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Rosen, J. M.

Publications and source records attributed to Rosen, J. M..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

On the temporal variation of stratospheric aerosol size and mass during the first 18 months following the 1982 eruptions of El Chichon

Baloon-borne particle counters at Laramie and in southern Texas are used to investigate the size and mass distribution of the aerosol which formed in the stratosphere during the first 18 months following the volcanic eruption of El Chichon. The latter appears to have reached a peak at Laramie in early 1983 and began a decline in May. Measurements of average aerosol radius versus time are used to estimate a sulfuric acid concentration of about 10 to the 7th per cu cm 40 days after the eruption and a net acid vapor lifetime of 25-50 days in the 18-25-km altitude region.

Hofmann, D. J.↗
NASA NTRS1984

Satellite and correlative measurements of the stratospheric aerosol. III - Comparison of measurements by SAM II, SAGE, dustsondes, filters, impactors and lidar

The SAM II and SAGE satellite sensors, dustsondes, impactors, a filter collector and an airborne lidar were used in a large satellite validation experiment on July 16-19, 1979, at Poker Flat, Alaska. Independent measurements of extinction profiles by SAM II and SAGE are noted to agree with each other and with those derived from the other instruments (within combined uncertainties). The wire impactor-derived results, while also consistent with the others, are coarse due to the relatively large uncertainties in impactor-derived mass, extinction, and number of particles/unit volume whose radius is greater than x microns.

Russell, P. B.↗
NASA NTRS1983

The El Chichon volcanic cloud - An introduction

Background information on the El Chichon volcanic cloud is provided, and coordinated observational campaigns designed to investigate the El Chichon cloud are described. An introduction is then given to the set of papers about the El Chichon cloud in Geophysical Research Letters, volume 10, number 11. Topics discussed include in situ measurements of the size distribution of the volcanic aerosols, high resolution size measurements, the spatial and temporal evolution of the cloud, and the optical properties of the cloud.

Danielsen, E. F.↗
NASA NTRS1983

Unusual behavior in the condensation nuclei concentration at 30 km

The result obtained with an improved balloon-borne condensation nuclei (CN) counter that is capable of operating to altitudes of at least 30 km are presented. Of major interest is the appearance of a quasiannual variation near 30 km which could be described by a sudden concentration increase of unusually small particles occurring in the winter or spring followed by a 1- to 3-month decay period to background levels. The magnitude of the variation has increased dramatically following the recent generally high levels of volcanic activity affecting the lower stratosphere. Several potential explanations for the event are considered, but none appear entirely satisfactory or complete at the present time. The explanation with the fewest drawbacks would attribute the production of growth of the new cn to a highly supersaturated H2SO4 vapor layer generated by any one of several proposed processes in the upper high latitude stratosphere.

Rosen, J. M.↗
NASA NTRS1983

Lidar- and balloon-borne particle counter comparisons following recent volcanic eruptions

Balloon-borne particle counter measurements at Laramie, Wyoming (41 deg N) are used to calculate the expected lidar backscatter at 0.694 micron wavelength from July 1979 to February 1982, a period which included at least four detectable perturbations of the stratospheric aerosol layer due to volcanic eruptions. These calculations are compared with lidar measurements conducted at Garmisch-Partenkirchen (47.5 deg N) during the same period. While the agreement is generally good using only the main mode in the particle size distribution (radius about 0.07 micron) during approximately the first 6 months following a major volcanic eruption, a measured secondary mode near 1 micron radius, when included, improves the agreement. Calculations of the expected backscatter at 25-30 km reveal that substantial number of particles diffuse into this high altitude region about 7 months after a major eruption, and these particles should be taken into account when normalizing lidar at these altitudes.

Hofmann, D. J.↗
NASA NTRS1983

Condensation nuclei events at 30 km and possible influences of solar cosmic rays

Two recent observations have provided the basis for study of a relationship between solar activity and the formation of small particles in the earth's atmosphere; the discovery of annual increases of condensation nuclei (CN) at 30 km and the detection of sulfuric acid molecules in large negative ion clusters in the 25-35-km altitude region. These observations have led to formulation and testing of a model wherein CN are formed in a 'polar cloud chamber' supersaturated with sulfuric acid vapor and triggered by ionization associated with solar flare cosmic radiation. It is concluded that such a model provides a potential explanation of the observations.

Hofmann, D. J.↗
NASA NTRS1983

Stratospheric sulfuric acid fraction and mass estimate for the 1982 volcanic eruption of El Chichon

The stratospheric sulfuric acid fraction and mass for the 1982 volcanic eruptions of El Chichon are investigated using data from balloon soundings at Laramie (41 deg N) and in southern Texas (27-29 deg N). The total stratospheric mass of these eruptions is estimated to be approximately 8 Tg about 6.5 months after the eruption with possibly as much as 20 Tg in the stratosphere about 45 days after the eruption. Observations of the aerosol in Texas revealed two primary layers, both highly volatile at 150 C. Aerosol in the upper layer at about 25 km was composed of an approximately 80 percent H2SO4 solution while the lower layer at approximately 18 km was composed of a 60-65 percent H2SO4 solution aerosol. It is calculated that an H2SO4 vapor concentration of at least 3 x 10 to the 7th molecules/cu cm is needed to sustain the large droplets in the upper layer. An early bi-modal nature in the size distribution indicates droplet nucleation from the gas phase during the first 3 months, while the similarity of the large particle profiles 2 months apart shows continued particle growth 6.5 months after the explosion.

