Vol. 2 No. 8 SEPTEMBER 1975

NATIONAL CENTER FORATMOSPHERIC RESEARCHNCAR

NEWSLETTEREdward Benton Is New UCAR Special Assistant fo r University Relations

Ned Benton, new UCAR Special Assistant for University Relations, is shown here giving a seminar at NCAR's High A ltitu d e Observatory earlier this year on the topic o f geomagnetism.

Edward (Ned) Benton has accepted appointment as the UCAR Special Assistant for University Relations; he assumed his new responsibilities officially on 1 August. Benton comes to UCAR from the University of Colorado, where he was chairman of the Department of Astro- Geophysics from 1969 to 1974.

His responsibilities w ill be to facilitate and stimulate joint university/NCAR research, to insure effective communication between member universities and NCAR, to serve as ombudsman in problems that may arise between NCAR and member universities, and to provide informed advice to the president of UCAR on policy questions. Benton plans to visit universities to learn of programs under way and potential areas of collaboration. He will also work closely

with the University Relations Committee of UCAR members (see story this page).

Benton obtained his Ph.D. from Harvard University in 1961. From 1963 to 1965 he worked as a scientist at NCAR in the Laboratory of Atmospheric Science. His major research interests are applied mathematics and flu id dynamics, and he has taught in those areas at the University of Colorado for the past ten years. He also served as assistant director of NCAR's Advanced Study Program from 1967 to 1969, and he spent the summers of 1970, 1971, and 1972 at NCAR as a visiting scientist.

Benton welcomes communication with university scientists. He can be reached at NCAR ext. 477 or at the NCAR address.

University Relations Committee MeetsThe University Relations Committee of the UCAR Members' Representatives held its first meeting at NCAR on 16 - 17 June.The committee was appointed in October 1974; its charge is to aid the president of UCAR in improving communications and interactions between the corporation and its members.

Present at the meeting were John Young, University of Wisconsin, who is the committee's chairman; John Geisler, University of Miami; James Holton, Univer­sity of Washington; John McCarthy, University of Oklahoma; Albert Pallmann, Saint Louis University; Ronald Prinn, Massachusetts Institute of Technology;J. J. Stephens, Florida State University; and Richard Thorne, University of California. Thomas Seliga of Ohio State University was not able to attend. Edward Benton, newly appointed Special Assistant for University Relations (see story this page), met with the committee.

Discussion in the meeting centered on ways to increase collaboration between NCAR and the university community and on the relation of responsibilities among the committee, Benton, and the UCAR Members' Representatives.

The committee w ill report on these matters at the annual meeting of the Members' Representatives in October. In the meantime, recommendations developed by the committee will be forwarded to President Bretherton. They w ill include suggestions for expanding the scientific and graduate student visitor programs at NCAR, for potential broadening of the role of NCAR project advisory committees to help promote scientific collaboration anr long-range scientific planning in the university community, and for increasing the scope of scientific news reported in this Newsletter.

Young welcomes questions or comments. They may be addressed to him at the Department of Meteorology, University of Wisconsin, Madison, Wisconsin 53706, or by telephone at (608) 262 - 2828.

NCAR's mailing address for correspon dence with all staff members is:

P.O. Box 3000 Boulder, Colorado 80303

Most NCAR telephone extensions can be reached via FTS by dialing (303) 494-5 plus the extension; however, some extensions can only be reached through the switchboard, (303) 494-5151. From commercial telephones, call the switchboard and ask for the extension. This information is noted w ith the name of the NCAR contact.

Carrier Balloon Passes System TestA full flight test of the Carrier Balloon System (CBS) was successfully carried out on 1 July at the National Scientific Balloon Facility of NCAR in Palestine, Texas.

The CBS will provide essential tropical wind data from the surface to 24 km. It was conceived by NCAR's Global Atmospheric Measurement Program (GAMP), and it is a key component in the Global Atmospheric Research Program (GARP) plan for a First GARP Global Experiment (FGGE) in 1979.

The operational system is to be made up of 200 carrier balloons, each 21 m in diameter, designed to fly at an altitude of 24 km.Each balloon w ill carry 100 dropsondes (weighing about 300 g apiece). Dropsondes w ill be released one by one on command from a network of geostationary satellites. As they descend, they w ill relay signals to the balloon from a network of eight Omega navigation stations spaced around the world. Electronics aboard the balloon will digitize the Omega data and retransmit them via the satellite system to a ground station where the signals w ill be converted to the wind field as observed by the descending dropsondes.

