The importance of aerosol absorption in satellite sensor vicarious calibration and/or satellite m... more The importance of aerosol absorption in satellite sensor vicarious calibration and/or satellite measurement of physical parameters is reiterated in a sensitivity study performed using a radiative transfer model, with field-measured data as input. Broadband shortwave surface fluxes need to be measured according to new protocols, described herein, to infer atmospheric absorption to improve calibration accuracy to within the plusmn2% stated
: Almost perfect operation of Skylab Experiment S082A resulted in the return of 1032 extreme ultr... more : Almost perfect operation of Skylab Experiment S082A resulted in the return of 1032 extreme ultraviolet solar spectroheliograms, providing an enormous wealth of new information about the sun in the wavelength range 171 to 630. The present User's Guide was written for guest investigators and other ATM experimenters who will collaborate in interpreting the returned data. The first section is devoted to a brief overview of the Apollo Telescope Mount (ATM) as a whole and the major areas in which the data have been found to be most important. There follows a detailed description of the spectroheliograph and the special Schumann film it utilized. The complementary relationshop to the 5 other major instruments on ATM is explained. A large portion of the Guide is devoted to a description of the observations, the data catalogs and documentation, and listings of important events recorded during almost 9 months of nearly continuous operation of Skylab, beginning in May 1973. The main part...
Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research III, 1999
ABSTRACT A new high spectral resolution (0.25 cm(superscript -1)) and high spatial resolution (2.... more ABSTRACT A new high spectral resolution (0.25 cm(superscript -1)) and high spatial resolution (2.6 km) scanning (46 km swath width) Fourier Transform Spectrometer (FTS) has been built for flight on NASA high altitude (approximately 20 km) aircraft. The instrument, called the NPOESS Aircraft Sounding Testbed- Interferometer (NAST-I), has been flown during several field campaigns to provide experimental observations needed to finalize specifications and to test proposed designs for future satellite instruments; specifically, the Cross-track Infrared Sounder (CrIS) to fly on the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NAST-I provides new and exciting observations of mesoscale structure of the atmosphere, including the fine scale thermodynamic characteristics of hurricanes. The NAST-I instrument is described, its excellent spectral and radiometric performance is demonstrated, and surface and atmospheric remote sensing results obtained during airborne measurement campaigns are presented.
Quarterly Journal of the Royal Meteorological Society, 2007
The objective of the paper is to apply a novel radiative transfer model and a physical retrieval ... more The objective of the paper is to apply a novel radiative transfer model and a physical retrieval algorithm to hyperspectral data taken during the European Aqua Atmospheric Thermodynamics Experiment (EAQUATE) campaign. A principal-component-based radiative transfer model (PCRTM) is used to calculate projection coefficients of the radiance spectrum onto a set of predefined empirical orthogonal functions (EOFs) and associated derivatives with respect to the state vector. Instead of fitting channel radiances, the physical retrieval algorithm iteratively fits the principal component (PC) scores or the EOF projection coefficients of the observed radiance spectrum using the PCRTM as its forward model. Since the EOFs are orthonormal to each other, only a few PC scores are needed to capture the information content of the radiance spectrum, therefore reducing the computational time needed for running both the forward model and the inversion. This paper demonstrates the application of such a physical algorithm for retrieving atmospheric temperature, moisture and ozone profiles, and surface properties such as surface skin temperature and surface emissivity. The results have been compared with those obtained with a NAST-I channel-based physical retrieval algorithm and with those obtained from collocated radiosonde and LIDAR measurements.
