550 BULLETIN AMERICAN METEOROLOGICAL SOCIETY

New Developments in Observations and Instrumentation in the Weather Bureau

VAUGHN D. ROCKNEY

United States Weather Bureau, Washington, D. C.

(Manuscript received 28 February 1959)

ABSTRACT A review is made of programs for the development, procurement, and installation of new observing instruments by the Weather Bureau. Some new observational techniques which will be used with the new instruments are also described. The article deals with four main fields of observations—surface, upper-air, radar, and marine.

1. Introduction expect to see the high-intensity runway lights. "Approach-light contact height" is defined as the The Weather Bureau, at the present time, is height above the ground at which a pilot making engaged in bringing about improvements in obser- a final approach along the glide path can expect to vations in four major fields—surface, radar, ma- establish visual contact with the approach lights. rine, and upper-air. Many new and improved To obtain runwray visual range, the transmissom- instruments which have been developed by our In- eter indicator which normally reads runway visi- strumental Engineering Division are being placed bility is recalibrated and the values of "RVR" are in use. This article will describe recent develop- read directly. To obtain the approach-light con- ments in the observational field and will give some- tact height, indications of the rotating-beam ceil- thing of the outlook for the future in this field. ometer, transmissometer, and an illuminometer as well as the brightness setting of the approach lights 2. Surface instruments and observations are all considered. Values of "ALCH" are com- One of the most important developments in sur- puted using empirically-derived charts. Comput- face observations is the advent of new end-of-run- ers to replace all manual operations in the deriva- way instruments. These permit improved obser- tion of these parameters are now being developed. vational techniques that are aimed at increasing Observations taken at Newark have been ac- the "acceptance rates" of airports under bad cepted wholeheartedly by both the aviation indus- weather conditions while, at the same time, giving try and military and civil aviation agencies [1 ; the pilot an accurate picture of what the weather 2; 3 J. Runway visual-range programs have re- will be when he flares out for landing. A total of cently been inaugurated at the Idlewild, Boston, 95 rotating-beam and 95 transmissom- Washington National, and Los Angeles airports. eters for these end-of-runway installations are on Expansion of this system to other areas is depend- order and are now being delivered and installed. ent upon the availability of proper runway lighting In general, the ceilometers (fig. 1) will be in- facilities, other landing aids, and proper wreather stalled at the middle marker sites and the trans- instrumentation at the individual airports. missometers (fig. 2) near the touchdown points One hundred thirty-four hygrothermoineters of the instrument runways. At the airport at are on order (figs. 3 and 4). In these instruments, Newark, New Jersey, the Weather Bureau over the temperature is sensed by an electrical resist- the period of the past several years, in cooperation ance (thermohm) and the dewpoint with the U. S. Air Force and Airways Moderni- by a Foxboro Dewcell, using a lithium-chloride- zation Board, has developed techniques for meas- coated heater element. The temperature of the uring the "runway visual range" and the "ap- heater element is a function of dewpoint. A proach-light contact height,'" both of which are thermohm is used to sense the heater element tem- new parameters aimed at objectively describing perature. The hygrothermometers will enable us the significant weather to the landing pilot. to correct deficiencies in exposures of thermom- "Runway visual range" is defined as the dis- eters by remoting the instruments to sites where tance along the runway that a landing pilot can the temperature and moisture are truly represent-

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FIG. 1. Control and indicator panel of rotating-beam and schematic diagram of operation. ative of the surrounding environment. At the ment from present locations atop terminal build- same time, the observer's workload will be de- ings to completely representative sites in the creased. Temperature extremes at the representa- middle of the airfields. In all cases where we are tive sites will also be indicated. Last year at about relocating the wind equipment, we are providing 15 airport locations, we removed the wind equip- extra cables so that the hygrothermometers can

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FIG. 2. Schematic diagram of transmissometer operation. be installed on the middle of the airfield also. A data from beach areas for operational forecasting large number of additional wind-equipment reloca- purposes. tions is planned. Considerable effort is being spent on the devel- Additional surface wind data are being obtained opment of automatic devices to take and transmit from the Gulf and Atlantic coasts through the in- surface weather observations. A new automatic stallation of relatively low-cost and weather-observing system is in production, and wind vanes to provide additional representative 24 sets have been obtained. Fifteen of these sets are in operation, and the balance will be installed in the next year. The principal use at the present is at remote locations. However, within a few months, one of these systems will be installed on an operational basis at Washington National Air- port to take as much as possible of the aviation observation by automatic means and to transmit it automatically. The equipment provides for in- serting the "visual elements" (ceiling, sky cover, prevailing visibility, weather, and obstructions to vision) into their normal place in the aviation report by punching them into an array of push buttons. Next, the automatically-observed param- FIG. 3. Indicator panel for hygrothermometer. Note pointers for max-min readings on the temperature eters are transmitted and, finally, there may be dial. transmitted a manually-prepared tape on which

