Hurricane Bill was also sampled by a third A-Train member instrument, the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), aboard the CALIPSO satellite, a joint mission between the United States and France. As a lidar instrument, CALIOP is an active sensor that measures total attenuated backscatter (similar to radar) and is designed with a sensitivity toward atmospheric aerosols and cloud ice particles. The CALIPSO satellite flies in line with CloudSat, therefore, their observations differ from a marginal separation in time. In the image below, CALIPSO samples along a track similar to CloudSat (see previous blog post), and obtains backscatter from the high altitude ice clouds (cirrus) at 15 km and above. CALIPSO is even better at detecting thin ice clouds than CloudSat, and in some cases may offer a better measure of cloud top height. Note that although CloudSat depicts the eye as being completely cloud free, CALIPSO measurements detect some returns almost completely across the width of the storm. Therefore, some “optically thin” cirrus may have been present in the vicinity of the CloudSat track or across the eye of Hurricane Bill that was only detected by CALIPSO.
For more information about the NASA A-Train and other NASA instruments applied to hurricane research, check out the following article: NASA’s A-Train of Satellites “On Track” With Hurricane Research. Quick look imagery from the CALIPSO satellite are provided by NASA Langley Research Center.