Radiative properties of ice crystals within cirrus clouds: application to remote sensing

2004 ◽  
Author(s):  
Ping Yang ◽  
Heli Wei ◽  
Hung-Lung A. Huang ◽  
Bryan A. Baum ◽  
Yong X. Hu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties

scholarly journals Thin and subvisible cirrus and contrails in a subsaturated environment

2011 ◽  
Vol 11 (12) ◽  
pp. 5853-5865 ◽  
Author(s):  
M. Kübbeler ◽  
M. Hildebrandt ◽  
J. Meyer ◽  
C. Schiller ◽  
Th. Hamburger ◽  
...  
Keyword(s):  
Crystal Size ◽  
Life Time ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Size Spectra ◽  
Ice Clouds ◽  
Frontal Systems ◽  
Ice Crystal Size

Abstract. The frequency of occurrence of cirrus clouds and contrails, their life time, ice crystal size spectra and thus their radiative properties depend strongly on the ambient distribution of the relative humidity with respect to ice (RHice). Ice clouds do not form below a certain supersaturation and both cirrus and contrails need at least saturation conditions to persist over a longer period. Under subsaturated conditions, cirrus and contrails should dissipate. During the mid-latitude aircraft experiment CONCERT 2008 (CONtrail and Cirrus ExpeRimenT), RHice and ice crystals were measured in cirrus and contrails. Here, we present results from 2.3/1.7 h of observation in cirrus/contrails during 6 flights. Thin and subvisible cirrus with contrails embedded therein have been detected frequently in a subsaturated environment. Nevertheless, ice crystals up to radii of 50 μm and larger, but with low number densities were often observed inside the contrails as well as in the cirrus. Analysis of the meteorological situation indicates that the crystals in the contrails were entrained from the thin/subvisible cirrus clouds, which emerged in frontal systems with low updrafts. From model simulations of cirrus evaporation times it follows that such thin/subvisible cirrus can exist for time periods of a couple of hours and longer in a subsaturated environment and thus may represent a considerable part of the cirrus coverage.

scholarly journals Thin and subvisible cirrus and contrails in a subsaturated environment

2010 ◽  
Vol 10 (12) ◽  
pp. 31153-31186 ◽  
Author(s):  
M. Kübbeler ◽  
M. Hildebrandt ◽  
J. Meyer ◽  
C. Schiller ◽  
T. Hamburger ◽  
...  
Keyword(s):  
Crystal Size ◽  
Life Time ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Size Spectra ◽  
Ice Clouds ◽  
Frontal Systems ◽  
Ice Crystal Size

Abstract. The frequency of occurrence of cirrus clouds and contrails, their life time, ice crystal size spectra and thus their radiative properties depend strongly on the ambient distribution of the relative humidity with respect to ice (RHice). Ice clouds do not form below a certain supersaturation and both cirrus and contrails need at least saturation conditions to persist over a longer period. Under subsaturated conditions, cirrus and contrails should dissipate. During the mid-latitude aircraft experiment CONCERT 2008 (CONtrail and Cirrus ExpeRimenT), RHice and ice crystals were measured in cirrus and contrails. Here, we present results from 2.3/1.7 h of observation in cirrus/contrails during 6 flights. Thin and subvisible cirrus with contrails embedded therein have been detected frequently in a subsaturated environment. Nevertheless, ice crystals up to radii of 50 μm and larger, but with low number densities were often observed inside the contrails as well as in the cirrus. Analysis of the meteorological situation indicates that the crystals in the contrails were entrained from the thin/subvisible cirrus clouds, which emerged in frontal systems with low updrafts. From model simulations of cirrus evaporation times it follows that such thin/subvisible cirrus can exist for time periods of a couple of hours and longer in a subsaturated environment and thus may represent a considerable part of the cirrus coverage.

scholarly journals On the Occurrence of Hollow Bullet Rosette– and Column-Shaped Ice Crystals in Midlatitude Cirrus

2007 ◽  
Vol 64 (12) ◽  
pp. 4514-4519 ◽  
Author(s):  
C. G. Schmitt ◽  
A. J. Heymsfield
Keyword(s):  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Cirrus Cloud ◽  
Ice Crystal ◽  
Particle Size Distributions ◽  
Polyvinyl Formal ◽  
Ice Particles ◽  
Cloud Ice ◽  
Parameter Values

