Meteorological Sounders

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Meteorological Sounders

• Dr. Bernie Connell
• CIRA/NOAA-RAMMT
• March 2005

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Outline

• GOES Sounder
• Types of soundings
• Channels
• Absorption regions (CO2, H2O, O3)
• Retrievals (Temperature and Humidity)
• Derived Product Imagery (DPI)
• POES Microwave sounder

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Passive Atmospheric Soundings

• Two basic types
• Vertical sounding the sounding instrument
  senses radiation coming from the atmosphere and
  the earths surface.
• Limb sounding the sounding instrument senses
  radiation in the upper atmosphere from the
  earths limb.

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Weighting function

• Derived from the vertical change of transmittance
  (dt/dp)
• Specifies the relative contributions to the
  outgoing radiance from various levels of the
  atmosphere.
• Determines the layer of the atmosphere that is
  sensed for a given spectral channel.
• The peak occurs at the pressure level that
  provides the largest contribution detected by the
  satellite
• Contributions from individual spectral channels
  come from deep and overlapping layers.

Satellite Meteorology Using the GOES Sounder
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Absorption regions for CO2, H2O, and O3
Satellite Meteorology Using the GOES Sounder
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GOES Sounder Channels
Channel Center Wavelength (um) Comment (spectral region, application) Channel Center Wavelength (um) Comment (spectral region, application)
1 14.71 CO2, Stratosphereic temperature 10 7.43 Water vapor, Lower to mid-level tropospheric moisture
2 14.37 CO2, Stratosphereic temperature 11 7.02 Water vapor, mid-level tropospheric moisture
3 14.06 CO2, Upper-tropospheric temperature 12 6.51 Water vapor, upper-level tropospheric moisture
4 13.96 CO2, Mid-tropospheric temperature 13 4.57 CO2, Lower-level tropospheric temperature
5 13.37 CO2, Lower-tropospheric temperature 14 4.52 CO2, Mid-level tropospheric temperature
6 12.66 Water vapor, lower-tropospheric moisture 15 4.45 CO2, Upper-level tropospheric temperature
7 12.02 Water vapor, dirty (moisture contaminated) window 16 4.13 CO2, Boundary-layer temperature
8 11.03 Window, cloud-top and surface temperature 17 3.98 Window, cloud top and surface temperature
9 9.71 Ozone, stratospheric ozone 18 3.74 Window, cloud top and surface temperature
Visible 0.94 Visible window, cloud top and surface features
Midwave
Longwave
Shortwave
Midwave
Resolution 10 km at nadir
Satellite Meteorology Using the GOES Sounder
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Greatest absorption by the gas occurrs near the
center of an absorption region (indicated by
yellow arrows in the above diagram) This usually
corresponds to colder brightness temperatures,
indicating that the energy is being emitted from
higher levels of the troposphere.
Satellite Meteorology Using the GOES Sounder
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Weighting Function

• 1 - 14.71 um
• 2 - 14.37 um
• 3 - 14.06 um
• 4 13.96 um
• 5 - 13.37 um
• 6 - 12.66 um
• 7 - 12.02 um

channels 1 5 CO2 channels channel 6 low
level water vapor channel 7 window channel Note
the location and shapes of the weighting functions
Satellite Meteorology Using the GOES Sounder
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Weighting Functions for 2 points wet and dryCO2
channels 1 - 5
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Weighting Functions for 2 points wet and dryH2O
channels 10 -12
10-12
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Example of all channels for the GOES-12 Sounder
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Example Determination of Temperature profile in
CO2 absorption region

• Radiance to space near the center of the
  absorption region (14.7 micrometers) usually
  corresponds to colder satellite brightness
  temperatures
• Away from the center of an absorption region,
  brightness temperatures increase as absorption by
  the gas decreases, and radiation from lower in
  the troposphere reaches the satellite.
• By selecting several spectral channels between
  the center and wing of an absorption region,
  the atmosphere can be probed at different depths

Satellite Meteorology Using the GOES Sounder
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Retrieval Methods

• Given a set of observed radiances, what is the
  temperature profile?
• This is called the inverse problem or retrieval
  problem.
• There are three general approaches to retrievals
• Physical retrievals
• Statistical retrievals
• Hybrid retrievals

Satellite Meteorology Using the GOES Sounder
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Retrieval of profiles from the GOES Sounder by
NESDIS (physically based)
Radiance at Satellite (surface blackbody
radiancesurface emissivityatmospheric
transmittance) atmospheric contribution from
many layers.