Quarterly Journal of the Royal Meteorological Society, 2007
Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sen... more Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sensors aboard Earth observing satellites are critical to weather prediction and scientific research. The retrieval algorithms and retrieved parameters from satellite sounders must be validated to demonstrate the capability and accuracy of both observation and data processing systems. The European Aqua Thermodynamic Experiment (EAQUATE) was conducted not only for validation of the Atmospheric InfraRed Sounder on the Aqua satellite, but also for assessment of validation systems of both ground-based and aircraft-based instruments that will be used for other satellite systems, such as the Infrared Atmospheric Sounding Interferometer on the European MetOp satellite, the Cross-track Infrared Sounder from the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project and the continuing series of NPOESS satellites. Detailed intercomparisons were conducted and presented using different retrieval methodologies: measurements from airborne ultraspectral Fourier transform spectrometers, aircraft in situ instruments, dedicated dropsondes and radiosondes, ground-based Raman lidar, as well as the European Centre for Medium-range Weather Forecasting modelled thermal structures. The results of this study not only illustrate the quality of the measurements and retrieval products, but also demonstrate the capability of the validation systems put in place to validate current and future hyperspectral sounding instruments and their scientific products.
A physical inversion scheme has been developed dealing with cloudy as well as cloud-free radiance... more A physical inversion scheme has been developed dealing with cloudy as well as cloud-free radiance observed with ultraspectral infrared sounders to simultaneously retrieve surface, atmospheric thermodynamic, and cloud microphysical parameters. A fast radiative transfer model, which applies to the clouded atmosphere, is used for atmospheric profile and cloud parameter retrieval. A one-dimensional (1D) variational multivariable inversion solution is used to improve an iterative background state defined by an eigenvector-regression retrieval. The solution is iterated in order to account for nonlinearity in the 1D variational solution. It is shown that relatively accurate temperature and moisture retrievals can be achieved below optically thin clouds. For optically thick clouds, accurate temperature and moisture profiles down to cloud-top level are obtained. For both optically thin and thick cloud situations, the cloud-top height can be retrieved with relatively high accuracy (i.e., erro...
Atmospheric thermodynamic parameters, such as atmospheric temperature and moisture profiles, clou... more Atmospheric thermodynamic parameters, such as atmospheric temperature and moisture profiles, cloud optical/microphysical properties, and surface properties are basic meteorological variables for weather forecasting. In addition, they are critical parameters in tropospheric chemistry studies. A physical, geophysical parameter retrieval scheme dealing with cloudy and cloud-free radiances observed with satellite ultraspectral infrared sounders has been developed to determine simultaneously surface, atmospheric thermodynamic, and cloud microphysical parameters. A one-dimensional variational (1-D Var.) multivariable inverse solution of the radiative transfer equation is used to iteratively improve a background state defined by eigenvector regression. This algorithm has been applied to data from the Infrared Atmospheric Sounding Interferometer (IASI) on the EUMETSAT Metop-A satellite. The IASI retrieved parameters presented herein are from radiance data gathered during the Joint Airborne IASI Validation Experiment (JAIVEx). JAIVEx provided intensive aircraft observations obtained from airborne Fourier Transform Spectrometer (FTS) systems, such as the NPOESS Airborne Sounder Testbed -Interferometer (NAST-I), in-situ measurements, and dedicated dropsonde and radiosonde measurements for the validation of the IASI products. Here, IASI atmospheric profile retrievals are compared with those obtained from dedicated dropsondes, radiosondes, and the airborne FTS system. The
The National Polar-Orbiting Operational Environmental Satellite System ͑NPOESS͒ Airborne Sounder ... more The National Polar-Orbiting Operational Environmental Satellite System ͑NPOESS͒ Airborne Sounder Testbed ͑NAST͒ consists of two passive collocated cross-track scanning instruments, an infrared interferometer ͑NAST-I͒ and a microwave radiometer ͑NAST-M͒, that fly onboard high-altitude aircraft such as the NASA ER-2 at an altitude near 20 km. NAST-I provides relatively high spectral resolution ͑0.25-cm Ϫ1 ͒ measurements in the 645-2700-cm Ϫ1 spectral region with moderate spatial resolution ͑a linear resolution equal to 13% of the aircraft altitude at nadir͒ cross-track scanning. We report the methodology for retrieval of atmospheric temperature and composition profiles from NAST-I radiance spectra. The profiles were determined by use of a statistical eigenvector regression algorithm and improved, as needed, by use of a nonlinear physical retrieval algorithm. Several field campaigns conducted under varied meteorological conditions have provided the data needed to verify the accuracy of the spectral radiance, the retrieval algorithm, and the scanning capabilities of this instrumentation. Retrieval examples are presented to demonstrate the ability to reveal fine-scale horizontal features with relatively high vertical resolution.
