bluuebunny/crossref_metadata_2025 huggingface dataset:
Airborne intercomparison of nitric oxide measurement techniques
Authors: Hoell James M. , Gregory Gerald L. , McDougal David S. , Torres Arnold L. , Davis Douglas D. , Bradshaw John , Rodgers Michael O. , Ridley Brian A. , Carroll Mary Anne
Published: February 2008

Results from an airborne intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted during missions flown in the fall of 1983 and spring of 1984. Instruments intercompared included a laser‐induced fluorescence (LIF) system and two chemiluminescence instruments (CL). NO mixing ratios from below 5 pptv (parts per trillion by volume) to greater than 100 pptv were reported, with the majority less than 20 pptv. Good correlation was observed between the measurements reported by the CL and LIF techniques. The general level of agreement observed for the ensemble of measurements obtained during the two missions provides the basis from which one can conclude that equally “valid” measurements of background levels of NO can be expected from either CL or LIF instruments. At the same time the periods of disagreement that were observed between the CL and LIF instruments as well as between the two CL instruments highlight the difficulty of obtaining reliable measurements with NO mixing ratios in the 5–20 pptv range and emphasize the vigilance that should be maintained in future NO measurements.
Carbon kinetic isotope effect in the reaction of CH4 with HO
Authors: Davidson J. A. , Cantrell C. A. , Tyler S. C. , Shetter R. E. , Cicerone R. J. , Calvert J. G.
Published: February 2008

The carbon kinetic isotope effect in the CH4 + HO reaction can enrich atmospheric methane in 13C relative to its sources. In the only previous measurement of the carbon kinetic isotope effect in this reaction, a value of k12/k13 of 1.003 was reported. In the present experimental determination we have found a significantly larger kinetic isotope effect of 1.010±0.007 (95% confidence interval). This report discusses the experimental details of the carbon kinetic isotope effect determination in the CH4 + HO reaction and the possible atmospheric implications in the use of the present result. Tropospheric methane is known to have a 13C/12C ratio of −47‰ (parts per thousand) relative to Peedee belemnite, and most known methane sources for which measurements of the stable carbon isotope ratio have been performed are depleted in 13C relative to the atmosphere. A k12/k13 ratio of 1.010 leads to an expected value for the weighted average of the 13C/12C ratio of the methane sources which is about 10‰ more depleted than the atmosphere (approximately −57‰). This result is fundamentally important to those researchers who use stable carbon isotope ratios to study atmospheric methane.
Mass accommodation coefficient for HO2 radicals on aqueous particles
Authors: Mozurkewich Michael , McMurry Peter H. , Gupta Anand , Calvert Jack G.
Published: February 2008

The rate of reaction of gas phase HO2 radicals with a monodisperse, submicrometer aerosol was measured in a flow tube reactor at atmospheric pressure. At the relative humidity of the experiments (75%), the aerosol consisted of concentrated solution droplets of either LiNO3 or NH4HSO4. When the aerosol contained a sufficient amount of Cu(II) ions, reaction of HO2 with the aerosol was observed. The mass accommodation coefficient for HO2 on aqueous particles was determined to be greater than 0.2. This implies that in clouds HO2 mass transport will be limited by gas‐phase diffusion and HO2 will be in equilibrium at the gas‐liquid interface. Reactions of HO2 with Cu(I) and Cu(II) ions in submicrometer aerosols may have a significant role in converting atmospheric odd hydrogen radicals into H2O2.
Climate warming due to increasing atmospheric CO2: Simulations With a multilayer coupled atmosphere‐ocean seasonal energy balance model
Authors: Peng Li , Chou Ming‐Dah , Arking Albert
Published: February 2008

The multilayer energy balance model of Peng et al. (1982) has been further developed to include a simple two‐dimensional advective‐diffusive deep ocean and to allow seasonal variation in order to study long‐term transient climate response to a CO2increase as well as its seasonal pattern. Comparisons between the model‐simulated present climate and conventional and satellite data show that the model can simulate well the annual cycle of the surface temperature and the radiation budget of the atmosphere. In response to a hypothetical step function doubling of atmospheric CO2, the model reaches within 1/eof the equilibrium response of global mean surface temperature (2.6°C) in 9–35 years for the probable range of vertical heat diffusivity in the ocean. This large range of response time underlies the importance of properly using the heat diffusion coefficient in ocean models. In response to a projected CO2trend based on estimates by the Carbon Dioxide Assessment Committee (National Research Council 1983), the model's transient response in annually and globally averaged surface temperature is 60–75% of the corresponding equilibrium response. The disequilibrium increases with increasing oceanic heat diffusivity. When the atmospheric CO2level reaches twice the current level, in about a century, the global mean surface temperature increases by 1.5°–2.0°C, depending on the heat diffusivity of the ocean. Local warming at certain times of the year, however, may be 2–3 times greater than the annual and global average. In the northern high latitudes the response undergoes significant seasonal and latitudinal variations. A maximum occurs in the early winter, and a secondary maximum occurs in the spring. In the southern hemisphere, large responses are confined to a narrow latitude zone bordering Antarctica and occur only in the cold months. The pattern of the seasonal and latitudinal distribution of the transient response remarkably resembles that of the equilibrium response to a doubling of CO2. This agrees with Bryan et al. (1982) and Spelman and Manabe (1984), implying that sensitivity studies of equilibrium climate can be used as a guide for predicting the latitudinal pattern of a warming trend. The abovementioned transient response is obtained by integrating the model from the equilibrium state corresponding to the year 1975. A comparison between this and another numerical integration of the model starting from the equilibrium state corresponding to the CO2level in 1925 shows that the atmospheric CO2increase before 1975 has only a very small effect on the model response after the year 2000.
Problems in interpretation of power spectra of cloud fields
Authors: O'Brien D. M.
Published: February 2008

