Abstract
We developed a multiple-filed-of view multiple-scattering polarization lidar (MFMSPL) at 355nm to study microphysics of optically thick clouds and understand multiple scattering effects on space lidar measurements (e.g., EarthCARE). This system is based on depolarization Mie lidar technique; it uses a compact receiver module including a small telescope, polarizer, and detectors to measure co-polar and cross-polar backscatter signals, separately. The MFMSPL system has all the 10 measurement channels. The MFMSPL uses the five receiver modules with FOV of 10mrad tilted with different zenith angles (θ); it measures on-beam signals (θ=0mrad) as well as four off-beam signals (θ=10,20,30,40mrad). This MFMSPL system was based on previously developed 532nm MFMSPL system, however, we made the system more stable, robust, and compact by integrating co-polar and cross-polar channels in the receiver module than the previous system. In addition, we improved the dynamic range of the measurement in nighttime by synergy use of analog and photon counting measurements. In the conference, we present the MFMSPL system, data analysis method including calibration method, and observation results.
Highlights
Lidar cannot penetrate optically thick clouds due to strong attenuation; it generally detects only the bottom of the layer [1]
CALIBRATION The receiver modules are tilted with different zenith angles in usual observation to measure on-beam signals and off-beam signals (Fig. 1), to calibrate the 10 channels of the multiple-filed-of view multiplescattering polarization lidar (MFMSPL) relatively, we make all the five receiver modules upward in the vertical direction (i.e., =0mrad) and set a polarization sheet on each receiver module rotating in angle of 45 to the direction of the linear polarization of the laser as conducted in calibration of depolarization Mie lidars [7]
The on-beam channels indicate that cloud layers appeared from 4km to 8km on the day and it rained from 19UTC to 20UTC
Summary
Lidar cannot penetrate optically thick clouds (or aerosols) due to strong attenuation; it generally detects only the bottom of the layer [1]. To obtain more information in the inner part of cloud layer and overcome the limitations of conventional ground-based lidars, we developed a multiple-filed-of view multiple-scattering polarization lidar (MFMSPL) at 532nm that can detect backscatter coefficients and depolarization ratios as similar as those observed by CALIOP [5]. This system was constructed by combining four channels with different zenith angles, such that each receiver channel has a 10mrad FOV and a polarization function. This paper describes the developed MFMSPL system (Section2), calibration method (Section3), observation results (Section 4), and summary (section 5)
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