The Drop-Size Response of the CSIRO Liquid Water Probe

Biter, Cleon J.; Dye, J. E.; Huffman, Debra E.; King, W. D.

doi:10.1175/1520-0426(1987)004<0359:tdsrot>2.0.co;2

Cited by 70 publications

(34 citation statements)

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“…The Nevzorov LWC sensor with cylindrical sensor wire of 1.8 mm in diameter was found to measure solely 50% of the LWC at a median volume diameter of approximately 200 µm. Similar results were first shown by Biter et al (1987) for the King probe, another cylindrical hot wire like the Nevzorov LWC, and for various other cylindrical hot wires by Strapp et al (2003). The Nevzorov TWC sensor was found to agree within +/−20% of tunnel reference LWC across the entire tested range of MVD within 11-236 µm.…”

Section: Discussion Of the Sensor Efficiencies In Liquid Cloudsmentioning

confidence: 99%

Response of the Nevzorov hot wire probe in clouds dominated by droplet conditions in the drizzle size range

et al. 2009

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Abstract. During the airborne research mission ASTAR 2004 (Arctic Study of Tropospheric Aerosols, Clouds and Radiation) performed over the island of Svalbard in the Arctic a constant-temperature hot-wire Nevzorov Probe designed for aircraft measurements, has been used onboard the aircraft POLAR 2. The Nevzorov probe measured liquid water (LWC) and total condensed water content (TWC) in supercooled liquid and partly mixed phase clouds, respectively. As for other hotwire probes the calculation of LWC and/or TWC (and thus the ice water content IWC) has to take into account the collection efficiencies of the two separate sensors for LWC and TWC which both react differently with respect to cloud phase and what is even more difficult to quantify with respect to the size of ice and liquid cloud particles. The study demonstrates that during pure liquid cloud sequences the ASTAR data set of the Nevzorov probe allowed to improve the quantification of the collection efficiency, particularly of the LWC probe part with respect to water. The improved quantification of liquid water content should lead to improved retrievals of IWC content. Simultaneous retrievals of LWC and IWC are correlated with the asymmetry factor derived from the Polar Nephelometer instrument.

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Section: Discussion Of the Sensor Efficiencies In Liquid Cloudsmentioning

confidence: 99%

Response of the Nevzorov hot wire probe in clouds dominated by droplet conditions in the drizzle size range

et al. 2009

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“…However, hot-wire measurements have their own limitations; e.g. (1) they are limited to non-precipitating conditions, as their sensitivity declines appreciably and unpredictably for droplet sizes above ∼40 µm due to droplet splattering (Biter et al, 1987;Feind et al, 2000), (2) the collection of small droplets (<5 µm) is not 100% efficient (King et al, 1978), and (3) a percentage of the ice mass present in ice-only or mixed-phase clouds can be mistakenly attributed to liquid water. Thus, while hot-wire LWC measurements and optical cloud probe measurements are complementary to one another and should be flown together whenever possible, careful and detailed laboratory calibrations with water droplets are necessary for fundamental evaluation of a cloud droplet probe.…”

Section: Measurement Of Cloud Particlesmentioning

confidence: 99%

Water droplet calibration of the Cloud Droplet Probe (CDP) and in-flight performance in liquid, ice and mixed-phase clouds during ARCPAC

