THE RESEARCH TEAM WILL FIRST EVALUATE AND IMPROVE UPON THE ALGORITHMS USED TO DERIVE ICE WATER CONTENT AND SNOWFALL RATE FROM CLOUDSAT W RADAR REFLECTIVITY MEASUREMENTS AND FOR OTHER RADAR WAVELENGTHS DRAWING UPON THE EXPERTISE OF THE COPI WHO DEVELOPED THE CLOUDSAT 2C SNOW PROFILE DATA PRODUCT. IN GENERAL ZEIWC AND ZES RELATIONSHIPS ARE DEVELOPED USING ICE PARTICLE SIZE DISTRIBUTIONS PSD EITHER MEASURED OR TAKEN FROM THE LITERATURE TOGETHER WITH ASSUMED PARTICLE SHAPES HABITS THAT ARE THEN USED TO ESTIMATE THE BACKSCATTER CROSS SECTIONS AND THE MASSES AND FALL VELOCITIES OF THE ICE HYDROMETEORS. DIFFERENT FROM THAT METHODOLOGY OUR TEAM WILL USE NASA AIRCRAFT FIELD PROGRAM DATA IN MOST CASES WHERE THE ICE WATER CONTENT IS MEASURED DIRECTLY TOGETHER WITH COLLOCATED WBAND RADAR MEASUREMENTS FROM OVERFLYING AIRCRAFT TO DEVELOP ZEIWC AND ZES RELATIONSHIPS. BECAUSE SNOWFALL RATE REQUIRING THE TERMINAL VELOCITY IS DERIVED FROM AVERAGE REPRESENTATIONS REPORTED IN THE LITERATURE OF PREVIOUS STUDIE AND IS LESS CERTAIN THAN THE IWC ESTIMATES AND WILL USE A UNIQUE APPROACH. OUR FIELD PROGRAM DATA INCLUDES AROUND 1 MILLION KM OF INSITU SAMPLED CLOUD WHERE DIRECT MEASUREMENTS OF IWC AND ICE PARTICLE SHAPE AND CONCENTRATION ARE AVAILABLE FROM LOCATIONS RANGING FROM THE ARCTIC TO THE TROPICS. PARTICLE SHAPE INFORMATION WILL ENABLE US TO CALCULATE MORE ACCURATE TERMINAL VELOCITY VALUES AND THUS SNOWFALL RATES WHICH WE WILL RELATE TO THE DIRECTLY MEASURED IWC TO IMPROVE IWC S RELATIONSHIPS. THUS THE CLOUDSAT 2CICE IWC RETRIEVALS INVOLVING FEWER ASSUMPTIONS THAN THE 2C SNOW PROFILE RETRIEVALS CAN PROVIDE A SECOND METHOD TO DERIVE SNOWFALL RATES.THE RESEARCH TEAM WILL THEN USE CLOUDSAT RADAR OBSERVATIONS TOGETHER WITH THOSE FROM RADARS ON OTHER SATELLITES TRMM IN PARTICULAR TO DETERMINE WHAT FRACTION OF THE EARTH S PRECIPITATION ORIGINATES FROM THE ICE PHASE AT GEOGRAPHIC LOCATIONS THROUGHOUT THE WORLD. WE WILL THEN USE THESE RESULTS TO EVALUATE VALIDATE SNOW AND RAIN PRECIPITATION PRODUCTS FROM THE NCAR COMMUNITY ATMOSPHERE MODEL CAM GLOBAL CLIMATE MODEL AND THE UK MET OFFICE UNIFIED MODEL. DIFFERENCES BETWEEN THE OBSERVATIONS AND MODELS WILL BE CHARACTERIZED SPATIALLY VERTICALLY AND SEASONALLY TO IDENTIFY WEAKNESS IN THE MODELS AND WITH THE EVENTUAL GOAL OF IMPROVING THEM.