WE PROPOSE SEVERAL OBSERVATIONAL STUDIES OF ATMOSPHERIC CIRCULATION AND VARIABILITY BASED ON THE LONG RECORD OF AURA MICROWAVE LIMB SOUNDER (MLS) MEASUREMENTS COMBINED WITH PARALLEL CHEMISTRY-CLIMATE MODEL RESULTS. WE WILL USE TIME SERIES OF MLS STRATOSPHERIC WATER VAPOR (H2O) MEASUREMENTS TO PROVIDE NEW OBSERVATIONAL ESTIMATES OF THE TRANSIT-TIME OR AGE-OF-AIR SPECTRA IN THE STRATOSPHERE AS A COMPLEMENT TO ANALYSES USING SEVERAL TRACERS WITH DIFFERING CHEMICAL LIFETIMES. OBSERVATIONAL RESULTS WILL BE COMPARED WITH ANALYSES OF CHEMISTRY-CLIMATE MODEL SIMULATIONS FROM WHOLE ATMOSPHERE COMMUNITY CLIMATE MODEL (WACCM) AND A NEW CHEMICAL LAGRANGIAN MODEL OF THE STRATOSPHERE (CLAMS). INITIAL COMPARISONS SUGGEST THAT MORE COMPLETE AGE SPECTRA INFORMATION CAN BE OBTAINED BY INCORPORATING METHANE OXIDATION EFFECTS ON H2O AND WE WILL EXPLORE METHODS TO EVALUATE THIS FROM SATELLITE OBSERVATIONS. A SECOND SET OF STUDIES WILL INVOLVE ANALYSIS OF MLS TEMPERATURE DATA TO EXTEND THE LONG-TERM RECORD OF STRATOSPHERIC TEMPERATURE TRENDS FROM THE STRATOSPHERIC SOUNDING UNIT (SSU). WE WILL ALSO EVALUATE THE MLS TEMPERATURE DATA RECORD IN THE MESOSPHERE TO QUANTIFY VARIABILITY AND COUPLING WITH THE LOWER ATMOSPHERE AND MAKE COMPARISONS TO RESULTS FROM HIGH-TOP CHEMISTRY-CLIMATE MODEL SIMULATIONS.