The successful Palestine flight test included launch, successful receipt of drop com­mands from the SMS-II satellite, timed re­lease of a dropsonde when a satellite com­mand was not transmitted, and receipt of data from the sondes that compared well w ith wind data obtained from rawinsonde soundings in the same area. The command and telemetry frequencies used by the system experienced some local or regional radio frequency interference during the test, but very little such interference is expected when the system is operating in equatorial regions during FGGE. Michael Olson, CBS system manager, said, "The test demonstrated the system's readiness for a tropical flight program."

Previous tests included system simulations and a number of test flights from Australia and Kourou, French Guiana, to determine balloon lifetime. The balloons should fly for periods of 60 days or more during the observing periods of FGGE.

Having passed the latest milestone, the balloons w ill be taken to Kourou for further flight tests in September, when it w ill be determined whether the balloons will remain within the equatorial region during an entire FGGE observing period (40 to 60 days).

For more information about the carrier balloon system, contact Vincent Lally, leader of GAMP, at NCAR ext. 77 - 730 (via the NCAR switchboard) or Olson at NCAR ext. 77 - 733, or write to them at the NCAR address.

GATE Data from Commercial A ircra ft Archived fo r ResearchersThe commercial aircraft data collected during the field phase of the GARP Atlantic Tropical Experiment (GATE) have been collected, formatted, and sent to World Data Center A for GATE in Asheville, North Carolina. The data were collected in three separate programs by researchers at NCAR and NASA, at Florida State University, and at Colorado State University.

As archived, the data are filed on three magnetic tapes. "We've shown that the potential yield of commercial aircraft as a global observational tool is hardly being realized,'' comments Paul Julian of NCAR's Empirical Studies Project. Julian and Robert Steinberg of NASA's Lewis Research Center made arrangements for one of the data collection programs. T. N. Krishnamurti of Florida State University was responsible for another program, and the third program was organized by Willis Somervell and Elmar Reiter of Colorado State University.

Julian points out that in the GATE A-scale area (extending from the west coast of South America to the east coast of Africa over 30° of latitude) on a typical day, about ten of the standard air reports (AIREPs) filed by flight crews on commercial aircraft are eventually archived in the National Meteorological Center."B u t it is possible to increase that figure by an order of magnitude over comparable areas of the tropics and subtropics, or even more at higher latitudes," Julian says, "as we've shown by this relatively modest e ffort in GATE."

Each tape contains the aircraft data from one of the three programs, by month, day, and hour. Tape 01 contains data recorded on board wide-body jet airliners that carry an automated airborne integrated data system (AIDS). A consortium of four airlines (Air Afrique, KLM, Swissair, and UTA) and South African Airways provided these data to Julian and Steinberg. They consist of position, altitude, and wind vector data from the Al DS; air temperature data from the airborne Rosemount temperature sensor; and Greenwich time from the airborne GMT clock aboard the jet airliners. The sampling rate varies from airline to airline but is on the order of 1° of latitude or about I00 km.

Tape 02 contains data collected under an arrangement made by Krishnamurti with weather centers at airports in various cities to collect Al REPs from the commercial flights of numerous airlines (both standard and wide-body jetliners). Data were taken on flights to and from points in the GATE A-scale area. Some data in this set were collected by a Brazilian communications firm , TASA.

Tape 03 contains Al REP data collected by Somervell and Reiter from 18 airlines under agreements in which the air crews made / AIREP observations more frequently than at the normal navigation checkpoints and supplemented their data with visual observations and sketches. The supplemen­tary data are not on the tape, but are available from NCAR on microfilm upon request.

Tape 01 contains 19,000 observations, tape 02 contains 35,000 observations, and tape 03 contains 29,500 observations. Because of the multiple sources, there are duplications, but a spot check made of the number of unduplicated observations obtained on various days showed that between 370 and 870 separate observations were obtained on typical days. A little more than a third of these are contributed by the automatically recorded AIDS data.

"While these data were obtained by special arrangements and requests," Julian concludes, "they show that a fairly modest effort to streamline the conventional AIREP system and to collect data from automated systems— perhaps by having data transmitted to the geostationary satellites— could result in a tremendous increase in the quantity of airborne meteorological data available to re­searchers. Commercial aircraft could make a real contribution to the data base in the upcoming First GARP Global Experi­ment." Julian notes that the present data are being examined in various ways to determine their quality. The wind vectors obtained from inertial navigation systems, for example, appear to be quite accurate — within 1.5 m/s.

