bluuebunny/crossref_metadata_2025 huggingface dataset:
measurements of some stratospheric ion‐molecule association rates: Implications for ion chemistry and derived HNO3 concentrations in the stratosphere
Authors: Viggiano A. A. , Dale F. , Paulson J. F.
Published: February 2008

Three‐body association rate coefficients have been measured as a function of temperature for the clustering of HCl to HSO4−(H2SO4)m(HNO3)n ions for m = 0–3 and n = 0 and 1. The temperature coefficients of these clustering reactions were found to increase with increasing cluster size in agreement with studies on other systems. A total of three ligands was found to bond strongly to HSO4−. We also measured the rate coefficients for NO3− clustering to HNO3 as a function of pressure. This rate was found to saturate at a value of 2.6×10−10 cm3 s−1 at a pressure of about 0.3 torr. The data were used to check the identities of some of the ions observed in the stratosphere and to predict the abundances of other ions that have not yet been observed. HNO3 concentrations derived from in situ ion composition measurements have been corrected to account for the saturation of the rate coefficient at a value less than 10−9 cm3 s−1. The corrected concentrations do not change much at 34 km but increase by a factor of almost 2 at 40.8 km. This result is in better agreement with model calculations.
The application of potential flow theory to the rotational dynamics of spheroids, disks, and cylinders
Authors: Weinheimer Andrew J. , Few Arthur A.
Published: February 2008

The purpose of this work is to obtain estimates of the torque exerted by a fluid on a translating object and also of the frequency of the rotational oscillation that results from this torque. The approach employed is to assume spheroidal geometry for the translating objects and to assume that the flow around these spheroids may be approximated by potential flow. Potential flow torques and oscillation frequencies for prolate and oblate spheroids are computed and compared to measured values for spheroids, disks, and cylinders found in the literature. The results of this comparison lie in four areas. First, it is found that potential flow torques are consistently larger than measured torques, and the reason for this is discussed. Second, and as a corollary, it is found that potential flow oscillation frequencies are also greater than measured frequencies. Third, it is suggested that the observed oscillation frequencies are determined by the nearly potential flow on the objects' upstream sides rather than by the natural frequency of vortex shedding, as suggested by the remarks of some authors. Fourth, the tumbling, or autorotation, that is observed to occur for some solids while translating through fluids is examined in light of these results. In particular the possibility is considered that the tumbling results from a resonance between periodic conditions in the wake of an object and a natural frequency of oscillation that is characteristic of the object and the nearly potential flow on its upstream side.
Ice flow at the Dome C ice divide based on a deep temperature profile
Authors: Bolzan John F.
Published: February 2008

We calculate the temperature distribution with depth at the Dome C ice divide, East Antarctica, for a number of vertical strain rate functions; assuming two‐dimensional flow. To solve the heat equation, we use the Dome C oxygen isotope profile and radar data to specify the surface and basal boundary conditions, respectively. Two different sets of simple, monotonie polynomials are used as strain rate test functions. For a net surface warming of about 9°C through the Wisconsinan‐Holocene climatic transition, we find that the best agreement to the measured 800‐m Dome C temperature profile results from a vertical strain rate of the form (1 ‐ z/H)p, with H the ice thickness and p≃2.5. Using dated horizons in the oxygen isotope profile obtained by cross correlation with a marine sediment core, we find virtually no change in accumulation rate at Dome C since the end of the Wisconsinan glacial.
An airborne lidar instrument for detection of OH using the technique of laser‐induced fluorescence
Authors: Davis L. I. , Guo Chuan , James John V. , Morris Peter T. , Postiff R. , Wang Charles C.
Published: February 2008

This paper describes an airborne lidar instrument for detecting OH, using the technique of laser‐induced fluorescence. The detection limit is determined mainly by the shot noise of the solar background. For daytime measurements at 6100 m (20,000‐ft) a detection limit of about 1×106 OH/cm3 was obtained with a 2‐hour acquisition time under favorable conditions.
Nitric oxide measurements at a nonurban eastern United States site: Wallops instrument results from July 1983 GTE/CITE mission
Authors: Torres Arnold L.
Published: February 2008

The NASA Goddard Space Flight Center/Wallops Flight Facility nitric oxide detector used in the July 1983 GTE/CITE 1 instrument intercomparison is a chemiluminescence system which, at that time, had a detection limit of about 2 pptv (S/N = 1) for 60‐s integrations. A substantial amount of NO concentration data was taken with this system at Wallops Island, Virginia, a site that should be typical of numerous nonurban coastal areas of the eastern United States and for which little other data are available. Midday concentrations under conditions of northwest winds averaged about 200 pptv, a value low enough to imply lower NOx amounts than are generally thought to exist in the eastern United States. During a 2‐day period when the sampled air had spent 1–2 days over the Atlantic Ocean, average NO concentrations of 70 and 33 pptv were observed. Measurements at night indicated an average NO concentration of 16 pptv under wind conditions making contamination of the sampled air by local anthropogenic sources unlikely.
Kinetics of aqueous‐phase oxidation of nitrogen(III) by hydrogen peroxide
Authors: Lee Yin‐Nan , Lind John A.
Published: February 2008

