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Aircraft and Balloon Measurements of Trace Gases and Modeling of Transport in the Upper Troposphere and Lower Stratosphere |
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Recent technological advances in gas chromatography have enabled us to obtain high-resolution (1-6 minutes) measurements of important greenhouse (N2O, CH4, SF6), ozone depleting (CFCs, halons), and air quality gases (PAN, H2, CO, hydrocarbons or HCs) in the upper troposphere and lower stratosphere (UT/LS) on board airborne platforms. Three airborne gas chromatographs have been operated on NSF, NOAA, and NASA airplanes, unmanned Aircraft systems (UAS)and on a special carriage traveling along the Trans-Siberian Railway. Depending on the configuration of columns, flows, and temperatures, these airborne gas chromatographs (GCs) can measure a variety of organic chlorine and bromine, and other long-lived species in the troposphere and the stratosphere to altitudes of 32 km. Recent measurements in the UT/LS have spanned all latitudes between 70oS and 90oN in several seasons over the past 12 years. All airborne GCs can measure trace amounts of sulfur hexafluoride (SF6), which can be used to directly determine the mean age of a sampled air parcel. Age is an important parameter in helping us to understand ozone and climate changes that may be produced by operating an aircraft in the UT/LS. Tracer relationships are also important for establishing the ozone depletion potentials, relative lifetimes of species, and transport parameters (e.g., tropical pipeline versus global diffuser). One airborne GC, Lightweight Airborne Chromatograph Experiment, which can be used on a balloon platform, has been successfully operated to altitudes up to 32 km in the tropical, mid-latitude, and polar stratosphere. A new airborne GC has been outfitted with a mass selective detector along with four standard detectors. The new GC can measure the above standard gases including organic nitrates (e.g., PAN), HCs, and COS at ambient conditions. Measurements from all airborne instruments will permit modeling of the transport and calculation of the mixing rates of mid-latitude air into the tropical stratosphere. A related long-term goal is to monitor the decline in the mixing ratios of the CFCs and halons, and their replacement compounds in the stratosphere resulting from provisions of the Montreal Protocol. |
NOAA ESRL Contact CIRES Contact |
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