This site contains browse images of the total 532 nm attenuated backscatter signal (the sum of the 532 nm parallel and perpendicular return signals), the perpendicular 532 nm attenuated backscatter signal, and the total 1064 nm attenuated backscatter signal from CALIOP, the CALIPSO lidar. All images shown were acquired during both the daytime and nighttime portions of orbits.
The signal strength has been color coded such that blues correspond to molecular scattering and weak aerosol scattering, aerosols generally show up as yellow/red/orange. Stronger cloud signals are plotted in gray scales, while weaker cloud returns are similar in strength to strong aerosol returns and coded in yellows and reds.
Preliminary calibrations applied to the pre-release 1.10 versions of the data produced occasional artifacts due to high energy particles trapped in the Earth's magnetic field hitting the CALIOP detectors. These calibration artifacts are sometimes apparent in the browse images as discontinuities where colors suddenly become darker. The calibration technique applied in release version 1.10 and subsequent data releases significantly improves this problem.
The CALIOP 532 nm channels do not recover instantaneously from very strong returns such as those from ocean and land surfaces. Instead, there is a decay which is approximately exponential.
Due to this effect, there is often apparent lidar return from beneath the surface. This effect is particularly noticeable in Antarctica where frequent cloud-free atmospheres and a highly reflective surface result in surface signals which apparently extend significantly below the true surface.
When the atmosphere is not clear, varying atmospheric attenuation will modulate the strength of the surface return and the magnitude of the transient recovery. Return signals from very strongly scattering clouds can also produce this effect, although it is not always apparent.
