Radiosonde Observations(Raobs) Upper Air Obs

AOS 330 Lab 6

Early Upper Air Observations

• http://www.ua.nws.noaa.gov/photo.htm

1900’s1930

Early Upper Air Observations cont.

• http://www.ua.nws.noaa.gov/photo.htm

1930 1936

Basic Definitions

Radiosonde is a balloon-borne instrument platform used to measure and transmit simultaneously meteorological data while ascending through the atmosphere. The instrument consists of sensors for the measurement of pressure, temperature and relative humidity.

Definitions (cont.)

Rawinsonde is a radiosonde that is tracked to provide wind speed and direction.

Pibal (Pilot balloon) is an uninstrumented balloon that is tracked to provide information on wind speed and direction.

Radiosonde Observations (Raobs)• ~800 Radiosonde sites worldwide, 92 Radiosonde stations in U.S.• Launch at the same time twice a day (prior to 00UTC and 12UTC)* to take “snapshot” of

the upper atmosphere*UTC- Coordinated Universal Time or Zulu (Z) time/ formerly Greenwich Mean Time (GMT)• The complete radiosonde system, or rawinsonde, consists of a balloon-borne

radiosonde instrument package, a radio receiver, a tracking unit, and a recorder.

http://www.ua.nws.noaa.gov/nws_upper.htm

Radiosonde PackageTemp. Sensor

Humidity Sensor

Receiver/Processor

Calibration check box

www.chmi.cz/meteo/ oap/eoap_basic.html

GPS antenna

Unwinder

Balloon Attachment point

Transmitter Antenna

Radiosonde Package cont.• T : measured by small rod thermistor / capacitive wire sensor (small size

allows quick responses to changes in T)• Relative Humidity : Carbon hygristor / thin-film electrical capacitance sensor• P : Aneroid barometer / silicon-based solid state pressure transducers • Navigation unit : need to track the horizontal position of the radiosonde as it

ascends to calculate the upper level winds. External methods include: optical tracking / radar

• Most modern ones have internal nevigation system such as an Omega LORAN (Long Range Nevigation) receiver, or GPS (Global Positioning System) unit.

• Transmitter : to transmit the measurements made by sensors to ground using coded radio signal ~404MHz or 1680 MHz

• Battery : to power the radio transmitter (chemical battery, activate with water)

(Petty, G.2008)

Radiosonde Package cont.

Ground station:• Antenna subsystem: capture signals of the radiosonde• Receiver and data processing subsystem: receive radio

signals from the radiosonde and decode them into raw engineering units. Part of processing include applying hypsometric equation to get thickness at each sounding level. Wind speed and direction at each level is also calculated if there is a navigation / tracking subsystem.

• Display and output: On computer display and raw data can be read out to storage devices.

NWS Radiosonde Balloon Launch

http://www.wrh.noaa.gov/rev/tour/UA/equipment.php

Balloon

BiodegradableParachute

Radiosonde with GPS Receiver

Radiosonde Replacement System (RRS)

http://www.wrh.noaa.gov/rev/tour/UA/inflation.php

observing computer

an antenna which is housed in a radome

Activate the data acquisition system

Inflating the balloon

http://www.wrh.noaa.gov/rev/tour/UA/inflation.php

Baselining the Radiosonde

http://www.wrh.noaa.gov/rev/tour/UA/baseline.php

Sensor Inspection and Battery Materials, write down the radiosonde calibration information

Radiosonde being Baselined and Acquiring GPS Information

Balloon Launch

Reno-Tahoe International Airport view from Launch Site

airport

Wait to get clearance from Federal Aviation Administration (FAA)

(http://www.wrh.noaa.gov/rev/tour/UA/launch.php)

Before the launch, obtain measurements of local T, humidity, and P

Balloon Launch

(http://www.wrh.noaa.gov/rev/tour/UA/launch.php)

After release the balloon, activate the tracking system and monitor the data during the ascent.

Pre-launch takes about 30 mins, while sounding may take about 90 mins.

NSSL/SWAMP Radiosonde Balloon Launch

• http://www.weathergraphics.com/tim/raob/

Rawinsonde Data

http://www.rap.ucar.edu/weather/upper/Skew-T/log-P

Rawinsonde Plot at 500hPa

Upper Air Plot Model

WS

WD

TT

DD

HHH

TT – Temperature (deg. C)DD – Dewpoint Depression (deg. C)HHH – Height (m)WS – Wind Speed (knots)WD – Wind Direction (degrees)The station circle is filled when the dew point depression is < 5 deg. C

http://profhorn.meteor.wisc.edu/wxwise/weather/lesson3/Upper_Air_Maps.html#

Dropsonde

http://spacescience.spaceref.com/newhome/headlines/essd24aug98_1.htm

Released from a Hurricane Hunters aircraft

To prepare for the launch

• Since we need to fill the balloon up with Helium, make sure the Helium bottle is not empty

• Need water for activating the battery• Balloon• Sonde• At the roof, record 1) weather conditions at time of

launch (temperature, dewpoint, wind speed and direction, sky cover and cloud type(s)) 2) launch time, and 3) estimated ascent rate (from data on terminal readout).

References

• http://www.aos.wisc.edu/~hopkins/wx-inst/wxi-raob.htm

• http://www.ua.nws.noaa.gov/factsheet.htm• http://www.wrh.noaa.gov/rev/tour/UA/

introduction.php• http://www.weathergraphics.com/tim/raob/• Petty, G (2008). A First Course in Atmospheric

Thermodynamics, Sundog Publishing.