A new airborne facility instrument for Earth science applications is introduced. The Mineral and Gas Identifier (MAGI) is a wide-swath (programmable up to ±42° off nadir) moderate spectral resolution ...thermal-infrared (TIR) imaging spectrometer that spans the 7.1- to 12.7-μm spectral window in 32 uniform and contiguous channels. Its spectral resolution enables improved discrimination of rock and mineral types, greatly expanded gas-detection capability, and generally more accurate land-surface temperature retrievals. The instrument design arose from trade studies between spectral resolution, spectral range, and instrument sensitivity and has now been validated by flight data acquired with the completed sensor. It offers a potential prototype for future space-based TIR instruments, which will require much higher spectral resolution than is currently available in order to address more detailed climate, anthropogenic, and solid Earth science questions.
Scattering properties of tropospheric aerosol layers were observed with airborne lidars during the Global Backscatter Experiment (GLOBE) airborne campaigns covering a wide range of latitude and ...longitude over the Pacific Ocean. Lidar data at 0.532, 1.064, 1.54, and 9.25 μm wavelengths are used to study the vertical profiles and optical properties of the marine boundary layer (MBL) as well as elevated dust layers due to transport of material from Asia. The lidars were calibrated to provide absolute aerosol backscatter coefficients at their respective wavelengths. The lidar data are compared with predictions based on commonly used dust and sea salt aerosol refractive index and size distribution parameters. Published observations of aerosol characteristics from onboard in situ sensors are used to verify locations where mineral dust aerosol dominated the aerosol optical properties in the free troposphere. Relative humidity has a major impact on the observed MBL aerosol scattering characteristics. The multiwavelength observations of the dust layers are consistent with the assumption that for the particle size range that dominates the scattering properties the particle size distribution varies little over 103 km transport distances and is not strongly dependent on altitude. A nonsphericity effect on the dust scattering, in particular the suppression of backscattering at the shorter lidar wavelengths, is discussed in the context of data comparisons with model predictions. The observations of the sea salt aerosol scattering in the remote MBL indicate that at altitudes above 150 m in optically clear conditions the influence of the supermicron coarse mode is minor compared with that of the submicron accumulation mode.
Active Raman sounding of the earth's water vapor field Tratt, David M.; Whiteman, David N.; Demoz, Belay B. ...
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy,
08/2005, Letnik:
61, Številka:
10
Journal Article
Recenzirano
The typically weak cross-sections characteristic of Raman processes has historically limited their use in atmospheric remote sensing to nighttime application. However, with advances in ...instrumentation and techniques, it is now possible to apply Raman lidar to the monitoring of atmospheric water vapor, aerosols and clouds throughout the diurnal cycle. Upper tropospheric and lower stratospheric measurements of water vapor using Raman lidar are also possible but are limited to nighttime and require long integration times. However, boundary layer studies of water vapor variability can now be performed with high temporal and spatial resolution. This paper will review the current state-of-the-art of Raman lidar for high-resolution measurements of the atmospheric water vapor, aerosol and cloud fields. In particular, we describe the use of Raman lidar for mapping the vertical distribution and variability of atmospheric water vapor, aerosols and clouds throughout the evolution of dynamic meteorological events. The ability of Raman lidar to detect and characterize water in the region of the tropopause and the importance of high-altitude water vapor for climate-related studies and meteorological satellite performance are discussed.
In 1992 the atmospheric lidar remote sensing groups of the National Aeronautics and Space Administration Marshall Space Flight Center, the National Oceanic and Atmospheric ...Administration/Environmental Technology Laboratory (NOAA/ETL), and the Jet Propulsion Laboratory began a joint collaboration to develop an airborne high-energy Doppler laser radar (lidar) system for atmospheric research and satellite validation and simulation studies. The result is the Multi-center Airborne Coherent Atmospheric Wind Sensor (MACAWS), which has the capability to remotely sense the distribution of wind and absolute aerosol backscatter in three-dimensional volumes in the troposphere and lower stratosphere.
A factor critical to the programmatic feasibility and technical success of this collaboration has been the utilization of existing components and expertise that were developed for previous atmospheric research by the respective institutions. For example, the laser transmitter is that of the mobile ground-based Doppler lidar system developed and used in atmospheric research for more than a decade at NOAA/ETL.
The motivation for MACAWS is threefold: 1) to obtain fundamental measurements of subsynoptic-scale processes and features to improve subgrid-scale parameterizations in large-scale models, 2) to obtain datasets in order to improve the understanding of and predictive capabilities for meteorological systems on subsynoptic scales, and 3) to validate (simulate) the performance of existing (planned) satellite-borne sensors.
Initial flight tests were made in September 1995; subsequent flights were made in June 1996 following system improvements. This paper describes the MACAWS instrument, principles of operation, examples of measurements over the eastern Pacific Ocean and western United States, and future applications.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tropospheric and lower stratospheric aerosol backscatter profiles were obtained with an airborne backscatter lidar at 9.25‐μm wavelength during the NASA Global Backscatter Experiment (GLOBE) airborne ...field campaigns in November 1989 and May/June 1990. The range of latitudes extended from 70°N to 62°S over the Pacific Ocean basin. The data provide evidence that the tropics are an effective sink for aerosol particles in the lidar‐active size range, most likely through efficient wet deposition processes. A reduction of planetary boundary layer (PBL) thickness and aerosol mass density was observed within the tropical regions of enhanced cumulus convection. PBL thickness maxima were consistently observed in the southern hemisphere at subtropical and high latitudes. The downward transport of volcanic aerosol from the February 1990 Kelut eruption into the upper troposphere was observed in the southern hemisphere during the May/June 1990 period. A springtime enhancement of aerosol in the middle troposphere, due to convection and transport of surface material, was observed in both hemispheres, although the seasonal enhancement was much more dramatic in the northern hemisphere due to the influence of the Asian continental source. Above the PBL the observed springtime enhancement was in the form of extensive layers, with the high‐altitude layers reaching the midlatitude tropopause near 140°E longitude.
Slicing is useful for many software engineering applications and has been widely studied for three decades, but there has been comparatively little work on slicing extended finite state machines ...(EFSMs). This paper introduces a set of dependence-based EFSM slicing algorithms and an accompanying tool. We demonstrate that our algorithms are suitable for dependence-based slicing. We use our tool to conduct experiments on 10 EFSMs, including benchmarks and industrial EFSMs. Ours is the first empirical study of dependence-based program slicing for EFSMs. Compared to the only previously published dependence-based algorithm, our average slice is smaller 40 percent of the time and larger only 10 percent of the time, with an average slice size of 35 percent for termination insensitive slicing.
Tropospheric and lower stratospheric aerosol backscatter data obtained from a calibrated backscatter lidar at Pasadena, California (34 deg N latitude) over the 1984-1993 period clearly indicate ...tightly coupled aerosol optical properties in the upper troposphere and lower stratosphere in the winter and early spring, due to the active midlatitude stratospheric-tropospheric (ST) exchange processes occurring at this time of year. Lidar data indicate that during pre-Pinaturbo background conditions, the subsequent purging of the aerosol in the upper troposphere caused a significant reduction in the aerosol content throughout the 8 - 18 km altitude region in the early spring period. The post-Pinatubo evidence of intense exchange in the winter and early spring is a significant increase in the upper tropospheric aerosol content, such that the backscatter levels reach values nearly equivalent to the enhanced backscatter levels existing in the lower stratosphere. The calculated stratospheric mass extrusion rate is consistent with a 45-day lifetime of lower stratospheric aerosol during this part of the year, which implies that midlatitude ST exchange is a significant sink for stratospheric aerosol.
PDF
