scholarly journals Final Report on “Influence of nucleation on ice microphysical properties of mixed-phase stratiform clouds”

2018 ◽  
Author(s):  
Raymond A. Shaw
Keyword(s):  
Mixed Phase ◽  
Final Report ◽  
Microphysical Properties ◽  
Stratiform Clouds

scholarly journals Vertical Motions in Arctic Mixed-Phase Stratiform Clouds

2008 ◽  
Vol 65 (4) ◽  
pp. 1304-1322 ◽  
Author(s):  
Matthew D. Shupe ◽  
Pavlos Kollias ◽  
P. Ola G. Persson ◽  
Greg M. McFarquhar
Keyword(s):  
Liquid Water ◽  
Single Layer ◽  
Water Layer ◽  
Mixed Phase ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Remote Sensors ◽  
Microphysical Properties ◽  
Stratiform Clouds ◽  
Dynamical Properties

Abstract The characteristics of Arctic mixed-phase stratiform clouds and their relation to vertical air motions are examined using ground-based observations during the Mixed-Phase Arctic Cloud Experiment (MPACE) in Barrow, Alaska, during fall 2004. The cloud macrophysical, microphysical, and dynamical properties are derived from a suite of active and passive remote sensors. Low-level, single-layer, mixed-phase stratiform clouds are typically topped by a 400–700-m-deep liquid water layer from which ice crystals precipitate. These clouds are strongly dominated (85% by mass) by liquid water. On average, an in-cloud updraft of 0.4 m s−1 sustains the clouds, although cloud-scale circulations lead to a variability of up to ±2 m s−1 from the average. Dominant scales-of-variability in both vertical air motions and cloud microphysical properties retrieved by this analysis occur at 0.5–10-km wavelengths. In updrafts, both cloud liquid and ice mass grow, although the net liquid mass growth is usually largest. Between updrafts, nearly all ice falls out and/or sublimates while the cloud liquid diminishes but does not completely evaporate. The persistence of liquid water throughout these cloud cycles suggests that ice-forming nuclei, and thus ice crystal, concentrations must be limited and that water vapor is plentiful. These details are brought together within the context of a conceptual model relating cloud-scale dynamics and microphysics.

scholarly journals A numerical study of aerosol influence on mixed-phase stratiform clouds through modulation of the liquid phase

2013 ◽  
Vol 13 (4) ◽  
pp. 1733-1749 ◽  
Author(s):  
G. de Boer ◽  
T. Hashino ◽  
G. J. Tripoli ◽  
E. W. Eloranta
Keyword(s):  
Liquid Phase ◽  
Mass Fraction ◽  
Freezing Point ◽  
Numerical Study ◽  
Liquid Droplet ◽  
Number Concentration ◽  
Mixed Phase ◽  
Large Variability ◽  
Stratiform Clouds ◽  
Aerosol Properties

Abstract. Numerical simulations were carried out in a high-resolution two-dimensional framework to increase our understanding of aerosol indirect effects in mixed-phase stratiform clouds. Aerosol characteristics explored include insoluble particle type, soluble mass fraction, influence of aerosol-induced freezing point depression and influence of aerosol number concentration. Simulations were analyzed with a focus on the processes related to liquid phase microphysics, and ice formation was limited to droplet freezing. Of the aerosol properties investigated, aerosol insoluble mass type and its associated freezing efficiency was found to be most relevant to cloud lifetime. Secondary effects from aerosol soluble mass fraction and number concentration also alter cloud characteristics and lifetime. These alterations occur via various mechanisms, including changes to the amount of nucleated ice, influence on liquid phase precipitation and ice riming rates, and changes to liquid droplet nucleation and growth rates. Alteration of the aerosol properties in simulations with identical initial and boundary conditions results in large variability in simulated cloud thickness and lifetime, ranging from rapid and complete glaciation of liquid to the production of long-lived, thick stratiform mixed-phase cloud.

scholarly journals First Look at the Occurrence of Horizontally Oriented Ice Crystals over Summit, Greenland

