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- Author or Editor: Jörg Ackermann x
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Abstract
The European Space Agency plans to install the backscatter lidar system ATLID (atmospheric lidar) on a polar-orbiting platform at the beginning of the next century. This kind of active remote sensing will provide highly accurate information about cloud-top height, which, in addition to collocated passive sounder's measurements of brightness temperature, might improve retrieved vertical temperature profiles and serve as a supplementation of present cloud climatologies. Due to technical constraints, ATLID will not provide spatially continuous information about cloud-top height. The representativeness of the lidar measurements for the whole cloud field constitutes the sampling problem and is investigated in two steps: first, a scan mode for ATLID is developed, which on the assumption that the cloud field is a two-dimensional random variable gives an equal pixel spacing along and across the flight track of the orbiter. Second, the simulated lidar measurements given by the elaborated scan mode are contributed to a spatially continuous cloud field represented by Advanced Very High Resolution Radiometer images. From the dispersed lidar measurements with a footprint diameter of about 1 km the cloud field is restored by a spatial interpolation scheme and compared with the original cloud field by a linear regression analysis. It turns out that the sampling error and hence the benefits of ATLID strongly depend on the meteorological situation: if the required vertical accuracy of the lidar measurement is about 250 m corresponding approximately to half of the vertical resolution of present retrieval schemes, the probability for a meaningful ATLID information is between 40% and 70%. Since an imager cannot provide a useful brightness temperature in case of multilayered or broken clouds within one imager pixel, the synergism of ATLID with a passive instrument also depends on the homogeneity of cloud-top height within the range of 1 km. To cheek this small-scale variability of cloud tops data from the European Lidar Airborne Campaign 1990 are evaluated. Results show that for optically thick clouds the variability exceeds in 3% to 38% of all considered cases a threshold of 250 m. Additionally, power-spectrum analyses confirm the result of the sampling analyses.
Abstract
The European Space Agency plans to install the backscatter lidar system ATLID (atmospheric lidar) on a polar-orbiting platform at the beginning of the next century. This kind of active remote sensing will provide highly accurate information about cloud-top height, which, in addition to collocated passive sounder's measurements of brightness temperature, might improve retrieved vertical temperature profiles and serve as a supplementation of present cloud climatologies. Due to technical constraints, ATLID will not provide spatially continuous information about cloud-top height. The representativeness of the lidar measurements for the whole cloud field constitutes the sampling problem and is investigated in two steps: first, a scan mode for ATLID is developed, which on the assumption that the cloud field is a two-dimensional random variable gives an equal pixel spacing along and across the flight track of the orbiter. Second, the simulated lidar measurements given by the elaborated scan mode are contributed to a spatially continuous cloud field represented by Advanced Very High Resolution Radiometer images. From the dispersed lidar measurements with a footprint diameter of about 1 km the cloud field is restored by a spatial interpolation scheme and compared with the original cloud field by a linear regression analysis. It turns out that the sampling error and hence the benefits of ATLID strongly depend on the meteorological situation: if the required vertical accuracy of the lidar measurement is about 250 m corresponding approximately to half of the vertical resolution of present retrieval schemes, the probability for a meaningful ATLID information is between 40% and 70%. Since an imager cannot provide a useful brightness temperature in case of multilayered or broken clouds within one imager pixel, the synergism of ATLID with a passive instrument also depends on the homogeneity of cloud-top height within the range of 1 km. To cheek this small-scale variability of cloud tops data from the European Lidar Airborne Campaign 1990 are evaluated. Results show that for optically thick clouds the variability exceeds in 3% to 38% of all considered cases a threshold of 250 m. Additionally, power-spectrum analyses confirm the result of the sampling analyses.
Abstract
An adequate estimation of the aerosol extinction-to-backscatter ratio S is important for solving the underdetermined single scattering lidar equation and for investigating the climate impact of aerosols. In this study, the extinction-to-backscatter ratios for the Nd:YAG wavelengths are calculated for continental, maritime, and desert aerosols; the corresponding aerosol components are varied within the expected natural variabilities of the particle number mixing ratios.
For continental aerosol, S increases with the relative humidity f from 40 to 80 sr. For maritime aerosol, the extinction-to-backscatter ratios lie between 15 and 30 sr for 355 and 532 nm and between 25 and 50 sr for 1064 nm. The desert aerosol exhibits a weak dependence of S on f and ranges between 42 and 48 sr for 355 nm and between 17 and 25 sr for 532 and 1064 nm. For practical applications, the calculated values of S are fitted by a power series expansion with respect to their dependence on f.
Abstract
An adequate estimation of the aerosol extinction-to-backscatter ratio S is important for solving the underdetermined single scattering lidar equation and for investigating the climate impact of aerosols. In this study, the extinction-to-backscatter ratios for the Nd:YAG wavelengths are calculated for continental, maritime, and desert aerosols; the corresponding aerosol components are varied within the expected natural variabilities of the particle number mixing ratios.
For continental aerosol, S increases with the relative humidity f from 40 to 80 sr. For maritime aerosol, the extinction-to-backscatter ratios lie between 15 and 30 sr for 355 and 532 nm and between 25 and 50 sr for 1064 nm. The desert aerosol exhibits a weak dependence of S on f and ranges between 42 and 48 sr for 355 nm and between 17 and 25 sr for 532 and 1064 nm. For practical applications, the calculated values of S are fitted by a power series expansion with respect to their dependence on f.
