LESSON 1 EXPLORING OUR EARTH'S ATMOSPHERIC ENVIRONMENT Study Objectives By the end of this unit, you should be able to: identify those important weather elements describing the state of the atmosphere. list the various instruments used to measure each weather element. list the usual values and the observed extreme ranges of surface weather elements. After reading this chapter, the student should be able to: distinguish between weather and climate. describe the scientific method. explain the value of models in scientific investigations. Textbook Reading Assignment Recommended Readings from Moran and Morgan (1997): pages 1-16. Lecture # 2 Recommended Readings from Moran and Morgan (1997): pages 1-16, 21-24; 375-382. Overview We begin our study of the atmosphere by distinguishing between weather and climate, the principal topics of this book. The atmosphere is the arena in which weather and climate take place. Our present atmosphere is the product of a lengthy evolutionary process and consists of a mixture of gases (mostly nitrogen and oxygen) in which is suspended a variety of tiny solid and liquid particles (collectively called aerosols). Much of what is known about the atmosphere's composition and structure is derived from direct measurements by instruments borne by kites, balloons, aircraft, rockets, and Earth-orbiting satellites. One finding of these efforts is that the atmosphere can be subdivided into layers based on the vertical profile of average air temperature. The lowest of these layers, the troposphere, is the site of virtually all weather. A portion of the upper atmosphere, known as the ionosphere, contains a relatively high concentration of electrically charged particles. This region is also the site of the aurora. Study notes Outline: A. WHAT IS METEOROLOGY? Derivation of Key Words - Weather and Climate The Present Scope of Meteorology and the Atmospheric Sciences B. COURSE OBJECTIVES C. GOALS OF METEOROLOGY Observation Codification Explanation Prediction Adaptation Modification D. CHARACTERISTICS OF METEOROLOGY International Physical Interdisciplinary E. BRIEF HISTORY OF METEOROLOGY AND CLIMATOLOGY Ancient - Weather Lore Classic Greek Meteorology Renaissance Meteorology Meteorology in the Scientific & Industrial Revolutions Organized weather observations Our concept of storms New tools and models ///// OBSERVATIONS OF THE EARTH'S ATMOSPHERE Outline: A. THE PLANET EARTH & EARTH SYSTEMS Uniqueness of the Planet Earth Components of the Planet Earth System Interactions within the System B. SURVEY OF THE EARTH'S ATMOSPHERE Importance of the Earth's planetary atmosphere Overall Dimensions of the Earth's atmosphere Comparison with the other components of the Earth System C. WEATHER - CLIMATE ELEMENTS The role of Meteorological Observations What we need to Know Observed Surface WEATHER - CLIMATE ELEMENTS BAROMETRIC PRESSURE AIR TEMPERATURE ATMOSPHERIC HUMIDITY PRECIPITATION CLOUD TYPE, AMOUNT WINDS (SPEED & DIRECTION) D. THE SURFACE WEATHER STATION Instruments Location and Exposure of Weather Instruments E. THE SURFACE WEATHER MAP The meaning of SYNOPTIC WEATHER ANALYSIS Goal of synoptic weather analysis Requirements for synoptic weather analysis Historical perspective Isopleths Isobars Isotherms Interpretation of modern surface weather maps F. OTHER OBSERVATIONAL TOOLS Radiosondes Weather Radar Weather Satellites Meteorological Rockets Wind Profilers IN this chapter emphasize the weather element aspect, as well as rules. Overview Study notes Review Questions Before completing the Written Assignment, answer the following Review Questions. These Review Questions are for your use and you should not to submit these for grading. They are designed to assist you in mastering the material presented in this unit and in preparing for the written assignment and for the examinations. A Key is provided at the end of this Course Guide. If you have difficulty with any of these questions, please contact your instructor at the University of Wisconsin–Extension for assistance. Key Terms and Concepts to Know Suggestions for Additional Reading Links to Other References: The provides access to many types of current weather maps and other that the meteorologist uses. Explanation of the time system, , that the meteorologist uses. This explanation includes the procedure for converting between local Central Time and UTC or Z Time Materials on various . Written Assignment 1 After you have worked through the Review Questions, please proceed with this unit's written assignment. Please enter the answers on the appropriate preprinted answer sheet and mail your completed assignment to your instructor at the University of Wisconsin–Extension for grading. Use one of the printed envelopes provided with your course materials. Should include: ??. What were the surprises or challenges that you encountered, or questions that arose, during your study of this lesson? HOMEWORK #1 WEATHER ELEMENTS 1. Convert the following lengths: 1 inch = centimeters 1 cm = meters 1 mile (statute) = meters 1 meter = feet 100 km = miles (statute) 1. What is the difference between the concept of weather and the concept of climate? Give an example of each, using personal experience. 2. The barometric pressure associated with one standard atmosphere at mean sea level is [you may round to nearest whole number]: inches of mercury centimeters of mercury pounds per square inch millibars feet of water 3. The highest recorded sea level corrected pressure in the world was . [Please include units!] The lowest recorded sea level corrected pressure in the world was . [Please include units!] The range between the record lowest and highest sea level corrected pressure (above) is approximately . [Please include units!] 4. What is the weight exerted by the atmosphere upon the flat, horizontal roof of a 30 foot by 50 foot building? [Assume standard sea level conditions; English units may be used here]. Clearly show your work for partial credit! 5. If the air pressure decreases in the vertical at a rate of 1 mb per 10 meters, what is the approximate station pressure measured at Mile High Stadium in Denver (elevation of 1 mile), assuming that sea level corrected pressure is 1000 mb? Clearly show your work for partial credit! How does the station pressure at Denver compare with the record sea level pressures that you determined in Question 3? How do you account for this vertical difference in air pressure in comparison with the set of record sea level pressures? 