Improved retrievals of the optical properties of cirrus clouds by a combination of lidar methods

Cadet, Bertrand; Giraud, Vincent; Haeffelin, Martial; Keckhut, Philippe; Réchou, Anne; Baldy, S.

doi:10.1364/ao.44.001726

Cited by 45 publications

(39 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Even when using polarization and several wavelengths, retrieving optical and microphysical parameters from lidar requires making many assumptions about the particle type, shape and size within the cloud. In addition, this retrieval requires very accurate signals, that for a given lidar (Cadet et al, 2005) are not possible when clouds are too thin (too weak differential signals) or too deep (too large lidar signal attenuation above cloud). In our case, even if we should theoretically be able to retrieve the extinction and thus, the optical thickness directly from the Raman channel, the Nitrogen backscatter signal is often too noisy for an accurate retrieval.…”

Section: Ohp Ground-based Lidarmentioning

confidence: 99%

“…Therefore, it is essential to identify and document these different parameters at different geographical locations to improve the parameterisation in numerical models and decrease uncertainties in climate prediction. Lidars designed to monitor cirrus clouds have been deployed at several observatories around the globe for more than a decade, producing regional climatologies from midlatitude (Goldfarb et al, 2001;Giannakaki et al, 2007) and tropical observatories (Comstock et al, 2002;Cadet et al, 2003;Thorsen et al, 2011). Lidar instruments can detect cirrus clouds with optical depths as low as 10 −3 at visible wavelengths, whereas many passive satellite sensors require visible optical depths of ∼ 0.1 for cirrus to be detected and, consequently, may underestimate the actual cirrus occurrence frequency.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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

show abstract

Section: Ohp Ground-based Lidarmentioning

confidence: 99%

Section: Introductionmentioning

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

View full text Add to dashboard Cite

show abstract

“…LR depends on several characteristics of the particles, including their shape, size distribution and refractive index (Ansmann et al, 1992;Ackermann, 1998;Ansmann, 2002;Chen et al, 2002;Barnaba and Gobbi, 2004;Cadet et al, 2005;Josset et al, 2012). Therefore, LR can provide indications about the ice-crystal characteristics (Sassen et al, 1989;Ansmann, 2002;Petty et al, 2006).…”

Section: E G Larroza Et Al: Towards An Automatic Lidar Cirrus Cloumentioning

confidence: 99%

“…From the signal attenuation, one can derived the LR (Chen et al, 2002). However, depending on the signal quality and cloud optical depth amplitude, this parameter can be obtained with reasonable accuracy (typically 10-20 %) or with worthless large uncertainty in the case of both of thin or thick clouds (Cadet et al, 2005). Here a methodology is proposed to derive the LR parameter when the conditions are favorable for including multilayer events.…”

Section: E G Larroza Et Al: Towards An Automatic Lidar Cirrus Cloumentioning

confidence: 99%

Towards an automatic lidar cirrus cloud retrieval for climate studies

et al. 2013

View full text Add to dashboard Cite

Abstract. This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinctionto-backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology.

show abstract

“…SIRTA gathers active and passive remote sensing instruments to retrieve optical, radiative and dynamic properties of the atmosphere and its constituents. This includes a dual wavelength polarisation lidar LNA Lidar for Lidar Nuages Aérosols, that is Cloud Aerosol Lidar), a millimetre wave Doppler radar, a near-IR ceilometer, a surface broadband flux station, and standard weather measurements (Haeffelin et al, 2005). The SIRTA database includes also radiosonde profile data produced by Météo-France 15 km from the site as part of their national operational network (00 and 12 UT).…”

Section: Data Descriptionmentioning

confidence: 99%

STRAT: An Automated Algorithm to Retrieve the Vertical Structure of the Atmosphere from Single-Channel Lidar Data

Morille

Haeffelin

Drobinski

et al. 2007

Journal of Atmospheric and Oceanic Technology

194

View full text Add to dashboard Cite

Today several lidar networks around the world provide large datasets that are extremely valuable for aerosol and cloud research. Retrieval of atmospheric constituent properties from lidar profiles requires detailed analysis of spatial and temporal variations of the signal. This paper presents an algorithm called Structure of the Atmosphere (STRAT), which is designed to retrieve the vertical distribution of cloud and aerosol layers in the boundary layer and through the free troposphere and to identify near-particle-free regions of the vertical profile and the range at which the lidar signal becomes too attenuated for exploitation, from a single lidar channel. The paper describes each detection method used in the STRAT algorithm and its application to a tropospheric backscatter lidar operated at the SIRTA observatory, in Palaiseau, 20 km south of Paris, France. STRAT retrievals are compared to other means of layer detection and classification; retrieval performances and uncertainties are discussed

show abstract

Improved retrievals of the optical properties of cirrus clouds by a combination of lidar methods

Cited by 45 publications

References 29 publications

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

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

Towards an automatic lidar cirrus cloud retrieval for climate studies

STRAT: An Automated Algorithm to Retrieve the Vertical Structure of the Atmosphere from Single-Channel Lidar Data

Contact Info

Product

Resources

About