scholarly journals Bulk microphysical properties of semi-transparent cirrus from AIRS: a six year global climatology and statistical analysis in synergy with geometrical profiling data from CloudSat-CALIPSO

2012 ◽  
Vol 12 (1) ◽  
pp. 503-525 ◽  
Author(s):  
A. Guignard ◽  
C. J. Stubenrauch ◽  
A. J. Baran ◽  
R. Armante
Keyword(s):  
Statistical Analysis ◽  
Single Scattering ◽  
Ice Crystals ◽  
Crystal Habit ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Mean Values ◽  
Temperature Range ◽  
Microphysical Properties ◽  
Ice Water

Abstract. This article presents a retrieval method and a statistical analysis of the bulk microphysical properties of semi-transparent ice clouds using the Atmospheric Infrared Sounder (AIRS). The method relies on spectral differences of cirrus emissivities in the 8–12 μm range and is sensitive to the effective ice crystal diameter (De) and ice water path (IWP) of up to 85 μm and 120 g m−2, respectively. An indication of the most frequent ice crystal habit in the cirrus has been obtained by using separately single scattering properties of column-like and aggregate-like ice crystals in the simulations. Uncertainties due to hypotheses on atmospheric parameters and ice crystal single scattering properties are discussed and the cirrus emissivity and temperature range for the applicability of the method are determined. To be sure that the cirrus only includes ice crystals, one has to restrict the cloud temperature range to Tcld<230 K. On a global scale, these semi-transparent ice clouds (cirrus) represent about 25% of all high clouds and are mainly encountered in the midlatitudes during winter and in the tropics, with an average De and IWP of 52 μm and 27 g m−2, respectively. A comparison with bulk microphysical properties from the TIROS-N Operational Vertical Sounder (TOVS) shows an agreement on global mean values. The addition of spectral information revealed improvements at the limits of the cirrus emissivity range. Collocated Radar-Lidar Geometrical Profiling (GEOPROF) data have been used to study the vertical structure of these clouds and to infer average ice water content (IWC) for cirrus with a small vertical extent. This allowed us to compare and contrast parameterizations of De as functions of IWC and IWP, respectively.

scholarly journals Bulk microphysical properties of semi transparent cirrus from AIRS: a six years global climatology and statistical analysis in synergy with CALIPSO and CloudSat

2011 ◽  
Vol 11 (9) ◽  
pp. 24671-24725
Author(s):  
A. Guignard ◽  
C. J. Stubenrauch ◽  
A. J. Baran ◽  
R. Armante
Keyword(s):  
Statistical Analysis ◽  
General Circulation ◽  
General Circulation Models ◽  
Single Scattering ◽  
Ice Crystals ◽  
Effective Diameter ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
Ice Water

Abstract. This article presents a retrieval method and a statistical analysis of the bulk micropysical properties of semi-transparent ice clouds using the Atmospheric Infrared Sounder (AIRS). Global and long-term coverage provides information on the effective diameter (De) and habits of ice crystals in relation with their environment, ice water path (IWP) and temperature. The method relies on spectral absorption differences between 8 and 12 μm that depend on ice crystal properties. Using single scattering properties for column-like or aggregate-like ice crystals, the method is sensitive to De of up to 85 μm and IWP of up to 120 g m−2. Uncertainties due to the hypotheses on atmospheric parameters and ice crystal single scattering properties as well as horizontal heterogeneities have been demonstrated to be small. The behaviour of bulk microphysical properties as a function of temperature demonstrates that pure ice clouds only occur when Tcld<230 K. On a global scale, these clouds represent practically 25 % of all high clouds and are mainly encountered in the mid-latitudes during winter and in the tropics. Colocated Radar-Lidar Geometrical Profiling (GEOPROF) data reveal an increase in the vertical extent of these cloud layers during mid-latitude winter but which does not significantly impact ice crystal characteristics. A comparative study with bulk microphysical properties from the TIROS-N Operational Vertical Sounder (TOVS) reveals improvements, especially for optically thin and thick semi-transparent ice clouds. Finally, we investigated parametrizations of De as a function of IWP or Ice Water Content (IWC), which could be useful for modelling cirrus in General Circulation Models.