6. Convert the following temperature readings: 59°F = °C = K -40°C = °F = K 263 K = °C = °F 7. The record high temperature for Madison, WI was 107°F on 14 July 1936, while the record low was -37°F on 30 Jan 1951. What is the range of extreme temperatures? . 8. Compare these record temperatures with those of the United States and the world. [Please include units!] Record High Record Low Range United States World 9. The National Weather Service at Madison reported the following information for two days during this past January. The "normal" high and low temperatures for these days are also included and represent the 30 year averages for the 1961–1990 climatological interval. ----------- Observed ----------- ----------- "Normal" ----------- DAY High [°F] Low [°F] Ave. [°F]* High [°F] Low [°F] Ave. [°F]* 16 Jan 1997 18 -8 24 7 23 Jan 1997 24 10 25 7 a. What were the heating degree day units (based upon 65°F) for: 16 Jan 1997 23 Jan 1997 b. What are the "normal" heating degree day units (based upon 65°F): 16 Jan 23 Jan c. Qualitatively, how would the amount of energy required for space heating on each of those dates compare with that of the climatological (or "normal") average for the corresponding dates? Explain your reasoning. [* Note: Round up the average temperatures to the nearest whole degree Fahrenheit.] CHAPTER 1 (Moran and Morgan, 1997) ATMOSPHERE: ORIGIN, COMPOSITION, AND STRUCTURE We begin our study of the atmosphere by distinguishing between weather and climate, the principal topics of this book. The atmosphere is the arena in which weather and climate take place. Our present atmosphere is the product of a lengthy evolutionary process and consists of a mixture of gases (mostly nitrogen and oxygen) in which is suspended a variety of tiny solid and liquid particles (collectively called aerosols). Much of what is known about the atmosphere's composition and structure is derived from direct measurements by instruments borne by kites, balloons, aircraft, rockets, and Earth-orbiting satellites. One finding of these efforts is that the atmosphere can be subdivided into layers based on the vertical profile of average air temperature. The lowest of these layers, the troposphere, is the site of virtually all weather. A portion of the upper atmosphere, known as the ionosphere, contains a relatively high concentration of electrically charged particles. This region is also the site of the aurora. CHAPTER OBJECTIVES After reading this chapter, the student should be able to: distinguish between weather and climate. describe the scientific method. explain the value of models in scientific investigations. describe the principal events in the evolution of the Earth's atmosphere. distinguish between the heterosphere and the homosphere. explain why the significance of an atmospheric gas or aerosol is not necessarily related to its relative abundance. sketch the average vertical temperature profile of the atmosphere. describe the origin and significance of the ionosphere. explain how the ionosphere influences long-distance radio transmissions. MULTIPLE CHOICE QUESTIONS 1 Weather is a. variable. b. the state of the atmosphere at some place and time. c. usually described in terms of such variables as temperature and wind speed. d. confirmed mostly to the troposphere. * e. All of the above are correct. 2. The climate of some locality encompasses a. average weather conditions. b. extremes in weather. * c. Both of the above are correct. 3. The scientific method is a systematic form of inquiry that involves a. observation b. speculation. c. reasoning. d. experimentation. * e. All of these are correct. 4. A scientific model is an _________ representation of the way a system works. a. exact b. erroneous * c. approximate 5. The behavior of a system (such as the Earth-atmosphere system) a. is controlled by random events. * b. is governed by well-known natural laws. c. is so variable that it is fruitless to try to model the system. d. can never be predicted. e. is well beyond the realm of human understanding. 6. A weather map is an example of a ____________ model. a. conceptual b. mathematical * c. graphical d. numerical e. physical 7. A global climate model that is used to predict the climatic future is a __________ model. a. conceptual b. graphical * d. numerical e. physical 8. The atmosphere is composed of a. a mixture of gases called air. b. mostly nitrogen and carbon dioxide. * c. a mixture of gases and suspended aerosols. d. nitrogen and oxygen exclusively. e. mostly water vapor, oxygen, and ozone. 9. During an early phase of the planet's existence, Earth's atmosphere was similar in composition to the atmospheres of Mars and Venus. At that time Earth's principal atmospheric gas was a. nitrogen. * b. carbon dioxide. c. oxygen. d. water vapor. e. argon. 10. Source of argon, an inert gas, in the Earth's atmosphere is a. outgassing. b. photosynthesis. * c. radioactive decay of an isotope of potassium. d. the ocean. e. photodissociation of ozone. 11. Today, the principal source of atmospheric oxygen is a. outgassing. b. photodissociation of water vapor. * c. photosynthesis by plants. d. radioactive decay of soil. e. volcanic eruptions. 12. Some time in the Earth's past, carbon dioxide was an abundant gas in the atmosphere. The primary reason for its subsequent decline was a. removal by photosynthesis. b. photodissociation into carbon plus oxygen. c. chemical conversion to nitrogen. * d. cycling into the ocean and bedrock. e. None of the above is correct. 13. The portion of the atmosphere in which the principal gases (nitrogen and oxygen) occur everywhere in the same proportions is the a. troposphere. b. stratosphere. c. homosphere. * d. All of these are correct. e. None of these is correct. 14. The portion of the atmosphere in which the proportions of the principal gases (nitrogen and oxygen) change with altitude is a. below the stratopause. * b. the heterosphere. c. the homosphere. d. the troposphere. e. below the tropopause. 15. An atmospheric gas that varies significantly in concentration from one location to another near sea-level is a. nitrogen. b. oxygen. * c. water vapor. d. All of these are correct. e. None of these is correct. 16. The source(s) of atmospheric aerosols is (are) a. wind erosion of soil. b. forest fires. c. the spray of ocean waves. d. volcanic eruptions. * e. All of these are correct. 