[A-CG36] 衛星による地球環境観測

[ACG36-P10] Improvement of cloud mask algorithm of CALIPSO lidar

*及川 栄治¹、岡本 創¹、佐藤 可織¹ (1.九州大学　応用力学研究所)

キーワード：CALIPSO、ライダー、雲

The cloud mask algorithm at 532 nm had been developed for the CALIPSO satellite lidar retrieval (Hagihara et al., 2010). In the cloud mask scheme, the threshold value of attenuated backscattering coefficient to discriminate between clouds and aerosols was set to the fixed value, 10^-5.25 m^-1sr^-1. Clouds near cloud base tend to be undetected in this cloud mask scheme, because attenuated backscattering coefficient affected by the attenuation of the upper cloud layers becomes lower than the threshold value of clouds and aerosols. Therefore, the threshold value between clouds and aerosols changes depending on cloud and molecule attenuation in the new cloud mask scheme. In this study, we use the CALIPSO level 1b product version 4.1 and the effects of the CALIPSO lidar receiver’s transient response on attenuated backscattering coefficient are corrected using the transient response function (Lu et al., 2014, 2020). In the new cloud mask scheme, clouds near cloud base are detected more frequently and the low-level cloud fraction increases.