Structure and Statistical Analysis of the Microphysical Properties of Generating Cells in the Comma Head Region of Continental Winter Cyclones

Abstract This paper presents analyses of the microphysical structure of cloud-top convective generating cells at temperatures between −10° and −55°C across the comma head of 11 continental cyclones, using data collected by the W-band Wyoming Cloud Radar and in situ instrumentation aboard the National Science Foundation (NSF)/NCAR C-130. A case study of one cyclone is presented, followed by statistical analyses of the entire dataset. Ice particle number concentrations averaged 1.9 times larger inside generating cells compared to outside, and derived ice water contents and median mass diameters averaged 2.2 and 1.1 times larger in cells, respectively. Supercooled water was directly measured at temperatures between −31.4° and −11.1°C, with the median and 95th-percentile liquid water content increasing from ~0.09 to 0.12 g m−3 and 0.14 to 0.28 g m−3 over this temperature range, respectively. Liquid water was present in 26% of observations within cells and 18% of observations between cells over the same temperature range, and it was nearly ubiquitous at temperatures above −16°C. The larger ice particle concentrations in cells are consistent with greater ice production in convective updrafts. The increased mass and diameter of the ice particles demonstrate that generating cells provide environments favorable for enhanced particle growth. The impact of water saturation and supercooled water in the cells was evident, with rapid particle growth by diffusion and sometimes riming apparent, in addition to aggregation. Turbulent mixing lessened the observed differences between cells and surrounding regions, with supercooled water observed within and between cells, similar habits within and between cells, and rimed particles evident even in ice-phase conditions.

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The impact of cloud inhomogeneities on the Earth radiation budget: the 14 October 1989 I.C.E. convective cloud case study

Annales Geophysicae ◽

10.1007/s00585-994-0240-z ◽

1994 ◽

Vol 12 (2/3) ◽

pp. 240-253 ◽

Cited By ~ 1

Author(s):

F. Parol ◽

J. C. Buriez ◽

D. Crétel ◽

Y. Fouquart

Keyword(s):

Aspect Ratio ◽

Water Content ◽

Liquid Water ◽

Convective Cloud ◽

Liquid Water Content ◽

Radiation Budget ◽

The Earth ◽

Earth Radiation Budget ◽

The Impact ◽

Earth Radiation

Abstract. Through their multiple interactions with radiation, clouds have an important impact on the climate. Nonetheless, the simulation of clouds in climate models is still coarse. The present evolution of modeling tends to a more realistic representation of the liquid water content; thus the problem of its subgrid scale distribution is crucial. For a convective cloud field observed during ICE 89, Landsat TM data (resolution: 30m) have been analyzed in order to quantify the respective influences of both the horizontal distribution of liquid water content and cloud shape on the Earth radiation budget. The cloud field was found to be rather well-represented by a stochastic distribution of hemi-ellipsoidal clouds whose horizontal aspect ratio is close to 2 and whose vertical aspect ratio decreases as the cloud cell area increases. For that particular cloud field, neglecting the influence of the cloud shape leads to an over-estimate of the outgoing longwave flux; in the shortwave, it leads to an over-estimate of the reflected flux for high solar elevations but strongly depends on cloud cell orientations for low elevations. On the other hand, neglecting the influence of cloud size distribution leads to systematic over-estimate of their impact on the shortwave radiation whereas the effect is close to zero in the thermal range. The overall effect of the heterogeneities is estimated to be of the order of 10 W m-2 for the conditions of that Landsat picture (solar zenith angle 65°, cloud cover 70%); it might reach 40 W m-2 for an overhead sun and overcast cloud conditions.

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Experiments on the Growth of Spongy Ice Near a Stagnant Point

Journal of Glaciology ◽

10.1017/s0022143000009370 ◽

1990 ◽

Vol 36 (123) ◽

pp. 143-150 ◽

Cited By ~ 8

Author(s):

G.S.H. Lock ◽

I.B. Foster

Keyword(s):

Air Temperature ◽

Liquid Water ◽

Cross Flow ◽

Supercooled Water ◽

Liquid Water Content ◽

Air Temperatures ◽

Stagnant Point ◽

Air Speed ◽

Temperature Liquid ◽

Ice Fraction

AbstractThe paper presents experimental observations on the growth of spongy ice in the vicinity of the forward stagnation point of a disc situated in a cross flow containing supercooled water droplets. Following some preliminary observations, the discussion focuses on two quantities: the ice fraction and the rate of growth of the accretion. The data presented reveal the effects of air speed, air temperature, liquid-water content, and salinity. They also suggest two morphological regimes: at higher air temperatures, the growth appeared to be crystalline columnar; at lower temperatures, smaller crystals appeared to be randomly distributed, producing a mushy accretion.

