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C h a p t e r
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Introduction to Climatology
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those specializing in glaciology, as well as specialNOT FOR SALE OR DISTRIBUTION Chapter at a Glance ized physical geographers, geologists, and oceanMeteorology and Climatology ographers. The biosphere, which crosscuts the Scales in Climatology lithosphere, hydrosphere, cryosphere, and atmoSubfields of Climatology sphere, includes the zone containing all life forms © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLCThe biosphere Climatic Records and Statistics on the planet, including humans. NOT FOR SALE Summary OR DISTRIBUTION NOT FOR SALEby OR DISTRIBUTION is examined specialists in the wide array of life Key Terms sciences, along with physical geographers, geoloReview Questions gists, and other environmental scientists. Questions for Thought The atmosphere is the component of the system studied by climatologists © and meteorologists. Ho- Learning, LLC © Jones & Bartlett Learning, LLC Jones & Bartlett listic interactions between the atmosphere and NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Climatology may be described as the scientific each combination of the “spheres” are important study of the behavior of the atmosphere—the contributors to the climate (Table 1.1), at scales thin gaseous layer surrounding Earth’s surface— from local to planetary. Thus, climatologists must integrated over time. Although this definition is draw on knowledge generated in several natural © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC certainly acceptable, it fails to capture fully the and sometimes social scientific disciplines to unNOTscope FORofSALE OR DISTRIBUTION FOR SALE DISTRIBUTION the processes at workOR in the atmosphere. climatology. Climatology is a holistic derstandNOT science that incorporates data, ideas, and theo- Because of its holistic nature of atmospheric propries from all parts of the Earth–ocean–atmosphere erties over time and space, climatology naturally system, including those influenced by humans, falls into the broader discipline of geography. Over the course of this book we shall see that intoLearning, an integrated whole to explain atmospheric © Jones & Bartlett LLC © Jones & Bartlett Learning, LLC these processes can be complex. The effects of NOT FOR SALE properties. OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The Earth–ocean–atmosphere system may be some of these interactions cascade up from local divided into a number of zones, with each tradi- to planetary scales, and the effects of others tend tionally studied by a separate scientific discipline. to cascade down the various scales to ultimately The part of the solid Earth nearest to the surface (to affect individual locations over time. The processes © Jones Bartlett Learning, © Jones & Bartlett are so interrelated with other spheres and with Learning, LLC a depth of perhaps 100&km) is called the litho- LLC other scales that it is often NOT difficult to generalize by DISTRIBUTION sphere and NOT is studied by geologists, geophysicists, FOR SALE OR FOR SALE OR DISTRIBUTION saying that any particular impact begins at one geomorphologists, soil scientists, vulcanologists, and other practitioners of the environmental and component of the system or side of the scale and agricultural sciences. The part of the system that is proceeds to another. We can state that the scope of climatology is covered by liquid water is termed the hydrosphere; © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC it is considered by those in the fields of oceanogra- broad. It has also expanded widely from its roots NOTphy, FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION hydrology, and limnology (the study of lakes). in ancient Greece. The term “climatology” is deThe region comprising frozen water in all its forms rived from the Greek term “klima,” which means (glaciers, sea ice, surface and subsurface ice, and “slope,” and reflects the early idea that distance snow) is known as the cryosphere and is studied by from the equator alone (which causes differences
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Meteorology and Climatology
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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Table 1.1 Examples of Interactions Between the Atmosphere and FOR the Other “Spheres” Impacts NOT SALE ORand DISTRIBUTION NOT FOR SALE OR DISTRIBUTION on Thermal Receipt/Climate Sphere Interacting with Atmosphere
Example of a Potential Impact
Lithosphere
Large volcanic eruptions can create a dust and soot cloud that can reduce the receipt
Hydrosphere
of solar Learning, radiation, coolingLLC the global atmosphere for months or © Jones & Bartlett ©years. Jones & Bartlett Learning, LLC Changes ocean circulation can cause global atmospheric circulation shifts that NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR inDISTRIBUTION produce warming in some regions and cooling in others.
Cryosphere
Melting of polar ice caps can cause extra heating at the surface where ice was located because bare ground reflects less of the solar energy incident upon the surface than ice.
