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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

The Contribution of Water Ice Clouds to the Water Cycle in the North Polar Region of Mars: Preliminary Analysis

While it has long been known that Mars' north residual polar cap and the Martian regolith are significant sources of atmospheric water vapor, the amount of water vapor observed in the northern spring season by the Viking Mars Atmospheric Water Detector instrument (MAWD) cannot be attributed to cap and regolith sources alone. Kahn suggested that ice hazes may be the mechanism by which additional water is supplied to the Martian atmosphere. Additionally, a significant decrease in atmospheric water vapor was observed in the late northern summer that could not be correlated with the return of the cold seasonal C02 ice. While the detection of water ice clouds on Mars indicate that water exists in Mars' atmosphere in several different phases, the extent to which water ice clouds play a role in moving water through the Martian atmosphere remains uncertain. Work by Bass et. al. suggested that the time dependence of water ice cap seasonal variability and the increase in atmospheric water vapor depended on the polar cap center reaching 200K, the night time saturation temperature. Additionally, they demonstrated that a decrease in atmospheric water vapor may be attributed to deposition of water ice onto the surface of the polar cap; temperatures were still too warm at this time in the summer for the deposition of carbon dioxide. However, whether water ice clouds contribute significantly to this variability is unknown. Additional information is contained in original extended abstract.

Bass, D. S.↗
DOE OSTI2015

DEEPLY EMBEDDED PROTOSTELLAR POPULATION IN THE 20 km s{sup −1} CLOUD OF THE CENTRAL MOLECULAR ZONE

We report the discovery of a population of deeply embedded protostellar candidates in the 20 km s{sup −1} cloud, one of the massive molecular clouds in the Central Molecular Zone (CMZ) of the Milky Way, using interferometric submillimeter continuum and H{sub 2}O maser observations. The submillimeter continuum emission shows five 1 pc scale clumps, each of which further fragments into several 0.1 pc scale cores. We identify 17 dense cores, among which 12 are gravitationally bound. Among the 18 H{sub 2}O masers detected, 13 coincide with the cores and probably trace outflows emanating from the protostars. There are also 5 gravitationally bound dense cores without H{sub 2}O maser detection. In total, the 13 masers and 5 cores may represent 18 protostars with spectral types later than B1 or potentially growing more massive stars at earlier evolutionary stages, given the non-detection in the centimeter radio continuum. In combination with previous studies of CH{sub 3}OH masers, we conclude that the star formation in this cloud is at an early evolutionary phase, before the presence of any significant ionizing or heating sources. Our findings indicate that star formation in this cloud may be triggered by a tidal compression as it approaches pericenter, similar to the case of G0.253+0.016 but with a higher star formation rate, and demonstrate that high angular resolution, high-sensitivity maser, and submillimeter observations are promising techniques to unveil deeply embedded star formation in the CMZ.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2002

Use of Collocated KWAJEX Satellite, Aircraft, and Ground Measurements for Understanding Ambiguities in TRMM Radiometer Rain Profile Algorithm

Coordinated ground, aircraft, and satellite observations are analyzed from the 1999 TRMM Kwajalein Atoll field experiment (KWAJEX) to better understand the relationships between cloud microphysical processes and microwave radiation intensities in the context of physical evaluation of the Level 2 TRMM radiometer rain profile algorithm and uncertainties with its assumed microphysics-radiation relationships. This talk focuses on the results of a multi-dataset analysis based on measurements from KWAJEX surface, air, and satellite platforms to test the hypothesis that uncertainties in the passive microwave radiometer algorithm (TMI 2a12 in the nomenclature of TRMM) are systematically coupled and correlated with the magnitudes of deviation of the assumed 3-dimensional microphysical properties from observed microphysical properties. Re-stated, this study focuses on identifying the weaknesses in the operational TRMM 2a12 radiometer algorithm based on observed microphysics and radiation data in terms of over-simplifications used in its theoretical microphysical underpinnings. The analysis makes use of a common transform coordinate system derived from the measuring capabilities of the aircraft radiometer used to survey the experimental study area, i.e., the 4-channel AMPR radiometer flown on the NASA DC-8 aircraft. Normalized emission and scattering indices derived from radiometer brightness temperatures at the four measuring frequencies enable a 2-dimensional coordinate system that facilities compositing of Kwajalein S-band ground radar reflectivities, ARMAR Ku-band aircraft radar reflectivities, TMI spacecraft radiometer brightness temperatures, PR Ku-band spacecraft radar reflectivities, bulk microphysical parameters derived from the aircraft-mounted cloud microphysics laser probes (including liquid/ice water contents, effective liquid/ice hydrometeor radii, and effective liquid/ice hydrometeor variances), and rainrates derived from any of the individual ground, aircraft, or satellite algorithms applied to the radar or radiometer measurements, or their combination. The results support the study's underlying hypothesis, particularly in context of ice phase processes, in that the cloud regions where the 2a12 algorithm's microphysical database most misrepresents the microphysical conditions as determined by the laser probes, are where retrieved surface rainrates are most erroneous relative to other reference rainrates as determined by ground and aircraft radar. In reaching these conclusions, TMI and PR brightness temperatures and reflectivities have been synthesized from the aircraft AMPR and ARMAR measurements with the analysis conducted in a composite framework to eliminate measurement noise associated with the case study approach and single element volumes obfuscated by heterogeneous beam filling effects. In diagnosing the performance of the 2a12 algorithm, weaknesses have been found in the cloud-radiation database used to provide microphysical guidance to the algorithm for upper cloud ice microphysics. It is also necessary to adjust a fractional convective rainfall factor within the algorithm somewhat arbitrarily to achieve satisfactory algorithm accuracy.

