DIVERSE METEOROLOGICAL PROCESSES ASSOCIATED WITH MID?LATITUDE CYCLONES (E.G. COLD AND WARM FRONTS DRY LINES MESO?SCALE CONVECTIVE SYSTEMS) PLAY DISTINCT ROLES IN DISTRIBUTING ATMOSPHERIC GREENHOUSE GASES (GHG E.G. CO2 CH4) AND OTHER ATMOSPHERIC CONSTITUENTS (E.G. AEROSOLS WATER VAPOR O3). HOWEVER OUR UNDERSTANDING OF THE HORIZONTAL STRUCTURES AND VERTICAL VARIABILITY IN GHGS ACROSS FRONTAL BOUNDARIES REMAINS LIMITED. WITHIN THE ATMOSPHERIC CARBON AND TRANSPORT AMERICA (ACT?AMERICA A NASA EARTH VENTURE SUBORBITAL PROJECT) FOR THE FIRST TIME SIMULTANEOUS REMOTE SENSING AND IN?SITU MEASUREMENTS OF ATMOSPHERIC GHGS AND STATE VARIABLES WERE COLLECTED ACROSS MANY DIFFERENT FRONTS WITHIN THE ATMOSPHERIC BOUNDARY LAYER (ABL) AND FREE TROPOSPHERE (FT) COVERING ALL FOUR SEASONS (SUMMER 2016 WINTER 2017 FALL 2017 AND SPRING 2018) IN THREE REGIONS OF THE UNITED STATES (MID?ATLANTIC MID?WEST AND SOUTH). BY DEPLOYING TWO NASA AIRCRAFT (C?130 AND B?200) ACT?AMERICA CAMPAIGNS CUMULATIVELY COLLECTED MORE THAN 850 HOURS OF HIGH?RESOLUTION (5S) AIRBORNE IN?SITU AND REMOTE SENSING MEASUREMENTS WITH SUFFICIENT SPATIAL RESOLUTION (500M) TO DETECT GHG DISTRIBUTIONS AND ADEQUATE SPATIAL COVERAGE (UP TO 1800 KM WITHIN A SINGLE RESEARCH FLIGHT) TO COVER A LARGE FRACTION OF THE GHG AND METEOROLOGICAL STRUCTURES ASSOCIATED WITH THE MID?LATITUDE STORMS. WITHIN THIS PROJECT WE WILL EXPLORE THE OBSERVATIONAL ASPECTS OF THE FOLLOWING THREE RESEARCH TOPICS (RTS) WITH AN EMPHASIS ON THE REMOTELY SENSED COLUMN?AVERAGE CO2 (XCO2) MEASUREMENTS OBTAINED BY THE MFLL (MULTI?FUNCTIONAL FIBER LASER LIDAR ONBOARD C?130 AIRCRAFT) INSTRUMENT. WE WILL ALSO PERFORM COMPARISON OF THE OBSERVATIONAL FINDINGS AGAINST THE AVAILABLE WRF?CHEM SIMULATIONS. RESEARCHERS AT PENN STATE WILL CREATE HIGH?RESOLUTION WRFCHEM RESULTS ALONG THE FLIGHT TRACK AND MAKE THOSE AVAILABLE TO THE RESEARCHERS AT TEXAS TECH UNIVERSITY.