The Cloud Physics Lidar, or CPL, is a airborne backscatter lidar designed to operate simultaneously at three wavelengths: 1064, 532, and 355 nm. The CPL flies on high-altitude research aircraft, such as the ER-2 or WB-57. The purpose of the CPL is to provide multiwavelength measurements of cirrus, subvisual cirrus, and aerosols with high temporal and spatial resolution. The CPL utilizes state-of-art technology with a high repetition rate, low pulse energy laser and photon-counting detection. Vertical resolution of the CPL measurements is fixed at 30 m; horizontal resolution can vary but is typically about 200 m. From a fundamental measurement of 180-degree volume backscatter coefficients, various data products are derived, including time-height cross-section images; cloud and aerosol layer boundaries; optical depth for clouds, aerosol, and planetary boundary layer; and extinction profiles.