The NPOESS Airborne Sounding Testbed Interferometer—Remotely Sensed Surface and Atmospheric Conditions during CLAMS

Abstract

During the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS), the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder TestbedInterferometer (NAST-I), flying aboard the high-altitude Proteus aircraft, observed the spatial distribution of infrared radiance across the 650-2700 cm Ϫ1 (3.7-15.4 m) spectral region with a spectral resolution of 0.25 cm Ϫ1 . NAST-I scans cross track with a moderate spatial resolution (a linear ground resolution equal to 13% of the aircraft altitude at nadir). The broad spectral coverage and high spectral resolution of this instrument provides abundant information about the surface and three-dimensional state of the atmosphere. In this paper, the NAST-I measurements and geophysical product retrieval methodology employed for CLAMS are described. Example results of surface properties and atmospheric temperature, water vapor, ozone, and carbon monoxide distributions are provided. The CLAMS NAST-I geophysical dataset is available for use by the scientific community.

Retrieval validation during the European Aqua Thermodynamic Experiment

“…The mean difference profile is within ±8%. The statistical results are within the requirements of this type of sounder (Smith et al, 2005a;Susskind et al, 2006). These small differences can be explained by the different vertical resolutions achieved by the different retrieval algorithms, which are also manifested in the profile validation over Potenza (Figure 1).…”

“…A large difference between Raman lidar and other profiles in that region is due to the difference in vertical and horizontal resolution; the Raman lidar has a higher signal-to-noise ratio and the vertical resolution is about 15 to 30 m. The AIRS water vapour mixing ratio and RH profiles retrieved with A-T and N-T algorithms are in good agreement, i.e. within instrument sounding goals (Smith et al, 2005a;Susskind et al, 2006). In the region near 9 km, the radiosonde indicates a lower humidity than that indicated by all other sensors.…”

“…These instruments provide experimental observations needed for finalizing specifications, testing proposed designs, and developing data-processing algorithms for the Cross-track Infrared Sounder (CrIS), which will fly on NPOESS satellites. Detailed descriptions of NAST-I instrumentation, data processing methodologies, and data products can be found elsewhere (Cousins and Smith, 1997;Smith et al, 1999;Larar et al, 2002;Zhou et al, 2002;Smith et al, 2005a). Selected AIRS radiance datasets have been put through testing using the NAST-Team retrieval algorithm since AIRS data first became available in July 2002 (Smith et al, 2004).…”

Case-study of a principal-component-based radiative transfer forward model and retrieval algorithm using EAQUATE data

“…(9) The new physical inversion algorithm has been successfully applied to the NAST-I instrument, which is a Fourier Transform infrared spectrometer with a spectral resolution of 0.25 cm −1 and a continuous spectral coverage from 645 to 2700 cm −1 (Cousins and Smith, 1997;Smith et al, 1999Smith et al, , 2005. It would be very computationally intensive (or impractical) to include all 8632 NAST-I channels in a conventional physical inversion algorithm.…”

Surface emissivity effects on thermodynamic retrieval of IR spectral radiance

“…The scope of this letter is to illustrate the sensitivity of the skin temperature and lower tropospheric water vapor retrieval accuracy to the surface emissivity from an infrared nadirobserving Fourier transform spectrometer (such as NAST-I, IASI, and CrIS). Measurements made by NAST-I during the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) field experiment 9 during the summer of 2001 are used to demonstrate the retrieval methodology and surface emissivity effects on surface skin temperature and lower tropospheric moisture retrievals in conjunction with some validations.…”