CIRA & NOAA/NESDIS/RAMM Meteorological Sounders Dr. Bernie Connell CIRA/NOAA-RAMMT March 2005

CIRA & NOAA/NESDIS/RAMM Outline GOES Sounder Types of soundings Channels Absorption regions (CO 2, H 2 O, O 3 ) 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 Satellite Meteorology: Using the GOES Sounder Absorption regions for CO 2, H 2 O, and O 3

GOES Sounder Channels Channel Center Wavelength (um) Comment (spectral region, application) Channel Center Wavelength (um) Comment (spectral region, application) CO 2, Stratosphereic temperature Water vapor, Lower to mid- level tropospheric moisture CO 2, Stratosphereic temperature Water vapor, mid-level tropospheric moisture CO 2, Upper-tropospheric temperature Water vapor, upper-level tropospheric moisture CO 2, Mid-tropospheric temperature CO2, Lower-level tropospheric temperature CO 2, Lower-tropospheric temperature CO2, Mid-level tropospheric temperature Water vapor, lower- tropospheric moisture CO2, Upper-level tropospheric temperature Water vapor, “dirty” (moisture contaminated) window CO2, Boundary-layer temperature Window, cloud-top and surface temperature Window, cloud top and surface temperature Ozone, stratospheric ozone Window, cloud top and surface temperature Visible 0.94 Visible window, cloud top and surface features Resolution = 10 km at nadir Longwave Midwave Shortwave Satellite Meteorology: Using the GOES Sounder

CIRA & NOAA/NESDIS/RAMM Satellite Meteorology: Using the GOES Sounder 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 Satellite Meteorology: Using the GOES Sounder um um um 4 – um um um 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

Weighting Functions for 2 points: wet and dry CO2 channels 1 - 5

Weighting Functions for 2 points: wet and dry H2O channels

CIRA & NOAA/NESDIS/RAMM 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) 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 Radiance at Satellite = (surface blackbody radiance*surface emissivity*atmospheric transmittance) + atmospheric contribution from many layers.

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. GOES sounder data and products

Total Precipitable Water

CIRA & NOAA/NESDIS/RAMM 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 GOES sounder data and products

Lifted Index negative values – unstable air masspositive values – stable air mass

CIRA & NOAA/NESDIS/RAMM 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. 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 CO 2 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 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 R89.0R 231.4R157.0R 350.3R /- 1R 452.8R /- 3R 553.6R /- 7R 654.4R 754.9R 855.5R 957.2R /-.217R / /-.048R / /-.022R / /-.010R / /-.0045R R 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:

CIRA & NOAA/NESDIS/RAMM SSM/T Frequency MHz Polarization 50.5H 53.2H 54.35H 54.9H 58.4V V 59.4V 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 GHz for moisture sounding / TPW 23GHz for TPW

Weighting functions for AMSU – B courtesy of Tom Greenwald Stan Kidder’s AMSU web page at CIRA: Note: AMSU-B channels 1-5 are often referred to as AMSU channels C /- 1R GHz C /- 3R GHz C /- 7R GHz

CIRA & NOAA/NESDIS/RAMM AMSU Products Total Precipitable Water (TPW) Cloud Liquid Water (CLW) Rain rate Snow and Ice cover TPW CLW Rain rate Snow cover Ice cover

CIRA & NOAA/NESDIS/RAMM AMSU Products Microwave Surface and Precipitation Products System (MSPPS) CIRA’s AMSU Website

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: NOAA/NESDIS Office of Research and Applications (ORA) Operational Products Development Branch (OPDB) Derived GOES sounder products: The Cooperative Institute for Meteorological Satellite Studies Realtime GOES Page NOAA/NESDIS/ORA/Hydrology Team/Microwave Remote Sensing Project Microwave Surface and Precipitation Products System (MSPPS)

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 CIMSS Stan Kidder’s AMSU webpage at CIRA: Microwave Surface and Precipitation Products System (MSPPS)