Improved Airborne Hot-Wire Measurements of Ice Water Content in Clouds

Korolev, Alexei; Strapp, J. W.; Isaac, George A.; Emery, Edward

doi:10.1175/jtech-d-13-00007.1

Cited by 81 publications

(142 citation statements)

References 22 publications

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“…They showed that only a fraction of the mass of large (> 500 µm) ice particles is collected, with some of the particle debris leaving the cone. The Nevzorov TWC probe cone used here is the modified deep cone (60 • ), which has been shown (Korolev et al, 2008) to have improved collection efficiency. In order to calculate the TWC from the electrical energy supplied, the water phase must be known because of the extra energy required to melt ice.…”

Section: Instrumentationmentioning

confidence: 99%

“…Secondly, the small bulk ice water content obtained from collecting small ice can now be measured with sufficient sensitivity with a deep-cone Nevzorov probe. The earlier shallow-cone Nevzorov has been shown not to collect all ice particles (Korolev et al, 2008). A parametrization was developed for the Nevzorov Total Water Content (TWC) probe 'dry-air' baseline drift.…”

Section: Introductionmentioning

confidence: 99%

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The effective density of small ice particles obtained from in situ aircraft observations of mid‐latitude cirrus

Cotton

Field

Ulanowski

et al. 2012

Quart J Royal Meteoro Soc

157

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The effective ice-particle density, parametrized through a mass-dimension relation, is widely used in ice microphysical schemes for weather and climate models. In this study, we use aircraft-based observations in mid-latitude cirrus taken during the Constrain field programme in 2010. The low temperatures and a humidity often close to ice saturation meant that the typical ice particles observed were small (maximum dimension 20-800 µm) and ice water contents were low (0.001-0.05 g m −3 ). Two new instruments are included in this study: the Small Ice Detector Mark-2 (SID-2) and the deep-cone Nevzorov Total Water Content probe. SID-2 is a new singleparticle light-scattering instrument and was used to identify and size small ice particles (10-150 µm). The deep-cone Nevzorov probe is shown to be able to collect small ice masses with sufficient sensitivity. The focus of this article is on the effective density of small ice particles (both pristine ice crystals and small aggregates up to 600 µm maximum dimension). Due to instrument limitations in previous studies, the effective density of small ice particles is questionable.Aircraft flights in six cirrus cases provided ice-particle measurements throughout the depth of the cirrus. The particle size distribution (PSD) was mostly bimodal. The smaller ice-crystal mode dominated the PSD near cloud top and the larger ice-aggregate mode dominated near cloud base. A mass-dimension relation valid for both ice crystals and aggregates was found that provided a best fit to the observations. For small ice particles (less than 70 µm diameter) the density is constant (700 kg m −3 ), while for larger ice crystals or aggregates the mass-dimension relation is m(D) = 0.0257D 2.0 . These measurements allow testing of the diagnostic split between ice crystals and aggregates used in the Met Office Unified Model.

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Section: Instrumentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effective density of small ice particles obtained from in situ aircraft observations of mid‐latitude cirrus

Cotton

Field

Ulanowski

et al. 2012

Quart J Royal Meteoro Soc

157

View full text Add to dashboard Cite

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“…While other condensed water instruments have been successfully calibrated by introducing liquid water sprays or ice shavings (Korolev et al, 2013) into a wind tunnel and characterizing the resulting water concentration gradients, for an evaporative total water hygrometer such as the CLH-2, performing the calibration using a sample that includes only water vapor, that is, with the total water content equal to the water vapor content, simplifies the production of calibration mixtures.…”

Section: Total Water Calibration Proceduresmentioning

confidence: 99%

“…All existing measurement techniques are imperfect, with most exhibiting sensitivities to more than one phase of water. For example, closedpath systems designed to sample vapor can be contaminated by evaporation of ingested particulates, and hot-wire sensors often show a response to ice particles in addition to the liquid drops they are designed to measure (Cober et al, 2001;Korolev et al, 2003). The central problem -that measuring water concentration in clouds often results in observations that represent an ambiguous combination of phases -can be 216 S. W. Dorsi et al: A fiber-coupled laser hygrometer for airborne total water measurement avoided by instead measuring total water content -the sum of water mass contained in solid, liquid and vapor forms 1 .…”

Section: Introductionmentioning

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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“…Ice particles shatter on impact with the sensor and are swept away before significant melting or evaporation can occur (Korolev et al, 1998). The TWC collector has a 'deep inverted cone' shape designed to capture both liquid and ice particles (Korolev et al, 2013). Korolev et al (1998) showed that in mixed phase conditions, interactions between the LWC collector and ice particles can result in LWC overestimation on the order of 12% IWC.…”

mentioning

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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Improved Airborne Hot-Wire Measurements of Ice Water Content in Clouds

Cited by 81 publications

References 22 publications

The effective density of small ice particles obtained from in situ aircraft observations of mid‐latitude cirrus

The effective density of small ice particles obtained from in situ aircraft observations of mid‐latitude cirrus

A fiber-coupled laser hygrometer for airborne total water measurement

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

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