The kinetics of the aqueous‐phase oxidation of nitrous acid by hydrogen peroxide in the micromolar concentration range has been investigated over the pH range 1.8–3.1. The reaction yields nitric acid according to the stoichiometry: H2O2 + HNO2 → H+ + NO3− + H2O. The experimentally derived rate law is given by −d[H2O2]/dt = d[NO3−]/dt = k[H+][HNO2][H2O2], with k determined as (6.3 ± 1.5) × 103 M−2 s−1 at 25.1 ± 0.1°C and zero ionic strength. The enthalpy of activation determined over the temperature range 10°–35°C at pH 2.07 and 0.08 M ionic strength is 13.3 ± 0.3 kcal/mol. The results obtained here are in fairly good agreement with those of earlier studies, despite large differences in the reagent concentrations employed (3 to 5 orders of magnitude). The contribution of this reaction to atmospheric formation of aqueous‐phase NO3− and depletion of gas‐phase HNO2 is found to be insignificant for representative atmospheric conditions; however, oxidation of N(III) by H2O2 in collected precipitation samples may be appreciable on a time scale of hours to a few days.
Response of CIGRE and CCIR lightning flash counters to the electric field changes from lightning: A theoretical study
Authors: Cooray Vernon
Published: February 2008

Recent information concerning the electric field changes from lightning flashes have been employed to study the response of Conférence Internationale des Grandes Réseaux Electriques (CIGRE) and International Radio Consultative Committee (CCIR) lightning flash counters. This study led to the following conclusions: (1) The CIGRE 10‐kHz counter operates on the radiation field of the return strokes, and the effective range of this counter is about 20 km. (2) The CCIR counter is similar to the CIGRE 10‐kHz counter, except for its high sensitivity and the ability to react to radiation pulses of both polarities. The effective range of this counter is estimated to be about 140 km. (3) The effective range of the CIGRE 500‐Hz counter is about 30 km. (4) A better discrimination between cloud and ground flashes can be achieved by raising the center frequency and low‐frequency response of the CIGRE 10‐kHz counter, while keeping the upper frequency response the same. The response to ground flashes remains approximately the same after the modification.
Unimolecular decomposition of NO3 to form NO and O2 and a review of N2O5/NO3 kinetics
Authors: Johnston H. S. , Cantrell C. A. , Calvert J. G.
Published: February 2008

The nitrate free radical NO3 has been observed by several investigators in the troposphere at night. It increases during the night much less than predicted in terms of known processes, and there has been a search for an unknown NO3 scavenger. In this article we report evidence in the chemical literature for the thermal decomposition of NO3 to form nitric oxide and molecular oxygen, where the reaction w is NO3 → NO + O2, and the rate is such that this reaction is proposed as a scavenging process in the troposphere. By straightforward reinterpretation of three room temperature kinetic studies which used reactors of widely different volumes, we find the first‐order rate constant at one atmosphere pressure to be w = (3 ± 2) × 10−3 s−1; in these systems the otherwise unexplained first‐order loss of NO3 accounted for 5–74% of the observed rate. Using high‐temperature shock tube experiments, Schott and Davidson [1958] evaluated rate constants for reaction e (NO2 + NO3 → NO + O2 + NO2) and reaction g (2NO3 → 2NO2 + O2), but these values are much higher than the extrapolated results of Graham and Johnston [1978]. This difference is ascribed to the unrecognized contribution of reaction w in Schott and Davidson's system; with this assumption we evaluated by two methods the rate constants for w at high temperatures, which combine with the room temperature values to give the Arrhenius expression w = 2.5 × 106 exp (−6.1 × 103/T) s−1. This relation implies that the unimolecular reaction has a low frequency factor and a low activation energy, which are ascribed to a forbidden transition to the low‐lying excited electronic state (2E2″) of NO3. The rate of this channel of decomposition is compared with the much slower process leading to NO2 and O as products. Although this article gives evidence that the reaction NO3 → NO + O2 occurs, the quantitative values of rate coefficients are uncertain, and there are no data concerning the effect of foreign gas pressure. This article points out two methods (equations (14) and (17)) whereby deliberate studies of this reaction can be used to establish its rate coefficients and to find its M gas dependence. The recommended rate expression for reaction e is 2.05 × 1013 exp (−1.24 × 104/T)/Keq and that for g is 8.5 × 10−13 exp (−2.45 × 103/T) cm3 molecule−1 s−1, where Keq refers to the equilibrium N2O5 = NO3 + NO2.
Modeling seasonal changes of atmospheric carbon dioxide and carbon 13
Authors: Gillette Dale A. , Box Elgene O.
Published: February 2008

A two‐dimensional (latitude‐altitude) model of atmospheric CO2 and δ13C was constructed to simulate some features of seasonal carbon cycle fluctuations. The model simulates air‐sea exchange, atmospheric diffusion, and fossil fuel carbon sources, which are functions of time and latitude. In addition, it uses biosphere‐atmosphere fluxes of carbon that are based on global‐scale biological models of vegetation growth and decay. Results of the model show fair agreement with observational results for CO2 and δ13C seasonal fluctuations. Our model results have far northern fluctuations with smaller amplitudes than are observed. Analysis of sources of CO2 change at given latitudes shows that, for far southern latitudes, southern hemisphere biospheric fluxes are dominant in affecting the seasonal CO2 fluctuations. Long‐term decrease of δ13C for the model is larger than for observations. This may be due to errors in the formulation for oceanic fluxes for 13C in the model or to a net uptake of carbon by the biosphere.
Simultaneous in situ measurements of nitrogen dioxide, nitric oxide, and ozone between 20 and 31 km
Authors: McFarland M. , Ridley B. A. , Proffitt M. H. , Albritton D. L. , Thompson T. L. , Harrop W. J. , Winkler R. H. , Schmeltekopf A. L.
Published: February 2008

