AN INTEGRATED MODELING AND OBSERVATIONAL STUDY IS PROPOSED TO EXPLORE HORIZONTAL CLOUD STRUCTURE AND 3D RADIATIVE EFFECTS AND THEIR IMPACT ON PASSIVE REMOTE SENSING RETRIEVALS OF CLOUD PROPERTIES. THE MODELING COMPONENT OF THIS STUDY WILL BE BASED ON A CLOUD RETRIEVAL SIMULATOR OUR GROUP DEVELOPED WITH THE NASA GISS LES CLOUD MODEL DHARMA AND A SUITE OF RADIATIVE TRANSFER MODELS. THE OBSERVATIONAL STUDY WILL UTILIZE DATA FROM THE MODIS AIRBORNE SIMULATOR (MAS) AND THE RESEARCH SCANNING POLARIMETER (RSP) OBTAINED DURING VARIOUS NASA SUB-ORBITAL FIELD CAMPAIGNS. THE COMBINATION OF LES-SATELLITE SIMULATOR AND FIELD CAMPAIGN DATA WILL ALLOW US TO INVESTIGATE THE FOLLOWING QUESTIONS: 1) HOW DO CLOUD HORIZONTAL STRUCTURES AND 3D RADIATIVE TRANSFER EFFECTS IMPACT SPECTRAL/POLARIMETRIC METHODS? 2) HOW DO THESE IMPACTS VARY WITH SATELLITE RETRIEVAL RESOLUTION? 3) HOW DO 3D RADIATIVE TRANSFER EFFECTS INFLUENCE THE STATISTICS OF RETRIEVED CLOUD PROPERTIES AT THE SCALES RELEVANT TO GCM AND AEROSOL INDIRECT EFFECT STUDIES? THE MODELING STUDY WHICH IS IDEAL FOR STUDYING PROCESS-LEVEL PHYSICAL EFFECTS WILL HELP TO INFORM THE OBSERVATIONAL STUDIES THAT FOLLOW. A SCALE-BY-SCALE ANALYSIS OF RETRIEVALS AT VARIOUS RESOLUTIONS WILL ALLOW FOR THE EXPLORATION OF RESOLUTION EFFECTS STEMMING FROM UNRESOLVED CLOUD FEATURES. THIS ANALYSIS OF MBL CLOUD RETRIEVALS WILL HELP US UNDERSTAND THE RETRIEVAL DIFFERENCES BETWEEN INSTRUMENTS WITH DIFFERENT SPATIAL RESOLUTIONS FOR EXAMPLE MODIS 1KM VS. NPP VIIRS 375M. IN ADDITION THE PROPOSED COMPARISON BETWEEN SPECTRALAND POLARIMETRIC-BASED CLOUD PROPERTY RETRIEVALS WILL REVEAL THE SENSITIVITY OF THE TWO METHODS TO CLOUD HORIZONTAL STRUCTURES AND 3- D EFFECTS. CLOUD RETRIEVALS INFORM OUR INTERPRETATION AND PRESCRIPTION OF CLOUDS IN CLIMATE MODELING AND PHYSICAL STUDIES SO BIASES INHERENT IN THE RETRIEVAL HAVE THE POTENTIAL TO EFFECT OTHER STUDIES. THIS RESEARCH IS DIRECTLY RELATED TO ONE OF THE NESSF FOCUS AREAS WATER AND THE ENERGY CYCLE AND ADDRESSES THE NEED FOR A GREATER UNDERSTANDING OF CLOUDS IN A CHANGING CLIMATE. THE PROPOSED RESEARCH WILL CONSTITUTE THE MAJOR EFFORT AND FOCUS OF THE AUTHOR S PH.D. DISSERTATION OVER THE NEXT THREE YEARS.