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UCAR logoThis newsletter is a joint project of SIRS Publishing, Inc.
and the University Corporation for Atmospheric Research

MAY 1996 — VOLUME 3, NO. 3

Copyright | Note to Teachers


Table of Contents:

Article

Activity

Resources

Credits & Copyright Information


ARTICLE


How Did Our Weather Measurement Systems Evolve?

When we need to know the weather forecast for the weekend, all we have to do is turn on the radio, the television, make a phone call, or flip to the weather section of a local newspaper to get a detailed record of recent, current, and predicted weather data. We can see real-time radar images, download weather data from the Internet, and can see storm tracks via satellite. The weather enthusiast can spend thousands of dollars on a personal, computerized weather station with state-of-the art weather instruments. But such a glut of weather-related information has only been available in recent years with the innovation of atmospheric measurement systems.

Wind was probably the first atmospheric variable to be measured. The ancient Egyptians and Chinese used wind vanes to measure the direction of the air flow. In the second century B.C. a wind vane was erected in the Tower of the Winds in Athens. The Greeks observed deformation of the trees and waves in fields of grass as a way to measure properties of the wind, and Aristotle wrote about relationships between cloud formation and winds. It was not until 1377 that the first systematic measurements of wind were made by an Oxford scholar, Walter Merle. (It's interesting that more than 2,000 years later, superb observationalists such as Theodore Fujita, long-time professor at the University of Chicago, still use their own eyes as one of their principal observing tools. Fujita's studies of the damage patterns of crops and structures have taught us much about the damage potential of tornadoes and other wind-related weather phenomena.)

The history of temperature measurement begins with the Greeks in about the third century B.C., when the concept of degrees of hot and cold was introduced. The invention of a liquid-in-glass thermometer has been attributed to several individuals in the late 16th century, including Galileo and Santorio (Italy), Cornelius Drebel (the Netherlands), and Robert Fludd (England). Italy's Evangelista Torricelli is credited with invention of the mercury barometer around 1640.

The first humidity measurements are attributed to a German, Cardinal Nicholas Decusa, who used a balance to weigh a piece of wool, the weight of which would change depending upon the moisture in the air. Decusa's first experiments took place around 1450 and his device remained in use for almost 250 years. In 1670, Robert Hooke invented the hair hygrometer, which stretches a single strand of hair between two points and measures the change in its length caused by atmospheric moisture. (Hair lengthens when the humidity rises and shrinks when the humidity falls.)

Next to be developed for humidity measurement was the wet-bulb thermometer, or psychrometer, which relies on the lowering of temperature caused by evaporation of moisture from a wick wrapped around a thermometer's mercury bulb. From the difference between this reading, known as the wet-bulb temperature, and the standard, or dry-bulb, temperature, one can infer the relative humidity. Discovery of the cooling effect of the wet bulb is attributed to Scottish medical professor William Cullen in the 1750s.

stratospheric balloon being inflated prior to launch

A stratospheric balloon is inflated prior to launch. Research balloons are
constructed of polyethylene, a high-grade plastic, with a thickness no greater
than the average dry cleaning bag. The balloons can be up to 240 meters (800 feet)
long and can hold millions of cubic feet of helium. They are filled only partially at
launch so that they will rise to an altitude where internal pressure equals atmospheric
pressure and they can float. At 30 to 45 kilometers (20 to 30 miles) above the earth's
surface, scientists can measure chemical reactions in the ozone, the effect of
human-manufactured pollutants, and cosmic radiation.
(Photo by NCAR)

Aristotle, in his Meteorologica (written around 340 B.C.), was among the first to lay the foundations for what would become modern meteorology. Merle may have been the first person in Europe to keep a regular, day-to-day weather journal, from 1337 to 1344. In the mid-1600s the Grand Duke of Tuscany, Ferdinand II, established the world's first meteorological network, which included the Italian cities of Florence, Pisa, Vallombrosa, Bologna, and Milan, Italy; Paris, France; and Warsaw, Poland. Human observers at each location observed and reported twice daily the temperature, pressure, humidity, state of the sky, and force and direction of the wind. Unfortunately, virtually all of these records have been lost or destroyed, with the exception of some of those in Florence.

Colonists in the New World, including several early U.S. presidents, kept detailed weather records. However, the United States' first meteorological network began with Joseph Henry, secretary of the Smithsonian Institution, who in 1845 established a weather reporting system utilizing 150 volunteers in diverse locations throughout the country. By 1860 the number of observers had increased to 500. President Ulysses Grant formalized the first weather bureau in the U.S., which began operations on November 1, 1870, as the National Weather Service, based in the military through the U.S. Signal Service. On this day, the observers made their reports at the same time of day, or synchronously, at 24 stations across the country. Forecasts were issued for eight regional districts three times a day. By 1878, the number of reporting stations grew to 284.