Simultaneous in situ measurements of NO, NO2, O3, and temperature were made from approximately 20 to 31 km in the stratosphere during July, August, and November. Two of the balloon flights were made from Palestine, Texas (32°N), the third from Gimli, Manitoba (50°N). NO was detected using the chemiluminescence technique; NO2 was photolyzed to NO prior to detection. Both the NO and NO2 mixing ratios are in good agreement with most other measurements in this altitude region. To within the combined uncertainties the measured NO2 to NO ratios agree with those calculated assuming photochemical steady state. There is, however, a tendency for the observed ratio to be larger than the calculated ratio at low altitudes near 32°N, but not at 50°N. Refinements to the experiment will be required to elucidate unequivocal discrepancies. From the observation of a temporal increase in the sum of NO and NO2 while at constant altitude, it is possible to infer the abundance of N2O5 near noon. Further, a lower‐limit estimate of the total odd nitrogen mixing ratio of 16–19 parts per billion by volume near 30 km is made using the observations of NOx, the estimated N2O5 mixing ratio, and previous measurements of HNO3.
A simple bidirectional reflectance model for terrestrial surfaces
Authors: Pinty B. , Ramond D.
Published: February 2008

A simple bidirectional reflectance model is derived for terrestrial surfaces. This model uses photometric relationships together with data from the Nimbus 7 Earth Radiation Budget (ERB) Experiment. It is shown that the model provides a good description of bidirectional patterns derived from satellite observations for two classes of broad uniform surfaces, namely, land and desert. Dependency of the derived albedo model on solar zenith angle is also studied and compared with several observations made at the surface of the earth. Despite the simplicity of the approach the proposed bidirectional reflectance model might be useful for several applications in satellite remote sensing.
Northern hemisphere kinetic energy during the first GARP global experiment year
Authors: Zautner Jeffrey H. , Whittaker Linda M. , Horn Lyle H.
Published: February 2008

A comparison of the monthly vertically integrated northern hemisphere kinetic energy (in the isentropic domain) during the First GARP (Global Atmospheric Research Program) Global Experiment (FGGE) year with 5‐year monthly means (isobaric domain) shows only small seasonal differences, which are probably related to the different domains. Ratios of monthly total kinetic energy to available potential energy yield similar results. Daily values of the zonal and eddy kinetic energy indicate that the first part of the FGGE year differed considerably from a 5‐year mean in that the zonal kinetic energy was as large as the eddy component. Seasonal maps of the kinetic energy show anomalous winter and spring distributions, with the Atlantic and Pacific maxima equal in winter but with a near disappearance of the Atlantic maximum in spring. Similar differences are noted in cyclone activity. The transient kinetic energy plotted as a function of month and latitude appears to fit the normal pattern, but here longitudinal differences are obscured.
Temperature dependence of the NO3 cross section in the 662‐nm region
Authors: Ravishankara A. R. , Mauldin R. L.
Published: February 2008

The absorption cross section of NO3 free radical has been measured in the wavelength region of 652.5–672.5 nm at three temperatures (220, 240, and 298 K). A discharge flow apparatus was used to prepare NO3 via the F + HNO3 → HF + NO3 reaction, and a long‐path continuous wave laser absorption cell, coupled to the flow tube, was used to measure the absorbance. The absolute concentration of NO3 in the absorption cell was determined by titration with NO. It was found that the absorption cross section at 662 nm (the peak of the band) increased with decrease in temperature, while the shape of the band itself did not change. These results are compared with those from other studies. The implication of this finding to NO3 measurement using absorption techniques is discussed.
Changes in precipitation chemistry at Dye 3, Greenland
Authors: Finkel R. C. , Langway C. C. , Clausen H. B.
Published: February 2008

Measurements of the chemical composition (Cl−, NO3−, SO42−, and H+) of ice core samples from Dye 3, Greenland, show recent increases in the concentration of nitrate and sulfate which can be attributed to anthropogenic sources. These anthropogenic sources have changed not only the magnitude of impurity levels in Greenland snow but also the seasonal pattern of impurity concentration. The observed change in seasonal deposition patterns between preindustrial and industrial times is used to analyze the sources of both natural and anthropogenic impurities in Greenland.
Kinetics of the OH + CO reaction under atmospheric conditions
Authors: Hynes A. J. , Wine P. H. , Ravishankara A. R.
Published: February 2008

The pulsed laser photolysis‐pulsed laser‐induced fluorescence technique has been employed to study the kinetics of the reaction, OH + CO → k1 products, as a function of temperature and pressure in N2, air, and O2 buffer gases. At pressures of 1 atm and below, k1 is found to increase linearly with increasing pressure. Within experimental uncertainty, both the rate constant in the low‐pressure limit and the slope of the k1 versus pressure dependence are found to be the same at 262 K as at 299 K. From our data we obtain the expression k1 = (1.47 ± 0.08) × 10−13 [1 + (0.59 ± 0.10)P] independent of temperature, where P is in units of atmospheres and k1 is in units of cubic centimeters per molecule per second. Within experimental uncertainty, the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. In 700‐torr air at 299 K, k1 is found to be independent of water vapor concentration over the range 0.01–20 torr. Our results will have little effect on current panel recommendations of k1 values for use in atmospheric models. However, uncertainties in the temperature dependence under atmospheric conditions, the third body efficiency of O2, and the effect of water vapor on k1 are now greatly reduced.
Characteristics of the Yala Glacier from the viewpoint of tritium content
Authors: Kamiyama Kokichi , Kitaoka Koichi , Watanabe Okitsugu
Published: February 2008

