FOR RETRIEVALS OF ICE CLOUD MICROPHYSICAL AND RADIATIVE PROPERTIES EACH SCIENCE TEAM ASSUMES A DIFFERENT ICE PARTICLE HABIT/SHAPE MODEL FOR GENERATING LOOK-UP TABLES THAT INVOLVE FORWARD LIGHT SCATTERING AND RADIATIVE TRANSFER COMPUTATIONS. FOR EXAMPLE THE CERES EDITION 4 ICE CLOUD PROPERTY RETRIEVAL ASSUMES A SINGLE HABIT MODEL (SPECIFICALLY HEXAGONAL ICE CRYSTALS WITH SURFACE ROUGHNESS) THE MODIS COLLECTION 6 ICE CLOUD PROPERTY RETRIEVAL ASSUMES ROUGHENED AGGREGATES AND THE AIRS SCIENCE TEAM ADOPTED THE MODIS COLLECTION 5 ICE MODEL (A MIXTURE OF VARIOUS ICE PARTICLE HABITS) IN THE INFRARED REGIME. HOWEVER LOEB ET AL. (2017) SHOWED THAT THE EFFECT OF AN ICE PARTICLE HABIT MODEL ON CLOUD RADIATIVE FORCING ASSESSMENT FROM SATELLITE-BASED CLOUD PROPERTY RETRIEVAL PRODUCTS IS MINIMIZED IF THE SAME ICE HABIT MODEL IS CONSISTENTLY USED FOR BOTH THE RETRIEVAL AND THE DOWNSTREAM BROADBAND RADIATIVE TRANSFER COMPUTATION. THIS FINDING PROMOTES A HYPOTHESIS (HEREAFTER THE CONSISTENCY HYPOTHESIS) THAT TO MINIMIZE ERRORS A CONSISTENT ICE CLOUD MODEL SHOULD BE USED FOR SATELLITE-BASED ICE CLOUD PROPERTY RETRIEVALS AND THE ASSESSMENT OF ICE CLOUD RADIATIVE FORCING. THIS HYPOTHESIS IF VALIDATED POSES A SIGNIFICANT CHALLENGE IN THAT AT PRESENT ICE CLOUD MODELS USED IN RADIATIVE TRANSFER MODELS (PARTICULARLY THOSE INVOLVED IN CLIMATE MODELS) ARE NOT CONSISTENT WITH THEIR COUNTERPARTS USED IN SATELLITE REMOTE SENSING. FOR THAT REASON USING SATELLITE RETRIEVAL PRODUCTS TO VALIDATE CLIMATE MODEL OUTPUT INCLUDING CLOUD RADIATIVE FORCING ASSESSMENT MAY INTRODUCE SIGNIFICANT UNCERTAINTIES. THE STUDY BY LOEB ET AL. (2017) WAS LIMITED BY USING ONLY 10 DAYS OF MODIS DATA AND THE ICE MODELS EMPLOYED BY THE CERES SCIENCE TEAM. THE PROJECT DESCRIBED IN THIS PROPOSAL BUILDS ON OUR PREVIOUS WORK AND WILL MORE THOROUGHLY VALIDATE THE CONSISTENCY HYPOTHESIS USING THE ICE CLOUD PROPERTY RETRIEVAL PRODUCTS DEVELOPED BY THE MODIS CERES AND AIRS SCIENCE TEAMS IN CONJUNCTION WITH RELEVANT ICE CLOUD MODELS. FOR ROBUST SIMULATIONS WE WILL USE THE LEVEL-2 RETRIEVAL PRODUCTS RATHER THAN THE GRIDDED PRODUCTS. ONLY THE MODIS AND AIRS PIXELS COLLOCATED WITH CALIPSO DATA WILL BE USED. THE CALIPSO MEASUREMENTS WILL BE USED TO CONSTRAIN CLOUD HEIGHT. THE MERRA REANALYSIS DATA WILL BE USED TO PROVIDE ATMOSPHERIC VERTICAL PROFILES. THE AFORESAID CLOUD PROPERTY RETRIEVAL PRODUCTS WILL BE USED AS INPUTS FOR RADIATIVE TRANSFER SIMULATIONS IN COMPARISON WITH THE CERES FLUX PRODUCTS. MOST IMPORTANTLY WE WILL DEVELOP ICE CLOUD PARAMETERIZATIONS FOR PREVAILING RADIATIVE TRANSFER MODELS (RTMS) INCLUDING RTMS USED IN TWO CLIMATE MODELS (SPECIFICALLY NCAR CESM AND NASA GISS MODELE2). THIS WILL MAKE IT POSSIBLE FOR RESEARCHERS TO USE NASAS CLOUD PROPERTY RETRIEVAL PRODUCTS WITHOUT PERPETUATING ERRORS STEMMING FROM USE OF MIS-MATCHED ICE CLOUD MODELS. THIS WILL BE ESPECIALLY BENEFICIAL IN STUDIES ASSESSING CLOUD RADIATIVE FORCING AND VALIDATING CLIMATE MODEL OUTPUT IN COMPARISON WITH SATELLITE OBSERVATIONS. IN PARTICULAR THESE ICE CLOUD PARAMETERIZATIONS WILL ALLOW USERS OF CLOUD PROPERTY RETRIEVAL PRODUCTS THE CAPABILITY OF SELECTING AN APPROPRIATE PARAMETERIZATION IN THE ASSESSMENT OF ICE CLOUD RADIATIVE FORCING. EXPECTED SIGNIFICANCE: THE OUTCOMES OF THIS PROJECT WILL: 1) IMPROVE THE ACCURACY OF THE ASSESSMENT OF ICE CLOUD RADIATIVE FORCING; AND 2) ADVANCE THE BEST USE OF NASAS CLOUD RETRIEVAL PRODUCTS. THIS WILL BE PARTICULARLY BENEFICIAL IN PROVIDING PARAMETERIZATION SCHEMES THAT ARE CONSISTENT WITH SPECIFIC CLOUD PROPERTY RETRIEVAL PRODUCTS FOR VARIOUS DOWNSTREAM APPLICATIONS INCLUDING CLOUD RADIATIVE FORCING ASSESSMENT AND VALIDATION OF CLIMATE MODEL PRODUCTS INVOLVING ICE CLOUDS.