mendel (1822-1884) was an Austrian monk that had questions about how traits are inherited in biological species. Through a large hybridization experiment he first explained how traits are inherited through his eight-year research on common pea plants. Pea plants represented an ideal study organism because he could easily control their fertilization to select for specific traits, such as plant height, seed shape, and pea color (Miko, 2008). He proposed principles of inheritance that described the transmission of traits before anyone knew that genes existed, such as alternate versions of traits and the ability to distinguish between dominant and recessive traits (Miko, 2008).
While Mendel’s ground breaking experiments led to an understanding of the process of inheritance the substance of inheritance was still a question waiting to be answered. In 1944, deoxyribonucleic acid (DNA) was discovered to be substance of inheritance rather than protein in an elegant experiment conducted aby Oswald Avery and colleagues. The next question to be answered was: What is the structure of DNA? There were four scientists who co-discovered the double-helix structure of DNA shortly after World War II and thereby formed the basis for modern biotechnology (Chemical Heritage Foundation, 2015). Maurice Wilkins first proposed the use of x-ray crystallography to study DNA, and his colleague Rosalind Franklin used this technique to obtain the first x-ray crystallographic images of DNA in 1951 (Chemical Heritage Foundation, 2015). James Watson and Francis Crick built off Franklin’s work and actually accessed her images without her permission, along with as much additional evidence as they could gather, to construct the double helix model of DNA (Chemical Heritage Foundation, 2015). All four scientists still received credit for their work by publishing articles announcing the structure of DNA in the same issue of Nature in 1953 (Nature Research, 2003).