Abstract
Abstract. A meteorological balloon-borne cloud sensor called the cloud particle sensor (CPS) has been developed. The CPS is equipped with a diode laser at ∼ 790 nm and two photodetectors, with a polarization plate in front of one of the detectors, to count the number of particles per second and to obtain the cloud-phase information (i.e. liquid, ice, or mixed). The lower detection limit for particle size was evaluated in laboratory experiments as ∼ 2 µm diameter for water droplets. For the current model the output voltage often saturates for water droplets with diameter equal to or greater than ∼ 80 µm. The upper limit of the directly measured particle number concentration is ∼ 2 cm−3 (2 × 103 L−1), which is determined by the volume of the detection area of the instrument. In a cloud layer with a number concentration higher than this value, particle signal overlap and multiple scattering of light occur within the detection area, resulting in a counting loss, though a partial correction may be possible using the particle signal width data. The CPS is currently interfaced with either a Meisei RS-06G radiosonde or a Meisei RS-11G radiosonde that measures vertical profiles of temperature, relative humidity, height, pressure, and horizontal winds. Twenty-five test flights have been made between 2012 and 2015 at midlatitude and tropical sites. In this paper, results from four flights are discussed in detail. A simultaneous flight of two CPSs with different instrumental configurations confirmed the robustness of the technique. At a midlatitude site, a profile containing, from low to high altitude, water clouds, mixed-phase clouds, and ice clouds was successfully obtained. In the tropics, vertically thick cloud layers in the middle to upper troposphere and vertically thin cirrus layers in the upper troposphere were successfully detected in two separate flights. The data quality is much better at night, dusk, and dawn than during the daytime because strong sunlight affects the measurements of scattered light.
Highlights
Clouds play various roles in the weather and climate through latent heat transport, precipitation and the hydrological cycle, and shortwave and longwave radiative processes
When the degree of polarization (DOP) value is more than ∼ 0.3, the particle is water in many cases, but there is a chance that it is ice; for the final judgement, the DOP statistics of the cloud layer to which the particle is belong and the simultaneous temperature value should be taken into account
For the first two flights, at Moriya, we used a version of cloud particle sensor (CPS) with the same instrumental configuration as for the PS2 and found that the lower detector part became highly contaminated after passing through supercooled cloud layers
Summary
Clouds play various roles in the weather and climate through latent heat transport, precipitation and the hydrological cycle, and shortwave and longwave radiative processes. A balloon-borne optical particle counter (OPC) has been used for studies on PSCs (Hayashi et al, 1998) and on cirrus clouds and aerosols in the tropical tropopause layer (Iwasaki et al, 2007; Shibata et al, 2012) This instrument uses an inlet tube and a gear pump to introduce air into a scattering cell where a laser diode and a silicon photodiode are used to characterize the size distribution of aerosol particles. The CPS uses the air flow associated with the balloon ascent or descent to introduce air into a detection area within the instrument where a diode laser and two photodetectors are used to count the number of cloud particles and to characterize their phase using the polarization information.
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