• After cloud-clearing, the GOES Sounder radiance
  measurements are spatially averaged over small
  areas to improve signal-to-noise ratio.
• A first guess profile is obtained from a NWP
  model, modified by the latest hourly surface
  reports. Radiances are then calculated for these
  model first-guess profiles.
• The first-guess profiles are then adjusted until
  the calculated radiances match the observed GOES
  Sounder radiances (within some threshold).

Satellite Meteorology Using the GOES Sounder
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GOES Sounder ProductsDerived Product Imagery
(DPI)
Lifted Index
CAPE
Convective Inhibition
Total Precipitable Water
Surface Skin Temperature
Water vapor winds
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Total Precipitable Water

• Utilizes split window technique to determine
  boundary-layer moisture (11.0 12.0 micrometer
  difference), and the 3 water vapor channels
  (6.5, 7.0, 7.5 micrometer) for mid-tropospheric
  moisture.

http//cimss.ssec.wisc.edu/goes/realtime/realtime.
html http//www.orbit.nesdis.noaa.gov/smcd/opdb/g
oes/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
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Total Precipitable Water
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Lifted Index

• Utilizes retrieved temperature/moisture profile
• Parcel lifted mechanically from 1000 mb level up
  to 500 mb level
• Operational applications convective potential
  convective morphology

http//cimss.ssec.wisc.edu/goes/realtime/realtime.
html http//www.orbit.nesdis.noaa.gov/smcd/opdb/g
oes/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
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Lifted Index
negative values unstable air mass
positive values stable air mass
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Skin Temperature

• Utilizes longwave IR window channels (11.0, 12.0
  micrometer), plus shortwave channel (3.8
  micrometer) at night
• Operational applications fog forecasting
  frost/freezing temperature forecasting highlight
  regions of differential heating.

http//www.orbit.nesdis.noaa.gov/smcd/opdb/goes/sd
pi/html/sdpiimgnewt.html
GOES sounder data and products
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Skin Temperature
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Cloud Top Pressure

• Utilizes longwave IR window (11.0, 12.0
  micrometer) and CO2 channels (13.4, 13.9, 14.1
  micrometer)
• Uses visible channel and/or shortwave IR channel
  (4.0 micrometer) for cloud clearing
• Operational applications supplement ASOS
  aviation TAFs

http//cimss.ssec.wisc.edu/goes/realtime/realtime.
html http//www.orbit.nesdis.noaa.gov/smcd/opdb/g
oes/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
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Cloud top pressure
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GOES Soundings and Derived Product Imagery

• Advantages
• Hourly products
• Shows trends, gradients, and advection
• Indicates instability prior to cloud development
• A good check against models
• Disadvantages
• Coarse vertical resolution (only 18 IR channels)
• Clouds prevent retrieval profiles
• Specific (FOV) values not as indicative as trends
• Potential for elevated convection not diagnosed
• Product availability not timely (1 hour past
  valid time)
• Limited coverage

GOES sounder data and products
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POES - Microwave

• 19 200 GHz sensed by SSM/I and AMSU
• Frequencies below 200 GHz are relatively
  insensitive to cirrus clouds
• Frequencies below 50 GHz lie within an
  atmospheric window region and are primarily
  sensitive to emission by water vapor, clouds,
  precipitation, and surface features.

