Simultaneous, in situ measurements of OH and HO_2 in the stratosphere

Stratospheric OH and HO_2 radical densities have been measured between 36 and 23 km using a balloon-borne, in situ instrument launched from Palestine, TX on August 25, 1989. OH is detected using the laser-induced fluorescence technique (LIF) employing a Cu-vapor-laser pumped dye laser coupled with an enclosed-flow detection chamber. HO_2 is detected nearly simultaneously by adding No to the sample flow to convert ambient HO_2 to OH. Observed OH and HO_2 densities ranged from 8.0 ± 2.8 × 10^6 and 1.4 ± 0.5 × 10^7 molec cm^(−3), respectively, at 36 km, to 1.4± 0.5 × 10^6 and 3.0± 1.0 × 10^6 at 23 km, where the uncertainty is ±1σ. The HO_2 density exhibits a maximum in the 34–30 km of 1.7±0.6 × 10^7. The data were obtained over a solar zenith angle variation of 51° at 36 km to 61° at 23 km. O_3 and H_2O densities also were measured simultaneously with separate instruments

Balloon borne in-situ detection of OH in the stratosphere from 37 to 23 km

The OH number density in the stratosphere has been measured over the altitude interval of 37 to 23 km at midday via a balloon-borne gondola launched from Palestine, Texas on July 6, 1988. OH radicals are detected with a laser induced fluorescence instrument employing a 17 kHz repetition rate copper vapor laser pumped dye laser optically coupled to an enclosed flow, in-situ sampling chamber. OH abundances ranged from 88±31 pptv (1.1 ± 0.4 × 10^7 molec cm^(−3)) in the 36 to 35 km interval to 0.9 ± 0.8 pptv (8.7 ± 7.7 × 10^5 molec cm^(−3)) in the 24 to 23 km interval. The stated uncertainty (±1σ) includes that from both measurement precision and accuracy. Simultaneous detection of ozone and water vapor densities was carried out with separate on-board instruments

The Development and Deployment of a Ground-Based, Laser-Induced Fluorescence Instrument for the In Situ Detection of Iodine Monoxide Radicals

High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer. Of particular interest are the roles IO plays in the formation of new particles in coastal marine environments and in depletion episodes of ozone and mercury in the Arctic polar spring. This paper describes a ground-based instrument that measures IO at mixing ratios less than one part in 1012. The IO radical is measured by detecting laser-induced fluorescence at wavelengths longer that 500 nm. Tunable visible light is used to pump the A23/2 (v = 2) X23/2 (v = 0) transition of IO near 445 nm. The laser light is produced by a solid-state, Nd:YAG-pumped Ti:Sapphire laser at 5 kHz repetition rate. The laser-induced fluorescence instrument performs reliably with very high signal-to-noise ratios (>10) achieved in short integration times (<1 min). The observations from a validation deployment to the Shoals Marine Lab on Appledore Island, ME are presented and are broadly consistent with in situ observations from European Coastal Sites. Mixing ratios ranged from the instrumental detection limit (<1 pptv) to 10 pptv. These data represent the first in situ point measurements of IO in North America

Simultaneous, in situ measurements of OH, HO_2, O_3, and H_2O: A test of modeled stratospheric HO_x chemistry

Simultaneous, in situ measurements of OH, HO_2, H_2O, and O_3 from 37–23 km are reported. The partitioning between OH and HO_2 and the total HO_x concentration are compared with expected steady-state values. The ratio of HO_2 to OH varies from less than 2 at 36 km to more than 3 at 25 km; in the lower stratosphere this ratio is nearly a factor of two less than predicted. The data are used to calculate HO_x production and loss rates. The measured HOx mixing ratio is consistent with production dominated by the reaction of O(1D) with H_2O, and loss controlled by NO_y below 28 km and HO_x above 30 km. The steady-state concentration of H_2O_2 is inferred from the measured HO_2 concentration and calculated photolysis rate. The maximum H_2O_2 mixing ratio (at 33 km) is predicted to be less than 0.2 ppb

Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals

The odd-hydrogen radicals OH and HO2 are central to most of the gas-phase chemical transformations that occur in the atmosphere. Of particular interest is the role that these species play in controlling the concentration of stratospheric ozone. This paper describes an instrument that measures both of these species at volume mixing ratios below one part in 10(exp 14) in the upper troposphere and lower stratosphere. The hydroxyl radical (OH) is measured by laser induced fluorescence at 309 nm. Tunable UV light is used to pump OH to the first electric state near 282 nm. the laser light is produced by a high-repetition rate pulsed dye-laser powered with all solid-state pump lasers. HO2 is measured as OH after gas-phase titration with nitric oxide. Measurements aboard a NASA ER-2 aircraft demonstrate the capability of this instrument to perform reliably with very high signal-to-noise ratios (greater than 30) achieved in short integration times (less than 20 sec)

Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals

The odd-hydrogen radicals OH and HO2 are central to most of the gas-phase chemical transformations that occur in the atmosphere. Of particular interest is the role that these species play in controlling the concentration of stratospheric ozone. This paper describes an instrument that measures both of these species at volume mixing ratios below one part in 10^14 in the upper troposphere and lower stratosphere. The hydroxyl radical (OH) is measured by laser induced fluorescence at 309 nm. Tunable UV light is used to pump OH to the first electronic state (A-tilde 2Sigma+(v[script ']=1) ~30) achieved in short integration times (< 20 sec)