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Images of the Nevzorov TWC sensor cone taken with high-speed video camera in a flow of ice particles in the Cox & Co wind tunnel. Red dashed lines in (b) and (d) indicate the shape of the hollow cone of the hot-wire sensor. Airspeed is 80 m s 21. Original video is available online at ftp://depot.cmc.ec.gc.ca/upload/hsvideo.
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Airborne measurements of ice water content (IWC) in both ice and mixed-phase clouds remain one of the long-standing problems in experimental cloud physics. For nearly three decades, IWC has been measured with the help of the Nevzorov hot-wire total water content (TWC) sensor, which had an inverted cone shape. It was assumed that ice particles would...
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... pixel resolution of the camera was determined by the optical zoom settings, and for the experiments described below it ranged from approximately 50 to 100 mm. Figure 1 shows images of the side view of the Nevzorov TWC sensor exposed to a flow of ice particles. As seen in Fig. 1, some of the particles rebound off the TWC cone into the airstream and are swept away, which re- sults in an underestimate of the measured IWC. ...
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... v5.0 (v5) high-frame- rate camera manufactured by Vision Research, Inc. The pixel resolution of the camera was determined by the optical zoom settings, and for the experiments described below it ranged from approximately 50 to 100 mm. Figure 1 shows images of the side view of the Nevzorov TWC sensor exposed to a flow of ice particles. As seen in Fig. 1, some of the particles rebound off the TWC cone into the airstream and are swept away, which re- sults in an underestimate of the measured IWC. How- ever, the efforts to quantify the IWC losses by counting the incoming ice particles that approach the sensor cone and rebound out based on high-speed video frames proved ...
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... resulted in a deeper catch volume requiring particles to bounce farther forward into the airstream to exit the capture volume. Figure 4 shows video frames of the modified deep TWC cone exposed to the flow of ice particles. The video in this sequence was shot with a different exposure rate that does not result in the particle streaks observed in Figs. 1a-d. The bounced particles in this video appear as quasi-spherical sharp images, whereas the ice particles in the undisturbed flow appear as elongated streaks because of their higher velocity. The rebounding ice particles are indicated by the arrows in Fig. 4b. Most video frames of the deep cone did not contain evidence of particles ...
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... is worth mentioning that most ice clouds with large ice particles (D max . 4 mm) were associated with tem- peratures 2158 , T , 2108C (Fig. 10a). This tempera- ture range corresponds to the dendritic ice growth regime. Dendrites typically form large fragile low- density aggregates that may be hypothesized to cause larger measurement problems because of fragmenta- tion and shattering. As seen from the diagrams in Figs. 9, these particles result in the largest uncertainties in ...
Citations
... The particle size bins corresponding to the distribution suggest that the cloud contained particles up to approximately D max = 5.75 mm. There are large uncertainties in the number concentrations of ice particles smaller than 100 µm, due to shattering (Korolev et al., 2013b). Furthermore, Buehler et al. (2007) show the sensitivity of various submillimetre channels to particles of different size. ...
The first closure study involving passive microwave and submillimetre measurements of ice clouds with the consideration of oriented particles is presented, using a unique combination of polarised observations from the ISMAR spectral-like radiometer, two radars with frequencies of 35 and 95 GHz, and a variety of in situ instruments. Of particular interest to this study are the large V–H polarised brightness temperature differences measured from ISMAR above a thick frontal ice cloud. Previous studies combining radar and passive submillimetre measurements have not considered polarisation differences. Moreover, they have assumed particle habits a priori. We aim to test whether the large V–H measurements can be simulated successfully by using an atmospheric model consistent with in situ microphysics. An atmospheric model is constructed using information from the in situ measurements, such as the ice water content, the particle size distribution, and the mass and shape of particles, as well as background information obtained from dropsonde profiles. Columnar and dendritic aggregate particle models are generated specifically for this case, and their scattering properties are calculated using the independent monomer approximation under the assumption of horizontal orientation. The scattering properties are used to perform polarised radiative transfer simulations using ARTS to test whether we can successfully simulate the measured large V–H differences. Radar measurements are used to extrapolate the 1-D microphysical profile to derive a time series of particle size distributions which are used to simulate ISMAR brightness temperatures. These simulations are compared to the observations. It is found that particle models that are consistent with in situ microphysics observations are capable of reproducing the brightness temperature depression and polarisation signature measured from ISMAR at the dual-polarised channel of 243 GHz. However, it was required that a proportion of the particles were changed in order to increase the V–H polarised brightness temperature differences. Thus, we incorporated millimetre-sized dendritic crystals, as these particles were observed in the probe imagery. At the second dual-polarised channel of 664 GHz, the brightness temperature depressions were generally simulated at the correct locations; however, the simulated V–H was too large. This work shows that multi-frequency polarisation information could be used to infer realistic particle shapes, orientations, and representations of the split between single crystals and aggregates within the cloud.