2017 ◽  
Author(s):  
Sebastian Cole ◽  
Ryan R. Neely III. ◽  
Robert A. Stillwell
Keyword(s):  
Ground Level ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Wind Speeds ◽  
Microphysical Properties ◽  
Stratiform Clouds ◽  
Monthly Changes ◽  
Microphysical Processes ◽  
Monthly Variations

Abstract. The microphysical properties of clouds play a significant role in determining their radiative effect; one of these properties is the orientation of ice crystals. A source of error in current microphysical retrievals and model simulations is the assumption that clouds are composed of only randomly oriented ice crystals (ROIC). This assumption is frequently not true, as evidenced by optical phenomena such as parhelia (commonly referred to as sundogs). Here, observations from the Cloud, Aerosol and Polarization Backscatter Lidar (CAPABL) at Summit, Greenland are utilized along with instruments that are part of the Integrated Characterization of Energy, Clouds, Atmospheric state and Precipitation at Summit (ICECAPS) project in order to determine when, where and under what conditions horizontally oriented ice crystals (HOIC) occur at Summit, Greenland. Between July 2015 and May 2016, HOIC are observed on 86 days of the 335-day study. HOIC occurred within stratiform clouds on 48 days, in precipitation on 32 days and in cirrus clouds on 14 days. Analysis of all of the cases found that, on average, in comparison to ROIC, HOIC occur at higher temperatures, higher wind speeds and lower heights above ground level. Differences were also present in the relative humidities (RHs) at which HOIC and ROIC occurred in stratiform clouds and precipitation but not in cirrus clouds. Analysis over the whole study period revealed monthly variations in the abundance of HOIC with the number of detections peaking in April and October. Monthly changes were also present in the number of days containing HOIC. The results presented here aim to be the first step towards a comprehensive climatology and understanding of the microphysical processes that lead to the formation of HOIC at Summit, Greenland.

scholarly journals Vertical redistribution of moisture and aerosol in orographic mixed-phase clouds

2020 ◽  
Author(s):  
Annette K. Miltenberger ◽  
Paul R. Field ◽  
Adrian H. Hill
Keyword(s):  
Air Temperature ◽  
Unified Model ◽  
Mixed Phase ◽  
Atmospheric Models ◽  
Microphysical Properties ◽  
Cloud Microphysical Processes ◽  
Microphysical Processes ◽  
Mixed Phase Clouds ◽  
Natural Laboratory

Abstract. Orographic wave clouds offer a natural laboratory to investigate cloud microphysical processes and their representation in atmospheric models. Wave clouds impact the larger-scale flow by the vertical redistribution of moisture and aerosol. Here we use detailed cloud microphysical observations from the ICE-L campaign to evaluate the recently developed Cloud Aerosol Interacting Microphysics (CASIM) module in the Met Office Unified Model (UM) with a particular focus on different parameterisations for heterogeneous freezing. Modelled and observed thermodynamic and microphysical properties agree very well (deviation of air temperature

scholarly journals Long-lifetime ice particles in mixed-phase stratiform clouds: Quasi-steady and recycled growth

2015 ◽  
Vol 120 (22) ◽  
pp. 11,617-11,635 ◽  
Author(s):  
Fan Yang ◽  
Mikhail Ovchinnikov ◽  
Raymond A. Shaw
Keyword(s):  
Mixed Phase ◽  
Ice Particles ◽  
Stratiform Clouds ◽  
Long Lifetime

scholarly journals HOLIMO II: a digital holographic instrument for ground-based in-situ observations of microphysical properties of mixed-phase clouds

2013 ◽  
Vol 6 (3) ◽  
pp. 4183-4221 ◽  
Author(s):  
J. Henneberger ◽  
J. P. Fugal ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Mixed Phase ◽  
Size Spectrum ◽  
Research Station ◽  
Resolution Limit ◽  
Microphysical Properties ◽  
Cloud Particles ◽  
Mixed Phase Clouds

Abstract. Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in-situ image cloud particles in a well defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener–Bergeron–Findeisen (WBF) process.

Sign in / Sign up

Export Citation Format

Share Document