The importance of weather observations and weather services became obvious to businessmen, farmers, and people from all walks of life, many of whom wanted forecasters in their own home towns. In the 1890s the U.S. Weather Bureau was created as a civilian agency to assume the responsibilities of weather forecasting previously assigned to the military. The Weather Bureau grew and prospered, incorporating kite stations in 1898, manned balloon soundings in 1910, aircraft soundings of the atmosphere in the 1920s, and finally the radiosonde in the 1930s. (A sounding is a measurement of meteorological information such as temperature, pressure, winds, and humidity at various heights in the atmosphere.)

The instrumental packages known as radiosondes rise quietly via weather balloon through the middle atmosphere, or troposphere, and into the upper atmosphere, or stratosphere, reaching heights of 25 kilometers. They perform even in severe weather conditions and turbulence, sending back their data through radio transmission. Simple and inexpensive, radiosondes have been a mainstay of weather observation for more than a half-century.

Such an instrument was critical for implementing a mathematical, computational approach to predicting weather, because frequent reports on the state of the atmosphere in all three dimensions (north-south, east-west, and vertically) were needed. However, until the invention of the radiosonde, sounding the atmosphere required either the use and recovery of balloons carrying recording instruments or the use of aircraft aloft. Surface observations were available, but the inability to systematically observe the three-dimensional structure of the atmosphere frustrated meteorologists for several decades.

Ballooning began with the French Montgolfier brothers (Joseph-Michel and Jacques-Etienne), who invented the hot-air balloon in 1783. Shortly thereafter, Jacques Charles, also a Frenchman, used a hot-air balloon to carry a barometer aloft as an altimeter, or measuring device for altitude. Meteorologists around the world began to use this technique. An American, John Jeffries, produced temperature and pressure measurements up to three kilometers. In the 1800s there was competition to see who could obtain the highest measurements possible. In 1865 James Glaisher, an English mathematician, took measurements in a manned balloon at nearly ten kilometers, subjecting his co-pilot to severe frostbite and almost asphyxiating himself. It became clear that routine high-altitude measurements would have to be made with unmanned balloons.

NACR's cloud-physics Doppler radar dishes

One of the National Center for Atmospheric Research's
cloud-physics Doppler radars points to a developing
thunderstorm in central Florida. More than 100 researchers
from NCAR and elsewhere studied Florida showers and
thunderstorms in 1991. A wide variety of instruments
was deployed, collecting an unusually detailed data set
on the processes that cause summertime showers
and storms to develop in the area.
(Photo by NCAR)

In the 1890s, a German physician flew a balloon-borne instrument to altitudes as high as 20 kilometers. In World War I, balloon flights were replaced by aircraft flights, but these rarely exceeded five kilometers. In 1918 there were attempts in France to transmit high-altitude data from a captive balloon. By 1927 transmitters had been fitted to balloons and were sending airborne signals.

Another important development in atmospheric measurement came with the invention of radar before World War II. Scientists found that radio waves reflected from aircraft could be used to detect positions. Although radar was used primarily for detecting and tracking aircraft, operators learned that weather signals could also be detected and even interfere with their task of finding and warning of aircraft. Young meteorologist cadets during World War II were taught the principles of radar to track precipitation.

In the late 1950s the U.S. Weather Bureau installed its network of radars throughout the country and they have remained the mainstay of the severe weather warning system in this country for more than 30 years.

In the 1960s scientists refined the use of Doppler techniques, which allowed wind as well as precipitation data to be obtained from radar returns. One obstacle to practical use of Doppler radars was the inability of equipment to rapidly process radar signals in real time. However, the innovation of integrated circuits in the 1970s allowed exciting development in the field. The use of Doppler radar has improved short-term forecasts of tornadoes and other hazardous phenomena because it observes circulation patterns within storms.

Doppler radar was next installed into the tail of research aircraft to map three-dimensional winds. Today these systems are invaluable tools for the monitoring and studying of tropical cyclones. This data is combined with ground-based systems for more accurate monitoring and forecasting.

Despite the progress made in the field of radar, the 1960s must be considered the decade of satellite meteorology. In 1961 President John F. Kennedy, in a famous speech before Congress, called upon the United States to place a man on the moon by the end of that decade. Less well-known is the fact that he also asked for $53 million to give us the earliest possible satellite system for worldwide weather observation.

TRACON unit in an airport

Terminal Radar Approach Control (TRACON) units are
installed at airports and help track and direct airplane
traffic. NCAR's Terminal Doppler Weather Radar (TDWR)
program helps detect microbursts, downdrafts of cold,
heavy air that strike the ground and spread
horizontally, producing strong wind shear.
(Photo by NCAR)

In 1954 Harry Wexler, of the U.S. Weather Bureau, proposed the use of satellites in meteorology. The Television and Infrared Observations Satellite (TIROS) project began in about 1958 under the direction of the newly formed National Aeronautics and Space Administration (NASA), and was launched in April 1960. By 1965, the ninth TIROS was launched, and 20 days after its launch it yielded the first mosaic picture of the entire earth.