Microphysical Properties of Ice Crystal Precipitation and Surface-Generated Ice Crystals in a High Alpine Environment in Switzerland

2017 ◽  
Vol 56 (2) ◽  
pp. 433-453 ◽  
Author(s):  
Oliver Schlenczek ◽  
Jacob P. Fugal ◽  
Gary Lloyd ◽  
Keith N. Bower ◽  
Thomas W. Choularton ◽  
...  
Keyword(s):  
Ice Crystals ◽  
Crystal Habit ◽  
The Arctic ◽  
Spatial And Temporal Variability ◽  
Research Station ◽  
Size Distributions ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
The Individual

AbstractDuring the Cloud and Aerosol Characterization Experiment (CLACE) 2013 field campaign at the High Altitude Research Station Jungfraujoch, Switzerland, optically thin pure ice clouds and ice crystal precipitation were measured using holographic and other in situ particle instruments. For cloud particles, particle images, positions in space, concentrations, and size distributions were obtained, allowing one to extract size distributions classified by ice crystal habit. Small ice crystals occurring under conditions with a vertically thin cloud layer above and a stratocumulus layer approximately 1 km below exhibit similar properties in size and crystal habits as Antarctic/Arctic diamond dust. Also, ice crystal precipitation stemming from midlevel clouds subsequent to the diamond dust event was observed with a larger fraction of ice crystal aggregates when compared with the diamond dust. In another event, particle size distributions could be derived from mostly irregular ice crystals and aggregates, which likely originated from surface processes. These particles show a high spatial and temporal variability, and it is noted that size and habit distributions have only a weak dependence on the particle number concentration. Larger ice crystal aggregates and rosette shapes of some hundred microns in maximum dimension could be sampled as a precipitating cirrostratus cloud passed the site. The individual size distributions for each habit agree well with lognormal distributions. Fitted parameters to the size distributions are presented along with the area-derived ice water content, and the size distributions are compared with other measurements of pure ice clouds made in the Arctic and Antarctic.

scholarly journals Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 μm

2013 ◽  
Vol 70 (1) ◽  
pp. 330-347 ◽  
Author(s):  
Ping Yang ◽  
Lei Bi ◽  
Bryan A. Baum ◽  
Kuo-Nan Liou ◽  
George W. Kattawar ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Single Scattering ◽  
Dipole Approximation ◽  
Ice Crystals ◽  
Crystal Habit ◽  
Ice Crystal ◽  
Particle Volume ◽  
Ice Clouds ◽  
Sensing Applications ◽  
Data Library

Abstract A data library is developed containing the scattering, absorption, and polarization properties of ice particles in the spectral range from 0.2 to 100 μm. The properties are computed based on a combination of the Amsterdam discrete dipole approximation (ADDA), the T-matrix method, and the improved geometric optics method (IGOM). The electromagnetic edge effect is incorporated into the extinction and absorption efficiencies computed from the IGOM. A full set of single-scattering properties is provided by considering three-dimensional random orientations for 11 ice crystal habits: droxtals, prolate spheroids, oblate spheroids, solid and hollow columns, compact aggregates composed of eight solid columns, hexagonal plates, small spatial aggregates composed of 5 plates, large spatial aggregates composed of 10 plates, and solid and hollow bullet rosettes. The maximum dimension of each habit ranges from 2 to 10 000 μm in 189 discrete sizes. For each ice crystal habit, three surface roughness conditions (i.e., smooth, moderately roughened, and severely roughened) are considered to account for the surface texture of large particles in the IGOM applicable domain. The data library contains the extinction efficiency, single-scattering albedo, asymmetry parameter, six independent nonzero elements of the phase matrix (P11, P12, P22, P33, P43, and P44), particle projected area, and particle volume to provide the basic single-scattering properties for remote sensing applications and radiative transfer simulations involving ice clouds. Furthermore, a comparison of satellite observations and theoretical simulations for the polarization characteristics of ice clouds demonstrates that ice cloud optical models assuming severely roughened ice crystals significantly outperform their counterparts assuming smooth ice crystals.

