Rodney S. Henderson 1 USAF Aerial weather Reconnaissance Byran, Tex. 77801 Using me Lockheed wc-130 Aircraft

Abstract 1970s. At least five major organizational changes have occurred, ranging from the deactivation of a squadron Air Force weather reconnaissance forces fly a wide variety of missions for many different military and civilian agencies. of WB-57s to the establishment of an Air Force Reserve The workhorse of the weather reconnaissance fleet is the weather reconnaissance organization. Currently, opera- Lockheed WC-f30 "Hercules," operated by three weather tional aerial weather reconnaissance is performed by Mil- reconnaissance squadrons. A discussion of the organization itary Airlift Command (MAC) and U.S. Air Force Re- of Air Force weather reconnaissance forces is presented along with brief remarks concerning the aircraft and its meteorolog- serve (AFRES) units. ical instrumentation. The tropical cyclone reconnaissance, MAC weather reconnaissance forces are assigned to tactical support, and East Coast winter storms missions are the Aerospace Rescue and Recovery Service (ARRS) and discussed as being representative of typical weather recon- to the Air Weather Service (AWS). AFRES weather re- naissance operations. The effectiveness of Air Force weather connaissance forces are assigned to the Fourth Air Force reconnaissance is considered along with remarks concerning the accuracy of data acquired on typical operations. Efforts during peacetime and to MAC in time of war. Figure 1 to develop improved meteorological systems over nearly a illustrates Air Force weather reconnaissance organiza- decade have resulted in concept development for an Im- tion. proved Weather Reconnaissance System (IWRS), whose gen- Control of ARRS weather reconnaissance squadrons eral characteristics are briefly considered. is exercised by the 41st Rescue and Weather Recon- naissance Wing (41st RWRW) at McClellan AFB, Calif. 1. Introduction The 41st RWRW has two basic missions: combat rescue On 27 July 1943, Maj. Joe Duckworth flew a propeller- and aerial weather reconnaissance. Three squadrons pro- driven, single-engine North American AT-6 "Texan" vide the operational weather reconnaissance capability trainer into the center of a tropical cyclone and created within the 41st RWRW: the 54th WRS at Andersen a legacy shared by weather reconnaissance crews for three AFB, Guam, the 53rd WRS at Keesler AFB, Miss., and the and a half decades. Major Duckworth flew into the eye 55th WRS at McClellan AFB, Calif. The 54th WRS and of the storm twice that day, once with a navigator 53rd WRS operate Lockheed WC-130 aircraft on a and again with a weather officer. Duckworth's legacy has variety of missions. The 55th WRS operates Boeing developed into one of the U.S. Air Force's largest, con- WC-135B aircraft primarily on atmospheric sampling tinuing, humanitarian efforts—the tropical cyclone re- missions for various government agencies. connaissance mission of Air Force weather reconnais- In 1976, AFRES converted a tactical airlift group sance units. into a weather reconnaissance group at Keesler AFB and Today, three Air Force squadrons fly Lockheed WC- began to establish a weather reconnaissance organization. 130 aircraft on a wide variety of missions ranging from Reserve weather reconnaissance organization differs tropical cyclone reconnaissance to weather modification from the structure under ARRS because of the operations. Each squadron is supported by trained heavier training requirements levied on Reserve units weather personnel, in a special detachment or within the and the necessity of maintaining Reserve organizations squadron, who fly aboard the aircraft and provide the to provide services normally available from host air base meteorological expertise necessary to accomplish weather organizations or higher headquarters. reconnaissance operations in any part of the world. It Reserve weather reconnaissance organization under is hoped that this paper will serve as a brief but effective the Fourth Air Force begins with the 403rd RWRW at introduction to the small but very active world of Air Selfridge ANG Base, Mich. The 403rd is composed of Force weather reconnaissance. four rescue and recovery squadrons and one weather reconnaissance group, the 920th WRG, based at Keesler 2. Organizational structure AFB. The 920th WRG provides command and staff supervision to several subordinate units including the Air Force weather reconnaissance organizational struc- Reserve's only weather reconnaissance squadron, the ture has undergone some marked changes since the early 815th WRS, which is also located at Keesler AFB and operates WC-130H aircraft. i Captain, U.S. Air Force; presently assigned to Texas A&rM In April 1977, weather personnel were removed from University in a graduate program. the ARRS squadrons and placed in separate AWS de- 0003-0007/78/1136-4143$05.00 tachments at Keesler AFB and at Andersen AFB and in © 1978 American Meteorological Society an AWS operating location at McClellan AFB. The de-