... This probe, manufactured by Sky Physics Technology Inc., has sensors to measure the bulk liquid-water content (LWC) and the total condensed-water content (liquid plus ice) in cloud (Korolev et al., 1998). The vane used, which self-aligns to the airflow, consists of two coiled wires of 2 and 3 mm diameter for liquid-water content measurement and an 8 mm deep cup total-water sensor (Korolev et al., 2013). All elements were operated at 120°C, and data were recorded at 64 Hz. ...
Cloud feedbacks associated with deep convective anvils remain highly uncertain. In part, this uncertainty arises from a lack of understanding of how microphysical processes influence the cloud radiative effect. In particular, climate models have a poor representation of microphysics processes, thereby encouraging the collection and study of observation data to enable better representation of these processes in models. As such, the Deep Convective Microphysics Experiment (DCMEX) undertook an in situ aircraft and ground-based measurement campaign of New Mexico deep convective clouds during July–August 2022. The campaign coordinated a broad range of instrumentation measuring aerosol, cloud physics, radar, thermodynamics, dynamics, electric fields, and weather. This paper introduces the potential data user to DCMEX observational campaign characteristics, relevant instrument details, and references to more detailed instrument descriptions. Also included is information on the structure and important files in the dataset in order to aid the accessibility of the dataset to new users. Our overview of the campaign cases illustrates the complementary operational observations available and demonstrates the breadth of the campaign cases observed. During the campaign, a wide selection of environmental conditions occurred, ranging from dry, northerly air masses with low wind shear to moist, southerly air masses with high wind shear. This provided a wide range of different convective growth situations. Of 19 flight days, only 2 d lacked the formation of convective cloud. The dataset presented (https://doi.org/10.5285/B1211AD185E24B488D41DD98F957506C; Facility for Airborne Atmospheric Measurements et al., 2024) will help establish a new understanding of processes on the smallest cloud- and aerosol-particle scales and, once combined with operational satellite observations and modelling, can support efforts to reduce the uncertainty of anvil cloud radiative impacts on climate scales.
... It is based on thermodynamic models, and consists of a heater wire for each type of measurement, together with a reference wire which is shielded from direct contact with ice particles. The heating power necessary to maintain a constant temperature is determined by means of feedback [19,20]. Although such probes are able to estimate TWC and LWC, and thus infer possible ice formation conditions, they are more suited to atmospheric research than in hostile environments such as compressor flows. ...
The problem of crystal ice formation inside aircraft turbine engines is well‐documented, and poses a significant risk to safety. The problem is not only one of power loss in flight, but the very real possibility that a flame‐out event could occur due to ice accretion on compressor stators, with potentially catastrophic outcomes. Although many instrumentation systems have been developed for wing ice detection, incipient formation of crystal ice is somewhat more difficult to detect. This is compounded by the need for a noncontact sensor which is robust to in‐flight conditions. This paper proposes an approach to the detection of ice formation based on microwave transmission characteristics across the first and possibly the second stage of the compressor stator. It is shown that noncontact detection is feasible under realistic conditions. The contribution of this paper is twofold. First, the microwave transmission approach is motivated using wind tunnel measurements, and appropriate frequency bands are determined. Next, a signal processing approach involving higher‐order analysis of time‐frequency distribution characteristics is then put forward. Experimental results are presented to support the hypothesis that multiband detection offers a workable approach to the incipient crystal‐ice detection problem.
... From these measurements, ice water content can be calculated. The vane used, which self-aligns to the airflow, consists of two coiled wires of 2 and 3 mm diameter for LWC measurement 385 and an 8 mm deep cup total water sensor (Korolev et al., 2013). All elements were operated at 120 • C and data were recorded at 64 Hz. ...