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Microwave Spectrum and Channel locations
Region for Temperature Sounding between 50 and 60
GHz
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AMSU-A AMSU-B
Channel Frequencies (GHz) and Polarizations Frequencies (GHz) and Polarizations
1 23.8 R 89.0R
2 31.4R 157.0R
3 50.3R 183.3 /- 1R
4 52.8R 183.3 /- 3R
5 53.6R 183.3 /- 7R
6 54.4R
7 54.9R
8 55.5R
9 57.2R
10 57.29 /- .217R
11 57.29 /- .322 /- .048R
12 57.29 /- .322 /- .022R
13 57.29 /- .322 /- .010R
14 57.29 /- .322 /- .0045R
15 89.0R
Notation xyz x is the center frequency. If y
appears, the center frequency is not sensed, but
two bands, one on either side of the center
frequency, are sensed y is the distance from
the center frequency to the center of the two
pass bands. If z appears, it is the width of the
two pass bands. Polarization R rotates with
scan angle.
Source Kidder and Vonder Haar (1995)
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Stan Kidders AMSU web page at CIRA
http//amsu.cira.colostate.edu/
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SSM/T
Frequency MHz Polarization
50.5 H
53.2 H
54.35 H
54.9 H
58.4 V
58.825 V
59.4 V
Application Vertical Temperature Sounding
Polarization V vertical, H horizontal
Source Kidder and Vonder Haar (1995)
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TPW from AMSU and SSMI
3 channels centered at 183 GHz for moisture
sounding / TPW
23GHz for TPW
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Weighting functions for AMSU Bcourtesy of Tom
Greenwald
C3 183.3 /- 1R GHz C4 183.3 /- 3R GHz C5
183.3 /- 7R GHz
Note AMSU-B channels 1-5 are often referred to
as AMSU channels 16-20.
Stan Kidders AMSU web page at CIRA
http//amsu.cira.colostate.edu/
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AMSU Products
TPW

• Total Precipitable Water (TPW)
• Cloud Liquid Water (CLW)
• Rain rate
• Snow and Ice cover

CLW
Ice cover
Rain rate
Snow cover
http//amsu.cira.colostate.edu/
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AMSU Products

• Microwave Surface and Precipitation Products
  System (MSPPS)
• http//www.orbit.nesdis.noaa.gov/corp/scsb/mspps/m
  ain.html
• CIRAs AMSU Website
• http//amsu.cira.colostate.edu/

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References

• CDs produced by the COMET program (see
  meted.ucar.edu)
• Polar Satellite Products for the Operational
  Forecaster
• POES Introduction and Background
• POES Microwave Applications
• An Introduction to POES Data and Products
• Satellite Meteorology Remote Sensing Using the
  New GOES Imager
• Satellite Meteorology Using the GOES Sounder
• Kidder, S.Q., and T.H. Vonder Haar, 1995
  Satellite Meteorology. Academic Press, 466 pp.
• Stan Kidders AMSU webpage at CIRA
  http//amsu.cira.colostate.edu/
• NOAA/NESDIS Office of Research and Applications
  (ORA) Operational Products Development Branch
  (OPDB)
• Derived GOES sounder products
• http//orbit-net.nesdis.noaa.gov/goes/sdpi/
• The Cooperative Institute for Meteorological
  Satellite Studies Realtime GOES Page
  http//cimss.ssec.wisc.edu/goes/realtime/realtime
  .html
• NOAA/NESDIS/ORA/Hydrology Team/Microwave Remote
  Sensing Project
• Microwave Surface and Precipitation Products
  System (MSPPS)
• http//www.orbit.nesdis.noaa.gov/corp/scsb/mspps
  /main.html

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Lab

• Learn to navigate the following links to locate
  imagery for your region
• GOES Derived Product Imagery
• NOAA/NESDIS/ORA/OPDB
• http//orbit-net.nesdis.noaa.gov/goes/sdpi/
• CIMSS
• http//cimss.ssec.wisc.edu/goes/realtime/realti
  me.html
• Stan Kidders AMSU webpage at CIRA
• http//amsu.cira.colostate.edu/
• Microwave Surface and Precipitation Products
  System (MSPPS)
• http//www.orbit.nesdis.noaa.gov/corp/scsb/mspps/m
  ain.html