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Evaluation of Orographic Cloud Seeding Using a Bin Microphysics Scheme: Three-Dimensional Simulation of Real Cases

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0278.1 ◽

2020 ◽

Vol 59 (9) ◽

pp. 1537-1555

Author(s):

István Geresdi ◽

Lulin Xue ◽

Noémi Sarkadi ◽

Roy Rasmussen

Keyword(s):

Water Content ◽

Liquid Water ◽

Cloud Condensation Nuclei ◽

Three Dimensional ◽

Liquid Water Content ◽

Weather Modification ◽

Diffusional Growth ◽

Surface Precipitation ◽

Orographic Clouds ◽

The Impact

AbstractThe University of Pécs and NCAR Bin (UPNB) microphysical scheme was implemented into the mesoscale Weather Research and Forecast (WRF) Model that was used to study the impact of silver iodide (AgI) seeding on precipitation formation in winter orographic clouds. Four different experimental units were chosen from the Wyoming Weather Modification Pilot Project to simulate the seeding effect. The results of the numerical experiments show the following: (i) Comparisons with the soundings, snow gauges, and microwave radiometer data indicate that the three-dimensional simulations with detailed microphysics reasonably represent both the dynamics and the microphysics of real clouds. (ii) The dispersion of the AgI particles from the simulated ground-based seeding was effective because of turbulent mixing. (iii) In the investigated cases (surface temperature is less than 0°C), surface precipitation and precipitation efficiency show low susceptibility to the concentrations of cloud condensation nuclei and natural ice nucleating particles. (iv) If the available liquid water content promotes the enhancement of the number of snowflakes by diffusional growth, the surface precipitation can be increased by more than 5%. A novel parameter relevant to orographic clouds, horizontally integrated liquid water path (LWP), was evaluated to find the relation between seeding efficiency and liquid water content. The impact of seeding is negligible if the horizontal LWP is less than 0.1 mm and is apparent if the horizontal LWP is larger than 1 mm, as based on the cases investigated in this study.

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Aerosol liquid water content in the moist southern West African monsoon layer and its radiative impact

10.5194/acp-2018-420 ◽

2018 ◽

Author(s):

Konrad Deetz ◽

Heike Vogel ◽

Sophie Haslett ◽

Peter Knippertz ◽

Hugh Coe ◽

...

Keyword(s):

Relative Humidity ◽

Water Content ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Diurnal Cycle ◽

Liquid Water ◽

Liquid Water Content ◽

Scale Model ◽

Model Framework ◽

The Impact

Abstract. Water uptake can significantly increase the size and therefore the optical properties of aerosols. In this study, the regional-scale model framework COSMO-ART is applied to Southern West Africa (SWA) for a summer monsoon process study on 2–3 and 6–7 July 2016. The high moisture and aerosol burden in the monsoon layer makes SWA favorable to quantify properties that determine the aerosol liquid water content and its impact on radiative transfer. Given the marked diurnal cycle in SWA, the analysis is separated into three characteristic phases: (a) Atlantic Inflow progression phase (15–2 UTC), when winds from the Gulf of Guinea accelerate in the less turbulent evening and nighttime boundary layer, (b) Moist morning phase (3–8 UTC), when the passage of the Atlantic Inflow front leads to overall cool and moist conditions over land and (c) Daytime drying phase (9–15 UTC), in which the Atlantic Inflow front re-establishes with the inland heating initiated after sunrise. This diurnal cycle imprints, via the relative humidity, also the aerosol liquid water content. We analyzed the impact of relative humidity and clouds on the aerosol liquid water content. As shown by other studies, the accumulation mode particles are the dominant contributor of aerosol liquid water. We find aerosol growth factors of 2 (4) for submicron (coarse) mode particles, leading to a substantial increase of mean aerosol optical depth from 0.2 to 0.7. Considering the aerosol liquid water content leads to a decrease in shortwave radiation of about 20 W m−2, while longwave effects appear to be insignificant, especially during nighttime. The estimated relationships between total column aerosol liquid water and radiation are −305 ± 39 W g−1 (shortwave in-cloud), −114 ± 42 W g−1 (shortwave off-cloud) and about −10 W g−1 (longwave). The results highlight the need to consider the relative humidity dependency of aerosol optical depth in atmospheric models, particularly in moist tropical environments, where their effect on radiation can be very large.

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The Impact of Liquid Water Content over Different Seas of Europe on Satellite Communication

2018 IX National Conference with International Participation (ELECTRONICA) ◽

10.1109/electronica.2018.8439128 ◽

2018 ◽

Author(s):

Hitesh Singh ◽

Boncho Gueorguiev Bonev ◽

Peter Zhelev Petkov ◽

Sarang Patil

Keyword(s):

Water Content ◽

Liquid Water ◽

Satellite Communication ◽

Liquid Water Content ◽

The Impact

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Relationship between optical extinction and liquid water content in fogs

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-9623-2013 ◽

2013 ◽

Vol 6 (6) ◽

pp. 9623-9653

Author(s):

C. Klein ◽

A. Dabas

Keyword(s):

