WE INTEND TO PROPOSE AN EARTH VENTURE SUBORBITAL MISSION TO INVESTIGATE THE DYNAMICS AND CHEMISTRY OF THE SUMMER STRATOSPHERE OVER CENTRAL NORTH AMERICA. A FIELD MEASUREMENT CAMPAIGN WILL FOCUS ON OBSERVATIONS WITH THE NASA ER-2 HIGH-ALTITUDE RESEARCH AIRCRAFT. IN ORDER TO INVESTIGATE BOTH SHORT-TIMESCALE PROCESSES AND INTERANNUAL VARIABILITY WE PLAN TO MAKE FIELD OBSERVATIONS DURING TWO CONSECUTIVE SUMMER SEASONS. THE IN SITU OBSERVATIONS FROM THE AIRCRAFT WILL BE COMBINED WITH OBSERVATIONS FROM SATELLITES AND GROUND-BASED RADARS OPERATIONAL METEOROLOGICAL ANALYSES AND REGIONAL AND GLOBAL DYNAMICAL AND CHEMICAL MODELS TO ADDRESS THE ROLE OF CONVECTION IN THE COMPOSITION AND DYNAMICS OF THE LOWER STRATOSPHERE OVER NORTH AMERICA DURING SUMMER. THE PROPOSED RESEARCH WILL LAY THE SCIENTIFIC FOUNDATION FOR UNDERSTANDING HOW THE SUMMERTIME STRATOSPHERIC ENVIRONMENT INCLUDING THE PROTECTIVE STRATOSPHERIC OZONE LAYER WILL CHANGE AS THE CLIMATE AND COMPOSITION OF THE EARTH'S ATMOSPHERE CHANGE OVER THE COMING CENTURY.