Search results for "Liquid water content"

Partitioning of Aerosol Particles in Mixed-phase Clouds at a High Alpine Site

2007

6 German Aerospace Centre, D-82234, Wessling, Germany * Now at Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland Abstract The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3,580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the scavenged fraction of aerosol particles, F Scav , and of black carbon, F Scav,BC . They denote the fraction of the aerosol volume con…

Impact of cloud processes on aerosol particle properties: results from two ATR-42 flights in an extended stratocumulus cloud layer during the EUCAARI…

2011

Abstract. Within the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Meteo France research aircraft ATR-42 was operated from Rotterdam airport during May 2008, to perform scientific flights dedicated to the investigation of aerosol-cloud interactions. Therein, the objective of this study is to illustrate the impact of cloud processing on the aerosol particles physical and chemical properties. The presented results are retrieved from measurements during a double-flight mission from Rotterdam (Netherlands) to Newcastle (UK) and back using data measured with compact Time of Flight Aerosol Mass Spectrometer (cToF-AMS) and Scanning Mobility Particle Sizer (SMPS…

A Radiation Fog Model with a Detailed Treatment of the Interaction between Radiative Transfer and Fog Microphysics

1990

Abstract A one-dimensional radiation fog model is presented which includes a detailed description of the interaction between atmospheric radiative transfer and the microphysical structure of the fog. Aerosol particles and activated cloud droplets are treated using a two-dimensional joint size distribution whereby the activation process of aerosols is explicitly modeled. For this purpose a new positive definite semi-Lagrangian advection scheme is developed that produces only small numerical diffusion and is numerically very efficient. For the radiative calculations, time dependent attenuation parameters are determined from the actual particle size distributions. The diffusional growth of the…

Cloud and Fog Effects and Their Parameterisation in Regional Air Quality Models

1997

For the special purpose of cloud chemistry a tool ASOCC was developed which is able to generate a differential equation system from a given set of chemical kinetics equations. Sensitivity and structure analysis have been performed to evaluate the great number of investigated reactions in the liquid phase and to derive a condensed mechanism for use in regional chemistry-transport models.

Effects of organic aerosol constituents on extinction and absorption coefficients and liquid water contents of fogs and clouds

1978

We have speculated on the influence of organic material on extinction and absorption coefficients and liquid water content of fogs and of clouds immediately after their condensational stage. It results therefore, that the reduction of the speed of growth from fog to cloud droplets due to the presence of organic films largely reduces the properties mentioned. Compared to that their increase coming from the surface tension reduction due to organic material being dissolved or building up films is expected to be less effective.

2014

Abstract. This study uses the EMAC atmospheric chemistry-climate model to simulate cloud properties and estimate cloud radiative effects induced by aerosols. We have tested two prognostic cloud droplet nucleation parameterizations, i.e., the standard STN (osmotic coefficient model) and hybrid (HYB, replacing the osmotic coefficient by the κ hygroscopicity parameter) schemes to calculate aerosol hygroscopicity and critical supersaturation, and consider aerosol–cloud feedbacks with a focus on warm clouds. Both prognostic schemes (STN and HYB) account for aerosol number, size and composition effects on droplet nucleation, and are tested in combination with two different cloud cover parameteriz…

Ultrathin Tropical Tropopause Clouds (UTTCs): II. Stabilization mechanisms

2003

Abstract. Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10-4 have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200-300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1-5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work sugges…