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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

In situ measurements of BrO in the Arctic stratosphere

Mixing ratios of BrO have been measured in the Arctic lower statosphere with an instrument mounted on the NASA ER-2 aircraft. Observations from fourteen flights above the Arctic Circle in January and February of 1989 defined mixing ratios within the vortex of 4 + or - 2 parts per trillion by volume (pptv) at a potential temperature of 400 K, rising to 8 + or - 2 pptv at 470 K. These values are twice as large as values found at equivalent potential temperatures at lower latitudes, and are comparable to the mixing ratios found inside the antarctic polar vortex. Within the statistical uncertainty of the measurements, no BrO was observed in darkness at any time either inside or outside of the vortex, indicating that active bromine was sequestered in long-lived reservoirs, probably BrONO2 and BrCl. These measurements, in conjuction with measurements of ClO, demonstrate that the interaction of bromine and chlorine could represent a major sink for ozone in the presence of sunlight.

Toohey, D. W.↗
NASA NTRS1990

Loss of ozone in the Arctic vortex for the winter of 1989

Measurements of ClO (Brune et al., 1990) acquired during the Airborne Arctic Stratospheric Expedition are used to infer concentrations of reactive chlorine (ClO + 2 x Cl2O2). Observed fields of potential temperature and potential vorticity are used to extrapolate in situ data to larger regions of the vortex. Calculated values of the loss rate of O3, based on estimates of reactive chlorine and measurements of BrO (Toohey et al., 1990), suggest that the loss of O3 was abut 12 pct for levels of the atmosphere with potential temperatures between 440 and 470 K over the 39 day duration of the ER-2 flights into the polar vortex. Calculated loss rates agree with observed rates of removal of O3, although significant uncertainties exist for each.

Salawitch, Ross J.↗
NASA NTRS1990

Microwave radiative transfer studies using combined multiparameter radar and radiometer measurements during Cohmex

Theoretical calculations of the upwelling microwave radiances from clouds containing layers of rain, ice, and a melting region were performed at frequencies of 18, 37, and 92 GHz. These frequencies coincide with high-resolution microwave radiometer measurements taken aboard the NASA ER-2 high-altitude aircraft during the summer 1986 Cohmex (Cooperative Huntsville Meteorological Experiment) in Alabama. For purposes of brightness temperature computations, the storms were modeled with rain, melting phase, and ice layers. The melting phase region was composed of water-coated ice spheres defined by a 'melt index' in terms of the volume fraction of water. Single scatter albedo, scattering, and extinction coefficients were computed at the above frequencies as a function of the rain rate and melt index. In addition, multiparameter radar observations of the storm were mapped into a Cartesian space and averaged over regions comparable to the radiometer footprint.

Vivekanandan, J.↗
NASA NTRS1990

Heterogeneous chemistry on liquid sulfate aerosols - A comparison of in situ measurements with zero-dimensional model calculations

The possibility that stratospheric chlorine is converted from reservoir to reactive forms by heterogeneous reactions on background sulfate aerosols is examined. Tightly constrained photochemical models have been used to calculate ClO abundances for the morning and the afternoon conditions observed on January 24, 1989 outside the Arctic polar vortex by instruments on the NASA ER-2 aircraft. Calculations involving gas-phase chemistry only and calculations with heterogeneous chemistry including HCl evaporation from the aerosol both produce ClO abundances that agree with observations; calculations in which HCl removal from the aerosol is controlled by heterogeneous reactions produce ClO abundances that are 3 to 3.5 times larger than observations. These results suggest that HCl evaporation must be included in a model of the chemistry of background aerosols.

Mather, J. H.↗
NASA NTRS1990

Remote sounding of the tropical cirrus cloud temperature and optical depth using 6.5 and 10.5-micron radiometers during STEP

A dual-channel retrieval technique involving the water vapor band at 6.5 microns and the window region at 10.5 microns has been developed to infer the temperature and emissivity of tropical anvils. This technique has been applied to data obtained from the ER-2 narrow field-of-view radiometers during two flights in the field observation of the Stratosphere-Troposphere Exchange Project near Darwin, Australia, January-February 1987. The retrieved cloud temperatures are between 190 and 240 K, while the cloud emissivities derived from the retrieval algorithm range from about 0.2 to 1. Moreover, the visible optical depths have been obtained from the cloud emissivity through a theoretical parameterization with values of 0.5-10. A significant portion of tropical cirrus clouds are found to have optical depths greater than about 6. Because of the parameterization, the present technique is unable to precisely determine the optical depth values for optically thick cirrus clouds.

Liou, K. N.↗
NASA NTRS1990

Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols

The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.

