Showing papers by "Paul O. Wennberg published in 1996"
TL;DR: The presence of a significant amount of reactive nitrogen (NO_y) in the layer implies the systematic removal of NO, which is without precedent in stratospheric in situ observations as discussed by the authors.
Abstract: During the 1993 NASA Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE), anomalously low nitric oxide (NO) was found in a distinct sunlit layer located above the mid-latitude tropopause. The presence of a significant amount of reactive nitrogen (NO_y) in the layer implies the systematic removal of NO, which is without precedent in stratospheric in situ observations. Large increases in measured chlorine monoxide (ClO) and the hydroperoxyl radical (HO_2) also were observed in the layer. Heterogeneous reaction rate constants of chlorine nitrate (ClONO_2) with hydrogen chloride (HCl) and H_2O to form nitric acid (HNO_3) on sulfate aerosol are enhanced in the NO removal layer by local increases in H_2O and aerosol surface area. The associated conversion of NO_x (= NO + NO_2) to HNO_3 is the most likely cause of the observed low NO and NO_x/NO_y values and high ClO values.
44 citations
TL;DR: In situ laser-induced fluorescence measurements of atmospheric OH are susceptible to interference from laser generated OH, particularly in the troposphere as discussed by the authors, and they implement the addition of perfluoropropene, C_3F_6, for the chemical removal of atmospheric atmospheric OH from the ambient air.
Abstract: In situ laser-induced fluorescence measurements of atmospheric OH are susceptible to interference from laser generated OH, particularly in the troposphere To quantify this interference we implement the addition of perfluoropropene, C_3F_6, for the chemical removal of OH from the ambient air The removal rate of OH by C_3F_6 is determined in the laboratory using the discharge flow technique Over the temperature range 249 to 296 K the rate constant is (60±08) × 10^(−13) exp[(370±40)/T] cm^³ molecule^(−1) s^(−1), independent of pressure In situ measurements using C_3F_6 addition are performed in both aircraft-borne and ground-based experiments These studies show that laser excitation of the ^²Σ^+(v=1)← ^²Π(v=0) transition (282 nm) at high pulse repetition rates and low peak power can provide reliable and sensitive measurements of tropospheric OH
36 citations