A recurrent suggestion in the literature is that the spatial variability of cloud might best be studied through the power spectrum of the cloud field. In this paper this proposal is examined in the context of radiative transfer by broken cloud. Through the analysis of numerical models in one and two dimensions, three conclusions are drawn: (1) Fields with the same power spectrum may transmit different average fluxes, so the power spectrum alone does not determine the radiative transfer. (2) The power spectrum of both the models and real cloud fields (advanced very high resolution radiometer satellite images) oscillate so rapidly that quantitative analysis of the power spectrum is very sensitive to the manner in which the power spectrum is sampled. The most stable analysis of the power spectrum involves integration over all spatial frequencies. It will be shown how this procedure permits the calculation of infrared transfer in a one‐dimensional cloud model. (3) A proposal for a satellite‐mounted optical Fourier analyzer is examined, and it is shown that while such an instrument eliminates aliasing and computational restraints, the need to compress the data by logarithmic sampling of the power spectrum impairs the resolution of the correlation function of the cloud field. Furthermore, the degradation of the resolution increases with the correlation length.
Equatorial ozone profiles from the ground to 52 km during the southern hemisphere autumn
Authors: Barnes Robert A. , Holland Alfred C. , Kirchhoff Volker W. J. H.
Published: February 2008

We report the results of an ozone measurement campaign conducted at Natal, Brazil (5.9°S, 35.2°W) from March 25 to April 15, 1985. Seven profiles were obtained during this period, using ROCOZ‐A and electrochemical concentration cell ozonesondes, standard U.S. meteorological radiosondes, and Super‐Loki datasondes. Complete profiles of ozone, pressure, and temperature were obtained from the ground to 52 km, and all of the profiles correspond with site overpasses by ozone instruments on NASA and National Oceanic and Atmospheric Administration satellites. The profiles from this measurement series show reasonable agreement with established satellite climatologies. Stratospheric ozone variability was 2% or less during the 3 weeks of the measurement campaign, with stratospheric temperature and pressure variabilities half that amount. Low variability at a single location for this period implies comparable uniformity for ozone profiles over a large area around the measurement site. This condition at Natal removes the requirement of exact concurrence between satellite and local ozone measurements, allowing comparisons of larger sets of profiles and improving the precision of the intercomparisons. Regional ozone stability also allows an overall intercomparison of ozone measurements among the four satellites without the need for zonal mean averages. The auxiliary pressure and temperature profiles presented here allow the use of this data set as a transfer standard between satellite instruments with different fundamental ozone measurements. Finally, the low ozone variability in the stratosphere at Natal during this measurement series should provide an opportunity for high‐quality intercomparisons of measured and modeled ozone concentrations in the equatorial stratosphere and lower mesosphere as well as a consistency check among satellite ozone measurements.
A numerical modeling study of a Montana thunderstorm: 2. Model results versus observations involving electrical aspects
Authors: Helsdon John H. , Farley Richard D.
Published: February 2008

In this investigation we compare the results of the Storm Electrification Model (SEM) simulation of the July 19 Cooperative Convective Precipitation Experiment (CCOPE) case study cloud against the actual observations with respect to the cloud's electrical characteristics, as deduced from the data of two aircraft. It is found that the SEM reproduces the basic charge and electric field structure of the cloud on a time scale similar to that observed. The comparability of the modeled and observed values of field strength and charge within the cloud is directly related to the proximity of the aircraft to the main active core of the cloud. The character of the electric field external to the cloud appears to be well modeled, at least at the time of observation. A feature which was not observed, but appears in the model, is a charge‐screening layer at the top of the anvil. In addition, the model predicts electric field strengths sufficient to initiate a lightning discharge at approximately the same time in cloud evolution as that when an intracloud discharge was recorded.
Atmospheric distribution of 85Kr simulated with a general circulation model
Authors: Jacob Daniel J. , Prather Michael J. , Wofsy Steven C. , McElroy Michael B.
Published: February 2008

A three‐dimensional chemical tracer model for the troposphere is used to simulate the global distribution of 85Kr, a long‐lived radioisotope released at northern mid‐latitudes by nuclear industry. Simulated distributions for the period 1980–1983 are in excellent agreement with data from six latitudinal profiles measured over the Atlantic. High concentrations of 85Kr are predicted over the Arctic in winter, advected from European sources, and somewhat smaller enhancements arising from the same sources are predicted over the tropical Atlantic in summer. Latitudinal gradients are steepest in the northern tropics, with distinctly different seasonal variations over the Pacific, as compared to the Atlantic. The global inventory of 85Kr is reconstructed for the period 1980–1983 by combining the concentrations measured over the Atlantic with the global distributions predicted by the model. The magnitude of the Soviet source is derived. The interhemispheric exchange time is calculated as 1.1 years, with little seasonal dependence.
On the interpretation of zenith sky absorption measurements
Authors: Solomon Susan , Schmeltekopf Arthur L. , Sanders Ryan W.
Published: February 2008

