Atmospheric Infrared Sounder (AIRS)
Product Details
RESEARCH PRODUCT DETAILS
AIRS Profiles
AIRS Level-2 products can give near-rawinsonde-quality retrievals of atmospheric temperature and moisture. Currently, this is a research product in development for transition to SPoRT's Huntsville NWS WFO partner for use in detecting mid-morning pre-convective atmospheric conditions. The AIRS profiles give an asynoptic, three-dimensional look at the atmosphere that is not available through point observations such as rawinsondes or aircraft data, so they can be of used in finding the location of fronts or other changes in atmospheric stability. The real-time data is a tool that compares the AIRS soundings with NAM forecast and rawinsonde observations to help aid the researchers and forecasters in determining the best way to use the AIRS profiles for operational weather forecasting applications.
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Cloud Top Pressure
The CO2 slicing technique is being utilized to produce a cloud top pressure product from AIRS measurements. The original technique (Smith and Platt 1978) has been adapted to utilize the hyperspectral nature of the AIRS instrument, as described in McCarty and Jedlovec 2006. The increased spectral resolution of the instrument allows for a more detailed investigation of the vertical structure of the atmosphere. This trait is utilized to produce more accurate cloud height assessments.
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Effective Cloud Fraction
The effective cloud fraction (ECF) product is a by-product of the CO2 slicing technique. After retrieving the cloud top pressure, the ECF, which is the product of the cloud emissivity and physical cloud fraction, can be calculated. Ranging from 0 to 100 percent, it is representative of the fractional contribution of the cloud to the measured radiances.
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Percent Cloud Free Channels
The CO2 sorting technique is implemented to provide the percentage of bands within the 15 µm CO2 absorption continuum which are uncontaminated by clouds. This methodology, adapted from Holz et al. 2006 and described in McCarty et al. 2007, is used for the purpose of determining the channels in an AIRS instantaneous field of view which can be assimilated in an analysis system. The technique is used to determine those channels which are unaffected by clouds. They can then be assimilated without the need to characterize any cloud properties in the radiative transfer within the assimilation system.
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Carbon Dioxide
The AIRS Carbon Dioxide imagery uses the 13.3 µm absorption channel to approximate tropospheric temperatures. It has an approximately 15-km resolution at nadir.
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Infrared
The AIRS longwave infrared imagery uses the 10.7 µm window channel and is nearly identical to the infrared imagery produced by GOES and MODIS, but at a lower resolution (approximately 15 km at nadir). This image is for detection of cold cloud tops.
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Shortwave Infrared
The AIRS shortwave infrared imagery uses the 3.9 µm wavelength and is available at 15 km resolution at nadir. It depicts both reflected and emitted atmospheric and surface emission.
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Visible
The AIRS Visible imagery is produced at a single band of 10.65 µm. Obviously, this is available only during the daytime hours. This typically provides one overpass per day at an approximate resolution of 15 km at nadir.
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Water Vapor
As with the visible imagery, the water vapor imagery uses a single band at 6.5 µm that is sensitive to the amount of water vapor in the atmosphere. The water vapor imagery has a resolution of 15 km at nadir and is used to depict changing upper level water vapor patterns.