The airborne NPOESS Aircraft Sounding Test-bed Interferometer (NAST-I) has flown on numerous flig... more The airborne NPOESS Aircraft Sounding Test-bed Interferometer (NAST-I) has flown on numerous flights under the Aqua satellite in order to validate AIRS radiance measurements and profile retrievals. The NAST-I is an excellent AIRS airborne validation tool since it possesses relatively high spectral and spatial resolution as well as relatively low radiance measurement noise, especially after the data are spatially averaged to the footprint size of the AIRS sensor. The results of these airborne missions have shown that the AIRS calibration validates well against airborne interferometer radiance measurements 1 . Here, it is shown that the retrievals obtained using the same retrieval algorithm are in general agreement, although the airborne NAST-I result possesses higher vertical resolution as a consequence of it's higher spectral resolution and lower "effective" radiance noise level. The "effective" radiance noise level is a function of the single spectral sample radiance measurement noise, the number of spectral channels used for the retrieval, and the number of spatial samples averaged to produce the final profile result. For the NAST-I aircraft instrument, the effective radiance noise level is extremely small, particularly after reducing the horizontal linear resolution to that of the satellite AIRS instrument (i.e., ~14 km for AIRS as opposed to ~2 km for NAST-I), and as a result its relatively large spectral range and high spectral resolution (i.e., NAST-I possess nearly four times the number of spectral channels as does the AIRS). It is shown here that spatial averaging of the AIRS data, which decreases the noise level of the radiances used for the retrieval, improves the vertical resolution of the profile results.
The Workshop on Polarized Solid Targets, the 6th of a series which started in 1978, has been atte... more The Workshop on Polarized Solid Targets, the 6th of a series which started in 1978, has been attended by 47 participants, who presented 32 contributions, as many as ever. The presence of several young, “new” colleagues has been particularly gratifying and has contributed to create an atmosphere of lively and fruitful discussions. Furthermore, for the first time in many years we had the pleasure to meet a good number of colleagues from the Soviet Union, and we had the opportunity to learn and discuss about much interesting work which had been, alas, largely ignored in the West. It is to hope that the contacts which have been established at this Workshop will be actively pursued, they shall certainly bear interesting fruits.
India and the United States of America (U.S.A.) held a joint conference from June 21-25, 2004 in ... more India and the United States of America (U.S.A.) held a joint conference from June 21-25, 2004 in Bangalore, India to strengthen and expand cooperation in the area of space science, applications, and commerce. Following the recommendations in the joint vision statement released at the end of the conference, the National Oceanic and Atmospheric Administration (NOAA) and the Indian Space and
The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on Oc... more The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on October 19, 2006. The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25/cm and a spectral coverage from 645 to 2760/cm. Ultraspectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations during the JAIVEx are obtained and presented. These retrievals are further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed Interferom...
A state-of-the-art IR-only retrieval algorithm has been developed with an all-season-global EOF P... more A state-of-the-art IR-only retrieval algorithm has been developed with an all-season-global EOF Physical Regression and followed by 1-D Var. Physical Iterative Retrieval for IASI, AIRS, and NAST-I. The benefits of this retrieval are to produce atmospheric structure with a single FOV horizontal resolution (approx. 15 km for IASI and AIRS), accurate profiles above the cloud (at least) or down to the surface, surface parameters, and/or cloud microphysical parameters. Initial case study and validation indicates that surface, cloud, and atmospheric structure (include TBL) are well captured by IASI and AIRS measurements. Coincident dropsondes during the IASI and AIRS overpasses are used to validate atmospheric conditions, and accurate retrievals are obtained with an expected vertical resolution. JAIVEx has provided the data needed to validate the retrieval algorithm and its products which allows us to assess the instrument ability and/or performance. Retrievals with global coverage are un...