Observations of several atmospheric species can be performed by measuring the absorption of visible and near‐ultraviolet light scattered from the zenith sky. The determination of vertical column abundances of molecules such as ozone and NO2 from such measurements is briefly reviewed. It is shown that the conversion of NO to NO2 can be of significance in the interpretation of measurements made near twilight. On the other hand, multiple scattering from the atmosphere or by clouds is likely to be a very small effect.
Relative levels of natural and anthropogenic lead in recent Antarctic snow
Authors: Boutron Claude F. , Patterson Clair C.
Published: February 2008

Concentrations of lead have been measured by ultraclean isotope dilution mass spectrometry in large blocks of surface snow collected along a 433‐km coast‐interior axis in East Antarctica and near the geographic south pole. Slight contamination existed on the outside of the blocks, but concentration profiles from their exteriors to their interiors indicate that lead concentrations in the innermost parts of the blocks do represent the original concentrations in present‐day Antarctic snow. Geographical variations of lead concentrations appear to be mainly due to local emissions from Dumont d'Urville and Amundsen Scott stations. The globally significant lead concentration in present‐day Antarctic snow is found to be about 2 pg Pb/g. The corresponding value in Antarctic air is estimated to be about 7 pg Pb/m3 STP, which is approximately fivefold larger than total natural lead contributed by soil dusts, volcanoes and sea salts. A tentative temporal curve of globally significant lead concentrations in Antarctic ice and snow for the last 13,000 years is given. It shows concentrations of about 0.4 pg Pb/g throughout most of the Holocene, with recent fivefold increases to about 2 pg Pb/g today. The general picture is then that four‐fifths of total lead in the Antarctic troposphere today is anthropogenic.
Trace elements in the atmosphere of American Samoa: Concentrations and deposition to the tropical South Pacific
Authors: Arimoto Richard , Duce Robert A. , Ray Barbara J. , Hewitt Alan D. , Williams John
Published: February 2008

As part of the SEAREX (Sea‐Air Exchange) Program, samples of aerosol particles, rain, and dry deposition were collected from an 18‐m‐high tower on American Samoa, in the tropical South Pacific. The mineral aerosol concentration at Samoa (∼10 ng m−3) was among the lowest ever recorded for the near‐surface troposphere; it was far lower and also less variable than the mean concentrations observed during the high‐ and low‐dust seasons at Enewetak (∼1000 and ∼100 ng m−3, respectively), the site of a previous SEAREX experiment in the tropical North Pacific. Atmospheric concentrations of Cu, I, Pb, Sb, Se, and Zn were higher than those expected from mineral aerosol or atmospheric sea salt. These anomalously enriched elements (AEEs) generally exhibited lower concentrations at Samoa, but for Se and I, which may have important biological sources in the oceans, the differences in concentrations at the two sites were small. Higher enrichments of the AEEs relative to oceanic and crustal sources occurred at Samoa, suggesting that the atmospheric residence times of these elements are longer than those of mineral particles or that their sources are more widespread than those of mineral dust. Wet deposition appears to be quantitatively more important than dry deposition for the air‐to‐sea transfer of mineral dust, and recycled sea spray evidently accounts for a significant fraction of the airsea exchange of the enriched trace elements.
Cokriging radar‐rainfall and rain gage data
Authors: Krajewski Witold F.
Published: February 2008

An ordinary cokriging procedure has been developed to optimally merge rainfall data from radars and standard rain gages. The radar‐rainfall data are given in digitized form. The covariance matrices required to perform cokriging are computed from single realization data, using the ergodicity assumption. Since the ground truth and the error structure of the radar data are unknown, parameterization of the covariance between radar data and the true rainfall is required. The sensitivity of the procedure to that parameterization is analyzed within a controlled simulation experiment. The experiment is based on a hypothesized error structure for the rainfall measurements. The effect of measurement noise and network density is examined. The usefulness of the procedure to remove the bias in radar is tested. Daily data are used.
Effects of Doppler shifting on the frequency spectra of atmospheric gravity waves
Authors: Fritts David C. , VanZandt T. E.
Published: February 2008

Spectra of atmospheric motions as a function of observed frequency may depart significantly from the spectra as a function of intrinsic frequency due to a nonzero mean wind. In this paper we examine the effects of Doppler shifting on a model spectrum of atmospheric gravity waves. In order to gain insight into the effects of Doppler shifting, we have derived analytic solutions by approximation of the intrinsic frequency spectra and the gravity wave dispersion relation. Our results reveal that Doppler shifting can have major effects on the observed frequency spectrum of both horizontal and vertical gravity wave energy. For levels of Doppler shifting representative of the lower and middle atmosphere, possible effects include a substantial enhancement of horizontal energy density at higher observed frequencies, a corresponding reduction of the vertical energy density at higher frequencies, and a significant transfer of vertical energy to observed frequencies above the buoyancy frequency. The predicted effects are found to be consistent with some of the features of the observed frequency spectra.
Acid dew and the role of chemistry in the dry deposition of reactive gases to wetted surfaces
Authors: Chameides William L.
Published: February 2008

