scispace - formally typeset
Search or ask a question
Proceedings ArticleDOI

Measurements of long range transport using two wavelength and polarization lidar over tropical rural site Gadanki (13.45° N, 79.17° E)

05 May 2016-Vol. 9879, pp 11
TL;DR: In this paper, a lidar system was used to profile the boundary layer at 1064 and 532 nm wavelengths, which are fundamental and second harmonic components of Nd:YAG laser.
Abstract: This paper describes the measurements carried out on shape and size information of boundary layer aerosol particles using a lidar system developed at NARL, Gadanki. The lidar system profiles the boundary layer at 1064 and 532 nm wavelengths, which are fundamental and second harmonic components of Nd:YAG laser. However, the polarization measurements are conducted at 532 nm only. Using an external dichroic mirror in the laser path, the Nd:YAG laser output is separated into its harmonics. The fundamental harmonic of Nd:YAG laser is steered into atmosphere using a hard coated mirror and the atmospheric returns at 1064 and 532 nm are collected using two independent telescopes. The laser backscatter corresponding to 1064 nm is detected using an Avalanche photodiode; whereas the co and cross polarized signals returns corresponding to 532 nm laser are detected using a set of mini-PMT units. A three channel transient recorder unit is employed for recording the signals utilizing the analog and photon counting electronics. The lidar system is possible to operate in daylight period and can provide information on scattering properties of boundary layer aerosols. In the present study, measurements during long range transport events were performed at NARL, Gadanki during the year 2012. We proposed to present two case studies on long range transport that occurred during the year 2012. We present the results in terms of aerosol backscattering coefficient, depolarization ratio and color ratio with support of back trajectory analysis.
Citations
More filters
Journal ArticleDOI
TL;DR: In this article, the Levinson recursion algorithm-based Wiener filter over an original lidar signal was proposed to convert an analog signal to virtual count. And the proposed algorithm can be applied to any ground-based lidar system for an accurate profiling of the lower atmospheric compositions.
Abstract: The ground-based lidar is an active remote sensing instrument to profile the lower atmosphere effectively. In general, a lidar receives an analog signal from a lower altitude, a photon count from a higher altitude, and glues them in order to profile the atmosphere effectively. We propose the Levinson recursion algorithm-based Wiener filter over an original lidar signal to convert an analog signal to virtual count. This count is further glued with photon counting through mean square error method, and the results are compared with the linear regression algorithm. It is found that the proposed algorithm enhances the scaled analog from 152 to 8780 MHz in 355 nm, 131 to 3591 MHz in 387 nm, and 79 to 2956 MHz in 408 nm wavelengths. Furthermore, the improvement in correlation coefficients is found to be 0.9899, 0.9942, and 0.9807 for 355, 387, and 408 nm wavelengths, respectively. The proposed algorithm can be applied to any ground-based lidar system for an accurate profiling of the lower atmospheric compositions.

1 citations

References
More filters
Journal ArticleDOI
TL;DR: A restatement of the more general solution of Fernald et al.l which is also applicable to mildly turbid atmospheres where both aerosol and molecular scatterers must be considered in the analysis.
Abstract: There have been many discussions of solutions to the lidar equation for elastic scattering (e.g., Fernald et al.,' Klett, 2 Davis, and Collis and Russell ). Most of these are simply variations on Hitschfeld and Bordan's5 solution for meteorological radars. Klett 2 recently restated this solution in a very convenient form for the analysis of lidar observations collected in very turbid atmospheres. His paper has prompted a restatement of the more general solution of Fernald et al.l which is also applicable to mildly turbid atmospheres where both aerosol and molecular scatterers must be considered in the analysis. This has led to a simple numerical scheme for the computer analysis of lidar measurements. The lidar equation for two distinct classes of scatters (Fernald et al.') is

1,558 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provided an intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models and found that a roughly threefold variation in one measure of global climate sensitivity was found among the 19 models.
Abstract: The present study provides an intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models. This intercomparison uses sea surface temperature change as a surrogate for climate change. The interpretation of cloud-climate interactions is given special attention. A roughly threefold variation in one measure of global climate sensitivity is found among the 19 models. The important conclusion is that most of this variation is attributable to differences in the models' depiction of cloud feedback, a result that emphasizes the need for improvements in the treatment of clouds in these models if they are ultimately to be used as reliable climate predictors. It is further emphazied that cloud feedback is the consequence of all interacting physical and dynamical processes in a general circulation model. The result of these processes is to produce changes in temperature, moisture distribution, and clouds which are integrated into the radiative response termed cloud feedback.

863 citations

BookDOI
01 Jan 2005
TL;DR: In this article, the DIAL Revisited: BELINDA and White-Light Femtosecond Lidar is revisited: BelinDA and Raman Lidars.
Abstract: to Lidar.- Polarization in Lidar.- Lidar and Multiple Scattering.- Lidar and Atmospheric Aerosol Particles.- High Spectral Resolution Lidar.- Visibility and Cloud Lidar.- Differential-Absorption Lidar for Ozone and Industrial Emissions.- Differential-Absorption Lidar for Water Vapor and Temperature Profiling.- Raman Lidar.- Temperature Measurements with Lidar.- Resonance Scattering Lidar.- Doppler Wind Lidar.- Airborne and Spaceborne Lidar.- DIAL Revisited: BELINDA and White-Light Femtosecond Lidar.

681 citations

Journal ArticleDOI
TL;DR: In this paper, the light scattering and absorption programs of Cai and Liou (1982) and Takano and Jaweera (1985) are extended to include hexagonal ice crystals randomly and horizontally oriented in space.
Abstract: The light scattering and absorption programs of Cai and Liou (1982) and Takano and Jaweera (1985) are extended to include hexagonal ice crystals randomly and horizontally oriented in space. The scattering and polarization results for the ice crystals are calculated. The results are compared with measurement data. The single-scattering properties for horizontally oriented columns and plates are presented and used to explain halos and arcs observed in the atmopshere. In the second section, the theory and computations for multiple scattering in cirrus clouds containing oriented ice crystals are presented. The radiative transfer in clouds composed of horizontally oriented ice crystals is formulated. Also, reflected and transmitted intensities, planetary albedo, and polarization in multiple scattering by ice crystals are discussed.

543 citations

Journal ArticleDOI
TL;DR: A simple two-component theory considering two types of aerosol (dust and spherical aerosols) was developed and applied to the observed data and the mixing ratio of dust and the backscatter-related Angström exponents for dust andherical aerosols was derived.
Abstract: Lidar depolarization measurements were performed simultaneously at two wavelengths (532 and 1064 nm) in an Asian dust event. The observed particle depolarization ratio for 1064 nm was generally larger than that for 532 nm, and it was found that the mixing of Asian dust and other spherical aerosols must be taken into account. A simple two-component theory considering two types of aerosol (dust and spherical aerosols) was developed and applied to the observed data. The mixing ratio of dust and the backscatter-related Angstrom exponents for dust and spherical aerosols was derived. These parameters can be used to infer characteristics of the aerosols and the mixed states.

123 citations