Comparison of six H-TDMA systems: A laboratory study
Abstract
INTRODUCTION Hygroscopic properties of aerosol particles are crucial parameters for the determination of the understanding of the particle’s impact on regional and global climate. One of the most common methods to examine these properties is the H-TDMA (Hygroscopicity-Tandem Differential Mobility Analyzer) technique. The principle of the H-TDMA has been used for more than twenty years to investigate hygroscopic properties of submicrometer aerosol particles with high temporal resolution. In general, these systems are home-made set-ups and show substantial differences in technical details, used quality criteria, and applied data evaluation. METHODS A workshop comparing six European HTDMA systems was held in February 2006 at the Leibniz-Institute for Tropospheric Research in Leipzig, Germany. It was the aim of this study to intercompare the performance of those systems in terms of particle dry sizing, RH (Relative Humidity) control and RH stability (certainty of growth factor determination), and determination in observed number fractions in case of external mixtures. For this reason, four different experiments were prepared (Table 1).