Preliminary results of the Cloud-Aerosol Interaction Measurements (CLAIM) 2007 campaign on the Amazon Basin, Brazil

Clouds and precipitation play an important role on Earth's radiation budget, water and hydrological cycles, as well as energy cycles through latent heat release in the atmosphere. Under several aspects the interaction between aerosols and clouds is still a poorly understood process, and one reason for this is the lack of experimental observations to characterize the evolution of cloud microphysical structure. An instrumentation suite was put together to assess these issues. The Cloud Scanner is a scanning radiometer composed of 2 wavelengths in the near infrared (2.10 and 2.25 μm) used for the separation between ice and water, and 3 wavelengths in the thermal infrared (8, 11 and 12 μm) for the measurement of cloud brightness temperature, cirrus properties and water vapor correction. The Rainbow Camera is a multiangle imaging polarimeter with the wavelengths 0.47, 0.55, 0.66, 0.76, 0.87, and 0.91 μm, with 60 degrees FOV, used to retrieve droplet effective radii and distribution width. Both instruments were integrated onto a research aircraft for a field campaign over the Brazilian Amazon Basin from Sep-Oct 2007 under varying conditions of aerosol loading and cloud type, development stages, and cover area. The preliminary results obtained include real-time mappings of ice/water separation for clouds, with temperature profiles allowing for the retrieval of glaciation levels for a variety of cloud developmental stages and aerosol loadings, including deep convective cumulus clouds and/or high aerosol content. Vertical profiles of effective radius can be obtained using the measurements in 2.10 μm as entries in a look up table from a 3D radiative transfer model for the cloud field. The post-processed polarimeter measurements allow retrieving a polarized reflectance signal from which one can derive effective radii and distribution widths of droplets for clouds in the observed scenes. These results help understanding and quantifying the effects of cloud-aerosol interactions and their consequences for cloud microphysics.