Liquid Water Content and Droplet Size Distribution Mass Fractions for Wind Milling Engine Fan Blade Ice Accretion Analysis

2007 ◽  
Author(s):  
R. Elangovan ◽  
M. D. Breer
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Droplet Size ◽  
Liquid Water ◽  
Droplet Size Distribution ◽  
Liquid Water Content ◽  
Ice Accretion ◽  
Mass Fractions ◽  
Fan Blade

scholarly journals Fog Droplet Size Distribution and the Interaction between Fog Droplets and Fine Particles during Dense Fog in Tianjin, China

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 258 ◽  
Author(s):  
Qing Liu ◽  
Bingui Wu ◽  
Zhaoyu Wang ◽  
Tianyi Hao
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Droplet Size ◽  
Liquid Water ◽  
Fine Particles ◽  
Droplet Size Distribution ◽  
Liquid Water Content ◽  
Average Spectrum ◽  
Dense Fog ◽  
Scavenging Efficiency

From November 2016 to January 2017, there were large-scale dense fog processes in Tianjin area on the west coast of Bohai Bay, China, even strong dense fog with visibility less than 50 m occurred. Based on the observation data of fog droplet spectrum monitor, visibility sensor, environmental particle monitoring equipment and meteorological automatic station, the characteristics of fog droplet size distribution and the interaction between the fog droplets and fine particles during dense fog events were analyzed. The results show following characteristics: (1) The average concentration of fog droplets (Na), the average liquid water content (La) and the maximum liquid water content (Lmax) in the strong dense fog process are larger than those in the dense fog. The average spectrum of fog droplet size distribution conforms to Junge distribution, and they are all broad-spectrum fog with a spectrum width of about 45 μm. The average spectrum is similar to the dense fog of heavily industrialized inland in the world. (2) The maximum of fog droplet diameter during the formation stage have a good indication for the outbreak of strong dense fog. (3) The mass concentration of PM2.5 (CPM2.5) is ranged from 121–375 μg/m3, and the interaction between fog droplets and fine particles is analyzed. During the formation, development and maturity stages, fog process can scavenge atmospheric fine particles, and the scavenging efficiency of PM2.5 is more remarkable than PM10. When CPM2.5 does not exceed 350 μg/m3, the increase in the concentration of fine particles is conducive to the rapid growth of fog droplets and the sharp drop of visibility. However, when CPM2.5 exceeds the critical value, the increase has a negative feedback effect on the development of the fog process. More investigations and cases are necessary to fully assess the mechanisms related to the dense fog events in Tianjin area and further analysis will be done.

scholarly journals A Model Intercomparison of CCN-Limited Tenuous Clouds in the High Arctic

2017 ◽  
Author(s):  
Robin G. Stevens ◽  
Katharina Loewe ◽  
Christopher Dearden ◽  
Antonios Dimitrelos ◽  
Anna Possner ◽  
...  
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Liquid Water ◽  
Atmospheric Stability ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Liquid Water Content ◽  
High Arctic ◽  
Model Intercomparison ◽  
Cloud Droplet Size Distribution

Abstract. We perform a model intercomparison of summertime high Arctic (> 80 N) clouds observed during the 2008 Arctic Summer Cloud Ocean Study (ASCOS) campaign, when observed cloud condensation nuclei (CCN) concentrations fell below 1 cm−3. Previous analyses have suggested that at these low CCN concentrations the liquid water content (LWC) and radiative properties of the clouds are determined primarily by the CCN concentrations, conditions that have previously been referred to as the tenuous cloud regime. The intercomparison includes results from three large eddy simulation models (UCLALES-SALSA, COSMO-LES, and MIMICA) and three numerical weather prediction models (COSMO-NWP, WRF, and UM-CASIM). We test the sensitivities of the model results to different treatments of cloud droplet activation, including prescribed cloud droplet number concentrations (CDNC) and diagnostic CCN activation based on either fixed aerosol concentrations or prognostic aerosol with in-cloud processing. There remains considerable diversity even in experiments with prescribed CDNCs and prescribed ice crystal number concentrations (ICNC). The sensitivity of mixed-phase Arctic cloud properties to changes in CDNC depends on the representation of the cloud droplet size distribution within each model, which impacts on autoconversion rates. Our results therefore suggest that properly estimating aerosol–cloud interactions requires an appropriate treatment of the cloud droplet size distribution within models, as well as in-situ observations of hydrometeor size distributions to constrain them. The results strongly support the hypothesis that the liquid water content of these clouds is CCN-limited. For the observed meteorological conditions, the cloud generally did not collapse when the CCN concentration was held constant at the relatively high CCN concentrations measured during the cloudy period, but the cloud thins or collapses as the CCN concentration is reduced. The CCN concentration at which collapse occurs varies substantially between models. Only one model predicts complete dissipation of the cloud due to glaciation, and this occurs only for the largest prescribed ICNC tested in this study. Global and regional models with either prescribed CDNCs or prescribed aerosol concentrations would not reproduce these dissipation events. Additionally, future increases in Arctic aerosol concentrations would be expected to decrease the frequency of occurrence of such cloud dissipation events, with implications for the radiative balance at the surface. Our results also show that cooling of the sea-ice surface following cloud dissipation increases atmospheric stability near the surface, further suppressing cloud formation. Therefore, this suggests that linkages between aerosol and clouds, as well as linkages between clouds, surface temperatures and atmospheric stability need to be considered for weather and climate predictions in this region.