17. The importance of a gas or aerosol is to its relative abundance in the atmosphere. a. directly proportional * b. not necessarily related 18. A gas that occurs in minute concentrations in the atmosphere and yet shields living organisms from exposure to potentially lethal intensities of solar ultraviolet radiation is * a. ozone. b. water vapor. c. carbon dioxide. d. helium. e. nitrogen. 19. A gas that occurs in relatively low concentrations in the atmosphere and is required for photosynthesis is a. oxygen. b. argon. c. sulfur dioxide. d. hydrogen. * e. carbon dioxide. 20. During photosynthesis, green plants remove from the atmosphere and release to the atmosphere. a. oxygen..... carbon dioxide * b. carbon dioxide..... oxygen c. water vapor ... hydrogen d. ozone ... carbon dioxide e. nitrogen ... water vapor 21. All other factors being equal, a more C02-rich atmosphere is a _____ atmosphere. * a. warmer b. colder 22. Water vapor is * a. an invisible gas. b. uniformly distributed within the atmosphere. c. concentrated within the lower stratosphere. d. visible as clouds. e. the principal gas in the ionosphere. 23. The ozone shield occurs within that portion of the atmosphere known as the a. troposphere. * b. stratosphere. c. mesosphere. d. thermosphere. e. ionosphere. 24. Atmospheric aerosols a. are generated by both human activities and natural processes. b. may play a role in cloud formation. c. may influence air temperature. d. include sea-salt crystals. * e. All of the above are correct. 25. Air pollutants are gases or aerosols that a. occur in concentrations that threaten the well-being of living organisms, especially humans. b. often are normal components of the atmosphere. c. may disrupt the orderly functioning of the environment. * d. All of the above are correct. e. None of the above is correct. 26. Air pollution is __________ the consequence of human activity a. always * b. often but not always c. never 27. The single most important source of atmospheric pollution in the United States is (are) * a. transportation vehicles. b. wind erosion of soil. c. coal-burning electric power plants. d. garbage dumps. e. volcanic eruptions. 28. An example of a secondary air pollutant is (are) a. automobile exhaust, b. sulfur dioxide from coal burning. * c. smog. d. oxygen. e. dust from soil erosion. 29. A radiosonde is equipped with instruments that measure a. temperature. b. air pressure. c. humidity. * d. All of these are correct. e. None of these is correct. 30. Most weather is confined to that subdivision of the atmosphere known as the * a. troposphere. b. stratosphere. c. mesosphere. d. thermosphere. e. ionosphere. 31. Within the atmosphere, the lowest average air temperature occurs a. within the troposphere. b. at the tropopause. c. within the stratosphere. d. at the stratopause. * e. at the mesopause. 32. Air temperatures in the upper stratosphere are ____ air temperatures in the lower stratosphere. a. lower than * b. higher than c. about the same as 33. In the troposphere, air temperature _____ with increasing altitude. a. always increases b. always decreases c. usually increases * d. usually decreases e. does not change 34. The ionosphere a. occurs primarily within the troposphere. b. influences weather conditions at the Earth's surface. * c. features a relatively high concentration of electrically charged particles. d. is a subdivision of the homosphere. e. is not affected by the solar wind. 35. The northern lights are most likely to be seen a. near the equator. b. during daylight hours. * c. at high latitudes. d. in the Southwest. e. in New Mexico. 36. Normally rainwater is * a. slightly acidic. b. strongly acidic. c. strongly alkaline. d. slightly alkaline. e. chemically neutral. 37. A type of scientific model that has been used to forecast weather and climate is a a. physical model. b. graphical model. * c. numerical model. d. conceptual model. e. None of these is correct. 38. The most abundant gas in the Martian atmosphere is a. oxygen. b. argon. * c. carbon dioxide. d. nitrogen. e. methane. 39. The nation that was the first to orbit an artificial weather satellite was a. Great Britain. b. the former USSR. c. France. d. Egypt. * e. the United States. 40. Properties of the atmosphere are determined by a. radar. b. radiosondes. c. dropsondes. d. satellites. * e. All of these are correct. COMPLETION QUESTIONS 1. Climate is defined as average weather plus ____________ in weather behavior. 2. The atmosphere is a mixture of gases in which ____________ are suspended. 3. ____________ is the most abundant gas by percent volume within the homosphere. 4. With the coming of life on Earth, ____________ contributed oxygen to the atmosphere. 5. The ____________ is the thermal subdivision of the atmosphere in which virtually all weather takes place. 6. The ____________ contains minute concentrations of ____________ that protect life on Earth from exposure to dangerous levels of ultraviolet radiation. 7. The ionosphere is a site of electrons and ____________ charged ions. 8. Since the 1950s, computers programmed with numerical models of the atmosphere have been used to forecast the ____________. 9. A scientific model is an ____________ representation or simulation of the way a system works. 10. A radiosonde used to monitor upper-air winds is known as a ____________. 1. Climate is defined as average weather plus (extremes) in weather behavior. 2. The atmosphere is a mixture of gases in which (aerosols) are suspended. 3. Nitrogen is the most abundant gas by percent volume within the homosphere. 4. With the coming of life on Earth, photosynthesis contributed oxygen to the atmosphere. 5. The troposphere is the thermal subdivision of the atmosphere in which virtually all weather takes place. 6. The stratosphere contains minute concentrations of ozone that protect life on Earth from exposure to dangerous levels of ultraviolet radiation. 7. The ionosphere is a site of electrons and positively charged ions. 8. Since the 1950s, computers programmed with numerical models of the atmosphere have been used to forecast the weather. 9. A scientific model is an approximate representation or simulation of the way a system works. 10. A radiosonde used to monitor upper-air winds is known as a rawinsonde. ESSAY QUESTIONS 1. Describe the scientific method and the role played by scientific models in applying the scientific method. 2. Outline the major events in the evolution of the Earth's atmosphere. How does human activity play a role in this evolution? 