et al. 2010

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Abstract. Laboratory calibrations of the Cloud DropletProbe (CDP) sample area and droplet sizing are performed using water droplets of known size, generated at a known rate. Although calibrations with PSL and glass beads were consistent with theoretical instrument response, liquid water droplet calibrations were not, and necessitated a 2 µm shift in the manufacturer's calibration. We show that much of this response shift may be attributable to a misalignment of the optics relative to the axis of the laser beam. Comparison with an independent measure of liquid water content (LWC) during in-flight operation suggests much greater biases in the droplet size and/or droplet concentration measured by the CDP than would be expected based on the laboratory calibrations. Since the bias in CDP-LWC is strongly concentration dependent, we hypothesize that this discrepancy is a result of coincidence, when two or more droplets pass through the CDP laser beam within a very short time. The coincidence error, most frequently resulting from the passage of one droplet outside and one inside the instrument sample area at the same time, is evaluated in terms of an "extended sample area" (SA E ), the area in which individual droplets can affect the sizing detector without necessarily registering on the qualifier. SA E is calibrated with standardized water droplets, and used in a Monte-Carlo simulation to estimate the effect of coincidence on the measured droplet size distributions. The simulations show that extended coincidence errors are important for the CDP at droplet concentrations even as low as 200 cm −3 , and these errors are necessary to explain the trend between calculated and measured LWC observed in liquid and mixed-phase clouds during the Aerosol, RadiationCorrespondence to: S. Lance (sara.m.lance@noaa.gov) and Cloud Processes Affecting Arctic Climate (ARCPAC) study. We estimate from the simulations that 60% oversizing error and 50% undercounting error can occur at droplet concentrations exceeding 400 cm −3 . Modification of the optical design of the CDP is currently being explored in an effort to reduce this coincidence bias.

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“…Temperature and relative humidity ( RH ) were measured using a Rosemount 102 probe [ Lawson and Cooper , 1990] and EG&G chilled mirror hygrometer, respectively. Vertical gust velocities were determined from a Rosemount 858 gust probe (see Section 4 for discussion of associated uncertainty), and cloud LWC was measured using a Particle Measurement Systems (PMS) King hot‐wire probe [ King et al , 1978] considered to be accurate to within approximately ±15% for the relatively low values of r eff observed in this study [ Biter et al , 1987; King et al , 1985; Strapp et al , 2003]. Cloud droplet number concentration ( N d ) and size were measured using a Droplet Measurement Technologies (DMT) Cloud Droplet Probe (CDP) [ Lance et al , 2010; McFarquhar et al , 2007] or PMS Forward‐Scattering Spectrometer Probe (FSSP‐100) [ Knollenberg , 1976, 1981], which have size ranges of ∼2–50 μ m and ∼3–45 μ m (diameter), respectively.…”

Section: Approachmentioning

confidence: 99%

Factors influencing the microphysics and radiative properties of liquid-dominated Arctic clouds: Insight from observations of aerosol and clouds during ISDAC

et al. 2011

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[1] Aircraft measurements during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 are used to investigate factors influencing the microphysics and radiative properties of springtime Arctic clouds. The analysis is focused on low-level, liquid-dominated clouds in two separate regimes with respect to cloud and aerosol properties: single-layer stratocumulus with below-cloud aerosol concentrations (N a ) less than 250 cm −3 (clean cases); and layered stratocumulus with N a > 500 cm −3 below cloud base, associated with a biomass burning aerosol (polluted cases). For each regime, vertical profiles through cloud are used to determine cloud microphysical and radiative properties. The polluted cases were correlated with warmer, geometrically thicker clouds, with higher droplet number concentrations (N d ), liquid water paths (LWP), optical depths (t), and albedo (A) relative to clean cases. The mean cloud droplet effective radii (r eff ), however, were similar (5.7 mm) for both aerosol-cloud regimes. This discrepancy resulted mainly from the higher LWP of clouds in polluted cases, which can be explained by both meteorological (temperature, dynamics) and microphysical (precipitation inhibition) factors. Adiabatic parcel model simulations demonstrate that differences in droplet activation between the aerosol-cloud regimes may play a role, as the higher N a in polluted cases limits activation to larger and/or more hygroscopic particles. The observations and analysis presented here demonstrate the complex interactions among environmental conditions, aerosol, and the microphysics and radiative properties of Arctic clouds.

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The Drop-Size Response of the CSIRO Liquid Water Probe

Cited by 70 publications

References 0 publications

Response of the Nevzorov hot wire probe in clouds dominated by droplet conditions in the drizzle size range

Response of the Nevzorov hot wire probe in clouds dominated by droplet conditions in the drizzle size range

Water droplet calibration of the Cloud Droplet Probe (CDP) and in-flight performance in liquid, ice and mixed-phase clouds during ARCPAC

Factors influencing the microphysics and radiative properties of liquid-dominated Arctic clouds: Insight from observations of aerosol and clouds during ISDAC

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