First ice cloud effective particle size parameterization based on combined lidar and radar data

2002 ◽  
Vol 29 (1) ◽  
Author(s):  
D. P. Donovan
Keyword(s):  
Particle Size ◽  
Radar Data ◽  
Ice Cloud ◽  
Effective Particle Size ◽  
Effective Particle

Effect of Cavities on the Optical Properties of Bullet Rosettes: Implications for Active and Passive Remote Sensing of Ice Cloud Properties

2008 ◽  
Vol 47 (9) ◽  
pp. 2311-2330 ◽  
Author(s):  
Ping Yang ◽  
Zhibo Zhang ◽  
George W. Kattawar ◽  
Stephen G. Warren ◽  
Bryan A. Baum ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Particle Size ◽  
Phase Function ◽  
Hollow Structure ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Effective Particle Size ◽  
Effective Particle ◽  
Scattering Phase ◽  
Scattering Phase Function

Abstract Bullet rosette particles are common in ice clouds, and the bullets may often be hollow. Here the single-scattering properties of randomly oriented hollow bullet rosette ice particles are investigated. A bullet, which is an individual branch of a rosette, is defined as a hexagonal column attached to a hexagonal pyramidal tip. For this study, a hollow structure is included at the end of the columnar part of each bullet branch and the shape of the hollow structure is defined as a hexagonal pyramid. A hollow bullet rosette may have between 2 and 12 branches. An improved geometric optics method is used to solve for the scattering of light in the particle. The primary optical effect of incorporating a hollow end in each of the bullets is to decrease the magnitude of backscattering. In terms of the angular distribution of scattered energy, the hollow bullets increase the scattering phase function values within the forward scattering angle region from 1° to 20° but decrease the phase function values at side- and backscattering angles of 60°–180°. As a result, the presence of hollow bullets tends to increase the asymmetry factor. In addition to the scattering phase function, the other elements of the phase matrix are also discussed. The backscattering depolarization ratios for hollow and solid bullet rosettes are found to be very different. This may have an implication for active remote sensing of ice clouds, such as from polarimetric lidar measurements. In a comparison of solid and hollow bullet rosettes, the effect of the differences on the retrieval of both the ice cloud effective particle size and optical thickness is also discussed. It is found that the presence of hollow bullet rosettes acts to decrease the inferred effective particle size and to increase the optical thickness in comparison with the use of solid bullet rosettes.

scholarly journals Retrieval of Ice Cloud Optical Thickness and Effective Particle Size Using a Fast Infrared Radiative Transfer Model

2011 ◽  
Vol 50 (11) ◽  
pp. 2283-2297 ◽  
Author(s):  
Chenxi Wang ◽  
Ping Yang ◽  
Bryan A. Baum ◽  
Steven Platnick ◽  
Andrew K. Heidinger ◽  
...  
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Distribution Method ◽  
Ice Cloud ◽  
Effective Particle Size ◽  
Effective Particle ◽  
Cloud Optical Thickness

AbstractA computationally efficient radiative transfer model (RTM) is developed for the inference of ice cloud optical thickness and effective particle size from satellite-based infrared (IR) measurements and is aimed at potential use in operational cloud-property retrievals from multispectral satellite imagery. The RTM employs precomputed lookup tables to simulate the top-of-the-atmosphere (TOA) radiances (or brightness temperatures) at 8.5-, 11-, and 12-μm bands. For the clear-sky atmosphere, the optical thickness of each atmospheric layer resulting from gaseous absorption is derived from the correlated-k-distribution method. The cloud reflectance, transmittance, emissivity, and effective temperature are precomputed using the Discrete Ordinate Radiative Transfer model (DISORT). For an atmosphere containing a semitransparent ice cloud layer with a visible optical thickness τ smaller than 5, the TOA brightness temperature differences (BTDs) between the fast model and the more rigorous DISORT results are less than 0.1 K, whereas the BTDs are less than 0.01 K if τ is larger than 10. With the proposed RTM, the cloud optical and microphysical properties are retrieved from collocated observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) in conjunction with the Modern Era Retrospective-Analysis for Research and Applications (MERRA) data. Comparisons between the retrieved ice cloud properties (optical thickness and effective particle size) based on the present IR fast model and those from the Aqua/MODIS operational collection-5 cloud products indicate that the IR retrievals are smaller. A comparison between the IR-retrieved ice water path (IWP) and CALIOP-retrieved IWP shows robust agreement over most of the IWP range.