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FIG. 1. U.S. Air Force operational weather reconnaissance organization under the Military Airlift Command and U.S. Air Force Reserve.

tachments are subordinate to AWS Headquarters, pro- monoplane with retractable tricycle landing gear. Allison vide weather personnel for operational missions, and T-56 turboprop engines drive four-bladed, full-feather- provide staff meteorological support to the active duty ing, reversible pitch propellers at almost 1000 rpm. The squadrons. The operating location was established at fuselage is divided into a cargo compartment and a flight McClellan AFB to provide support to the 41st RWRW deck by a bulkhead at the forward end of the cargo and, to a lesser degree, to provide weather personnel compartment. Flight deck crew positions are provided for 55th WRS operations. AWS also operates a network for a pilot (Aircraft Commander), copilot, flight engi- of weather monitors at selected worldwide detachments neer, navigator, and an Weather that copy and relay weather reconnaissance observations. Officer (ARWO). A crew position for the System Operator (DSO) is located at a console in the cargo compartment near the right paratroop door. 3. Aircraft and instrumentation The WC-130s carry meteorological sensor systems for The guiding principle in operational Air Force weather measuring atmospheric parameters at the aircraft flight reconnaissance is the concept of placing a manned me- level and for taking soundings beneath the aircraft. teorological sensor platform in the atmosphere at the Systems used to collect data at flight level are referred time, place, and altitude requested by a "customer," to as the horizontal meteorological system (horizontal collecting data according to the customer's requirements, metsystem), and systems used to produce atmospheric and relaying those data to the customer in a usable, soundings are called the vertical meteorological system coded form. For over a decade, the workhorse meteoro- (vertical metsystem). Components of the horizontal met- logical sensor platform for Air Force weather reconnais- system are listed in Table 1 along with other aircraft sance units has been the Lockheed WC-130 "Hercules" systems used to produce data for meteorological ob- (Fig. 2). The WC-130E and WC-130H versions of the servations. Table 2 lists components of the vertical met- aircraft currently are in use, with a single WC-130B system. having been modified to carry an advanced metsystem— Additional equipment is available or can be installed the Airborne Weather Reconnaissance System. for specialized missions. Atmospheric Research Equip- The WC-130 is an all-metal, four-engine, high-wing ment (ARE) is installed on WC-130E aircraft and is used

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FIG. 2. The workhorse meteorological sensor platform for Air Force weather reconnaissance— the Lockheed WC-130 "Hercules." Photo is of the WC-130H used by the 920th Weather Re- connaissance Group at Keesler AFB, Miss.

TABLE 1. Components of the WC-130 horizontal metsystem and other systems used in producing data for horizontal meteorological observations.*

Parameter Sensed Subsystem Remarks

Atmospheric pressure 1301A Pressure Transducer System In the process of being replaced by the Garrett Airesearch Digital Pressure Encoderf Pressure altitude AIMS counterdrum-pointer aneroid altimeter Provides secondary pressure altitude dataf (pilot's instrument panel) Atmospheric temperature Rosemount AN/AMQ-28 Total Temperature Requires true airspeed information obtainable from System an indicator on the navigator's panel for normal usej C-3 Outside Air Temperature System Provides a limited backup capability (navigator's panel) Atmospheric dew point Cambridge Systems AN/AMQ-34 Aircraft System Absolute altitude AN/APN-42A Radar Altimeter SCR-718 or AN/APN-133 Radio Altimeter Secondary absolute altimeters on WC-130E aircraft only; AN/APN-133 altimeters are currently programed for installation on WC-130H aircraft by 1979. AN/APN-150 Radar Altimeter (pilot's Currently used as the secondary absolute altimeter instrument panel) on WC-130H aircraft at low altitude only Sea surface temperature Barnes Engineering Co. PRT-5 Precision Radiation Flight-level wind Doppler Navigation System, AN/APN-147/AN/ ASN-35 (navigator's panel) Hewlett-Packard HP-97 programable calculator Data-recording system WC-130E only; system is not currently used AN/APN-59 aircraft radar

* Except where otherwise noted, all instrument indicators are located at the flight deck ARWO position. t Data from these subsystems are used along with absolute altitude data in computing heights of standard pressure surfaces or in extrapolating sea-level pressures. I The sensed parameter must be computed from subsystem indications and is not directly displayed on an indicator.