Biosphere
Deforestation increases the amount of solar energy received at the surface and alters © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC atmospheric chemistry by returning carbon dioxide stored in living plant matter to NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the atmosphere.
in the angle or slope of the Sun in the sky) drove meteorology involves only the present, the immeclimate. The second part of the word is derived diate past, and the very near future. © Jones & Bartlett Learning, & Bartlett Learning, LLC of mefrom “logos,” defined asLLC “study” or “discourse.” Mod- © Jones But a much more important component NOT FOR SALE OR DISTRIBUTION FORisSALE OR DISTRIBUTION ern climatology seeks not only to describe the na- NOT teorology the examination of the forces that creture of the atmosphere from location to location ate the atmospheric properties being measured. over many different time scales but also to explain Changes in the magnitude or direction of these why particular attributes occur and change over forces over time and changes in the internal proptime and to assess potential impacts of those erties of the matter being affected by these&forces © the Jones & Bartlett Learning, LLC © Jones Bartlett Learning, LLC changes on natural and social systems. create differences in weather conditions over time. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Although many meteorologists are not directly ■■Meteorology and Climatology involved with forecasting these changes, meteo rology is the only natural science in which a priThe two atmospheric sciences, meteorology and mary goal is to predict future conditions. Weather © Jones &are Bartlett Learning, LLC Jones greatly & Bartlett Learning, climatology, inherently linked. Meteorology forecasting has©improved with recent tech- LLC FOR of SALE OR DISTRIBUTION NOT FORthat SALE DISTRIBUTION isNOT the study weather—the overall instanta- nological enhancements allowOR for improved neous condition of the atmosphere at a certain understanding of these forces, along with improved place and time. Weather is described through the observation, data collection, and modeling of the direct measurement of particular atmospheric atmosphere. Currently, weather forecasts proproperties such as temperature, precipitation, duced by the National Weather Service in the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC humidity, wind direction, wind speed, cloud United States are accurate for most locations over a NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION cover, and cloud type. The term “weather” refers period of approximately 72 hours. By contrast, climate refers to the state of the to tangible aspects of the atmosphere. A quick look or walk outside may be all that is needed to atmosphere for a given place over time. It is imdescribe the weather of your location. Of course, portant to note that climatologists are indeed conprocesses that these observations may be & compared the cerned © Jones Bartlettwith Learning, LLCwith the same atmospheric © Jones & Bartlett Learning, LLC meteorologists study, but the NOT scope FOR is different. state of the atmosphere at other locations, SALE OR DISTRIBUTION NOT FOR SALE OR which DISTRIBUTION Meteorologists may study the processes for their in most cases is different. Because meteorology deals with direct and spe- own sake, while climatologists study the processes cific measurements of atmospheric properties, dis- to understand the long-term consequences of cussion of weather centers on short-duration time those processes. Climatology, therefore, allows © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC intervals. Weather is generally discussed over time us to study atmospheric processes and their imNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION spans of a few days at most. How is the weather pacts far beyond present-day weather. There are three properties of climate data to contoday? How does this compare with the weather we had yesterday? What will the weather be like to- sider: normals, extremes, and frequencies. These morrow or toward the end of the week? All of these are used to gauge the state of the atmosphere over a periodLearning, as compared with atmoquestionsLearning, involve short-term © Jones & Bartlett LLC analysis of atmo- ©particular Jones &time Bartlett LLC spheric conditions similar time period in the spheric properties for a given time and place. So NOT NOT FOR SALE OR DISTRIBUTION FOR SALEover ORaDISTRIBUTION
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C h a p t e r 1 — Introduction to Climatology
© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC but also in theOR otherDISTRIBUTION “spheres” because the interacpast. Normals refer to average weather conditions NOT FOR SALE NOT FOR SALE OR DISTRIBUTION