The vertical distributions of tritium content in glacier ice were determined at two different heights of the Yala Glacier in the Langtang Region, Nepal Himalayas. In the vertical profile of tritium content at the upper point (about 5,400 m high) there exists a clear peak, which shows the injection of artificial tritium due to nuclear weapon test series. The average accumulation rate from 1963 to 1982 at this point is estimated to be 0.85 m of water equivalent per year. At the lower point (about 5,200 m high) the tritium content is relatively low throughout the ice core, decreasing with depth. Precipitation nourishes the glacier in the accumulation area, and, after a long time, it appears in the ablation area with the movement of the ice body, resulting in the different profiles of the tritium content between the two points. From the viewpoint of tritium content, the precipitation in the Yala Glacier is more similar to that in New Delhi, India, than that in Karizimir, Afghanistan. Generally speaking, the tritium content in the precipitation is lower in the coastal area than in the continental area. The precipitation in the Yala Glacier belongs to the coastal type. There possibly exists a great difference in tritium content between the glaciers nourished by water vapor coming directly from the sea and by that coming over the continent.
Radiation measurements and model results from R/V Oceanographer during STREX 1980
Authors: Lind Richard J. , Katsaros Kristina B.
Published: February 2008

Measurements of shortwave and long‐wave irradiance were made from the NOAA ship R/V Oceanographer during the Storm Transfer and Response Experiment (STREX) near 50°N, 140°W during the autumn of 1980. Long‐wave exitance was calculated from observed sea surface temperature. Shortwave exitance and albedo were calculated from smoothed observations of R. E. Payne relating albedo to solar zenith angle and shortwave transmittance. Daily net radiation balances ranged from +9.3 to −43.3 W m−2. A model of shortwave irradiance adapted from F. E. Lumb gave results to within 10 W m−2, averaged over most 5‐day periods. An abridged form of a long‐wave irradiance model, developed by the authors, was compared to measurements. This model was found to have similar accuracies when applied to data from STREX and when applied to data from the 1978 Joint Air‐Sea Interaction (JASIN) Experiment.
Lagrangian time scales connected with clouds and precipitation
Authors: Hamrud Mats , Rodhe Henning
Published: February 2008

An attempt is made to estimate Lagrangian time scales connected with clouds in the atmosphere. Three‐dimensional wind and relative humidity obtained from the First GARP Global Experiment (FGGE) data set are used to compute three‐dimensional trajectories with accompanying clouds. From the meteorological history of the trajectories, estimates are made of the average time from the release of a trajectory until the first cloud passage and the average time between first and second cloud passage. Geographical and seasonal variations of these parameters are calculated and discussed. Since the “clouds” parameterized from the FGGE data are limited to those connected with the large‐scale flow in the atmosphere, a substantial bias in our estimates is introduced. This implies that the estimates are more representative for major cloud systems, often connected with precipitation, than for clouds in general.
An improved rocket ozonesonde (ROCOZ‐A): 2. Preparation of stratospheric ozone profiles
Authors: Barnes Robert A. , Holland Alfred C. , Lee H. S.
Published: February 2008

The ROCOZ‐A radiometer measures ozone by long pathlength photometry in the stratosphere and lower mesosphere. After a rocket launch to an apogee of 70 km, the instrument measures the solar ultraviolet irradiance over its four filter wavelengths as it descends on a parachute. The fundamental values from ROCOZ‐A are ozone overburdens versus radar altitude from 53 to 20 km. The slope of these values gives ozone number density. At one standard deviation the repeatability of the ozone overburden measurements averages 2.4%. For ozone number density the repeatability averages 3.2% with a significant increase at altitudes below the ozone number density maximum. The accuracy limits for overburden and number density are estimated at 5–7%. With auxiliary measurements of pressure and temperature, ozone results are also produced in terms of ozone mixing ratio, albeit with a slight broadening of the estimated accuracy limits. The vertical response of ROCOZ‐A ozone measurements (full width at half maximum) is 4 km. The assembly of ROCOZ‐A profiles can be used to compare with measurements from each of the current NASA and NOAA satellite ozone instruments. In addition, the repeatability of ROCOZ‐A allows the use of this instrument as a transfer standard between satellite instruments with different fundamental ozone measurements.
Ratio of calcium plage to sunspot areas of solar active regions
Authors: Lawrence J. K.
Published: February 2008

Published sunspot and calcium plage areas were examined for about 1,700 solar active regions (ARs) between 1971 and 1982. With these data, averaged AR properties, the possibility of energy balance between spot and facular emission over the lifetimes of activity complexes, and changes in AR properties over an 11‐year sunspot cycle were studied. Overall energy balance can neither be established nor ruled out. Apparently, real temporal changes in the nature of ARs, however, imply either that energy balance cannot hold over periods shorter than a few years or that standard models for estimating irradiance fluctuations from spot and/or plage areas must be modified.
An intercomparison of nitrogen‐containing species in Nimbus 7 LIMS and SAMS data
Authors: Jackman Charles H. , Guthrie Paul D. , Kaye Jack A.
Published: February 2008