Unauthenticated | Downloaded 09/25/21 08:15 AM UTC Bulletin American Meteorological Society 1139 for atmospheric sampling operations. The ARE consists 11) clouds including number of layers, amount in each basically of particulate sampling systems, a gaseous layer, type, and altitudes of the base and top of whole-air sampling system with associated plumbing and each layer; compressor systems, and an ARE console with system 12) surface wind direction and speed; controls and monitoring equipment. Special equipment 13) icing; can also be installed for weather modification activities, 14) significant weather observed off course; such as supercooled fog dispersal and cloud seeding. 15) significant weather changes observed along track; 4. Data acquisition and dissemination 16) radar data; Meteorological data collected on weather reconnaissance 17) visibility at flight level; missions fall into two categories: horizontal data and ver- 18) sea-surface temperature. tical data. Horizontal data consist of data from the Vertical data consist of pressure, temperature, and dew horizontal metsystem, data from other aircraft systems, point depression in a vertical sounding beneath the air- and estimates made by the ARWO of such parameters craft. as cloud types and amounts. They are reported in several Horizontal data are collected by the ARWO using the formats and with varying content depending upon the horizontal metsystem, inputs from the navigator (posi- requirements of individual mission customers. Data tion, time, and flight-level wind), and estimates of such typically reported in horizontal observations are given observational elements as surface wind, clouds, icing below: rates, flight conditions, and other parameters. Horizontal 1) position (latitude and longitude); data are encoded in observation formats appropriate for 2) time; the type of mission being flown. Vertical data are in- 3) flight-level wind direction and speed; itially acquired as pressure, temperature, relative humid- 4) turbulence; ity, and reference signals radioed back to the aircraft 5) flight condition (approximate amount of cloud from expendable called . Sig- above and/or below flight level or amount of time nals from the dropsondes are converted by the DSO into in cloud at flight level); atmospheric soundings by using a programable calculator 6) absolute altitude; or by manual computation if necessary. The completed 7) flight-level temperature; soundings are prepared and transmitted as vertical ob- 8) flight-level dew point; servations or "drops." 9) present weather (precipitation, haze, fog, etc). Dissemination of completed horizontal and vertical 10) height of standard pressure surface or sea-level observations from the aircraft normally is made by voice pressure; over high-frequency (HF) radio through an Aeronautical

TABLE 2. Components of the WC-130 vertical metsystem used in producing vertical atmospheric soundings.

Subsystem Subsystem Components Remarks

AN/AMT-13 radio dropsonde A cylindrical 18 inches long, 3.5 inches in diameter, and weighing 4.7 lb; a small parachute deploys the transmitter antenna and slows the fall rate to ^4600 ft/min AN/AMQ-29 dropsonde MX-9133/AMQ-31 Radiosonde Used to arm the dropsonde and eject it from the aircraft data-recording system Dispenser Unitron Frequency Converter Converts normal aircraft 400 Hz electrical power to 60 Hz power required by certain metsystem components R1196/AMQ-19 Radiosonde Receiver C-8804/AMQ-25A Power Vertical Controls on this panel permit energizing the equipment, Subsystem Control Panel selecting the operating mode, and tuning the receiver in the manual mode

Manual Pressurization/Depressurization Control Panel Hewlett-Packard components: 5332A The Hewlett-Packard 9100B calculator is in the process Preset Controller/Counter, 5216A of being replaced by the newer HP-97 Electronic Counter, 562ARC 10 Digital Recorder, 7128A Strip Chart Recorder, 3310A Function Generator, 9100B Programable Calculator

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TABLE 3. Air Weather Service weather monitors responsible ably illustrated best by considering briefly the tropical for collecting weather reconnaissance data and stations cyclone reconnaissance, tactical support, and East Coast typically used in contacting each weather monitor. winter storm missions with the understanding that these are only a small part of the spectrum of weather recon- Weather USAF Aeronautical Monitor Monitor Location Station naissance operations.