Unauthenticated | Downloaded 10/04/21 08:35 AM UTC VOL. 40, No. 11, NOVEMBER, 1959 551 are punched "remarks," notices to airmen, additive early in 1959 (fig. 5). The WSR-57 is unique data, and the like. among weather radars in many respects, especially Parameters that can be sensed and transmitted in that it will incorporate two receivers, one hav- automatically at the present time include runway ing linear, and the other logarithmic-gain charac- visual range or runway visibility sensed by the teristics. The log receiver is intended to improve transmissometer; temperature and dew point, by the usefulness of the radar for hydrologic pur- the new hygrothermometer; wind speed, direction, poses. The radars will also be equipped with a and altimeter setting, by conventional sensors; the unique photo-repeater scope and camera system occurrence of thunderstorms, by a low-sensitivity for operational and research photography. Plans radio receiver; and cumulative amounts of precipi- have been developed for expansion of the radar tation, by a heated tipping-bucket rain gage. Tech- network to provide complete coverage of the niques have also been perfected for the trans- continental United States and some United States mission of these data at normal teletypewriter possessions overseas. Ultimate plans include the speeds. Development contracts have been let for automatic collection of radar-scope displays at a sky-cover sensor (which will likely involve infra- central locations and the incorporation of a num- red techniques), a sea-level-pressure computer ber of the displays into composite maps of the involving an electronically-read mercurial barom- rainfall distribution over large areas. These will eter, and an "interpreter" for the rotating-beam be very useful to hydrologists and the meteorol- ceilometer to present cloud-height data in a form ogists who are concerned with forecasting 8 to 48 suitable for aircraft operations. Plans provide hr in the future. for a digital display of the current observation at A radar rainfall beacon has been developed and various places in the weather station, in the con- is now under test. This beacon, which can be trol tower, or in offices of the airport, airlines, or battery-powered, is connected to a recording rain- other agencies. Provision for the automatic punching of climatological cards or tape will also be made. The solar radiation network now comprises 100 stations (of which 45 are cooperators outside the Weather Bureau), all of which take observa- tions of the total sun and sky (hemispherical) radiation. Eight of these stations report normal incidence radiation and others take special meas- urements. Four stations are taking observations of total ozone, by the use of the Dobson spectro- photometer. Numerous programs of dust and precipitation sampling are being conducted for offices concerned with the distribution of radioac- tive debris, the travel of wheat-stem rust spores, etc.

3. Radar instruments and observations In the field of radar observations, our network now comprises 70 stations, of which 66 have the WSR-1 (Weather Search Radar-Model 1) or WSR-3 type (the WSR-3 is different from the WSR-1 in that it has the range-height indication feature) and three have the SP-1 type. All of these radars operate in the 10-cm band. The WSR-1 and WSR-3 have a peak-power output of 50 kw, and the SP-1M has an output of 1000 kw. We also operate a 3-cm Decca Model 41 radar at Akron, Ohio. Thirty-one new radars, designated WSR-57 and operating in the 10-cm band with a peak-power output of 500 kw are also on order, with quantity delivery expected to begin FIG. 4. Exposure screen for hygrothermometer sensor.

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FIG. 5. Antenna assembly for WSR-57 radar. gage. It enables a master radar station to read A 30-watt CW radar, operating on the Doppler the amount of precipitation that has occurred at principle, has been developed as an experimental the beacon site. This device promises to be very device to try to detect tornadoes. The supposition useful for making hydrologic observations, espe- is that debris or water droplets having unusually cially in the mountainous terrain where observers high-speed motion will be present in the parent may be difficult to obtain or where communica- cloud or in the funnel itself, and that the Doppler tions are nonexistent. Several of these gages radar will "hear" these high-speed motions. On located in strategic places in a watershed can be 2 April 1958, at Wichita Falls, Texas, a tornado read at the master station. A wide variety of passed within five mi of this radar, and on 10 other information could also be telemetered by the June 1958 another tornado passed within 25 mi radar-beacon technique. of the radar while it was located at Wichita,

