Aircraft observations of biomass burning pollutants in the equatorial lower stratosphere over the tropical western Pacific during boreal winter
Year: 2025
Type: article
Abstract: . Recent studies hypothesize that emissions from fires reaching the stratosphere can provide aerosols and aerosol precursors that initiate stratospheric ozone loss and lead to radiative heating of the stratosphere and cooling of the surface. Air from the troposphere enters the stratosphere primarily over the tropical western Pacific (TWP) during boreal winter. We report observations in the TWP of persistent, ubiquitous continental pollution in the tropical tropopause layer (TTL) and lower stratosphere (LS) during the Airborne Tropical TRopopause EXperiment (ATTREX) campaign in February–March 2014. We found concentrations of carbon monoxide (CO) enhanced up to 65 % over background levels in the deep tropics (5° S–15° N, 16 –17 km). Correlations of CO with hydrocarbon and halocarbon species indicated a biomass burning source, with the largest CO enhancements found in warmer, clear air. Satellite observations of CO did not detect the thin pollution layers observed by the aircraft, but did indicate Africa, Indonesia, and the western/central Pacific as geographical hot spots for CO in the TTL. Backward trajectories identified convective encounters in these areas as the dominant sources of polluted air in the TWP. Africa and Indonesia contributed about 60 % of the excess CO, transported to the TWP in two to four weeks. Our study confirms that air in the TTL over the TWP is affected by emissions from distant fires that can rapidly reach the LS in the principal source region for air entering the stratosphere, supporting the view that fires in tropical regions could impact stratospheric ozone and temperatures.
Institutions: Harvard University, University of Miami, National Oceanic and Atmospheric Administration, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, NOAA Global Monitoring Laboratory, NOAA Chemical Sciences Laboratory, Bay Area Environmental Research Institute, Ames Research Center
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $1,725
Awards: DURING THE FIRST YEAR OF THE PROGRAM WE WILL DESIGN AND BUILD THE MAJORITY OF THE AWAS INSTRUMENT AND ASSOCIATED CONTROLS. FINAL DETAILS WILL BE WOR, G5312368803, DESPITE ITS LOW CONCENTRATION STRATOSPHERIC WATER VAPOR HAS LARGE IMPACTS ON THE EARTH'S ENERGY BUDGET AND CLIMATE. RECENT STUDIES SUGGEST THAT EVEN SMALL CHANGES IN STRATOSPHERIC HUMIDITY MAY HAVE CLIMATE IMPACTS THAT ARE SIGNIFICANT COMPARED TO THOSE OF DECADAL INCREASES IN GREENHOUSE GASES. FUTURE CHANGES IN STRATOSPHERIC HUMIDITY AND OZONE CONCENTRATION IN RESPONSE TO CHANGING CLIMATE ARE SIGNIFICANT CLIMATE FEEDBACKS. WHILE THE TROPOSPHERIC WATER VAPOR CLIMATE FEEDBACK