scholarly journals A model intercomparison of CCN-limited tenuous clouds in the high Arctic

2018 ◽  
Vol 18 (15) ◽  
pp. 11041-11071 ◽  
Author(s):  
Robin G. Stevens ◽  
Katharina Loewe ◽  
Christopher Dearden ◽  
Antonios Dimitrelos ◽  
Anna Possner ◽  
...  
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Liquid Water ◽  
Atmospheric Stability ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Liquid Water Content ◽  
High Arctic ◽  
Model Intercomparison ◽  
Cloud Droplet Size Distribution

Abstract. We perform a model intercomparison of summertime high Arctic (> 80∘ N) clouds observed during the 2008 Arctic Summer Cloud Ocean Study (ASCOS) campaign, when observed cloud condensation nuclei (CCN) concentrations fell below 1 cm−3. Previous analyses have suggested that at these low CCN concentrations the liquid water content (LWC) and radiative properties of the clouds are determined primarily by the CCN concentrations, conditions that have previously been referred to as the tenuous cloud regime. The intercomparison includes results from three large eddy simulation models (UCLALES-SALSA, COSMO-LES, and MIMICA) and three numerical weather prediction models (COSMO-NWP, WRF, and UM-CASIM). We test the sensitivities of the model results to different treatments of cloud droplet activation, including prescribed cloud droplet number concentrations (CDNCs) and diagnostic CCN activation based on either fixed aerosol concentrations or prognostic aerosol with in-cloud processing. There remains considerable diversity even in experiments with prescribed CDNCs and prescribed ice crystal number concentrations (ICNC). The sensitivity of mixed-phase Arctic cloud properties to changes in CDNC depends on the representation of the cloud droplet size distribution within each model, which impacts autoconversion rates. Our results therefore suggest that properly estimating aerosol–cloud interactions requires an appropriate treatment of the cloud droplet size distribution within models, as well as in situ observations of hydrometeor size distributions to constrain them. The results strongly support the hypothesis that the liquid water content of these clouds is CCN limited. For the observed meteorological conditions, the cloud generally did not collapse when the CCN concentration was held constant at the relatively high CCN concentrations measured during the cloudy period, but the cloud thins or collapses as the CCN concentration is reduced. The CCN concentration at which collapse occurs varies substantially between models. Only one model predicts complete dissipation of the cloud due to glaciation, and this occurs only for the largest prescribed ICNC tested in this study. Global and regional models with either prescribed CDNCs or prescribed aerosol concentrations would not reproduce these dissipation events. Additionally, future increases in Arctic aerosol concentrations would be expected to decrease the frequency of occurrence of such cloud dissipation events, with implications for the radiative balance at the surface. Our results also show that cooling of the sea-ice surface following cloud dissipation increases atmospheric stability near the surface, further suppressing cloud formation. Therefore, this suggests that linkages between aerosol and clouds, as well as linkages between clouds, surface temperatures, and atmospheric stability need to be considered for weather and climate predictions in this region.

scholarly journals The effect of droplet size and liquid water content on ice accretion and aerodynamic coefficients of tower legs

2013 ◽  
Vol 132-133 ◽  
pp. 362-374 ◽  
Author(s):  
H. Banitalebi Dehkordi ◽  
M. Farzaneh ◽  
P. Van Dyke ◽  
L.E. Kollar
Keyword(s):  
Water Content ◽  
Droplet Size ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Ice Accretion ◽  
Aerodynamic Coefficients

scholarly journals Theoretical Analysis of the Entrainment–Mixing Process at Cloud Boundaries. Part I: Droplet Size Distributions and Humidity within the Interface Zone

2018 ◽  
Vol 75 (6) ◽  
pp. 2049-2064 ◽  
Author(s):  
Mark Pinsky ◽  
Alexander Khain
Keyword(s):  
Water Content ◽  
Droplet Size ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Mixing Process ◽  
Governing Parameter ◽  
Interface Zone ◽  
Dry Air ◽  
Air Interface ◽  
Entrainment Mixing