Sensitivity of global temperature to rising CO2 remains highly uncertain. One of the greatest sources of uncertainty arises from cloud feedbacks associated with deep convective anvils. For deep convective clouds, their growth and characteristics are substantially controlled by mixed-phase microphysical processes. However, there remain several questions about cloud microphysical processes, especially in deep, mixed-phase clouds. Meanwhile, the representation of these processes in global climate models is limited. As such, the Deep Convective Microphysics Experiment (DCMEX) has undertaken an in-situ aircraft and ground-based measurement campaign. The data, combined with operational satellite observations and modelling, will help establish new understanding from the smallest, cloud and aerosol particle scales through to the largest, cloud-system and climate scales. DCMEX is one of four projects in the UK Natural Environment Research Council, Uncertainty in climate sensitivity due to clouds, CloudSense programme. Along with other CloudSense projects, DCMEX will support progress in reducing the uncertainty in cloud feedbacks and equilibrium climate sensitivity. This paper lays out the underpinning dataset from the DCMEX summer 2022 field campaign. Its content describes the coordinated operation and technical details of the broad range of aerosol, cloud physics, radar, thermodynamics, dynamics, electric field and weather instruments deployed. In addition, an overview of the characteristics of campaign cases illustrates the complementary operational observations available, as well as demonstrating the breadth of the campaign cases observed.
... Cloud and precipitation particle concentration, phase discrimination, and habit identification were provided by a combination of scattering and optical array probes (e.g., Fig. 3b). Bulk measurements of liquid and ice content were provided by hotwire probes, including a deep-cone Nevzorov (Korolev et al. 2013). Aerosol size distributions from outside of cloud were provided by a wing-mounted Ultra-High Sensitivity Aerosol Spectrometer (UHSAS; Cai et al. 2008). ...
During near-0°C surface conditions, diverse precipitation types (p-types) are possible, including rain, drizzle, freezing rain, freezing drizzle, ice pellets, wet snow, snow, and snow pellets. Near-0°C precipitation affects wide swaths of the United States and Canada, impacting aviation, road transportation, power generation and distribution, winter recreation, ecology, and hydrology. Fundamental challenges remain in observing, diagnosing, simulating, and forecasting near-0°C p-types, particularly during transitions and within complex terrain. Motivated by these challenges, the field phase of the Winter Precipitation Type Research Multi-scale Experiment (WINTRE-MIX) was conducted from 1 February – 15 March 2022 to better understand how multiscale processes influence the variability and predictability of p-type and amount under near-0°C surface conditions. WINTRE-MIX took place near the US / Canadian border, in northern New York and southern Quebec, a region with plentiful near-0°C precipitation influenced by terrain. During WINTRE-MIX, existing advanced mesonets in New York and Quebec were complemented by deployment of: (1) surface instruments, (2) the National Research Council Convair-580 research aircraft with W- and X-band Doppler radars and in situ cloud and aerosol instrumentation, (3) two X-band dual-polarization Doppler radars and a C-band dual-polarization Doppler radar from University of Illinois, and (4) teams collecting manual hydrometeor observations and radiosonde measurements. Eleven intensive observing periods (IOPs) were coordinated. Analysis of these WINTRE-MIX IOPs is illuminating how synoptic dynamics, mesoscale dynamics, and microscale processes combine to determine p-type and its predictability under near-0°C conditions. WINTRE-MIX research will contribute to improving nowcasts and forecasts of near-0°C precipitation through evaluation and refinement of observational diagnostics and numerical forecast models.
... The aircraft collected profiling radar data and in situ cloud microphysical and meteorological data. Here, we use liquid water content (LWC) and ice water content (IWC) measurements from a Nevzorov probe (Korolev et al. 2013). For the four flights examined here, the Nevzorov LWC measurement compares well to LWC estimates from another probe, the Cloud Droplet Probe, where droplet water mass is integrated over the size spectrum from 2 to 50 mm. ...
... This comparison uses both scatterplots and histograms (not shown); mean values of the two probes are within 35% of the overall mean. The aircraft did not carry an independent bulk IWC probe, so the Nevzorov IWC estimate is less certain, but Korolev et al. (2013) report that for ice particles smaller than 4 mm, the Nevzorov IWC falls within 50% of IWC estimates from two other probes. ...