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Kansas. Wind speeds in excess of 200 mph 5. Upper-air instruments and observations were measured in these tornadoes. In the field of upper-air observations, the 4. Marine instruments and observations Weather Bureau, about two years ago, assumed the responsibility for the operation of virtually In the field of marine observations, 700 new all the upper-air stations in the United States, in- precision aneroid and 1000 battery- cluding Alaska, that had been operated by military powered aspirated psychrometers have been fur- agencies. The AN/GMD-1A radio direction- nished to cooperating merchant ships. Six hun- finding equipment with which those stations were dred microbarographs have been issued to these equipped was continued in use. Equipment of the vessels. In an effort to obtain more upper-air GMD-1 series has replaced the older SCR-658 at data over the oceans, cooperative programs with a total of 53 of the 132 upper-air stations now op- the U. S. Navy have been established on five erated by the Bureau. For those not familiar military transport vessels in the Pacific and two with the characteristics of various equipments in in the Atlantic. Aboard these vessels, Weather this field, the SCR-658 (403-mc frequency) is Bureau employees take four synoptic observations the original electronic radio-direction-finding and two observations daily using high- equipment used for taking rawins, and the GMD-1 quality instruments. So far, it has been impossible series (1680-mc frequency) is the newer type. to obtain rawins from these ships, but work is Both were developed by the U. S. Army Signal continuing on the problem of instrumentation for Corps. The new equipment has vastly greater this purpose. We also operate an additional capability than the SCR-658 in terms of precision upper-air program aboard a U. S. Coast Guard of upper-wind measurement and the ability to vessel in the Gulf of Mexico and Caribbean area. measure high-speed winds to high altitudes. In Extension of the moving-ship program to 75 addi- addition, it tracks the radiosonde automatically tional vessels plying the waters of the world is planned when funds become available. For use ... on the ships, a miniaturized, easily transportable Delivery is expected in 1959 of 42 new radio- receiving station has been developed which in- theodolites. These will be generally similar to cludes receiver, frequency unit, and recorder, all the GMD-1 series but will have a larger antenna contained in two small chests that weigh about and improved circuitry to provide greater accu- 40 pounds each (fig. 6). In a further experiment racy and more efficient operation (fig. 7). Plans toward miniaturization, one of these sets is being are now being laid for the modification of all transistorized and packaged in a single case. Min- radio-direction-finding equipment, both the new iaturized , weighing only 565 g with type and the GMD-1 series, to include the capa- battery, have also been developed and are in use. bility of measuring the slant range to the radio- sonde in flight, using the transponder principle. In this system, there is mounted on the existing radiotheodolite a 403-mc transmitter with its an- tenna directed similarly to that of the radiotheodo- lite. The radiosonde is modified to include a

FIG. 6. Miniaturized radiosonde reception equipment. Recorder at left, receiver and frequency meter at right.

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located some 8 mi from downtown Washington, D. C., the operational 4-daily rawinsonde program for the Washington area and many instrumental test programs are conducted on the five acres of ground occupied by the Center. Field tests are conducted there, and comparisons are made of various kinds of instruments for measuring me- teorological parameters such as temperature, hu- midity, solar radiation, ceiling, visibility, and new radar devices. Experimental projects also involve new instruments and techniques of measurements for hydrology and agricultural . Of particular interest currently are tests of two types of sonic -. One operates on a short pathlength and is especially suitable for micrometeorological observations; the other operates on a long pathlength and is suitable for airfield measurements.

FIG. 7. Antenna assembly of new 1680-mc radiotheodo- 7. Conclusion lite designated WBRT-1. Recent developments in electronics and auto- mation promise observational techniques that are 403-mc receiver in addition to a 1680-mc trans- more objective, more timely, and more accurate mitter. In operation, a modulated signal is trans- than those currently available. Meteorologists can mitted on 403 mc from the radiotheodolite to the look forward to observational quality that is, or radiosonde, and the signal (with temperature, can be made to be, responsive to virtually every humidity, and pressure data superimposed) is new requirement of the science. then retransmitted on 1680 mc to the radiotheodo- lite. Knowing the speed of radio waves and ob- REFERENCES serving the phase shift of the modulated signal, 1. Sperry Gyroscope Company, 1954: A flight investiga- one is able to compute the slant range to the radio- tion of the performance of low ceiling/visibility meteorological equipment. Sperry Rep. No. 5245— sonde by the ground equipment. Errors in wind 4059, prepared for Air Navigation Development calculations that result from small errors in the Board (Summary Rep.: Sperry Rep. No. 5245- elevation angle when that angle is small are mini- 4060, 1954). 2. Sperry Gyroscope Company, 1957: An operational mized inasmuch as the trigonometric computation evaluation of an approach zone slant visibility of the winds aloft no longer involves the use of measuring system. Sperry Rep. 3245-4079, pre- the tangent function. The transponder modifica- pared for Air Force Cambridge Research Center (Summary Rep. Sperry No. 3245-4080, 1957). tion will also facilitate our ultimate plans for auto- 3. Haig, Thomas O., and W. C. Morton, 1958: An opera- matic computation of rawinsonde data. tional system to measure, compute, and present approach visibility information. AF Surv. Geo- phys., No. 102; ASTIA Doc. No. AD 152584. 6. Observational test and development center 4. Ference, M., Jr., 1951: Instruments and techniques At the Weather Bureau's Observational Test for meteorological measurements. Compendium MeteorAmerican Meteorological Society, 1207- and Development Center at Silver Hill, Maryland, 1213.

graduate fellows will vary from $1800 to $2200 in ac- ANNOUNCEMENTS cordance with the academic status of the recipients. Tuition, laboratory fees, dependency and travel allowances will also be provided. Application materials may be obtained on request to Graduate Awards the Fellowship Office, National Academy of Sciences- National Research Council, 2101 Constitution Avenue, Applications for the National Science Foundation grad- N. W., Washington 25, D. C. uate fellowship awards for advanced study in the sciences are being accepted through 1 January 1960. Stipends for (Continued on page 596)

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