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 Direct comparisons of ice cloud macro- and microphysical properties simulated by the Community Atmosphere Model version 5 with HIPPO aircraft observations

2017 ◽  
Vol 17 (7) ◽  
pp. 4731-4749 ◽  
Author(s):  
Chenglai Wu ◽  
Xiaohong Liu ◽  
Minghui Diao ◽  
Kai Zhang ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Ice Nucleation ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Model Version ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Ice Water

Abstract. In this study we evaluate cloud properties simulated by the Community Atmosphere Model version 5 (CAM5) using in situ measurements from the HIAPER Pole-to-Pole Observations (HIPPO) campaign for the period of 2009 to 2011. The modeled wind and temperature are nudged towards reanalysis. Model results collocated with HIPPO flight tracks are directly compared with the observations, and model sensitivities to the representations of ice nucleation and growth are also examined. Generally, CAM5 is able to capture specific cloud systems in terms of vertical configuration and horizontal extension. In total, the model reproduces 79.8 % of observed cloud occurrences inside model grid boxes and even higher (94.3 %) for ice clouds (T ≤ −40 °C). The missing cloud occurrences in the model are primarily ascribed to the fact that the model cannot account for the high spatial variability of observed relative humidity (RH). Furthermore, model RH biases are mostly attributed to the discrepancies in water vapor, rather than temperature. At the micro-scale of ice clouds, the model captures the observed increase of ice crystal mean sizes with temperature, albeit with smaller sizes than the observations. The model underestimates the observed ice number concentration (Ni) and ice water content (IWC) for ice crystals larger than 75 µm in diameter. Modeled IWC and Ni are more sensitive to the threshold diameter for autoconversion of cloud ice to snow (Dcs), while simulated ice crystal mean size is more sensitive to ice nucleation parameterizations than to Dcs. Our results highlight the need for further improvements to the sub-grid RH variability and ice nucleation and growth in the model.

scholarly journals Direct comparisons of ice cloud macro- and microphysical properties simulated by the Community Atmosphere Model version 5 with HIPPO aircraft observations

2017 ◽  
Author(s):  
Chenglai Wu ◽  
Xiaohong Liu ◽  
Minghui Diao ◽  
Kai Zhang ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Ice Nucleation ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Model Version ◽  
Microphysical Properties ◽  
Cloud Properties ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Ice Water

Abstract. In this study we evaluate cloud properties simulated by the Community Atmosphere Model Version 5 (CAM5) using in-situ measurements from the HIAPER Pole-to-Pole Observations (HIPPO) for the period of 2009 to 2011. The modeled wind and temperature are nudged towards reanalysis. Model results collocated with HIPPO flight tracks are directly compared with the observations, and model sensitivities to the representations of ice nucleation and growth are also examined. Generally, CAM5 is able to capture specific cloud systems in terms of vertical configuration and horizontal extension. In total, the model reproduces 79.8 % of observed cloud occurrences inside model grid boxes, and even higher (94.3 %) for ice clouds (T ≤ −40 °C). The missing cloud occurrences in the model are primarily ascribed to the fact that the model cannot account for the high spatial variability of observed relative humidity (RH). Furthermore, model RH biases are mostly attributed to the discrepancies in water vapor, rather than temperature. At the micro-scale of ice clouds, the model captures the observed increase of ice crystal mean sizes with temperature, albeit with smaller sizes than the observations. The model underestimates the observed ice number concentration (Ni) and ice water content (IWC) for ice crystals larger than 75 μm in diameter. Modeled IWC and Ni are more sensitive to the threshold diameter for autoconversion of cloud ice to snow (Dcs), while simulated ice crystal mean size is more sensitive to ice nucleation parameterizations than to Dcs. Our results highlight the need for further improvements to the sub-grid RH variability and ice nucleation and growth in the model.