IS WELL REPRESENTED IN GLOBAL MODELS PREDICTIONS OF FUTURE CHANGES IN STRATOSPHERIC HUMIDITY ARE HIGHLY UNCERTAIN BECAUSE OF GAPS IN OUR UNDERSTANDING OF PHYSICAL PROCESSES OCCURRING IN THE TROPICAL TROPOPAUSE LAYER (TTL -13-18 KM) THE REGION OF THE ATMOSPHERE THAT CONTROLS THE COMPOSITION OF THE STRATOSPHERE. UNCERTAINTIES IN THE TTL CHEMICAL COMPOSITION ALSO LIMIT OUR ABILITY TO PREDICT FUTURE CHANGES IN STRATOSPHERIC OZONE. WE PROPOSE A SERIES OF MEASUREMENT CAMPAIGNS USING THE LONG-RANGE NASA GLOBAL HAWK. (GH) UNMANNED AIRCRAFT SYSTEM (UAS) TO DIRECTLY ADDRESS THESE PROBLEMS.A NUMBER OF TIL PROCESSES AFFECT STRATOSPHERIC HUMIDITY AND OZONE: DEEP CONVECTIVE TRANSPORT OF WATER VAPOR AND OTHER CHEMICAL CONSTITUENTS INTO THE TTL; THE FORMATION OF UBIQUITOUS THIN CIRRUS IN THE TTL (WHICH THEMSELVES HAVE A LARGE EFFECT ON THE RADIATION BUDGET AND CLIMATE); LIMITATION OF STRATOSPHERIC HUMIDITY BY SEDIMENTING ICE CRYSTALS IN TTL THIN CIRRUS; SLOW VERTICAL TRANSPORT THROUGH THE TTL; THE EFFECTS OF TROPICAL ATMOSPHERIC WAVES ON TTL THERMAL STRUCTURE DEHYDRATION AND TRANSPORT; AND THE CHEMISTRY OF SHORT-LIVED TRACE GASES.OBSERVATIONS OF TTL COMPOSITION ARE SPARSE COMPARED TO THOSE IN OTHER CLIMATICALLY IMPORTANT REGIONS PARTLY BECAUSE THE HIGH TTL ALTITUDE LIMITS AIRCRAFT SAMPLING. FURTHER THE UTILITY OF SATELLITE MEASUREMENTS OF TTL COMPOSITION IS REDUCED BY THE CHARACTERISTICALLY STRONG VERTICAL GRADIENTS IN THE TTL. AS A RESULT TTL PROCESSES ARE NOT WELL REPRESENTED IN GLOBAL MODELS. THIS INVESTIGATION WILL PROVIDE DATA NEEDED TO ADDRESS THESE SHORTCOMINGS: HIGH SPATIAL RESOLUTION (ONLY OBTAINABLE BY AIRCRAFT) MEASUREMENTS OVER LARGE GEOGRAPHICAL REGIONS (REQUIRING THE GR RANGE) AND OVER MULTIPLE SEASONS.THE PROPOSED INVESTIGATION FILLS SEVERAL SIGNIFICANT GAPS IN ATMOSPHERIC SCIENCE IDENTIFIED IN THE NASA DECADAL SURVEY INVOLVING CLIMATE CHANGE STRATOSPHERIC OZONE AND STRATOSPHERE-TROPOSPHERE EXCHANGE. SCIENCE QUESTIONS THAT WILL BE ADDRESSED INCLUDE THE FOLLOWING:1. WHAT PROCESSES CONTROL THE TROPICAL TROPOPAUSE TEMPERATURE AND THE HUMIDITY OF AIR ENTERING THE STRATOSPHERE (INCLUDING THEIR SEASONAL CYCLES)?2. WHAT ARE THE DOMINANT PATHWAYS FOR VERTICAL TRANSPORT FROM CONVECTIVE DETRAINMENT ALTITUDES IN THE TTL UP TO THE TROPICAL TROPOPAUSE IN DIFFERENT SEASONS?3. WHAT ARE THE FORMATION PROCESSES MICROPHYSICAL PROPERTIES AND CLIMATE IMPACT OF TTL CIRRUS AND HOW DO THESE CLOUDS REGULATE THE HUMIDITY OF AIR ENTERING THE STRATOSPHERE?4. WHAT ARE THE CHEMICAL AND TRANSPORT PROCESSES THAT DRIVE THE BUDGETS OF PRECURSORS OF OZONE-DESTROYING SUBSTANCES SUCH AS SHORT-LIVED HALOGEN COMPOUNDS?5. HOW WILL TTL CIRRUS STRATOSPHERIC HUMIDITY AND STRATOSPHERIC OZONE RESPOND TO A CHANGING CLIMATE AND WHAT ARE THE RESULTING FEEDBACK EFFECTS?, G6640013078
OpenAlex ID: W4413068022