The value of multiangle measurements for retrieving structurally and radiatively consistent properties of clouds, aerosols, and surfaces David J. Diner a, * , Bobby H. Braswell b , Roger Davies a , Nadine Gobron c , Jiannan Hu d , Yufang Jin e , Ralph A. Kahn a , Yuri Knyazikhin d , Norman Loeb f , Jan-Peter Muller g , Anne W. Nolin h , Bernard Pinty c , Crystal B. Schaaf d , Gabriela Seiz i , Julienne Stroeve j a Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States b University of New Hampshire, Durham, NH, United States c Joint Research Centre, Ispra, Italy d Boston University, Boston, MA, United States e University of California at Irvine, Irvine, CA, United States f NASA Langley Research Center, Hampton, VA, United States g University College London, London, UK h Oregon State University, Corvallis, OR, United States i Swiss Federal Institute of Technology (ETH), Zurich, Switzerland j University of Colorado, Boulder, CO, United States Received 6 November 2004; received in revised form 6 June 2005; accepted 13 June 2005 Abstract Passive optical multiangle observations make possible the retrieval of scene structural characteristics that cannot be obtained with, or require fewer underlying assumptions than, single-angle sensors. Retrievable quantities include aerosol amount over a wide variety of surfaces (including bright targets); aerosol microphysical properties such as particle shape; geometrically-derived cloud-top heights and 3-D cloud morphologies; distinctions between polar clouds and ice; and textural measures of sea ice, ice sheets, and vegetation. At the same time, multiangle data are necessary for accurate retrievals of radiative quantities such as surface and top-of-atmosphere albedos, whose magnitudes are governed by structural characteristics of the reflecting media and which involve angular integration over intrinsically anisotropic intensity fields. Measurements of directional radiation streams also provide independent checks on model assumptions conventionally used in satellite retrievals, such as the application of 1-D radiative transfer theory, and provide data required to constrain more sophisticated, 3-D approaches. In this paper, the value of multiangle remote sensing in establishing physical correspondence and self-consistency between scene structural and radiative characteristics is demonstrated using simultaneous observations from instruments aboard NASA’s Terra satellite (MISR, CERES, ASTER, and MODIS). Illustrations pertaining to the remote sensing of clouds, aerosols, ice, and vegetation properties are presented. D 2005 Elsevier Inc. All rights reserved. Keywords: Multiangle remote sensing; Terra; MISR; CERES; ASTER; MODIS 1. Introduction Solar radiation is the fundamental energy source for the Earth’s climate system and its web of life. Aerosols having a host of sizes, shapes, and atmospheric distributions absorb and scatter radiation over different surface types, resulting in a range of regional climate influences. Stratiform and cumuliform cloud fields with various spatial distributions of water and ice exist throughout the atmosphere’s vertical domain, cooling or heating the surface below. These surfaces in turn–smooth and crevassed, forested and arid, rural and urban–influence and are transformed by atmos- pheric, geodynamic, and biological processes. The complex- ity of the Earth system makes diagnosis and prediction of 0034-4257/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.rse.2005.06.006 * Corresponding author. E-mail address: David.J.Diner@jpl.nasa.gov (D.J. Diner). Remote Sensing of Environment 97 (2005) 495 – 518 www.elsevier.com/locate/rse