Hofmann, D. J.↗
NASA NTRS1983

Stratospheric condensation nuclei and possible solar influences

Balloon-borne measurements of condensation nuclei and H2SO4 molecules in large negative ion clusters have been made in the stratosphere at around 30 km altitude. The nuclei observed were in the 0.01-0.1 micron diameter range. Consideration was given to sunspot activity as a triggering event for ionization of upper atmospheric H2SO4 species and subsequent formation of the nuclei. A numerical model was defined for a steady state between the H2SO4 association and ion recombination in order to determine a critical nucleation rate. It is concluded that condensation nuclei are produced in ion nucleation in an H2SO4 supersaturated polar cloud chamber, with the process being initiated by solar flare particle ionization.

Hofmann, D. J.↗
NASA NTRS1982

Dustsonde measurements of the Mount St. Helens volcanic dust cloud over Wyoming

Numerous balloon soundings of the aerosol and condensation nuclei (CN) concentrations were made over Laramie, Wyoming following the eruption of Mount St. Helens in May of 1980. On several occasions the volatility of the particles was tested. In addition, special instrumentation was used to observe the evolution of particle size after the eruption. The particles in the initial cloud were relatively large and nonvolatile. In a relatively short time, however, the aerosol began showing a dominant volatile component. Although there were probably no CN in the original cloud due to the expected very short coagulation life time, high concentrations of unusually small CN particles were observed about a month after the eruption. By the end of September the CN profiles and associated particle size were practically back to normal. At present the aerosol particles show about a three times larger concentration than before the eruption, most of the new material being in a layer centered around 19 km. The net effect of the more recent series of eruptions during the last half of October 1980 seems to be negligible.

Rosen, J. M.↗
NASA NTRS1982

Stratospheric condensation nuclei variations may relate to solar activity

Observations of increases of stratospheric condensation nuclei suggest a photo-initiated sulphuric acid vapour formation process in spring in polar regions. It is proposed that the sulphuric acid rapidly forms condensation nuclei through attachment to negatively charged multi-ion complexes and that the process may be modulated through variations in solar activity.

Hofmann, D. J.↗
NASA NTRS1981

Satellite and correlative measurements of the stratospheric aerosol. II Comparison of measurements made by SAM II, dustsondes and airborne lidar

Results are shown from the first set of measurements conducted to validate extinction data from the Stratospheric Aerosol Measurement II (SAM II). Dustsonde-measured number density profiles and lidar-measured backscattering profiles for two days are converted to extinction profiles, and are shown to agree within their respective uncertainties at all heights above the tropopause. Near the tropopause, agreement depends on use of model size distributions with larger particles, having radii greater than 0.6 microns. The presence of such large particles is supported by measurements made elsewhere, is suggested by the in situ size distribution measurements reported, and is likely to have an important bearing on the radiative impact of the total stratospheric aerosol. It is concluded that the SAM II extinction data and uncertainty estimates are supported.

Russell, P. B.↗
NASA NTRS1980

A stratospheric aerosol increase

Large disturbances were noted in the stratospheric aerosol content in the midlatitude Northern Hemisphere commencing about 7 months after the eruption of La Soufriere and less than 1 month after the eruption of Sierra Negra. The aerosol was characterized by a very steep size distribution in the 0.15 to 0.25 micron radius range and contained a volatile component. Measurements near the equator and at the South Pole indicate that the disturbance was widespread. These observations were made before the May 18 eruption of Mt. St. Helens.

Rosen, J. M.↗
NASA NTRS1978

Vertical profiles of condensation nuclei

Condensation nuclei measurements using a low supersaturation (about 10%) thermal gradient diffusion cloud chamber (TGDCC) and a high supersaturation (about 200%) expansion type instrument were compared on a series of three balloon flights over Laramie, Wyoming. In general, the two instruments produced similar vertical profiles but some discrepancies remain unexplained. Agreement between the two would indicate that the low supersaturations used in the TGDCC were still large enough to cause the instrument to count essentially all of the particles present. The TGDCC condensation nuclei (CN) counter was flown at several sites in both the Northern and Southern Hemispheres. The results indicate the existence of a relative maximum in the CN mixing ratio associated with the upper equatorial troposphere and what appears to be a worldwide constant mixing ratio of CN above 20-25 km.

Rosen, J. M.↗
NASA NTRS1978

A steady-state stratospheric aerosol model

This paper deals with the development of a one-dimensional steady-state stratospheric aerosol model and the subsequent perturbations caused by including the expected Space Shuttle particulate effluents in the model. Two approaches to the basic modeling effort have been made: in one, enough simplifying assumptions were introduced so that a more or less exact solution to the descriptive equations could be obtained; in the other, very few simplifications were made and a computer technique was used to solve the equations. The most complete form of the model contains the effects of sedimentation, diffusion, particle growth and coagulation. The results indicate that the model is capable of describing many aspects of the stratospheric aerosol layer, such as size distribution and the vertical profile of particles greater than 0.3 micron diameter.

Rosen, J. M.↗
NASA NTRS1977

A stratospheric aerosol model with perturbations induced by the space shuttle particulate effluents

A one dimensional steady state stratospheric aerosol model is developed that considers the subsequent perturbations caused by including the expected space shuttle particulate effluents. Two approaches to the basic modeling effort were made: in one, enough simplifying assumptions were introduced so that a more or less exact solution to the descriptive equations could be obtained; in the other approach very few simplifications were made and a computer technique was used to solve the equations. The most complex form of the model contains the effects of sedimentation, diffusion, particle growth and coagulation. Results of the perturbation calculations show that there will probably be an immeasurably small increase in the stratospheric aerosol concentration for particles larger than about 0.15 micrometer radius.

Rosen, J. M.↗