3. Summarize the various techniques whereby data are gathered on the state of the atmosphere. 4. Explain why climate is sometimes described as the ultimate environmental control. 5. Describe some of the ways in which weather and climate affect the nation's economy and your daily life. Review Questions 1. Distinguish between weather and climate. Explain why a description of climate only in terms of average weather is incomplete and potentially misleading. 2. List some of the ways whereby the atmosphere sustains life on Earth. 3. In your own words, define the scientific method. What role is played by hypotheses in the scientific method? 4. What is a scientific model and what is its basic purpose? Identify some models that are useful in studying weather and climate. 5. How are numerical models used to predict future climate? 6. What role did outgassing play in the evolution of the Earth's atmosphere? 7. In the geologic past, carbon dioxide was the chief component gas of the Earth's atmosphere. What caused its concentration to decline? 8. How did the formation of oceans and the coming of life on the planet affect the evolution of the atmosphere? 9. Distinguish between the homosphere and the heterosphere. 10. Most aerosols in the atmosphere are products of activities at the Earth's surface. List several natural sources of aerosols. List some sources related to human activities. 11. Present several examples of how some minor constituents of the atmosphere are essential for continuation of life on Earth. 12. Under what conditions is a natural constituent (gas or aerosol) of the atmosphere considered to be an air pollutant? 13. In what way was invention of the radiosonde a major step forward in monitoring the atmosphere? 14. List some of the advantages of satellite observations of the atmosphere as contrasted with ground-based techniques of atmospheric monitoring. 15. In what ways does the troposphere differ from the stratosphere? 16. Why do air pollutants that enter the stratosphere tend to persist there for lengthy periods? 17. What is the ratio of nitrogen to oxygen in the troposphere? Does that ratio change within the stratosphere? 18. What is the source of ions within the ionosphere? 19. Why is the aurora visible only at high latitudes? 20. How and why does auroral activity vary with activity on the sun? Questions for Critical Thinking 1. Photosynthesis occurs chiefly during the growing season. Speculate on how variations in the rate of photosynthesis through the course of a year might influence the concentration of carbon dioxide in the atmosphere. 2. Why does a radiosonde balloon burst when it ascends to altitudes above about 30 km (19 mi)? 3. Speculate on how changes in the average temperature of the troposphere might affect the altitude of the tropopause. 4. Mountain tops are closer to the sun than are lowlands, and yet mountain tops are colder than lowlands. Why? 5. What does the usual temperature profile of the troposphere imply about the source of heat for the troposphere? ANSWERS TO REVIEW QUESTIONS 1. Weather is the state of the atmosphere at a particular place and time described in terms of such variables as temperature, wind, and cloudiness. Climate is the average weather plus extremes in weather at a particular place over some specified interval of time. Weather elements (such as temperature and precipitation) vary with time and hence, average values of weather elements provide an incomplete description of climate. Extreme values plus average values, however, convey the full range of expected variability of weather. 2. The atmosphere (a) shields living organisms from exposure to hazardous levels of ultraviolet radiation, (b) contains gases necessary for respiration and photosynthesis, and (c) provides the water essential for life. 3. The scientific method is a systematic form of inquiry that involves observation, speculation, and the formulation and testing of hypotheses. A hypothesis is an educated guess that suggests possible lines of inquiry. 4. Scientific models incorporate only the essential variables and provide an approximation of the way a system works. Many models are used in the study of weather and climate including graphical (weather maps), numerical (mathematical models of the atmosphere), and physical (tornado simulations). 5. A numerical model is used to simulate the present average state of the atmosphere. Then, some variable such as carbon dioxide concentration is altered. The model is run again to simulate the state of the atmosphere under the new conditions. 6. Outgassing is the ultimate source of carbon dioxide, nitrogen, water vapor, and many other atmospheric gases and aerosols. 7. Much of the original atmospheric carbon dioxide was cycled into ocean waters and ocean sediments thereby considerably reducing its atmospheric concentration. 8. Much of the original atmospheric carbon dioxide was absorbed in ocean waters or was locked up in marine sediments and sedimentary rocks. Furthermore, in those waters the first photosynthetic organisms evolved; most atmospheric oxygen is a byproduct of photosynthesis. 9. In the homosphere, the proportions of the chief atmospheric gases are constant. In the heterosphere, atmospheric gases are layered so that the concentrations of heavier gases decrease more rapidly with altitude than do concentrations of the lighter gases. 10. Forest fires, wind erosion of soil, and volcanic eruptions are some natural sources of atmospheric aerosols. Human activities that contribute aerosols to the atmosphere include industrial emissions and various agricultural practices. 11. Carbon dioxide is essential for photosynthesis; ozone formation within the stratosphere shields organisms from exposure to lethal intensities of ultraviolet (UV) radiation; some aerosols serve as nuclei for cloud formation. 12. A normal component of the atmosphere becomes an air pollutant when its concentration increases to a level that threatens the well-being of living organisms or disrupts the orderly functioning of the environment. 13. A radiosonde provides profiles of temperature, air pressure, and humidity from the Earth's surface up to an altitude of about 30 km (19 mi). The data are transmitted immediately to a ground station; no recovery of the recording instrument is necessary. 14. Remote sensing of the atmosphere by satellite provides a continuous field of view of the state of the atmosphere over a broad area. Other monitoring techniques (such as radiosondes or surface weather stations) provide weather information at discrete points within the atmosphere and may fail to detect small-scale systems such as severe thunderstorms. 