HR: 1330h
AN: A32B-0152    [PDF]
TI: Analysis of {\it in Situ} Measurements of Chlorine and Bromine Species in the Arctic Winter Stratosphere and Development of an Instrument for {\it in Situ} Atmospheric Measurements of IO
AU: * Wilmouth, D M
EM: wilmouth@huarp.harvard.edu
AF: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, MA 02138 United States
AU: Stimpfle, R M
EM: stimpfle@huarp.harvard.edu
AF: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, MA 02138 United States
AU: Hanisco, T F
EM: hanisco@huarp.harvard.edu
AF: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, MA 02138 United States
AU: Co, D T
EM: co@fas.harvard.edu
AF: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, MA 02138 United States
AU: Anderson, J G
EM: anderson@huarp.harvard.edu
AF: Harvard University, Department of Chemistry and Chemical Biology, Cambridge, MA 02138 United States
AB: {\it In situ} measurements of ClO, ClOOCl, ClONO$_{2}$, and BrO were acquired with the Harvard Halogen flight instrument onboard the NASA ER-2 aircraft in the Arctic stratosphere during the winter of 1999-2000. These chlorine measurements, along with measurements of HCl and total inorganic chlorine, Cl$_{y}$, enable the first analysis of the inorganic chlorine budget in the Arctic vortex. The results indicate excellent agreement between the sum of the measured species (ClO + 2$\times$ClOOCl + ClONO$_{2}$ + HCl) and Cl$_{y}$ in January and early February; however, the budget agreement becomes significantly worse during early to mid-March. The source of the March budget discrepancy is explored, revealing evidence that supports the validity of the ClO, ClOOCl, and ClONO$_{2}$ measurements. The BrO measurements represent a substantial improvement in sensitivity, precision, and spatial resolution relative to those acquired previously onboard the ER-2. Modifications to the BrO detection system, laboratory calibrations, and analysis of {\it in situ} BrO data successfully obtained during twelve flights of the 1999-2000 winter are presented. The Harvard Halogen instrument is currently being modified to include IO detection capabilities. The observed long-term trend in mid-latitude Northern Hemisphere ozone in the lower stratosphere over the last two decades may be the result of increased catalytic loss of ozone by the rate-limiting halogen radicals ClO, BrO, and IO. This makes measuring all three of these halogen oxides critical. The motivation and method of IO detection will be discussed. Specifically, measuring IO {\it in situ} requires the sensitivity to detect sub parts per trillion concentrations. Based on the known laser characteristics of the OH and NO$_{2}$ laser systems used in this laboratory and the known collection efficiency of the detection optics, we expect a sensitivity of better than 10$^{5}$ cm$^{-3}$ for IO.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting