Exam 3 Thursday Nov. 18. • This exam will cover the following chapters in the text book • Chapter 8 Pressure and Wind • Chapter 9 Small Scale and Local System • Chapter 10 Global System • Chapter 11 Air Mass and Fronts • The corresponding lectures are: Lectures 12 through 16
To prepare: • Review the lecture notes • Read the chapters • Review exercises 6 and 7 on Angel • Review quizzes 5, 6 (on Angel) and 7 (to be posted). While reviewing the lecture notes and the chapters, try to answer the questions listed below. These questions are taken from Questions for Review at the end of each chapter which highlight the key concepts.
What rule do we use to adjust the station pressure to the mean sea level pressure? Pressure decreases by 10 mb for 100 m increase in altitude in the lower atmosphere What is the force that initially sets air in motion? What does Coriolis force do to moving air in the northern hemisphere? How each of the following influence Coriolis force? wind speed latitude
Why on a map, closely spaced isobars indicate strong winds and widely spaced isobars indicate weak winds? What is geostrophic wind? Why would you not expect to observe geostrophic wind at equator? A geostrophic wind is a wind that results from a balance between the Coriolis force and the pressure gradient force. At the equator there is no Coriolis force, thus there cannot be a geostrophic wind. Why do upper-level winds in mid-latitude generally blow from the west? Because winds at these altitudes are approximately geostrophic, with higher pressures (warmer temperatures) to the south and lower pressures (colder temperatures) to the north. (Buys-Ballot Law).
How do winds blow around a low and a high aloft and near the surface in the Northern Hemisophere? What are the forces that affect horizontal movement of air? How does Buys-Ballot law help to locate regions of high and low pressure aloft and at surface? What is the effect of surface friction on wind speed and direction? As air moves from a rough to a smooth surface, how do the speed and direction change as a result of reduced friction?
Describe various scales of motion, and give an example of each A friend has just returned from a trans-Atlantic jet flight and reported that the plane dropped about 1000 m when it entered an ‘air pocket’. Explain to your friend what apparently happened to cause this drop? What is wind shear and how does it relate to clear air turbulence? You are fly fishing in a mountain stream during the early morning; would you expect the wind to be blowing up-stream or downstream?
What is Chinook winds and why they are warm and dry? What atmospheric conditions contribute to the development of a strong Santa Ana condition? Why is a Santa Ana wind warm? As air descends from the elevated desert plateau, it funnels through mountain canyons in the San Gabriel and San Bernardino Mountains, finally spreading over the Los Angeles basin and San Fernando Valley. The wind often blows with exceptional speed in the Santa Ana Canyon (the canyon from which it derives its name). These warm, dry winds develop as a region of high pressure builds over the Great Basin. The clockwise circulation around the anticyclone forces air downslope from the high plateau. Santa Ana winds are warm because of compression heating of the already warm, dry desert air.
Explain the following concepts: • single Cell model • three cell model • Doldrums • subtropical highs, horse latitude • trade winds, intertropical convergence zone (ITCZ) • Westerlies • polar front, subpolar low, polar eastlies • jet stream • El Nino and La Nina
Draw a large circle. Now place the major surface pressure and wind belts of the world at their appropriate latitudes. Along a meridian line running from the equator to the poles, how does the general circulation help to explain zones of abundant and sparse precipitation? How does the polar front influence the development of the polar front jet stream?
What is a major El Nino event? What are the conditions over the tropical eastern and central Pacific Ocean during the phenomenon called La Nina?
Air masses • What is an air mass? • Source regions for air masses • Air mass classification • Characteristics of different types of air masses that affect United States • Weather Fronts • What is a front? • Types of fronts, their characteristics, and the associated weather conditions. • Lake-effect snow