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

Optical and geometrical characteristics of cir- rus 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 tempera- tures in the range from 65 to 38 C. The cloud thickness generally ranges from 1 to 5 km and 38% of the cases stud- ied have thickness between 2 and 3 km. The retrieval of op- tical depth and lidar ratio of cirrus clouds is performed using three different methods, taking into account multiple scatter- ing 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 re- sults obtained between the three methods shows good agree- ment. The multiple scattering errors of the measured effec- tive extinction coefficients range from 20 to 60%, depending on cloud optical depth. The temperature and thickness de- pendencies 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 be- tween optical depth and thickness was also found. However, no clear dependence of the lidar ratio values on the cloud temperature and thickness was found.

[1]  G. Tselioudis,et al.  Evidence of impact of aviation on cirrus cloud formation , 2003 .

[2]  P. Flamant,et al.  Iterative method to determine an averaged backscatter-to-extinction ratio in cirrus clouds. , 1996, Applied optics.

[3]  J. Comstock,et al.  Ground‐based lidar and radar remote sensing of tropical cirrus clouds at Nauru Island: Cloud statistics and radiative impacts , 2002 .

[4]  C. M. R. Platt.  Lidar Backscatter from Horizontal Ice Crystal Plates , 1978 .

[5]  Q. Fu,et al.  Parameterization of the Radiative Properties of Cirrus Clouds , 1993 .

[6]  Gerald G. Mace,et al.  The Composite Characteristics of Cirrus Clouds: Bulk Properties Revealed by One Year of Continuous Cloud Radar Data , 2001 .

[7]  Andrew J. Heymsfield,et al.  A parameterization of the particle size spectrum of ice clouds in terms of the ambient temperature and the ice water content , 1984 .

[8]  F. G. Fernald.  Analysis of atmospheric lidar observations: some comments. , 1984, Applied optics.

[9]  R. Velotta,et al.  An algorithm to determine cirrus properties from analysis of multiple-scattering influence on lidar signals , 2004 .

[10]  David M. Winker,et al.  The Experimental Cloud Lidar Pilot Study (ECLIPS) for cloud-radiation research , 1994 .

[11]  Oded Ben-Dov,et al.  Application of the Lidar to Air Pollution Measurements , 1967 .

[12]  A. Ansmann,et al.  Aerosol lidar intercomparison in the framework of the EARLINET project. 2. Aerosol backscatter algorithms. , 2004, Applied optics.

[13]  C. Platt,et al.  Lidar and Radiometric Observations of Cirrus Clouds , 1973 .

[14]  Optical and geometrical properties of northern midlatitude cirrus clouds observed with a UV Raman lidar , 1999 .

[15]  V. Freudenthaler,et al.  Aerosol lidar intercomparison in the framework of the EARLINET project. 1. Instruments. , 2004, Applied optics.

[16]  P. Davis.  The analysis of lidar signatures of cirrus clouds. , 1969, Applied optics.

[17]  J. Nee,et al.  Lidar ratio and depolarization ratio for cirrus clouds. , 2002, Applied optics.

[18]  C. Zerefos,et al.  Raman lidar and sunphotometric measurements of aerosol optical properties over Thessaloniki, Greece during a biomass burning episode , 2003 .

[19]  R. Hogan,et al.  Fast approximate calculation of multiply scattered lidar returns. , 2006, Applied optics.

[20]  P. Keckhut,et al.  A sub‐tropical cirrus clouds climatology from Reunion Island (21°S, 55°E) lidar data set , 2003 .

[21]  Harshvardhan,et al.  Temperature dependence of cirrus extinction - Implications for climate feedback , 1988 .

[22]  A. Ansmann,et al.  Aerosol lidar intercomparison in the framework of the EARLINET project. 3. Raman lidar algorithm for aerosol extinction, backscatter, and lidar ratio. , 2004, Applied optics.

[23]  Henning Rodhe,et al.  Atmospheric chemistry: Clouds and climate , 1999, Nature.

[24]  Christos Zerefos,et al.  Four‐year aerosol observations with a Raman lidar at Thessaloniki, Greece, in the framework of European Aerosol Research Lidar Network (EARLINET) , 2005 .

[25]  K. Sassen,et al.  Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part II: Midlatitude Cirrus Microphysical and Radiative Properties , 2002 .

[26]  J. Comstock,et al.  A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part III: Radiative Properties , 2001 .

[27]  William Viezee,et al.  Lidar Observations of Airfield Approach Conditions:An Exploratory Study , 1969 .

[28]  A. Ansmann,et al.  Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar. , 1992, Applied optics.

[29]  E. Eloranta.  Practical model for the calculation of multiply scattered lidar returns. , 1993, Applied optics.

[30]  U. Wandinger,et al.  Multiple-Scattering Influence on Extinction-and Backscatter-Coefficient Measurements with Raman and High-Spectral-Resolution Lidars. , 1998, Applied optics.

[31]  K. Sassen,et al.  A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part I: Macrophysical and Synoptic Properties , 2001 .

[32]  D. F. Young,et al.  A study of the vertical structure of tropical (20°S–20°N) optically thin clouds from SAGE II observations , 1998 .

[33]  S. Solomon.  The Physical Science Basis : Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

[34]  V. Freudenthaler,et al.  Aerosol lidar intercomparison in the framework of the EARLINET project. 1. Instruments. , 2004 .

[35]  Lidar network observations of cirrus morphological and scattering properties during the International Cirrus Experiment 1989 : the 18 October 1989 case study and statistical analysis , 1993 .

[36]  Benjamin M. Herman,et al.  Determination of aerosol height distributions by lidar , 1972 .

[37]  S. Young,et al.  Analysis of lidar backscatter profiles in optically thin clouds. , 1995, Applied optics.

[38]  Albert Ansmann,et al.  Cirrus optical properties observed with lidar, radiosonde, and satellite over the tropical Indian Ocean during the aerosol‐polluted northeast and clean maritime southwest monsoon , 2007 .

[39]  Alain Hauchecorne,et al.  Cirrus climatological results from lidar measurements at OHP (44°N, 6°E) , 2001 .

[40]  M. McCormick,et al.  A 6‐year climatology of cloud occurrence frequency from Stratospheric Aerosol and Gas Experiment II observations (1985–1990) , 1996 .

[41]  C. Platt,et al.  Remote Sounding of High Clouds: I. Calculation of Visible and Infrared Optical Properties from Lidar and Radiometer Measurements , 1979 .

[42]  Kenneth Sassen,et al.  Subvisual-Thin Cirrus Lidar Dataset for Satellite Verification and Climatological Research , 1992 .

[43]  K. Parameswaran,et al.  Temperature dependence of tropical cirrus properties and radiative effects , 2005 .

[44]  A. C. Dilley,et al.  Remote Sounding of High Clouds. Part VI: Optical Properties of Midlatitude and Tropical Cirrus , 1987 .

[45]  J. Klett.  Stable analytical inversion solution for processing lidar returns. , 1981, Applied optics.

[46]  Peter J. Webster,et al.  Clouds and Climate: Sensitivity of Simple Systems. , 1981 .

[47]  E. Eloranta,et al.  The 27-28 October 1986 FIRE IFO cirrus case study : cloud optical properties determined by high spectral resolution lidar , 1990 .