Abstract Cirrus clouds in mid- and high latitudes are frequently composed of bullet rosette– and column-shaped ice crystals, which can have hollow ends. Bullet rosette–shaped ice crystals are composed of a number of bullets radiating from a central point. Research has shown that the light-scattering properties of ice particles with hollow ends are different from the scattering properties of solid ice particles. Knowledge of the frequency of occurrence of hollow particles is important to more accurately calculate the radiative properties of cirrus clouds. This note presents the results of a survey of cirrus cloud ice crystal replicas imaged from balloon-borne Formvar (polyvinyl formal) replicators. Fifty percent to 80% of the replicated bullet rosette– and column-shaped particles had hollow ends. In bullets longer than 150 μm in length, the length of the hollows of the bullets averaged 88% of the total length of the bullet. The combined length of both hollow portions of column-shaped ice crystals varied from 50% of the length of the column for 30-μm-long columns to 80% of the length of the columns longer than 200 μm. Asymmetry parameter values estimated from cirrus cloud aircraft particle size distributions are higher by 0.014 when hollow crystals are considered. This difference leads to a 2.5 W m−2 increase for hollow crystals at the surface for a 0.5 optical depth cloud, demonstrating the importance of the incorporation of hollow particle scattering characteristics into radiative transfer calculations.

Radiative properties of cirrus clouds observed during the European cloud radiation experiment '94 in Brittany by active and passive remote sensing observations

1995 ◽  
Author(s):  
Gerard Brogniez ◽  
Helene Chepfer ◽  
Yves Fouquart ◽  
Jean-Francois Gayet ◽  
Pierre H. Flamant ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Cirrus Clouds ◽  
Radiative Properties ◽  
Passive Remote Sensing

scholarly journals The origin of midlatitude ice clouds and the resulting influence on their microphysical properties

2015 ◽  
Vol 15 (23) ◽  
pp. 34243-34281 ◽  
Author(s):  
A. E. Luebke ◽  
A. Afchine ◽  
A. Costa ◽  
J. Meyer ◽  
C. Rolf ◽  
...  
Keyword(s):  
Bimodal Distribution ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
Ice Crystal Size ◽  
Ice Water

Abstract. The radiative role of ice clouds in the atmosphere is known to be important, but uncertainties remain concerning the magnitude and net effects. However, through measurements of the microphysical properties of cirrus clouds, we can better characterize them, which can ultimately allow for their radiative properties to be more accurately ascertained. It has recently been proposed that there are two types of cirrus clouds – in situ and liquid origin. In this study, we present observational evidence to show that two distinct types of cirrus do exist. Airborne, in situ measurements of cloud ice water content (IWC), ice crystal concentration (Nice), and ice crystal size from the 2014 ML-CIRRUS campaign provide cloud samples that have been divided according to their origin type. The key features that set liquid origin cirrus apart from the in situ origin cirrus are a higher frequency of high IWC (> 100 ppmv), higher Nice values, and larger ice crystals. A vertical distribution of Nice shows that the in situ origin cirrus clouds exhibit a median value of around 0.1 cm−3, while the liquid origin concentrations are slightly, but notably higher. The median sizes of the crystals contributing the most mass are less than 200 μm for in situ origin cirrus, with some of the largest crystals reaching 550 μm in size. The liquid origin cirrus, on the other hand, were observed to have median diameters greater than 200 μm, and crystals that were up to 750 μm. An examination of these characteristics in relation to each other and their relationship to temperature provides strong evidence that these differences arise from the dynamics and conditions in which the ice crystals formed. Additionally, the existence of these two groups in cirrus cloud populations may explain why a bimodal distribution in the IWC-temperature relationship has been observed. We hypothesize that the low IWC mode is the result of in situ origin cirrus and the high IWC mode is the result of liquid origin cirrus.

scholarly journals The origin of midlatitude ice clouds and the resulting influence on their microphysical properties

2016 ◽  
Vol 16 (9) ◽  
pp. 5793-5809 ◽  
Author(s):  
Anna E. Luebke ◽  
Armin Afchine ◽  
Anja Costa ◽  
Jens-Uwe Grooß ◽  
Jessica Meyer ◽  
...  
Keyword(s):  
Bimodal Distribution ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
Ice Crystal Size ◽  
Ice Water