Pueschel, R. F.↗
NASA NTRS1990

Cirrus cloud statistics: Temperatures and optical depths

Measurements of the upwelling infrared radiance at 10.5 and 6.5 microns were obtained during the FIRE cirrus Intensive Field Observations using a radiometer with a 15 deg cone nadir field-of-view flown on the NASA Ames ER-2. Data are recorded at a frequency of 1 Hz and the radiometer is continuously calibrated with a liquid nitrogen blackbody source, thereby providing a large number of very accurate radiance values during the course of a several hour flight. For this study, the focus is on the statistical properties of the cirrus deck as deduced from the radiance data. The data acquired on 28 October 1986 is stressed, but some data from the other flights are also shown for comparison purposes.

Valero, Francisco P. J.↗
NASA NTRS1990

Overview of the 27-28 October FIRE Cirrus IFO case: Meteorology and cloud fields

A detailed description of the meteorology of the 27 and 28 October FIRE Cirrus IFO case is presented. The progression of synoptic scale events over the region is reviewed including the evolution of surface and upper air features, i.e., the surface cyclone that formed to the west over Montana on the 27th and moved through Wisconsin late on the 28th and the associated short wave ridge aloft. A summary of the corresponding cloud conditions observed over the area of aircraft operations is given including characterization of the cloud forms and cloud heights based on information derived from debriefings of the aircrews, surface observations, airborne (ER-2) and surface lidars observations and satellite imagery (GOES). The correspondence between the resolved meteorological features (subsynoptic rawinsonde network) and the development of cloud layers is illustrated. In particular, the discussion emphasizes the relationship between vertical thermodynamic structure and the character and vertical structure of the cloud fields. The role of the larger scale in maintaining the observed vertical structure is quantified both with respect to its control via forced ascent and advective processes. Based on results of these analyses, conclusions are drawn with respect to the design of future field missions.

Starr, David OC.↗
NASA NTRS1990

Cloud spatial structure during the FIRE MS IFO

The fractal properties of clouds observed during the FIRE Marine Stratocumulus Intensive Field Observations (MS IFO) and their effects on the large scale radiative properties of the atmosphere are examined. This involves three states: (1) analysis of LANDSAT Thematic Mapper (TM) cloud data to determine the scaling properties associated with various cloud types; (2) simulation of fractal clouds with realistic scaling properties; and (3) computation of mean radiative properties of fractal clouds as a function of their scaling properties. Thirty-three LANDSAT scenes were acquired as part of the FIRE Marine Stratocumulus IFO in July 1987. They exhibit a wide variety of stratocumulus structures. Analysis has so far focused upon the July 7 scene, in which the NASA ER-2, the BMO C130 and the NCAR Electra repeatedly gathered data across a stratocumulus-fair weather cumulus transition.

Cahalan, Robert F.↗
NASA NTRS1990

Preliminary results of radiation measurements from the marine stratus FIRE experiment

During the marine stratocumulus phase of the First International Satellite Cloud Climatology Regional Experiment (FIRE) in July 1987, researchers acquired radiative flux data from a variety of instruments which were flown on the ER-2 high altitude aircraft. The spectral coverage ranged from the near UV to beyond 40 microns. A survey and selected preliminary analyses of these measurements are presented. The specific instruments used in the experiment were chosen primarily for measuring quantities of specific interest for marine stratocumulus fields. However, testing and evaluation of instrumentation and techniques to be used in the future inland cirrus experiment was also an important consideration. Details of the instruments and the significance of what they measure are given.

Valero, Francisco P. J.↗
NASA NTRS1990

Thermodynamic structure of the stratocumulus-capped boundary layer on 7 July, 1987

As part of project First ISCCP Regional Experiment (FIRE), a mission was carried out on 7 July 1987 to study the thermodynamic structure of a boundary layer which is in transition from a clear to a cloudy state. The National Center for Aeronautical Research (NCAR) Electra flew a pattern in tight coordination with the NASA ER-2 aircraft near 122 West, 31.6 North off the coast of California. A description is given here of the thermodynamic structure. The purpose is to derive the entrainment rate and the fluxes of the thermodynamic variables. To this end researchers represent the data in conserved variable diagrams.

Boers, Reinout↗
NASA NTRS1989

Analysis of the boreal forest-tundra ecotone: A test of AVIRIS capabilities in the Eastern Canadian subarctic

A comparison was conducted between ground reflectance spectra collected in Schefferville, Canada and imaging spectrometer observations acquired by the AVIRIS sensor in a flight of the ER-2 Aircraft over the same region. The high spectral contrasts present in the Canadian Subarctic appeared to provide an effective test of the operational readiness of the AVIRIS sensor. Previous studies show that in this location various land cover materials possess a wide variety of visible/near infrared reflectance properties. Thus, this landscape served as an excellent test for the sensing variabilities of the newly developed AVIRIS sensor. An underlying hypothesis was that the unique visible/near infrared spectral reflectance patterns of Subarctic lichens could be detected from high altitudes by this advanced imaging spectrometer. The relation between lichen occurrence and boreal forest-tundra ecotone dynamics was investigated.