scholarly journals Influence of Cloud-Top Height and Geometric Thickness on a MODIS Infrared-Based Ice Cloud Retrieval

2009 ◽  
Vol 48 (4) ◽  
pp. 818-832 ◽  
Author(s):  
Kevin J. Garrett ◽  
Ping Yang ◽  
Shaima L. Nasiri ◽  
Christopher R. Yost ◽  
Bryan A. Baum
Keyword(s):  
Particle Size ◽  
Optical Thickness ◽  
Lookup Table ◽  
Infrared Observation ◽  
Ice Cloud ◽  
Brightness Temperatures ◽  
Effective Particle Size ◽  
Effective Particle ◽  
Level 2 ◽  
Geometric Thickness

Abstract The retrieval of ice cloud microphysical and optical properties from satellite-based infrared observation remains a challenging research topic, partly because of the sensitivity of observed infrared radiances to many surface and atmospheric parameters that vary on fine spatial and temporal scales. In this study, the sensitivity of an infrared-based ice cloud retrieval to effective cloud temperature is investigated, with a focus on the effects of cloud-top height and geometric thickness. To illustrate the sensitivity, the authors first simulate brightness temperatures at 8.5 and 11.0 μm using the discrete ordinates radiative transfer (DISORT) model for five cloud-top heights ranging from 8 to 16 km and for varying cloud geometric thicknesses of 1, 2, 3, and 5 km. The simulations are performed across a range of visible optical thicknesses from 0.1 to 10 and ice cloud effective diameters from 30 to 100 μm. Furthermore, the effective particle size and optical thickness of ice clouds are retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) measurements on the basis of a lookup-table approach. Specifically, the infrared brightness temperatures are simulated from the collocated Atmospheric Infrared Sounder (AIRS) level-2 product at 28 atmospheric levels and prescribed ice cloud parameters. Variations of the retrieved effective particle size and optical thickness versus cloud-top height and geometric thickness are investigated. Results show that retrievals based on the 8.5- and 11.0-μm bispectral approach are most valid for cloud-top temperatures of less than 224 K with visible optical thickness values between 2 and 5. The present retrievals are also compared with the collection-5 MODIS level-2 ice cloud product.

Effects of Process Parameters on the Particle Size Distribution of Graphene Oxide Aqueous Dispersion

2013 ◽  
Vol 750-752 ◽  
pp. 1113-1116 ◽  
Author(s):  
Xue Bing Hu ◽  
Yun Yu ◽  
Jian Er Zhou ◽  
Li Xin Song
Keyword(s):  
Particle Size ◽  
Graphene Oxide ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Ultrasonic Treatment ◽  
Treatment Time ◽  
Aqueous Dispersion ◽  
Centrifugal Separation ◽  
Effective Particle Size ◽  
Effective Particle

During graphene oxide separation process, the effects of the process parameters such as centrifugal separation time and ultrasonic treatment time on the particle size distribution of graphene oxide aqueous dispersion were studied. The results show graphene oxide has the narrower particle size distribution and the smaller nominal effective particle size with increasing the centrifugal separation time from 20 min to 160 min. And there is a critical time in the ultrasonic treatment to obtain the narrower particle size distribution and smaller nominal effective particle size of graphene oxide. Graphene oxide has the narrower particle size distribution and the smaller nominal effective particle size when the ultrasonic treatment time is 4 h.

The Effect of Surfactant and Suspending Agent Concentration on the Effective Particle Size of Metered-dose Inhalers

1997 ◽  
Vol 49 (12) ◽  
pp. 1175-1177 ◽  
Author(s):  
L. T. FEDINA ◽  
R. ZELKÓ ◽  
L. I. FEDINA ◽  
Z. S. SZABADOS ◽  
M. SZÁNTÓ ◽  
...  
Keyword(s):  
Particle Size ◽  
Metered Dose Inhalers ◽  
Effective Particle Size ◽  
Effective Particle ◽  
Metered Dose
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