O3 H2O Research Articles

Mixing characteristics within the tropopause transition layer over the Asian summer monsoon region based on ozone and water vapor sounding data

The structure of the tropopause transition layer (TTL) over the Asian summer monsoon (ASM) anticyclone is analyzed on the basis of high-resolution balloon soundings of temperature, ozone, and water vapor at Kunming and Lhasa, China during 11 summer monsoon seasons between 2009 and 2019. Two definitions of the TTL, one based on thermal structure and one based on tracer correlations of O3 and H2O, are analyzed and compared. In tracer–tracer space, the air masses of mixed stratospheric and tropospheric characteristics are identified by using the O3–H2O correlations. The mixed air formed a transitional layer and shows strong spatial variation in the altitude space. Statistical result shows that the altitude range of mixed air parcels spans a layer of approximately 5.5 km depth between 12.5 km and 18 km. This vertical distribution of mixed air masses is basically consistent with thermally-based TTL, which takes the level of minimum stability (LMS) and the cold point tropopause (CPT) as its lower and upper boundaries, respectively. The thermal definition regards the TTL as a thermal transition zone, but does not consider the tracer mixing features between stratosphere and troposphere. Tracer correlations can identify the mixed air mass, which is a basic feature of the TTL, whether they are from the range of the thermally-based TTL, or below the LMS, or above the CPT. Based on the O3–H2O correlations, statistical analysis shows that about 30%–50% of air masses between the LMS and the CPT are identified as mixed. And up to 1–1.5 km above the CPT, a small fraction of air masses is also mixed, which means that air masses from the troposphere can be lifted and mixed into the free stratosphere within the ASM anticyclone region.

Growth modulation of atomic layer deposition of HfO2 by combinations of H2O and O3 reactants.

Atomic layer deposition (ALD) is a thin film deposition technique based on self-saturated reactions between a precursor and reactant vacuum conditions. A typical ALD reaction consists of the first half-reaction of the precursor and the second half-reaction of the counter reactant, in which the terminal groups on the surface change after each half-reaction. In this study, the effects of counter reactants on the surface termination and growth characteristics of ALD HfO2 thin films formed on Si substrates using tetrakis(dimethylamino)-hafnium (TDMAH) as a precursor were investigated. Two counter reactants, H2O and O3, were individually employed, as well as in combination with consecutive exposure by H2O-O3 and O3-H2O. The film growth behaviors and properties differed when the sequence of exposure of the substrate to the reactants was varied. Based on X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) simulation, the changes are attributed to the effects of the surface terminations formed from different counter reactant combinations. The knowledge from this work could provide insight for precisely tuning the growth and properties of ALD films.

Theoretical insight towards the photo-dissociation dynamics of O3–H2O complex: Deep understanding the source of atmospheric hydroxyl radical

To explore the dynamic mechanism of the hydroxyl radical generation from the ozone–water complex and its atmospheric implications, the intrinsic reaction coordinate computations and ab initio molecular dynamic simulations were used to map the minimum energy profiles of O3 and O3–H2O complex photo-dissociation and inspect photo-dissociation feasibility for different complex conformers. The stable trans isomer possesses a small portion in seven coexistent O3–H2O complex conformers, 70% of which is the unique source to produce OH radicals in SPP(D̃1A′,1ππ∗) state. The quantum yield of atmospheric hydroxyl radical through the ozone–water complex photolysis is much lower than the previous expectation.

Kinetics of the gas‐phase reaction of CF3OC(O)H with OH radicals at 242–328 K

AbstractThe rate constants, k1, of the reaction of CF3OC(O)H with OH radicals were measured by using a Fourier transform infrared spectroscopic technique in an 11.5‐dm3 reaction chamber at 242–328 K. OH radicals were produced by UV photolysis of an O3–H2O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during UV irradiation. With CF3OCH3 as a reference compound, k1 at 298 K was (1.65 ± 0.13) × 10−14 cm3 molecule−1 s−1. The temperature dependence of k1 was determined as (2.33 ± 0.42) × 10−12 exp[−(1480 ± 60)/T] cm3 molecule−1 s−1; possible systematic uncertainty could add an additional 20% to the k1 values. The atmospheric lifetime of CF3OC(O)H with respect to reaction with OH radicals was calculated to be 3.6 years. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 337–344 2004

Rate constants for the gas‐phase reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals at 250–430 K

AbstractThe rate constants k1 for the reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm3 reaction chamber with either CHF2Cl or CH2FCF3 as a reference compound. OH radicals were produced by UV photolysis of an O3–H2O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k1 (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10−15 cm3 molecule−1 s−1 (FP‐LIF method) and (1.72 ± 0.07) × 10−15 cm3 molecule−1 s−1 (LP‐LIF method), whereas the K1 (298 K) values determined by the relative method were (1.87 ± 0.11) × 10−15 cm3 molecule−1 s−1 (CHF2Cl reference) and (2.12 ± 0.11) × 10−15 cm3 molecule−1 s−1 (CH2FCF3 reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K1 = (4.71 ± 0.94) × 10−13 exp[−(1630 ± 80)/T] cm3 molecule−1 s−1. Using kinetic data for the reaction of tropospheric CH3CCl3 with OH radicals [k1 (272 K) = 6.0 × 10−15 cm3 molecule−1 s−1, tropospheric lifetime of CH3CCl3 = 6.0 years], we estimated the tropospheric lifetime of CF3CF2CF2CF2CF2CHF2 through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004

Comparison of infrared and Dobson total ozone columns measured from Lauder, New Zealand

Ozone total columns have been derived from 13 spectral intervals in 5 infrared bands and compared with values deduced from correlative measurements with a Dobson spectrophotometer. The observations were recorded on 10 days in 1994 at the Network for the Detection of Stratospheric Change station in Lauder, New Zealand. The infrared total columns were derived from spectral fittings of unblended, temperature‐insensitive ozone lines in high resolution solar absorption spectra. The line parameters on the 1992 HITRAN compilation were assumed with the O3 H2O relative volume mixing ratio and temperature profiles specified from correlative balloon ozonesonde, microwave O3, and radiosonde measurements. The retrieved IR/Dobson total column ratios ranged from 0.96 to 1.02 with the lower wavenumber bands yielding lower ratios. The results do not support the revised O3 intensity scale currently used to process O3 infrared measurements from 2 instruments on the Upper Atmosphere Research Satellite.

Tracer Study of the Reactivity of O(1D)

The transfer of oxygen from water to oxygen in the uv photolysis of O3–H2O mixtures is studied as a function of the ozone and water vapor pressures using 18O-labeled H2O. It is shown that deactivation of the active species is generally competitive with the ordinary chemical reactions these species undergo. It is also shown that the reaction of O1D with H2O is about four times slower than its reaction with O3. The quantum yields at different O3 and H2O pressures are calculated from the exchange data. Some preliminary experiments on the exchange of O1D with N2O and in somewhat more detail on the CO2–O2 exchange during the uv decomposition of O3 are also reported.