Publication

Chemical and dynamical effects on cloud droplet number: Implications for estimates of the aerosol indirect effect

Athanasios Nenes
2004
Journal paper
Abstract

Most aerosol-cloud-climate assessment studies use empirical aerosol number/droplet number relationships, which are subject to large variability. Historically, this variability has been attributed to unresolved variations in updraft velocity. We revisit this postulation and assess the effects of both updraft velocity and chemical composition on this variability. In doing so we utilize an inverse modeling approach. Using a detailed numerical cloud parcel model and published aerosol characteristics, with published correlations of cloud droplet versus sulfate and cloud droplet versus aerosol number as constraints, we determine a most probable size distribution and updraft velocity for polluted and clean conditions of cloud formation. A sensitivity analysis is then performed to study the variation in cloud droplet number with changes in aerosol chemistry and updraft velocities. This addresses the need to estimate the importance of chemical effects on spatial scales relevant for global climate models. Our analysis suggests that the effect of organic surfactants can introduce as much variability in cloud droplet number as the effect of expected variations in updraft velocity. In addition, the presence of organics seems to further enhance the sensitivity of droplet concentration to vertical velocity variability. The variability from organic surfactants is seen to be insensitive to variations in aerosol number concentration, implying that such effects can affect cloud droplet number consistently over large spatial scales. Our findings suggest that organics can be as important to the aerosol indirect effect as the effect of unresolved cloud dynamics, and they illustrate the potential and complex role of chemical effects on aerosol-cloud interactions. Copyright 2004 by the American Geophysical Union.

About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Graph Chatbot

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.