Nitrogen dioxide (NO2) and nitric acid (HNO3) distributions were derived with a two‐dimensional time‐dependent model using N2O, CH4, and temperature measurements from the stratospheric and mesospheric sounder (SAMS) along with H2O measurements from the limb infrared monitor of the stratosphere (LIMS) and O3 measurements from the solar backscatter ultraviolet (SBUV) instrument. All three instruments (SAMS, LIMS, and SBUV) were aboard the Nimbus 7 satellite. The computed NO2 and HNO3 were compared with LIMS NO2 and HNO3 measurements. Calculated NO2 is lower than the LIMS NO2 in much of the lower stratosphere by about a factor of 4 or more. Differences in the upper stratosphere between derived NO2 and LIMS NO2 are within the photochemical uncertainties of the computation. Derived NO2 is much larger than LIMS NO2 at high latitudes in the upper stratosphere in December, indicating that dynamics and/or photochemistry in the atmosphere are different from those used in the model. Derived HNO3 is in fairly good agreement with LIMS HNO3 in the upper stratosphere. Derived and LIMS HNO3 gradually become more different through the middle stratosphere and reach a fairly substantial disagreement in the lower stratosphere. The high‐latitude maxima observed in LIMS HNO3 are present at lower altitudes and at higher concentrations than those derived in the model computations. More significantly, the derived HNO3 at polar latitudes is highest in the summer while LIMS HNO3 is highest in the winter. Disagreements in the lower stratosphere between the computed and LIMS NO2 and HNO3 can only be reduced if two changes are made in the model computations: (1) additional lower stratospheric sources of odd nitrogen (other than N2O + O(1D)) are included and (2) a modified chemistry to allow the formation of HNO3 at the expense of N2O5 is used.
The kinetics of the reaction of OH With COS
Authors: Wahner Andreas , Ravishankara A. R.
Published: February 2008

The laser/flash‐photolysis laser‐induced fluorescence technique was employed to study the reaction of OH with carbonyl sulfide (COS) in various buffer gases (He, N2, and SF6). In order to determine the relevance of this reaction to tropospheric chemistry the influence of O2 on the rate constant was investigated. To avoid secondary reactions, especially the photolysis of COS, different photolytic OH precursors (H2O2, HNO3, and HONO) with different photolysis light sources (Xe flash lamp, ArF laser, fourth‐harmonic Nd: YAG laser, XeF laser, and third‐harmonic Nd: YAG laser) were used. The rate constant (1.92±0.25)×10−15 cm3 s−1 for the reaction of OH with COS at room temperature was found (after correcting for H2S impurity) to be independent of the pressure and the buffer gas. Addition of O2 was found to have no influence on the measured rate constant. Certain experiments were carried out at 298 K and 245 K to ascertain the mechanism for this reaction. Our results suggest that the degradation pathway involving homogeneous gas phase reaction of COS with OH is of minor importance in the troposphere.
Modeling of the stratospheric background aerosols from zonally averaged SAGE profiles
Authors: Brogniez C. , Lenoble J.
Published: February 2008

The SAGE (Stratospheric Aerosol and Gas Experiment) satellite aerosol extinction profiles at 1.0 and 0.45 μm, averaged over 10° latitude bands, are used to derive a description of the background stratosphere, which is compared to the Standard Radiation Atmosphere model. At middle and high latitudes a small seasonal variation appears, with larger particles and higher optical depths in winter.
Seasonal and diurnal variability of nitric acid vapor and ionic aerosol species in the remote free troposphere at Mauna Loa, Hawaii
Authors: Galasyn James F. , Tschudy Kristie L. , Huebert Barry J.
Published: February 2008

Measurements of nitric acid vapor and aerosol nitrate, sulfate, and ammonium were made at the Mauna Loa Observatory on Hawaii between October of 1984 and January of 1986 during 10‐day periods every 2 months. Nitric acid exhibited both a diurnal cycle (higher concentrations during the upslope wind hours of 0900 to 2100 LT) and a seasonal modulation (highest concentrations during the late summer). In August the daytime/nighttime average HNO3 concentrations were 97/79 parts per trillion by volume (pptv), while in February they were only 18/8 pptv. The ratio of summer/winter average HNO3 concentrations was 8. Dry deposition at the surface may be a major factor causing the diurnal variation, causing the measured surface values to be lower than the concentrations in the free troposphere above the surface. The long‐range transport of anthropogenic odd nitrogen from the west coast of North America is a likely cause of the higher summertime nitric acid concentrations. This suggests that there may be regular periods during which apparently “short‐lived” anthropogenic trace gases may be transported to remote parts of the atmosphere with relatively high efficiency. Aerosol NO3−, SO42−, and NH4+ also showed seasonal variations: summer/winter ratios were 3, 2, and 0.5, respectively.
Simulations of the GOES visible sensor to changing surface and atmospheric conditions
Authors: Pinker R. T. , Ewing J. A.
Published: February 2008