Smith, Eric A.↗
DOE OSTI2017

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during August-September 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds. Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C 10-12 ) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Chemical Imaging of Atmospheric Organic Particles in the Southern Great Plains Field Campaign Report

The main goal of this field project was to characterize the chemical and physical properties of atmospheric particles representative of the Southern Great Plains (SGP) environment to establish a relationship between the composition of aerosol particles and their atmospheric impacts. The specific research efforts were focused on in-depth microscopy studies of chemical and physical properties of atmospheric organic particles collected at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) SGP observatory. An array of novel molecular-level characterization and chemical imaging approaches were used to characterize chemical composition of particles and elucidate fundamental processes governing their atmospheric aging, evolution of chemical composition, optical properties, cloud formation ability, and implications for particle-cloud interactions – the most challenging problems relevant to predictive understanding of aerosol effects on climate.(1, 2) Atmospheric particles consist of a complex mixture of organic compounds with a wide range of molecular structures, morphologies, physical properties, and chemical reactivity. The chemical composition, morphology, and phase state of atmospheric particles are of crucial importance for understanding the formation and reaction mechanisms of particles, their atmospheric evolution, and their impact on climate. It is of great interest to understand how the chemical and morphological particle microstructure affects their physicochemical properties such as chemical reactivity, thermodynamics of gas-particle partitioning, phase separations inside individual particles, hygroscopicity, optical properties, and ability to form liquid droplets (cloud condensation nuclei) and ice crystals (ice nuclei) in clouds. The phase state of organic particles, which yet remains poorly understood, plays a key role in their physicochemical properties and has important implications in various atmospheric processes. Fundamental understanding of these physicochemical properties and their possible evolution in time requires advanced analytical approaches for chemical imaging of particles with a resolution on the scale of 10-100 nm.(3) Comprehensive characterization of the size-dependent chemical composition of individual particles collected at the site was carried out using advanced molecular-level characterization and imaging approaches to identify their possible sources and to correlate to their climatic properties.

Southern Great Plains, aerosols, HI-SCALE field ca↗
DOE OSTI2020

Cloud Shortwave Optical Properties

The data set consists of calibrated zenith shortwave spectral radiances (400-950 nm and 940-1665 nm) and cloud optical depth (COD) retrievals every 2 seconds. The field of view is 0.5 degree. Retrievals of cloud droplet effective radius and thermodynamic phase are currently experimental and done offline. Effective radius and phase are not in this data set.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

STUDYING ATMOSPHERE-DOMINATED HOT JUPITER KEPLER PHASE CURVES: EVIDENCE THAT INHOMOGENEOUS ATMOSPHERIC REFLECTION IS COMMON

