Mass spectrometry in the stratosphere

During the last few years a gas expansion system, combined with a mass spectrometer has been developed and successfully flown in the stratosphere. Neutral gas particles are formed into a molecular beam which traverses the ion source of the mass spectrometer without wall interactions. Vertical profiles of constituents such as H₂O, CO₂ and O₃ have been measured in the altitude range of 20 to 40 km during balloon descents. Isotopes of major atmospheric gases (N₂, O₂, Ar) provided in-flight calibration standards.Before each flight the mass spectrometer system was calibrated in the laboratory for many gases of interest, including ozone. Mixing ratios of ozone determined from recent flights have accuracies of better than 5%. The sensitivity of the system was sufficiently high to detect, in addition, the heavy isotope of ozone at mass 50. A pronounced enhancement of heavy ozone in the upper stratosphere has been found. The mass spectrometer system provides the unique opportunity to perform in the stratospherein-situ measurements combined with isotopic studies.     

Signatures of the Sudden Stratospheric Warming events of January–February 2008 in Seoul,S. Korea

The period January–February 2008 was characterized by four Sudden Stratospheric Warmings (SSWs) in the Northern Hemisphere, of which the last warming, at the end of February 2008, was a major warming. A significant decrease in mesospheric water vapour (H₂O) of more than 2 ppmv (∼40%) was observed by the ground-based microwave (GBMW) radiometer in Seoul, S. Korea [37.3°N, 126.3°E] during the major SSW. A comparison with ground-based mesospheric H₂O observations from the mid-latitude station in Bern [46.9°N, 7°E] revealed an anticorrelation in the mesospheric H₂O data during the major SSW. In addition, prior to the major warming, strong periodic fluctuations were recorded in the Aura MLS vertical temperature distribution between 15 and 0.05 hPa at Seoul. The mesospheric temperature oscillation was found to have a period of ∼10–14 days with a persistency of 3–4 cycles.     

The influence of the several very large solar proton events in years 2000–2003 on the neutral middle atmosphere

Solar proton events (SPEs) are known to have caused changes in constituents in the Earth’s polar neutral middle atmosphere. The past four years, 2000–2003, have been replete with SPEs. Huge fluxes of high energy protons entered the Earth’s atmosphere in periods lasting 2–3 days in July and November 2000, September and November 2001 and October 2003. The highly energetic protons produce ionizations, excitations, dissociations and dissociative ionizations of the background constituents, which lead to the production of HO_x (H, OH, HO₂) and NO_y (N, NO, NO₂, NO₃, N₂O₅, HNO₃, HO₂NO₂, ClONO₂, BrONO₂). The HO_x increases lead to short-lived ozone decreases in the polar mesosphere and upper stratosphere due to the short lifetimes of the HO_x constituents. Large mesospheric ozone depletions (>70%) due to the HO_x enhancements were observed and modeled as a result of the very large July 2000 SPE. The NO_y increases lead to long-lived stratospheric ozone changes because of the long lifetime of the NO_y family in this region. Polar total ozone depletions >1% were simulated in both hemispheres for extended periods of time (several months) as a result of the NO_y enhancements due to the very large SPEs.     

The variability of stratospheric nitrogen compounds observed by LIMS in the winter of 1978–1979

The LIMS experiment was launched on the Nimbus 7 satellite for the purpose of sounding the vertical structure of temperature and key upper atmosphere trace gases on a global scale. The technique of thermal infrared limb sounding was used to obtain measurements of O₃, H₂O, NO₂, and HNO₃. LIMS collected data almost continuously from late October to late May over the latitude range from 64°S to 84°N. Two of the gases, NO₂ and HNO₃, are important elements in the NO_x chain of chemical reactions leading to ozone destruction. We will describe results for these gases in terms of zonal mean profiles and latitudinal distributions. The period selected for study is January–May 1979, when a major stratospheric warming occurred.     

The global distribution and variability of stratospheric constituents measured by LIMS

The purpose of the Nimbus 7 LIMS experiment was to sound the composition and structure of the upper atmosphere and provide data for study of photochemistry, radiation, and dynamics processes. Vertical profiles were measured of temperature and ozone (O₃) over the 10-km to 65-km range and water vapor (H₂O), nitrogen dioxide (NO₂), and nitric acid (HNO₃) over the 10-km to ～50-km range. Latitude coverage extended from 64°S to 84°N. Several general features of the atmosphere have emerged from data analyses thus far. Nitrogen dioxide exhibits rapid latitudinal variations in winter and shows hemispheric asymmetry with generally higher vertical column amount in the summer hemisphere. HNO₃ data show that this gas is highly variable with altitude, latitude, and season. Smallest mixing ratios occur in the tropics, and the largest values occur in the high latitude winter hemisphere. The results show that O₃, NO₂, and HNO₃ are strongly affected during a stratospheric warming. There is a persistently low water vapor mixing ratio in the tropical lower stratosphere (～2–3 ppmv), a poleward gradient at all times in the mission, and evidence of increasing mixing ratio with altitude at tropical and middle latitudes.     

