Meteorological Sounders
Dr. Bernie Connell
CIRA/NOAA-RAMMT
March 2005
CIRA & NOAA/NESDIS/RAMM
Outline
GOES Sounder
Types of soundings
Channels
Absorption regions (CO2, H2O, O3)
Retrievals (Temperature and Humidity)
Derived Product Imagery (DPI)
POES – Microwave sounder
CIRA & NOAA/NESDIS/RAMM
Passive Atmospheric Soundings
Two basic types:
• Vertical sounding – the sounding instrument
senses radiation coming from the atmosphere and
the earth’s surface.
• Limb sounding – the sounding instrument senses
radiation in the upper atmosphere from the earth’s
limb.
CIRA & NOAA/NESDIS/RAMM
Weighting function
• Derived from the vertical change of transmittance
(dτ/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
CIRA & NOAA/NESDIS/RAMM
Absorption regions for CO2, H2O, and O3
Satellite Meteorology: Using the GOES Sounder
CIRA & NOAA/NESDIS/RAMM
Midwave
1
14.71
CO2, Stratosphereic
temperature
10
7.43
Water vapor, Lower to midlevel 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, lowertropospheric 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
Comment (spectral
region, application)
Resolution = 10 km at nadir
Satellite Meteorology: Using the GOES Sounder
Channel
Center
Wavelength
(um)
Comment (spectral
region, application)
Shortwave
Channel
Center
Wavelength
(um)
Midwave
Longwave
GOES Sounder Channels
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.
CIRA & NOAA/NESDIS/RAMM
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
CIRA & NOAA/NESDIS/RAMM
Weighting Functions for 2 points: wet and dry
CO2 channels 1 - 5
Weighting Functions for 2 points: wet and dry
H2O channels 10 -12
10-12
Example of all channels for the GOES-12 Sounder
CIRA & NOAA/NESDIS/RAMM
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
CIRA & NOAA/NESDIS/RAMM
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
CIRA & NOAA/NESDIS/RAMM
Retrieval of profiles from the GOES Sounder by
NESDIS (physically based)
Radiance at Satellite =
(surface blackbody radiance*surface emissivity*atmospheric 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
CIRA & NOAA/NESDIS/RAMM
GOES Sounder Products
Derived Product Imagery (DPI)
Lifted Index
CAPE
Convective Inhibition
Total Precipitable Water
Surface Skin Temperature
Water vapor winds
CIRA & NOAA/NESDIS/RAMM
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/goes/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
CIRA & NOAA/NESDIS/RAMM
Total Precipitable Water
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/goes/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
CIRA & NOAA/NESDIS/RAMM
Lifted Index
positive values – stable air mass
negative values – unstable air mass
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/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
CIRA & NOAA/NESDIS/RAMM
Skin Temperature
CIRA & NOAA/NESDIS/RAMM
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/goes/sdpi/html/sdpiimgnewt.html
GOES sounder data and products
CIRA & NOAA/NESDIS/RAMM
Cloud top pressure
CIRA & NOAA/NESDIS/RAMM
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
CIRA & NOAA/NESDIS/RAMM
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.
CIRA & NOAA/NESDIS/RAMM
Microwave Spectrum and Channel locations
Region for Temperature Sounding between 50 and 60 GHz
CIRA & NOAA/NESDIS/RAMM
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
Source: Kidder and Vonder Haar (1995)
Notation: x±y±z; 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.
CIRA & NOAA/NESDIS/RAMM
Stan Kidder’s AMSU web page at CIRA: http://amsu.cira.colostate.edu/
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)
CIRA & NOAA/NESDIS/RAMM
TPW from AMSU and SSMI
3 channels centered at 183 GHz
for moisture sounding / TPW
23GHz for TPW
Weighting functions for AMSU – B
courtesy 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 Kidder’s AMSU web page at CIRA: http://amsu.cira.colostate.edu/
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/
CIRA & NOAA/NESDIS/RAMM
AMSU Products
• Microwave Surface and Precipitation Products
System (MSPPS)
http://www.orbit.nesdis.noaa.gov/corp/scsb/mspps/main.html
• CIRA’s AMSU Website
http://amsu.cira.colostate.edu/
CIRA & NOAA/NESDIS/RAMM
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 Kidder’s 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
CIRA & NOAA/NESDIS/RAMM
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/realtime.html
Stan Kidder’s 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/main.html
CIRA & NOAA/NESDIS/RAMM