15. Most weather, moisture, and clouds are confined to the troposphere. The stratosphere is above the weather and hence, features excellent visibility and generally smooth flying conditions. 16. There is little exchange of air between the stratosphere and the troposphere, so that exhaust gases emitted into the stratosphere by aircraft tend to remain there for extended periods. Furthermore, there is no rain or snow to wash air pollutants from the stratosphere. 17. The ratio of nitrogen molecules to oxygen molecules in the troposphere is about 4 to 1. This same proportionality also applies to the stratosphere. 18. Highly energetic solar radiation entering the upper atmosphere strips electrons from oxygen and nitrogen leaving them as positively charged ions. 19. The Earth's magnetic field channels some solar wind particles into belts centered on the Earth's geomagnetic poles so that the aurora is visible only at high latitudes. 20. The auroral oval shrinks when the sun is relatively inactive and expands equatorward with an increase in solar activity. An active sun features solar flares that produce a shock wave that propagates through the solar wind. Collision of the shock wave with the Earth's magnetosphere causes the auroral oval to expand. ANSWERS TO QUESTIONS FOR CRITICAL THINKING 1. Variations in the rate of photosynthesis through the year mean that the atmospheric carbon dioxide concentration declines into the growing season and recovers thereafter. 2. Air pressure, which we can think of as the weight of the overlying air, drops rapidly with increasing altitude. Hence, a balloon expands and eventually bursts as it ascends within the atmosphere because the air pressure acting on the balloon declines. 3. Air expands as it is heated. Hence, a warmer troposphere will have a higher tropopause. 4. Objects not only receive heat from the sun, they also lose heat to their surroundings. Apparently, cooling processes become more important with increasing altitude. We have more specifics on this observation in Chapters 2 and 3. 5. The highest average temperatures in the troposphere occur adjacent to the Earth's surface. Hence, the surface of the Earth is the principal source of heat for the troposphere. MONITORING THE WEATHER (DataStreme) CHAPTER 1 PROGRESS Directions: Please enter your responses to the following on the Response Form which appears in Study Guide, Part B: Applications, Chapter 1. 1. The first weather-related decision I made today was: __________________________________________________________________________ 2. NOAA Weather Radio (NWR) transmissions (can)(cannot) be received at the location of the school where I teach. There (is)(is not) a NWR receiver in my school. 3. Cable television's The Weather Channel is available at my (home)(school)(neither place). ** Questions 4 through 10 refer to Figure I.3 (text) and other text material in the Introduction. The figure depicts the most commonly used weather-map symbols as seen on television and in newspapers. 4. The H (or High) and L (or Low) symbols indicate regions where surface air pressures are high or low, respectively, compared to surrounding areas. An H is plotted where the air pressure is highest and an L is plotted where the air pressure is lowest. Proceeding outward and away from a high pressure system, the air pressure (falls)(rises)(does not change). As a low pressure system approaches your locality, the air pressure at your locality will (fall)(rise)(remain the same). 5. Assuming that the cold front continues to move toward the east, residents of coastal Virginia and the Carolinas can expect (higher)(lower) air temperatures in the next day or so. They might also experience (fog)(snow)(thunderstorms). 6. Over western Texas at map time the wind is probably blowing from the (south)(north). This. is described as a (south)(north) wind because, by convention, the wind is named for the direction (toward which)(from which) it blows. 7. A cold front and a warm front are linked to the L (low-pressure system) over lower Michigan. The symbols identifying the fronts imply that those fronts are rotating in a (clockwise), (counterclockwise) direction about the L. 8. The weather map indicates that stormy weather is more likely to be taking place at locations near the centers of (Highs)(Lows). 9. The surface air pressure in Indiana is probably moving generally (rising)(falling) because the L in Michigan is likely moving (eastward)(westward). 10. The coldest air is located to the (northwest)(southeast) because of the L over lower Michigan. 11. Fronts are boundaries between air masses that usually contrast in temperature. Above the Earth's surface, fronts slope upward and over the (colder)(warmer) air. 12. Air pressure always (increases)(decreases) with increasing altitude. CHAPTER PROGRESS: (Answers) [as appropriate by participant] [as appropriate by participant] [as appropriate by participant] falls, fall lower, thunderstorms south, south, from which counterclockwise Lows rising, eastward northwest colder decreases CHAPTER 16 (Moran and Morgan, 1997) WEATHER ANALYSIS AND FORECASTING With this chapter, we close our study of the basic concepts of meteorology with a description of the steps involved in the preparation of weather forecasts. First we consider how data are gathered via surface and upper-air observations with a special focus on weather satellites. We then show how weather data are plotted on maps for analysis by meteorologists and input into computerized numerical models of the atmosphere. Next, we describe forecast methodology and discuss forecast skill and the techniques and challenges of long-range forecasting. The chapter concludes with a discussion of how weather information reaches the public. CHAPTER OBJECTIVES After reading this chapter, the student should be able to: describe how weather data are obtained from the surface and upper atmosphere. compare and contrast geosynchronous and polar-orbiting weather satellites. list the advantages of weather satellite observations. explain the difference between surface weather maps and upper-air weather maps. describe the complementary roles of meteorologists and computers in weather data analysis and forecasting. explain how and why forecast skill changes with length of the forecast period. explain how meteorologists prepare long-range weather forecasts. describe the significance of teleconnections in seasonal weather forecasting. summarize how each of us can make reasonably accurate single-station weather forecasts. review prospects for future improvement in weather forecast skill. MULTIPLE CHOICE QUESTIONS 1. On average, 24-hour forecasts issued by the National Weather Service are correct about ____________ of the time. a. 100% * b. 85 % c. 50% d. 25 % e. 2% 2. A World Meteorological Center is located at a. Washington, DC b. Moscow, Russia. c. Melbourne, Australia. * d. All of these are correct. e. None of these is correct. 