The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for... more The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite, but also included a strong component focusing on validation of the Atmospheric InfraRed Sounder (AIRS) aboard the AQUA satellite. The cross validation of IASI and AIRS is important for the joint use of their data in the global Numerical Weather Prediction process. Initial inter-comparisons of geophysical products have been conducted from different aspects, such as using different measurements from airborne ultraspectral Fourier transform spectrometers (specifically, the NPOESS Airborne Sounder Testbed Interferometer (NAST-I) and the Scanning-High resolution Interferometer Sounder (S-HIS) aboard the NASA WB-57 aircraft), UK Facility for Airborne Atmospheric Measurements (FAAM) BAe146-301 aircraft insitu instruments, dedicated dropsondes, radiosondes, and ground based Raman Lidar. An overview of ...
The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on Oc... more The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on October 19, 2006. The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25 cm(exp -1) and a spectral coverage from 645 to 2760 cm(exp -1). Ultra-spectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations are obtained and presented. These retrievals are further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed - Interfero...
The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for... more The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly forvalidation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25 cm-1 and aspectral coverage from 645 to 2760 cm-1. Ultra-spectral resolution infrared spectral radiance obtained from nearnadir observations provide atmospheric, surface, and cloud property information. An advanced retrievalalgorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloudparameter retrieval. This physical inversion scheme has been developed, dealing with cloudy as well as cloud-free radiance observed with ultraspectral infrared sounders, to simultaneously retrieve surface, atmosphericthermodynamic, and cloud microphysical parameters. A fast radiative transfer model, which applies to thecloud-free and/or clouded atmosphere, is used for atmospheric profile and cloud parameter retrieval. A one-dimensional (1-d) variational multi...
The Infrared Atmospheric Sounding Interferometer (IASI) is a modern satellite sensor with 8461 ch... more The Infrared Atmospheric Sounding Interferometer (IASI) is a modern satellite sensor with 8461 channels and a spectral resolution of 0.25 wavenumber. It provides a wealth of information on atmospheric and surface properties. Due to the high spectral resolution, a large number of Radiative Transfer (RT) calculations through the inhomogeneous atmosphere are needed. Usually, only subsets of channels are used to perform physical inversions for atmospheric profiles. This paper presents a novel radiative transfer model based on principal component analysis. The Principal Componentbased Radiative Transfer Model (PCRTM) predicts PC scores and associated derivatives with respect to various atmospheric and surface properties in PC space directly. Usually, less than 200 PCs are needed to regenerate the original radiance spectrum with accuracy better than instrument noise level. Therefore, the dimension of the spectrum is reduced by an order of magnitude for hyper spectral sensors with thousand...
The real-time operational requirements for SARCOM translation into a high speed image data handle... more The real-time operational requirements for SARCOM translation into a high speed image data handler and processor to achieve the desired compression ratios and the selection of a suitable image data compression technique with as low as possible fidelity (information) losses and which can be implemented in an algorithm placing a relatively low arithmetic load on the system are described.
High-resolution infrared radiance spectra obtained from near nadir observations provide atmospher... more High-resolution infrared radiance spectra obtained from near nadir observations provide atmospheric, surface, and cloud property information. A fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. The retrieval algorithm is presented along with its application to recent field experiment data from the NPOESS Airborne Sounder Testbed-Interferometer (NAST-I). The retrieval accuracy dependence on cloud properties is discussed. It is shown that relatively accurate temperature and moisture retrievals can be achieved below optically thin clouds. For optically thick clouds, accurate temperature and moisture profiles down to cloud top level are obtained. For both optically thin and thick cloud situations, the cloud top height can be retrieved with an accuracy of approximately 1.0 km. Preliminary NAST-I retrieval results from the recent Atlantic-THORPEX Regional Campaign (ATReC) are presented and compared with coincident observations obtained from dropsondes and the nadir-pointing Cloud Physics Lidar (CPL).