Mesospheric H2O and H2O2 densities inferred from in situ positive ion composition measurement

The measurements of positive ion composition in the high latitude D-region have revealed an excess of 34⁺ under distrubed conditions which has been interpreted as H₂O₂⁺. At the same altitude range near the transition height oxonium ions were measured as well. This paper presents a new model for the production and loss of oxonium ions with their production from H₂O₂⁺ + H₂O → H₃O⁺ + HO₂ and their loss by attachment of N₂ and/or CO₂. A reaction constant of 8.5×10^?28 (300/T)⁴ cm⁶s^?1 has been obtained for the three body attachment H₃O⁺ + CO₂ + M → H₃O⁺.CO₂ + M from the measured density profile of 63⁺ in flight 18.1020. Mesospheric H₂O and H₂O₂ densities are inferred from measurements of four high latitude ion compositions based on the oxonium model. The mixing ratios of hydrogen peroxide are up to two orders of magnitude higher compared to previous model calculations. In order to explain the missing production of odd hydrogen, we consider larger O(¹D) densities, surface reactions of O(³P) on particles, and cathalytic photodissociation of water vapor on aerosol particles.     

Measurement of minor species (H2, Cl,O3, NO) in the earth's atmosphere by the occultation technique

The stellar occultation technique is a clean and powerful means of detecting and quantifying minor gases in the earth's atmosphere. The results obtained are totally insensitive to knowledge of the absolute flux of the star, and are not influenced by instrument calibration problems. Pioneering observations of nocturnal mesospheric ozone and thermospheric molecular oxygen by the stellar occultation technique were made in 1970 and 1971 with the Wisconsin stellar photometers on board the Orbiting Astronomical Observatory-2. A limb crossing geometry was used. The high resolution Princeton ultraviolet spectrometer aboard Copernicus was used in the summers of 1975, 1976 and 1977 to measure altitude profiles of molecular hydrogen, atomic chlorine and nitric oxide in addition to ozone and molecular oxygen. A limb grazing geometry was employed. The ozone densities show wide variation from orbit to orbit and particularly betewen the OAO-2 and Copernicus observations. A H₂ density of 1×10⁸ cm^?3 at 95 km, and a NO density less than 10⁶ cm^?3 for altitudes greater than 85 km were measured.     

Ozone variability related to several SEP events occurring during solar cycle no. 23

Data from geostationary operational environmental satellite (GOES) series were used to identify intense solar energetic particle (SEP) events occurred during the solar activity cycle no. 23. We retrieved O₃, NO, NO₂, HNO₃, OH, HCl and OHCl profiles coming from different satellite sensors (solar occultation and limb emission) and we looked for the mesospheric/stratospheric response to SEPs at high terrestrial latitudes. The chemistry of the minor atmospheric components is analysed to evaluate the associated odd nitrogen (NO_x) and odd hydrogen (HO_x) production, able to cause short (h) and medium (days) term ozone variations. We investigated the effects of SEPs on the polar atmosphere in three different seasons, i.e., January 2005, April 2002 and July 2000. The inter-hemispheric variability of the ozone, induced by the SEP series of January 2005, has been compared with the effects connected both to larger and quite similar events. We found that during SEP events: (i) solar illumination is the key factor driving SEP-induced effects on the chemistry of the polar atmosphere; (ii) even events with limited particle flux in the range 15–40 MeV are able to change the abundance of the minor constituents in the mesosphere and upper stratosphere.     

Composition of the Venus atmosphere below 100 km altitude

Our current knowledge on the composition of the Venus atmosphere in the altitude range from the surface to 100 km is compiled. Gases that have been measured, and whose mixing ratios are assumed to be constant with altitude, are CO₂, N₂, He, Ne, Ar, and Kr. Gases that have been identified in the lower and/or middle atmosphere, but whose mixing ratios may depend on altitude, latitude and/or local time, are CO, H₂O, HCl, HF, and SO₂. Conflicting data or only upper limits exist on some important trace gases, such as O₂, H₂, and Cl₂. The latter two are key constituents in the photochemistry of the middle atmosphere of Venus. The chapter concludes with a listing of the isotopic abundances of elements measured in the Venus atmosphere.     