Numerical experiments have been conducted to simulate the GOES Visible and Infrared Spin Scan Radiometer (VISSR) visible sensor's response under varying surface and atmospheric conditions, as a function of solar zenith angle. The possible bias in the information obtained with this limited spectral response sensor was assessed by comparing the narrow‐band filtered clear‐sky planetary albedo, as observable with the VISSR, with the broadband (0.3–2.5 μm) unfiltered planetary albedo under the same environmental conditions. Four cases of wavelength‐dependent surface albedo (snow, meadow, dry sand, and water) and three atmospheric conditions have been simulated. It was demonstrated that the relationship between the filtered and the broadband planetary albedo depends primarily on the assumptions made about the magnitude and wavelength dependence of the surface albedo and, to a lesser extent, on the atmospheric conditions. Under certain circumstances (e.g., dry sand, water), the two were found to be in close agreement. For snow the filtered albedo exceeds the broadband albedo for all zenith angles; for meadow the broadband albedo will exceed the filtered albedo. Regression equations were derived to transform the VISSR filtered albedo to unfiltered broadband albedo for each surface type.
Aqueous phase oxidation of sulfur(IV) by hydrogen peroxide, methylhydroperoxide, and peroxyacetic acid
Authors: Lind John A. , Lazrus Allan L. , Kok Gregory L.
Published: February 2008

The aqueous phase oxidation kinetics of sulfur(IV) by hydrogen peroxide, methylhydroperoxide, and peroxyacetic acid have been investigated over the pH range 4.0–5.2 for hydrogen peroxide and methylhydroperoxide and 2.9–5.8 for peroxyacetic acid. The reagent concentrations used in these studies were in the micromolar range. In the cases of hydrogen peroxide and peroxyacetic acid, 1 mol of sulfate was produced for each mole of peroxide consumed. In the case of methylhydroperoxide, 0.73±0.04 mol of sulfate, and 0.27±0.04 mol of the methylsulfate were produced for each mole of peroxide consumed. The experimentally determined rate laws for the three reactions are given by d[peroxide]/dt = k[H+] [peroxide] [S(IV)]. The third order rate constants, k, for the three reactions were determined to be 7.2±2.0×107 M−2s−1 for hydrogen peroxide (18°C), 1.7±0.4×107 M−2s−1 for methylhydroperoxide (23°C), and 3.5±1.3 ×107 M−2s−1 for peroxyacetic acid (18°C). The oxidation kinetics of aqueous S(IV) by peroxyacetic acid also contained a second‐order term over the pH range investigated in this study, first‐order in both peroxyacetic acid and S(IV) concentrations. The rate constant k′ for this term was determined to be 6.1±2.6×102 M−1s−1. Temperature dependence studies over the range 6°–25°C yielded activation energies of 31.6±1.3 kJ/mol for methylhydroperoxide and 33.2±0.7 kJ/mol for peroxyacetic acid.
Chemistry of mesospheric potassium and its different seasonal behavior as compared to sodium
Authors: Swider William
Published: February 2008

The chemistry for sodium at mesospheric heights has been adapted for mesospheric potassium. The profile computed for potassium agees well with mid‐latitude lidar observations. A nightglow of 1 R is estimated for 767 nm, an amount probably undetectable. Both lidar data and photometer data indicate that the seasonal variation of potassium, unlike that of sodium, is negligible. Their different seasonal patterns are argued to arise most likely from modest differences in the rate coefficients, especially their dependence on temperature, for comparable reactions. Thus, the computed seasonal behavior of Na better matches the data if an exponential temperature dependence is assumed for NaO2 + O → NaO + O2, but a similar assumption for potassium leads to poorer agreement with data. The twice larger KO2 versus NaO2 formation rate appears responsible for the fact that variations of atomic oxygen alter the total abundance of sodium mote than they do for potassium. Eddy transport is apparently also important to the seasonal variation of Na, influencing both the total sodium species profile and the atomic oxygen distribution. Potassium and sodium concentrations near and below the peak appear unaffected by ion chemistry. This is probably less true of lithium.
A space‐time stochastic model of rainfall for satellite remote‐sensing studies
Authors: Bell Thomas L.
Published: February 2008

A model of the spatial and temporal distribution of rainfall is described that produces random spatial rainfall patterns with these characteristics: (1) The model is defined on a grid with each grid point representing the average rain rate over the surrounding grid box. (2) Rain occurs at any one grid point, on average, a specified percentage of the time and has a lognormal probability distribution. (3) Spatial correlation of the rainfall can be arbitrarily prescribed. (4) Time stepping is carried out so that large‐scale features persist longer than small‐scale features. Rain is generated in the model from the portion of a correlated Gaussian random field that exceeds a threshold. The portion of the field above the threshold is rescaled to have a lognormal probability distribution. Sample output of the model designed to mimic radar observations of rainfall during the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE), is shown. The model is intended for use in evaluating sampling strategies for satellite remote‐sensing of rainfall and for development of algorithms for converting radiant intensity received by an instrument from its field of view into rainfall amount.
Distribution of stratospheric NO2 at 10 mbar: SME global morphology and comparison to LIMS observations
Authors: Naudet J.‐P. , Thomas R. J. , Rusch D. W. , Clancy R. T.
Published: February 2008