Satellite technology improved. Geostationary satellites (those that monitor the earth from one location in space rather than orbiting the poles) were first proposed in 1959, and the first successful launch of one was in 1966. By 1978 three Geostationary Operational Environmental Satellites (GOES) were in place. GOES-8 was launched in April 1994. Global Positioning Satellites (GPS) and Low Earth Orbiting (LEO) satellites provide even more data for atmospheric scientists.

Atmospheric measurement is poised on the threshold of a new era with improvements in computer and satellite technology. The number of observations available to weather forecasters in time and space soon will increase by almost 100 times, and these will be available in real time and in digital form, readily used by computer forecast models. Data will be accessible by many groups, such as forecasters, air traffic controllers, pilots, airline dispatch centers, highway management authorities, the agricultural community, the media, and the general public. There is much for atmospheric researchers to do, but it seems clear that weather forecasting will improve as dramatically in the future as it has in the past.

This article was adapted from an article and presentation by Robert Serafin, NCAR director, entitled "The Evolution of Atmospheric Measurement Systems."


ACTIVITY


Mission: Weathernator

Your mission, if you should choose to accept, is to advise secret agent Hail Windswept as she pursues a former television weatherman-turned-master-criminal, Mylar Crupki. Intelligence sources report that the sinister Mylar (who is known to only wear silver suits) is bent on world domination by unleashing a plot to control the world's weather with his atmospheric manipulator he calls the Weathernator.

In a desperate attempt to unravel the mystery of Mylar's fiendish creation before its too late, Hail has asked you, her faithful assistant, to research the new developments and predictions of weather measurement systems using SIRS Researcher®.

Good luck -- the fate of the world may be in your hands!

Here's a few sample citations from SIRS Researcher using the Keyword Search to get you started. These citations were found by using the keywords weather and doppler.

1. Gode Davis. "The Stormy Future of Weather Forecasting," Popular Science, Sept. 1995.

2. Betsy Carpenter. "Stalking the Savage Storm," U.S. News & World Report, July 24, 1989.

3. John Gribben. "Climate and Ozone: The Stratospheric Link," Ecologist, May/June 1991.

4. Jack Williams. "Doppler Effects: New Radar Puts Forecasters a Step Ahead," Weatherwise, Aug./Sept. 1994.

5. Robert Dreyfuss. "Spying on the Environment," E Magazine, Jan./Feb., 1995.

* Note to Librarians/Teachers: Using SIRS Researcher, have students/patrons compile 10 citations relating to Mission: Weathernator. Then have them write a two-page summary on their findings and discuss in groups.

SIRS Researcher provides thousands of carefully selected articles related to social issues; scientific developments and issues within the sciences; and global events and issues of historic, economic and political note. Three search methods guide you to the information you are looking for: Subject Headings Search, Topic Browse and Keyword Search. For more info on SIRS Researcher or any SIRS product call 1-800-232-SIRS.


RESOURCES


Project LEARN modules

One way for students to appreciate the development of atmospheric measurement technology is to have them make observations of their own. The following resources provide lessons or weather data that students can analyze.

Atmospheric Dynamics, a 100-page module that includes background information, hands-on activities, and authentic assessment tools, was developed by Project LEARN, an educational program at The National Center for Atmospheric Research. Send a check to NCAR for $20 to: Project LEARN, NCAR, P.O. Box 3000, Boulder, Colorado, 80307-3000. Two other modules, Ozone in Our Atmosphere, and Cycles of the Earth and Atmosphere: Impact on the Earthis Climate, are also available. You can order all three copies for $50.




Internet Sites

 

Science Now is jointly published by the Walter Orr Roberts Institute at the University Corporation for Atmospheric Research and SIRS Publishing, Inc. (Social Issues Resources Series.) Science Now is published three times during the school year and is distributed to SIRS subscribers. Comments and questions should be directed to Joyce Gellhorn via Internet at jgellhorn@sprynet.com. You can also contact your SIRS representative or write to:

SIRS Publishing, Inc.

P.O. Box 272348
Boca Raton, FL 33427-2348

http://www.sirs.com


Editor:
Caroline Hanson

Scientific Editor:
Robert Serafin, NCAR Director

Contributors:
Bob Henson, UCAR Communications;
Karon Kelly, Information Support Services;
Klay Huddleston, SIRS, Inc.

UCAR is a consortium of over 60 universities in the U.S. and Canada with doctoral programs in atmospheric and related sciences. UCAR manages and operates the National Center for Atmospheric Research under the sponsorship of the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Anyone who undertakes any of the activities described herein shall do so at their own risk; UCAR and SIRS Publishing, Inc. assume no liability, whatsoever, for any injury or harm, which may result therefrom.


© COPYRIGHT 1996 UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH. ALL RIGHTS RESERVED.


Note to Teachers: Permission is hereby granted to copy all or any portion of this publication for distribution to third parties provided such copying and distribution occur for the benefit of research, scientific and educational purposes and for no other purposes including, but not limited to, commercial exploitation purposes. In the event copying occurs or derivative works, as defined under U.S. Copyright Laws, are created, all notices and/or credits recited herein must remain intact on any copies made or derivative works created.

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