We identify three Kepler transiting planets, Kepler-7b, Kepler-12b, and Kepler-41b, whose orbital phase-folded light curves are dominated by planetary atmospheric processes including thermal emission and reflected light, while the impact of non-atmospheric (i.e., gravitational) processes, including beaming (Doppler boosting) and tidal ellipsoidal distortion, is negligible. Therefore, those systems allow a direct view of their atmospheres without being hampered by the approximations used in the inclusion of both atmospheric and non-atmospheric processes when modeling the phase-curve shape. We present here the analysis of Kepler-12b and Kepler-41b atmosphere based on their Kepler phase curve, while the analysis of Kepler-7b was already presented elsewhere. The model we used efficiently computes reflection and thermal emission contributions to the phase curve, including inhomogeneous atmospheric reflection due to longitudinally varying cloud coverage. We confirm Kepler-12b and Kepler-41b show a westward phase shift between the brightest region on the planetary surface and the substellar point, similar to Kepler-7b. We find that reflective clouds located on the west side of the substellar point can explain the phase shift. The existence of inhomogeneous atmospheric reflection in all three of our targets, selected due to their atmosphere-dominated Kepler phase curve, suggests this phenomenon is common. Therefore, it is also likely to be present in planetary phase curves that do not allow a direct view of the planetary atmosphere as they contain additional orbital processes. We discuss the implications of a bright-spot shift on the analysis of phase curves where both atmospheric and gravitational processes appear, including the mass discrepancy seen in some cases between the companion’s mass derived from the beaming and ellipsoidal photometric amplitudes. Finally, we discuss the potential detection of non-transiting but otherwise similar planets, whose mass is too small to show a gravitational photometric signal, but their atmosphere is reflective enough to show detectable phase modulations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Examining the Impacts of Microphysical-Dynamical Feedbacks on Convective Clouds in Different Aerosol Environments Using Enhanced Observational and Modeling Strategies

This project investigated how microphysical–dynamical feedbacks influence deep convective clouds across a range of aerosol conditions, storm lifecycles, and meteorological regimes, and how these sensitivities depend on the modeling framework used to represent convection and microphysics. Using the Aerosol, Cloud, Precipitation, and Climate (ACPC) Working Group model intercomparison simulations of isolated deep convection in the Houston region, we found a robust warm-phase aerosol response in most cloud-resolving models. Increased aerosol loading tended to suppress warm-rain production, increase cloud water, and reduce surface rainfall and near-surface evaporation. These impacts were typically strongest early in the convective lifecycle, with the largest aerosol-driven differences occurring during the first half of storm evolution. The ice-phase response, on the other hand, varied widely across modeling frameworks, and differed in sign, timing, and vertical structure. Ice microphysical pathways and parameterizations are therefore leading sources of uncertainty in aerosol–deep convection interactions. Theoretical analyses further suggested that aerosol-driven invigoration through cold-phase processes was much weaker than previously hypothesized for cold-based storms, and in warm-based storms could even reduce updraft strength. These results imply that any invigoration signal is more likely linked to warm-phase processes and peaks early in storm development.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1985

Particle Cloud Combustion Experiment

Preparation of flight experiment designs is supported by experimental studies of acoustically induced mixing process, optical transmissivities of particle cloud distributions, wall saturation effects and their control through the use of electrically neutral flame tube materials and surfaces, and the pyrolysis-vaporization kinetics of selected organic particulates. Drop tower tests of stabilized particle cloud flames have allowed valuable comparison of g = 0 and g = 1 (upwards and downwards) stabilized flame propagation. These stabilized flame data will be valuable assists in dealing with the freely propagating particle cloud flame data anticipated through Space Shuttle experimentation. Supporting theoretical studies emphasize comprehensive flame propagation and extinction relations among premixed single phase (gaseous) flames and premixed particle cloud flames, for both stabilized and freely propagating flames.

Berlad, A. L.↗
NASA NTRSDate not supplied

Attitude Ground System: Recent Experiences in Attitude Sensor Calibration and Upcoming Mission Support for Momentum Unloading

A key component of the mission ground system used for supporting NASA Goddard Space Flight Center space missions, known as the Attitude Ground System (AGS), is used to perform operational and analytical support for the spacecraft attitude con-trol system (ACS). The AGS is comprised of a real-time attitude analysis and moni-toring system, and a tool for performing offline analysis of the ACS system using key sensor telemetry collected and stored onboard and transmitted to the mission operations center. The AGS performs numerous functions, including independent ground attitude determination, attitude slew planning and commanding, attitude sensor calibration, and real-time monitoring of the health and safety of the ACS. The AGS is developed in MATLAB using a core library of utility functions called the Multi-Mission Three-Axis Satellite System (MTASS). The MTASS library has been used to support mission operations for over thirty NASA missions starting in the late 1990s. It is customized for each mission to meet specific mission requirements. In this paper we describe recent operational experience using the AGS to support the launch and early orbit (L&EO) phase of the Plankton, Aerosol, Cloud Ocean Ecosys-tem (PACE) and Joint Polar Satellite System (JPSS) missions. Our summary of L&EO support for PACE and JPSS includes ACS sensor calibration of the alignment and scale factors for the Star Trackers, Inertial Reference Unit, and Three-Axis Magnetometers. We will also describe new capabilities for planning and executing reaction wheel momentum unloading for the Roman Space Telescope (RST) During the spacecraft early orbit phase, the AGS is operated in the mission operations center by a team of subject matter experts that also develop and configure the AGS soft-ware. This unique approach, integrating system development and operation in a sin-gle engineering team, provides valuable expertise for quick assessment of ACS per-formance and safety; critical to anomaly resolution and mission success.