Abstract The problem of a complex entrainment–mixing process is analyzed by solving a diffusion–evaporation equation for an open region in the vicinity of the cloud–dry air interface. Upon normalization the problem is reduced to a one-parametric one, the governing parameter being the potential evaporation parameter R proportional to the ratio of saturation deficit in the dry air to the available liquid water content in the cloud air. As distinct from previous multiple studies analyzing mixing within closed adiabatic volumes, we consider a principally nonstationary problem that never leads to a homogeneous equilibrium state. It is shown that at R < −1 the cloud edge shifts toward the cloud; that is, the cloud dissipates due to mixing with dry air, and the cloud volume decreases. If R > −1, the cloud edge shifts outside; that is, the mixing leads to an increase in the cloud volume. The time evolution of droplet size distribution and its moments, as well as the relative humidity within the expanding cloud–dry air interface, are calculated and analyzed. It is shown that the values of the mean volume radii rapidly decrease within the interface zone in the direction away from the cloud, indicating significant changes in the cloud edge microstructure. Scattering diagrams plotted for the cloud edge agree well with high-frequency in situ measurements, corroborating the reliability of the proposed approach. It is shown that the humidity front moves toward dry air faster than the front of liquid water content. As a result, the mixing leads to formation of a humid air shell around the cloud. The widths of the interface zone and humid shell are evaluated.

scholarly journals Evaluating MODIS cloud retrievals with in situ observations from VOCALS-REx

2012 ◽  
Vol 12 (9) ◽  
pp. 23679-23729 ◽  
Author(s):  
N. J. King ◽  
K. N. Bower ◽  
J. Crosier ◽  
I. Crawford
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Liquid Water ◽  
Near Infrared ◽  
Droplet Size Distribution ◽  
Effective Radius ◽  
Liquid Water Path ◽  
Water Path ◽  
High Bias

Abstract. Microphysical measurements collected during eleven profiles through marine stratocumulus as part of the Variability of the American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) are compared to collocated overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua and Terra satellite platforms. The full depth of the cloud is sampled in each case using a Cloud Droplet Probe (CDP) and a Two-Dimensional Stereo Probe (2DS) together sizing cloud and precipitation droplets in the diameter range 2-1260 μm. This allows the total optical depth (τc) of the cloud and effective radius (re) of the droplet size distribution to be compared to MODIS cloud retrievals of the same quantities along with the secondarily derived total liquid water path. When compared to the effective radius at cloud top, the MODIS retrieved re using the 2.1 μm wavelength channel overestimates the in situ measurements on average by 13% with the largest overestimations coinciding with the detection by the 2DS of drizzle sized droplets. We show through consideration of the full vertical profile and penetration depths of the wavelengths used in the retrieval that the expected retrieved values are less than those at cloud top thus increasing the apparent bias in re retrievals particularly when using the 1.6 and 2.1 μm channels, with the 3.7 μm channel retrievals displaying the best agreement with in situ values. Retrievals of τc also tend to overestimate in situ values which, coupled with a high bias in re retrievals, lead to an overestimation of liquid water path. There is little apparent correlation between the variation of the three near-infrared re retrievals and the vertical structure of the cloud observed in situ. Retrievals are performed using measured profiles of water vapour and temperature along with an accurate knowledge of the width of the droplet size distribution which improve agreement between in situ and retrieved values but cannot completely explain the observed biases. Additionally we show that cloud heterogeneity and three-dimensional radiative effects may high skew the mean when averaging over comparison domains but cannot explain all of the apparent high bias.

scholarly journals Stratocumulus Liquid Water Content from Dual-Wavelength Radar

2005 ◽  
Vol 22 (8) ◽  
pp. 1207-1218 ◽  
Author(s):  
Robin J. Hogan ◽  
Nicolas Gaussiat ◽  
Anthony J. Illingworth
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Wave Attenuation ◽  
Droplet Size Distribution ◽  
Liquid Water Content ◽  
Radar Signal ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Atmospheric Radiation Measurement ◽  
The Difference

Abstract A technique is described to retrieve stratocumulus liquid water content (LWC) using the differential attenuation measured by vertically pointing radars at 35 and 94 GHz. Millimeter-wave attenuation is proportional to LWC and increases with frequency, so LWC can be derived without the need to make any assumptions on the nature of the droplet size distribution. There is also no need for the radars to be well calibrated. A significant advantage over many radar techniques in stratocumulus is that the presence of drizzle drops (those with a diameter larger than around 50 μm) does not affect the retrieval, even though such drops may dominate the radar signal. It is important, however, that there are not significant numbers of drops larger than 600 μm, which scatter outside of the Rayleigh regime at 94 GHz. A lidar ceilometer is used to locate the cloud base in the presence of drizzle falling below the cloud. An accuracy of around 0.04 g m−3 is achievable with averaging over 1 min and 150 m (two range gates), but for the previously suggested frequency pair of 10 and 35 GHz, the corresponding accuracy would be considerably worse at 0.34 g m−3. First, the retrieval of LWC is simulated using aircraft-measured size spectra taken from a profile through marine stratocumulus. Results are then presented from two case studies—one using two cloud radars at Chilbolton in southern United Kingdom, and another using the Cloud Profiling Radar System at the Atmospheric Radiation Measurement site in Oklahoma. The liquid water path from the technique was found to be in good agreement with the values that were obtained from microwave radiometers, with the difference between the two being close to the accuracy of the radiometer retrieval. In the case of well-mixed stratocumulus, the profiles were close to adiabatic.

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