Miami OL G, HQ AWS, Coral MacDill Airways a. Tropical cyclone reconnaissance Gables, Fla. Swan Det. 2, 1WW, Andersen Andersen Airways The mission typically associated with weather recon- AFB, Guam naissance forces is reflected by the nicknames of the Lajes Det. 19, 15WS, Lajes Lajes Airways units: "Typhoon Chasers" (54th WRS), "Storm Field, Azores Islands Trackers" (920th WRG), and "" (53rd Mather Det. 7, 24WS, Mather McClellan Airways WRS). Figure 3, taken in the eye of Hurricane Eloise, AFB, Calif. shows the Florida coastline as the hurricane moved on- Elmendorf Det. 1, 11WS, Elmendorf Elmendorf Airways shore in September 1975 and illustrates part of the AFB, Alaska reason for the emphasis on the tropical cyclone mission. Letterman Base Weather Branch, Hickam Airways The seasonal effort in tropical cyclone reconnaissance Hickam AFTJ, Hawaii forms a large part of each unit's mission. Yokota Metro Yokota AB, Japan Yokota Airways Tropical cyclone reconnaissance missions are flown to Clark Base Weather Branch, Clark Airways support the operations of hurricane and typhoon fore- Clark AB, Philippines cast centers such as the National Hurricane Center in Kindsbach Det. 21, 2WW, Croughton Airways Coral Gables, the Eastern Pacific Hurricane Center in Kindsbach, Germany Redwood City, Calif., the Central Pacific Hurricane Cen- Incirlik TUSLOG Det. 2, Incirlik Airways ter in Honolulu, and the Joint Typhoon Warning Incirlik, Turkey Center at Nimitz Hill, Guam. Missions flown for the hurricane centers are conducted under the provisions of the National Hurricane Operations Plan and applicable Station direct phone patch to a weather monitor. The Air Force directives. Missions flown for the Joint Ty- USAF Aeronautical Stations provide the primary means phoon Warning Center are conducted under military of air/ground communications for relaying weather re- operating instructions and directives. These forecasting connaissance data to the weather monitors. Under nor- agencies consolidate data from weather reconnaissance mal propagation conditions, these stations have an missions with other data from fixed observation sites, effective range of <3000 mi for single-sideband HF satellites, and other sources in forecasting the develop- communications. The weather monitor copies the obser- ment, movement, and intensity of tropical cyclones. vation, checks it for accuracy, and transmits it over long- The primary objective of tropical cyclone reconnais- line teletypewriter. Weather monitor duties typically are sance is the location of the tropical cyclone center, the corollary responsibilities for base weather stations or measurement of meteorological parameters in the center, other AWS facilities. The Miami Monitor, collocated and the reporting of the center location and meteorolog- with the National Hurricane Center in Coral Gables, ical data to the appropriate forecast agency. Location of Fla., is an exception and handles data from tropical the cyclone center is normally accomplished by flying cyclone reconnaissance missions as well as from routine the aircraft into the center by use of the AN/APN-59, reconnaissance tracks. Weather monitors and the Aero- 3 cm radar, visual scanning of surface winds, use of nautical Stations normally used to contact them are Doppler flight-level winds, and data from the horizontal listed in Table 3. metsystem. Flying to the center of the tropical cyclone is referred to as a "penetration" and locating the center by penetration, as a "vortex fix." Under some conditions, 5. Operational employment2 penetration may not be possible, and a "radar fix" of A wide variety of missions are flown by weather recon- the cyclone center is attempted from the 3 cm radar. naissance units, ranging from routine weather recon- Every available source of information is used in locat- naissance tracks over broad ocean areas to weather ing the tropical cyclone center. Constant comparison of modification activities involving fog dispersal and cloud flight level and surface wind direction is made to keep seeding. Missions are flown for many different customers "the left wing into the wind" so that, within known and involved in operations in many different parts of the acceptable limits, direct flight to the cyclone center is world. Typical weather reconnaissance missions are prob- possible. The radar presentation of rainbands is used to determine the approximate location of the cyclone 2 Editor's note: In this section and elsewhere in this paper, center. The radar "eye" return from cyclones with well- SI units have not been used exclusively because it seemed developed wall cloud structures simplifies the location more appropriate in describing weather reconnaissance op- erations to use the units actually employed in the measure- problem unless attenuation from other convective activ- ments. ity masks the return. The aircraft is flown at a "con-

