The THz imager instrument for ice cloud remote sensing

2021 ◽  
Author(s):  
Shuai Dong ◽  
Zhenzhan Wang ◽  
Shengwei Zhang ◽  
Wensi Zhai ◽  
Bin Li
Keyword(s):  
Remote Sensing ◽  
Ice Cloud

scholarly journals Developing and bounding ice particle mass- and area-dimension expressions for use in atmospheric models and remote sensing

2016 ◽  
Vol 16 (7) ◽  
pp. 4379-4400 ◽  
Author(s):  
Ehsan Erfani ◽  
David L. Mitchell
Keyword(s):  
Remote Sensing ◽  
Power Laws ◽  
Field Studies ◽  
Particle Mass ◽  
Atmospheric Models ◽  
Cloud Particle ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Cloud Properties ◽  
Probe Measurements

Abstract. Ice particle mass- and projected area-dimension (m-D and A-D) power laws are commonly used in the treatment of ice cloud microphysical and optical properties and the remote sensing of ice cloud properties. Although there has long been evidence that a single m-D or A-D power law is often not valid over all ice particle sizes, few studies have addressed this fact. This study develops self-consistent m-D and A-D expressions that are not power laws but can easily be reduced to power laws for the ice particle size (maximum dimension or D) range of interest, and they are valid over a much larger D range than power laws. This was done by combining ground measurements of individual ice particle m and D formed at temperature T  <  −20 °C during a cloud seeding field campaign with 2-D stereo (2D-S) and cloud particle imager (CPI) probe measurements of D and A, and estimates of m, in synoptic and anvil ice clouds at similar temperatures. The resulting m-D and A-D expressions are functions of temperature and cloud type (synoptic vs. anvil), and are in good agreement with m-D power laws developed from recent field studies considering the same temperature range (−60 °C  <  T  <  −20 °C).

scholarly journals Airborne observations of a subvisible midlevel Arctic ice cloud: microphysical and radiative characterization

2009 ◽  
Vol 9 (1) ◽  
pp. 595-634
Author(s):  
A. Lampert ◽  
A. Ehrlich ◽  
A. Dörnbrack ◽  
O. Jourdan ◽  
J.-F. Gayet ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Thermal Infrared ◽  
Airborne Lidar ◽  
Radiative Properties ◽  
The Arctic ◽  
Cloud Base ◽  
Effective Diameter ◽  
Ice Cloud ◽  
Tropospheric Aerosol

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed at around 3 km altitude south of Svalbard. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in-situ instruments. Collocated airborne lidar remote-sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in-situ sensors roughly 30 min later. From individual ice crystal samples detected with the Cloud Particle Imager and the ensemble of particles measured with the Polar Nephelometer, we retrieved the single-scattering albedo, the scattering phase function as well as the volume extinction coefficient and the effective diameter of the crystal population. Furthermore, a lidar ratio of 21 (±6) sr was deduced by two independent methods. These parameters in conjunction with the cloud optical thickness obtained from the lidar measurements were used to compute spectral and broadband radiances and irradiances with a radiative transfer code. The simulated results agreed with the observed spectral downwelling radiance within the range given by the measurement uncertainty. Furthermore, the broadband radiative simulations estimated a net (solar plus thermal infrared) radiative forcing of the subvisible midlevel ice cloud of −0.4 W m−2 (−3.2 W m−2 in the solar and +2.8 W m−2 in the thermal infrared wavelength range).

scholarly journals Comparison of Airborne In Situ, Airborne Radar–Lidar, and Spaceborne Radar–Lidar Retrievals of Polar Ice Cloud Properties Sampled during the POLARCAT Campaign

2013 ◽  
Vol 30 (1) ◽  
pp. 57-73 ◽  
Author(s):  
Julien Delanoë ◽  
Alain Protat ◽  
Olivier Jourdan ◽  
Jacques Pelon ◽  
Mathieu Papazzoni ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Process Analysis ◽  
Airborne Radar ◽  
Ice Cloud ◽  
Cloud Properties ◽  
Ice Water Content ◽  
Surface Measurements ◽  
Ice Water ◽  
Spaceborne Radar

Abstract This study illustrates the high potential of RALI, the French airborne radar–lidar instrument, for studying cloud processes and evaluating satellite products when satellite overpasses are available. For an Arctic nimbostratus ice cloud collected on 1 April 2008 during the Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport (POLARCAT) campaign, the capability of this synergistic instrument to retrieve cloud properties and to characterize the cloud phase at scales smaller than a kilometer, which is crucial for cloud process analysis, is demonstrated. A variational approach, which combines radar and lidar, is used to retrieve the ice-water content (IWC), extinction, and effective radius. The combination of radar and lidar is shown to provide better retrievals than do stand-alone methods and, in general, the radar overestimates and the lidar underestimates IWC. As the sampled ice cloud was simultaneously observed by CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites, a new way to assess satellite cloud products by combining in situ and active remote sensing measurements is identified. It was then possible to compare RALI to three satellite ice cloud products: CloudSat, CALIPSO, and the Cloud-Aerosol-Water-Radiation Interactions (ICARE) center’s radar–lidar project (DARDAR).