at a place. Climatic normals are typically calculated tions between the atmosphere and the other spheres for 30-year periods and give a view of the type of ex- are more likely to have important consequences pected weather conditions for a location through over longer, rather than shorter, time scales. This is the course of a year. For example, climatologically particularly true if those processes occur over large © Jones & Bartlett Learning, © usually Jonestake & Bartlett areas, because the impacts longer to Learning, LLC normal conditions in Crestview, Florida, are hotLLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION and humid during the summer and cool but not develop in such cases. For instance, if the Great Lakes were to totally evaporate, such a process cold in winter. Two places could have the same average condi- would necessarily take place over a long time petions but with different ranges of those conditions, riod. The difference in water level in the Great Lakes today and &tomorrow not cause in the same way thatLearning, two studentsLLC who both have between © © Jones & Bartlett Jones Bartlettwould Learning, LLC much impact on tomorrow’s weather as compared an average of 85 percent in a class may not have acNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION quired that average by earning the same score on with today’s. A meteorologist would, therefore, not each graded assignment. Therefore, extremes are really need to take this atmosphere–hydrosphere used to describe the maximum and minimum interaction into account when considering tomormeasurements of atmospheric variables that can row’s weather. However, the difference in water © Jones & Bartlett Learning, LLCat a certain place and time, © Jones & Bartlett LLC be expected to occur content between Learning, the Great Lakes over centuries is NOT FOR SALE based OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION on a long period of observations. For exam- more likely to have a noticeable and dramatic imple, a temperature of 0°C (32°F) at Crestview in pact on climate during that time period. InteracApril would fall outside of the range of expected tions between the atmosphere and other spheres, such as in this example, thus must be considered temperatures. when evaluating climate. © Jones & Bartlett Learning, LLC Finally, frequencies to theLearning, rate of inci-LLC © Jones &refer Bartlett Regardless of the differences between meteo dence of a particular phenomenon at a particular NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION place over a long period of time. Frequency data rology and climatology, it is important to recognize are often important for risk assessment, engineer- that the distinction between the two is becoming ing, or agricultural applications. For instance, the increasingly blurred over time. A successful climafrequency of hailstorms in a city is a factor in de- tologist should have a firm grounding in the laws of © Jones & Bartlett Learning, LLC © Jones LLC physics & andBartlett chemistryLearning, that dictate the termining a homeowner’s insurance premium. Or atmospheric NOTif FOR SALEdesigns OR DISTRIBUTION NOT behavior FOR SALE DISTRIBUTION of the OR atmosphere. An efan engineer a culvert to accommodate instantaneous 8 cm (3 in.) of rain in a 5-hour period but that fre- fective meteorologist should recognize the imporquency is exceeded an average of two times per tance of patterns over time and the impacts of those year, this rate of failure may or may not be accept- patterns and the influence of other components of able to the citizens affected by the culvert. A farmer the Earth–ocean–atmosphere system. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The holistic perspective of climatology also carmay want to know how many days on average have NOT FOR SALE more OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION than 1.5 cm (0.6 in.) of rain in October be- ries over to include interactions between the atmocause October rains are problematic for any crop sphere and social systems. The impact of people on harvested during that month. their environment is a theme in climatology that We can say then that both meteorologists and has become more prevalent in recent years. It is © Jones & same Bartlett Learning, © Jones & Bartlett climatologists study the atmospheric pro- LLC being increasingly recognized that many features Learning, LLC cesses but with three primary and important dif- of the human condition are related to climate. NOT FOR SALEThis OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ferences. First, the time scales involved are is especially true of climatic “extremes” and “fredifferent. Meteorologists are primarily concerned quencies,” because it is the “abnormal” events, and with features of the atmosphere at a particular time conditions exceeding certain thresholds, that genand place—the “weather”—whereas climatologists erally cause the greatest impact on individuals and © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC study the long-term patterns and trends of those society. NOTshort-term FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION features—the “climate.” Second, meteorologists are more concerned with the processes for ■■Scales in Climatology their own sake, while climatologists consider the long-term implications of those processes. Third, We have already stated the importance of temporal scale in climatology. It isLLC also important to climatology is inherently more intertwined © with © Jones & Bartlett Learning, LLC Jones & Bartlett Learning, emphasize climatology involves the study of happening not only in the atmosphere NOT FOR SALE processes OR DISTRIBUTION NOT FOR SALEthat OR DISTRIBUTION
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Subfields of Climatology
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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC withFOR their associated fronts fall into the synoptic atmospheric phenomena along many different NOT SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION
spatial scales. There is usually a direct relation- scale. Because these phenomena are quite freship between the size of individual atmospheric quent and directly affect many people, the synopphenomena and the time scale in which that phe- tic scale is perhaps the most studied spatial scale nomenon occurs (Figure 1.1). The microscale in the atmospheric sciences. © Jones Bartlett Learning, LLC ©view Jones & Bartlett Learning, LLC Finally, we can also study and climate over represents the smallest of all&atmospheric scales. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Phenomena that operate along this spatial scale an entire hemisphere or even the entire globe. are smaller than 0.5 km (0.3 mi) and typically last This represents the largest spatial scale possible from a few seconds to a few hours. A tiny circula- and is termed the planetary scale, because it ention between the underside and the top of an indi- compasses atmospheric phenomena on the order of (6000 to mi). Because in LLC vidual leaf & falls into this category, LLC as does a 10,000 to 40,000©km © Jones Bartlett Learning, Jones &24,000 Bartlett Learning, general the largest spatial systems operate over the tornado funnel cloud, and everything between. A NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION larger scale is the local scale, which operates over longest time scales, it is no surprise then that planeareas between about 0.5 and 5 km (0.3 to 3 mi)— tary-scale systems operate over temporal scales that about the size of a small town. A typical thunder- span weeks to months. Examples of planetary-scale systems include the broad wavelike flow in the upstorm falls into this spatial scale. © Jones & Bartlett Learning, LLC Jones & Bartlett LLCpressure atmosphere and theLearning, major latitudinal The next spatial scale is the mesoscale, which © per NOT FOR SALE ORsystems DISTRIBUTION FORbelts SALE DISTRIBUTION and wind that OR encircle the planet. involves that operate over areas between NOT about 5 and 100 km (3 to 60 mi) and typically last from a few hours to a few days. Such systems include ■■Subfields of Climatology those you may have encountered in earlier coursework, such as the mountain/valley breeze and land/ Climatology can be divided into©several © Jones & Bartlett Learning, LLC Jonessubfields, & Bartlett Learning, LLC sea breeze circulation systems, clusters of interactsome of which correspond to certain scales of anal- OR DISTRIBUTION NOT FOR SALE NOT FOR SALE OR DISTRIBUTION ing thunderstorms known as mesoscale convective ysis. For instance, the study of the microscale procomplexes, a related phenomenon associated with cesses involving interactions between the lower cold fronts termed “mesoscale convective systems,” atmosphere and the local surface falls into the and the central region of a hurricane. realm of boundary-layer climatology. This subfield © Moving Jonestoward & Bartlett Learning, we LLC © Jones & Bartlett larger phenomena, come to is primarily concerned with exchangesLearning, in energy, LLC NOT FOR scale, SALE OR DISTRIBUTION NOT FOR OR DISTRIBUTION the synoptic a spatial scale of analysis that matter (especially water), andSALE momentum near the functions over areas between 100 and 10,000 km surface. Physical processes can become very com(60 to 6000 mi). Systems of this size typically oper- plex in the near-surface “boundary layer” for two ate over periods of days to weeks. Entire tropical reasons. First, the decreasing effect of friction from cyclone systems and midlatitude (frontal) cyclones the surface upward complicates the motion of the
Temporal Scale (seconds)
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Atmospheric planetary waves
106 10
5
104
Hurricane
Midlatitude cyclone
© Jones & Bartlett Learning, LLC Land/sea breeze NOT FOR SALE OR DISTRIBUTION
Tornado 10 Dust devil Turbulence in an urban city street 102 © JonesMicroturbulence & Bartlett Learning, LLC 101 FOR SALE OR DISTRIBUTION NOT Micro 100 .00001 .0001 .001 .01 .1
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Thunderstorm
3
Local 1
Meso 10
© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Synoptic
100
1,000
Planetary
10,000
100,000
Spatial Scale (km)
© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC FigureOR 1.1 DISTRIBUTION Spatial–temporal relationships for selected atmospheric features. NOT FOR SALE NOT FOR SALE OR DISTRIBUTION
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6
C h a p t e r 1 — Introduction to Climatology
© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC and the surface of a region.” He atmosphere and involves significant transfer of FOR NOT SALE OR environment DISTRIBUTION NOT FOR SALE OR DISTRIBUTION
momentum downward to the surface. Second, the goes on to state that, “because synoptic climatolmost vigorous exchanges of energy and moisture ogy seeks to explain key interactions between occur in this layer because solar radiant energy the atmosphere and surface environment, it has striking the ground warms it greatly and rapidly great potential for basic and applied research in © Jones & Bartlett Learning, © Jones & Bartlett the environmental sciences.” Synoptic climatol- Learning, LLC compared with the atmosphere above it and be-LLC NOT FOR SALE NOT FOR SALE OR DISTRIBUTION at- DISTRIBUTION cause the source of water for evaporation is at the ogy may act as a keystone that links studies of OR surface. Boundary-layer climatology may be fur- mospheric dynamics with applications in various ther subdivided into topics that examine surface– other disciplines. Synoptic climatology is similar in some ways to atmosphere interactions in mountain/alpine reregional climatology, description of the climate gions, urban landscapes, or various vegetated © Jones & Bartlett Learning, LLC © Jones & aBartlett Learning, LLC of a particular region of the surface. However, synland covers. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Physical climatology is related to boundary- optic climatology necessarily involves the explalayer climatology in that it studies energy and mat- nation of process, whereas regional climatology ter. However, it differs in that it emphasizes the may not. nature of atmospheric energy and matter themThe study of climate can extend to times before © Jones & Bartlett Learning, Jones & Bartlett Learning, weather LLC record. This selves at climaticLLC time scales, rather than the© prothe advent of the instrumental NOT FOR SALE cesses OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION involving energy, matter, and momentum subfield of climatology is termed paleoclimatology exchanges only in the near-surface atmosphere. and involves the extraction of climatic data from Some examples include studies on the causes of indirect sources. This proxy evidence may include lightning, atmospheric optical effects, microphysics human sources such as books, journals, diaries, of cloud formation, and air pollution. Although me-LLC newspapers, and artwork to information about Learning, LLC © Jones & Bartlett Learning, ©gain Jones & Bartlett teorology has traditionally emphasized this type of preinstrumental climates. However, the field NOT FOR SALE priOR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION work to a greater extent than climatology, climatol- marily focuses on biological, geological, geochemiogists have contributed to our understanding of cal, and geophysical proxy sources, such as the these phenomena. Furthermore, the convergence analysis of tree rings, fossils, corals, pollen, ice of meteorology and climatology as disciplines will cores, striations in rocks, and sediment deposited © Jones & Bartlett LLCtopics of re- annually© & Bartlett Learning, LLC likely lead to more Learning, overlap in these onJones the bottoms of lakes (varves). NOTsearch FORinSALE OR DISTRIBUTION NOT FORis SALE OR DISTRIBUTION the future. Bioclimatology a very diverse subfield that Hydroclimatology involves the processes (at includes the interaction of living things with their all spatial scales) of interaction between the atmo- atmospheric environment. Agricultural climatolsphere and near-surface water in solid, liquid, and ogy is the branch of bioclimatology that deals with gaseous forms. This subfield analyzes all compo- the impact of atmospheric properties and processes © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC nents of the global hydrologic cycle. Hydrocli- on living things of economic value. Human biocliNOT FOR SALE matology OR DISTRIBUTION SALE OR DISTRIBUTION interfaces especially closely withNOT the FOR matology is closely related to the life sciences, instudy of other “spheres,” including the litho- cluding biophysics and human physiology. sphere, cryosphere, and biosphere, because water Applied climatology is very different in its oriis present in all of these spheres. entation from the other subfields of climatology. © Jones & Bartlettis Learning, © Jones & Bartlett Another subfield of climatology dynamic cli- LLC While the others seek to uncover causes of various Learning, LLC matology, which primarily concerned with gen- aspects of climate, appliedNOT climatology is primarFOR SALE OR DISTRIBUTION NOTisFOR SALE OR DISTRIBUTION eral atmospheric dynamics—the processes that ily concerned with the effects of climate on other induce atmospheric motion. Most dynamic clima- natural and social phenomena. This subfield may tologists work at the planetary scale. This differs be further subdivided. One area of focus involves from the subfield of synoptic climatology, which attempts to improve the environment. Examples © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC is also concerned with the processes of circulation include using climatic data to create more efficient NOTbut FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION is more regionally focused and usually in- architectural and engineering design, generating volves more practical and specific applications improvements in medicine, and understanding than those described in the more theoretical area the impact of urban landscapes on the natural and of dynamic climatology. According to climatologist human environment. Other examples involve the Brent Yarnal, synoptic possibility of modifying the physical © Jones & Bartlett Learning, LLC climatology “studies the ©reJones & Bartlett Learning, LLC atmosphere between the atmospheric circulation to suitSALE particular needs, such as with the NOT FOR SALE lationships OR DISTRIBUTION NOT FOR ORhuman DISTRIBUTION
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Climatic Records and Statistics
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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC moreFOR accurate method we do not want to practice of cloud seeding, which attempts to exNOT SALE ORbecause DISTRIBUTION NOT FOR SALE OR DISTRIBUTION
tract the maximum amount of precipitation from change the method of calculating the means in clouds in water-scarce regions. the middle of our long-term weather records. In general, each subfield overlaps with others. What would happen if the temperatures began to We cannot fully understand processes and im- rise abruptly at the same point in the period of re© Jones Bartlett Learning, LLC © Jones & Bartlett Learning, LLC pacts relevant to any subfield& without touching on cord that the method of calculating the mean temFOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION aspects important for others and at least one other perature changed? We would NOT not know whether nonclimatology field. For example, an agricultural the “change” represented an actual change in cliclimatologist interested in the effect of wind- mate or was just an artifact of a