Abstract. Terminology dealing with ice nucleation in the atmosphere, in biological systems, and in other areas has not kept pace with the growth of empirical evidence and the development of new ideas over recent decades. Ambiguities and misinterpretations could be seen in the literature. This paper offers a set of definitions for various terms in common use, adds some qualifications, and introduces some new ones. Input has been received on the interpretation of various terms from a fair number of researchers; diverse views have been accommodated with some success. It is anticipated that the terminology proposed here will be helpful both to those who adopt it and to those who wish to explain a different perspective.
Abstract. As part of a series of papers on the sources, distribution and potential impact of biological particles in the atmosphere, this paper introduces and summarizes the potential role of biological particles in atmospheric clouds. Biological particles like bacteria or pollen may be active as both cloud condensation nuclei (CCN) and heterogeneous ice nuclei (IN) and thereby can contribute to the initial cloud formation stages and the development of precipitation through giant CCN and IN processes. The paper gives an introduction to aerosol-cloud processes involving CCN and IN in general and provides a short summary of previous laboratory, field and modelling work which investigated the CCN and IN activity of bacterial cells and pollen. Recent measurements of atmospheric ice nuclei with a continuous flow diffusion chamber (CFDC) and of the heterogeneous ice nucleation efficiency of bacterial cells are also briefly discussed. As a main result of this overview paper we conclude that a proper assessment of the impact of biological particles on tropospheric clouds needs new laboratory, field and modelling work on the abundance of biological particles in the atmosphere and their CCN and heterogeneous IN properties.
Measurements in marine stratocumulus over the northeast Pacific help scientists unravel the mysteries of this important cloud regime.T he stratocumulus-topped boundary layer (hereafter the STBL), which prevails in the subtropics in regions where the underlying ocean is much colder than the overlying atmosphere, is thought to be an important component of the climate system. Perhaps most striking is its impact on the radiative balance at the top of the atmosphere. The seasonally averaged net cloud radiative forcing from the STBL has been estimated to be as large as 70 W nr 2 (Stephens and Greenwald 1991), more than an order of magnitude larger than the radiative forcing associated with a doubling of atmospheric C0 2 . This means that even rather subtle sensitivities of the STBL to changes in the properties of the atmospheric aero-
The development and improvement of cloud microphysical and radiative parameterizations for use in cloud and numerical weather prediction models. OBJECTIVES Detailed study of marine stratocumulus cloud microphysical and radiative processes using a high-resolution large eddy simulation (LES) model with explicit microphysics. Better understanding of interactions between microphysical, radiative and boundary layer thermodynamical processes in order to improve prediction of drizzle, marine stratocumulus cloud base height and visibility. Towards this goal, we investigate: 1) The dependence of drizzle on marine stratocumulus cloud microstructure 2) The effects of aerosol and moisture fluxes on cloud base height, drizzle, and visibility 3) Methods to characterize and formulate variability of cloud parameters for use in numerical forecast models APPROACH The research is based on a high-resolution LES model of marine boundary layer stratocumulus clouds with explicit formulation of aerosol and drop size-resolving microphysics. The LES simulations, as well as observations from ASTEX filed project were used to: 1) develop a drizzle parameterization for marine stratocumulus clouds, and 2) study the effects of aerosol and moisture fluxes on cloud base height and visibility. Measurements obtained by Millimeter Wave Cloud Radar (MMCR) have been used to study the variability of radar reflectivity in boundary layer stratocumulus and low altitude stratiform clouds. WORK COMPLETED The following tasks have been completed this year: 1. The development of a one-term drizzle parameterization for stratocumulus clouds in the range of drop concentration from 10 to 60 cm-3. 2. Analysis of over 50 LES simulations investigating the response of cloud base height, drizzle, and visibility range to the strength of CCN and moisture sources. 3. Analysis of the variability of boundary layer stratocumulus and low altitude stratiform clouds based on radar data collected over two years of observations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.