Radiosonde Observations
(Raobs) Upper Air Obs
AOS 330 Lab 6
Early Upper Air Observations
1930
1900’s
•
http://www.ua.nws.noaa.gov/photo.htm
Early Upper Air Observations cont.
1930
•
http://www.ua.nws.noaa.gov/photo.htm
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/n
ws_upper.htm
Temp.
Sensor
Radiosonde Package
Balloon Attachment point
GPS antenna
Humidity
Sensor
Unwinder
www.chmi.cz/meteo/ oap/eoap_basic.html
Reciever/Processo
r
Calibration
check box
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
Balloon
Radiosonde with GPS
Receiver
Biodegradable
Parachute
http://www.wrh.noaa.gov/rev/tour/UA/equipment.php
Radiosonde Replacement System (RRS)
Activate the data acquisition system
an antenna
which is housed
in a radome
observing computer
http://www.wrh.noaa.gov/rev/tour/UA/inflation.php
Inflating the balloon
http://www.wrh.noaa.gov/re
v/tour/UA/inflation.php
Baselining the Radiosonde
Sensor Inspection and Battery Materials,
write down the radiosonde calibration
information
http://www.wrh.noaa.gov/rev/tour/UA/baseline.php
Radiosonde being Baselined and
Acquiring GPS Information
Balloon Launch
airport
Reno-Tahoe International Airport
view from Launch Site
Before the launch, obtain
measurements of local T,
humidity, and P
Wait to get clearance from Federal Aviation
Administration (FAA)
(http://www.wrh.noaa.gov/rev/tour/UA/launch.php)
Balloon Launch
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.
(http://www.wrh.noaa.gov/rev/tour/UA/launch.php)
NSSL/SWAMP Radiosonde Balloon
Launch
• http://www.weathergraphics.com/tim/raob/
Rawinsonde Data
Rawinsonde Plot at
500hPa
Skew-T/log-P
http://www.rap.ucar.edu/weather/upper/
Upper Air Plot Model
WS

TT
WD
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/essd24aug
Released from a Hurricane
98_1.htm
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 down 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/wxiraob.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.
Thermodynamic Diagrams
AOS 330 Lab 6
Thermodynamic Diagram
• Graphically display thermodynamic processes that occur in the
atmosphere (isobaric, isothermal, dry adiabatic, pseudoadiabatic,
etc.)
• Abscissa and ordinate are designed to represent 2 of the 3 state
variables
• Any dry atmospheric state may be plotted
• Any moist state cannot be plotted as unique points, however
vapor content can be known by plotting dew point temperature.
• Other moist processes can be accounted for by assuming certain
characteristic of the moist process to be pseudo-adiabatic
Potter and Coleman 2003, Hess 1959
Three Desirable Characteristics of a
thermodynamic diagram
1. Area enclosed by a cyclic process is proportional to the
change in energy or the work done during the process
(Area α Energy/Work)
2. As many as possible of the fundamental lines are
straight
3. Angle between isotherms (T) and isentropes (Θ) are to
be as large as possible
• Easier to see the stability variations of the environment
• Isotherm – Isentropes angle : 90 deg. optimum
Potter and Coleman 2003, Hess
1959
Coordinates of thermodynamic
diagrams
• Selected so that it satisfies the area equivalent
characteristics (Enclosed Area proportional to
Energy)
Angle
between
isotherms and
isentropes is
small in p-
diagram.
P


dw = pd
Must seek other
diagrams in which the
coordinates are two
functions of
thermodynamic
variables, yet under
the restriction that the
area enclosed by any
cycle in new diagram
to be equal to that of
the old
A
B
Equal-area transforamtion on p-diagram to
A-B diagram
Hess 1959
Equal-Area Transformation
A
P


B
Let A,B to each be a function of one of more thermodynamic variables.
Since a thermodynamic variable is determined by the state of system, if you
know and p, you would also be able to determine A and B.
Each point on p-diagram corresponds to a point on A-B diagram.
Any closed cycle on p-diagram is also closed cycle on A-B diagram.
Hess 1959
Equal-Area Transformation
A
P


B
For the area enclosed on one diagram to be equal to the area enclosed on
the other,
- ∮pd= ∮AdB
∮(pd + AdB) =0
For closed lines intergral to be 0, the intergrand must be an exact differential.
For example, set ds = pd + AdB so that s=f(,B)
Cyclic process:
Hess 1959
Equal-Area Transformation
For example, set ds = pd + AdB so that
s=f(,B)
A
P


From calculus:
B
s 
s 
ds(,B)    d    dB
 B
B 
Sufficient conditions for an equal
area transformations are:
DifferentiateP
partially with B and A
partially with 
s 
p 
 2 s A  
 
  
B 
B  B
A 
 2s
  
 B B

A 
 2s
  
 B B
Hess 1959
Equal-Area Transformation
For example, set ds = pd + AdB so that
s=f(,B)
A
P


Differentiate P
partially with B and A
partially with 
B
p 
 2s
  
B  B
A  p 
    
 B B 
A  p 
Therefore if      , the areas will be equal on the two
 B B 

diagrams

Hess 1959
Types of Thermodynamic Diagrams
Emagram
Log Pressure
∮dw =-R∮Td(lnp)
Area∝
Energy
T versus q
angle:
45 degrees
A = -R lnp
B=T
Temperature
abscissa
http://en.wikipedia.org/wiki/File:Emagram.GIF
Tephigram TΦ(entropy)
Most commonly used by
tropical meteorologist
Good for capturing the
stability variations of the
environment sounding.
Area ∝ Energy
T versus qangle:
90 degrees
∮dq = ∮Tds = cp∮Td(lnΘ)
A = cp ln Θ
B=T
http://en.wikipedia.org/wiki/File:Tephigram.gif
Skew T / Log P Diagram
Log Pressure
Most commonly used in
the mid latitudes
Suggested by Herlofson in
1947 to increase the angle
betweem isotherms and
isentropes on an
emagram (Hess,1959)
Area∝ Energy
T versus qangle: almost
90 degrees
A = T + K lnp
B = -R lnp
http://upload.wikimedia.org/wikipedia/en/1/17/Skew-T.gif
Stüve Diagram
Allows
isentropes to
be straight lines
but area here
does not
proportional to
energy
Of limited use,
not common
http://upload.wikimedia.org/wikipedia/en/7/7c/Stuve-diagram.gif
References
• Potter and Coleman, 2003a: Handbook of Weather, Climate
and Water: Dynamics, Climate, Physical Meteorology,
Weather Systems and Measurements, Wiley, 2003
• Hess, 1959: Introduction to Theoretical Meteorology, Holt,
Rinehart and Winston, 1959