An algorithm to determine cirrus properties from analysis of multiple-scattering influence on lidar signals

Wang, X.; Boselli, Antonella; D'Avino, Loredana; Velotta, R.; Spinelli, N.; Bruscaglioni, P.; Ismaelli, Andrea; Zaccanti, Giovanni

doi:10.1007/s00340-005-1765-x

Cited by 20 publications

(20 citation statements)

References 22 publications

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“…Also, photons that are scattered at small forward angles are not lost from the lidar beam and may experience enhanced scattering (Young, 1995). Multiple scattering is significant in cirrus clouds and varies with cloud optical depth, cloud extinction and lidar penetration depth (Wang et al, 2005). As Wandinger (1998) showed, multiple-scattering errors of measured extinction coefficients are typically in the order of 50% at the bases of clouds and decrease with increasing penetration depth to below 20%.…”

Section: Multiple Scattering Effectmentioning

confidence: 99%

“…As Wandinger (1998) showed, multiple-scattering errors of measured extinction coefficients are typically in the order of 50% at the bases of clouds and decrease with increasing penetration depth to below 20%. Wang et al (2005) showed that the presence of multiple scattering can lead to an underestimation of the extinction coefficient by as large as 200%, whereas the backscattering coefficient is almost unaffected.…”

Section: Multiple Scattering Effectmentioning

confidence: 99%

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Optical and geometrical characteristics of cirrus clouds over a Southern European lidar station

Giannakaki¹,

Balis²,

Amiridis

et al. 2007

Atmos. Chem. Phys.

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Abstract. Optical and geometrical characteristics of cirrus clouds over Thessaloniki, Greece (40.6 • N, 22.9 • E) have been determined from the analysis of lidar and radiosonde measurements performed during the period from 2000 to 2006. Cirrus clouds are generally observed in a mid-altitude region ranging from 8.6 to 13 km, with mid-cloud temperatures in the range from −65 • to −38 • C. The cloud thickness generally ranges from 1 to 5 km and 38% of the cases studied have thickness between 2 and 3 km. The retrieval of optical depth and lidar ratio of cirrus clouds is performed using three different methods, taking into account multiple scattering effect. The mean optical depth is found to be 0.31±0.24 and the corresponding mean lidar ratio is 30±17 sr following the scheme of Klett-Fernald method. Sub-visual, thin and opaque cirrus clouds are observed at 3%, 57% and 40% of the measured cases, respectively. A comparison of the results obtained between the three methods shows good agreement. The multiple scattering errors of the measured effective extinction coefficients range from 20 to 60%, depending on cloud optical depth. The temperature and thickness dependencies on optical properties have also been studied in detail. A maximum mid-cloud depth of ∼3.5 km is found at temperatures around ∼−47.5 • C, while there is an indication that optical depth and mean extinction coefficient increases with increasing mid-cloud temperature. A correlation between optical depth and thickness was also found. However, no clear dependence of the lidar ratio values on the cloud temperature and thickness was found.

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Section: Multiple Scattering Effectmentioning

confidence: 99%

Section: Multiple Scattering Effectmentioning

confidence: 99%

Optical and geometrical characteristics of cirrus clouds over a Southern European lidar station

Giannakaki¹,

Balis²,

Amiridis

et al. 2007

Atmos. Chem. Phys.

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“…Therefore the cirrus cloud measurements by ground-based lidar typically suffer seriously from the effect of multiple scattering (MS) (Wandinger, 1998). As analysed also in Wang et al (2005), the backscatter coefficient as determined by the elastic/Raman method is not influenced by MS significantly. On the contrary, multiple scattering occurrence can lead to an underestimation of the extinction coefficient, and hence of the optical depth and lidar ratio, up to a factor of 2 .…”