For more information about the commer­cial aircraft data, call Julian at NCAR ext. 316, or write to him at the NCAR address. To obtain data archived at the World Data Center, write:

World Data Center A NOAA/EDSNational Climatic CenterFederal BuildingAsheville, North Carolina 28801

Correction

In an article on the 1975 - 76 UCAR fellowships in the June issue, Randall Bensch was incorrectly identified as a graduate student at Oklahoma State University. While his B.S. was obtained at Oklahoma State, Bensch is now doing graduate work at the University of Oklahoma.

2

Report on NCAR GCM Is AvailableDevelopment and Use o f the NCAR GCM, a report by the NCAR General Circulation Model (GCM) Steering Committee, is available to the scientific community. It is intended to help GCM users judge the performance of the model, to review the past application of the model to climate and short-range forecasting, and to suggest areas in the model that need improvement.

Over the past few years, the growing demand for use of the GCM by scientists both within and outside NCAR and a general increase in computer use at NCAR have led to the need to set priorities for computer use. To set those priorities and to establish more effective coordination between the GCM users and the Computing Facility, NCAR Director Francis Brether­ton appointed a GCM Steering Committee. Bretherton is chairman, and the committee comprises ten other NCAR scientists and a recorder. The committee's first task has been to review and report on past and present GCM activities.

The report, now available to university researchers, was edited by Akira Kasahara, assistant for science in the Atmospheric Analysis and Prediction Division. It explains the classification and characteris-

On 3 June NCAR's National Scientific Balloon Facility (NSBF) in Palestine,Texas, launched a 1.489 million m3 (52.6 million f t 3) balloon— the largest balloon ever manufactured and flown.

The record balloon carried a 1,431 kg payload of astronomical instruments and special equipment designed by scientists from the Massachusetts Institute of Technology to measure high-energy X-ray emissions from distant galaxies. After spending 14 h at float altitude (44 km), the payload was cut down and retrieved undamaged near the Arizona-California border.

A day later the NSBF conducted its thousandth successful launch, sending NCAR equipment into the stratosphere to measure fluorocarbons, man-made pollutants suspected of damaging the earth's protective ozone layer.

The NSBF, one of the five facilities of NCAR's Atmospheric Technology Division, provides complete balloon flight support to the scientific community, including balloon selection, launching, tracking, payload recovery, and data retrieval; and engineering assistance to scientists preparing their instruments for flight.

tics of each version of the NCAR GCM and gives climatological statistics compiled from computer simulations w ith the various models, comparing them with observed statistics. One- to seven-day forecasts of large-scale atmospheric flow generated from the GCM are given, and applications of the model to medium-range weather prediction experiments, with and without objective analysis techniques, are discussed. The report also discusses model sensitivity for climate simulation and concludes with a summary of areas in the GCM needing improvement for application to numerical weather forecasting and climate studies.

In consultation with the GCM Advisory Panel, which consists of four scientists from UCAR universities, the GCM Steering Committee approves research proposals related to the development and use of the GCM, allocates necessary computer resource units and programming support, and monitors research programs. To obtain a copy of the report or to get more information about the GCM, write to Warren Washington, head of the GCM Operations and Coordination Group, at the NCAR address, or call him at NCAR ext. 674.

Complete information about the facility's capabilities and services is available from:

Alfred Shipley, Manager National Scientific Balloon Facility P.O. Box 1175 Palestine, Texas 75801 Telephone: (214) 729 - 0271

The world-record balloon was constructed o f 0.5 m il polyethylene w ith gore lengths o f 218 m. A t fu ll in fla tion i t measured 120 m in height and 158 m in diameter, and its surface area was 65,000 m 2.

Convective Storms Studied by Oklahoma TeamA combined field effort during May and June was carried out by the University of Oklahoma (OU) and the National Severe Storms Laboratory (NSSL). NCAR research aircraft supported the OU portion of the program.

The Oklahoma investigators were con­cerned with tornadic cyclone circulation, gust-front kinematics, and thermodynam­ics. The team was able to study several tornadic storms that occurred near S till­water, Oklahoma, on 13 June. They were also investigating the continuity of surface-layer convergence maxima through the lower atmosphere.

The team was led by John McCarthy and included Stephen Nelson, Randall Bensch, Lloyd Tidwell, Stephen Kock, Michael Weible, and Gerald Heymsfield. Paul Spyers-Duran (project engineer) and Bill Zinser (project pilot) of the NCAR Research Aviation Facility supported the team in an NCAR Queen A ir equipped with a gust probe and an inertial navigation system. The team is now using the NCAR aircraft measurements and simultaneous dual-doppler data from NSSL, including chaff releases, in studies of heat, moisture, and mass divergence.

