Boundary layer structure & aerosol properties: lidar retrievals and in-situ measurements

Aerosols remain the dominant source of uncertainty in the global radiative budget. In order to reduce the uncertainty in the aerosol radiative forcing we require observations on both the global scale, from satellites, and the local scale. Satellite based observations provide much better coverage than in-situ measurements, but interpretation is difficult. Intercomparisons between remote sensing and in-situ measurements are required to develop and test retrieval algorithms. Here we present an overview of a study conducted at the Chilbolton cloud radar facility in the spring of 2008 to compare surface and balloon-borne measurements of boundary layer structure and aerosol properties with measurements from three different lidar systems, two of which are newly installed at the site: a Vaisala ceilometer, providing aerosol backscatter at 905 nm; a Halo Photonics lidar, providing backscatter and Doppler velocity at 1550 nm, and Leosphere lidar operating at 355 nm and providing aerosol and molecular backscatter and cross-polar return. A new balloon borne system measures mean temperature, pressure, humidity, 3D turbulent winds, and a 16-channel aerosol size spectrum in the range 0.05–3.5 micrometres (mean radius). The study will examine: the relationship between surface observations and those aloft; under what conditions the lidar can be used to infer the BL extinction coefficient; to what extent aerosol properties can be determined from the combined lidar measurements; and whether aerosol turbulent fluxes can be inferred from the lidar measurements. A secondary objective is the assessment of BL turbulent structure from the lidar data.