Airborne vertically-profiling Doppler radar data and output from a ~1 km grid resolution numerical simulation are used to examine how relatively small-scale terrain ridges (~10-25 km apart and ~0.5-1.0 km above the surrounding valleys) impact cross-mountain flow, cloud processes, and surface precipitation in deep stratiform precipitation systems. The radar data were collected along fixed flight tracks aligned with the wind, about 100 km long between the Snake River Plain and the Idaho Central Mountains, as part of the 2017 Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE). Data from repeat flight legs are composited in order to suppress transient features and retain the effect of the underlying terrain.
Simulations closely match observed series of terrain-driven deep gravity waves, although the simulated wave amplitude is slightly exaggerated. The deep waves produce pockets of supercooled liquid water in the otherwise ice-dominated clouds (confirmed by flight-level observations and the model) and distort radar-derived hydrometeor trajectories. Snow particles aloft encounter several wave up- and down-drafts before reaching the ground. No significant wave-like modulation of radar reflectivity or model ice water content occurs. The model does indicate substantial localized precipitation enhancement (1.8-3.0 times higher than the mean) peaking just downwind of individual ridges, especially those ridges with the most intense wave updrafts, on account of shallow pockets of high liquid water content on the upwind side, leading to the growth of snow and graupel, falling out mostly downwind of the crest. Radar reflectivity values near the surface are complicated by snow melt, but suggest a more modest enhancement downwind of individual ridges.
... Another possible concentration bias is in processing asynchronous 2D probe images to calculate the sample area. Errors in determining sample area are size dependent and larger for small particles (Korolev et al., 2013a); therefore, such errors are more important for the +7 and +4 • C cases. ...
Jet engine power loss due to ice particle accumulation is a recognized
aviation hazard occurring in cloud conditions difficult to forecast or
visually recognize. High-altitude cirrus clouds can have ice particle
concentrations high enough to be dangerous; therefore, pilots must be
informed when aircraft enter such environments. One approach to determining
ice particle concentration is an onboard lidar system. Concurrent lidar
measurements are compared to backscatter coefficients derived from particle
size distributions obtained from wing-mounted, in situ probes during four
case studies consisting of sixty-second flight segments at different
temperatures: +7 and +4 ∘C for water droplet
analysis, and −33 and −46 ∘C for ice particle analysis.
Backscatter coefficients derived from external cloud probes (ECP) are
correlated (0.91) with measurements by an airborne lidar system known as the
Optical Ice Detector (OID). Differences between OID and ECP backscatter
coefficients range from less than 1 to over 3 standard deviations in terms of uncertainties. The backscatter coefficients are mostly in agreement for
liquid clouds and are in disagreement for the −33 and −46 ∘C cases, with ECP-derived backscatter coefficients lower than
the OID for three out of the four cases. Measurements over four 60 s research flight segments show that measured total water content is
correlated (0.74) with the OID backscatter coefficient, which indicates that
the OID is a useful instrument for determining ice particle concentrations
over a broad range of environments, including at ice water contents as low
as 0.02 g m−3. Additionally, concurrent measurements from cloud imaging
probes and the OID provide improved knowledge of cloud conditions, which may
help in understanding cloud processes.
... The data used here was collected by the Weather Modification Center of China Meteorological Administration and Weather Modification Office of Anhui Province during a cloud experiment over the northeast region of Jiangsu Province on 22 October 2018 using a King-350 (10GB) aircraft (Yang et al., 2019). A suite of instruments onboard the aircraft was used including a Nevzorov hotwire probe (Korolev et al., 2013), a Fast Cloud Droplet Probe (FCDP), a two-dimensional stereo probe (2DS), a High-Volume Precipitation Spectrometer (HVPS), and a Cloud Particle Imager (CPI) probe. The first three instruments were made by Stratton Park Engineering Company (SPEC). ...