Using the resistance model for mass transfer, a formulation is derived for the dry deposition rate of a reactive, soluble gas depositing on a wetted, vegetative surface. The deposition velocity is expressed in terms of a dynamical resistance, which is a function of the physical state of the atmosphere, and a surface resistance, which is a function of the chemical and physical properties of the surface. This formulation is then used in a model to simulate the generation of acidic dew from the dry deposition of HNO3 and SO2, as well as the SIV oxidants, H2O2 and O3. Dewdrop pHs of about 4 are calculated by the end of the night, however these pHs can rapidly fall to potentially toxic levels soon after sunrise as the dewdrops evaporate. The deposition velocities to the dew for highly soluble species such as HNO3 and H2O2 are found to be entirely determined by the dynamical resistance; for the conditions adopted here a value of 0.4 cm s−1 is calculated for these species. However, much smaller deposition velocities are predicted for SO2 and O3 because of their lower solubilities and hence larger surface resistances. In the case of SO2, a nocturnally averaged deposition velocity of only about 0.03 cm s−1 is calculated for the standard model. Because the chemical lifetime of SO2 in the dew is influenced by the atmospheric levels of H2O2, O3, and SO2, the SO2 deposition velocity is found to be a strong function of these species' atmospheric abundances. These results imply that the deposition velocities of species such as SO2 to wetted surfaces may be influenced by the chemical as well as the physical state of the atmosphere; the assumption typically adopted that dry deposition velocities are independent of the species' atmospheric abundance may not always be appropriate.
Simultaneous in situ measurements and diurnal variations of NO, NO2, O3, jNO2, CH4, H2O, and CO2 in the 40‐ to 26‐km region using an open path tunable diode laser spectrometer
Authors: Webster Christopher R. , May Randy D.
Published: February 2008

Simultaneous in situ measurements of [NO], [NO2], [O3], jNO2, [CH4], [H2O], [CO2], pressure, and temperature in the 40 to 26‐km region of the stratosphere were made from Palestine, Texas (32°N), on October 16, 1986, using the Jet Propulsion Laboratory (JPL) Balloon‐borne Laser In Situ Sensor (BLISS) instrument, carrying a University of Denver jNO2 instrument piggyback. Using tunable diode laser absorption spectroscopy over a long path length, measurements were made as follows during a 21‐hour flight: daytime [NO], [NO2], [O3], and NO2 near 40 km; [NO], [NO2], and NO2 through the sunset transition near 40 km; postsunset measurements of the rate of decay of [NO2] into the night over the 35 to 29‐km range; nighttime measurements of [NO2], [O3], [CH4], [H2O], and [CO2] at 27 km; and [NO] after sunrise. The NO, NO2, O3, CH4, H2O, and CO2 concentration measurements generally show good agreement with previous observations, with a tendency for somewhat lower NO2 amounts. Measured O3 concentrations at 38 km agree well with comparable measurements from in situ UV photometers, but at 28 km they are lower by about 10% and agree more closely with solar backscattered ultraviolet data at this altitude. The observed change in [NO2] during the night over a 5‐km altitude range implies either lower [NO2] postsunset profiles, or significantly faster [NO2] decay than current model predictions using N2O5 chemistry. Measurements of [NO], [NO2], [H2O], and [CO2] from an October 1985 flight are included for comparison.
Simulations of the HDO and H218O atmospheric cycles using the NASA GISS general circulation model: The seasonal cycle for present‐day conditions
Authors: Jouzel J. , Russell G. L. , Suozzo R. J. , Koster R. D. , White J. W. C. , Broecker W. S.
Published: February 2008

The cycles of the water isotopic species (HDO and H218O) have been incorporated into the NASA Goddard Institute for Space Studies (GISS) atmospheric general circulation model (GCM). The results of a 3‐year simulation for present‐day conditions are discussed, with special emphasis on the comparison between predicted and observed isotopic distributions (well documented mainly through the International Atomic Energy Agency/World Meteorological Organization network) for both the seasonal and annual time scales. The observed seasonal cycles are generally well simulated. For the annual scale the observed linear relationship between δ18O and the surface temperature at middle and high latitudes, as well as the absence of any correlation between these fields in tropical and equatorial regions, are properly obeyed by the GCM simulation. In the tropical and equatorial regions the δ18O patterns for both observations and the GCM are influenced by the amount of rainfall. There is excellent agreement between the simulated and observed δD–δ18O relationship throughout the world.
Solar ultraviolet irradiances on December 7, 1983, and December 10, 1984
Authors: Mentall James E. , Williams Donald E.
Published: February 2008

The full‐disk absolute solar irradiance was measured on December 7, 1983, and December 10, 1984. The first flight obtained data over the wavelength interval 150–260 nm, while the second obtained data from 150 to 340 nm. Absolute accuracy of the measurements varied from ±3 to ±9%, depending on the flight and the particular wavelength. Between 200 and 240 nm the results reported here are higher than previously reported irradiances, but there is good agreement over the other wavelength intervals. Near 150 nm the change in the solar flux between these two flights did not exceed 7%. Above 200 nm the change in the solar irradiance was not larger than the error bars of the measurement.
Turbulent transport observed just above the Amazon forest
Authors: Fitzjarrald David R. , Stormwind Brian L. , Fisch Gilberto , Cabral Osvaldo M. R.
Published: February 2008

