A Practical Application of Atmospheric Tomography with 3D Radiative Transfer to the Multi-angle Imaging SpectroRadiometer

The frequent and global measurement of cloud and aerosol optical and microphysical properties distributed within 3D space would be a revolutionary new class of observation useful for Large Eddy Simulation (LES) model validation and for the development of cloud microphysical parameterizations. Traditional techniques for measuring cloud properties, namely the bi-spectral technique, use 1D radiative transfer rather than 3D radiative transfer in the interpretation of radiances leading to biases that depend on cloud regime and sun-view geometry. Moreover, retrieved quantities such as cloud droplet effective radius lack information of the in-cloud vertical structure of microphysics, which is highly desired for advancements in cloud physics. Recent developments in Atmospheric Tomography with 3D Radiative Transfer (AT3D) eliminate the bias caused by using 1D radiative transfer and retrieves the highly desired 3D distribution of cloud and aerosol microphysical and optical properties through multi-view angle observations. Its success has been demonstrated in several idealized synthetic simulations and a case study of an isolated cumulus cloud over ocean observed by AirMSPI. We retrieve the 3D distribution of cloud volume extinction coefficient using AT3D and observations from the Multi Angle Imaging SpecroRadiometer (MISR) in a case study of broken cumulus over ocean within the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) domain. As part of the CAMP2Ex field campaign, in-situ measurements of the cloud drop size distribution were made at the same time and in a closely neighboring region. We leverage this dataset as a line of retrieval validation and find the retrieved cloud volume extinction coefficient field to agree well with in-situ observations. This work aims to pinpoint challenges that will arise in the practical application of the tomographic technique with the broader purpose of advancing the technique toward operational use on future satellite missions and providing a much sought after class of 3D cloud and aerosol optical and microphysical property measurements.