June 09, 2017 - ATTENTION: ONGOING
CALIOP is experiencing an elevated frequency of low energy laser shots within and
near the South Atlantic Anomaly (SAA) region which has degraded the science
quality of affected profiles since late May 2017. The frequency of low energy
laser shots will increase within the SAA and surrounding regions during the remainder
of lifetime of the current laser. Quality of level 2 data products is also degraded
within this region since they are derived from level 1B data. Low energy profiles
and level 2 data derived from them should not be used for scientific analyses.
Low energy laser shots are indicated by the "QC_Flag" SDS within the lidar
level 1B data product. The 5th bit of the QC_Flag should be queried to identify
CALIPSO LIDAR BROWSE IMAGES (PRODUCTION)
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.
IIR Level 2 images contained on the Version 4.10 browse image page are generated from either the Version 3.01, V3.02, or V3.30 lidar data. When a new version of the IIR Level 2 algorithm is completed using the Version 4.10 lidar data as input, these IIR browse images will be regenerated and reposted.
DATA RELEASE IMAGE AVAILABILITY
Version 3.01 - June 13, 2006 thru October 31, 2011 Version 3.02 - November 1, 2011 thru February 28, 2013 Version 3.30 - March 1, 2013 thru November 30, 2016 Version 3.40 - December 1, 2016 thru PRESENT Version 4.10 - June 13, 2006 thru PRESENT