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FIG. 3. This print was made from a color slide taken from a WC-130H orbiting at 10 000ft in the eye of Hurricane Eloise as it moved onshore early in the morning of 23 September 1975. The slide is part of a set taken at -1130 GMT. stant" pressure altitude with the result that the absolute 10) navigational and meteorological fix accuracy (posi- altitude determined from the radar altimeter decreases tion) estimates; as the center is approached. Temperature is also mon- 11) amplifying remarks. itored and increases as the center of a warm core system These data are collected at each vortex fix required by is approached, with the maximum gradient typically the forecast center whenever possible. Sea-level pressure occurring at or near the wall cloud structure, if a wall is acquired by dropsonde from a standard flight altitude cloud is present. Wind speeds are checked continuously; of 10 000ft (~700 mb) or is extrapolated if the mission they increase toward the cyclone center and then fall off is flown at 1500 ft. Except for dropsonde soundings from rapidly as the center is penetrated. Observations are 700 mb, all other measured data are determined at air- taken as necessary and recorded for transmission or for craft flight level. later use in reporting the vortex fix. An in-flight In addition to collecting data in the center of the analysis normally is maintained as an aid in locating tropical cyclone, special flight patterns are flown at the cyclone center and in keeping track of cyclone prog- 10 000ft or at 1500 ft to acquire data in each quadrant ress and development during the mission. of the cyclone. Observations are taken on the flight The types of data collected in the center of the trop- patterns and used to determine the intensity and dis- ical cyclone are summarized below: tribution of flight-level and surface winds, to measure 1) time of the vortex fix; height of standard pressure surface or sea-level pressure 2) position (latitude and longitude) of the vortex fix; profiles, and to determine temperature and dew point 3) minimum height of surface at standard level; profiles in the cyclone. 4) estimate of maximum observed surface wind and A special type of tropical cyclone reconnaissance mis- the bearing and range of that wind from the sion is the investigative mission. These missions are center; flown into areas of suspected tropical cyclone forma- 5) maximum flight-level wind near the center and its tion to determine if a closed cyclonic circulation bearing and range; exists in the suspect area and, if so, to determine the 6) minimum sea-level pressure; strength of the circulation system. Due to the weak, 7) maximum flight-level temperature inside and out- "diffuse" nature of tropical cyclones in the very early side the eye; stages of their development, investigative missions fre- 8) "character" of the eye—its shape, orientation, and quently are among the more challenging encountered by diameter; weather reconnaissance crews. 9) confirmation of the fix time and coordinates, in- b. Tactical support missions formation on how the fix was made, and the pres- sure level (850 mb, 700 mb, etc.) at which the fix Weather reconnaissance tactical support missions are was made; typically of two basic types: pathfinder (or scout) and

