Cloud optical, microphysical and macrophysical retrieval from synergy between POLDER3/Parasol and MODIS/Aqua : Preliminary results

Since March 2005, the PARASOL mission has been providing coincident data from POLDER3 (Polarization and Directionality of the Earth Reflectances) with MODIS (Moderate Resolution Imaging Spectroradiometer) on AQUA, making a major step forward achieving AQUA-Train experiment challenging objectives. Combination of these two instruments provides a unique opportunity to study clouds using high spatial resolution, multispectral, multidirectional and polarization measurements. Based on these data, possibilities and limitations of multi-sensor remote sensing are investigated and discussed.

Cross-calibration of the two instruments is being performed to allow for the fusion of data in a common set of algorithms. A new set of algorithms is being developed to retrieve (i) a comprehensive cloud thermodynamic phase index, (ii) cloud optical thickness from several bidirectional reflectances performed at 670 nm over land and 865 nm over ocean, (iii) particle effective radius from multi-angle polarization and near infrared measurements, and (iv) cloud top pressure from different techniques (v) and a qualitative multilayer cloud system index. MODIS high spatial resolution is also used to investigate the impact of sub pixel cloud heterogeneities on bidirectional reflectance field as measured by the POLDER instrument.

We will emphasis some limitation and strength of each instrument to explain when and how a synergistic approach can help in providing a better description of the cloudy atmosphere. Preliminary results obtained from our research semi-operational code developed for these studies will be presented and compared to existing operational level 2 products from MODIS and POLDER.