We present observations of turbulent heat, moisture, and momentum transport made at two levels, approximately 5 and 10 m above the Amazon rain forest canopy. Data acquired at 10 Hz included variances and some mixed third moments of vertical velocity, temperature, and humidity. Two features of the data appear to question the displacement height hypothesis: (1) the characteristic dissipation length scale in the near‐canopy layer varied between 20 m in stable conditions to approximately 150 m during afternoon convective conditions, generally larger scales than would be expected, and (2) no appreciable differences in dissipation scales was seen at the two observed levels. Heat budgets on selected days show that frequent periods with negative heat flux concurrent with continuing positive moisture flux occur in early afternoon, and this is believed to indicate the patchy nature of canopy‐atmosphere coupling. Vertical velocity skewness was observed to be negative on 3 successive days and exhibited a sharp positive gradient. We present time series of some of the terms in the turbulence budgets of vertical velocity variance and kinematic heat flux.
Concentrations of carbonyl sulfide and hydrogen cyanide in the free upper troposphere and lower stratosphere deduced from ATMOS/Spacelab 3 infrared solar occultation spectra
Authors: Zander R. , Rinsland C. P. , Farmer C. B. , Namkung J. , Norton R. H. , Russell J. M.
Published: February 2008

Volume mixing ratio profiles of carbonyl sulfide (OCS) and hydrogen cyanide (HCN) have been deduced from the analysis of 0.01 cm−1 resolution infrared solar absorption spectra obtained with the ATMOS (Atmospheric Trace Molecule Spectroscopy) Fourier transform spectrometer, operating in the occultation mode on board Spacelab 3 on April 30 to May 1, 1985. The profiles of OCS have been retrieved from spectroscopic fittings of absorption lines observed between 2038 and 2061 cm−1 and identified as ν3 band transitions of OCS; they extend from 12 to 27 km altitude for sunset occultations near 28°N and from 18 to 26 km for two sunrises occurring at 46.8° and 49.0°S. The 28°N results agree satisfactorily with model calculations and with column density determinations by airplane above 12 km altitude. The investigation for HCN was based on the analysis of transitions belonging to both the ν3 fundamental and the 2ν2 bands of HCN, centered at 3311.48 and 1426.53 cm−1, respectively; the HCN profiles extend from 12 to 32 km for the 28°N latitude sunsets and from 13 to 30 km for sunrise events near 48°S. For both latitudes the mean results indicate a decrease of about 15±5% from the bottom to the top of their altitude span. The northern hemisphere retrievals reported here represent the first volume mixing ratio profiles covering the upper troposphere and the lower stratosphere simultaneously. The sunrise data provide first profiling of both species at southern mid‐latitudes.
Measurements of odd nitrogen compounds in the stratosphere by the ATMOS experiment on Spacelab 3
Authors: Russell J. M. , Farmer C. B. , Rinsland C. P. , Zander R. , Froidevaux L. , Toon G. C. , Gao B. , Shaw J. , Gunson M.
Published: February 2008

The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment, launched April 30, 1985, on Spacelab 3, measured vertical profiles at 30°N and 48°S of a host of reservoir gases, source gases, and other trace molecules important in the odd nitrogen, odd chlorine, and odd hydrogen chemical families of the middle atmosphere. The measurements included simultaneous observations of all the main elements of the NOy family (i.e., NO, NO2, HNO3, N2O5, HNO4, and ClONO2), thereby giving a direct measurement of the total odd nitrogen mixing ratio for the first time. Some of these species (N2O5, HNO4, ClONO2) represent first detections in the stratosphere, or confirmation of previously published tentative indentifications, and detailed discussion of each is not given here. The largest mixing ratios observed were ≈13±2.6 parts per billion by volume (ppbv) for [NO], 8.6±1.3 ppbv for [NO2], 7.7±2.1 ppbv for [HNO3], 1.6±0.8 ppbv for [N2O5], 0.35±0.14 ppbv for HNO4, and 1.4±0.7 ppbv for [ClONO2]. All of these peak values were found in northern hemisphere profiles, with the exception of HNO3 and the implied value for N2O5. The maximum total odd nitrogen mixing ratio of ≈17±2.6 ppbv occurred at 43 km (≈2 mbar) and 30°N. These results have important implications because of the key role [NOy] plays in buffering the odd chlorine depletion effect on ozone. The abundances of individual gases and total odd nitrogen levels measured by ATMOS have been compared with prior results obtained from balloon and satellite platforms. Since there are no prior [NOy] measurements, comparisons in this case were made with a lower‐limit profile obtained from the sum of measured nighttime [NO2 + HNO3] and derived N2O5, obtained from model calculations initialized using earlier satellite results. The lower‐limit profile agrees with ATMOS data to within 16% up to 42 km altitude. Two‐dimensional model calculations of [NOy] are as much as 40% larger than ATMOS values above 30 km and up to 40% less than the observations in the lower stratosphere.
Diurnal variation of nitric oxide at 32 km: Measurements and interpretation
Authors: Kondo Yutaka , Matthews W. Andrew , Aimedieu Patrick , Robbins Donald E.
Published: February 2008