Other aspects of the overall program included the deployment by NSSL of a surface observation network and a dual- doppler radar system. NSSL also provided two storm chase vehicles and a mobile meteorological laboratory, which was operated during the study by a group from the University of Wisconsin. The U.S. A ir Force also took part, operating an instru­mented RF - 4C aircraft for high-altitude storm penetration. Nancy and Charles Knight of NCAR collected hailstones during the research period.

Details of the Oklahoma studies may be obtained by contacting John McCarthy fc the Department of Meteorology, Oklahoma University, Norman, Oklahoma 73069.

For information about NCAR's Research Aviation Facility, call Harry Vaughan at NCAR ext. 78 - 50 (via the NCAR switch­board) or write to him at the NCAR address.

NSBF Launches Record Balloon

3

New Hygrometer W ill Be AvailableUniversity researchers will soon be able to use a new hygrometer developed at NCAR that has high resolution, good long-term accuracy, and very fast response.

The instrument is a variable-path Lyman- alpha hygrometer designed by Arden Buck of NCAR's Research Systems Facility. Although it was conceived as an airborne instrument, it can also be used on the ground, in the laboratory, or wherever high-resolution humidity measurements must be made.

The Lyman-alpha hygrometer was developed in response to the need for a single, fast, accurate hygrometer for use in airborne meteorological studies that would be less costly than the techniques generally in use. The most accurate instruments tend to be slow, while the faster ones are insufficiently accurate for many purposes. Thus, meteorologists making airborne measurements have often had to combine two instruments to acquire needed humidity data.

In the Lyman-alpha hygrometer, a lamp emits Lyman-alpha radiation through a sampling volume, where it is partly absorbed by the water vapor present. The attenuated beam then enters a detector whose output provides a measure of humidity. (Lyman-alpha is an emission line of atomic hydrogen at 121.56 nm in the far ultraviolet; the absorption coefficient of water vapor at that wavelength is particularly strong.)

During the development effort. Buck says, two major problems were solved. The first was instability caused by changes in source or detector performance or in transmission characteristics of the windows into the sampling volume. This was overcome by varying the optical path length to obtain two different measures of the humidity. The two measures are mathematically combined to obtain humidity independent of system gain variations. Because d rift is relatively slow, the path length need not be changed frequently.

The second problem was the need to increase the spectral purity of the light source. This was done with modifications to a conventional hydrogen glow lamp to permit the operating pressure to be controlled.

Three path-length modes are available to the operator. In the first, the instrument operates with a fixed path length. In the second mode, the path length is changed periodically to allow an evaluation of system gain. The period between changes can be set by the operator at values between a few seconds and an hour. In the third mode, path length is changed automatically to keep the output voltage from the detector within desired limits.

The instrument has a response time of a few milliseconds. Instrumental resolution is better than 0.2% of the absolute humidity reading (0.02°C dew point). The accuracy is better than 1°C dew point. In laboratory tests, the hygrometer performed well over humidities ranging from 0.02 g/m3 (—53°C dew point) to 30.0 g/m3 (30° C dew point) and temperatures from —60 to 30°C under pressures from 200 to 1,000 mb. A first version of the instrument performed well during the GARP Atlantic Tropical Experi­ment last summer.

While the instrument gives an approximate reading of humidity in real time, computer processing is required to realize the full instrumental capability; thus the hygrom­eter output can be recorded on magnetic

tape. Atmospheric pressure and tempera­ture are required inputs for computer analysis. Software has been written to do the analysis; corrections are made for the slight absorption by oxygen and for imperfect optical collimation. Above the tropopause, errors due to absorption by ozone become significant.

For technical information about the new NCAR hygrometer, call Arden Buck at NCAR ext. 77 - 704 (via the NCAR switchboard) or write to him at the NCAR address. For information on airborne measurement with the instrument, contact Harry Vaughan of the Research Aviation Facility at NCAR ext. 78 - 50 (via the NCAR switchboard) or at the NCAR address.

The NCAR variable-path hygrometer (foreground! and associated electronics. The sampling volume(space between the source and detector windows) is several cubic millimeters.

NHRE Ends Fourth Field Season: September Symposium ScheduledThe National Hail Research Experiment (NHRE) has completed the fourth of seven planned field seasons in northeastern Colorado to test the feasibility of opera­tional hail suppression on the Great Plains.

