Rudolf Geiger

German meteorologist

• Born: August 24, 1894
• Birthplace: Erlangen, Germany
• Died: January 22, 1981
• Place of death: Munich, Germany

Geiger is recognized as the founder of a subdiscipline of meteorology that studies the nature of climatic conditions a few meters from the ground.

Early Life

Virtually nothing is known about the early life of Rudolf Geiger (GI-gur). He apparently received the necessary education in geography, soil, and meteorology to come to the attention of August Schmauss (1877-1954) of Munich during World War I. Schmauss provided Geiger with the opportunity to begin an extensive period of practical research in the Bavarian forests to investigate the air layer near the ground. His investigation involved not only forests but also cultivations on the moors and more extensive agricultural regions that surround or break up the forests. Since the subject of his research was in its infancy, Geiger proceeded in a purely practical manner to record and observe conditions of climate both in a small region and close to the ground. Until Geiger proceeded to write his book on micrometeorology in the early 1920’s, there existed no systematic work on this subject. Consequently, Geiger made an effort to record the difficulties and problems associated with this new area of research, and he was also interested in the practical applications of his climatological research.

Life’s Work

Geiger began his study of local climate at the beginning of modern instrumental research on climate. By 1900, many of the major elements of global meteorology were largely in place, along with the systematic study of broad weather patterns and theoretical formulations on the nature of climatic changes. Major advances in physics and mathematics provided meteorologists with the physics of gases and heat and the mathematical models to deal with the change of forces in the atmosphere. The Austrian Meteorological Society regularly began to publish scientific findings in 1866, as did the American Meteorological Journal in 1885. National weather bureaus were organized and each produced its own publications, the most notable being the daily bulletin of the Paris Observatory. The development and refinement of instruments proceeded at an unprecedented pace during the end of the nineteenth century. In addition to standard instruments such as the barometer (air pressure), the anemometer (wind velocity), and the hygrometer (humidity), other technological developments include the nephoscope to measure cloud velocity, the polarimeter for brightness and blueness of the sky, the dust-counter, and certain means of aerial research such as kites and balloons.

The major advances in meteorology were found not only in more accurate instruments and in the proliferation of detailed records but also in the theoretical models of the atmosphere. The most significant of these empirical rules include thermodynamic relations, which describe heat conditions of the atmosphere and hydrodynamic movement of the atmosphere and its gases. These empirical rules led to equations of energy and motion of the climates in various regions of the earth. To complete the grand scheme, meteorologists began to map the patterns of the general circulation of the atmosphere for the entire planet. The United States Signal Service began to publish daily patterns of the dynamics of the atmosphere. In 1893, these results began to be summarized by the United States Weather Bureau. Along with these advances in global climatology, there were also developments on specific atmospheric problems, such as the periodic variations in barometric pressure and the formation of rain. Although these global models of climate were a testament to the success of classical physics, an underlying feeling existed that local climate produces variation and problems that also required extensive research.

In 1927, Geiger wrote Das Klima der bodennahen Luftschicht (The Climate Near the Ground , 1950), which became a classic text and the first survey of microclimatological problems. His special interest lay in the climate in a small region of less than several hundred acres. Special weather conditions such as ground fog over a forest meadow at dawn are obvious, but in many cases local variations in climate would escape notice were it not for detailed instrumental research and mathematical analysis. It is in this boundary layer between the earth and the atmosphere that much of life takes place. Local variations in climate produce varieties in plant and animal life, as well as providing a concern for farmers, foresters, botanists, and practitioners of a number of other fields of science. Geiger generously acknowledged the pioneering work of Gregor Kraus (1841-1915), who published a study entitled Boden und Klima auf Kleinstem Raum (soil and climate in small regions) in 1911. Yet Geiger’s treatment of the concept of local climate is both broader and more incisive. Geiger began his treatment of microclimate with a review of the thermal conditions of climate, including theories of the earth’s radiation and the radiation balance of the earth’s surface. He quickly moved from the global model of temperature to the local level, comparing temperature instabilities recorded over grass near the Munich airport, the Gobi Desert, and an alfalfa garden in Berlin to show how wind eddies create temperature change. Geiger wanted to create an empirical model of temperature and gases of the air near the ground independent of ground conditions. The closest approximation was to describe an air layer over level ground without vegetation. With this model at hand, Geiger was then able to introduce variations to the surface of the ground such as soil, ground cover, ground moisture, water surface, rivers, snow, and ice.