On September 19–20 and October 4, 1985, in situ measurements of nitric oxide and ozone were carried out on board balloons launched from Aire sur l'Adour (44°N, 0°W) in France as a part of the Middle Atmosphere Program Global Budget of Stratospheric Trace Constituents NOx campaign. On September 19 a daytime NO profile from 6 to 33 km and the variation of NO in the afternoon at a float altitude of about 32 km were measured precisely. In the afternoon, when the solar zenith angle was between 48° and 70°, NO concentration was fairly stable, probably to within 10%. The slow decrease of NO near sunset at solar zenith angles larger than 80° was observed. A calculation assuming photochemical equilibrium between NO and NO2 has shown that the decay of NO toward sunset can be explained mainly by the decrease of the photodissociation rate of NO2 at large solar zenith angles. On October 4 the variation of NO at an altitude of about 33 km was measured for 2.5 hours after sunrise. Following the rapid buildup, which takes place for 30 min after visible sunrise, NO increases at a rate of approximately 1.2 parts per billion by volume (ppbv) per hour. From the rate of increase in NO in the morning, the N2O5 mixing ratio at sunrise at 33 km has been estimated to be 3.9±1.5 ppbv.
Determining microwave brightness temperatures from precipitating horizontally finite and vertically structured clouds
Authors: Kummerow C. , Weinman J. A.
Published: February 2008

Microwave radiances that may be measured from satellite‐borne radiometers operating at 37 GHz have been computed as a function of rainfall rates from horizontally finite precipitating clouds that contain both ice and liquid hydrometeors. It is found that precipitating ice at the top of the cloud depresses brightness temperatures significantly. Detailed comparison between finite clouds and the equivalent sections of plane‐parallel clouds are made. Footprint averaged brightness temperatures from finite clouds are found to deviate considerably from the sectioned plane‐parallel approximation, especially for large rain rates. Better agreement is achieved if a plane‐parallel source function is used in the finite cloud model. The effect of shape and orientation of the precipitating cells with respect to the satellite has also been considered. It is found that the largest errors introduced by plane‐parallel theory besides the footprint‐filling errors are encountered when precipitating cells have large fractions of their surface below the freezing level or contain large amounts of ice.
An intercomparison of mechanisms for the production of photochemical oxidants
Authors: Hough Adrian M.
Published: February 2008

Twenty different chemical mechanisms used in studies of the formation of photochemical oxidants have been compared. In order to concentrate on the differences in the hydrocarbon chemistry, these mechanisms were modified so that each contained the same inorganic processes and so that the rate coefficients for the hydrocarbon degradation reactions were the same in most cases. The mechanisms were all implemented in a model to study the formation of photochemical oxidants downwind of London during midsummer, clear‐sky, anticyclonic conditions. The same emissions inventory and meteorological parameters were used in each case. The mechanisms published since 1984 all produced similar results for ozone and nitric acid. The standard deviations of these concentrations were some 2–3 times greater when the whole set of results was considered. The concentrations of hydrogen peroxide and peroxyacylnitrates were much more variable, with concentrations varying by up to a factor of 2 for the recent mechanisms and with effectively no agreement over the whole set. This suggests that for these species, any agreement between observations and calculations which is within a factor of 2 is as good as can be expected and that model calculations cannot be verified to a greater degree of accuracy. The representation of hydrocarbon emissions in photochemical models and the ways in which large numbers of known atmospheric species are represented by a limited number of model variables clearly require further attention before confidence can be claimed in the model results for a wide range of photochemically generated secondary pollutants.
Simultaneous measurement of minor stratospheric constituents with emission far‐infrared spectroscopy
Authors: Carli Bruno , Park Jae H.
Published: February 2008

The vertical mixing ratio profiles of H2O, HDO, O3, heavy ozone, HF, HCl, HCN, and OH in the stratosphere are retrieved from high‐resolution far‐infrared emission spectra. These spectra were obtained with a balloon‐borne Fourier transform spectrometer in the spring of 1979 at 32°N. The nonlinear least squares fit method is used in the analysis. The results are obtained relative to the O2 mixing ratio, whose emission features can be found in the same spectra. The retrieval of OH together with other species should be particularly significant for the study of upper stratospheric photochemistry, although the errors are relatively large: 28% for OH and 16–19% for other species.
On the trigger of El Niño Southern Oscillation by the forcing of early El Chichón volcanic aerosols
Authors: Hirono Motokazu
Published: February 2008

After the volcanic eruption of El Chichon in 1982, the distribution of volcanic aerosols in the upper atmosphere was zonally very inhomogeneous for about a month or more and was located in a fairly uniform zonal band around the Earth in the northern subtropical region for the ensuing several months. The impact of those aerosols absorbing radiation on the atmospheric motion is discussed in the model of Gill (1980). It is shown that the mean westerly wind induced near the central Pacific equatorial region would be able to trigger or amplify the El Niño Southern Oscillation. Several observed results related to the simulation are discussed in some detail. The location of the initial center of most aerosols relative to the central Pacific is important in the model, and the impact of the forcing at the Agung event of 1963 is estimated to be smaller than that of the present event, which seems to agree with observed results.
Intercomparison of solar total irradiance data from recent spacecraft measurements
Authors: Mecherikunnel A. T. , Lee R. B. , Kyle H. L. , Major E. R.
Published: February 2008

