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BULLETIN of the American Meteorological Society Assistant Editor Editor Assistant to the Editor THOMAS A. GLEESON WERNER A. BAUM WHEATON M. COWARD, JR. Florida State University Florida State University American Meteorological Society Tallahassee, Florida Tallahassee, Florida Boston 8, Massachusetts VOL. 39 AUGUST, 1958 No. 8 Meteorological Sounding Systems THOMAS O. HAIG, MAJOR, TJSAF, AND VINCENT E. LALLY 1 Geophysics Research Directorate, Air Force Cambridge Research Center (Manuscript received 10 January 1958) ABSTRACT A survey is presented of past and present systems for obtaining direct measurements of atmospheric wind, pressure, temperature, and water vapor. Estimates are included of the types of horizontal- and vertical-sounding systems which will be in field use within the next decade. 1. Introduction There are literally hundreds of techniques for In this paper we shall not attempt to cover all obtaining indirect soundings of the atmosphere, the systems for measuring all meteorological pa- ranging from cloud watching (preferably from a rameters. We shall limit ourselves to the classi- reclining position) to wind determination by cal parameters of pressure, temperature, wind measurement of the scintillation of stars. We field, and water vapor, and specifically exclude shall not even attempt to list all the optical, acous- aircraft sounding systems from the discussion to tical, and electromagnetic phenomena which can keep within a reasonable space limitation. be used to obtain atmospheric data, but will at- tempt only a descriptive presentation of vertical- Meteorological sounding systems may be cate- and horizontal-sounding techniques. gorized in three classes : (1) Vertical-sounding systems where an object is made to ascend over- 2. Vertical-sounding systems head and information is obtained on meteorological The best known vertical sounding that we read conditions essentially in the vertical; (2) hori- of in literature is H. W. Longfellow's friend who zontal-sounding systems where measurements are "shot an arrow into the air, it fell to earth, I knew made of objects moving essentially at constant not where." Can we not surmise that his intent altitudes; and (3) indirect-sounding systems in was to probe the wind field in the upper air and which information is obtained on the pressure, that his difficulties in recovery were due to a temperature, water vapor, and wind fields with- "busted" forecast? The technique is not without out the use of any device or object ascending merit—only recently the U. S. Army announced through or floating in the air. a similar procedure for firing a bullet into the air 1 Now associated with Teledynamics Corp. at an angle so that the spent bullet will fall back Published monthly at Prince and Lemon Streets, Lancaster, Pa. Entered as second class matter September 24, 1945, at the Post Office at Lancaster, Pa., under the Act of August 24, 1912. Acceptance for mailing at special rate of postage provided for in paragraph (d-2), section 34.40, P. L. and R. of 1948, authorized September 24, 1945. Address all business communications, purchase orders and inquiries regarding the Society to the Executive Sec- retary, 3 Joy Street, Boston 8, Mass. 401 Unauthenticated | Downloaded 10/08/21 11:38 PM UTC 402 BULLETIN AMERICAN METEOROLOGICAL SOCIETY on a metal plate. The angle required to hit the balloons carying observers will explore the middle plate provides a low-altitude ballistic wind. regions, and the modern scientific kites will serve The first meteorological soundings were made to carry self-registering instruments to heights ap- by kite in 1749 in Glasgow with the raising of a proaching two miles [2] thermometer on a kite. In 1752 Franklin per- This forecast verified for about twenty years, formed his electrifying demonstration, but little but by the end of World War I manned balloons beyond the edification of small boys was accom- and kites had given way almost completely to the plished with kites until the invention of the box- airplane sounding with the pilot climbing slowly kite by Hargrove in 1893. These kites were able to 10,000 to 15,000 ft with a meteorograph and to carry meteorographs to heights in excess of returning quickly to the field to provide reasonably 10,000 ft, but several miles of trailing wire created synoptic data. This technique was much superior a considerable safety hazard. To quote Napier to the balloon-carried meteorograph, the record Shaw [ 1 ], "Teisserenc de Bort has some thrilling of which might not be recovered for several experiences about the effect of loose steel wire months. upon locomotives, steamboats, and rowing boats in We have seen how the art of vertical soundings the neighborhood of Paris." progressed from manned balloons to unmanned It was not until the invention of the balloon by balloons and kites equipped with meteorographs Montgolfier in 1783 that the meteorologist had a and, finally, to aircraft equipped