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Polar System is the European contribution to the European–U.S. operational polar meteorological satellite system (Initial Joint Polar System). It serves the midmorning (a.m.) orbit 0930 Local Solar Time (LST) descending node. The EUMETSAT satellites of this new polar system are the Meteorological Operational Satellite (Metop) satellites, jointly developed with ESA. Three Metop satellites are foreseen for at least 14 years of operation from 2006 onward and will support operational meteorology and climate monitoring.
The Metop Programme includes the development of some instruments, such as the Global Ozone Monitoring Experiment, Advanced Scatterometer, and the Global Navigation Satellite System (GNSS) Receiver for Atmospheric Sounding, which are advanced instruments of recent successful research missions. Core components of the Metop payload, common with the payload on the U.S. satellites, are the Advanced Very High Resolution Radiometer and the Advanced Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (ATOVS) package, composed of the High Resolution Infrared Radiation Sounder (HIRS), Advanced Microwave Sounding Unit A (AMSU-A), and Microwave Humidity Sounder (MHS). They provide continuity to the NOAA-K, -L, -M satellite series (in orbit known as NOAA-15, -16 and -17). MHS is a EUMETSAT development and replaces the AMSU-B instrument in the ATOVS suite. The Infrared Atmospheric Sounding Interferometer (IASI) instrument, developed by the Centre National d'Etudes Spatiales, provides hyperspectral resolution infrared sounding capabilities and represents new technology in operational satellite remote sensing.
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Polar System is the European contribution to the European–U.S. operational polar meteorological satellite system (Initial Joint Polar System). It serves the midmorning (a.m.) orbit 0930 Local Solar Time (LST) descending node. The EUMETSAT satellites of this new polar system are the Meteorological Operational Satellite (Metop) satellites, jointly developed with ESA. Three Metop satellites are foreseen for at least 14 years of operation from 2006 onward and will support operational meteorology and climate monitoring.
The Metop Programme includes the development of some instruments, such as the Global Ozone Monitoring Experiment, Advanced Scatterometer, and the Global Navigation Satellite System (GNSS) Receiver for Atmospheric Sounding, which are advanced instruments of recent successful research missions. Core components of the Metop payload, common with the payload on the U.S. satellites, are the Advanced Very High Resolution Radiometer and the Advanced Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (ATOVS) package, composed of the High Resolution Infrared Radiation Sounder (HIRS), Advanced Microwave Sounding Unit A (AMSU-A), and Microwave Humidity Sounder (MHS). They provide continuity to the NOAA-K, -L, -M satellite series (in orbit known as NOAA-15, -16 and -17). MHS is a EUMETSAT development and replaces the AMSU-B instrument in the ATOVS suite. The Infrared Atmospheric Sounding Interferometer (IASI) instrument, developed by the Centre National d'Etudes Spatiales, provides hyperspectral resolution infrared sounding capabilities and represents new technology in operational satellite remote sensing.
Abstract
After successful launch in November 2018 and successful commissioning of Metop-C, all three satellites of the EUMETSAT Polar System (EPS) are in orbit together and operational. EPS is part of the Initial Joint Polar System (IJPS) with the United States (NOAA) and provides the service in the midmorning orbit. The Metop satellites carry a mission payload of sounding and imaging instruments, which allow provision of support to operational meteorology and climate monitoring, which are the main mission objectives for EPS. Applications include numerical weather prediction, atmospheric composition monitoring, and marine meteorology. Climate monitoring is supported through the generation of long time series through the program duration of 20+ years. The payload was developed and contributed by partners, including NOAA, CNES, and ESA. EUMETSAT and ESA developed the space segment in cooperation. The system has proven its value since the first satellite Metop-A, with enhanced products at high reliability for atmospheric sounding, delivered a very strong positive impact on NWP and results beyond expectations for atmospheric composition and chemistry applications. Having multiple satellites in orbit—now three—has enabled enhanced and additional products with increased impact, like atmospheric motion vector products at latitudes not accessible to geostationary observations or increased probability of radio occultations and hence atmospheric soundings with the Global Navigation Satellite System (GNSS) Radio-Occultation Atmospheric Sounder (GRAS) instruments. The paper gives an overview of the system and the embarked payload and discusses the benefits of generated products for applications and services. The conclusions point to the follow-on system, currently under development and assuring continuity for another 20+ years.
Abstract
After successful launch in November 2018 and successful commissioning of Metop-C, all three satellites of the EUMETSAT Polar System (EPS) are in orbit together and operational. EPS is part of the Initial Joint Polar System (IJPS) with the United States (NOAA) and provides the service in the midmorning orbit. The Metop satellites carry a mission payload of sounding and imaging instruments, which allow provision of support to operational meteorology and climate monitoring, which are the main mission objectives for EPS. Applications include numerical weather prediction, atmospheric composition monitoring, and marine meteorology. Climate monitoring is supported through the generation of long time series through the program duration of 20+ years. The payload was developed and contributed by partners, including NOAA, CNES, and ESA. EUMETSAT and ESA developed the space segment in cooperation. The system has proven its value since the first satellite Metop-A, with enhanced products at high reliability for atmospheric sounding, delivered a very strong positive impact on NWP and results beyond expectations for atmospheric composition and chemistry applications. Having multiple satellites in orbit—now three—has enabled enhanced and additional products with increased impact, like atmospheric motion vector products at latitudes not accessible to geostationary observations or increased probability of radio occultations and hence atmospheric soundings with the Global Navigation Satellite System (GNSS) Radio-Occultation Atmospheric Sounder (GRAS) instruments. The paper gives an overview of the system and the embarked payload and discusses the benefits of generated products for applications and services. The conclusions point to the follow-on system, currently under development and assuring continuity for another 20+ years.