scholarly journals Disk and circumsolar radiances in the presence of ice clouds

2017 ◽  
Vol 17 (11) ◽  
pp. 6865-6882 ◽  
Author(s):  
Päivi Haapanala ◽  
Petri Räisänen ◽  
Greg M. McFarquhar ◽  
Jussi Tiira ◽  
Andreas Macke ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Ice Crystals ◽  
Crystal Habit ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
The Sun ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Cloud ◽  
The Impact

Abstract. The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8° from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPARTICUS) campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements obtained by the Sun and Aureole Measurements (SAM) instrument. First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 %) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.

scholarly journals Vertical distribution of microphysical properties of Arctic springtime low-level mixed-phase clouds over the Greenland and Norwegian seas

2017 ◽  
Vol 17 (20) ◽  
pp. 12845-12869 ◽  
Author(s):  
Guillaume Mioche ◽  
Olivier Jourdan ◽  
Julien Delanoë ◽  
Christophe Gourbeyre ◽  
Guy Febvre ◽  
...  
Keyword(s):  
Liquid Water ◽  
Crystal Size ◽  
Ice Crystals ◽  
Vertical Profiles ◽  
Liquid Droplets ◽  
Ice Crystal ◽  
Mean Values ◽  
Microphysical Properties ◽  
Ice Crystal Size ◽  
Mixed Phase Clouds

Abstract. This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPCs). We compiled and analyzed cloud in situ measurements from four airborne spring campaigns (representing 18 flights and 71 vertical profiles in MPCs) over the Greenland and Norwegian seas mainly in the vicinity of the Svalbard archipelago. Cloud phase discrimination and representative vertical profiles of the number, size, mass and shape of ice crystals and liquid droplets are established. The results show that the liquid phase dominates the upper part of the MPCs. High concentrations (120 cm−3 on average) of small droplets (mean values of 15 µm), with an averaged liquid water content (LWC) of 0.2 g m−3 are measured at cloud top. The ice phase dominates the microphysical properties in the lower part of the cloud and beneath it in the precipitation region (mean values of 100 µm, 3 L−1 and 0.025 g m−3 for diameter, particle concentration and ice water content (IWC), respectively). The analysis of the ice crystal morphology shows that the majority of ice particles are irregularly shaped or rimed particles; the prevailing regular habits found are stellars and plates. We hypothesize that riming and diffusional growth processes, including the Wegener–Bergeron–Findeisen (WBF) mechanism, are the main growth mechanisms involved in the observed MPCs. The impact of larger-scale meteorological conditions on the vertical profiles of MPC properties was also investigated. Large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations and air mass origins from the south, which can lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling studies are also determined, such as IWC (and LWC) – extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature.

scholarly journals Disk and circumsolar radiances in the presence of ice clouds

2016 ◽  
Author(s):  
Päivi Haapanala ◽  
Petri Räisänen ◽  
Greg M. McFarquhar ◽  
Jussi Tiira ◽  
Andreas Macke ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Ice Crystals ◽  
Crystal Habit ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
The Sun ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Cloud ◽  
The Impact

Abstract. The impact of ice clouds on solar-disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0° to 8° from the center of the Sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements with the Sun and Aureole Measurement (SAM) instrument. First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness was addressed. The angular dependence of the disk and circumsolar radiances was found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in the comparisons with SAM data, the ice-cloud optical thickness was adjusted for each case so that the simulated radiances agreed closely (i.e., within 3 %) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° were systematically underestimated when assuming smooth ice crystals, but the agreement with the measurements was better when rough ice crystals were assumed. Our results suggest that it may well be possible to infer the particle roughness (or more generally, non-ideality) directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.

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