This year's four-week experiment concen­trated on testing new and improved instrumentation. Particular attention was given to the armored T - 28 storm- penetration aircraft operated by the South Dakota School of Mines and Technology, data-processing facilities for the CP - 2 radar, and the color doppler radar display. Tests were also conducted on surface hail and rainfall instrumentation. The T - 28 flight tests with the Knollenberg precipita­tion particle imaging probe and the axial

scattering cloud particle probe also provided some basic data to test recently derived physical concepts of hail formation.

NHRE is managed by NCAR and primarily funded by NSF's directorate for Research Applied to National Needs. It includes participants from a dozen universities and several government and private organiza­tions. Each group contributes expertise or facilities for basic research on hailstorm growth and hail formation, development of hail suppression techniques, data collection and statistical evaluation, analysis of social and environmental impacts of weather modification, and other related subjects.

4

According to NHRE director David Atlas, primary emphasis for the past year has been on a comprehensive analysis of data from the 1972, 1973, and 1974 field seasons. Most of the vast volume of radar and surface hail and rainfall data accumu­lated in the three prior years has now been reduced. Preliminary analyses of these data do not show statistically significant indications of effect on the hail or rain, but significance was not expected to appear midway in the experiment. Major strides have, however, been made toward the understanding and elucidation of the microphysical and dynamical processes in two of the primary hail-producing storms of the high plains: multicell and supercell storms. In neither of these types of storm is the Soviet "rain accumulation zone" model now believed to be applicable. The recent findings have led to revised concepts of hail suppression, to improved methodol­ogy for seeding, and to a generally sharpened focus for the next three experimental years.

Later this month NHRE will hold a one- week symposium and workshop entitled "Hail and Its Suppression." The symposium is aimed at a comprehensive review of knowledge of the processes of

natural hail growth and those by which hail may be modified by seeding. The goal of the workshop is to crystallize the concepts of hail suppression and to set down the essential features of the design of an improved experiment for the remaining years of the program that w ill optimize the chances of demonstrating the effects of seeding both statistically and physically.

About 75 scientists w ill attend the work­shop, including NHRE staff; university, government, and private agency scientists affiliated with the experiment; other recognized hail research specialists; the NHRE advisory panel; and the NSF Weather Modification Advisory Panel. The program includes about 15 review papers, shorter "response" papers, and a number of brief reports on pertinent research not yet in print. A ll of the papers will be gathered into a symposium monograph.

Richard Sanborn, NHRE deputy director and one of three summer operations directors, lists several major technical accomplishments from the just-completed summer field work:

• Refinements in the operation of the CP - 2 dual-wavelength radar, the Data

Acquisition and Display System (DADS), and the color doppler display system, all developed by NCAR for real-time analysis of storms and control of operational procedures.

• Development of methods for multiple aircraft positioning and tracking with the University of Nevada Desert Research Institute's M33 radar and L-band interroga­tor. Aircraft tracks can now be super­imposed over DADS contoured radar presentations.

• Successful testing of new instruments aboard the armor-plated T - 28 aircraft operated by the South Dakota School of Mines and Technology. Improvements in methods for penetrating storms allowed some scientific data-gathering in the "weak echo" and "embryo curtain" regions of hailstorms to test newly formulated concepts of hailstorm mechanisms.

• Testing of a new, ground-based elec­tronic disdrometer used to measure hail size distributions. Comparison tests were also conducted with improved mechanical rain/hail separators and Styrofoam hailpads to verify the accuracy of each device and improve their reliability.

Summer Colloquium Workshop HeldA one-week workshop, "Understanding the Stratosphere and Mesosphere from Satellite Measurements," was held at NCAR14 - 18 July as part of a two-month summer colloquium conducted jo in tly by NCAR's Advanced Study Program (ASP) and Upper Atmosphere Project (UAP). Participants included about 40 scientists from U.S. and foreign universities, govern­ment agencies, and NCAR, as well as the summer colloquium students. John Gille, leader of UAP, chaired the workshop and helped organize the summer colloquium, which was coordinated by John Clark of Pennsylvania State University. The theme of the Colloquium was "The Stratosphere and Mesosphere: Dynamics, Physics, and Chemistry."

In welcoming the workshop participants, Gille said that questions of the stratosphere have become widely recognized in recent years, not only for their scientific interest, but also for their importance for human well-being, to the point where public policy questions have arisen. This recogni­tion, he said, has made the need to under­stand the stratosphere more urgent. Morris Tepper, program manager at NASA headquarters, echoed this sentiment at the close of the workshop, noting that Congress has asked NASA to take an active role in stratospheric research and that some funding for such research w ill probably be available. The possible human impacts on this layer must be investigated so that decisions can be made about regulating human activities.

