An optical particle size spectrometer for aircraft-borne measurements in IAGOS-CARIBIC

Abstract

Abstract. The particle number size distribution is an important parameter to characterize the atmospheric aerosol and its influence on the Earth's climate. Here we describe a new optical particle size spectrometer (OPSS) for measurements of the accumulation mode particle number size distribution in the tropopause region on board a passenger aircraft (IAGOS-CARIBIC observatory: In-service Aircraft for a Global Observing System -Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container). A modified KS93 particle sensor from RION Co., Ltd., together with a new airflow system and a dedicated data acquisition system, is the key component of the CARIBIC OPSS. The instrument records individual particle pulse signal curves in the particle size range 130-1110 nm diameter (for a particle refractive index of 1.47-i0.006) together with a time stamp and thus allows the post-flight choice of the time resolution and the size distribution bin width. The CARIBIC OPSS has a 50 % particle detection diameter of 152 nm and a maximum asymptotic counting efficiency of 98 %. The instrument's measurement performance shows no pressure dependency and no particle coincidence for free tropospheric conditions. The size response function of the CARIBIC OPSS was obtained by a polystyrene latex calibration in combination with model calculations. Particle number size distributions measured with the new OPSS in the lowermost stratosphere agreed within a factor of 2 in concentration with balloon-borne measurements over western North America. Since June 2010 the CARIBIC OPSS is deployed once per month in the IAGOS-CARIBIC observatory.

Particulate sulfur in the upper troposphere and lowermost stratosphere – sources and climate forcing

“…This study is based on measurements of particulate sulfur taken from the IAGOS-CARIBIC platform (Brenninkmeijer et al, 2007;www.caribic-atmospheric.com/), where the atmosphere is studied using modified passenger aircraft (March 1999-April 2002: Boeing 767-300 ER from LTU International Airways; May 2005-present: Airbus 340-600 from Lufthansa) during monthly sets of usually four intercontinental flights. A large number of trace gases and aerosol parameters are measured from this platform during flights in the altitude range 8.8-12 km, including gaseous and con-densed water, O 3 , CO, NO/NO y , volatile organic compounds (VOCs), greenhouse gases, halo-carbons, mercury, particle number concentrations, size distributions and elemental concentrations (Brenninkmeijer et al, 2007;Hermann et al, 2003;Schuck et al, 2009;Baker et al, 2010;Oram et al, 2012;Zahn et al, 2012;Martinsson et al, 2014;Dyroff et al, 2015;Slemr et al, 2016;Hermann et al, 2016).…”

“…Upper troposphere particulate sulfur, in addition, has tropospheric sources. In the tropics, convection lofts aerosol and aerosol precursor gases from low altitudes into the UT (Hess, 2005). During the monsoon season, primarily the Asian monsoon, appreciable amounts of aerosol and gaseous aerosol precursors are lifted to the tropopause region, extending from the UT to approximately 420 K potential temperature in the stratosphere, forming the Asian tropopause aerosol layer (ATAL; Vernier et al, 2011b).…”

Atmospheric mercury measurements onboard the CARIBIC passenger aircraft

“…Typically, a sequence of four individual flights is flown every month. A modified freight container holds automated analysers for gaseous mercury, CO, O 3 , NO, NO y , CO 2 , total and gaseous water vapour, oxygenated organic compounds, and fine particles (three counters for particles with diameters > 4, > 12, and > 18 nm), as well as one optical particle size spectrometer for particles with diameters > 140 nm (Hermann et al, 2016). In addition, air and aerosol particle samples are taken and analysed after the flight for greenhouse gases, halocarbons, hydrocarbons, and particle elemental composition and morphology .…”

On the parametrization of optical particle counter response including instrument-induced broadening of size spectra and a self-consistent evaluation of calibration measurements

“…In order to derive a size distribution uncertainty estimate from uncertainties in the particle properties, however, most studies follow the pragmatic approach and report the maximum impact on the size distribution as a conservative estimate (e.g., Osborne et al, 2008;Weinzierl et al, 2009;Brock et al, 2011;Ryder et al, 2013;Hermann et al, 2016). However, the size distribution uncertainty induced by the uncertainties in the particle properties can be substantially size dependent.…”

“…The initial PSL particle size distributions, which are traceable via the United States National Institute of Standards and Technology (NIST), are of Gaussian shape with known mean and standard deviation. Although they are narrower than the width of the DMA transfer functions, additional DMA filtering helped to effectively remove the interfering background at smaller particle diameters than are caused by the nebulization (see Hermann et al, 2016). For mean particle diameters larger than 800 nm the presented counting histograms are empirically separated from this background.…”