Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: J. C. Carstens x
  • Refine by Access: All Content x
Clear All Modify Search
J. C. Carstens

Abstract

No abstract available.

Full access
A. Williams and J. C. Carstens

Abstract

No abstract available.

Full access
J. C. Carstens and J. J. Martin

Abstract

The role of phoretic forces in providing an in-cloud scavenging mechanism is examined for the case of an evaporating cloud drop. A formula is presented which describes the coupled effects of diffusion and thermo- and diffusiophoresis around a stationary drop. Under those circumstances where the phoretically-induced collection dominates diffusion, the formula suggests that, regardless of the undersaturation experienced by the drop, causing it to evaporate, phoretic effects tend to be independent of their driving force. Such circumstances are also identified for the case of a failing cloud drop.

Full access
D. J. Alofs and J. C. Carstens

Abstract

The performance of the conventional horizontal plate thermal diffusion chamber as a cloud nucleus counter was studied. Numerical calculations were performed in order to follow the simultaneous drop growth and sedimentation in the spatially and temporally nonuniform supersaturation field. The effect of nuclei distribution and smallest detectable drop size were investigated. The results indicate order of magnitude uncertainty in the count at 0.1% supersaturation, and a factor of 2 uncertainty at 1.0% supersaturation.

Full access
J. C. Carstens, J. Podzimek, and A. Saad

Abstract

The theory of the growth (or evaporation) of a stationary drop has been cast into a form which reveals explicitly the role of both condensation and thermal accommodation coefficients. The equations for growth are integrated under constant ambient conditions. An application to cloud physics is discussed.

Full access
B. F. Ryan and J. C. Carstens

Abstract

A simple parcel model has been used to examine the possibility that observed profiles of θe following the passage of a squall line are produced by air originating in middle-level clouds and descending in steady rain. The model predicts realistic profiles of θ and q.

The calculations suggest that in meteorological situations such as squall lines the thermodynamic properties of air associated with evaporating downdrafts can be parameterized by this simple model.

Full access
A. M. Sinnarwalla, D. J. Alofs, and J. C. Carstens

Abstract

Growth rate measurements were made for water drops grown on nuclei in atmospheric air samples taken in Rolla, Missouri. Rolla, having a population of 15,000 and very little industry, is relatively free of urban pollutants. The measurements were made in a vertical flow thermal diffusion chamber at supersaturations of 0.5 and 1%. The time to grow from near dry radius to the final radius (6 to 7.5 µm) was measured. If one assumes the thermal accommodation coefficient is unity, the measurements indicate an average value of 0.026 for the condensation coefficient. The temperature ranged from 22.5 to 25.7°C.

Full access
Annmarie G. Carlton, Joost de Gouw, Jose L. Jimenez, Jesse L. Ambrose, Alexis R. Attwood, Steven Brown, Kirk R. Baker, Charles Brock, Ronald C. Cohen, Sylvia Edgerton, Caroline M. Farkas, Delphine Farmer, Allen H. Goldstein, Lynne Gratz, Alex Guenther, Sherri Hunt, Lyatt Jaeglé, Daniel A. Jaffe, John Mak, Crystal McClure, Athanasios Nenes, Thien Khoi Nguyen, Jeffrey R. Pierce, Suzane de Sa, Noelle E. Selin, Viral Shah, Stephanie Shaw, Paul B. Shepson, Shaojie Song, Jochen Stutz, Jason D. Surratt, Barbara J. Turpin, Carsten Warneke, Rebecca A. Washenfelder, Paul O. Wennberg, and Xianling Zhou

Abstract

The Southeast Atmosphere Studies (SAS), which included the Southern Oxidant and Aerosol Study (SOAS); the Southeast Nexus (SENEX) study; and the Nitrogen, Oxidants, Mercury and Aerosols: Distributions, Sources and Sinks (NOMADSS) study, was deployed in the field from 1 June to 15 July 2013 in the central and eastern United States, and it overlapped with and was complemented by the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. SAS investigated atmospheric chemistry and the associated air quality and climate-relevant particle properties. Coordinated measurements from six ground sites, four aircraft, tall towers, balloon-borne sondes, existing surface networks, and satellites provide in situ and remotely sensed data on trace-gas composition, aerosol physicochemical properties, and local and synoptic meteorology. Selected SAS findings indicate 1) dramatically reduced NOx concentrations have altered ozone production regimes; 2) indicators of “biogenic” secondary organic aerosol (SOA), once considered part of the natural background, were positively correlated with one or more indicators of anthropogenic pollution; and 3) liquid water dramatically impacted particle scattering while biogenic SOA did not. SAS findings suggest that atmosphere–biosphere interactions modulate ambient pollutant concentrations through complex mechanisms and feedbacks not yet adequately captured in atmospheric models. The SAS dataset, now publicly available, is a powerful constraint to develop predictive capability that enhances model representation of the response and subsequent impacts of changes in atmospheric composition to changes in emissions, chemistry, and meteorology.

Open access