The microphysical properties of supercooled liquid droplets (SLDs) and ice particles of stratiform mixed-phase clouds over Eastern China are characterized using carefully post-processed airborne data. The majority sampled clouds were precipitating with ice particles and were frequently mixed with SLDs at cold temperature (T). While the concentration of large ice crystal (> 600 μm) was low (up to 3 L⁻¹), the concentration of smaller ice particle (> 50 μm) was high (up to 300 L⁻¹). Such particles with high concentration cannot be a result of the recirculation of pre-existing aged ice and thus secondary ice production (SIP) was likely occurring over the stratiform clouds at temperatures between −16.9 °C and − 6.4 °C. The statistical analyses show that concentrations of tiny, hexagonal and irregular ice crystals were significantly greater in updraft than those in downdraft regions, suggesting that updrafts not only provide a favorable environment for the growth of cloud particles, but also promote the multiplication of the above young-age small ice (50–100 μm) where SIP is commonly occurring. Since the criteria for the other SIP mechanisms are difficult to meet for this light-riming stratiform without deep convections, this analysis indicates that shattering during droplet freezing might thus be an important SIP source at temperatures between −15 °C and − 9 °C. This study should provide a precise opportunity for parameterizations of mixed-phase stratiform clouds associated with SIP process and the effects of updrafts/temperature.
... The Nevzorov probe liquid water sensor measurements were corrected on the residual effect of ice (Field et al., 2004;A. V. Korolev et al., 1998 and the total water sensor measurements were corrected on the ice bouncing effect (A. V. Korolev et al., 2013). The Rosemount Icing Detector was used to identify the presence of the liquid phase and exclude false liquid signals in ice clouds. ...
Mixed‐phase clouds are recognized as significant contributors to the modulation of precipitation and radiation transfer on both regional and global scales. This study is focused on the analysis of spatial inhomogeneity of mixed‐phase clouds based on an extended data set obtained from airborne in situ observations. The lengths of continuous segments of ice, liquid, and mixed‐phase clouds present a cascade of scales varying from 10² km down to a minimum scale of 100 m determined by the spatial resolution of measurements. It was found that the phase composition of mixed‐phase clouds is highly intermittent, and the frequency of occurrence of ice, liquid, and mixed‐phase regions increases with the decrease of their spatial scales. The distributions of spatial scales have well‐distinguished power‐law dependencies. The results obtained yield insight into the morphology of mixed‐phase clouds and have important implications for improvement in representing subgrid inhomogeneity of mixed‐phase clouds in weather and climate models.
... Unlike LWC, IWC was estimated in the form m=aD b , where D is the diameter of the ice particle from the shadow images and a and b are empirically derived parameters. Previous studies have proposed several different sets of parameters a and b (Brown and Francis, 1995;Baker and Lawson, 2006;Heymsfield et al., 2010;Korolev et al., 2013;Wang et al., 2015). IWC as measured by Hotwire have been found to be nearly the same as the PSD estimation for D < 4 mm (Korolev et al., 2013). ...
... Previous studies have proposed several different sets of parameters a and b (Brown and Francis, 1995;Baker and Lawson, 2006;Heymsfield et al., 2010;Korolev et al., 2013;Wang et al., 2015). IWC as measured by Hotwire have been found to be nearly the same as the PSD estimation for D < 4 mm (Korolev et al., 2013). In comparison, the relationship from Heymsfield et al. (2010, hereafter H10) came from more recent airborne observations with broader temperatures ranging from 0°C to -60°C, and particle sizes between 100 and 2000 μm. ...
The microphysical characteristics of wintertime cold clouds in North China were investigated from 22 aircraft observation flights from 2014 to 2017, 2020, and 2021. The clouds were generated by mesoscale weather systems with little orographic component. Over the mixed-phase temperature range (−10°C to 0°C), the average fraction of liquid, mixed-phase, and ice cloud was 4.9%, 23.3%, and 71.8%, respectively, and the probability distribution of ice mass fraction was a half-U-shape, suggesting that ice cloud was the primary cloud type. The wintertime mixed-phase clouds in North China were characterized by large cloud droplet number concentration, small liquid water content (LWC), and small effective diameter of cloud droplets. The main reason for larger cloud droplet number concentration and smaller effective diameter of cloud droplets was the heavy pollution in winter in North China, while for smaller LWC was the lower temperature during flights and the difference in air mass type. With the temperature increasing, cloud droplet number concentration, LWC, and the size of ice particles increased, but ice number concentration and effective diameter of cloud droplets decreased, similar to other mid-latitude regions, indicating the similarity in the temperature dependence of cloud properties of mixed-phase clouds. The variation of the cloud properties and ice habit at different temperatures indicated the operation of the aggregation and riming processes, which were commonly present in the wintertime mixed-phase clouds. This study fills a gap in the aircraft observation of wintertime cold clouds in North China.
