A global view of horizontally oriented crystals in ice clouds from Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)

Noël, Vincent; Chepfer, Hélène

doi:10.1029/2009jd012365

Cited by 83 publications

(90 citation statements)

References 69 publications

(71 reference statements)

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“…4.1) shows the development of rather small ice crystals around 10 µm in radius in a volcanic ash environment. However, the are also observations were specular reflections occurs under colder conditions below −30 • C as reported by Noel and Chepfer (2010). Indeed, these observations are very rarely, but indicate that sedimentation of ice crystals can occur under cold conditions producing specular reflection when a zenith pointing lidar is used.…”

Section: Lidar Observationmentioning

confidence: 74%

Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption

Rolf

Krämer

Schiller³

et al. 2012

Atmos. Chem. Phys.

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Abstract. Heterogeneous ice formation induced by volcanic ash from the Eyjafjallajökull volcano eruption in April 2010is investigated based on the combination of a cirrus cloud observed with a backscatter lidar over Jülich (western Germany) and model simulations along backward trajectories. The microphysical properties of the cirrus cloud could only be represented by the microphysical model under the assumption of an enhanced number of efficient ice nuclei originating from the volcanic eruption. The ice nuclei (IN) concentration determined by lidar measurements directly before and after cirrus cloud occurrence implies a value of around 0.1 cm −3 (in comparison normal IN conditions: 0.01 cm −3 ). This leads to a cirrus cloud with rather small ice crystals having a mean radius of 12 µm and a modification of the ice particle number (0.08 cm −3 instead of 3 × 10 −4 cm −3 under normal IN conditions). The effectiveness of ice nuclei was estimated by the use of the microphysical model and the backward trajectories based on ECMWF data, establishing a freezing threshold of around 105 % relative humidity with respect to ice in a temperature range from −45 to −55 • C . Only with these highly efficient ice nuclei was it possible for the cirrus cloud to be formed in a slightly supersaturated environment.

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Section: Lidar Observationmentioning

confidence: 74%

Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption

Rolf

Krämer

Schiller³

et al. 2012

Atmos. Chem. Phys.

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“…This difference increases by the end of 2007 to reach 5 %. Although this difference is probably due to the sampling and the algorithm in use for each instrument, the tilt of laser emission that occurred for CALIOP at the end of 2007 (see, for example, Noel and Chepfer, 2010) could play a role in the slight decrease in cirrus clouds occurrence retrieved by CALIOP from this date. However, more investigations are needed to verify this.…”

Section: Occurrencementioning

confidence: 99%

A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N–5.7° E)

et al. 2013

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This study provides an analysis of cirrus cloud properties at midlatitude in the southern part of France from ground-based and spaceborne lidars. A climatology of cirrus cloud properties and their evolution over more than 12 yr is presented and compared to other mid-latitude climatological studies. Cirrus clouds occur ~37% of the total observation time and remain quasi-constant across seasons with a variation within ~5% around the mean occurrence. Similar results are obtained from CALIOP and the ground-based lidar, with a mean difference in occurrence of ~5% between both instruments. From the ground-based lidar data, a slight decrease in occurrence of ~3% per decade is observed but found statistically insignificant. Based on a clustering analysis of cirrus cloud parameters, three distinct classes have been identified and investigations concerning their origin are discussed. Properties of these different classes are analysed, showing that thin cirrus in the upper troposphere represent ~50% of cloud cover detected in summer and fall, decreasing by 15–20% for other seasons

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“…Still, publi-cations related to polarimetric propagation effects in deposited seasonal snow are rare despite the fact that a differential propagation speed in falling snow was already noticed in 1976 for weather radars (Hendry et al, 1976). Today, polarimetric upward-looking radars are used to characterize the orientation and anisotropy of falling snow particles or rain (e.g., Matrosov et al, 2005;Garrett et al, 2012;Xie et al, 2012;Hogan et al, 2012;Noel and Chepfer, 2010;Tyynelä and Chandrasekar, 2014).…”

Section: Radio and Microwave Remote Sensing Observations Of The Dielementioning

confidence: 99%

Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series

Leinß

Löwe²,

Proksch³

et al. 2016

The Cryosphere

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Abstract. The snow microstructure, i.e., the spatial distribution of ice and pores, generally shows an anisotropy which is driven by gravity and temperature gradients and commonly determined from stereology or computer tomography. This structural anisotropy induces anisotropic mechanical, thermal, and dielectric properties. We present a method based on radio-wave birefringence to determine the depth-averaged, dielectric anisotropy of seasonal snow with radar instruments from space, air, or ground. For known snow depth and density, the birefringence allows determination of the dielectric anisotropy by measuring the copolar phase difference (CPD) between linearly polarized microwaves propagating obliquely through the snowpack. The dielectric and structural anisotropy are linked by MaxwellGarnett-type mixing formulas. The anisotropy evolution of a natural snowpack in Northern Finland was observed over four winters (2009)(2010)(2011)(2012)(2013) with the ground-based radar instrument "SnowScat". The radar measurements indicate horizontal structures for fresh snow and vertical structures in old snow which is confirmed by computer tomographic in situ measurements. The temporal evolution of the CPD agreed in ground-based data compared to space-borne measurements from the satellite TerraSAR-X. The presented dataset provides a valuable basis for the development of new snow metamorphism models which include the anisotropy of the snow microstructure.

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A global view of horizontally oriented crystals in ice clouds from Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)

Cited by 83 publications

References 69 publications

Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption

Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption

A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N–5.7° E)

Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series

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