COMBINING HIGH SPECTRAL RESOLUTION LIDAR AND DUAL-FREQUENCY DOPPLER RADAR MEASUREMENTS WITH CONTEXTUAL BROAD-SWATH MULTI-SPECTRAL IMAGER OBSERVATIONS THE AEROSOL-CLOUD- ECOSYSTEMS (ACE) MISSION PRESENTS A UNIQUE OPPORTUNITY TO SIGNIFICANTLY ADVANCE OUR UNDERSTANDING OF THE COMPLETE SPECTRUM OF PROCESSES BY WHICH AEROSOLS CLOUDS AND PRECIPITATION INTERACT TO SHAPE THE EARTH S CLIMATE. AS ARTICULATED IN THE MOST RECENT ACE WHITE-PAPER SIGNIFICANTLY ADVANCING KNOWLEDGE OF THESE INTERACTIONS REQUIRES A NEW PARADIGM FOR INTERPRETING SATELLITE OBSERVATIONS THAT MORE DIRECTLY COUPLES CLOUD MICROPHYSICAL PROPERTIES AND THE UNDERLYING PROCESS RATES FROM WHICH THEY DERIVE. THIS NEED TO EXPLICITLY DOCUMENT THE SIGNATURES OF AEROSOL INFLUENCES ON LIQUID AND ICE PHASE MICROPHYSICAL PROCESSES PLACES STRINGENT REQUIREMENTS ON THE INFORMATION CONTENT OF THE ACE RADAR MEASUREMENTS TO ENSURE THEY PROVIDE SENSITIVITY TO ALL RELEVANT QUANTITIES ON THE SCALES OVER WHICH THESE PROCESSES VARY. THIS PROPOSAL WILL APPLY A COMBINATION OF SENSITIVITY STUDIES AND OBJECTIVE INFORMATION CONTENT METRICS TO GROUND-BASED AIRBORNE AND SIMULATED DOPPLER RADAR OBSERVATIONS TO LINK ACE DUAL-FREQUENCY DOPPLER RADAR REQUIREMENTS TO CORE MISSION OBJECTIVES. WE FOCUS ON THE ACE OBJECTIVES CENTERING ON QUANTIFYING AEROSOL IMPACTS ON CLOUD MICROPHYSICAL PROCESSES IN THE MID- AND HIGH-LATITUDES. THE SPECIFIC OBJECTIVES OF THE RESEARCH ARE TO:1.COMPLETE AN OBSERVATION-BASED DESCRIPTION OF THE RELEVANT INSTRUMENT SPECIFICATION TRADE-SPACE FOR THE ACE RADAR BY QUANTIFYING VERTICAL RESOLUTION REQUIREMENTS AND ESTABLISHING THE CORRESPONDING TRADE-OFFS WITH SENSITIVITY AND SPATIAL RESOLUTION;2.ANALYZE AIRBORNE MULTI-FREQUENCY RADAR OBSERVATIONS COLLECTED DURING THE RADAR DEFINITION EXPERIMENT (RADEX) TO VERIFY OBSERVATION-BASED TRADE-SPACE ASSESSMENTS AND EXPLORE NEW APPROACHES FOR RETRIEVING PROCESS RATES;3.UTILIZE A DATABASE OF SIMULATED 35 AND 94 GHZ REFLECTIVITIES AND DOPPLER SPECTRA FROM CLOUD RESOLVING MODEL (CRM) SIMULATIONS OF EXTRA-TROPICAL PRECIPITATION SCENES TO QUANTIFY THE INFORMATION CONTENT OF DIFFERENT ACE RADAR CONFIGURATIONS FOR SIMULTANEOUSLY QUANTIFYING CLOUD MICROPHYSICAL/MACROPHYSICAL PROPERTIES AND PROCESS RATES. PROVIDED BOTH ACE RADAR CHANNELS HAVE SUFFICIENT SENSITIVITY THE COMBINATION OF KA- AND WBAND REFLECTIVITIES PROVIDE THE MOST PRECISE MEASURE OF THE VERTICAL STRUCTURE OF RAIN DROP SIZES NEAR THE SURFACE AS WELL AS SNOW PARTICLE CONCENTRATIONS AND DENSITIES ALOFT. WITH SUFFICIENT ACCURACY ASSOCIATED DOPPLER VELOCITIES MAY ENHANCE OUR ABILITY TO DISCRIMINATE BETWEEN RAIN AND SNOW WHILE ALSO CONSTRAINING HYDROMETEOR SIZE-FALL-SPEED RELATIONSHIPS. TOGETHER THESE MEASUREMENTS FILL THE CRITICAL MISSING LINK FOR LINKING CHANGES IN LIQUID AND ICE PHASE PRECIPITATION PROCESSES TO VARYING METEOROLOGICAL CONDITIONS AND AEROSOL CONCENTRATIONS ON THE GLOBAL SCALE. THIS EFFORT WILL BE TIGHTLY COORDINATED WITH OTHER ACE PREPARATORY ACTIVITIES THROUGH REGULAR TELECONFERENCES AND WORKSHOPS TO ENSURE MAXIMUM PROGRESS IN DEFINING TRACEABLE INSTRUMENT SPECIFICATIONS AND LAYING THE GROUNDWORK FOR RETRIEVAL ALGORITHMS THAT ADDRESS THE CORE AEROSOL-CLOUD-PRECIPITATION PROCESS MISSION OBJECTIVES OF ACE.