596 research outputs found
NASA/MSFC FY88 Global Scale Atmospheric Processes Research Program Review
Interest in environmental issues and the magnitude of the environmental changes continues. One way to gain more understanding of the atmosphere is to make measurements on a global scale from space. The Earth Observation System is a series of new sensors to measure globally atmospheric parameters. Analysis of satellite data by developing algorithms to interpret the radiance information improves the understanding and also defines requirements for these sensors. One measure of knowledge of the atmosphere lies in the ability to predict its behavior. Use of numerical and experimental models provides a better understanding of these processes. These efforts are described in the context of satellite data analysis and fundamental studies of atmospheric dynamics which examine selected processes important to the global circulation
The North Atlantic Waveguide and Downstream Impact Experiment
The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum fĂŒr Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français InstrumentĂ©s pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe
A review of progress and applications of pulsed doppler wind LiDARs
Doppler wind LiDAR (Light Detection And Ranging) makes use of the principle of optical Doppler shift between the reference and backscattered radiations to measure radial velocities at distances up to several kilometers above the ground. Such instruments promise some advantages, including its large scan volume, movability and provision of 3-dimensional wind measurements, as well as its relatively higher temporal and spatial resolution comparing with other measurement devices. In recent decades, Doppler LiDARs developed by scientific institutes and commercial companies have been well adopted in several real-life applications. Doppler LiDARs are installed in about a dozen airports to study aircraft-induced vortices and detect wind shears. In the wind energy industry, the Doppler LiDAR technique provides a promising alternative to in-situ techniques in wind energy assessment, turbine wake analysis and turbine control. Doppler LiDARs have also been applied in meteorological studies, such as observing boundary layers and tracking tropical cyclones. These applications demonstrate the capability of Doppler LiDARs for measuring backscatter coefficients and wind profiles. In addition, Doppler LiDAR measurements show considerable potential for validating and improving numerical models. It is expected that future development of the Doppler LiDAR technique and data processing algorithms will provide accurate measurements with high spatial and temporal resolutions under different environmental conditions
NASA/MSFC FY-85 Atmospheric Processes Research Review
The two main areas of focus for the research program are global scale processes and mesoscale processes. Geophysical fluid processes, satellite doppler lidar, satellite data analysis, atmospheric electricity, doppler lidar wind research, and mesoscale modeling are among the topics covered
Saharan dust transport studied by airborne Doppler wind lidar and numerical models
Every year a large amount of dust is transported over the north Atlantic ocean from North Africa into the Caribbean region. Despite the progress made during the last decades in the understanding and modeling of this process, many uncertainties still remain. In this cumulative thesis, the airborne Doppler wind lidar (DWL) measurements performed during the SALTRACE campaign (June-July 2013), large eddy simulations and the global atmospheric composition model MACC are used to study different aspects of the dust transport process and evaluate the current modeling capabilities.
As part of this work, a novel calibration algorithm for the retrieval of quantitative aerosol backscatter and extinction coefficients from the DWL measurements is introduced. This calibration procedure relies on the simultaneous measurement of the same atmospheric volume by the airborne DWL and an aerosol ground-based lidar. This method is then validated with satellite lidar CALIOP and ground-based lidar measurements. Additionally, improvements in vertical wind retrieval algorithms are discussed and their impact on the retrieval accuracy estimated by means of two different methods.
Based on this extended airborne DWL dataset, which includes simultaneous backscatter and wind measurements, different processes associated with the Saharan dust transport are investigated. Measurements carried out in the Cabo Verde and Barbados regions revealed the presence of island-induced gravity waves. These measurements are used in combination with in-situ wind and particle number density retrievals, large eddy simulations, and wavelet analysis to determine the main characteristics of the observed waves and their interaction with the Saharan Air Layer. Finally, DWL and CALIOP measurements are used to evaluate the capabilities of the MACC global aerosol model to reproduce the Saharan dust long-range transport process during SALTRACE. A comparison and analysis of the measured and simulated average wind and dust distributions in the West African and Caribbean regions is presented. Three case studies covering different characteristic features, like the African Easterly Jet and the dust transport modulation by the African Easterly Waves, are discussed with an outlook to future campaigns and the assimilation of the data products for the ESA's future satellite missions Aeolus and EarthCARE
NASA's Hurricane and Severe Storm Sentinel (HS3) Investigation
The National Aeronautics and Space Administrations (NASA) Hurricane and Severe Storm Sentinel (HS3) investigation was a multi-year field campaign designed to improve understanding of the physical processes that control hurricane formation and intensity change, specifically the relative roles of environmental and inner-core processes. Funded as part of NASAs Earth Venture program, HS3 conducted five-week campaigns during the hurricane seasons of 2012-14 using the NASA Global Hawk aircraft, along with a second Global Hawk in 2013 and a WB-57f aircraft in 2014. Flying from a base at Wallops Island, Virginia, the Global Hawk could be on station over storms for up to 18 hours off the East Coast of the U.S. to about 6 hours off the western coast of Africa. Over the three years, HS3 flew 21 missions over 9 named storms, along with flights over two non-developing systems and several Saharan Air Layer (SAL) outbreaks. This article summarizes the HS3 experiment, the missions flown, and some preliminary findings related to the rapid intensification and outflow structure of Hurricane Edouard (2014) and the interaction of Hurricane Nadine (2012) with the SAL
NASA/MSFC FY91 Global Scale Atmospheric Processes Research Program Review
The reports presented at the annual Marshall Research Review of Earth Science and Applications are compiled. The following subject areas are covered: understanding of atmospheric processes in a variety of spatial and temporal scales; measurements of geophysical parameters; measurements on a global scale from space; the Mission to Planet Earth Program (comprised of and Earth Observation System and the scientific strategy to analyze these data); and satellite data analysis and fundamental studies of atmospheric dynamics
Validation and assimilation of Aeolus wind observations
Along with scientific and technological developments, the advancement of the Global Observing System (GOS) has been one of the most important factors contributing to the increase in numerical weather forecasting (NWP) skill in recent years. The initial conditions of a forecast are provided by data assimilation systems, combining the latest short-range forecast with a selection of atmospheric observations. One of the current major limitations is the lack of global wind profile observations, particularly in regions and for spatial scales where geostrophic mass-wind coupling is weak.