Each day of the workshop was devoted to an aspect of the theme. One topic was stratospheric dynamics derived from satellite instruments. Speakers included Roderick Quiroz of the National Meteoro­logical Center (NMC) of the National Oceanic and Atmospheric Administration (NOAA); Clive Rodgers of Oxford Univer­sity, who is on a nine-month visit to UAP and ASP; and Cuddapah Prabhakara of NASA/Goddard Space Flight Center (GSFC).

Recent findings about stratospheric and mesospheric composition were discussed by Prabhakara and Donald Heath of GSFC, who described experiments to determine ozone concentrations. Other speakers on this topic were A. James Miller of NMC, Raymond Deland of Brooklyn Polytechnic Institute, and Raymond Roble of UAP. Roble described the occultation technique he has used for mesospheric and thermo­spheric investigation from satellites.

Capabilities and first results of experiments aboard the recently launched Nimbus 6 satellite were the topic of another session. Gille discussed the limb radiance inversion radiometer (see story this issue), Rodgers detailed Oxford's pressure-modulated radiometer, and William Smith of the NOAA National Environmental Satellite Service (NESS) discussed the high- resolution infrared sounder. Future plans for upper atmosphere satellite sensors also received attention. James Russell III of NASA/Langley Research Center discussed

the Nimbus 6 limb-scanning radiometer. Philip Rosenkranz of the Massachusetts Institute of Technology spoke about temperature sounding of the stratosphere and mesosphere using oxygen microwave lines, and Rodgers talked about the Nimbus 6 limb-scanning pressure- modulated radiometer. Walter Planet of NESS described NOAA studies of occulta­tion techniques, and Andrew Nagy (University of Michigan) and Gille talked about possible experiments for the space shuttle. Finally, Joseph Waters of the Jet Propulsion Laboratory discussed deter­mination of upper atmosphere composition by microwave limb scanning.

In summaries, Robert Dickinson of UAP and the Climate Project at NCAR, Conway Leovy of the University of Washington, and Tepper drew a picture of the state of the science. Dickinson noted that satellite results to date provide a wealth of quanti­tative information for detailed studies of such questions as the mechanisms of wave­like fluctuating disturbances, the various degrees of freedom in trace gas transport, and the nature of tropospheric mechanisms forcing waves in the stratosphere. Leovy discussed the relation between the critical questions and future observing systems. He concluded that existing instruments and those planned for Nimbus G should be adequate to begin answering the immediately foreseeable scientific questions; the larger problem will be data processing, assimilation, and digestion. Beyond Nimbus G, he said, new platforms

5

SUPERPRESSURE BALLOON 3400 gm

MAGNETIC CUT-DOWN

VOLTASE REGULATOR

STABLE OSCILLATOR TRANSMITTER

•ANTENNA

RADIO ALTIMETER

1440 gm TOTAL PAYLOAD

The TWERLE system fu lly deployed (a) and detail o f the balloon flig h t train (b). The radio­a ltim eter (bottom o f b) gives the height o f the balloon to w ith in 15 - 20 m. The data encoder digitizes the sensor data, switching the sensors on in sequence and adding the identification and synchronization codes to the to ta l transmission. With the balloon a t the 150 mb pressure level, the pressure sensor should be accurate to w ith in 0.5 mb. The temperature sensor (not shown) should be accurate to w ith in 0 .5 °C. The tempera­ture o f the pressure sensor is also taken, fo r use in adjusting the pressure data. Above the power supply and the antenna is the transmitter, which broadcasts the identification, altitude, pressure, temperature, and pressure-sensor temperature for 1 s every minute. Transmissions are picked up by RAMS aboard Nimbus 6, which can "hea r" many balloons or buoys a t once. The magnetic cutdown on the balloon flig h t train cuts the flig h t train away from the balloon i f the balloon drifts north o f 2 0 °N magnetic latitude, so a ll data w ill be from the tropics. The balloon itse lf is 3.5 m in diameter and has a metallized cap to prevent the form ation o f frost on the balloon skin a t night.

i N IM B U S 6 IIn ■ >.> wwR A N D O M A C C E S S M E A S U R E M E N T ■ :■ *i

S Y S T E M {R A M S } ^ *

i C O N S T A N T -L E V E L B A L L O O N

* • W IN D

*&> • T E M P E R A T U R E

Iiplplill!• P R E S S U R E

• A L T IT U D E

v:;111" s-

E X P E N D A B L E D R IF T IN G B U O Y S

• P R E S S U R E

• T E M P E R A T U R E

• W IN D

• C U R R E N T

should be thought of in terms of broad scientific objectives rather than single­experiment objectives, and data reduction should be supported until such broad objectives can be fulfilled. Leovy emphasized the need for general circulation models of the atmosphere to diagnose our state of understanding and pointed out that they should be closely coupled with global observations and monitoring of the type that satellites can provide.

