Wind Tunnel Measurements of the Response of Hot-Wire Liquid Water Content Instruments to Large Droplets

Strapp, J. W.; Oldenburg, John R.; Ide, Robert F.; Lilie, Lyle; Bacic, S.; Vukovic, Zlatko R.; Oleskiw, Myron; Miller, Donald B.; Emery, Edward; Leone, Guido

doi:10.1175/1520-0426(2003)020<0791:wtmotr>2.0.co;2

Cited by 65 publications

(77 citation statements)

References 22 publications

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“…The collection efficiency of the Nevzorov TWC sensor for drizzle-size droplets is close to unity, as was demonstrated in wind tunnel testing at the NASA Icing Research Tunnel . Furthermore, Strapp et al (2003) presented a detailed study of Nevzorov LWC and TWC sensor response with respect to large-droplet conditions (Fig. 5).…”

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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“…); error bars are root mean squared error. Green hatched areas are estimates of expected percent LWC difference using droplet generator results computed for errors in CDP sizing and counting for 10% and 90% count thresholds and errors considering best estimates of Nevzorov collection efficiency as a function of VMD (from Korolev et al, 1998;Strapp et al, 2003;5 Schwarzenboeck et al, 2009). Plots are shown for 4 ranges of total droplet concentration.…”

Section: In-situ Resultsmentioning

confidence: 99%

“…al, 2017). The Nevzorov probe features reference elements that are positioned on the devices' trailing edge such that they are aerodynamically shielded from particle impact (Korolev et al, 1998;Strapp et al, 2003). Energy losses from the reference elements are then assumed to arise solely due to convective considerations and thus the total power delivered to the reference elements can be used to estimate the convective heat losses 20 from the sensing (collector) elements.…”

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confidence: 99%

Laboratory and In-flight Evaluation of a Cloud Droplet Probe (CDP)

Faber¹,

French²,

Jackson³

2018

Preprint

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Abstract. Laboratory and in-flight evaluations of measurements from a Cloud Droplet Probe (CDP) are presented. A description of a water droplet-generating device, similar to those used in previous studies, is provided along with validation of droplet sizing and positioning. Laboratory evaluations of a CDP using the droplet generating system indicate errors in sizing that depend on both droplet diameter and position within the sample area through which a droplet transited. For the 10 smallest diameters tested, the CDP undersized droplets by 1 -4 µm for the majority of those sampled. The remaining droplets were sized to within 1 µm of the actual diameter. Droplets with diameters of 17 and 24 µm were sized correctly, within 2 µm, which is the nominal CDP bin width for droplets of that size. For all larger diameters, the majority of droplets were oversized by 2 -4 µm, while a small percentage were severely undersized, by as much as 30 µm. This combination leads to an artificial broadening of the spectra, although errors in higher order moments were generally less than 10%. 15Comparisons of liquid water content (LWC) calculated from the CDP and that measured from a Nevzorov hotwire probe were conducted for 17,917 1 Hz in-cloud points. Although some differences were noted based on volume-weighted mean diameter and total droplet concentration, the CDP-estimated LWC exceeded that measured by the Nevzorov by approximately 20%, more than twice the expected difference based on results of the laboratory tests and considerations of Nevzorov collection efficiency. 20

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“…1 The term "total water content" is used with two conflicting meanings in the atmospheric instrumentation literature: it is used either to designate the condensed water content (ice + liquid water phases only) or to designate the water content in these condensed phases plus that in water vapor. For example, the hot-wire Nevzorov probe has a sensor with conical geometry designed to measure the liquid and/or ice water content of clouds (Korolev et al, 1998); the measurements made with this sensor are often referred to as "total water content" (e.g., Cober et al, 2001;Strapp et al, 2003;Boudala et al, 2004, Baumgardner et al, 2011, although these measurements by design exclude water vapor. Alternately, authors working with evaporative hygrometers refer to the measured sum of condensed water plus ambient water vapor as the "total water" (e.g., Brown and Francis, 1995;Wood and Field, 2000;Davis et al, 2007b).…”

Section: Instrument Designmentioning

confidence: 99%

A fiber-coupled laser hygrometer for airborne total water measurement

et al. 2014

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Abstract. The second-generation University of Colorado closed-path tunable-diode laser hygrometer (CLH-2) is an instrument for the airborne in situ measurement of total water content -the sum of vapor-, liquid-and ice-phase waterin clouds. This compact instrument has been flown on the NSF/NCAR Gulfstream-V aircraft in an underwing canister. It operates autonomously and uses fiber-coupled optics to eliminate the need for a supply of dry compressed gas. In operation, sample air is ingested into a forward-facing subisokinetic inlet; this sampling configuration results in particle concentrations that are enhanced relative to ambient and causes greater instrument sensitivity to condensed water particles. Heaters within the inlet vaporize the ingested water particles, and the resulting augmented water vapor mixing ratio is measured by absorption of near-infrared light in a single-pass optical cell. The condensed water content is then determined by subtracting the ambient water vapor content from the total and by accounting for the inertial enhancement of particles into the sampling inlet. The CLH-2 is calibrated in the laboratory over a range of pressures and water vapor mixing ratios; the uncertainty in CLH-2 condensed water retrievals is estimated to be 14.3 % to 16.1 % (1-σ ). A vapor-only laboratory intercomparison with the firstgeneration University of Colorado closed-path tunable-diode laser hygrometer (CLH) shows agreement within the 2-σ uncertainty bounds of both instruments.

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Wind Tunnel Measurements of the Response of Hot-Wire Liquid Water Content Instruments to Large Droplets

Cited by 65 publications

References 22 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

Laboratory and In-flight Evaluation of a Cloud Droplet Probe (CDP)

A fiber-coupled laser hygrometer for airborne total water measurement

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