Limits to Characterizing the Global 3D Aerosol Distribution Using Satellite Lidar

Signal-to-noise ratio is a primary concern of anyone designing or using observations from lidar systems but is especially challenging for satellite lidar systems. Moving at velocities of 7 km /sec limits the averaging which can be applied to profile data from satellite lidars and operating hundreds of kilometers above the atmosphere forces space-based lidars to operate at the limits of detection sensitivity. Several recent papers have examined the sensitivity limits of CALIOP, the resulting impacts on aerosol detection capabilities, and the ability to quantify aerosol radiative effects. The general conclusion is that future satellite lidars will require an improved capability to detect and retrieve aerosol if we are to make progress in characterizing aerosol impacts on climate. In this talk we explore the fundamental limits to aerosol detection due to both SNR and calibration in different regimes: day vs. night, PBL vs upper troposphere vs. stratosphere, etc. Then we examine these limits in the context of general categories of lidar instruments: large-pulse (CALIOP), small-pulse (CATS), and HSRL (ATLID) and identify likely paths to improvements relative to current CALIOP capabilities.