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Hyperspectral data from satellite-based sounders will have an impact on a wide variety of atmospheric products.
A technologically advanced focal plane array provides a 128 x 128 field of view (fov) imaging capability. Each of the pixels yields an interferogram, which can be transformed into spectra across the infrared measurement range. The high spatial (4 km) resolution provides more cloud-free measurements.
The high spectral resolution provides information about individual absorption lines. Current operational sounders measure across broad areas of the spectrum, losing the detail needed to obtain important details about the vertical profiles of atmospheric gasses.
The GIFTS makes high spectral resolution measurements across two regions of the Infrared portion of the electromagnetic spectrum. This coverage includes transparent (window) regions of the atmosphere and regions where constituent gasses are absorbing and emitting radiation. Temperature and moisture profiles can be calculated by applying the high spectral resolution measurements in absorption bands of CO2 and H2O. Created by combining multispectral observations, derived products have many applications ranging from fire and aerosol detection to the characterization of cloud properties to measurements of surface temperature over the land and sea.
The high spectral resolution yields many more individual observations than current broadband instruments. The emission characteristics at high spectral resolution also yield information from a thinner layer of the atmosphere, resulting in increased vertical resolution of the products.
The great increase in the number of measurements plus the increased vertical resolution result in significantly improved accuracy of the vertical profiles of temperature and moisture, and their derived products, similar in information content to a radiosonde. This improved accuracy will greatly improve short term nowcasts and forecasts of sub-synoptic scale events. With these measurements available every 15 minutes, the result is a true mesoscale observation system from space.
GIFTS temperature and moisture profiles will have detailed vertical resolution. Combined with the 4 km spatial resolution and the 15 minute temporal resolution, GIFTS can monitor the evolving atmosphere in detail never before captured, allowing for improved nowcasts and forecasts.
Temperature and moisture profiles from high spectral resolution measurements are interpolated to atmospheric levels. From the time rate of change of water vapor mixing ratio at a given gridpoint, motion vectors will yield accurate winds with accurate height assignments. Consequently, this approach allows wind information at multiple levels and all gridpoints instead of having winds at one or two levels and located only where tracers are found. More accurate winds greatly increases our knowledge of the atmospheric dynamics.
The SSEC Scanning-HIS and the NASA Langley NAST-I aircraft instruments have served as prototypes for GIFTS. These prototypes demonstrated significant improvements in accuracy and facilitated the development of high spectral resolution datasets.
This animation of NAST-I retrieved water vapor information depicts the detail available from high spectral resolution measurements. The ER-2 aircraft flew a racetrack flight pattern to cover the same region of the Earth and its atmosphere every 35 minutes. The animation was created from these scans. Southwesterly flow regimes are present at 800 and 700mb will easterlies are present at 500 and 200mb. Significant mesoscale detail is visible in the water vapor features.
A numerical model generated observation of water vapor as will be observed within a 3 x 3 array of GIFTS “cubes” (i.e., field of regard). The animation was generated for a region along the Louisiana/Texas Gulf coast for January 7, 2002. The model generated temperature and moisture fields were converted to radiance observations as would by the GIFTS at any instance of time. Moisture profiles were then retrieved from the radiance fields. Shown is a ten minute interval animation of the moisture “observed” by the GIFTS over a three hour period. The moisture flux can be used to identify where storms will develop and the winds inferred from the moisture flux can be used to obtain predictions of the storm motion.
GIFTS measurements will greatly improve weather nowcasting and forecasting, as well as provide more detailed information for scientific studies. Its applications will save lives with improved forecasts of severe weather, including severe thunderstorms, hurricanes and mid latitude cyclones. Improved forecasts will greatly benefit the economy by inspiring better agricultural planning and industrial practices. GIFTS will also benefit climate research with improved detection of trace gases, including greenhouse gasses, and aerosols.