Unauthenticated | Downloaded 09/25/21 08:15 AM UTC 1142 Vol. 59, No. 9, September 1978 area reconnaissance. These missions are flown to support meet the demanding conditions of weather reconnais- military operations of various types on a worldwide sance operations. Maintenance requirements may remove basis. The customer for both types of tactical support an aircraft from operations for lengthy periods of time, missions is typically the weather support element at the particularly if "depot-level" maintenance at central facil- highest command level directly involved in the opera- ities is involved. The small number of aircraft in the tion. fleet and maintenance constraints occasionally result in Pathfinder missions are usually flown along the not having an aircraft available to fly a mission. planned route for tactical aircraft deployments to inves- Performance considerations and aircraft basing are tigate flight-level winds along the route and other probably the most fundamental constraints on the effec- weather conditions of significance to the deployments. tiveness of the aircraft. The WC-130 was originally de- Standard observations are reported with wind factor signed as a tactical assault transport capable of medium data in segments along the route and for the entire subsonic speeds, moderate ranges in the later versions, route reported as remarks to the observations. The vast and a low-to-medium altitude capability. Typical WC- majority of peacetime tactical support missions are of the 130 operations involve airspeeds ranging from 190 to pathfinder type. 310 kt (true airspeed), ranges of from 2500 to >4000 n mi, Area reconnaissance missions are flown to support and altitudes from near the ocean surface to ~30 000 tactical operations within a specified area. These mis- ft (~300 mb). Missions may last from 8 to 13 h depend- sions may involve specialized observation codes and ing on the type of mission, crew capability, fuel load, procedures as well as armed escort or other protective and a number of other factors. These performance con- measures in a combat environment. straints and others effectively define the upper limit of the operational profile of the WC-130. c. East Coast winter storms missions The basing of WC-130 weather reconnaissance units Because of the threat of severe and crippling storms at two locations is necessary as an economy measure but along the east coast of the United States during winter, limits the squadrons' ability to rapidly conduct weather special arrangements have been made for providing reconnaissance operations beyond a certain radius of weather reconnaissance observations to use in preparing each base. Airplanes and crews frequently must be de- forecasts and warnings of the onset of such storms. The ployed from their home base to a forward operating loca- National East Coast Winter Storms Operations Plan has tion before beginning reconnaissance operations. This been developed and implemented since 1969 to coordi- limitation especially affects operations from Keesler AFB nate the use of surface platform, aircraft, and satellite since both the 53rd WRS and the 815th WRS conduct observations for forecast and warning use and, if prac- operations over a geographic area ranging from Europe tical, to meet the data requirements of research facil- to the Caribbean and Gulf of Mexico areas and west- ities. The plan is specifically designed to cover the time ward over the central and north Pacific Ocean. of year having a relatively high incidence of winter The meteorological instrumentation aboard the WC- storms along the East Coast, 1 November-15 April, and 130E and WC-130H was originally installed in the WC- generally considers only special arrangements between 130 fleet under Project Seek Cloud, an interim re- various agencies required to provide special weather sponse designed to upgrade the WC-130 meteorological observations. system in the aftermath of Hurricane Camille's destruc- The 815th WRS and 53rd WRS from Keesler AFB fly tive rampage across the Gulf Coast in August 1969. special missions off the East Coast to provide data for Many of the systems presently installed are aging rapidly, forecasts and analyses produced by the National Me- spares are in short supply in some cases, and the overall teorological Center and for the use of military forecast system is not designed to provide the type of high- facilities. Horizontal observations are taken at least every density high-quality data required by some of the newer 30 min while the aircraft is over the open ocean, with numerical forecasting models. The inability of the sys- midpoint data required between each horizontal observa- tem as presently installed to provide routine, high- tion. Vertical observations are taken as required by the density data on a real-time basis is probably the most forecast agencies involved, within the capabilities of the significant limitation of the present meteorological sys- vertical metsystem. tem. The accuracy of the data reported from weather re- 6. Comments on weather reconnaissance connaissance aircraft is hard to determine because of the effectiveness difficulty of comparing reconnaissance observations with A comprehensive analysis of weather reconnaissance ef- radiosonde observations and the fact that most weather fectiveness requires examining a wide range of factors reconnaissance missions are conducted in "data sparse and is considerably beyond the scope of this paper. Only areas," where comparison data are rarely available. a cursory examination of some of the capabilities and Many efforts have been made within the weather recon- limitations of the aircraft and instrumentation is pos- naissance organizations to determine the accuracy of the sible. reported data, all with varying degrees of success. Cur- The WC-130 is a remarkably sturdy and dependable rent estimates of the accuracies of various parameters aircraft but requires considerable maintenance effort to reported in weather reconnaissance horizontal observa-

