Sensitivity of depolarized lidar signals to cloud and aerosol particle properties

You, Yu; Kattawar, George W.; Yang, Ping; Hu, Yongxiang; Baum, Bryan A.

doi:10.1016/j.jqsrt.2005.11.058

Cited by 39 publications

(27 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After visual inspection of all lidar profiles and as expected due to the low optical depth τ <0.1 (You et al, 2006), multiple scattering can be excluded for this case.…”

Section: Lidar Remote Sensingmentioning

confidence: 78%

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

Lampert

Ehrlich

Dörnbrack³

et al. 2009

Atmos. Chem. Phys.

View full text Add to dashboard Cite

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 Correspondence to: A. Lampert (astrid.lampert@awi.de) 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).

show abstract

“…After visual inspection of all lidar profiles and as expected due to the low optical depth τ <0.1 (You et al, 2006), multiple scattering can be excluded for this case.…”

Section: Lidar Remote Sensingmentioning

confidence: 78%

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

Lampert

Ehrlich

Dörnbrack³

et al. 2009

Atmos. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…This instrument synergy enables the retrieval of a wide range of aerosol and cloud products including: vertically-resolved aerosol and cloud layers, extinction, optical depth, aerosol and cloud type, cloud water phase, cirrus emissivity, and particle size and shape [36,37]. The horizontal resolution is 70 m with an instantaneous field of view (IFOV) sampled at 333 m intervals along the track, and the vertical resolution is 30 m.…”

Section: Instruments and Data Descriptionmentioning

confidence: 99%

The Role of Emissivity in the Detection of Arctic Night Clouds

et al. 2017

View full text Add to dashboard Cite

Detection of clouds over polar areas from satellite radiometric measurements in the visible and IR atmospheric window region is rather difficult because of the high albedo of snow, possible ice covered surfaces, very low humidity, and the usual presence of atmospheric temperature inversion. Cold and highly reflective polar surfaces provide little thermal and visible contrast between clouds and the background surface. Moreover, due to the presence of temperature inversion, clouds are not always identifiable as being colder than the background. In addition, low humidity often causes polar clouds to be optically thin. Finally, polar clouds are usually composed of a mixture of ice and water, which leads to an unclear spectral signature. Single and bi-spectral threshold methods are sometimes inappropriate due to a large variability of surface emissivity and cloud conditions. The objective of this study is to demonstrate the crucial role played by surface emissivity in the detection of polar winter clouds and the potential improvement offered by infrared hyperspectral observations, such as from the Infrared Atmospheric Sounding Interferometer (IASI). In this paper a new approach for cloud detection is proposed and validated exploiting active measurements from satellite sensors, i.e., the CloudSat cloud profiling radar (CPR) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). For a homogenous IASI field of view (FOVs), the proposed cloud detection scheme tallies with the combined CPR and CALIOP product in classifying 98.11% of the FOVs as cloudy and also classifies 97.54% of the FOVs as clear. The Hansen Kuipers discriminant reaches 0.95.

show abstract

“…With increasing optical depth, the depolarization signal received from liquid clouds increases gradually from 0 to values in the range of non-spherical ice particles (e.g. a depolarization ratio of 30% at an optical depth of around 3 was calculated for the geometry of the Cloud-Aerosol Lidar with Orthogonal Polarization, CALIOP, You et al, 2006). For liquid water clouds, the backscatter and the depolarization are positively correlated, while for ice clouds, the depolarization decreases with penetration into the cloud, as was observed for CALIPSO data (Hu et al, , 2007.…”

Section: Airborne Mobile Aerosol Lidarmentioning

confidence: 99%

Lidar characterization of the Arctic atmosphere during ASTAR 2007: four cases studies of boundary layer, mixed-phase and multi-layer clouds

et al. 2010

View full text Add to dashboard Cite

Abstract. During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR), which was conducted in Svalbard in March and April 2007, tropospheric Arctic clouds were observed with two ground-based backscatter lidar systems (micro pulse lidar and Raman lidar) and with an airborne elastic lidar. In the time period of the ASTAR 2007 campaign, an increase in low-level cloud cover (cloud tops below 2.5 km) from 51% to 65% was observed above Ny-Ålesund. Four different case studies of lidar cloud observations are analyzed: With the ground-based Raman lidar, a layer of spherical particles was observed at an altitude of 2 km after the dissolution of a cloud. The layer probably consisted of small hydrated aerosol (radius of 280 nm) with a high number concentration (around 300 cm −3 ) at low temperatures (−30 • C). Observations of a boundary layer mixedphase cloud by airborne lidar and concurrent airborne in situ and spectral solar radiation sensors revealed the localized process of total glaciation at the boundary of different air masses. In the free troposphere, a cloud composed of various ice layers with very different optical properties was detected by the Raman lidar, suggesting large differences of ice crystal size, shape and habit. Further, a mixed-phase double layer cloud was observed by airborne lidar in the free troposphere. Local orography influenced the evolution of this cloud. The four case studies revealed relations of cloud properties and specific atmospheric conditions, which we plan to use as the base for numerical simulations of these clouds.

show abstract

Sensitivity of depolarized lidar signals to cloud and aerosol particle properties

Cited by 39 publications

References 17 publications

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

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

The Role of Emissivity in the Detection of Arctic Night Clouds

Lidar characterization of the Arctic atmosphere during ASTAR 2007: four cases studies of boundary layer, mixed-phase and multi-layer clouds

Contact Info

Product

Resources

About