AMMONIA (NH3) IS THE MOST IMPORTANT ATMOSPHERIC BASE AND CONTRIBUTES TO NITROGEN DEPOSITION AND PM2.5 FORMATION. UNDERSTANDING NH3 EMISSIONS IS CRITICAL FOR AIR QUALITY MANAGEMENT BUT THESE EMISSIONS HAVE SIGNIFICANT UNCERTAINTIES DUE TO SPATIOTEMPORAL VARIABILITIES. SATELLITE INSTRUMENTS PROVIDE A NEW APPROACH TO ANALYZE THE HETEROGENEITIES OF NH3 ON A GLOBAL SCALE. HOWEVER MOST SATELLITE MEASUREMENTS HAVE NOT BEEN VALIDATED AT THE PIXEL SCALE DUE TO LACK OF IN-SITU NH3 PROFILES. IN THIS PROJECT I WILL STUDY THE EFFECTIVENESS OF USING REMOTE SENSING TO STUDY TROPOSPHERIC NH3. FIRST I WILL DEVELOP AN ALGORITHM TO VALIDATE IASI AND CRIS SATELLITE DATA USING IN-SITU NH3 PROFILES FROM THE NASA DISCOVER-AQ COLORADO AND CALIFORNIA CAMPAIGNS. THE IN-SITU DATA WILL BE FILTERED BY A SPATIOTEMPORAL WINDOW FROM 0-60 KM AND 0-180 MIN CENTERING ON THE OVERPASS TIME AND SATELLITE PIXEL. IF THEY MATCH I WILL INTEGRATE IN-SITU NH3 PROFILES IN FOUR WAYS TO ACCOUNT FOR ISSUES SUCH AS SAMPLING BIASES AND ALTITUDE MISMATCH AND COMPARE THEM WITH SATELLITE COLUMNS. IF FTIR DATA MATCH WITH SATELLITE I WILL ALSO COMPARE THEM. CASE STUDY SHOWS GOOD AGREEMENT BETWEEN IASI NH3 AND DISCOVER-AQ COLORADO DATA. AFTER THAT I WILL STUDY HOW SATELLITE OVERPASS MEASUREMENT TIMES REPRESENT THE TEMPORAL VARIABILITY OF NH3 AT OTHER TIMES BY USING THE DISCOVER-AQ DATA AND LONG-TERM IN-SITU MEASUREMENTS COLLECTED IN MY RESEARCH. I WILL INTEGRATE IASI AND CRIS DAILY NH3 MEASUREMENTS ANALYZE THE TEMPORAL TRENDS AND COMPARE THEM WITH DISCOVER-AQ. I WILL ALSO COMPARE SATELLITE NH3 WITH IN-SITU DATA MEASURED AT DUKE FOREST AND ROCKY MOUNTAIN NATIONAL PARK BY OUR GROUP AND USE THE COMMUNITY MULTI-SCALE AIR QUALITY NH3 MODEL TO QUANTIFY VEGETATIVE NH3 FLUXES. FINALLY I WILL EXAMINE THE SPATIOTEMPORAL VARIABILITY OF NH3 IN AGRICULTURAL REGIONS IN THE U.S. SPECIFICALLY EXAMINING HOW SATELLITES CAN OBSERVE FERTILIZATION EMISSIONS AND HOW THIS DATABASE CAN BE USED TO IMPROVE EMISSION INVENTORIES. I WILL RESEARCH THE NATIONAL EMISSION INVENTORY DATABASE AND PLOT TEMPORAL NH3 DATA TO IDENTIFY FERTILIZATION PEAKS. THEN I WILL EVALUATE IASI AND CRIS DATA BY PLOTTING WEEKLY-AVERAGED NH3 COLUMNS AND APPLYING A MOVING WINDOW TO SEARCH FOR THE PERIODS WITH SIGNIFICANT COLUMN CHANGES AND COMPARE WITH FERTILIZATION DATA. I WILL CREATE A MAP THAT SPECIFIES THE FERTILIZATION PERIODS ACROSS THE U.S. THIS PROJECT FULFILLS NASA S OBJECTIVE TO ADVANCE KNOWLEDGE OF EARTH AS A SYSTEM TO MEET THE CHALLENGES OF ENVIRONMENTAL CHANGE AND TO IMPROVE LIFE ON OUR PLANET. IN SPECIFIC IT WILL: 1) ADVANCE THE UNDERSTANDING OF CHANGES IN THE EARTH S RADIATION BALANCE AIR QUALITY AND THE OZONE LAYER THAT RESULT FROM CHANGES IN ATMOSPHERIC COMPOSITION AND 2) DETECT AND PREDICT CHANGES IN EARTH S ECOLOGICAL AND BIOGEOCHEMICAL CYCLES INCLUDING LAND COVER BIODIVERSITY AND THE GLOBAL CARBON CYCLE. WE WILL BE ABLE TO UNDERSTAND TO WHAT EXTENT WE CAN USE SATELLITE TO STUDY TROPOSPHERIC NH3 AND ITS SPATIOTEMPORAL VARIABILITIES FROM REGIONAL TO GLOBAL SCALES.