The importance of aerosol absorption in satellite sensor vicarious calibration and/or satellite m... more The importance of aerosol absorption in satellite sensor vicarious calibration and/or satellite measurement of physical parameters is reiterated in a sensitivity study performed using a radiative transfer model, with field-measured data as input. Broadband shortwave surface fluxes need to be measured according to new protocols, described herein, to infer atmospheric absorption to improve calibration accuracy to within the plusmn2% stated
: Almost perfect operation of Skylab Experiment S082A resulted in the return of 1032 extreme ultr... more : Almost perfect operation of Skylab Experiment S082A resulted in the return of 1032 extreme ultraviolet solar spectroheliograms, providing an enormous wealth of new information about the sun in the wavelength range 171 to 630. The present User's Guide was written for guest investigators and other ATM experimenters who will collaborate in interpreting the returned data. The first section is devoted to a brief overview of the Apollo Telescope Mount (ATM) as a whole and the major areas in which the data have been found to be most important. There follows a detailed description of the spectroheliograph and the special Schumann film it utilized. The complementary relationshop to the 5 other major instruments on ATM is explained. A large portion of the Guide is devoted to a description of the observations, the data catalogs and documentation, and listings of important events recorded during almost 9 months of nearly continuous operation of Skylab, beginning in May 1973. The main part...
Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research III, 1999
ABSTRACT A new high spectral resolution (0.25 cm(superscript -1)) and high spatial resolution (2.... more ABSTRACT A new high spectral resolution (0.25 cm(superscript -1)) and high spatial resolution (2.6 km) scanning (46 km swath width) Fourier Transform Spectrometer (FTS) has been built for flight on NASA high altitude (approximately 20 km) aircraft. The instrument, called the NPOESS Aircraft Sounding Testbed- Interferometer (NAST-I), has been flown during several field campaigns to provide experimental observations needed to finalize specifications and to test proposed designs for future satellite instruments; specifically, the Cross-track Infrared Sounder (CrIS) to fly on the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NAST-I provides new and exciting observations of mesoscale structure of the atmosphere, including the fine scale thermodynamic characteristics of hurricanes. The NAST-I instrument is described, its excellent spectral and radiometric performance is demonstrated, and surface and atmospheric remote sensing results obtained during airborne measurement campaigns are presented.
Quarterly Journal of the Royal Meteorological Society, 2007
The objective of the paper is to apply a novel radiative transfer model and a physical retrieval ... more The objective of the paper is to apply a novel radiative transfer model and a physical retrieval algorithm to hyperspectral data taken during the European Aqua Atmospheric Thermodynamics Experiment (EAQUATE) campaign. A principal-component-based radiative transfer model (PCRTM) is used to calculate projection coefficients of the radiance spectrum onto a set of predefined empirical orthogonal functions (EOFs) and associated derivatives with respect to the state vector. Instead of fitting channel radiances, the physical retrieval algorithm iteratively fits the principal component (PC) scores or the EOF projection coefficients of the observed radiance spectrum using the PCRTM as its forward model. Since the EOFs are orthonormal to each other, only a few PC scores are needed to capture the information content of the radiance spectrum, therefore reducing the computational time needed for running both the forward model and the inversion. This paper demonstrates the application of such a physical algorithm for retrieving atmospheric temperature, moisture and ozone profiles, and surface properties such as surface skin temperature and surface emissivity. The results have been compared with those obtained with a NAST-I channel-based physical retrieval algorithm and with those obtained from collocated radiosonde and LIDAR measurements.