Refractive Index ◽

Linear Relationship ◽

Water Content ◽

Liquid Water ◽

Pure Water ◽

Liquid Water Content ◽

Usual Practice ◽

Optical Extinction ◽

The Real ◽

The Impact

Abstract. Studies carried out in the late 1970s suggest a simple linear relationship exists in practice between the optical extinction in the thermal IR and the liquid water content (LWC) in fogs. Such a relationship opens the possibility to monitor the vertical profile of the LWC in fogs with a rather simple backscatter lidar. Little is known on how the LWC varies as a function of height and during the fog life cycle, so the new measurement technique would help understand fog physics and provide valuable data for improving the quality of fog forecasts. In the present article, the validity of the linear relationship is revisited at the light of recent observations of fog droplet size distributions measured with a combination of sensors covering a large range of droplet radii. In particular, large droplets (radius above 15 μm) are detected, which was not the case in the late 1970s. The results confirm the linear relationship still holds, at least for the mostly radiative fogs observed during the campaign. The impact of the precise value of the real and imaginary parts of the refractive index on the coefficient of the linear relationship is also studied. The usual practice considers droplets are made of pure water. This assumption is probably valid for big droplets, it may be questioned for small ones since droplets are formed from condensation nuclei of highly variable chemical composition. The study suggests the relationship is mostly sensitive to the real part of the refractive index and the sensitivity grows with the size of fog droplets. However, large fog droplets are more likely to have an index close to that of water since they are mainly composed of water.

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Sources of Error in Dual-Wavelength Radar Remote Sensing of Cloud Liquid Water Content

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech2042.1 ◽

2007 ◽

Vol 24 (8) ◽

pp. 1317-1336 ◽

Cited By ~ 13

Author(s):

John K. Williams ◽

J. Vivekanandan

Keyword(s):

Water Content ◽

Liquid Water ◽

Liquid Water Content ◽

Mie Scattering ◽

Dual Wavelength ◽

Cloud Liquid Water ◽

Sources Of Error ◽

Microphysical Properties ◽

Using Data ◽

Cloud Liquid Water Content

Abstract Dual-wavelength ratio (DWR) techniques offer the prospect of producing high-resolution mapping of cloud microphysical properties, including retrievals of cloud liquid water content (LWC) from reflectivity measured by millimeter-wavelength radars. Unfortunately, noise and artifacts in the DWR require smoothing to obtain physically realistic values of LWC with a concomitant loss of resolution. Factors that cause inaccuracy in the retrieved LWC include uncertainty in gas and liquid water attenuation coefficients, Mie scattering due to large water droplets or ice particles, corruption of the radar reflectivities by noise and nonatmospheric returns, and artifacts due to mismatched radar illumination volumes. The error analysis presented here consists of both analytic and heuristic arguments; it is illustrated using data from the Mount Washington Icing Sensors Project (MWISP) and from an idealized simulation. In addition to offering insight into design considerations for a DWR system, some results suggest methods that may mitigate some of these sources of error for existing systems and datasets.

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Simultaneous and synergistic profiling of cloud and drizzle properties using ground-based observations

10.5194/amt-2016-402 ◽

2017 ◽

Cited By ~ 1

Author(s):

Stephanie P. Rusli ◽

David P. Donovan ◽

Herman W. J. Russchenberg

Keyword(s):

Liquid Water ◽

Optimal Estimation ◽

Liquid Water Content ◽

Cloud Base ◽

Unified Framework ◽

Forward Models ◽

Eddy Simulation ◽

Brightness Temperatures ◽

Microphysical Properties ◽

Cloud Properties

Abstract. Despite the importance of radar reflectivity (Z) measurements in the retrieval of liquid water cloud properties, it remains non-trivial to interpret Z due to the possible presence of drizzle droplets within the clouds. So far, there has been no published work that utilizes Z to identify the presence of drizzle above the cloud base in an optimized and a physically-consistent manner. In this work, we develop a retrieval technique that exploits the synergy of different remote sensing systems to carry out this task and to subsequently profile the microphysical properties of the cloud and drizzle in a unified framework. This is accomplished by using ground-based measurements of Z, lidar attenuated backscatter below as well as above the cloud base, and microwave brightness temperatures. Fast physical forward models coupled to cloud and drizzle structure parametrization are used in an optimal estimation type framework in order to retrieve the best-estimate for the cloud and drizzle property profiles. The cloud retrieval is first evaluated using synthetic signals generated from large-eddy simulation output to verify the forward models used in the retrieval procedure and the vertical parametrization of the liquid water content. From this exercise it is found that, on average, the cloud properties can be retrieved within 5 % of the mean truth. The full cloud-drizzle retrieval method is then applied to a selected ACCEPT campaign dataset collected in Cabauw, The Netherlands. An assessment of the retrieval products is performed using three independent methods from the literature, each was specifically developed to retrieve only the cloud properties, the drizzle properties below the cloud base, or the drizzle fraction within the cloud, respectively. One-to-one comparisons, taking into account the uncertainties or limitations of each retrieval, show that our results are generally consistent with what is derived using the three independent methods.

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