Section: Cirrus Cloudsmentioning

confidence: 99%

“…An underestimation of the lidar ratio can lead to a misinterpretation of cirrus optical and microphysical properties. Therefore, before comparing optical depth and lidar ratio measured at the three lidar stations, a correction of the extinction profiles for multiple scattering has been performed following the iterative procedure described by Wang et al (2005), based on a Monte Carlo calculation of direct influence of MS on lidar signals (Bruscaglioni et al, 1995). The iterative method allows retrieval of the MS corrected extinction coefficients vertical profiles from experimental measurements of extinction and backscatter values, namely the effective values.…”

Section: Cirrus Cloudsmentioning

confidence: 99%

“…For lidar stations at CNR-IMAA and DIFA, we have chosen almost simultaneous observations (1830( -1900 in order to directly compare results obtained with experimental apparatus having different fields of view and then differently influenced by MS. As described in Wang et al (2005), the iterative procedure corrects the MS effect, but can also be used to get an estimate of the effective cirrus particle dimension and shape based on the comparison of the lidar ratio values and the phase function chosen in Monte Carlo simulation from a set of cirrus phase functions. For all three lidar stations, we considered in the iterative procedure ten different types (plate and column) and dimensions (from a few to hundreds of µm) of the ice crystal scatterers.…”

Section: Cirrus Cloudsmentioning

confidence: 99%

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Characterization of the variability of the humidity and cloud fields as observed from a cluster of ground-based lidar systems

Mona

Rosati

D’Amico

et al. 2007

Q.J.R. Meteorol. Soc.

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Three lidar stations located in Southern Italy were operational during the Italian phase of the EAQUATE campaign in September 2004. With this cluster of instruments, the characterization of water vapour and clouds distribution and evolution with high temporal and vertical resolution is possible. A cirrus cloud episode and the presence of an elevated humid layer in the free troposphere observed at all three stations are analysed in detail. Variability of both cirrus cloud and water vapour fields is studied on different spatial and temporal scales.

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A fast hybrid (3‐D/1‐D) model for thermal radiative transfer in cirrus via successive orders of scattering

et al. 2017

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We investigate the impact of cirrus cloud heterogeneity on the direct emission by cloud or surface and on the scattering by ice particles in the thermal infrared (TIR). Realistic 3‐D cirri are modeled with the 3DCLOUD code, and top‐of‐atmosphere radiances are simulated by the 3‐D Monte Carlo radiative transfer (RT) algorithm 3DMCPOL for two (8.65 μm and 12.05 μm) channels of the Imaging Infrared Radiometer on CALIPSO. At nadir, comparisons of 1‐D and 3‐D RT show that 3‐D radiances are larger than their 1‐D counterparts for direct emission but smaller for scattered radiation. For our cirrus cases, 99% of the 3‐D total radiance is computed by the third scattering order, which corresponds to 90% of the total computational effort, but larger optical thicknesses need more scattering orders. To radically accelerate the 3‐D RT computations (using only few percent of 3‐D RT time with a Monte Carlo code), even in the presence of large optical depths, we develop a hybrid model based on exact 3‐D direct emission, the first scattering order from 1‐D in each homogenized column, and an empirical adjustment linearly dependent on the optical thickness to account for higher scattering orders. Good agreement is found between the hybrid model and the exact 3‐D radiances for two very different cirrus models without changing the empirical parameters. We anticipate that a future deterministic implementation of the hybrid model will be fast enough to process multiangle thermal imagery in a practical tomographic reconstruction of 3‐D cirrus fields.

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An algorithm to determine cirrus properties from analysis of multiple-scattering influence on lidar signals

Cited by 20 publications

References 22 publications

Optical and geometrical characteristics of cirrus clouds over a Southern European lidar station

Optical and geometrical characteristics of cirrus clouds over a Southern European lidar station

Characterization of the variability of the humidity and cloud fields as observed from a cluster of ground-based lidar systems

A fast hybrid (3‐D/1‐D) model for thermal radiative transfer in cirrus via successive orders of scattering

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