Meteorological Sounders

CIRA & NOAA/NESDIS/RAMM

Meteorological Sounders

Dr. Bernie Connell

CIRA/NOAA-RAMMT

March 2005


Outline

GOES Sounder

Types of soundings

Channels

Absorption regions (CO2, H2O, O3)

Retrievals (Temperature and Humidity)

Derived Product Imagery (DPI)

POES – Microwave sounder


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.


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/RAMMSatellite Meteorology: Using the GOES Sounder

Absorption regions for CO2, H2O, and O3

GOES Sounder Channels

ChannelCenter Wavelength

(um)

Comment (spectral region, application)

ChannelCenter Wavelength

(um)

Comment (spectral region, application)

1 14.71CO2, Stratosphereic temperature 10 7.43 Water vapor, Lower to mid-

level tropospheric moisture

2 14.37CO2, Stratosphereic temperature 11 7.02 Water vapor, mid-level

tropospheric moisture

3 14.06CO2, Upper-tropospheric temperature 12 6.51 Water vapor, upper-level

tropospheric moisture

4 13.96CO2, Mid-tropospheric temperature 13 4.57 CO2, Lower-level

tropospheric temperature

5 13.37CO2, Lower-tropospheric temperature 14 4.52 CO2, Mid-level


6 12.66 Water vapor, lower-tropospheric moisture 15 4.45 CO2, Upper-level


7 12.02Water 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

Resolution = 10 km at nadir

Lon

gwav

eM

idw

ave

Midw

ave

Shortw

ave




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.


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 vaporchannel 7 – window channelNote the location and shapes of the weighting functions

Weighting Functions for 2 points: wet and dryCO2 channels 1 - 5

Weighting Functions for 2 points: wet and dryH2O channels 10 -12

10-12


Example of all channels for the GOES-12 Sounder


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



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



Retrieval of profiles from the GOES Sounder by NESDIS (physically based)

• 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).


Radiance at Satellite = (surface blackbody radiance*surface emissivity*atmospheric transmittance)

+ atmospheric contribution from many layers.


GOES Sounder ProductsDerived Product Imagery (DPI)

Lifted IndexCAPE

Convective Inhibition

Total Precipitable Water

Surface Skin Temperature

Water vapor winds



• 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.

GOES sounder data and products

http://cimss.ssec.wisc.edu/goes/realtime/realtime.html http://www.orbit.nesdis.noaa.gov/smcd/opdb/goes/sdpi/html/sdpiimgnewt.html

http://cimss.ssec.wisc.edu/goes/realtime/realtime.html



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




Lifted Index

negative values – unstable air masspositive values – stable 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

http://www.orbit.nesdis.noaa.gov/smcd/opdb/goes/sdpi/html/sdpiimgnewt.html


Skin Temperature


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




Cloud top pressure


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



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.


Microwave Spectrum and Channel locations

Region for Temperature Sounding between 50 and 60 GHz


AMSU-A AMSU-BChannel

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: 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.

Source: Kidder and Vonder Haar (1995)

Stan Kidder’s AMSU web page at CIRA: http://amsu.cira.colostate.edu/

http://amsu.cira.colostate.edu/










SSM/TFrequency

MHzPolarization

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)

TPW from AMSU and SSMI

3 channels centered at 183 GHzfor moisture sounding / TPW

23GHz for TPW

Weighting functions for AMSU – Bcourtesy of Tom Greenwald

Stan Kidder’s AMSU web page at CIRA: http://amsu.cira.colostate.edu/ Note: AMSU-B channels 1-5 are often referred to as AMSU channels 16-20.

C3 183.3 +/- 1R GHz

C4 183.3 +/- 3R GHz

C5 183.3 +/- 7R GHz











AMSU Products

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

TPW

CLW

Rain rate

Snow cover

Ice cover



AMSU Products

• Microwave Surface and Precipitation Products System (MSPPS)

http://www.orbit.nesdis.noaa.gov/corp/scsb/mspps/main.html

• CIRA’s AMSU Website



ReferencesCDs produced by the COMET program (see meted.ucar.edu)

Polar Satellite Products for the Operational Forecaster POES Introduction and BackgroundPOES Microwave ApplicationsAn Introduction to POES Data and Products

Satellite Meteorology: Remote Sensing Using the New GOES ImagerSatellite 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


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


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

Documents

Meteorological Sounders