change in the breaks to reduce evaporation rates in an irrigated method of calculating the mean temperature. field must understand theLearning, near-surfaceLLC wind proBut what about that average temperature? Is it LLC © Jones & Bartlett © Jones & Bartlett Learning, file and turbulent transfer of moisture, along with actually meaningful? Let’s SALE say thatOR yesterday we NOT FOR SALE OR DISTRIBUTION NOT FOR DISTRIBUTION soil and vegetation properties. recorded a high temperature of 32°C (90°F) and a low of 21°C (70°F). Our calculated average daily ■■Climatic Records and Statistics temperature would be about 27°C (80°F). This number would be used to simply describe and © Jones & Bartlett Jones & Bartlett Learning, LLC Because Learning, climatology LLC deals with aggregates of © represent the temperature of the day for our locaNOT FOR SALE ORproperties, DISTRIBUTION FOR SALE OR DISTRIBUTION weather statistics are used to reduce a NOT tion. But the temperature was likely to have been vast array of recorded properties into one or a few 27°C (80°F) only during two very short periods in understandable numbers. For instance, we could the day, once during the mid-day hours when calculate the daily mean temperature—the averclimbing toward the maximum and again as temage temperature for entire& day—for yesterday at © the Jones Bartlett Learning, LLC decreased through the © Jones & Bartlett Learning, LLC peratures late afternoon. a particular location through a number of methods. NOT isFOR SALE NOT FOR SALE OR DISTRIBUTION So the term “average temperature” actually a OR DISTRIBUTION First, we could take all recorded temperatures rather abstract notion. Most averages or climatic throughout the day, add them together, and then “normals” are abstract notions, but the advantage divide by the total number of observations. from a long-term (climatic) perspective is that they A much simpler (but less accurate) method of provide a “mechanism” analyzing Learning, long-term LLC © Jones the & Bartlett Learning, LLC © Jones for & Bartlett calculating daily mean temperature is actuchanges and variability. NOT NOT FOR SALE OR DISTRIBUTION ally theFOR one SALE that is OR used:DISTRIBUTION A simple average is “Extremes” are somewhat different. As we saw calculated from the maximum and minimum earlier in this chapter, climatic extremes repretemperatures recorded for the day. This method is sent the most unusual conditions recorded for a the most common because in the days before computers were used to measure and record tem- location. For example, these may represent the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC perature, special thermometers that operated on highest or lowest temperatures during a particNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the principle of a “bathtub ring” were able to leave ular time period. Extremes are often given on the a mark at the highest and lowest temperature ex- nightly news to give a reference point to the daily perienced since the last time that the thermome- recorded temperatures. We might hear that the ter was reset. Each day, human observers could high temperature for the day was 33°C (92°F), but thatLLC was still 5 C° (8 F°) lower©than the “record © Jones Bartlett temperLearning, Jones & Bartlett Learning, LLC determine the maximum and&minimum high” of 38°C (100°F) recorded on the same in OR DISTRIBUTION ature for the previous hours, but they NOT FORdate SALE NOT 24 FOR SALE OR would DISTRIBUTION not know any of the other temperatures that oc- 1963. As long as our recorded atmospheric propercurred over that time span. For most of the period ties are within the extremes, we know that the atof weather records, we knew only the maximum mosphere is operating within the expected range of conditions. When extremes are exceeded or and minimum daily temperatures. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Of course, the numerical average calculated by nearly exceeded, then the atmosphere may be conNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the maximum–minimum method differs some- sidered to be behaving in an “anomalous” manner. what from the one obtained by taking all hourly The frequency with which extreme events occur is temperatures and dividing by 24. Even though we also important. Specifically, if extreme events ochave automated systems now that can measure cur with increasing frequency, the environmental, epidemiological, and economic imand record temperatures every second, we do not © agricultural, © Jones & Bartlett Learning, LLC Jones & Bartlett Learning, LLC pactsFOR will undoubtedly calculate mean daily temperatures using this NOT NOT FOR SALE OR DISTRIBUTION SALE ORincrease. DISTRIBUTION
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C h a p t e r 1 — Introduction to Climatology
© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC most weather records for the world are confined to Why are climatic records important? During the FOR NOT SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION
1980s and 1990s the rather elementary notion that more-developed countries and tend to be collected climate changes over time was absorbed by the in, or near, population centers. Developing coungeneral public. Before that time many people tries, rural areas, and especially the oceans are thought that climate remained static even though poorly represented in the global weather database, © Jones & considerably Bartlett Learning, Jones Bartlett weather properties varied around theLLC particularly in the earlier©part of the&record (Fig- Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR OR understandDISTRIBUTION normals (averages). WithSALE heightened ure 1.2). Oceans comprise over 70 percent of the ing of weather processes came the realization that planet’s surface, yet relatively few long-term weather climate varies considerably as well. Climatic calcu- records exist for these locations. Most atmospheric lations and the representation of climate for a given recordings over oceans are collected from ships, place over time became exceedingly important and and these recordings are biased by inconsistencies © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC precise. The problems associated with the calcula- in the height of the ship-mounted weather station, NOTtion FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION of various atmospheric properties still existed, the type of station used, the time of observation, however, and the methods of calculating these and the composition of ship materials. Furtherproperties could have far-reaching implications on more, ocean surface temperatures are derived in a such endeavors as environmental planning, hazard variety of ways, from inserting a thermometer into a assessment, and governmental policy. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC bucket of collected ocean water to recording the today’s technology we would assumeNOT that FOR NOT FOR SALE ORWith DISTRIBUTION SALE OR DISTRIBUTION temperature of water passing through the bilge of calculating a simple average temperature for Earth, the ship (with the heat generated by the ship infor instance, would be easy. However, data biases cluded in the recording). Vast tracts of ocean were and methodological differences complicate mat- largely ignored until the recent arrival of satellite ters. Many of these issues have been mathema monitoring and recording© technology, the Learning, LLC © Jones & Bartlett Learning, Jones &because Bartlett tically corrected in recorded data. Given theLLC representation of surface and atmospheric properNOT FOR SALE OR DISTRIBUTION FOR SALE OR corrections,NOT it is generally accepted thatDISTRIBUTION Earth’s avties was greatly limited to shipping lanes. erage annual temperature has risen by about 0.4 C° Even records taken with rather sophisticated (0.7 F°) over the past century. weather stations may be biased and complicated to Another factor that complicates the interpretasome degree by rather simple issues. Foremost tion of& the observedLearning, warming is LLC the increasingly © Jones Bartlett © Jones & Bartlett Learning, LLC among these are station moves. Moving a station urban location of many weather stations as urban NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION even a few meters may ultimately bias long-term sprawl infringes on formerly rural weather starecordings as factors such as differing surface mations. Early in the twentieth century many weather terials and solar exposure occur. Also of note is stations in the United States and elsewhere were time of observation bias, which involved data bias located on the fringe of major cities. This was esbased on the time of day when measurements are pecially true toward cen© Jones & Bartlett Learning, LLCthe middle part of the © Jones & Bartlett Learning, LLC recorded at different stations. Finally, systematic with the construction of major airports far FOR NOT FOR SALE tury OR DISTRIBUTION NOT SALE OR DISTRIBUTION from the urban core. Weather observations could biases and changes in the instrumentation may be recorded at the airport in a relatively rural, un- cause inaccuracies in measurements. The result of disturbed location. As cities grew, however, these these, and a host of other biases, is that considerlocations became swallowed up by urban areas. able data “correction” is required. Both the biases and the correction methods debate&concerning © Jones & Bartlett Learning, ©fuel Jones Bartlett Learning, LLC This instituted considerable bias into long-term LLC the occurrence of actual atmospheric trends. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION records as artificial heat from urban sources, known as the urban heat island, became part of the climatic record. Various properties, such as ■■Summary the abundance of concrete that absorbs solar enintroduces the field of climatology. It ergy effectively, the Learning, absence of vegetation © Jones & Bartlett LLC and wa- This chapter © Jones & Bartlett Learning, LLC surfaces, and the generation of waste heat by describes the scope of climatology, the inherent NOTterFOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION human activities contribute to the heat island. The differences between meteorology and climatology, urban heat island provides an excellent example and the associated notions of weather and climate. of how humans can modify natural climates and Meteorology studies changes in weather, the state can complicate the calculation and analysis of of atmospheric properties for a given location over a © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLCclimatology exrelatively short period of time, while “natural” climatic changes. amines weather properties over time for a location. addition, the long-term recordings themselves NOT FOR SALE ORInDISTRIBUTION NOT FOR SALE OR DISTRIBUTION may be plagued by other problems. Consider that Climatology is a holistic science in that it involves
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Summary
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Figure 1.2 Location of global surface observations at various years. Source: J. E. Hansen and S. Lebedeff, 1987, “Global trends of measured surface air temperature,” Journal of Geophysical Research, 92 D11, 13345–13372.