3. Weather forecasting requires a. acquisition of present weather data on the state of the atmosphere. b. depiction of observational data on weather maps. c. analysis of weather data and prediction. d. dissemination of weather information and forecasts to users. * e. All of the above are correct. 4. Weather stations gather data for a. preparation of weather maps and forecasts. b. exchange of weather information with other nations. c. use by aviation. * d. All of the above are correct. e. None of the above is correct. 5. At 0900 UTC, it is ____________ Eastern Standard Time (EST) in Boston, Massachusetts. a. midnight * b. 4 A.M. c. 9 A.M. d. 2 P.M. e. None of these is correct. 6. At 1200 UTC, it is ____________ Central Standard Time (CST) in Chicago, Illinois. a. midnight * b. 6 A.M. c. 7 A.M. d. noon e. 6 P.M. 7. New automated instrumentation at National Weather Service stations: a. AWIPS * b. ASOS 8. As part of its modernization efforts, the National Weather Service a. has phased out conventional weather radar in favor of radar that can operate in either the reflectivity or Doppler mode. b. is replacing manually operated weather stations with automated weather station c. is installing ASOS. d. is installing AWIPS. * e. All of the above are correct. 9. Across the United States, weather is continuously monitored at nearly 1000 stations. These weather stations are operated by a. the National Weather Service (NWS). b. the Federal Aviation Administration (FAA). c. private businesses and individuals in cooperation with the National Weather Service. * d. All of the above are correct. e. None of the above is correct. 10. Universal Coordinated Time (UTC) is the world standard time for weather observations. It is measured at a longitude of * a. zero degrees. b. 45 degrees W. c. 90 degrees W. d. 180 degrees W. e. 90 degrees E. 11. Weather stations in the NWS Cooperative Observer Network provide weather data primarily for a. weather forecasting. b. aviation. * c. hydrologic, agricultural, and climatic purposes. d. television weather broadcasts. e. the NOAA weather radio broadcasts. 12. Radiosondes provide continuous vertical profiles of a. temperature. b. relative humidity. c. air pressure. * d. All of these are correct. e. None of these is correct. 13. By international agreement, radiosonde balloons are launched everywhere at the same time at ____________ intervals. a. one-hour b. two-hour c. six-hour * d. 12-hour e. 24-hour 14. Polar-orbiting weather satellites view a particular locality ____________ every 24-hour day. a. once * b. twice c. three times d. four times 15. Geosynchronous (geostationary) weather satellites a. follow longitudinal trajectories over the poles. b. orbit the Earth at altitudes of 800 to 1000 km. * c. are situated over the equator and orbit eastward at the same rate as the Earth rotates. d. monitor all of the Earth's surface at one time. e. None of the above is correct. 16. The subsatellite point of a geosynchronous satellite a. is situated on the equator. b. has a fixed latitude and longitude. c. does not move because the satellite orbits toward the east at the same rate as the Earth rotates. * d. All of the above are correct. e. None of the above is correct. 17. The principal advantage of weather satellites over a network of surface weather stations is * a. satellites provide a continuous field of view of the atmosphere and Earth's surface. b. satellites detect synoptic-scale weather systems. c. satellites more accurately measure surface air temperatures. d. All of the above are correct. e. None of the above is correct. 18. Sensors aboard weather satellites intercept a. solar radiation reflected by clouds. b. infrared radiation emitted by the Earth-atmosphere system. c. visible radiation scattered to space by atmospheric aerosols. d. infrared radiation emitted by clouds to space. * e. All of the above are correct. 19. Sensors aboard weather satellites can monitor temperatures of the Earth-atmosphere system. Such sensors measure what type of radiation? * a. emitted infrared b. visible c. reflected solar d. radio waves e. gamma rays 20. Reduction of air pressure observations to sea level is intended to remove the influence of ____________ on barometer readings. a. temperature b. wind speed c. humidity * d. station elevation e. wind convergence 21. Lines of equal pressure on a weather map are called a. isotherms. * b. isobars. c. contours of elevation. d. isohyets. e. None of these is correct. 22. Isobars a. never cross. b. maybe parallel. c. by convention are drawn at 4-mb intervals on a surface weather map. d. join locations reporting the same barometer readings (after reduction to sea level). * e. All of the above are correct. 23. The percentage of the atmosphere's mass that is located above the 700-millibar level: a. 100% * b. 70 % c. 30% d. 50 % e. 10% 24. About ____________ percent of the atmosphere's mass is located under the 200-millibar level. a. 98 * b. 80 c. 20 d. 8 e. 2 25. Which one of the following pressure systems does not appear at the 500-mb level? a. midlatitude migrating cyclone b. Pacific high c. Icelandic low * d. Arctic high e. Alberta low 26. In winter, a cold 500-mb trough tends to develop over a. oceans. * b. continents. 27. An anticyclone that appears on a 500-mb map occupies a column of relatively a. cold air. * b. warm air. c. dry air. 28. Simultaneous advection of warm air into upper-air ridges and advection of cold air into upper-air troughs favor a. zonal air flow. b. fair weather. c. improving weather. * d. meridional air flow. e. None of these is correct. 29. Differences in altitude of the 500-mb surface from one place to another can be explained primarily by differences in mean ____________ of the air below the 500-mb surface. a. humidity * b. temperature c. wind speed d. wind direction e. None of these is correct. 