with meteoro- useful tool for probing the atmosphere at any graphs. In 1917 the first telemetering of sound- great height. This first conquest of space was ing data was performed, using the kite-wire to hailed with even greater fanfare than Sputnik. transmit the meteorograph signals. It was not The stories of the intrepid pioneers who ascended until 1927 that the first balloon-borne device trans- in balloons to make measurements of temperature mitted signals back from the stratosphere. Such and pressure make wonderful reading. Gay-Lus- devices were named "radiosondes" to distinguish sac, the celebrated French chemist, ascended to them from "balloon-sondes" (French for "sound- 23,000 ft as early as 1804 and made accurate tem- ing balloon"). By 1940 radiosondes had almost perature and pressure measurements as well as completely replaced the aircraft meteorographs measurements of the electric field. He obtained for the daily soundings used for weather fore- air samples with evacuated glass bulbs and verified casting. Pilot-balloons tracked by theodolite still the fact that the composition of the air was uni- provided the only means of obtaining wind data form. above the surface—and still do in many parts of In the 1860's James Glaisher made measure- the world. ments of pressure, temperature, and humidity up During World War II excellent gun-laying to 29,000 ft. Using various hygrometers, the dew radar sets were used to track balloon-borne tar- point was measured as being lower than — 45C. gets, and they provided wind data of unsurpassed Even today we are not making much more ac- accuracy. In 1944 the U. S. Army introduced the curate measurements than Glaisher's data of 100 first "rawinsonde" set, the SCR-658, which pro- years ago. vided temperature, pressure, and humidity data The merits of the manned balloon as a platform which were used to compute altitude. The com- for meteorological measurements were forgotten puted altitude is then combined with azimuth and in the 20th century excitement over aeronautics. elevation data provided by manual direction-find- Only in the last few years has there been a swing ing on the radiosonde transmitter. Our presently back to this most excellent means of making both used system within the United States, the AN/ horizontal and vertical measurements. GMD-1, operates in the same fashion as the During the latter half of the nineteenth century, SCR-658 except that tracking is automatic and oxygen masks were used to increase the height of much more accurate. manned balloon ascents, but no systematic ascents were made on a synoptic basis. Free balloons 3. Radiosonde systems in use throughout the carrying self-registering meteorological instru- world ments without observers came into use in the Vertical soundings are made in over 20 coun- 1890's. In Germany Dr. Asmann sent balloons tries using radiosondes. Unfortunately, few to heights of 60,000 ft carrying meteorographs. countries have equipment which will measure By the turn of the century it was the general con- winds together with the other meteorological ele- clusion "that to the free balloon, meteorologists ments. Pibals are still the only means to obtain must trust for data concerning the highest air; wind data except where radar equipment is used Unauthenticated | Downloaded 10/08/21 11:38 PM UTC VOL. 39, No. 8, AUGUST, 1958 403 or where directional receivers are coupled with the probably more accurate than our lithium-chloride radiosonde as in the AN/GMD-1 equipment. element. Rather than list the types of systems used through- Tests are now being conducted jointly by all out the world, it will be simpler to consider sepa- United States weather agencies on a carbon hu- rately the elements of the systems: the sensing midity element which has a better response and devices for temperature, pressure, and humidity; superior low-temperature characteristics than lith- methods of data telemetering; methods of compu- ium chloride. It is expected that this element tation; wind measurements; and the balloons. will be standardized for use within the United Information on equipment of other nations is de- States by 1959. Even the carbon element leaves rived from the tests in May 1956 at Payernne, much to be desired, and we must continue to Switzerland, in which fourteen countries com- search for a better element which can be produced pared their radiosondes [3]. at a low cost. Phosphorus-pentoxide elements Temperature measurements.—Bimetallic ele- provide an absolute measure of water vapor since ments are used in the radiosondes of all countries all the moisture passing through a channel is ab- with the exception of Holland and the United sorbed by the phosphorus pentoxide and then hy- States. These elements suffer from long-time drolized by an electric current. The total flow of constant and radiation effects. Poor shielding of current provides an exact measure of the ab- the element can magnify radiation errors.

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