The Solar Mesosphere Explorer Satellite (SME) has measured stratospheric NO2 since January 1982 using a visible light spectrometer. The presence of large amounts of aerosol injected into the stratosphere by El Chichon on April 4, 1982, temporarily prevented NO2 data analysis. At the end of 1983 the volcanic aerosol content of the atmosphere, although present, had decreased sufficiently to again allow reliable NO2 measurements. Monthly average results at 10 mbar are presented for a full year of SME observations, from October 1983 to September 1984. The observed morphology of NO2 is discussed. Interesting features include large amounts of NO2 in the summer hemisphere, with more in the south than the north. A low usually exists in the tropics. A comparison to Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) observations shows similar features.
On the depletion of ozone by a height increase of the tropical tropopause
Authors: Chimonas George
Published: February 2008

A model is presented in which transport rates through the lower stratosphere change in association with the height of the tropopause. The ozone distribution and column density are computed as the tropopause rises beyond its present position. Two distinct effects are noted. First, the total ozone content decreases by about 3% per kilometer rise of the tropopause from its present position. Second, there is a redistribution of ozone from statosphere to troposphere, which is quite gradual at first but suddenly becomes pronounced as the tropopause encroaches into the odd‐oxygen production region. The first effect is of minor significance in the modern atmosphere where it is masked by other dynamical and chemical variations. But the second effect is potentially important, as it suggests an associated major difference in the biological environment of the distant past when the atmosphere was warmer and less rich in oxygen.
Long‐term variation of the temperature of the middle atmosphere at mid‐latitude: dynamical and radiative causes
Authors: Chanin M. L. , Smirès N. , Hauchecorne A.
Published: February 2008

Temperature of the middle atmosphere has been measured since 1979 at the Observatory of Haute‐Provence (France, 44°N, 6°E) using the Rayleigh lidar technique. More than 500 temperature profiles in the height range 35–75 km have been used in that study. The main results are the following: temperature trends of opposite sign have been observed in the mesosphere (−20°K at 65 km) and in the stratosphere (+20°K at 40 km) between 1981 and 1985; but while the trend in the stratosphere is only found in winter, the tendency in the mesosphere is observed all year around. These temperature changes exhibit a highly significant correlation with the solar flux (represented by the radio flux at 10.7 cm) in the mesosphere and an equally significant anticorrelation in the winter stratosphere. On the other hand, the temperature at the 50‐km level does not present any long‐term variation. These results are interpreted as due to a superposition of a direct response of the mesosphere to the increase of the UV flux and a second effect, mainly present in winter, which affects all height ranges. This effect may or not be related to the 11‐year solar cycle, but its height dependence and its sign can only be interpreted by a change in the planetary wave activity.
Atmospheric effects of nuclear war aerosols in general circulation model simulations: Influence of smoke optical properties
Authors: Thompson Starley L. , Ramaswamy V. , Covey Curt
Published: February 2008

A global atmospheric general circulation model (GCM) is modified to include radiative transfer parameterizations for the absorption and scattering of solar radiation and the absorption of thermal infrared (IR) radiation by smoke aerosols. The solar scattering modifications include a parameterization for diagnosing smoke optical properties as a function of the time‐ and space‐dependent smoke particle radii. The aerosol IR modifications allow for both the “grey” absorber approximation and a broadband approximation that resolves the aerosol absorption in four spectral intervals. We examine the sensitivity of some GCM‐simulated atmospheric and climatic effects to the optical properties and radiative transfer parameterizations used in studies of massive injections of smoke. Specifically, we test the model response to solar scattering versus nonscattering smoke, variations in prescribed smoke single scattering albedo and IR specific absorption, and interactive versus fixed smoke optical properties. Hypothetical nuclear war created smoke scenarios assume the July injection of 60 or 180 Tg of smoke over portions of the mid‐latitude land areas of the northern hemisphere. Atmospheric transport and scavenging of the smoke are included. Nonscattering smoke cases produce roughly 40 Wm−2 more Earth‐atmosphere solar irradiance absorption over the northern hemisphere, when compared to scattering smoke cases having equivalent specific absorption efficiencies. Varying the elemental carbon content of smoke over a plausible range produces a 4°–6°C change in average mid‐latitude land surface temperature, and a variation of about 0.1 in zonally averaged planetary albedo in the northern hemisphere. The inclusion of IR absorption by smoke (IR specific absorption to visible specific extinction ratio of 0.1) produces mid‐latitude July temperature decreases that are 4°–6°C smaller in magnitude than produced by IR‐transparent cases. Thus the smoke IR opacity effect can make a substantial relative change in land surface temperature estimates when compared to July mid‐latitude land temperature decreases of 15°–20°C found in IR‐transparent cases.
Radiation transfer in plant canopies: Transmission of direct solar radiation and the role of leaf orientation
Authors: Verstraete Michel M.
Published: February 2008

Understanding the details of the interaction between the radiation field and plant structures is important climatically because of the influence of vegetation on the surface water and energy balance, but also biologically, since solar radiation provides the energy necessary for photosynthesis. The problem is complex because of the extreme variety of vegetation forms in space and time, as well as within and across plant species. This one‐dimensional vertical multilayer model describes the transfer of direct solar radiation through a leaf canopy, accounting explicitly for the vertical inhomogeneities of a plant stand and leaf orientation, as well as heliotropic plant behavior. This model reproduces observational results on homogeneous canopies, but it is also well adapted to describe vertically inhomogeneous canopies. Some of the implications of leaf orientation and plant structure as far as light collection is concerned are briefly reviewed.
On the multiple structure of atmospheric vortices
Authors: Mitsuta Yasushi , Monji Nobutaka , Ishikawa Hirohiko
Published: February 2008