Abstract. The radiative role of ice clouds in the atmosphere is known to be important, but uncertainties remain concerning the magnitude and net effects. However, through measurements of the microphysical properties of cirrus clouds, we can better characterize them, which can ultimately allow for their radiative properties to be more accurately ascertained. Recently, two types of cirrus clouds differing by formation mechanism and microphysical properties have been classified – in situ and liquid origin cirrus. In this study, we present observational evidence to show that two distinct types of cirrus do exist. Airborne, in situ measurements of cloud ice water content (IWC), ice crystal concentration (Nice), and ice crystal size from the 2014 ML-CIRRUS campaign provide cloud samples that have been divided according to their origin type. The key features that set liquid origin cirrus apart from the in situ origin cirrus are higher frequencies of high IWC ( > 100 ppmv), higher Nice values, and larger ice crystals. A vertical distribution of Nice shows that the in situ origin cirrus clouds exhibit a median value of around 0.1 cm−3, while the liquid origin concentrations are slightly, but notably higher. The median sizes of the crystals contributing the most mass are less than 200 µm for in situ origin cirrus, with some of the largest crystals reaching 550 µm in size. The liquid origin cirrus, on the other hand, were observed to have median diameters greater than 200 µm, and crystals that were up to 750 µm. An examination of these characteristics in relation to each other and their relationship to temperature provides strong evidence that these differences arise from the dynamics and conditions in which the ice crystals formed. Additionally, the existence of these two groups in cirrus cloud populations may explain why a bimodal distribution in the IWC-temperature relationship has been observed. We hypothesize that the low IWC mode is the result of in situ origin cirrus and the high IWC mode is the result of liquid origin cirrus.

scholarly journals Cirrus Clouds

2017 ◽  
Vol 58 ◽  
pp. 2.1-2.26 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Martina Krämer ◽  
Anna Luebke ◽  
Phil Brown ◽  
Daniel J. Cziczo ◽  
...  
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Ice Nucleation ◽  
In Situ Measurements ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Formation Mechanisms ◽  
Wide Range

Abstract The goal of this chapter is to synthesize information about what is now known about one of the three main types of clouds, cirrus, and to identify areas where more knowledge is needed. Cirrus clouds, composed of ice particles, form in the upper troposphere, where temperatures are generally below −30°C. Satellite observations show that the maximum-occurrence frequency of cirrus is near the tropics, with a large latitudinal movement seasonally. In situ measurements obtained over a wide range of cirrus types, formation mechanisms, temperatures, and geographical locations indicate that the ice water content and particle size generally decrease with decreasing temperature, whereas the ice particle concentration is nearly constant or increases slightly with decreasing temperature. High ice concentrations, sometimes observed in strong updrafts, result from homogeneous nucleation. The satellite-based and in situ measurements indicate that cirrus ice crystals typically differ from the simple, idealized geometry for smooth hexagonal shapes, indicating complexity and/or surface roughness. Their shapes significantly impact cirrus radiative properties and feedbacks to climate. Cirrus clouds, one of the most uncertain components of general circulation models (GCM), pose one of the greatest challenges in predicting the rate and geographical pattern of climate change. Improved measurements of the properties and size distributions and surface structure of small ice crystals (about 20 μm) and identifying the dominant ice nucleation process (heterogeneous versus homogeneous ice nucleation) under different cloud dynamical forcings will lead to a better representation of their properties in GCM and in modeling their current and future effects on climate.

Radiative Transfer in Cirrus Clouds: Light Scatting and Spectral Information

Cirrus ◽  
2002 ◽  
Author(s):  
K.N. Liou ◽  
Y. Gu
Keyword(s):  
Radiative Transfer ◽  
Cloud Cover ◽  
Climate Models ◽  
The United States ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Ice Particles ◽  
Ground Based Lidar ◽  
Composition Structure

