Improvement of MODIS aerosol retrievals near clouds

[1] The retrieval of aerosol properties near clouds from reflected sunlight is challenging. Sunlight reflected from clouds can effectively enhance the reflectance in nearby clear regions. Ignoring cloud 3-D radiative effects can lead to large biases in aerosol retrievals, risking an incorrect interpretation of satellite observations on aerosol-cloud interaction. Earlier, we developed a simple model to compute the cloud-induced clear-sky radiance enhancement that is due to radiative interaction between boundary layer clouds and the molecular layer above. This paper focuses on the application and implementation of the correction algorithm. This is the first time that this method is being applied to a full Moderate Resolution Imaging Spectroradiometer (MODIS) granule. The process of the correction includes converting Clouds and the Earth's Radiant Energy System broadband flux to visible narrowband flux, computing the clear-sky radiance enhancement, and retrieving aerosol properties. We find that the correction leads to smaller values in aerosol optical depth (AOD), Angstrom exponent, and the small mode aerosol fraction of the total AOD. It also makes the average aerosol particle size larger near clouds than far away from clouds, which is more realistic than the opposite behavior observed in operational retrievals. We discuss issues in the current correction method as well as our plans to validate the algorithm.

[1]  W. Paul Menzel,et al.  MODIS Cloud-Top Property Refinements for Collection 6 , 2012 .

[2]  E. Vermote,et al.  Operational remote sensing of tropospheric aerosol over land from EOS moderate resolution imaging spectroradiometer , 1997 .

[3]  Alexander Ignatov,et al.  Physical Basis, Premises, and Self-Consistency Checks of Aerosol Retrievals from TRMM VIRS , 2000 .

[4]  W. Paul Menzel,et al.  Remote sensing of cloud, aerosol, and water vapor properties from the moderate resolution imaging spectrometer (MODIS) , 1992, IEEE Trans. Geosci. Remote. Sens..

[5]  R. Davies,et al.  Comparison of MISR and CERES top‐of‐atmosphere albedo , 2006 .

[6]  Michael D. Obland,et al.  Aerosol and cloud interaction observed from high spectral resolution lidar data , 2008 .

[7]  K. Stamnes,et al.  Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media. , 1988, Applied optics.

[8]  Oleg Dubovik,et al.  Angstrom exponent and bimodal aerosol size distributions , 2006 .

[9]  Larry Di Girolamo,et al.  Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar , 2009 .

[10]  T. Eck,et al.  Bimodal size distribution influences on the variation of Angstrom derivatives in spectral and optical depth space , 2001 .

[11]  Roger Davies,et al.  Fusion of CERES, MISR, and MODIS measurements for top-of-atmosphere radiative flux validation , 2006 .

[12]  D. Diner,et al.  Linearization of a scalar matrix operator method radiative transfer model with respect to aerosol and surface properties , 2013 .

[13]  Robert F. Cahalan,et al.  A simple model for the cloud adjacency effect and the apparent bluing of aerosols near clouds , 2008 .

[14]  K. Stamnes,et al.  Radiative Transfer in the Atmosphere and Ocean , 1999 .

[15]  Yoram J. Kaufman,et al.  On the twilight zone between clouds and aerosols , 2007 .

[16]  Patrick Minnis,et al.  Diurnal Variability of Regional Cloud and Clear-Sky Radiative Parameters Derived from GOES Data. Part III: November 1978 Radiative Parameters , 1984 .

[17]  Norman G. Loeb,et al.  An Observational Study of the Relationship Between Cloud, Aerosol and Meteorology in Broken Low-Level Cloud Conditions , 2013 .

[18]  B. Barkstrom,et al.  Clouds and the Earth's Radiant Energy System (CERES): An Earth Observing System Experiment , 1996 .

[19]  Zhanqing Li,et al.  Separating real and apparent effects of cloud, humidity, and dynamics on aerosol optical thickness near cloud edges , 2010, Journal of Geophysical Research.

[20]  L. Remer,et al.  Case studies of aerosol remote sensing in the vicinity of clouds , 2009 .

[21]  Robert F. Cahalan,et al.  Importance of molecular Rayleigh scattering in the enhancement of clear sky reflectance in the vicinity of boundary layer cumulus clouds , 2008 .

[22]  David R. Doelling,et al.  Angular Distribution Models for Top-of-Atmosphere Radiative Flux Estimation from the Clouds and the Earth’s Radiant Energy System Instrument on the Terra Satellite. Part II: Validation , 2005 .

[23]  R. Charlson,et al.  On the climate forcing consequences of the albedo continuum between cloudy and clear air , 2007 .

[24]  J. Hansen,et al.  Light scattering in planetary atmospheres , 1974 .

[25]  E. Vermote,et al.  The MODIS Aerosol Algorithm, Products, and Validation , 2005 .

[26]  Alexander Marshak,et al.  Global CALIPSO Observations of Aerosol Changes Near Clouds , 2011, IEEE Geoscience and Remote Sensing Letters.

[27]  Sunny Sun-Mack,et al.  CERES Edition-2 Cloud Property Retrievals Using TRMM VIRS and Terra and Aqua MODIS Data—Part I: Algorithms , 2011, IEEE Transactions on Geoscience and Remote Sensing.

[28]  Steven Platnick,et al.  An initial analysis of the pixel-level uncertainties in global MODIS cloud optical thickness and effective particle size retrievals , 2004, SPIE Asia-Pacific Remote Sensing.

[29]  Evgueni I. Kassianov,et al.  On reflectance ratios and aerosol optical depth retrieval in the presence of cumulus clouds , 2008 .

[30]  Robert F. Cahalan,et al.  The albedo of fractal stratocumulus clouds , 1994 .

[31]  Zhanqing Li,et al.  Narrowband to Broadband Conversion with Spatially Autocorrelated Reflectance Measurements , 1992 .

[32]  Ana Maria Silva,et al.  Some considerations about Ångström exponent distributions , 2007 .

[33]  W. Paul Menzel,et al.  Cloud and aerosol properties, precipitable water, and profiles of temperature and water vapor from MODIS , 2003, IEEE Trans. Geosci. Remote. Sens..