Quantitative determination of the outgassing water vapor concentrations surrounding space vehicles from ion mass spectrometer measurements

Outgassing from materials as well as deliberate gaseous and liquid releases create contaminant clouds around spacecraft that can degrade both instrumentation and measurements. This paper describes a new method for estimating outgassing water vapor concentrations around space vehicles. Water vapor ions measured in the course of a rocket experiment performed at Eglin AFB, Florida, on December 12, 1980 at 2311 UT are utilized to demonstrate the technique. The H₂O concentration near the payload's surface is calculated using the rate coefficient for the fast charge transfer process, O⁺ + H₂O + H₂O⁺ + O, the source of the observed water vapor ions. It is found that the measured H₂O⁺ ions were produced within 3–4 cm of the sampling plate's surface and that the average H₂O pressure over this distance was relatively constant on ascent at 8 × 10^?6 torr, within a factor two, implying a steady outgassing rate.     

Positive ion composition and electron density in a combined auroral and NLC event

The positive ion composition and electron density were measured in the lower ionosphere above Kiruna in salvo A of CAMP (Cold Arctic Mesopause Project). The CAMP/P (S37/P) payload carrying a magnetic ion spectrometer, positive ion and electron probes, and propagation experiments was launched on 3 August 1982 2332 UT during extended Noctilucent Clouds (NLC) and auroral activities over Kiruna. The measured electron density was 5×10³cm^?3 at 80 km and 2.5×10⁵cm^?3 at 90 km. The increase of ion and electron densities in the D- and E-region during twilight was caused by precipitating auroral particles. The height distribution of the positive ions measured by the mass spectrometer in the mass range 19–280 amu is different from a winter flight with similar auroral conditions. Below 85.5 km proton hydrates H⁺(H₂O)₃ ? H⁺(H₂O)₈ were the dominant ions. The heaviest proton hydrates H⁺(H₂O)₇ and H⁺(H₂O)₈ were most abundant at 82–85.5 km, the altitude of visible NLC. Above 85.5 km O₂⁺ and NO⁺ became dominant. A small metal ion layer was observed between 90.5–93 km with a maximum ion density of 10% of the total positive ion density at 91 km altitude. The metal ion density disappeared within about a km below 90.5 km.     

First observation of upper mesospheric semi annual oscillations using ground based airglow measurements from Indian low latitudes

We summarize two years of Mesosphere Lower Thermosphere Photometer (MLTP) operation of mesospheric OH and O₂ emission monitoring. The deduced mesospheric OH and O₂ temperatures show large variability. Nightly temperature variations over Gadanki (13.5°N, 79.2°E) are dominated by the short period wave features, while tidal amplitudes are relatively small. Our measurements are the first to report a long period seasonal variation at two upper mesospheric altitudes simultaneously over the Indian sector. Our observations reveal the presence of a dominant semi-annual oscillation (∼6 months periodicity) together with a shorter period (∼2.5  months periodicity) oscillation in both OH and O₂ data.     

Measurements of H I and O VI velocity distributions in the extended solar corona with UVCS/SOHO and UVCS/Spartan 201

The Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory, UVCS/SOHO, and the Ultraviolet Coronal Spectrometer on the Spartan 201 satellite, UVCS/Spartan, have been used to measure H I 1215.67 Å line profiles in polar coronal holes of the Sun at projected heliocentric heights between 1.5 and 3.0 R_⊙. UVCS/SOHO also measured line profiles for H I 1025.72 Å, O VI 1032/1037 Å, and Mg X 625 Å. The reported UVCS/SOHO observations were made between 5 April and 21 June 1996 and the UVCS/Spartan observations were made between 11 and 12 April 1993. Both sets of measurements indicate that a significant fraction of the protons along the line of sight in coronal holes have velocities larger than those for a Maxwellian velocity distribution at the expected electron temperature. Most probable speeds for O⁵⁺ velocity distributions along the lines of sight are smaller than those of H⁰ at 1.5 R_⊙, are comparable at about 1.7 R_⊙ and become significantly larger than the H⁰ velocities above 2 R_⊙. There is a tendency for the O⁵⁺ line of sight velocity distribution in concentrations of polar plumes to be more narrow than those in regions away from such concentrations. UVCS/SOHO has identified 31 spectral lines in the extended solar corona.     

