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Weather Almanac for April 2006
MODERN WEATHER KITES
The Eddy Bowed Kite and the Hargrave Box Kite
William Abner Eddy had been fascinated by kites as a child. Trained at the University of Chicago as an accountant, Eddy renewed his kite interest as an adult. He had long been fascinated by stories of bowed kites used in the South Pacific that did not require a tail for stability, and though he had never seen one, he tried to build such a kite. Then in 1893, he saw his first Javanese bowed kite at Chicago's World's Fair, and later received further revealing information from a South African who had obtained a bowed kite in Indonesia.
With this information, Eddy was able to construct a bowed kite that responded to his satisfaction. Working with Alexander McAdie at Boston's Blue Hill Observatory in 1894, Eddy used a team of five bowed kites to lift a 2.5-pound (1.13 kg) thermograph 1400 feet (427 m) into the August sky. For several years thereafter, trains of Eddy kites were used at Blue Hill for raising instruments. In November 1895, they lifted a recording anemometer to great altitudes, and a year later, a modified Richard meteorograph that recorded pressure, temperature and humidity went aloft.
Half a world away in Sydney, Australia, Lawrence Hargrave, a pioneer in aeronautics, was studying the properties of airfoils. While working on the lift problem, he built kites to test his theories. He soon understood that cellular or box kites had better lift and stability than the traditional single sided kite. On 15 February 1893, Hargrave debuted the first true cellular kite over Sydney. Then on 12 November 1894, Hargrave flew a train of four linked box kites to lift himself 16 ft (4.9 m) into the air. Among the kite's attributes was its great stability, a requirement for the ideal weather observing platform.
Once word of the box kite came to Blue Hill, even William Eddy saw that it was perfectly suited for weather studies. Eddy wrote Hargrave for permission to use the box kite design in his experiments. In 1895, a modified box kite became the workhorse kite at both Blue Hill and the US Weather Bureau's upper air observation program.
A second technical breakthrough which aided the high-altitude kite soundings was the development of a steam-powered mechanized winch in 1897 by S.P. Fergusson at Blue Hill Observatory. The winch enabled observers to reel in the kites more effortlessly when the observations had been completed.
The Advent of Regular Kite Observations
As the art and science of weather forecasting improved, the need arose for more information on the state of the upper atmosphere (i.e., that above surface and tower measurements). Two methods of upper air measurements began giving these data to meteorologists in the 1890s: balloons and kites. Since radio communications had not yet been established for balloon-based observations, instruments sent aloft on balloon or kite had to be retrieved in order to record the measurements. Thus tethered probes were required.
Actually balloons and kites often worked side by side in these early days. Before launching a kite sounding, the observers frequently released a pilot balloon to judge the prevailing wind conditions over the region. If the wind aloft was strong enough for a kite launch, the size of kite was chosen based on the wind speed. Light winds aloft required a larger kite; strong winds a smaller one.
Beginning around 1893, the US Weather Bureau began using kites to probe the upper-level weather conditions, first as research tools and then in 1898, in a program of simultaneous, regular daily measurements undertaken at a number of sites across the country. Sixteen kite stations were established, most within the nation's mid-section — loosely within the basin of the Mississippi/Missouri/Ohio Rivers. A seventeenth was added later, and two permanent research observatories at Pikes Peak, Colorado and Mt. Weather, Virginia were also established. This network of stations provided weather data for about the next twenty years, but were finally closed as advances in weather balloons made them the new platform of choice. The last kite station at Ellendale, North Dakota closed in July 1933.
Professor Charles F. Marvin, later to become Weather Bureau Chief, adapted the Hargrave kite design for the Weather Bureau program, and it became known as the Hargrave–Marvin Box Kite. He also designed a kite meteorograph, an instrument capable of measuring and recording temperature, pressure, and humidity, in 1896. Pens tracings on paper or on a smoked copper sheet attached to a clock-rotated drum recorded the data during the flight. Marvin also administered the kite network, overseeing every detail from kite design to launch facility specifications:
"a 40-acre square tract of land with open country to the east but with a small town approximately one kilometer to the west. The site had to be level, cleared of trees and stumps, and surrounded by a strong fence to keep out livestock. In addition, the surrounding country needed to be free of forested tracts, lakes, marshes, rivers, streams and electric railways, as well as high-tension power lines."
Americans were not the only nation to use kites for meteorological purposes. As the 19th Century ended, several European countries had or were establishing kite station facilities. The French Trappes Observatory started using kite trains for high-altitude weather observations in 1880. Sweden, Denmark and France established a cooperative kite facility in Viborg, Denmark in August 1902. The first British kite research station was set up in July 1902 in Crinan Bay, off Scotland's west coast by W. H. Dines. In 1903, Germany began regular kite and tethered balloon soundings from the Aeronautical Observatory of Lindenberg where, from 1903 to 1912, 5691 kite flights were made. Other nations to undertake kite-probing of the atmosphere included Russia (at Pavlovsk in 1899), Finland (at Ilmala), India (in 1905), and Egypt (in 1907).
