U.S. Radiosondes Jan. 2000, NWS awarded contracts to two radiosonde manufacturers, Sippican and InterMet Systems, for the development and submission of GPS radiosondes for the NWS Radiosonde Replacement System. NWS is replacing all radiosonde systems with GPS sondes. All U.S. commutators are electronic chronometric type, switching between sensors and reference at a set time interval.

Sippican Inc. - purchased VIZ –VIZsonde Carbon Hygristor Bead thermistor Aneroid Pressure sensor

–GPS Mark II Microsonde GPS system –Wind derived from GPS system Pressure data derived from hydrostatic equation incorporating GPS altitude, temperature, humidity and surface pressure May also include Capacitance Aneroid Pressure sensor –±0.5 mb Temperaure - Thin rod thermistor, ±0.2 o C Humidity - Carbon hygristor ±2% RH Transmits on 403 MHz frequency Samples all parameters every 1.2 sec. Electronic Chronometric

–Sippican GPS W-9000 Meteorological Processing System. PC based processer. Receives data on 403 or 1680 MHz frequency Produces WMO Upper air messages Produces plots of temp. dew point, height Produces index of refraction tables

Intermet –Produces a Telemetry Receiver System –Required for non-GPS radiosondes. –Receives data on 1680 MHz –Systems computer generates upper air messages

Vaisala –Produces RS80 Series radiosondes. 403 or 1680 MHz transmitter RS80-15G Latest GPS sonde Pressure Sensor: BAROCAP capacitive aneroid –Accuracy: ±0.7 to 1.5 hPa Temperature Sensor: THERMOCAP capacitive bead –Accuracy: ±0.5 o C Humidity Sensor: HUMICAP thin film capacitor –Accuracy: ±5%

RS-90 radiosonde –403MHz or 1680 MHz transmitter –Loran-C or GPS –Same sensors as in RS-80 series

–Uses 2 HUMICAP humidity sensors. Operate in two phases. While one sensor is measuring, the other sensor is heated and then allowed to recover before being used to measure. –Top wire is thermistor –Bottom white sensors are humicap sensors.

Vaisala Dropsonde Developed by NCAR

Vaisala Radiotheodolite Operates on the 1680 MHz band.

Rocketsonde Releases parachute and sonde when reaches apogee. Measures temperature, pressure, humidity as it descends. Low - altitude, small rockets.

Accuracy of Radio/Rawinsonde Systems Temperature: Overall ±1 o C –Warmer temperatures: ~0.1 o C Humidity: Overall ±5% for temperatures above freezing Pressure: ± hPa Pressure Altitude (using radiodirection finders) 10 gpm at 500 hPa, 20 at 300 hPa, 50 at 50 hPa

Errors in altitude due to systematic error of 1 o C 50 hPa 87.7 gpm 100 hPa 67.5 gpm 200 hPa 47.1 gpm 300 hPa 35.3 gpm 400 hPa 26.8 gpm 500 hPa 20.7 gpm 600 hPa 15.3 gpm 700 hPa 10.7 gpm 800 hPa 6.7 gpm 900 hPa 3.1 gpm 1000 hPa 0.0 gpm

Typical Radio-theodolite wind finding accuracy Altitude <30 kts kts kts 10,000 ft 1 kt3 kt 6 kt 20,000 ft 2 kt5 kt 11 kt 40,000 ft 4 kt10 kt 21 kt 60,000 ft 2 kt7 kt 15 kt 80,000 ft 3 kt10 kt 21 kt 100,000 ft 4 kt12 kt 26 kt

Azimuth errors: ~0.05 o Elevation errors: ~0.05 o Greater the elevation and stronger the wind, the greater the error. Wind direction: Errors increase with altitude and decreasing elevation angles –700 hPa: 1.3 o to 9.5 o. –500 hPa: 1.8 o to 13.4 o

Navigation Aid Methods Systems to improve the position determination of radiosondes Most common systems –LORAN C –GPS

Loran C Long Range Navigation Utilizes reception by the radiosonde of the pulses transmitted on a carrier wave from a master Loran station and two or more slave stations in the same group of stations. The phase difference between pulses from the slave station referenced to the master station provides position information.

GPS Global positioning system Radiosonde receives signal from a number of the 24 GPS satellites and retransmits them to ground station. Phase difference between reception of the signals from the satellites is used to determine position information.

Micro-Lab 1 (Orbview) Satellite Measures doppler shift of signals from GPS satellites which are passing through the limb of the Earth’s atmosphere and being occulted (altered in amplitude and phase) by the atmosphere. Vertical temperature and pressure profiles can be obtained from the measurements. Accuracies of 1 to 2 o K for altitudes from 5 km to 35 km.

Automated Aircraft Observing and Reporting System AMDAR: Aircraft Meteorological Data Relay –Program to input automatically sensed aircraft data into the Global Telecommunications System –Two main Systems 1. ASDAR: Aircraft to Satellite Data Relay. Processor automatically reports winds, temperature, position to satellite every 7 minutes.

2. ACARS: Aeronautical radio incorporated Communication Addressing and Reporting System. –Processor automatically reports winds, temperature and position to one of 600+ VHF ground stations in North and Central America, Hawaii, Caribbean, U.S. Territories. –Weather info. Can be transmitted to the aircraft using the same system. MOZAIC: Automatic system developed to measure ozone, water vapor and temperature. Currently used on European Aerobus 340 aircraft.

FANS: Future Air Navigation System –Digital air-ground, air-satellite-ground, data exchange system to transmit sensed weather data: position, heading, temperature, winds, humidity, turbulence, etc.

Non-Automated Aircraft Observing and Reporting Systems AIREPS: Inflight Weather Reports: Weather information, temperature, turbulence, icing, cloud types, bases, tops, frontal positions, hail, thunderstorms. SIGMETS: Significant Meteorological Conditions: Active thunderstorm area, tropical storm, severe squall line, heavy hail, severe turbulence, severe icing, marked mountain waves, widespread sandstorm/duststorm. Position, altitude, heading, weather information radioed to ground controllers

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