Unauthenticated | Downloaded 09/25/21 08:15 AM UTC Bulletin American Meteorological Society 1143 tions are generally as given below: nificant improvement over the current horizontal and vertical metsystems aboard the WC-130 fleet, but it is Parameter Accuracy relatively expensive to procure and maintain. Temperature (flight level) ±1°C The increasing need to update the instrumentation Dew point (flight level) ±1°C above 0°C* aboard weather reconnaissance aircraft has led to the ±1.5°C at or below 0°C Sea-surface temperature ±0.5°C development of requirements for an advanced capability Sea-level pressure ±1 mb in the form of what is usually called the Improved Absolute altitude ±10 m* Weather Reconnaissance System (IWRS). The IWRS is Height of standard pressure presently only a concept, with hardware development surface ±3 m at or below 700 mb and deployment awaiting approval and funding. The ±10 m above 700 mbf IWRS concept calls for improvements in the following * Confirmed by operational tests. -[•Estimating height of standard pressure surface ac- curacy is very difficult since the computational procedure is somewhat involved and for other reasons. Operational 1) an improved navigation system; experience indicates that these estimates are reasonable 2) improved wind determination; in most cases. 3) improved flight-level sensors; 4) the capability to provide wind profiles below flight Dropsonde data can generally be considered accurate to level; within 2 mb of pressure at sea level and 1°-1.5°C in 5) automatic data-processing and display; temperature. A new humidity element has reduced the 6) improved telecommunications; inaccuracy of dew point data, but reliable accuracy data 7) improved maintainability and reliability; were not available at this writing. 8) growth capability. The actual accuracy of a given parameter on an opera- tional mission is a function of many variables and is The improvement in WC-130 weather reconnaissance difficult to assess but should approximate the values effectiveness resulting from a fleet-wide IWRS capability given above. The accuracy of height of standard pressure would generally match that of deployment of the AWRS. surface and sea-level pressure data is particularly hard The future of the IWRS as a viable system for weather to evaluate since three systems are used in the basic com- reconnaissance operations is uncertain. Many of the putation and a "historical correction" calibration proce- IWRS improvements may be incorporated as changes dure is used to produce compatibility with routine to the present meteorological system. upper-air data. Generally, height of standard pressure Other improvements in WC-130 capability are being surface data from weather reconnaissance aircraft is ex- made while awaiting the development of an advanced pected to be at least as accurate as current radiosonde system. Hewlett-Packard HP-97 calculators were first data. used on WC-130 aircraft in 1977 and have greatly im- proved data handling on weather reconnaissance mis- 7. Improving the weather reconnaissance force sions. The aging, logistically unsupportable 1301A sys- In this decade, several efforts have been made to develop tem is being replaced. A secondary absolute altimeter an effective weather reconnaissance system for fleet-wide (the AN/APN-133) is being added to the WC-130H hori- deployment on WC-130s or to improve the present me- zontal metsystem to correct a metsystem deficiency that teorological system. As an example of the latter, the has plagued the WC-130H since it first joined the fleet recent use of a modern, programable calculator (the in 1973. New Omega navigation systems permit much Hewlett-Packard HP-97) has greatly speeded computa- greater position accuracies than were previously pos- tions aboard the aircrift and can be expected to reduce sible, a factor that is very important in tropical cyclone the operator error rate as well as increase the time reconnaissance operations. These improvements, signif- available for in-flight quality control of the data and icant though they are, still represent only relatively other duties. minor improvements to the basic, "interim" Seek Cloud A prior and much more ambitious effort initiated in metsystem. the early 1970s was the Airborne Weather Reconnais- sance System (AWRS), which is operational in prepro- 8. Concluding remarks duction form on a single WC-130B operated by the 53rd This brief introduction to Air Force WC-130 weather WRS. The system was developed to provide high-density, reconnaissance has necessarily omitted a great deal of high-quality data for the forecast models envisaged for detail in an attempt to provide a quick overview of the the mid- and late 1970s. The AWRS uses six interrelated organization, equipment, and typical operations of subsystems to provide an advanced, interactive data weather reconnaissance units. More specific information reduction and transmission capability: a flight-level data- is available in various military regulations or publica- sensing subsystem, a vertical profile sensing subsystem, tions or, for qualified requestors, can be obtained from a navigation subsystem, a communications subsystem, an Headquarters Air Weather Service, Directorate of Re- automatic data-processing subsystem, and a mission con- connaissance, Scott AFB, 111. 62225 (Autovon 638- troller console/display subsystem. The AWRS is a sig- 4624). •

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