Cloud Detection Efficiencies of Radar, Lidar, and Stereo Cameras at the ARM SGP Site

 

Author

David Romps — Lawrence Berkeley National Laboratory

Category

Warm low clouds, including aerosol interactions

Description

The ARM Cloud Digital Cameras (ACDC) are a pair of cameras located at the Central Facility that perform stereo reconstruction of clouds. Three months of these reconstructions are available as the Point Cloud of Cloud Points Product in the ARM archive. Here, we use these data to compare the height- and time-resolved cloud detections by the stereo cameras, Raman lidar, and scanning W-band cloud radar. To accommodate its soda-straw view, the lidar is assumed to have detected a cloud at height z and time t if it reports any cloud at height z within plus or minus 15 minutes of time t. For shallow clouds (below 5 km), the stereo cameras detect nearly all of the clouds that the lidar detects, but half of the shallow clouds detected by the stereo cameras are not detected by the lidar. The tables are turned in the upper troposphere (above 10 km), where stereo reconstruction struggles to find feature points on smooth and wispy cirrus. The comparison with W-band cloud radar is more anecdotal because the radar was only operational for 5 days during the three-month study period. Nevertheless, on days when there were shallow cumuli, the stereo cameras were able to see them, but the radar was not.