In his book on microclimate, Geiger depended on a host of research and publications to make sense of his subject. There are some twelve hundred citations, and each area of investigation contained its own complexities. For example, variations in the air layer over snow depends on how the snowflakes were deposited, whether it is new snow or old snow, whether rain has fallen on the snow cover, and the elevation of the terrain. To complicate matters even further, the way in which snow melts also influences the immediate environment, not to mention the surfaces on which it is deposited, which create even further variability.

While the thermal nature of air near the ground is the topic of half of his work, Geiger was also concerned with radiation equilibrium. As with the first half of his work, Geiger begins with a description of the physics of the heat budget of the earth, of the atmosphere, and of the ground. He then turns to the heat balance of large climatic regions such as glaciers and riverbanks. Geiger then directs his remarks to a variety of plant covers, the influence of leaves, fruit, blossoms, branches, and pollen. Since Geiger did his work in the Bavarian forest, a large section of the work is devoted to problems of forest meteorology. In an extensive review of the literature and his own contribution on forest climate, Geiger describes radiation in the forest, wind factors, air temperature, humidity, dew, rainfall around a single tree, smoke, snow, shadows cast by trees, and forest clearings.

As the text of Geiger’s work on microclimate progresses, it becomes clear that his concern is with the interaction between the individual living organism and the air that surrounds it. When an aggregate of many similar organisms exist, such as a forest, slope, or valley, then this is the local climate. Yet the nesting sites of swallows, termite nests, rabbit burrows, and sites of an even smaller scale can constitute microclimatic conditions. For human habitats, any room of a house can possess a climate, from the ventilation of a cellar to the dust content of a room. Geiger even considered the climate of the automobile.

The publication of The Climate Near the Ground did not bring Geiger instant recognition or acclaim. He began a field of study that was in its infancy, and it required time and practitioners in the field to gain standing in the scientific community. After the publication of his work, Geiger was made director of the Meteorological Research Institute in the Bavarian Forest Service. In 1930, he presented a short monograph entitled Mikroklima und Pflanzenklima (microclimate and plant climate). Several years later, he was invited to join the Meteorological Institute of the University of Bavaria, where he taught and conducted his research. He died in 1981.

Significance

Geiger introduced the concept of microclimate to describe the interaction between climate and living organisms that could be seen as an early component of modern ecology. Geiger’s emphasis and almost all of his research fall on the side of climate, whereas the focus of ecology is more on the interplay of organic life. With few exceptions, the concept of microclimate did not become a viable field of study until after 1950. Many significant studies have been undertaken and important books published since that time. Geiger’s book both closed a chapter on climatic research in which the observations were limited to locations that generated certain interests and opened a chapter to an era when detailed observations were widely distributed. By the end of World War II, microclimate had developed into an experimental science in which controlled conditions became far more important. Geiger was one of the central figures in fostering the development of this field of study.

Bibliography

Arya, S. Pal. Introduction to Micrometeorology. 2d ed. San Diego, Calif.: Academic Press, 2001. This work points to the later developments in the highly specialized study of climate in a small area. While this field has important applications to biology, chemistry, and medicine, Arya’s presentation is necessarily technical.

Franklin, Thomas B. Climates in Miniature: A Study of Micro-Climate and Environment. London: Faber & Faber, 1955. A series of studies on local climate with the emphasis on the interplay between elements of the environment and their effects on climate.

Geiger, Rudolf, Robert H. Aron, and Paul Todhunter. The Climate Near the Ground. 1950. Rev. and updated ed. Lanham, Md.: Rowman & Littlefield, 2003. The classic text on microclimate. Although the book includes a significant number of technical terms and mathematical formulas, much of it is accessible to advanced general readers.

Lutgens, Frederick K., and Edward J. Tarbuck. The Atmosphere: An Introduction to Meteorology. 10th ed. Upper Saddle River, N.J.: Pearson Prentice Hall, 2007. Microclimatology studies areas ranging from the size of a room to a valley of several hundred acres, but whether the area is large or small, analysis requires meteorological terms such as heat transfer, evaporation, and wind velocity. This work offers a general understanding of meteorology necessary for microclimatology.

Yoshino, Masatoshi M. Climate in a Small Area: An Introduction to Local Meteorology. Tokyo: University of Tokyo Press, 1975. This study is faithful to the spirit of Geiger’s work in that it covers microclimate from a wide perspective and provides many examples. While there are large technical sections, it is also possible to gain a substantial amount of general information about the subject.