30. At the 500-mb level, the air column under a ridge is ____________ the air column under a trough. * a. warmer than b. colder than c. about the same temperature as 31. An upper-air trough may be linked to a surface a. warm-core cyclone. * b. wave cyclone. c. warm-core anticyclone. d. cold-core anticyclone. e. None of these is correct. 32. The scale of atmospheric circulation that is most important in forecasting tomorrow's weather is a. mesoscale. b. microscale. * c. synoptic-scale. d. planetary-scale. 33. Over the course of a year, daily weather exhibits a ____________ weather bias. * a. fair b. stormy 34. When hazardous weather is considered possible based on current or anticipated atmospheric conditions, a weather ____________ is issued. a. alert * b. watch c. warning d. advisory 35. A linkage between weather changes occurring in widely separated regions of the globe: a. atmospheric teleconnection b. southern oscillation c. seesawing of surface air pressure between Darwin and Tahiti. * d. All of the above are correct. e. None of the above is correct. 36. Source(s) of weather information for the general public is (are) a. NOAA weather radio. b. cable-TV weather channels c. radio and newspapers. d. commercial television. * e. All of the above are correct. 37. Weather watches and warnings are issued for a. tornadoes. b. hurricanes. c. floods. d. winter storms. * e. All of these are correct. 38. The 500-mb surface is ____________ the friction layer. a. within * b. above 39. Forecasting the track of a hurricane is based on a. records of tracks of similar hurricanes of the past. b. numerical models of the atmosphere. c. the experience of the forecaster. * d. Some combination of the above. e. None of the above is correct. 40. Numerical models have been used to successfully predict a. the weather of the next 24-hours. b. the coastal region to be affected by a hurricane storm surge. c. the onset of an extreme El Niño. * d. All of the above is correct. e. None of the above is correct. COMPLETION QUESTIONS 1. Upper-air weather observations are obtained using a ____________. 2. A ____________ satellite orbits the Earth and continuously monitors the same portion of the Earth's surface. 3. A ____________ satellite monitors the same location on the Earth's surface twice each 24-hour day. 4. Surface weather data are plotted on a constant altitude surface whereas upper-air weather data are plotted on constant ____________ surfaces. ·5. Cold air advection lowers the 500-mb altitude and ____________ upper-air troughs. 6. Midlatitude shifts in weather from one episode to another are due to changes in the upper-air ____________ wave ____________. 7. The altitude of a pressure surface varies from one place to another primarily because of differences in average ____________ of air below the pressure surface. 8. A 500-mb trough may be linked to a ____________ at the surface. 9. Over the past three decades, the accuracy of short-term weather forecasting has shown slow but steady ____________. 10. A ____________ is a linkage between weather changes occurring in widely separated regions of the globe. 1. Upper-air weather observations are obtained using a radiosonde. 2. A geosynchronous satellite orbits the Earth and continuously monitors the same portion of the Earth's surface. 3. A polar-orbiting satellite monitors the same location on the Earth's surface twice each 24-hour day. 4. Surface weather data are plotted on a constant altitude surface whereas upper-air weather data are plotted on constant pressure surfaces. ·5. Cold air advection lowers the 500-mb altitude and strengthens upper-air troughs. 6. Midlatitude shifts in weather from one episode to another are due to changes in the upper-air westerly wave pattern. 7. The altitude of a pressure surface varies from one place to another primarily because of differences in average temperature of air below the pressure surface. 8. A 500-mb trough may be linked to a wave cyclone at the surface. 9. Over the past three decades, the accuracy of short-term weather forecasting has shown slow but steady improvement. 10. A teleconnection is a linkage between weather changes occurring in widely separated regions of the globe. ESSAY QUESTIONS 1. Explain why weather forecasting requires international cooperation. 2. What advantages do geosynchronous weather satellites offer over polar-orbiting satellites? 3. How can a weather satellite see at night? 4. Speculate on why the atmosphere exhibits a fair-weather bias. 5. What is meant by weather forecasting based on persistence? Provide specific examples. Review Questions 1. Why does weather forecasting require international cooperation? 2. Describe the principal steps involved in the preparation of weather forecasts. 3. Why do airport weather stations report altimeter settings for aircraft? 4. What is Greenwich Mean Time (GMT)? 5. What is your local time at 0100 UTC? 6. What is the chief purpose of the NWS Cooperative Observer Network? In what sense is die network cooperative? 7. What advantages do satellites bring to weather observation? 8. Distinguish between a satellite in polar orbit and a satellite in geosynchronous orbit. 9. Why do polar-orbiting satellites provide greater spatial resolution than geosynchronous satellites? 10. What is the basic difference between surface weather maps and upper-air weather maps? 11. What is meant by a numerical model of the atmosphere? 12. Why does the reliability of numerical weather prediction deteriorate for forecast periods beyond 48 hr? 13. Why are computerized weather forecasts not likely to replace human weather forecasters? Provide some illustrations. 14. Describe the basis for long-range (monthly, seasonal) weather forecasts. 15. What is a teleconnection? Describe how teleconnections aid long-range weather forecasting. Provide a specific example. 16. Speculate on how long-term weather records could be used to formulate seasonal weather forecasts. 17. Explain why there is a linkage between sea-surface temperatures and planetary-scale atmospheric circulation patterns. 18. An episode of one weather type usually gives way to another weather type very abruptly-in a single day or less. Explain why. 19. What is meant by fair-weather bias? 20. Distinguish between weather watches and weather warnings. Questions for Critical Thinking 1. Explain how weather satellites are able to provide nighttime observations of cloud cover. 