Goward, Samuel N.↗
NASA NTRS1990

Analysis of wind profile measurements from an instrumented aircraft

The results of an experimental program to determine the capability of measuring wind profiles on support of STS operations with an instrumented aircraft are discussed. These results are a compilation of the flight experiments and the statistical data comparing the quality of the aircraft measurements with quasi-simultaneous and quasi-spatial overlapping Jimsphere measurements. An instrumented aircraft was chosen as a potential alternative to the Jimsphere/radar system for expediting the wind profile calculation by virtue of the ability of an aircraft to traverse the altitudes of interest in roughly 10 minutes. The two aircraft which participated in the study were F-104 and ER-2.

Paige, Terry S.↗
NASA NTRS1990

High altitude reconnaissance aircraft

At the equator the ozone layer ranges from 65,000 to 130,000 plus feet, which is beyond the capabilities of the ER-2, NASA's current high altitude reconnaissance aircraft. The Universities Space Research Association, in cooperation with NASA, is sponsoring an undergraduate program which is geared to designing an aircraft that can study the ozone layer at the equator. This aircraft must be able to cruise at 130,000 feet for six hours at Mach 0.7, while carrying 3,000 lbs. of payload. In addition, the aircraft must have a minimum range of 6,000 miles. In consideration of the novel nature of this project, the pilot must be able to take control in the event of unforeseen difficulties. Three aircraft configurations were determined to be the most suitable - a joined-wing, a biplane, and a twin-boom conventional airplane. The performance of each configuration was analyzed to investigate the feasibility of the project.

Yazdo, Renee Anna↗
NASA NTRS1990

The NASA-ER2 meteorological measurement system: Instrumentaion, calibration and intercomparison results

The NASA ER-2 aircraft is used as a platform for high altitude atmospheric missions. The Meteorological Measurement System (MMS) was designed specifically for atmospheric research to provide accurate, fast response, in situ measurements of pressure, temperature, and the three dimensional wind vector. The MMS consists of three subsystems: an air motion sensing system to measure the velocity of the air with respect to the aircraft, a high resolution Inertial Navigation System (INS) to measure the velocity of the aircraft with respect to the Earth, and a Data Acquisition System, to sample, process and record the measured quantities. Details of each of these systems are given. The location of the MMS instrumentation is illustrated. The calibration of the MMS is discussed and results on an intercomparison of MMS measurements, Vaisala radiosonde observation and radar tracking data are given. An illustration of the MMS measurement of vertical wind is given.

Chan, K. Roland↗
NASA NTRS1990

Data analysis and archival

The purpose of this task is the acquisition, distribution, archival, and analysis of data collected during and in support of the Upper Atmospheric Research Program (UARP) field experiments. Meteorological and U2 data from the 1984 Stratosphere-Troposphere Exchange Project (STEP) was analyzed to determine characteristics of internal atmospheric waves. CDROM's containing data from the 1987 STEP, 1987 Airborne Antarctic Ozone Expedition (AAOE), and the 1989 Airborne Arctic Stratospheric Expedition (AASE) were produced for archival and distribution of those data sets. The AASE CDROM contains preliminary data and a final release is planned for February 1990. Comparisons of data from the NASA ER-2 Meteorological Measurement System (MMS) with radar tracking and radiosonde data show good agreement. Planning for a Meteorological Support Facility continues. We are investigating existing and proposed hardware and software to receive, manipulate, and display satellite imagery and standard meteorological analyses, forecasts, and radiosonde data.

Danielsen, Edwin F.↗
NASA NTRS1990

Radiative heating rates during AAOE and AASE

Radiative transit computations of heating rates utilizing data from the 1987 Airborne Antarctic Ozone Experiment (AAOE) (Tuck et al., 1989) and the 1989 Airborne Arctic Stratospheric Experiment (AASE) (Turco et al., 1990) are described. Observed temperature and ozone profiles and a radiative transfer model are used to compute the heating rates for the Southern Hemisphere during AAOE and the Northern Hemisphere during AASE. The AASE average cooling rates computed inside the vortex are in good agreement with the diabatic cooling rates estimated from the ER-2 profile data for N2O for the AASE period (Schoeberl et al., 1989).

Rosenfield, Joan E.↗
NASA NTRS1990

Remote measurements of the structure of midwest thunderstorm tops and anvils from high altitude aircraft

Results are presented from observations by a visible and IR scanning radiometer, a scanning passive microwave radiometer, and a nadir-viewing cloud lidar system (CLS), carried out from ER-2 overflights for two midwest severe weather events both of which presented following phenomena: (1) a group of severe thunderstorms which later transformed into a linear mesoscale convective system, and (2) a severe thunderstorm which produced large hail. Most of the aircraft in situ and remote measurements pointed to a deep subsidence region and gravity waves downstream of the overshooting cloud tops. The observations do not support a radiative explanation for the warm areas in the anvil.

Heymsfield, Gerald M.↗