Tepper found several major concerns clearly stated in the various sessions. There was concern over the underutilization of existing data and a parallel feeling that too many investigators are concerned only with data from their own experiments. There was concern over a gulf seen to exist between modelers and observers. Finally, Tepper noted, many participants had expressed a feeling that scientific research must be relevant to social problems.

In response to concern about data utiliza­tion, Gille noted that NCAR will assist university investigators in obtaining data from NASA and in studies of those data. University researchers who wish to partici­pate in such studies should write to Gille at the NCAR address or call him at NCAR ext. 351. A complete account of the workshop will be available in colloquium notes to be published early in 1976.

TWERLE Data-Gathering BeginsWith the launch of the Nimbus 6 satellite on 12 June, the data-gathering phase of tht Tropical Wind, Energy Conversion, and Reference Level Experiment (TWERLE) began. TWERLE is a collaborative experi­ment being carried out as part of the preparation for the Global Atmospheric Research Program (GARP) First GARP Global Experiment (FGGE).

In TWERLE, lightweight, low-cost, constant-level balloons carrying arrays of sensors are launched, primarily in the tropics. As the winds carry the balloons along, they transmit information about the pressure and temperature at their float altitude (about 150 mb). If the Nimbus 6 satellite is in range, it picks up each balloon signaling its identification code and data from the sensor array.

"As of 1 August, 127 balloons have been launched," says Paul Julian of NCAR's Empirical Studies Project, a leader of the TWER LE science team. "The satellite's balloon location system is working very well," he reports, "and overall sensor performance is satisfactory. Interesting balloon trajectories have been observed, particularly for balloons launched from Ghana and American Samoa. In a few cases, pairs of balloons launched together have circumnavigated the South Pole several times and are still close together, although theories of turbulent diffusion would not lead us to predict this event."

49 gm

32 gm

342 gm

253 bbi 1»,__^-0ATA ENCODER

222 gm

194 jm

200 gm

sS fe .^ -'SO LA fl POWER SUPPLY

PRESSURE SENSOR

6

Pressure, temperature, and balloon altitude data are collected by a receiver called the Random Access Measurement System (RAMS) aboard Nimbus 6. Data are then transmitted to Nimbus 6 ground stations in Fairbanks, Alaska, and Rosman, North Carolina. Finally, data are sent to NASA's Goddard Space Flight Center (GSFC), which transmits the data to NCAR twice a day over a computer-to-computer link.

The experiment is a jo in t effort among NCAR, the University of Wisconsin, and GSFC. In addition to Julian, the science team includes Verner Suomi of the Univer­sity of Wisconsin, Charles Cote of GSFC, Vincent Lally of NCAR's Global Atm o­spheric Measurement Program (GAMP), and William Kellogg of the NCAR Climate Project.

The experimenters are gradually building a picture of the winds in the atmosphere over the tropics. A reference level — measurements of pressure and temperature at a known altitude— is being determined for calibration of remote sensing by both microwave and infrared satellite instru­ments. Data are also being obtained for studies of the rate at which potential energy is converted to kinetic energy in the upper atmosphere. The low-cost system is receiving a fu ll test for its use in FGGE, when the satellites that take balloon data w ill be in the television infrared observa­tion series (TIROS).

LRIR Operating on NimbusThe Limb Radiance Inversion Radiometer (LRIR) experiment, an NCAR/university/ industry jo in t endeavor funded by NASA, went into space on 12 June aboard the space satellite Nimbus 6 . The LRIR is providing the first global data sets of simultaneous temperature, ozone, and water vapor distributions w ith excellent vertical resolution. These data w ill yield information on stratospheric climatology, sudden warmings, stratospheric transports, diurnal variations, atmospheric tides, and the upper atmosphere radiation budget.

The instrument uses one of the first two- stage cryogenic coolers in space; it is expected to operate for seven months (the lifetime of the cooler), in use approximate­ly 75% of the time. The LRIR differs from most other satellite radiometers because it scans the atmosphere tangentially to the earth's surface (limb scanning), rather than looking down into the atmosphere toward the earth's surface.