Solar total irradiance data obtained by the solar monitors of the Earth Radiation Budget Experiment (ERBE) on board the Earth Radiation Budget Satellite (ERBS) and on the National Oceanic and Atmospheric Administration spacecraft NOAA 9 and NOAA 10 are compared with the solar total irradiance data obtained from the Solar Maximum Mission (SMM) Active Cavity Radiometer Irradiance Monitor 1 (ACRIM 1), the sounding rockets, and the Nimbus 7 Earth radiation budget (ERB) channel 10 C. For the first 2 years of solar total irradiance measurements in space, the ERBE solar monitors on board ERBS and NOAA 9 spacecraft yielded the same mean irradiance value of 1364.9 W m−2 for the solar constant. This value is 0.2% lower than the mean value of the solar constant derived from the SMM ACRIM 1 and the sounding rockets, and it is 0.4% lower than the Nimbus 7 ERB measurements. For the first 6 months of solar irradiance, data available from the ERBE solar monitor on board NOAA 10 spacecraft yielded a mean value of 1363.2 W m−2 for the solar constant. The current solar monitoring and ERB measurement programs have yielded solar total irradiance data of high accuracy and precision. The disparity between the solar total irradiance values obtained in near‐simultaneous measurements with absolute pyrheliometers of similar design and mode of operation is an indication of the uncertainty associated with absolute pyrheliometers available at present. This disparity points out the need for intercalibration of electrically self‐calibrating pyrheliometers from spacecraft to derive an absolute pyrheliometric scale, valid for solar total irradiance measurements from space.
Solar heating of water bodies as influenced by their inherent optical properties
Authors: Kirk John T. O.
Published: February 2008

A simple one‐dimensional model has been developed for calculating the development of thermal structure in water bodies under specified meteorological conditions, as a function of their inherent optical properties (spectral absorption coefficients, scattering coefficient). Penetration of radiant solar energy is modeled with a previously derived equation relating attenuation of irradiance in narrow wavebands to absorption coefficient, scattering coefficient and solar angle. Evaporative and other heat exchange processes at the surface are taken into account. Vertical heat transfer is calculated by making use of a recently published parameterization of the eddy diffusion coefficient. The calculations show marked changes in thermal structure as absorption and scattering are varied over a range of optical water types from coastal seawater to highly colored and turbid inland water. In general terms, increasing the color and/or turbidity shifts the zone of shortwave energy absorption more toward the surface and leads to warmer but shallower mixed layers.
Response of electrons to a gravity wave in the upper mesosphere
Authors: Sugiyama T.
Published: February 2008

Effects of a gravity wave on the electron concentration in the upper mesosphere including the temperature effects of the wave on chemical reaction rates, are studied analytically. To reproduce the ledge of the D region, a simple working model of the fast formation of H+(H2O)n is presented, in which NO+(H2O)2 in some excited state is hypothesized to be exothermically converted to H+(H2O)2. Using the model, we show that a wave, with periods longer than 2 hours, interacts remarkably with the ledge of the D region, where the amplitude of electron response reaches a level about 20 times as large as the response of the neutral density. The modulated ledge moves, with the propagation of the wave, gradually downward, while being replaced by a new ledge from above. The general agreement of the obtained results and observations suggests that the thermal decomposition of NO+ H2O · N2 has an important role in controlling the compositions of positive ion species and thereby the structures of electron profiles in the upper mesosphere. It is stressed that the irregular profiles of electrons observed in the upper mesosphere are caused, to a considerable extent, by the effects of gravity waves.
Heterogeneous processes in the Po Valley radiation fog
Authors: Fuzzi Sandro , Orsi Giordano , Nardini Giorgio , Facchini Maria Cristina , McLaren Scott , McLaren Eugene , Mariotti Mauro
Published: February 2008

The heterogeneous processes responsible for fog water chemical composition are examined in this paper. SO2/SO4= and NOx/HNO3/NO3− systems have been particularly investigated for their role in the production of acidity within the dispersed liquid phase. A program is presented, involving several European and American institutes, which has thus far provided the following main results: (1) nucleation scavenging represents a major source of sulphate in fog, but a potential also exists for SO2 conversion in the liquid phase; (2) excess nitrate which was found in fog, with respect to the prefog aerosol concentration, appears to derive from gas phase HNO3 incorporation into the droplets. Chemical processes seem to be active at the stage of fog formation, with microphysical condensation/evaporation/deposition/entrainment processes being primarily responsible for changes in the chemical composition of the system during fog evolution. Additional and improved data requirements indicated by our results are discussed.
Possible contribution of N2O5 scavenging to HNO3 observed in winter stratiform cloud
Authors: Leaitch W. R. , Bottenheim J. W. , Strapp J. W.
Published: February 2008