Quarterly Journal of the Royal Meteorological Society, 2007
Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sen... more Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sensors aboard Earth observing satellites are critical to weather prediction and scientific research. The retrieval algorithms and retrieved parameters from satellite sounders must be validated to demonstrate the capability and accuracy of both observation and data processing systems. The European Aqua Thermodynamic Experiment (EAQUATE) was conducted not only for validation of the Atmospheric InfraRed Sounder on the Aqua satellite, but also for assessment of validation systems of both ground-based and aircraft-based instruments that will be used for other satellite systems, such as the Infrared Atmospheric Sounding Interferometer on the European MetOp satellite, the Cross-track Infrared Sounder from the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project and the continuing series of NPOESS satellites. Detailed intercomparisons were conducted and presented using different retrieval methodologies: measurements from airborne ultraspectral Fourier transform spectrometers, aircraft in situ instruments, dedicated dropsondes and radiosondes, ground-based Raman lidar, as well as the European Centre for Medium-range Weather Forecasting modelled thermal structures. The results of this study not only illustrate the quality of the measurements and retrieval products, but also demonstrate the capability of the validation systems put in place to validate current and future hyperspectral sounding instruments and their scientific products.
A physical inversion scheme has been developed dealing with cloudy as well as cloud-free radiance... more A physical inversion scheme has been developed dealing with cloudy as well as cloud-free radiance observed with ultraspectral infrared sounders to simultaneously retrieve surface, atmospheric thermodynamic, and cloud microphysical parameters. A fast radiative transfer model, which applies to the clouded atmosphere, is used for atmospheric profile and cloud parameter retrieval. A one-dimensional (1D) variational multivariable inversion solution is used to improve an iterative background state defined by an eigenvector-regression retrieval. The solution is iterated in order to account for nonlinearity in the 1D variational solution. It is shown that relatively accurate temperature and moisture retrievals can be achieved below optically thin clouds. For optically thick clouds, accurate temperature and moisture profiles down to cloud-top level are obtained. For both optically thin and thick cloud situations, the cloud-top height can be retrieved with relatively high accuracy (i.e., erro...
Atmospheric thermodynamic parameters, such as atmospheric temperature and moisture profiles, clou... more Atmospheric thermodynamic parameters, such as atmospheric temperature and moisture profiles, cloud optical/microphysical properties, and surface properties are basic meteorological variables for weather forecasting. In addition, they are critical parameters in tropospheric chemistry studies. A physical, geophysical parameter retrieval scheme dealing with cloudy and cloud-free radiances observed with satellite ultraspectral infrared sounders has been developed to determine simultaneously surface, atmospheric thermodynamic, and cloud microphysical parameters. A one-dimensional variational (1-D Var.) multivariable inverse solution of the radiative transfer equation is used to iteratively improve a background state defined by eigenvector regression. This algorithm has been applied to data from the Infrared Atmospheric Sounding Interferometer (IASI) on the EUMETSAT Metop-A satellite. The IASI retrieved parameters presented herein are from radiance data gathered during the Joint Airborne IASI Validation Experiment (JAIVEx). JAIVEx provided intensive aircraft observations obtained from airborne Fourier Transform Spectrometer (FTS) systems, such as the NPOESS Airborne Sounder Testbed -Interferometer (NAST-I), in-situ measurements, and dedicated dropsonde and radiosonde measurements for the validation of the IASI products. Here, IASI atmospheric profile retrievals are compared with those obtained from dedicated dropsondes, radiosondes, and the airborne FTS system. The
The National Polar-Orbiting Operational Environmental Satellite System ͑NPOESS͒ Airborne Sounder ... more The National Polar-Orbiting Operational Environmental Satellite System ͑NPOESS͒ Airborne Sounder Testbed ͑NAST͒ consists of two passive collocated cross-track scanning instruments, an infrared interferometer ͑NAST-I͒ and a microwave radiometer ͑NAST-M͒, that fly onboard high-altitude aircraft such as the NASA ER-2 at an altitude near 20 km. NAST-I provides relatively high spectral resolution ͑0.25-cm Ϫ1 ͒ measurements in the 645-2700-cm Ϫ1 spectral region with moderate spatial resolution ͑a linear resolution equal to 13% of the aircraft altitude at nadir͒ cross-track scanning. We report the methodology for retrieval of atmospheric temperature and composition profiles from NAST-I radiance spectra. The profiles were determined by use of a statistical eigenvector regression algorithm and improved, as needed, by use of a nonlinear physical retrieval algorithm. Several field campaigns conducted under varied meteorological conditions have provided the data needed to verify the accuracy of the spectral radiance, the retrieval algorithm, and the scanning capabilities of this instrumentation. Retrieval examples are presented to demonstrate the ability to reveal fine-scale horizontal features with relatively high vertical resolution.