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understanding the interaction of the atmosphere sphere, hydrosphere, cryosphere, and biosphere. NOT FOR SALE OR DISTRIBUTION NOT SALE OR of DISTRIBUTION with other aspects of the Earth–ocean–atmosphere All are important to FOR the establishment global, system using many different spatial and temporal hemispheric, and regional climates. scales. Each scale partially defines the many Climatic data and calculations also are deinterlocking subfields of climatology, including scribed, with particular emphasis on climatic boundary-layer, physical, hydro-, dynamic, synop- © normals, extremes, andLearning, frequencies.LLC Some causes © Jones & Bartlett Learning, LLC Jones & Bartlett tic, regional, paleo-, bio-, and applied climatology. of spurious climatic data, such as the urban heat NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Interactions occur between the atmosphere, litho- island, are also introduced.
XKey X Terms © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Agricultural climatology Frequencies Paleoclimatology NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Applied climatology Friction Physical climatology Atmosphere Global hydrologic cycle Planetary scale Bioclimatology Human bioclimatology Pressure Biosphere Hydroclimatology Proxy evidence Boundary-layer Hydrosphere Regional & climatology © Jones & Bartlett Learning, LLC © Jones Bartlett Learning, LLC Climate Lithosphere Synoptic climatology NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Climatology Local scale Synoptic scale Cloud seeding Mesoscale Time of observation bias Cryosphere Meteorology Urban heat island Daily mean temperature Microscale Varve © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Dynamic climatology Momentum Weather NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR Evaporation National Weather Service Wind DISTRIBUTION Extremes Normals
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C h a p t e r 1 — Introduction to Climatology
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1. Why is the science of climatology inherently 1. Think of several examples of how advancements holistic? in science and technology may have helped cli2. Briefly describe Earth’s “spheres.” Give exammatology to evolve as a science since 1950. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC ples of how each of the spheres is connected. 2. In today’s age of specialization, is climatology’s NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 3. Compare and contrast the notions of weather interdisciplinary nature an advantage or a disand climate. advantage? 4. Compare and contrast the sciences of meteo3. To what extent are “extreme events” a matter of rology and climatology. perspective? 5. Describe the various spatial and temporal 4. In what sense might the occurrence of non© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC scales of climatology. catastrophic events cause OR catastrophic events NOT FOR SALE OR DISTRIBUTION NOT FOR SALE DISTRIBUTION 6. Discuss the different subdisciplines within to occur? climatology. How are they different from/ similar to one another? go.jblearning.com/Climatology3eCW 7. How are mean temperatures calculated? Dis© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, Connect to this book’s website: LLC go.jblearning.com/ cuss the problems inherent in the calculation NOT FOR SALE ORmethods. DISTRIBUTION NOT FOR SALE OR The DISTRIBUTION Climatology3eCW. site provides chapter outlines, further readings, and other tools to help 8. What is the urban heat island and why is it you study for your class. You can also follow useful relevant to temperature assessment? links for additional information on the topics © Jones & Bartlett Learning, LLCcovered in this chapter. © Jones & Bartlett Learning, LLC
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