Global analysis of ice microphysics from CloudSat and CALIPSO: Incorporation of specular reflection in lidar signals

Abstract

[1] We developed a new radar-lidar algorithm that can be applied to CloudSat and CloudAerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data to retrieve ice microphysics. The algorithm analyzes the specular reflection of lidar signals often observed by CALIPSO with large backscattering coefficients and small depolarization ratios. Analyses of CloudSat and CALIPSO data by our former radar-lidar algorithm showed problems retrieving ice cloud microphysics when specular reflection was present. We implemented additional look-up tables for horizontally oriented plates. A specular reflection mode in the radar-lidar algorithm could drastically improve retrieval results. The new radar-lidar algorithm requires depolarization ratios measured by CALIPSO, in addition to the radar reflectivity factor and backscattering coefficient at 532 nm. We performed several sensitivity studies to retrieval results. Nonsphericity turned out to be the largest source of uncertainties. Global analyses of ice microphysics for CloudSat-CALIPSO overlap regions were performed. The effective radius decreased as the altitude increased. The effective radius in the specular reflection ranged from 100 to 300 mm. The ice water content (IWC) ranged from 10 −4 to several tenths of a gram per cubic meter. Both effective radius and IWC increased as the altitude (temperature) decreased (increased). The largest mixing ratio of oriented particles occurred between −20 and −5°C. The IWC had two maxima in the tropics above 15 km and around 5 km. We also examined the differences in ice microphysics over land and ocean. The effective radius was similar over land and ocean, but the IWC tended to be larger over land.

Depolarization Ratio of Clouds Measured by Multiple-Field of view Multiple Scattering Polarization Lidar

“…Analysis of the MFMSPL and the cloud radar would provide a unique opportunity to develop and evaluate the performance of the system. And it is also expected that the system can help to develop the retrieval algorithm for water microphysics using CALIPSO and CloudSat data as previously conducted for the ice microphysics [8]. The JAXA-ESA mission EarthCARE was scheduled to be launched in 2018 and the EarthCARE will carry high spectral resolution lidar at 355nm and 94GHz Doppler cloud radar.…”

Development of multiple scattering polarization lidar to observe depolarization ratio of optically thick low level clouds

“…Besides, the beam area was much smaller for the MFMSPL than that for the CALIPSO and the impact of the difference will be investigated. It is also planned to use the data by the MFMSPL and synergy observations with the cloud radar to develop and evaluate retrieval algorithms for water clouds for CALIPSO and CloudSat in a similar manner as that for ice clouds [8] [9]. The JAXA-ESA joint mission EarthCARE was scheduled to be launched in 2016 and it will carry a high spectral resolution lidar at 355nm and 94GHz Doppler cloud radar [10].…”

Development of level 2 algorithms for EarthCARE CPR/ATLID

“…The retrieved properties are effective radius, ice water content, and liquid water content. We can apply the radar-lidar algorithms for the CPR-ATLID overlapping region as performed for CloudSat and CALIPSO data [4] and by using the solutions for the region, it is also possible to derive the cloud microphysics for CPR or ATLID only regions on the basis of Levenberg-Marquardt algorithm as demonstrated in [5].…”

“…Some of the algorithms have been developed and applied to the CloudSat and CALIPSO [2,3,4,5] and global distribution of the cloud products have been obtained for more than six years. All cloud products have horizontal and vertical resolutions of 1km and 100m, respectively.…”