The importance of cirrus clouds in climate has been recognized in the light of a number of intensive composite field observations: the First ISCCP Regional Experiment (FIRE) I in October-November 1986; FIRE II in November-December 1991; the European experiment on cirrus (ICE/EUCREX) in 1989; Subsonic Aircraft: Contrail and Cloud Effect Special Study (SUCCESS) in April 1996. Based on observations from the ground-based lidar and radar, airborne instrumentation, and satellites, cirrus clouds are typically located in the upper troposphere and lower stratosphere (Liou 1986). The formation, maintenance, and dissipation of cirrus clouds are directly associated with synoptic and mesoscale disturbances as well as related to deep cumulus outflows. Increases of high cloud cover have been reported at a number of urban airports in the United States based on surface observations spanning 40 years (Liou et al. 1990; Frankel et al. 1997). These increases have been attributed to the contrails and water vapor produced by jet airplane traffic. Satellite observations from NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) using the CO2 slicing method (Wylie et al. 1994) also show that cirrus cloud cover substantially increased between 60° S and 60° N during a 4-year period from June 1989 to September 1993. Understanding the role of cirrus clouds in climate must begin with reliable modeling of their radiative properties for incorporation in climate models as well as determination of the global variability of their composition, structure, and optical properties. Development of the remote sensing methodologies for the detection and retrieval of the ubiquitous visible and subvisual cirrus clouds requires the basic scattering, absorption, and polarization data for ice crystals in conjunction with appropriate radiative transfer models. We present the fundamentals involving radiative transfer in cirrus clouds and review pertinent research. In section 13.1, an overview of the subject of light scattering by ice crystals is presented in which we discuss a unification of the geometric optics approach for large ice particles and the finite-difference time domain numerical solution for small ice particles, referred to as the unified theory. Section 13.2 presents radiative transfer in cirrus clouds involving two unique properties: orientation of nonspherical ice crystals and cloud inhomogeneity.

scholarly journals Influence of crystal shapes on radiative fluxes in visible wavelength: ice crystals randomly oriented in space

1996 ◽  
Vol 14 (8) ◽  
pp. 837-844 ◽  
Author(s):  
P. Chervet ◽  
H. Isaka ◽  
T. Nakajima
Keyword(s):  
Cirrus Clouds ◽  
Ice Crystals ◽  
Radiative Properties ◽  
Radiation Budget ◽  
Shape Effect ◽  
Crystal Shape ◽  
Ice Crystal ◽  
Radiative Fluxes ◽  
Crystal Shapes ◽  
Scattering Phase

Abstract. Radiative properties of cirrus clouds are one of the major unsolved problems in climate studies and global radiation budget. These clouds are generally composed of various ice-crystal shapes, so we tried to evaluate effects of the ice-crystal shape on radiative fluxes. We calculated radiative fluxes of cirrus clouds with a constant geometrical depth, composed of ice crystals with different shapes (hexagonal columns, bullets, bullet-rosettes), sizes and various concentrations. We considered ice particles randomly oriented in space (3D case) and their scattering phase functions were calculated by a ray-tracing method. We calculated radiative fluxes for cirrus layers for different microphysical characteristics by using a discrete-ordinate radiative code. Results showed that the foremost effect of the ice-crystal shape on radiative properties of cirrus clouds was that on the optical thickness, while the variation of the scattering phase function with the ice shape remained less than 3% for our computations. The ice-water content may be a better choice to parameterize the optical properties of cirrus, but the shape effect must be included.

scholarly journals Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study

2004 ◽  
Vol 4 (5) ◽  
pp. 1255-1263 ◽  
Author(s):  
B. Mayer ◽  
M. Schröder ◽  
R. Preusker ◽  
L. Schüller
Keyword(s):  
Remote Sensing ◽  
Size Distribution ◽  
Droplet Size ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Single Scattering ◽  
Effective Radius ◽  
Radiative Properties ◽  
High Angular Resolution ◽  
Size Distributions

Abstract. Cloud single scattering properties are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI) in 180° backscatter geometry, we found that high angular resolution aircraft observations of the glory provide unique new information which is not available from traditional remote sensing techniques: Using only one single wavelength, 753nm, we were able to determine not only optical thickness and effective radius, but also the width of the size distribution at cloud top. Applying this novel technique to the ACE-2 CLOUDYCOLUMN experiment, we found that the size distributions were much narrower than usually assumed in radiation calculations which is in agreement with in-situ observations during this campaign. While the shape of the size distribution has only little relevance for the radiative properties of clouds, it is extremely important for understanding their formation and evolution.

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