WE PROPOSE A PROJECT FOCUSED ON STUDYING TROPICAL CYCLONES (TCS) IN A NEW VERSION OF THE NASA GISS CLIMATE MODEL AT 0.5 DEGREE (50 KM) HORIZONTAL GRID SPACING. OUR PROJECT WILL HAVE TWO COMPONENTS. IN THE FIRST WE WILL EXPERIMENT WITH PHYSICS AND NUMERIC PARAMETERS TO DEVELOP A MODEL THAT WILL BE COMPETITIVE FOR THE STUDY OF TROPICAL CYCLONES ON THE GLOBAL SCALE. IN THE SECOND WE WILL USE THE MODEL FOR SCIENTIFIC STUDIES OF TROPICAL CYCLONES AND CLIMATE. THE HIGHEST RESOLUTION VERSION OF THE GISS MODEL TO PRESENT HAS BEEN ONE WITH 1 DEGREE HORIZONTAL GRID SPACING. THE TCS IN THIS MODEL ARE SIMILAR TO THOSE IN OTHER LOW-RESOLUTION MODELS: THEY HAVE LOW INTENSITIES VERY LARGE SPATIAL SCALES AND PERSISTENT BIASES IN THEIR CLIMATOLOGICAL GENESIS LOCATIONS (PARTICULARLY TOO FEW STORMS IN THE NORTH ATLANTIC AND EASTERN NORTH PACIFIC). RESEARCH WITH OTHER MODELS HAS SHOWN THAT A TRANSITION TO MUCH HIGHER-FIDELITY SIMULATIONS OF TCS OFTEN OCCURS AS HORIZONTAL RESOLUTION DROPS BELOW 1 DEGREE. TC SIMULATION ALSO DEPENDS CRITICALLY ON MODEL PHYSICS AND NUMERICS HOWEVER. EXPERIMENTATION COUPLED WITH CAREFUL MODEL EVALUATION IS NEEDED TO DEVELOP A MODEL WHICH SIMULATES TCS WELL ON THE GLOBAL SCALE WITHOUT DEGRADING THE QUALITY OF THE BROADER CLIMATE SIMULATION. FOR MODEL DEVELOPMENT WE WILL CONDUCT EXPERIMENTS IN WHICH ASPECTS OF THE MODEL PHYSICS AND NUMERICS ARE VARIED AND EVALUATE THE RESULTS TO EXAMINE BOTH TCS AND THE BROADER MODEL CLIMATE. THE PHYSICS TESTING WILL FOCUS ON THE MODEL CONVECTIVE PARAMETERIZATION SPECIFICALLY PARAMETERS RELATED TO ENTRAINMENT RAIN RE-EVAPORATION AND COLD POOLS. OUR TEAM HAS SUBSTANTIAL EXPERIENCE WITH THIS SCHEME HAVING DEVELOPED MODIFICATIONS IN PAST PROJECTS WHICH HAVE NOW BECOME PART OF THE OPERATIONAL MODEL DUE TO OUR ANALYSIS OF THE IMPROVEMENTS IN THE SIMULATED MADDEN-JULIAN OSCILLATION WHICH RESULTED FROM THEM. MODEL NUMERICS TESTS WILL INCLUDE THE ROLE OF DIVERGENCE DAMPING A PARAMETER SHOWN TO BE IMPORTANT IN TC SIMULATION IN THE HIGH-RESOLUTION GLOBAL MODELS AT THE NOAA GEOPHYSICAL FLUID DYNAMICS LABORATORY (GFDL) WHICH ARE ARGUABLY THE BEST IN THE WORLD FOR TCS. AS WE VARY THE MODEL WE WILL CAREFULLY EVALUATE THE MODEL S SIMULATION OF TC NUMBERS INTENSITIES AND PATTERNS OF GENESIS AND TRACKS AS WELL AS ITS MEAN CLIMATE AND SUBSEASONAL VARIABILITY TO DETERMINE THE OPTIMAL CONFIGURATION. STUDIES OF THE INFLUENCE OF CLIMATE CHANGE ON TCS WILL BUILD ON OUR PRIOR EXPERIENCE FROM THE US CLIVAR HURRICANE WORKING GROUP AND RELATED PROJECTS IN WHICH WE HAVE BOTH CONTRIBUTED SIMULATIONS WITH THE 1 DEGREE GISS MODEL AND DIAGNOSED RESULTS FROM MANY OTHER MODELS. WE WILL PERFORM SIMULATIONS FOR A RANGE OF WARMING SCENARIOS EXAMINING THE ROLES OF SEA SURFACE TEMPERATURE CHANGE DIRECT GREENHOUSE GAS AND AEROSOL FORCINGS (USING THE ATMOSPHERIC MODEL COUPLED TO A SLAB OCEAN MIXED LAYER) AND OTHER INFLUENCES. AN AREA OF PARTICULAR INTEREST AND ONE VERY LITTLE STUDIED PREVIOUSLY WILL BE THE INFLUENCE OF CLIMATE CHANGE ON TCS WHICH MAKE EXTRATROPICAL TRANSITION SUCH AS HURRICANE SANDY (2012). IN ADDITION TO STUDYING THE INFLUENCE OF CLIMATE CHANGE ON TCS WE WILL ALSO STUDY THE INFLUENCE OF THE EL NINO-SOUTHERN OSCILLATION (ENSO) PHENOMENON. TROPICAL CYCLONES ARE AMONG THE MOST DESTRUCTIVE NATURAL HAZARDS. HOW THEY WILL CHANGE AS THE CLIMATE WARMS REMAINS AN IMPORTANT QUESTION WITH SIGNIFICANT UN-ANSWERED ASPECTS. HIGH-RESOLUTION MODELS HAVE BEEN CRITICALLY IMPORTANT TOOLS IN IMPROVING CONFIDENCE IN OUR UNDERSTANDING OF THE TC-CLIMATE RELATIONSHIP OVER THE LAST DECADE. NASA GISS HAS BEEN LARGELY LEFT OUT OF THIS ACTIVITY DUE TO THE LACK OF A SUFFICIENTLY HIGH-RESOLUTION GISS MODEL. THIS IS ABOUT TO CHANGE AND OUR PROJECT WILL AID THIS TRANSITION. THIS PROPOSAL IS RELEVANT TO THE THEME EXTREMES IN THE EARTH SYSTEM WITHIN THE MAP SOLICITATION.