2. Explain why warm air advection causes the 500-mb surface to rise and why cold air advection causes the 500-mb surface to lower. 3. Explain why cold-core anticyclones and warm-core cyclones do not appear on 500-mb maps. 4. Why are winds associated with contour gradients on upper-air weather maps? 5. On average in midlatitudes in summer, a 500-mb ridge develops over the continents and a 500-mb trough occurs over the oceans. In winter, it's just the reverse: A 500-mb trough develops over the continents and a 500-mb ridge occurs over the oceans. Please explain. ANSWERS TO REVIEW QUESTIONS 1. Weather systems know no political boundaries; the atmosphere is continuous. Hence, weather forecasting requires international cooperation. 2. Acquisition of weather data, depiction of weather data on weather maps, and analysis of weather maps are the principal steps involved in the preparation of weather forecasts. 3. Such information enables pilots to more accurately calibrate the altimeter aboard their aircraft. 4. UTC is the time at the Old Royal Observatory at Greenwich, England (located at the prime meridian). 5. For reference, at 0600 UTC, it is midnight Central Standard Time (CST). 6. Participants monitor weather for hydrologic, agricultural, and climatic purposes. The network is cooperative in that participants volunteer their time and labor and the National Weather Service supplies equipment and data management. 7. Weather satellites observe a broad sector of the Earth continuously and can see weather systems that escape direct observation by weather observing networks-especially over the ocean. 8. A satellite in polar orbit follows longitudinal trajectories over the polar regions. A geosynchronous satellite orbits the Earth at the same rate as the Earth rotates so that a geosynchronous satellite always observes the same portion of the Earth's surface. Furthermore, a geosynchronous satellite orbits at much higher altitudes than does a polar-orbiting satellite. Hence, sensors aboard a polar-orbiting satellite provide greater resolution. 9. Polar-orbiting weather satellites provide greater spatial resolution because they orbit at much lower altitudes than do geosynchronous satellites. 10. Surface weather maps are constant altitude (sea-level) depictions of weather data. Upper-air weather maps are constant pressure (isobaric) depictions of weather data. 11. A numerical model of the atmosphere consists of a series of equations that approximates the behavior of the atmosphere and can be used for predictive purposes. 12. Numerical models are only approximations of atmospheric behavior. Also, stations within weather observing networks are so widely spaced that some weather systems escape detection and this information may not be available to the numerical model. 13. Local conditions can modify computerized weather forecasts. For example, a sea breeze or lake-effect snowfall might not be anticipated by a large-scale numerical model of the atmosphere. Also, an experienced meteorologist learns the weaknesses or biases of predictive models. 14. Fundamentally, long-range forecasts attempt to predict the locations of anomalies in temperature and precipitation and are based on an extrapolation into the future of circulation features known to persist. 15. A teleconnection is a linkage between weather changes occurring in widely separated regions of the globe. Hence, for example, an extreme El Nina may be accompanied by specific anomalies in certain regions of the world. Hence, teleconnections aid long-range weather forecasting. 16. Long-term weather records likely contain analogues of present weather patterns. Hence, a forecast could be based on recognition of precursors to that weather pattern. 17. There is a continual exchange of heat and moisture between the atmosphere and the ocean. Hence, changes in sea-surface temperature affects the temperature of the overlying air column and hence, the planetary-scale circulation pattern. We can think of spatial anomalies in sea-surface temperature as selecting for certain wave patterns in the westerlies. 18. Upper-air weather patterns can change abruptly so that episodes of weather types also shift abruptly. 19. Fair-weather days out-number stormy days just about everywhere. 20. A weather watch is issued when hazardous weather is considered possible based on current or anticipated atmospheric conditions. A weather warning is issued when hazardous weather is likely or is actually occurring somewhere in the region. ANSWERS TO QUESTIONS FOR CRITICAL THINKING 1. Weather satellites are equipped with infrared sensors that monitor IR emitted by clouds and the Earth's surface. Temperatures can then be deduced from radiation emissions. Recall that IR is emitted continually and that the wavelength of peak radiation intensity is temperature-dependent. 2. Air pressure falls more rapidly with altitude in cold, dense air than in warm, light air. Hence, air mass advection can affect the altitude of isobaric surfaces such as the 500-mb surface. Warm air advection causes the 500-mb surface to rise and cold air advection causes the 500-mb surface to drop. 3. Cold-core anticyclones and warm-core cyclones are shallow systems that do not reach the 500-mb level. Refer back to the discussion in Chapter 11. 4 Contour gradients are caused by horizontal temperature gradients that, in turn, produce horizontal pressure gradients. Hence, winds are associated with contour gradients on upper-air weather maps. 5. The surface of the continents warms up more than the ocean surface during summer. And, the surface of continents cools down more than the ocean surface during winter. Surface temperatures affect the temperature of the overlying air and hence, the altitude of pressure surfaces. MONITORING THE WEATHER SYNOPTIC WEATHER OBSERVATIONS & ANALYSIS THE TOOLS Weather Instruments to include surface, satellites, radar, radiosondes. WEATHER MAPS Isobars and Isotherms REVIEW QUESTIONS/STUDY GUIDE Are you able to answer the following? Name three weather elements that meteorologists routinely measure. What weather elements are measured by a radiosonde? Compare the observation capabilities of polar orbiting and geosynchronous satellites. What three types of satellite images are available to the meteorologist and how can these products be used? How is radar used to sense the weather? Briefly describe the principles utilized by conventional and Doppler weather radar units. How does Doppler radar differ from conventional weather radar systems?