Thornthwaite's E 0 as well as his climatic water-budget algorithms (Thornthwaite and Mather, 1955) have found many varied uses, ranging from evaluating local hydroclimatic problems to assessing the geographic variability of evapotranspiration on regional, continental, and even global scales. Thornthwaite's contribution to climatological understanding has endured not only because his E 0 concept is physically grounded, but because relatively reliable estimates of E 0 can easily be made from measurements (or estimates) of monthly air temperature ( T) and day length ( h). Thornthwaite devised a relatively straightforward characterization of atmospheric moisture demand (termed "potential evapotranspiration," or E 0) and a practical means of estimating it (Wilm et al., 1944). Working with colleagues at the Laboratory of Climatology in New Jersey during the 1930s and 1940s, C.W. Surrogates for atmospheric moisture demand, such as pan evaporation and air temperature, were used out of necessity, but they were conceptually flawed and often produced highly biased estimates. What was missing was an easy-to-use, reliable, and yet physically realistic way of estimating the time-integrated atmospheric demand for land surface moisture. Until the 1940s, practical algorithms were unavailable for reliably evaluating the relative wetness or dryness of climates, relationships between precipitation and stream runoff, the amount of irrigation necessary to maximize crop yield, and a number of other hydroclimatic problems. The current popularity of GISs, for example, both reflects and reinforces the influence of spatial analytic theories in the discipline. The variety of perspectives in geography and a recognition of how different world views and experiences influence theoretical work (see Chapter 3) help geographers remain conscious of the influence of theory on technique development (and the reverse). Sidebars 4.1 and 4.2 illustrate the close relationship between advancement of the discipline and technique development. Thus, advancement of the discipline goes hand in hand with the development of new and improved techniques for collecting, analyzing, and interpreting information. As theoretical paradigms change, so do the techniques for empirical research. These techniques reflect the conscious decisions of geographers about the kinds of information that are important to collect the spatial scales at which information should be collected, compiled, analyzed, and displayed data sampling strategies and experimental designs data representation and methods for data analysis. They are developed to address specific problems and, thus, reflect the focus of the discipline at particular times. The techniques that geographers use in their work are not developed in a vacuum. With respect to the display and analysis of data, the chapter examines cartography, visualization, geographic information systems (GISs), and spatial statistics. With respect to observation, the chapter addresses two extremes on the geographic scales of observation: local fieldwork and remote sensing. This chapter provides a brief discussion of contributions made by geographers to the development of techniques for observation, display, and analysis of geographic data.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |