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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Balloon-borne observations of stratospheric aerosol in Antarctica from 1972 to 1984

Stratospheric levels of particles with r or = 0.15 microns were monitored with optical particle counters in approximately monthly balloon soundings at Laramie, Wyoming (41 deg N) since 1971. These measurements were used to characterize the background stratospheric aerosol layer and the disturbed layer following major volcanic eruptions. Levels of particles with r or = 0.01 microns have also been measured with balloon-borne counters since 1973. The latter are collectively called condensation nuclei (CN) as they are characteristic of aerosol in the early stages of growth. While they dominate the size distribution in the tropsophere, they are a trace species in the undisturbed stratosphere. From 1972 until 1980, annual balloon soundings from McMurdo Station (78 deg S) and/or Amundsen-Scott Station (90 deg S), in Antarctica, have also been conducted to crudely monitor Southern Hemisphere aerosol levels. These measurements were continued in 1983 and 1984. Profiles of r 0.15 microns aerosol concentrations as measured during January at the south pole from 1972 to 1975 and in 1980 are given. The former are typical of undisturbed conditions and indicate the small degree of variability under these conditions. The latter indicates the effect of minor volcanic activity, visible in the 10 to 15 km region.

Hofmann, D. J.↗
NASA NTRS1994

Condensation nuclei measurement in the stratosphere for the NASA ACE program

A condensation nucleus counter which operated at stratospheric pressures was developed, designed, and constructed. It was calibrated in the laboratory. Its response as a function of particle size and concentration was reported. This was the first time that the response of such an instrument was verified in the laboratory. An inlet was constructed which provided near isokinetic sampling. The resulting instrument, the U-2 CNC, was deployed on NASA U-2 aircraft in the study of the climatic effects of aerosol. These studies occurred in March, April, May, July, November, and December of 1992 and in April, May, June, and December of 1983. The U-2 CNC was used in the study of the aerosol cloud resulting from the eruption of El Chichon. It permitted the observation of new particle formation in the stratosphere.

Wilson, James Charles↗
NASA NTRS1979

Condensation-nuclei (Aitken Particle) measurement system used in NASA global atmospheric sampling program

The condensation-nuclei (Aitken particle) measuring system used in the NASA Global Atmospheric Sampling Program is described. Included in the paper is a description of the condensation-nuclei monitor sensor, the pressurization system, and the Pollack-counter calibration system used to support the CN measurement. The monitor has a measurement range to 1000 CN/cm cubed and a noise level equivalent to 5 CN/cm cubed at flight altitudes between 6 and 13 km.

Nyland, T. W.↗
NASA NTRS1989

Observations of condensation nuclei in the Airborne Antarctic Ozone Experiment - Implications for new particle formation and polar stratospheric cloud formation

This paper discusses the results of the ER-2 Condensation Nucleus Counter operated in the Airborne Ozone Experiment in August, September, and October 1987, providing data on the mixing ratio of aerosol condensation nuclei (CN) with diameters between about 0.02 and 1 micron. It is shown that the vertical profile of the CN mixing ratio is closely related to that of N2O, and that, between the -71 and -53 deg latitude, the location of the minima in the CN mixing ratio profile was near the 160 ppbv N2O isopleth, indicating that the processes of mixing and subsidence, which determine the inclination of that isopleth, also strongly affect the spatial distribution of the sulfate aerosol. Evidence for new sulfate particle formation is presented and related to the amount of subsidence experienced by air parcels in the formation of the polar vortex. Concentrations of CN are compared with those of larger particles (with diameters between 0.81 micron and 9.75 microns) to study polar stratospheric cloud formation mechanisms.

Wilson, J. C.↗
NASA NTRS1990

Measurements of condensation nuclei in the Airborne Arctic Stratospheric Expedition - Observations of particle production in the polar vortex

The ER-2 Condensation Nucleus Counter (ER-2 CNC) was operated in the Airborne Arctic Stratospheric Expedition (AASE) in January and February 1989. The ER-2 CNC measures the mixing ratio of particles, CN, with diameters from approximately 0.02 to approximately 1 micron. The spatial distribution of CN in the Arctic polar vortex was found to resemble that measured in the Antarctic in the Spring of 1987. The vertical profile of CN in the vortex was lowered by subsidence. At altitudes above the minimum in the CN mixing ratio profile, CN mixing ratios correlated negatively with that of N2O, demonstrating new particle production. CN serve as nuclei in the formation of Polar Stratospheric Clouds (PSCs) and the concentration of CN can affect PSC properties.

Wilson, J. C.↗
DOE OSTI2025

Fast and sensitive measurements of sub-3 nm particles using Condensation Particle Counters For Atmospheric Rapid Measurements (CPC FARM)

New particle formation (NPF) is the atmospheric process whereby gas molecules react and nucleate to form detectable particles. NPF has a strong impact on Earth's radiative balance as it produces roughly half of global cloud condensation nuclei. However, the time resolution and sensitivity of current instrumentation are inadequate in measuring the size distribution of sub-3 nm particles, the particles critical for understanding NPF. Here we present the Condensation Particle Counters For Atmospheric Rapid Measurements (CPC FARM), a method to measure the concentrations of freshly nucleated particles. The CPC FARM consists of five CPCs operating in parallel, each configured to operate at different detectable particle sizes between 1–3 nm. This study explores two methods to calculate the size distribution from the differential measurements across the CPC channels. The performance of both inversion methods was tested against the size distribution measured by a pair of stepping particle mobility sizers (SMPSs) during an ambient air sampling study in Pittsburgh, PA. Observational results indicate that the CPC FARM is more accurate with higher time resolution and sensitivity in the sub-3 nm range compared to the SMPS.

Cheng, Darren [Carnegie Mellon Univ., Pittsburgh, ↗
NASA NTRS1981

Simultaneous operation of three CCN counters and an isothermal haze chamber at the 1980 International CCN Workshop

Four devices were operated for the detection and characterization of cloud condensation nuclei (CCN) and fog condensation nuclei (FCN). In chronological order of development, the CCN devices are the conventional continuous-flow diffusion chamber (CFD), the rapid-cycle CCN spectrometer, and the instantaneous CCN spectrometer. The FCN detection device is an isothermal haze chamber (IHC). These four instruments are discussed and general comments on their performance at the workshop are given.

Hudson, J. G.↗
NASA NTRS1990

Aerosol measurements in the stratocumulus project

Cloud Condensation Nuclei (CCN) and Condensation Nuclei (CN) were measured from the National Center for Atmospheric Research (NCAR) Electra throughout the marine stratocumulus project. The total particle concentration was measured with a condensation nucleus counter. The CCN were measured with the Desert Research Institute (DRI) instantaneous CCN spectrometer. This instrument simultaneously measures the concentration of aerosol active at up to 100 different critical supersaturations (Sc). This is accomplished by exposing the sample to a fixed supersaturation field and using the size of the droplets produced in this cloud chamber to deduce the Sc of the nuclei upon which they have grown. Droplet size is associated with Sc through a calibration which is accomplished by passing soluble aerosols of known size and composition through the cloud chamber. This procedure results in a calibration curve of Sc vs. droplet size. This then allows the channel number to be directly associated with Sc. Thus, number concentration vs. Sc is obtained and this is a CCN spectrum. Since the instrument operates continuously, the measurements at all Sc's are available simultaneously. Samples are drawn directly from the ambient air and data is displayed in nearly real time. Samples were integrated over times of about 10 seconds so that substantial spatial resolution is available. Calibrations were performed once or twice a day and were found to be consistent. Preliminary results are shown.

Hudson, James G.↗
NASA NTRS1974

In situ measurement of particulate number density and size distribution from an aircraft

Commercial particulate measuring instruments were flown aboard the NASA Convair 990. A condensation nuclei monitor was utilized to measure particles larger than approximately 0.003 micrometers in diameter. A specially designed pressurization system was used with this counter so that the sample could be fed into the monitor at cabin altitude pressure. A near-forward light scattering counter was used to measure the number and size distribution particles in the size range from 0.5 to 5 micrometers and greater in diameter.

Briehl, D.↗
NASA NTRS1988

Aerosol measurements in the winter/spring Antarctic stratosphere. I - Correlative measurements with ozone. II - Impact on polar stratospheric cloud theories

Aerosol measurements collected from August 25-November 3, 1986 at McMurdo Station using balloon-borne optical particle counters are examined in order to study the relationship between aerosol and ozone distribution and the formation of polar stratospheric clouds (PSCs). Ozone, aerosol, and condensation nuclei profiles, and pressure, temperature, and humidity measurements are analyzed. It is observed that the height of the stratospheric sulfate layer decreases over the period of measurement suggesting that upwelling in the votex is not important in the zone depletion process. Three theories on PSC formation are described, and the effects of the aerosol measurements on the theories are considered. The three theories are: (1) the original theory of water vapor pressure over a solution of H2SO4 of Steele et al. (1983) and Hamill and Mc Master (1984); (2) the nitric acid theory of PSCs of Toon et al. (1986) and Hamill et al. (1986); and (3) the quasi-cirrus cloud theory of Heymsfield (1986).

Hofmann, D. J.↗
NASA NTRS1993

Twenty years of balloon-borne tropospheric aerosol measurements at Laramie, Wyoming

The paper examines the tropospheric aerosol record obtained over the period 1971 to 1990, during which high-altitude balloons with optical particle counters were launched at Laramie, Wyoming, in a long-term study of the stratospheric sulfate aerosol layer. All aerosol particle size ranges display pronounced seasonal variations, with the condensation nuclei concentration and the optically active component showing a summer maximum throughout the troposphere. Mass estimates, assuming spherical sulfate particles, indicate an average column mass between altitudes of 2.5 and 10 km of about 4 and 16 mg/sq m in winter and summer, respectively. Calculated optical depths vary between 0.01 and 0.04 from winter to summer; the estimated mass scattering cross section is about 3 sq m/g throughout the troposphere. There is evidence for a decreasing trend of 1.6-1.8 percent/yr in the optically active tropospheric aerosol over the past 20 yr, which may be related to a similar reduction in SO2 emission in the U.S. over this period.

Hofmann, David J.↗
NASA NTRS1994

Counting Condensation Nuclei in the Antarctic Ozone Mission

The work done on this grant primarily concerns the measurement of aerosol in the stratosphere from NASA ER-2 aircraft in studies of stratospheric ozone depletion in the northern and southern hemispheres. The ER-2 Condensation Nucleus Counter (CNC) measures the number concentration of particles in the diameter range of approximately 0.01 to 1 micron. The Passive Cavity Aerosol Spectrometer measures size distributions in the 0.17 to 3 micron diameter range. This instrument was upgraded during this grant period to a Focused Cavity Aerosol Spectrometer (FCAS). This upgrade permitted the instrument to measure particles as small as 0.05 micron in diameter. The inlet for the PCAS and FCAS was modified and characterized under this grant so that the modifications to the aerosol due to anisokinetic sampling and heating upon sampling and in transport to the measurement location were accounted for in the data analysis. These measurements permitted observations of particle production in the southern hemisphere winter polar vortex and observation of the impact of denitrification on the number concentration of the aerosol in the denitrified air. In the northern polar vortex, the measurements provided a characterization of the sulfate aerosol. Following the eruption of Mount Pinatubo in 1991, the measurements permitted an accurate characterization of the sulfate aerosol enhancements resulting from the eruption. This led to studies of the impact of heterogeneous chemistry on the partitioning of the partitioning of the reactive nitrogen species and the partitioning of the chlorine reservoir.

Wilson, James Charles↗
NASA NTRS1974

In situ measurements of particulate number density and size distribution from an aircraft

Two different commercial particulate measuring instruments were flown aboard the NASA Convair 990. A condensation nuclei monitor was utilized to measure particles larger than approximately 0.003 micron in diameter. A specially designed pressurization system was used with this monitor at cabin altitude pressure. A near-forward light scattering counter was used to measure the number and size distribution particles in the size range from 0.5 to 5 microns and greater in diameter. Considerable variation in number density was encountered for both classes of particles at the test altitudes ranging from 5 to 12 km. Presence of clouds could be detected by the light scattering instrument because large numbers of particles would then be registered by the instrument, especially in the size range above 5.0 microns in diameter.

Briehl, D.↗
NASA NTRS1998

Vertical Profiles of Cloud Condensation Nuclei, Condensation Nuclei, Optical Aerosol, Aerosol Optical Properties, and Aerosol Volatility Measured from Balloons

Under the support of this grant a balloon-borne gondola containing a variety of aerosol instruments was developed and flown from Laramie, Wyoming, (41 deg N, 105 deg W) and from Lauder, New Zealand (45 deg S, 170 deg E). The gondola includes instruments to measure the concentrations of condensation nuclei (CN), cloud condensation nuclei (CCN), optically detectable aerosol (OA.) (r greater than or equal to 0.15 - 2.0 microns), and optical scattering properties using a nephelometer (lambda = 530 microns). All instruments sampled from a common inlet which was heated to 40 C on ascent and to 160 C on descent. Flights with the CN counter, OA counter, and nephelometer began in July 1994. The CCN counter was added in November 1994, and the engineering problems were solved by June 1995. Since then the flights have included all four instruments, and were completed in January 1998. Altogether there were 20 flights from Laramie, approximately 5 per year, and 2 from Lauder. Of these there were one or more engineering problems on 6 of the flights from Laramie, hence the data are somewhat limited on those 6 flights, while a complete data set was obtained from the other 14 flights. Good CCN data are available from 12 of the Laramie flights. The two flights from Lauder in January 1998 were successful for all measurements. The results from these flights, and the development of the balloon-bome CCN counter have formed the basis for five conference presentations. The heated and unheated CN and OA measurements have been used to estimate the mass fraction of the aerosol volatile, while comparisons of the nephelometer measurements were used to estimate the light scattering, associated with the volatile aerosol. These estimates were calculated for 0.5 km averages of the ascent and descent data between 2.5 km and the tropopause, near 11.5 km.

Deshler, T.↗
DOE OSTI2025

A new technique to retrieve aerosol vertical profiles using micropulse lidar and ground-based aerosol measurements

Accurately characterizing the vertical distribution of aerosols and their cloud-forming properties is crucial for understanding aerosol-cloud interactions and their impact on climate. This study presents a novel technique for retrieving vertical profiles of aerosols, cloud condensation nuclei (CCN), and ice nucleating particles (INP) by combining micropulse lidar, radiosonde, and ground-based aerosol measurements. Herein, the technique is applied to data collected by our team at Texas A&M University during the Tracking Aerosol Convection Interactions ExpeRiment (TRACER) campaign. Ground-based aerosol size distribution and CCN counter data are used to estimate the value of the aerosol hygroscopicity parameter, κ. The derived κ, together with Mie scattering theory and the relative humidity profile from the radiosonde, is used to estimate aerosol size growth and the associated increase in backscatter at each altitude. We then correct the lidar backscatter to dry conditions to produce the dry aerosol backscatter coefficient profile. The dry aerosol backscatter coefficient profile is linearly scaled to collocated surface measurements of aerosols, CCN, and INP to produce corresponding vertical profiles. Combining lidar backscatter profiles with aerosol and cloud nucleation measurements leads to a more realistic representation of vertical distributions of aerosol properties. The method could be readily applied to lidar measurements in future field campaigns.

Chen, Bo [Texas A & M Univ., College Station, TX (↗
NASA NTRS2003

Toward Aerosol/Cloud Condensation Nuclei (CCN) Closure during CRYSTAL-FACE

During July 2002, measurements of cloud condensation nuclei were made in the vicinity of southwest Florida as part of the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign. These observations, at supersaturations of 0.2 and 0.85%, are presented here. The performance of each of the two CCN counters was validated through laboratory calibration and an in situ intercomparison. The measurements indicate that the aerosol sampled during the campaign was predominantly marine in character: the median concentrations were 233 cm-3 (at S = 0.2%) and 371 cm(sup -3) (at S = 0.85%). Three flights during the experiment differed from this general trend; the aerosol sampled during the two flights on 18 July was more continental in character, and the observations on 28 July indicate high spatial variability and periods of very high aerosol concentrations. This study also includes a simplified aerosol/CCN closure analysis. Aerosol size distributions were measured simultaneously with the CCN observations, and these data are used to predict a CCN concentration using Kohler theory. For the purpose of this analysis, an idealized composition of pure ammonium sulfate was assumed. The analysis indicates that in this case, there was good general agreement between the predicted and observed CCN concentrations: at S = 0.2%, N(sub predicted)/N(sub observed)= 1.047 (R(sup 2)= 0.911)); at S = 0.85%, N(sub predicted)/N(sub observed)=1.201 (R(sup 2)= 0.835)). The impacts of the compositional assumption and of including in-cloud data in the analysis are addressed. The effect of removing the data from the 28 July flight is also examined; doing so improves the result of the closure analysis at S = 0.85%. When omitting that atypical flight, N(sub predicted)/N(sub observed) = 1.085 (R(sup 2) = 0.770) at S = 0.85%.

VanReken, Timothy M.↗
NASA NTRS1980

Laboratory investigations of cloud nuclei from combustion of Space Shuttle propellant

Small quantities of solid rocket motor propellant, of the type to launch the Space Shuttle, were burned at ambient pressure in the laboratory to provide aerosol samples for characterization. A portion of each sample was injected into an isothermal cloud chamber and the remainder into a 770-liter holding tank. Portable ice nucleus (IN) counters, filter devices for IN determinations and a cloud condensation nucleus (CCN) counter sampled from the tank. The measurements show that particles resulting from the combustion of the propellant are active IN (3.3 times 10 to the 8th to 1.5 times 10 to the 11th/g active at 20 C). The portable counters and filters detected significantly fewer IN than the isothermal cloud chamber. The propellant aerosol is a prolific source of CCN that swamped the instrument.

Hindman Ii, E. E.↗
NASA NTRS2015

Investigation of the CCN Activity, BC and UVBC Mass Concentrations of Biomass Burning Aerosols during the 2013 BASELInE Campaign

Biomass-burning (BB) aerosols, acting as cloud condensation nuclei (CCN), can influence cloud microphysical and radiative properties. In this study, we present CCN measured near the BB source regions over northern Southeast Asia (Doi Ang Khang, Thailand) and at downwind receptor areas (Lulin Atmospheric Background Station, Taiwan), focusing exclusively on 13-20 March 2013 as part of 2013 spring campaign of the Seven SouthEast Asian Studies (7-SEAS) intensive observation. One of the campaigns objectives is to characterize BB aerosols serving as CCN in SouthEast Asia (SEA). CCN concentrations were measured by a CCN counter at 5 supersaturation (SS) levels: 0.15%, 0.30%, 0.45%, 0.60%, and 0.75%. In addition, PM2.5 and black carbon mass concentrations were analyzed by using a tapered element oscillating microbalance and an aethalometer. It was found the number-size distributions and the characteristics of hygroscopicity (e.g., activation ratio and k) of BB aerosols in SEA have a strong diurnal pattern, and different behaviors of patterns were characterized under two distinct weather systems. The overall average value was low (0.05-0.1) but comparable with previous CCN studies in other BB source regions. Furthermore, a large fraction of UV-absorbing organic material (UVBC) and high Delta-C among BB aerosols were also observed, which suggest the existence of substantial particulate organic matter in fresh BB aerosols. These data provide the most extensive characterization of BB aerosols in SEA until now.

biomass burning aerosol↗