The European Space Agency's (ESA) Doppler Wind Lidar (DWL) satellite mission Aeolus provides a novel data set of wind profiles with quasi-global coverage intended to fill this gap in the GOS. This thesis aims to assess the impact of the Aeolus observations in NWP to demonstrate the potential value of such satellite-based DWL missions.
A crucial prerequisite for using meteorological observations in NWP data assimilation systems is the knowledge and characterization of their errors. Therefore, in the first part of this work, a validation study is conducted to investigate the quality of the Aeolus wind profiles. Comparisons with three independent reference data sets - collocated radiosonde observations as well as model equivalents of the global ICOsahedral Nonhydrostatic (ICON) model of the German Weather Service (DWD) and the Integrated Forecast System (IFS) model of the European Centre for Medium-Range Weather Forecasts (ECMWF) - enable a comprehensive estimation of the systematic and random errors of the Aeolus observations. In addition, the systematic errors are examined for their dependencies, and correction approaches that can be used in data assimilation systems as part of quality control are tested.
Discrepancies between the radiosonde and model-based validation results that occur in determining the random error are mainly due to differences in spatial and temporal representativeness. The representativeness error components can be estimated using high-resolution regional model simulations and thus can be taken into account in determining the Aeolus observational error. The results provide important information on the magnitude and vertical structure of the Aeolus Rayleigh and Mie wind error, which serves as the basis for the assigned observational error in the data assimilation.
The second part of this thesis examines how numerical weather forecasting benefits from the assimilation of the novel DWL observations from the Aeolus satellite. For this purpose, an Observing System Experiment (OSE) based on the operational global assimilation system of ICON at DWD with and without the assimilation of Aeolus observations is analyzed. Besides global impact statistics, regions and periods with particularly pronounced impact are investigated further to understand the underlying dynamics leading to the overall beneficial impact. The largest impact of assimilating Aeolus observations occurs in the 2-3 day wind and temperature forecast in the tropical upper troposphere and lower stratosphere and in the Southern Hemisphere. The influence of the Aeolus observations in the Northern Hemisphere is less pronounced but still relatively large compared to other observing systems. Furthermore, this thesis illustrates three examples of atmospheric phenomena that constitute dynamical scenarios for significant forecast error reduction: the change of the oscillatory phase of two large-scale tropical circulation systems - the quasi-biennial oscillation (QBO) and the El NiñoâSouthern Oscillation (ENSO) - and the interaction of tropical cyclones undergoing extratropical transition (ET) with the midlatitude waveguide. These indications of dynamical changes and processes related to the particularly high impact of Aeolus on NWP forecasts provide important information for the advancement of observing and NWP systems and will serve as the basis for future studies on opportunities to improve NWP forecasts by additional observations
Planning, implementation, and first results of the Tropical Composition, Cloud and Climate Coupling Experiment (TC4)
The Tropical Composition, Cloud and Climate Coupling Experiment (TC4), was based in Costa Rica and Panama during July and August 2007. The NASA ER-2, DC-8, and WB-57F aircraft flew 26 science flights during TC4. The ER-2 employed 11 instruments as a remote sampling platform and satellite surrogate. The WB-57F used 25 instruments for in situ chemical and microphysical sampling in the tropical tropopause layer (TTL). The DC-8 used 25 instruments to sample boundary layer properties, as well as the radiation, chemistry, and microphysics of the TTL. TC4 also had numerous sonde launches, two ground-based radars, and a ground-based chemical and microphysical sampling site. The major goal of TC4 was to better understand the role that the TTL plays in the Earth's climate and atmospheric chemistry by combining in situ and remotely sensed data from the ground, balloons, and aircraft with data from NASA satellites. Significant progress was made in understanding the microphysical and radiative properties of anvils and thin cirrus. Numerous measurements were made of the humidity and chemistry of the tropical atmosphere from the boundary layer to the lower stratosphere. Insight was also gained into convective transport between the ground and the TTL, and into transport mechanisms across the TTL. New methods were refined and extended to all the NASA aircraft for real-time location relative to meteorological features. The ability to change flight patterns in response to aircraft observations relayed to the ground allowed the three aircraft to target phenomena of interest in an efficient, well-coordinated manner
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