The airborne NPOESS Aircraft Sounding Test-bed Interferometer (NAST-I) has flown on numerous flig... more The airborne NPOESS Aircraft Sounding Test-bed Interferometer (NAST-I) has flown on numerous flights under the Aqua satellite in order to validate AIRS radiance measurements and profile retrievals. The NAST-I is an excellent AIRS airborne validation tool since it possesses relatively high spectral and spatial resolution as well as relatively low radiance measurement noise, especially after the data are spatially averaged to the footprint size of the AIRS sensor. The results of these airborne missions have shown that the AIRS calibration validates well against airborne interferometer radiance measurements 1 . Here, it is shown that the retrievals obtained using the same retrieval algorithm are in general agreement, although the airborne NAST-I result possesses higher vertical resolution as a consequence of it's higher spectral resolution and lower "effective" radiance noise level. The "effective" radiance noise level is a function of the single spectral sample radiance measurement noise, the number of spectral channels used for the retrieval, and the number of spatial samples averaged to produce the final profile result. For the NAST-I aircraft instrument, the effective radiance noise level is extremely small, particularly after reducing the horizontal linear resolution to that of the satellite AIRS instrument (i.e., ~14 km for AIRS as opposed to ~2 km for NAST-I), and as a result its relatively large spectral range and high spectral resolution (i.e., NAST-I possess nearly four times the number of spectral channels as does the AIRS). It is shown here that spatial averaging of the AIRS data, which decreases the noise level of the radiances used for the retrieval, improves the vertical resolution of the profile results.
The Workshop on Polarized Solid Targets, the 6th of a series which started in 1978, has been atte... more The Workshop on Polarized Solid Targets, the 6th of a series which started in 1978, has been attended by 47 participants, who presented 32 contributions, as many as ever. The presence of several young, “new” colleagues has been particularly gratifying and has contributed to create an atmosphere of lively and fruitful discussions. Furthermore, for the first time in many years we had the pleasure to meet a good number of colleagues from the Soviet Union, and we had the opportunity to learn and discuss about much interesting work which had been, alas, largely ignored in the West. It is to hope that the contacts which have been established at this Workshop will be actively pursued, they shall certainly bear interesting fruits.
India and the United States of America (U.S.A.) held a joint conference from June 21-25, 2004 in ... more India and the United States of America (U.S.A.) held a joint conference from June 21-25, 2004 in Bangalore, India to strengthen and expand cooperation in the area of space science, applications, and commerce. Following the recommendations in the joint vision statement released at the end of the conference, the National Oceanic and Atmospheric Administration (NOAA) and the Indian Space and
The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on Oc... more The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on October 19, 2006. The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25/cm and a spectral coverage from 645 to 2760/cm. Ultraspectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations during the JAIVEx are obtained and presented. These retrievals are further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed Interferom...
A state-of-the-art IR-only retrieval algorithm has been developed with an all-season-global EOF P... more A state-of-the-art IR-only retrieval algorithm has been developed with an all-season-global EOF Physical Regression and followed by 1-D Var. Physical Iterative Retrieval for IASI, AIRS, and NAST-I. The benefits of this retrieval are to produce atmospheric structure with a single FOV horizontal resolution (approx. 15 km for IASI and AIRS), accurate profiles above the cloud (at least) or down to the surface, surface parameters, and/or cloud microphysical parameters. Initial case study and validation indicates that surface, cloud, and atmospheric structure (include TBL) are well captured by IASI and AIRS measurements. Coincident dropsondes during the IASI and AIRS overpasses are used to validate atmospheric conditions, and accurate retrievals are obtained with an expected vertical resolution. JAIVEx has provided the data needed to validate the retrieval algorithm and its products which allows us to assess the instrument ability and/or performance. Retrievals with global coverage are un...