铝合金阳极化膜上铈转化膜沉积的电化学研究

阳极氧化膜在含1g/L CeCl₃和2.7 g/L H₂O₂的水溶液中阴极电解可以在其表面沉积富铈转化膜.用循环伏安、φ-t和j-t曲线等电化学测试方法对转化膜成膜反应进行了研究,以期获得对成膜机理的深入了解和证实根据其它工作提出的成膜机理.研究结果表明铈转化膜的生成包括阳极氧化膜的化学溶解和4价铈化合物的电化学还原两个过程;在阴极电位达到析氢电位之前,这两个过程主要是由H₂O₂在阴极的电还原改变了阴极表面附近溶液的局部pH值引起的,而O₂的还原通常不能引起这两个过程的发生.      

The identification of mesospheric frontal gravity-wave events at a mid-latitude site

Mesospheric frontal-type gravity waves are an uncommon type of wave disturbance that occurs in the mesospheric OH, Na, O₂, and O(¹S) nightglow. They are understood to be the result of gravity waves exhibiting various degrees of non-linear behavior. Despite their similar appearance in all-sky images, careful analysis reveals that there are at least two distinct types of frontal wave disturbances, each with completely different consequences in terms of vertical momentum transport and deposition. Therefore, a correct identification is important in order to characterize their propagation modes. In this report we present the frontal gravity wave activity that occurred during a twelve-month period at Millstone Hill (42.6°N, 172.5°W), a mid-latitude site, to illustrate their range of behaviors.     

Temporal variation of the volume emission rates between OI5577 and O2(0,1)

The intensities of the upper mesospheric airglow emissions, OI 557.7 nm and O₂(b) atmospheric (0,1) band at 864.5 nm, have been measured since October 1998 using a ground-based multichannel airglow photometer located near the equator at São João do Cariri (7S, 35W). The intensity ratio between the two emissions, OI5577/O₂b(0,1), was obtained as a function of time. The annual average of the ratio R in 1998 was 0.41 ± 0.14, and showed considerable day to day variations, ranging from 0.2 to 0.6. Nocturnal variations of the ratio also demonstrate a large amplitude of oscillation, varying between 0.3 to 0.6. These results were compared with a model calculation.     

Measurement of stratospheric trace constituent distributions from balloon-borne far infrared observations

Far infrared limb thermal emission spectra obtained from balloon borne measurements made as a part of the Balloon Intercomparison Campaign (BIC) have been analyzed for retrieval of stratospheric trace constituent distributions. The measurements were made with a high resolution Michelson Interferometer and covered the 15–180 cm⁻¹ spectral range with an unapodized spectral resolution of 0.0033 cm⁻¹. The retrieved vertical profiles of O₃, H₂O, HDO, HCN, CO and isotopes of O₃ are presented. The results are compared with the BIC measurements for O₃ and H₂O made from the same balloon gondola and with other published data. A comparison of the simultaneously retrieved profiles for several gases with the published data shows good agreement and indicates the validity of the far infrared data, the retrieval techniques and the accuracy of the inferred profiles.     

Greenhouse gases and recovery of the Earth’s ozone layer

A numerical 2-D zonally averaged dynamical radiative-photochemical model of the ozonosphere including aerosol physics is used to examine the role of the greenhouse gases CO₂, CH₄, and N₂O in the recovery of the Earth’s ozone layer after reduction of anthropogenic discharges of chlorine and bromine compounds into the atmosphere. A weakness in efficiencies of all catalytic cycles of the ozone destruction due to cooling of the stratosphere caused by greenhouse gases is shown to be a dominant mechanism of the impact of the greenhouse gases on the ozone layer. Numerical experiments show that the total ozone changes caused by greenhouse gases will be comparable in absolute value with the changes due to chlorine and bromine species in the middle of the 21st century. Continuous anthropogenic growth of CO₂ will lead to a significantly faster recovery of the ozone layer. In this case, the global total ozone in the latitude range from 60°S to 60°N will reach its undisturbed level of 1980 by about 2040. If the CO₂ growth stops, the global total ozone will reach this level only by the end of the century.     

The infrared synthetic spectrum of comet Halley

In order to prepare infrared sounding of comet Halley from the flyby VEGA probes, we have computed the synthetic spectrum between 2.5 and 15 μ of a typical comet at a heliocentric distance of ～ 0.8 AU. The present paper is particularly devoted to the contribution from the cometary gases. For a selection of 20 possible parent molecules, the most efficient excitation process is resonant fluorescence by the solar radiation field. The H₂O, CO, CO₂, CH₄, NH₃ and H₂CO molecules are the best candidates for detection by the IKS infrared spectrometers aboard the VEGA probes. For the water molecule, collisions are too rare to ensure thermal equilibrium in the whole coma ; therefore a limited number of fluorescence lines are expected to be present in the H₂O vibrational bands.