Beginning in 1900, countries represented in the International Commission for Scientific Aeronautics agree to make simultaneous kite and balloon ascents on the first Thursday of every month to sample the atmosphere. At its peak, this activity sent instruments aloft from 44 stations on land and sea across both northern and southern hemispheres.
As the technology advanced, kites flew to higher and higher altitudes. A train of six kites launched from the German Aeronautical Observatory at Lindenberg set an early altitude record for scientific kiting on November 1905 reaching an altitude of 6431 metres (21,096 feet). According to its instruments, the wind speed in the lower atmosphere was 28.9 km/h (18 mph) and temperature 4.8 oC (40.8 oF) while at maximum altitude, the readings were 90 km/h (56 mph) and -25 oC (-13 oF), respectively. Using eight kites, the Observatory claimed to have broken that record on 1 August 1919, reaching 9750 m (31,955 ft), though some today question that claim.
The US Weather Bureau claimed the kite altitude record with the ascent of a kite to 7,044 metres (23,111 ft) on 3 October 1907 from the Mt Weather research facility. A few years later on 5 May 1910, a train of ten kites launched from Mt Weather rose to an altitude of 7269.7 metres (23,835 feet). In order to accomplish this feat, over 13.6 km (8.5 miles) of wire were deployed.
Since then, the records have been broken and are still being chased by kitists around the world.
The Blue Hill Observatory Meteorological Program
The history of American weather kiting at the Blue Hill Meteorological Observatory near Boston, Massachusetts deserves more words than I can allot in this piece. Founded by Professor Abbot Lawrence Rotch in February 1884, the Observatory's original kite–weather research involved studies of atmospheric electrification. Aware of Eddy's work on new kite forms, Rotch invited him to Cambridge to see if his kite could lift a lightweight thermograph. The aforementioned Alexander McAdie directed the research and he was assisted in the early days by William A. Eddy, S.P. Ferguson, and Henry H. Clayton.
On 4 August, 1894, a train of five Eddy kites successfully lifted a modified Richard thermograph above Blue Hill to a height of 427 metres (1400 ft), demonstrating a new method of obtaining high altitude weather data. Sparked by the success, Clayton and Fergusson believed the measurement of pressure, temperature, wind, and possibly humidity could be obtained in future flights. Experiments continued with weather kites for the next decade.
In August 1895, the team flew their first Hargrave-style kite, and by improving both the Eddy and Hargrave kite designs, extended ascents to heights from 305 to 458 metres (1000 to 1500 feet). In 1896, 86 soundings were flown, some lasting for 24 and 36 hours as the kites were alternately reeling in and out. The work of reeling in and paying out the line was hard, and aborted soundings often involved searching for and retrieving breakaway kite packages. The process was improved to some degree when Fergusson invented a steam-powered windlass to launch and reel in the weather kites.
As the technology improved, so did the peak ascents, culminating in a record ascent on 15 October 1897 of 3380 metres (11,080 feet) vertically above Blue Hill, or 3571 metres (11,713 feet) above sea level. Then on 19 July 1900, they reached a new record height of 4623 metres (15,157 feet) above Blue Hill. All high-altitude flights were made with kite trains.
But the work at Blue Hill was about more than reaching ever greater altitude; it was about advancing the knowledge of the atmosphere. Clayton reported in 1899 that kite flights had revealed important features of the atmosphere's vertical structure. For example, he determined that the axis of a cyclone, or low pressure system, sloped westward with height and concluded that surface cyclones and anticyclones were but manifestations of great waves (that we today call Rossby waves) of warm and cold air sweeping across the continent.
The data collected from the flights were used elsewhere as well. Norwegian meteorologist Vilhelm Bjerknes, who developed the now-standard frontal theory, gave credit to the Blue Hill kite soundings for the observational data he needed to test his cyclone development theory.
As a result of the Blue Hill pioneering work in atmospheric soundings, international committees recommended kite experiments be undertaken elsewhere and pushed for regular observation programs. Routine observation flights of temperature, humidity, and wind were run out of Blue Hill from 1894 to 1909. International cooperation on weather observations was effectively halted by the outbreak of war in 1914. With it, the exchange of sounding data ended, and in 1914 so too did the kite sounding program at Blue Hill.
The Present Use of Kites in Meteorology
Though regular routine weather observations with kites ended nearly a century ago, the kite still plays a role in modern meteorological research. And often in that role it is teamed with its replacement for upper air soundings, the balloon. Tethered balloons or kite-balloons aka kitoons, are often used ro measure weather conditions above the surface where towers or free balloons are not feasible.
Return to Part 1: Kites Live In Weather
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