Search Results

You are looking at 1 - 10 of 15 items for

  • Author or Editor: R. J. Charlson x
  • All content x
Clear All Modify Search
R. J. Charlson and M. J. Pilat

Abstract

Full access
R. J. Charlson and M. J. Pilat

Abstract

Full access
N. C. Ahlquist and R. J. Charlson

Abstract

While reliable instruments exist for measuring the dew point of air or other gases, few devices give an electrical signal that is an accurate function of relative humility (RT). The solid-state circuit described herein calculates RT with an accuracy of about ±1% RT via an electronic analog of the Clausius-Clapeyron equation.

Full access
R. F. Pueschel, R. J. Charlson, and N. C. Ahlquist

Abstract

Full access
R. F. Pueschel, R. J. Charlson, and N. C. Ahlquist

Abstract

Full access
D. S. Covert, R. J. Charlson, and N. C. Ahlquist

Abstract

A chemically pure aerosol of defined size distribution exhibits a unique growth pattern due to adsorption of water vapor, and to hygroscopic and/or deliquescence effects which are dependent upon relative humidity and which can be followed by measuring light scattering by the aerosol. A number of pure aerosols were produced artificially in the laboratory, subjected to a controlled humidity environment, and the magnitude of their light scattering coefficient measured continuously over a wide range of relative humidity (20–90%) with an integrating nephelometer. The results obtained can be applied to similar measurements on ambient air to yield qualitative chemical information and to determine the amount of visibility degradation which may be attributed to the association of water vapor with atmospheric aerosols. Examples of light scattering-relative humidity relationships for atmospheric aerosols are given.

Full access
R. J. Charlson, T. Silver, A. D. Clarke, and B. A. Bodhaine

Abstract

No abstract available.

Full access
F. Stratmann, A. Kiselev, S. Wurzler, M. Wendisch, J. Heintzenberg, R. J. Charlson, K. Diehl, H. Wex, and S. Schmidt

Abstract

In this paper, a new device is introduced to study the formation and growth of cloud droplets under near-atmospheric supersaturations. The new device, called the Leipzig Aerosol Cloud Interaction Simulator (LACIS), is based on a laminar flow tube. It has been designed to reproduce the thermodynamic conditions of atmospheric clouds as realistically as possible.

A series of experiments have been conducted that prove the definition and stability of the flow field inside the LACIS as well as the stability and reproducibility of the generated droplet size distributions as a function of the applied thermodynamic conditions. Measured droplet size distributions are in good agreement with those determined by a newly developed Eulerian particle–droplet dynamical model.

Further investigations will focus on the influences of latent heat release during vapor condensation on the tube walls and the development of a more suitable optical particle counter for droplet size determination.

Full access
J. E. Penner, R. J. Charlson, J. M. Hales, N. S. Laulainen, R. Leifer, T. Novakov, J. Ogren, L. F. Radke, S. E. Schwartz, and L. Travis

Anthropogenic aerosols are composed of a variety of aerosol types and components including water-soluble inorganic species (e.g., sulfate, nitrate, ammonium), condensed organic species, elemental or black carbon, and mineral dust. Previous estimates of the clear sky forcing by anthropogenic sulfate aerosols and by organic biomass-burning aerosols indicate that this forcing is of sufficient magnitude to mask the effects of anthropogenic greenhouse gases over large regions. Here, the uncertainty in the forcing by these aerosol types is estimated. The clear sky forcing by other anthropogenic aerosol components cannot be estimated with confidence, although the forcing by these aerosol types appears to be smaller than that by sulfate and biomass-burning aerosols.

The cloudy sky forcing by anthropogenic aerosols, wherein aerosol cloud condensation nuclei concentrations are increased, thereby increasing cloud droplet concentrations and cloud albedo and possibly influencing cloud persistence, may also be significant. In contrast to the situation with the clear sky forcing, estimates of the cloudy sky forcing by anthropogenic aerosols are little more than guesses, and it is not possible to quantify the uncertainty of the estimates.

In view of present concerns over greenhouse gas-induced climate change, this situation dictates the need to quantify the forcing by anthropogenic aerosols and to define and minimize uncertainties in the calculated forcings. In this article, a research strategy for improving the estimates of the clear sky forcing is defined. The strategy encompasses five major, and necessarily coordinated, activities: surface-based observations of aerosol chemical and physical properties and their influence on the radiation field; aircraft-based observations of the same properties; process studies to refine model treatments; satellite observations of aerosol abundance and size distribution; and modeling studies to demonstrate consistency between the observations, to provide guidance for determination of the most important parameters, and to allow extension of the limited set of observations to the global scale. Such a strategy, if aggressively implemented, should allow these effects to be incorporated into climate models in the next several years. A similar strategy for defining the magnitude of the cloudy sky forcing should also be possible, but the less firm understanding of this forcing suggests that research of a more exploratory nature be carried out before undertaking a research strategy of the magnitude recommended for the clear sky forcing.

Full access
J. J. DeLuisi, P. M. Furukawa, D. A. Gillette, B. G. Schuster, R. J. Charlson, W. M. Porch, R. W. Fegley, B. M. Herman, R. A. Rabinoff, J. T. Twitty, and J. A. Weinman

Abstract

The experimental results in Part I are used in the theoretical interpretation of the radiation flux measurements which were taken with an aircraft. The absorption term of the complex refractive index of aerosols is estimated to be approximately 0.01 for a real part of 1.5 for the wavelength bandwidth 0.32–0.68 μm. A regional variation in the refractive index is noted.

Atmospheric heating and cooling rates due to aerosol and molecular absorption in the solar and terrestrial wavelengths are determined from the radiation flux measurements. The magnitudes of these rates are compared and their relative importance is discussed.

Full access