Various scales of the multiple‐vortex phenomena observed in atmospheric vortices are reviewed and summarized. The nonaxisymmetric feature clearly seen in small‐scale vortices such as tornadoes is also recognized in the vortices of tropical cyclones. On the basis of both the physical resemblances and the swirl ratio similarity, this asymmetry in tropical cyclones is concluded to be a manifestation of multiple vortices. It is suggested that the evolution of a vortex from one‐cell to two‐cell to multiple vortices is a common feature in nature found not only in tornadoes, but also in other kinds of vortices, ranging from dust devils to tropical cyclones.
Changes in SBUV ozone profiles near Natal, Brazil, from 1979 to 1985
Authors: Barnes Robert A.
Published: February 2008

Ozone column amounts from Natal, Brazil, are calculated from radiances measured by the solar backscatter ultraviolet (SBUV) spectrometer aboard Nimbus 7 during March/April of 1979 and 1985. These amounts are calculated at altitudes from 36 to 47 km, a region where ozone varies exponentially with altitude. Calculations are made with the algorithm of Thomas and Holland (1977), providing ozone values from five SBUV channels at wavelengths from 255 to 292 nm. Each of the five column amounts is essentially independent of measurements from the other SBUV channels but not independent of the assumption of exponential ozone change with altitude. SBUV ozone amounts are significantly lower in 1985 than in 1979, with a distinct skew between the ozone profiles from the two data sets. The differences between the two SBUV data sets increase from 3.6% to at 4.7 mbar (36 km) to 15.9% at 1.2 mbar (47 km). There are corresponding changes in the backscattered radiances from SBUV for these data sets, with a distinct wavelength dependence for the changes. SBUV radiances from 1985 are higher by 2.3% at 292 nm, increasing to 9.6% at 255 nm. There is a direct relationship between radiance differences and differences in the ozone column amounts. The structure of the ozone changes does not agree with current calculations of ozone reduction due to fluorocarbons. Using SBUV values alone, it is not possible to separate atmospheric and instrumental changes. Published ROCOZ‐A ozone profiles from Natal in March/April 1985 show reasonable agreement with the 1979 SBUV measurements there. On an absolute basis the ROCOZ‐A measurements at Natal in 1985 do not agree with the 1985 SBUV profiles. Several tests can be performed to resolve these differences between instruments. Until these tests are completed, it would seem prudent to exercise caution before attributing changes in the SBUV radiances to the atmosphere.
The effect of diffusion on tracer puffs simulated by a regional scale Eulerian model
Authors: Brost Richard A. , Haagenson Philip L. , Kuo Ying‐Hwa
Published: February 2008

On a spatial scale of up to 1,100 km and a temporal scale of up to 36 hours, we used Eulerian models to simulate the transport and diffusion of a passive tracer released from a point source near the surface. An Eulerian tracer model was driven by meteorological analysis of 6‐hour rawinsonde data supplemented by the simulations of an Eulerian mesoscale meteorological model. The tracer model simulations were compared with 6‐hour integrated samples collected at 86 surface stations during the Cross‐Appalachian Tracer Experiment (CAPTEX) for six different releases. We examined the effect of the parameterizations of vertical and horizontal sub‐grid scale turbulent transport and the finite difference advection scheme on the simulations of concentration and the trajectories of the center of mass of the tracer at the surface. We found that the simulated trajectory error was sensitive to the vertical eddy diffusivity but insensitive to the advection scheme and hence insensitive to (horizontal) numerical diffusion. Using 70‐km horizontal resolution, only the most sophisticated advection scheme tested here (Prather, 1986) simulated a tracer puff with a horizontal area that was not too large during the first 36 hours after a point source release. The other schemes tested (Russell and Lerner, 1981; a simplified version of Smolarkiewicz, 1983) had enough numerical diffusion that the simulated horizontal tracer puffs were larger than the observed puffs. There were considerable differences in the capability of the tracer models to simulate individual releases, particularly for quantitative comparisons of simulated and observed concentrations.
Soluble atmospheric trace gases in the southwestern United States: 2. Organic species HCHO, HCOOH, CH3COOH
Authors: Dawson G. A. , Farmer J. Carl
Published: February 2008

The condensation method has been used at a variety of locations in the southwestern United States to determine the concentrations of formaldehyde, formic acid, and the group of organic acids coeluting with acetic acid (hereafter called “acetic acid”). Urban concentrations were typically as follows: formaldehyde, 1.4 ppb; formic acid, 3 ppb; and acetic acid, 4 ppb. In remote areas, formic and acetic acid concentrations were typically 0.9 ppb and 0.6 ppb, respectively. The data suggested that (1) in forested and probably desert regions, there is a substantial natural production of organics, particularly the acids, during summer, presumably by vegetation; (2) at least in the southwestern United States, in summer, there is a relatively weak coupling between the cycles of formaldehyde and formic acid; (3) near San Diego, organic acid lifetimes may be much shorter than previously expected, i.e., only several days; (4) at the lowest concentrations observed, partitioning of the organic acids into cloud water would give aqueous concentrations similar to those found in rain.