During a winter field study in early 1984, the concentrations of NO3−, SO4=, and H+, measured in cloud water samples collected in the bases of deep stratiform clouds and in the aerosol and gas phases below cloud, suggested a substantial enhancement of NO3− in the cloud water samples for 8 of 12 days. For these 8 days, variations in cloud water NO3−/SO4= were associated with an excess H+/SO4= in the cloud water, indicating HNO3. For the conditions of study, which included subfreezing temperatures and weak solar fluxes to the low‐level cloud, the possibility exists that much of the NO3− in the cloud water was from the formation and subsequent scavenging of N2O5 by cloud droplets. A chemical model set in a Lagrangian framework is used to describe the daytime evolution of odd nitrogen species, including dry deposition of HNO3, under conditions approximating the average conditions for the 8 days. Computations with no cloud scavenging of N2O5 predict an average cloud water NO3− mixing ratio well below the geometric mean determined for the measurements. For the conditions most typical of the observations, the production rate of HNO3 via the cloud scavenging of N2O5 was computed to be approximately equal to that for the gas‐phase production of HNO3.
Infrared measurements of atmospheric gases above Mauna Loa, Hawaii, in February 1987
Authors: Rinsland C. P. , Goldman A. , Murcray F. J. , Murcray F. H. , Blatherwick R. D. , Murcray D. G.
Published: February 2008

Infrared solar absorption spectra recorded at 0.02 cm−1 resolution from the National Oceanic and Atmospheric Administration (NOAA) Geophysical Monitoring for Climate Change (GMCC) program station at Mauna Loa, Hawaii (latitude 19.5°N, longitude 155.6°W, elevation 3.40 km), in February 1987 have been analyzed to determine simultaneous total vertical column amounts for 13 atmospheric gases. Average tropospheric concentrations of CO2, N2O, CH4, and CHClF2 and the daytime diurnal variations of the total columns of NO and NO2 have also been inferred. The retrieved total columns (in molecules cm−2) of the nondiurnally varying gases are 1.6±0.2×1015 for HCl, 5.9±1.2 ×1015 for HNO3, 2.0±0.2×1021 for H216O, 4.4±0.7×1018 for H218O, 2.7±0.1×1017 for HDO, 2.3±0.2×1019 for CH4, 5.0±0.5×1021 for CO2, 6.7±0.8×1018 for O3, 4.3±0.4×1018 for N2O, 1.0±0.2×1016 for C2H6, and 9.7±2.5×1014 for CHClF2. We compare the total column measurements of HCl and HNO3 with previously reported ground‐based, aircraft, and satellite measurements. The results for HCl are of particular interest because of the expected temporal increase in the concentration of this gas in the stratosphere. However, systematic differences among stratospheric HCl total column measurements from 1978 to 1980 and the absence of observations of free tropospheric HCl above Mauna Loa make it impossible to obtain a reliable estimate of the trend in the total burden of HCl. The measured HNO3 total column is consistent with aircraft measurements from ∼12 km altitude. The O3 total column deduced from the IR spectra agrees with correlative Mauna Loa Umkehr measurements within the estimated error limits. The column‐averaged D/H ratio of water vapor is (68±9)×10−6, which is 0.44±0.06 times the reference value of 155.76×10−6 for standard mean ocean water (SMOW). This large depletion in the D content of water vapor is similar to published measurements of the upper troposphere and lower stratosphere. Average tropospheric concentrations deduced for CO2, N2O, and CH4 are in good agreement with correlative NOAA GMCC surface data, indicating consistency between the measurement techniques for determining tropospheric volume mixing ratios. Results of the present study indicate that Mauna Loa is a favorable site for infrared monitoring of atmospheric gases. The site is particularly favorable for monitoring the tropospheric volume mixing ratios of long‐lived gases, since the high altitude of the tropopause reduces corrections required to account for the decrease in volume mixing ratio in the stratosphere.
Measurements of selected C2–C5 hydrocarbons in the troposphere: Latitudinal, vertical, and temporal variations
Authors: Singh Hanwant B. , Viezee William , Salas Louis J.
Published: February 2008

Results are presented on the tropospheric distribution of C2–C5 hydrocarbons based on (1) shipboard measurements over the eastern Pacific Ocean from latitude 47°N to 47°S, (2) ground‐based measurements at a remote coastal site in northern California (39°N), and (3) airborne studies of the troposphere over Colorado and over the eastern Pacific Ocean (38°N) during the summer and winter seasons. A total of 1077 hydrocarbon samples were processed during these comprehensive field programs. In agreement with previous studies, the shipboard measurements show large north‐to‐south gradients for virtually all nonmethane hydrocarbons (NMHCs) and clearly indicate their northern hemispheric sources. Ethane, the most abundant NMHC, is present at a concentration of 2 ppb in the northern hemisphere (NH) mid‐latitudes, with southern hemisphere (SH) concentrations of about 0.3 ppb. All other NMHC concentrations are in the sub‐ppb range. The measurements at the remote coastal site of Point Arena, California, show that NMHC concentrations can decrease by a factor of 2 or more during the passage of cold fronts in winter and spring. During these events the behavior of NMHCs is strongly correlated with primary anthropogenic species (e.g., CH2Cl2, CH2ClCH2Cl, and CH3CCl3) as well as secondary oxygenates (e.g., peroxyacetyl nitrate (PAN) and ozone). Aircraft measurements of NMHC concentrations made over Colorado and near the coastal zone of northern California were higher over land than over the ocean in the lower troposphere (<5 km). Upper tropospheric concentrations were found to be lower and, in general, much less spatially variable than those present in the lower troposphere. Because of the differences in NMHC concentrations between ocean and land and between lower and upper troposphere evident in the measurements, it is possible that weather systems associated with significant horizontal and vertical transport can cause large temporal and spatial variations in NMHC concentrations on local and regional scales.