There are several distinct advantages to the limb-scanning technique. It has high inherent vertical resolution, since most of the signal originates from a 4 - 5 km layer in the atmosphere above 30 km. There is zero background radiation, since almost all radiation received originates in the layer of the atmosphere being scanned. Finally,

The TWERLE balloons are being launched from four sites; Ascension Island, a British possession in the tropical Atlantic o ff the coast of Africa; Accra, Ghana; Pago Pago, American Samoa; and Christchurch, New Zealand. Balloon launches are done by NCAR crews under the direction of Ernest Lichfield of GAMP. Several members of the New Zealand Meteorological Service are also participating in the launch crews. About 400 balloons will be launched from the sites during the experiment.

In addition to balloons, the RAMS system is also listening for data from expendable drifting buoy? set out by experimenters from several nations. These are providing sea-level pressure reference, according to John Masterson of NCAR, who helped to organize the buoy program. "Nimbus 6/ RAMS is providing ground, air, and ocean 'tru th ' for GARP," Masterson says.

Julian notes that the TWER LE project has been nine years in development. It stems from efforts to improve on such systems as the balloon location and interrogation system on Nimbus 4 and the French EOLE system. The basic design for RAMS, which eliminates the process of interrogating balloons from the satellite and greatly simplifies system operation, came from Charles Laughlin of NASA. The University of Wisconsin team engineered the pressure sensor and oscillator-transmitter portions of the instrument array. The oscillator-

6there is large opacity in the region being scanned, since there is at least 60 times more emitting gas along a grazing horizon­tal path than there is in a vertical path to the earth's surface.

John Gille, leader of NCAR's Upper Atmosphere Project (UAP), is principal investigator for the experiment and coordinator of the activities of the LRIR science team, which comprises Paul Bailey (visiting UAP from Florida State Univer­sity), Frederick House of Drexel Univer­sity, Richard Craig of Florida State University, and John Thomas of the Honeywell Radiation Center.

A data reduction scheme is being used at NCAR to invert the measured radiances. In addition to the vertical distribution of temperature, ozone, and water vapor from 15 to 60 km, the geostrophic component of the wind is obtainable up to a level of 1 mb (~48 km) through integration of the temperature profile in the thermal wind equation.

Experimental data are being archived in three forms and stored on computer tapes, as follows:

• Radiance Archival Tapes (RAT). These are the most basic and complete form of

transmitter was fabricated by Ball Brothers Research Corporation and the pressure sensor was made by Charles Wolfe of Boulder, Colorado. The radioaltimeter was designed by Nadav Levanon of the Univer­sity of Tel Aviv and fabricated in Israel. The temperature sensor, data encoder, magnetic cutdown, and power systems were designed by Lichfield. Texas Instru­ments Incorporated built the RAMS package on the Nimbus 6 . The balloon flight train array was assembled, tested, and packaged by the GAMP group at NCAR.

"The data we're getting should be formatted and available to university researchers in six to eight months," Julian adds. Data are transmitted to the National Meteorological Center in Washington, D.C. They will also go into the GARP Data Systems Test archives and to the World Weather Watch.

For further information on TWER LE, interested researchers should call Julian at NCAR ext. 316 or Masterson at NCAR ext. 696, or write to them at the NCAR address.

Information on all Nimbus 6 experiments is available in the N im bus 6 User's Guide, which can be obtained by writing to the Director, National Space Science, Code 601, Goddard Space Flight Center, Greenbelt, Maryland 20771.

experimental observations, consisting of all useful limb radiance observations for the entire mission.

• Inverted Profile Archival Tapes (IPAT). Profiles are selected from RAT tapes with a spatial frequency of about 400 km along the scan track. These profiles are then inverted to provide parameters of tempera­ture, ozone mixing ratio, and water vapor mixing ratio at pressure points spaced vertically 1.5 km apart. Parameters are interpolated to standard pressure levels and thicknesses.

• Map Archival Tapes (MA T). Data contained on I PAT and available meteoro­logical data in the upper atmosphere at the time of observation are combined to produce objective analyses of parametric fields, interpolated in time and space to be coincident with synoptic weather maps.

These three archival products w ill be stored at the National Space Science Data Center at Goddard Space Flight Center. A second copy of all tapes w ill be available at NCAR. Raw data are being reduced at NCAR, and the reduced data will be available to univer­sity researchers by the fall of 1976. For further information on the LRIR, contact Gille at NCAR ext. 351 or the NCAR address.