DROUGHTS AND HEAT WAVES ARE EXTREME EVENTS THAT OCCUR REGULARLY IN MANY REGIONS CAUSING SIGNIFICANT AND OFTEN PERSISTENT DISRUPTIONS TO AGRICULTURE HUMAN HEALTH AND ECOSYSTEMS. RECENT NOTABLE EVENTS WITH SIGNIFICANT CONSEQUENCE FOR ECOSYSTEMS AND SOCIETIES INCLUDE HEAT WAVES IN EUROPE IN 2003 AND RUSSIA IN 2010 DROUGHTS IN THE LEVANT AND CENTRAL PLAINS AND THE ONGOING MULTI-YEAR DROUGHT IN CALIFORNIA. BECAUSE THE IMPACTS OF DROUGHTS AND HEAT WAVES ARE SO LARGE THERE IS INTEREST IN IMPROVING OUR UNDERSTANDING OF HOW CLIMATE CHANGE WILL AFFECT THESE EXTREMES. BUT TO IMPROVE OUR CONFIDENCE IN THESE MODEL PROJECTIONS WE NEED BETTER EVALUATIONS OF HOW WELL MODELS SIMULATE THESE EXTREMES AND IMPROVED CONSTRAINTS ON THE PROCESS BASED UNCERTAINTIES RELATED TO NATURAL SOURCES OF VARIABILITY INCLUDING SEA SURFACE TEMPERATURES (SST) INTERNAL (UNFORCED) ATMOSPHERIC DYNAMICS AND LAND-ATMOSPHERE FEEDBACKS. THE PRIMARY GOAL OF THIS PROPOSAL IS TO IMPROVE OUR UNDERSTANDING OF THE VARIABILITY AND PHYSICAL DRIVERS OF DROUGHTS AND HEAT WAVES IN THE NORTHERN HEMISPHERE EXTRA-TROPICS USING OBSERVATIONS AND NEW SIMULATIONS OF THE NASA GODDARD INSTITUTE FOR SPACE STUDIES (GISS) GENERAL CIRCULATION MODEL (GCM) MODELE . USING MODELE ONE OF NASA S CORE MODELING EFFORTS AND NASA OBSERVATIONS AND REANALYSES WE WILL INVESTIGATE NATURAL AND ANTHROPOGENIC CONTRIBUTIONS TO DROUGHT AND HEAT WAVE DYNAMICS DURING THE HISTORICAL PERIOD AND IN THE COMING DECADES. OUR SPECIFIC RESEARCH OBJECTIVES ARE TO: ANALYZE DROUGHTS AND HEAT WAVES IN OBSERVATIONS AND DIFFERENT CONFIGURATIONS OF MODELE (E.G. OCEAN FORCING LAND SURFACE COUPLING) TO IMPROVE OUR UNDERSTANDING OF THE CONTRIBUTIONS OF SST FORCING INTERNAL ATMOSPHERIC VARIABILITY AND LAND-ATMOSPHERE INTERACTIONS (OBJECTIVE #1); INVESTIGATE THE IMPACT OF IMPORTANT BUT UNDER-INVESTIGATED PROCESSES (IRRIGATION FIRE) ON MODELED DROUGHTS AND HEAT WAVES (OBJECTIVE #2); CONDUCT NEW EXPERIMENTS WITH MODELE TO EVALUATE HOW VARIATIONS IN ANTECEDENT SEASONAL CONDITIONS IN THE LAND SURFACE (SOIL MOISTURE) AND ATMOSPHERE (PERSISTENT HIGHS) AFFECT THE OCCURRENCE AND INTENSITY OF SUMMER DROUGHTS AND HEAT WAVES (OBJECTIVE #3); INVESTIGATE HOW NATURAL VARIABILITY AND ANTHROPOGENIC CHANGES IN THE CLIMATE SYSTEM INTERACT TO AFFECT THE RISK AND INTENSITY OF DROUGHT AND HEAT WAVE EVENTS ANALOGOUS TO RECENT EXTREMES (E.G. EARLY 21ST CENTURY DROUGHT IN THE LEVANT AND SYRIA 2010 RUSSIAN HEAT WAVE ETC) (OBJECTIVE #4) WE WILL USE INDICES AND DEFINITIONS OF HEAT WAVES AND DROUGHTS THAT CAN EASILY BE TRANSLATED BETWEEN OBSERVATIONS AND MODELE AND LEVERAGE SOME OF THE UNIQUE CAPABILITIES OF MODELE TO ANALYZE INTERACTIONS BETWEEN THESE EXTREMES AND UNDER-EXPLORED PROCESSES IN THE EARTH SYSTEM (IRRIGATION AND FIRE). THIS WORK WILL RESULT IN AN IMPROVED UNDERSTANDING OF THE NATURAL CLIMATE VARIATIONS DRIVING HEAT AND DROUGHT EXTREMES AND BETTER CONFIDENCE IN OUR ABILITY TO USE CLIMATE MODELS TO INVESTIGATE THESE EVENTS.