The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for... more The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite, but also included a strong component focusing on validation of the Atmospheric InfraRed Sounder (AIRS) aboard the AQUA satellite. The cross validation of IASI and AIRS is important for the joint use of their data in the global Numerical Weather Prediction process. Initial inter-comparisons of geophysical products have been conducted from different aspects, such as using different measurements from airborne ultraspectral Fourier transform spectrometers (specifically, the NPOESS Airborne Sounder Testbed Interferometer (NAST-I) and the Scanning-High resolution Interferometer Sounder (S-HIS) aboard the NASA WB-57 aircraft), UK Facility for Airborne Atmospheric Measurements (FAAM) BAe146-301 aircraft insitu instruments, dedicated dropsondes, radiosondes, and ground based Raman Lidar. An overview of ...
The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on Oc... more The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on October 19, 2006. The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25 cm(exp -1) and a spectral coverage from 645 to 2760 cm(exp -1). Ultra-spectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations are obtained and presented. These retrievals are further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed - Interfero...
The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for... more The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly forvalidation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25 cm-1 and aspectral coverage from 645 to 2760 cm-1. Ultra-spectral resolution infrared spectral radiance obtained from nearnadir observations provide atmospheric, surface, and cloud property information. An advanced retrievalalgorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloudparameter retrieval. This physical inversion scheme has been developed, dealing with cloudy as well as cloud-free radiance observed with ultraspectral infrared sounders, to simultaneously retrieve surface, atmosphericthermodynamic, and cloud microphysical parameters. A fast radiative transfer model, which applies to thecloud-free and/or clouded atmosphere, is used for atmospheric profile and cloud parameter retrieval. A one-dimensional (1-d) variational multi...
The Infrared Atmospheric Sounding Interferometer (IASI) is a modern satellite sensor with 8461 ch... more The Infrared Atmospheric Sounding Interferometer (IASI) is a modern satellite sensor with 8461 channels and a spectral resolution of 0.25 wavenumber. It provides a wealth of information on atmospheric and surface properties. Due to the high spectral resolution, a large number of Radiative Transfer (RT) calculations through the inhomogeneous atmosphere are needed. Usually, only subsets of channels are used to perform physical inversions for atmospheric profiles. This paper presents a novel radiative transfer model based on principal component analysis. The Principal Componentbased Radiative Transfer Model (PCRTM) predicts PC scores and associated derivatives with respect to various atmospheric and surface properties in PC space directly. Usually, less than 200 PCs are needed to regenerate the original radiance spectrum with accuracy better than instrument noise level. Therefore, the dimension of the spectrum is reduced by an order of magnitude for hyper spectral sensors with thousand...
The real-time operational requirements for SARCOM translation into a high speed image data handle... more The real-time operational requirements for SARCOM translation into a high speed image data handler and processor to achieve the desired compression ratios and the selection of a suitable image data compression technique with as low as possible fidelity (information) losses and which can be implemented in an algorithm placing a relatively low arithmetic load on the system are described.
High-resolution infrared radiance spectra obtained from near nadir observations provide atmospher... more High-resolution infrared radiance spectra obtained from near nadir observations provide atmospheric, surface, and cloud property information. A fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. The retrieval algorithm is presented along with its application to recent field experiment data from the NPOESS Airborne Sounder Testbed-Interferometer (NAST-I). The retrieval accuracy dependence on cloud properties is discussed. It is shown that relatively accurate temperature and moisture retrievals can be achieved below optically thin clouds. For optically thick clouds, accurate temperature and moisture profiles down to cloud top level are obtained. For both optically thin and thick cloud situations, the cloud top height can be retrieved with an accuracy of approximately 1.0 km. Preliminary NAST-I retrieval results from the recent Atlantic-THORPEX Regional Campaign (ATReC) are presented and compared with coincident observations obtained from dropsondes and the nadir-pointing Cloud Physics Lidar (CPL).
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Papers by Stephen Mango