Abstract
Abstract. A low-cost miniaturized particle counter has been developed by The University of Hertfordshire (UH) for the measurement of aerosol and droplet concentrations and size distributions. The Universal Cloud and Aerosol Sounding System (UCASS) is an optical particle counter (OPC), which uses wide-angle elastic light scattering for the high-precision sizing of fluid-borne particulates. The UCASS has up to 16 configurable size bins, capable of sizing particles in the range 0.4–40 µm in diameter. Unlike traditional particle counters, the UCASS is an open-geometry system that relies on an external air flow. Therefore, the instrument is suited for use as part of a dropsonde, balloon-borne sounding system, as part of an unmanned aerial vehicle (UAV), or on any measurement platform with a known air flow. Data can be logged autonomously using an on-board SD card, or the device can be interfaced with commercially available meteorological sondes to transmit data in real time. The device has been deployed on various research platforms to take measurements of both droplets and dry aerosol particles. Comparative results with co-located instrumentation in both laboratory and field settings show good agreement for the sizing and counting ability of the UCASS.
Highlights
Atmospheric aerosols are a key component in the Earth’s radiative system as they modify the local and planetary albedo by way of direct and indirect effects
The width of this pulse is equal to the time of flight (ToF) of the particle across the beam, and the height of this pulse corresponds to the maximum intensity incident upon the detector during this transit
To constrict the movement of the Universal Cloud and Aerosol Sounding System (UCASS), the payload is configured as a double pendulum, whereby the UCASS is secured by a line below the balloon and the meteorological sonde is secured below the UCASS
Summary
Atmospheric aerosols are a key component in the Earth’s radiative system as they modify the local and planetary albedo by way of direct and indirect effects. To cover large geographical scales, there exists an array of measurements from ground-based sun photometer networks (Holben et al, 1998; Che et al, 2009; Bokoye et al, 2002) to satellite-based instruments (Huete, 2004; Chu et al, 2003; Kaufman et al, 1997; Zhang and Christopher, 2003; Jiao et al, 2018) This combination of instruments provides near-continuous measurements worldwide and yields direct measurements of aerosol properties, such as aerosol optical depth (AOD), and inferred properties, such as number concentration and size distribution. Resolved in situ data are typically gathered with aircraft-based instrumentation during research campaigns These campaigns employ a variety of instruments for particle measurement: from single-scattering particle probes for the counting and sizing of small particles, optical array probes for the imaging of larger particles, and filters to collect samples for in-depth chemical analysis. Due to the relative ease and affordability of radiosoundings, the UCASS offers an alternative to aircraft-based measurements with fewer time and space restrictions
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