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 Developing and bounding ice particle mass- and area-dimension expressions for use in atmospheric models and remote sensing

2015 ◽  
Vol 15 (20) ◽  
pp. 28517-28573 ◽  
Author(s):  
E. Erfani ◽  
D. L. Mitchell
Keyword(s):  
Remote Sensing ◽  
Field Measurements ◽  
Power Laws ◽  
Field Studies ◽  
Particle Mass ◽  
Atmospheric Models ◽  
Cloud Particle ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Cloud Properties

Abstract. Ice particle mass- and projected area-dimension (m-D and A-D) power laws are commonly used in the treatment of ice cloud microphysical and optical properties and the remote sensing of ice cloud properties. Although there has long been evidence that a single m-D or A-D power law is often not valid over all ice particle sizes, few studies have addressed this fact. This study develops self-consistent m-D and A-D expressions that are not power laws, but can easily be reduced to power laws for the ice particle size (maximum dimension or D) range of interest, and they are valid over a much larger D range than power laws. This was done by combining field measurements of individual ice particle m and D formed at temperature T < −20 °C with 2-dimensional stereo (2D-S) and Cloud Particle Imager (CPI) probe measurements (or estimates) of D, A and m in synoptic and anvil ice clouds at similar temperatures. The resulting m-D and A-D expressions are functions of temperature and cloud type (synoptic vs. anvil), and are in good agreement with m-D power laws developed from recent field studies considering the same temperature range (−60 °C < T < −20 °C).

Simulation of remote sensing of clouds and humidity from space using a combined platform of radar and multi-frequency microwave radiometers

2020 ◽  
Author(s):  
Jonathan Jiang ◽  
Hui Su ◽  
Qing Yue ◽  
Pekka Kangaslahti
Keyword(s):  
Remote Sensing ◽  
Effective Diameter ◽  
Cloud Particle ◽  
Ice Cloud ◽  
Cloud Properties ◽  
Thermodynamic Conditions ◽  
Ice Water Content ◽  
Microwave Radiometers ◽  
Cloud Ice ◽  
Ice Water

&lt;p&gt;We present a simulated simultaneous retrieval of mass mean cloud ice particle effective diameter, ice water content, water vapor, and temperature profiles using a combination of a 94-GHz cloud radar and multi-frequency (118, 183, 240, 310, 380, 664, and 850 GHz) millimeter- and submillimeter-wave radiometers from a space platform. The retrieval capabilities and uncertainties of the combined radar and microwave radiometers are quantified. We show that this combined active and passive remote sensing approach with SmallSat technologies addresses a gap in the current state-of-the-art remote sensing measurements of ice cloud properties, especially deriving vertical profiles of ice cloud particle sizes in the atmosphere together with the ambient thermodynamic conditions. Therefore, this new approach can serve as a plausible candidate for future missions that target cloud and precipitation processes to improve weather forecasts and climate predictions. &amp;#160;&lt;/p&gt;

scholarly journals Microphysical and radiative characterization of a subvisible midlevel Arctic ice cloud by airborne observations – a case study

2009 ◽  
Vol 9 (8) ◽  
pp. 2647-2661 ◽  
Author(s):  
A. Lampert ◽  
A. Ehrlich ◽  
A. Dörnbrack ◽  
O. Jourdan ◽  
J.-F. Gayet ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Thermal Infrared ◽  
Airborne Lidar ◽  
Radiative Properties ◽  
The Arctic ◽  
Cloud Base ◽  
Effective Diameter ◽  
Ice Cloud ◽  
Tropospheric Aerosol

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed south of Svalbard at around 3 km altitude. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in situ instruments. Collocated airborne lidar remote sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in situ sensors roughly 30 min later. From individual ice crystal samples detected with the Cloud Particle Imager and the ensemble of particles measured with the Polar Nephelometer, microphysical properties were retrieved with a bi-modal inversion algorithm. The best agreement with the measurements was obtained for small ice spheres and deeply rough hexagonal ice crystals. Furthermore, the single-scattering albedo, the scattering phase function as well as the volume extinction coefficient and the effective diameter of the crystal population were determined. A lidar ratio of 21(±6) sr was deduced by three independent methods. These parameters in conjunction with the cloud optical thickness obtained from the lidar measurements were used to compute spectral and broadband radiances and irradiances with a radiative transfer code. The simulated results agreed with the observed spectral downwelling radiance within the range given by the measurement uncertainty. Furthermore, the broadband radiative simulations estimated a net (solar plus thermal infrared) radiative forcing of the subvisible midlevel ice cloud of −0.4 W m−2 (−3.2 W m−2 in the solar and +2.8 W m−2 in the thermal infrared wavelength range).

Sign in / Sign up

Export Citation Format

Share Document