Guidance, Navigation, and Control↗
NASA NTRS1993

Inference of cirrus cloud properties using satellite-observed visible and infrared radiances. II - Verification of theoretical cirrus radiative properties

The study presents a methodology developed to apply a parameterization of radiative transfer calculations to satellite analyses of cirrus clouds. Cloud heights and optical depths are derived from visible and IR window measurements taken during FIRE when cirrus clouds were present. Geostationary satellite retrievals are compared to lidar-derived cloud heights and retrievals from a polar-orbiting satellite taken at different angles to determine which theoretical models of scattering phase function and single-scattering albedo best represent actual cirrus clouds. Models using small scattering phase function and single-scattering albedo best represent actual cirrus clouds. It is concluded that interpretation of cirrus reflectance with water-droplet models leads to biased results. The cloud-height and optical depth biases can be minimized with the aid of the C20 or cirrostratus models.

Minnis, Patrick↗
DOE OSTI2014

The Ne-to-O abundance ratio of the interstellar medium from IBEX-Lo observations

In this paper we report on a two-year study to estimate the Ne/O abundance ratio in the gas phase of the local interstellar cloud (LIC). Based on the first two years of observations with the Interstellar Boundary Explorer, we determined the fluxes of interstellar neutral (ISN) O and Ne atoms at the Earth's orbit in spring 2009 and 2010. A temporal variation of the Ne/O abundance ratio at the Earth's orbit could be expected due to solar cycle-related effects such as changes of ionization. However, this study shows that there is no significant change in the Ne/O ratio at the Earths orbit from 2009 to 2010. We used time-dependent survival probabilities of the ISNs to calculate the Ne/O abundance ratio at the termination shock. Then we estimated the Ne/O abundance ratio in the gas phase of the LIC with the use of filtration factors and the ionization fractions. From our analysis, the Ne/O abundance ratio in the LIC is 0.33 ± 0.07, which is in agreement with the abundance ratio inferred from pickup-ion measurements.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

Molecule formation in normal clouds

Some aspects of molecule formation in normal interstellar clouds, i.e., clouds having particle densities of less than 100 per cu cm, are discussed in light of recent studies. It is pointed out that, with their relatively large depletion parameter values (DPVs), CH clouds are 'young', whereas OH clouds have small DPVs and are 'old'. The theoretical reason for this is that OH, as a product of grain catalysis, persists over a much longer period of cloud evolution, whereas CH(+), CH, and CN, as products of gas-phase reaction, can be found only in 'young' clouds where depletion has not yet occurred. This may explain why OH has not been seen in radio observations of regions where CH(+), CH, and CN have been seen optically.

Aannestad, P. A.↗
NASA NTRS1976

Phase B: Final definition and preliminary design study for the initial Atmospheric Cloud Physics Laboratory (ACPL), a spacelab mission payload

A preliminary identification of the Supporting Research and Technology (SR&T) necessary during the planned evolution of atmospheric cloud physics is discussed. All requirements are for subsequent flights over its expected ten year lifetime. Those components identified as requiring some SR&T work prior to inclusion are listed. A data sheet is included for each item, briefly justifying the need, giving general objectives for the proposed development effort and identifying approximate schedule requirements on the program.

Source record↗
NASA NTRS1976

Phase B: Final definition and preliminary design study for the initial Atmospheric Cloud Physics Laboratory (ACPL): A spacelab mission payload. Final review (DR-MA-03)

Systems design for an initial atmospheric cloud physics laboratory to study microphysical processes in zero gravity is presented. Included are descriptions of the fluid, thermal, mechanical, control and data, and electrical distribution interfaces with Spacelab. Schedule and cost analysis are discussed.

Clausen, O. W.↗
NASA NTRS2013

CGILS: Results from the First Phase of an International Project to Understand the Physical Mechanisms of Low Cloud Feedbacks in Single Column Models

1] CGILS-the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)-investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: in a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as the "NESTS" negative cloud feedback and the "SCOPE" positive cloud feedback (Negative feedback from Surface Turbulence under weaker Subsidence-Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations

Single Column Models↗