bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of nitrogen dioxide results measured by the Limb Infrared Monitor of the Stratosphere (LIMS) Experiment on NIMBUS 7
Authors: Russell James M. , Gille John C. , Remsberg Ellis E. , Gordley Larry L. , Bailey Paul L. , Drayson S. Roland , Fischer Herbert , Girard Andre , Harries John E. , Evans Wayne F. J.
Published: February 2008

The LIMS experiment launched on NIMBUS 7 measured vertical profiles of temperature and the concentrations of O3, H2O, HNO3, and NO2 during the period from late October 1978 until late May 1979. This paper discusses the validation of results from the NO2, channel and the quality of the data. The discussion includes channel characteristics, experiment errors due to instrument and spacecraft effects, predicted and measured precision, predicted accuracy, and comparisons with correlative measurements made in a series of balloon underflights. All balloon measurements used for comparisons were made using the solar occultation technique, and since NO2 varies significantly over the diurnal cycle, a photochemical model was used to time translate the data to the LIMS time. Because of this the comparisons were primarily qualitative. Features such as profile shape and slope of the mixing ratio altitude distribution are in good agreement. The mean difference between LIMS results and the balloon data is well within the range of the sum of the error bars for the two data sets. Comparisons are also made with past balloon measurements taken in the 40°N to 50°N latitude band and with photochemical model predictions of the vertical profile. The LIMS data fall within the range of previous mixing ratio measurements, and they are consistent with model estimates. The calculated on‐orbit precision is ≈0.3 ppbv and the estimated accuracy from simulations is ≈2 ppbv over the 3‐mbar to 10‐mbar range. Accuracy degrades at higher and lower pressure levels. These results provide the first day‐night set of NO2 measurements from space.
An intercomparison of SAGE and SBUV ozone observations for March and April 1979
Authors: Cunnold D. M. , Pitts M. C. , Trepte C. R.
Published: February 2008

Thirty‐eight latitudinal cross sections of stratospheric ozone observed by the SAGE and SBUV satellite instruments on the same days in March and April 1979 and at approximately the same latitude are compared. Differences in the zonal‐mean mixing ratios are found. At pressures less than 5 mbar, SAGE gives approximately 20% larger mixing ratios at tropical latitudes (after a correction has been applied for the expected diurnal variation of ozone.) At 50°–70° latitude at 10 mbar, the SBUV retrievals appear to underestimate ozone by approximately 15%. Mixing ratio differences are also noted in the tropics at 30 mbar. Longitudinal variations with a vertical scale exceeding 8 km are analyzed. The uncorrelated portions of the SAGE variances are approximately consistent with the SAGE noise model and resulting ozone profile error bars. Between 2 and 10 mbar, the random noise in an individual wave component (having this vertical scale) is expected to be less than 2% everywhere in both experiments except for 1% at tropical latitudes in the SBUV experiment. Based upon the correlated variances, the amplitudes of the inferred longitudinal ozone variations are found to be the same on the average at mid‐latitudes between 1 and 10 mbar. However, the relative amplitudes also are found to be dependent on the atmospheric situation. Systematic differences in the amplitudes at 0.4 and 30 mbar are discussed. Wave detectability by both sensors at 58°S in early April is illustrated and compared against TIROS‐N temperature observations for that period.
Simultaneous stratospheric measurements of H2O, HDO, and CH4 from balloon‐borne and aircraft infrared solar absorption spectra and tunable diode laser laboratory spectra of HDO
Authors: Rinsland C. P. , Goldman A. , Devi V. Malathy , Fridovich B. , Snyder D. G. S. , Jones G. D. , Murcray F. J. , Murcray D. G. , Smith M. A. H. , Seals R. K. , Coffey M. T. , Mankin W. G.
Published: February 2008

High‐resolution infrared solar absorption spectra recorded from a balloon‐borne platform at 33‐km altitude and an aircraft at 12‐km altitude have been analyzed to derive simultaneous stratospheric concentrations of H2O, HDO, and CH4. The data were obtained near 33°N with the University of Denver interferometer during a balloon flight in October 1979 and with the NCAR interferometer aboard a Sabreliner aircraft in September 1982. The analysis of the balloon spectra indicates the H2O mixing ratio increased from 3.5 to 4.8 ppmv and the CH4 mixing ratio decreased from 1.15 to 0.70 ppmv between 18 to 38 km. Tunable diode laser laboratory spectra were recorded and analyzed to derive absolute intensities and air‐broadened half widths of selected lines of the v2 band of HDO. With these parameters, which are reported here, an HDO profile that increases from 0.61 ppbv near 18 km to 0.88 ppbv near 29 km is inferred from the balloon spectra, corresponding to a D/H ratio, normalized to the reference value of 158 atomic parts per million of Standard Mean Ocean Water (SMOW), of 0.55 to 0.67. The average D/H value of 0.40 above 12 km, derived from the aircraft spectra, provides additional spectroscopic evidence for a large depletion in the D content of water vapor in the lower stratosphere. The simultaneous vertical profiles for the three gases retrieved from the balloon spectra are consistent, within the estimated precision of the data (±10%), with methane oxidation as the sole source of stratospheric H2O in addition to H2O transported upward through the tropopause. However, there is an indication of a small increase in the total hydrogen in H2O and CH4 with altitude, and we believe more precise simultaneous measurements are required.
Three unusual strokes in a triggered lightning flash
Authors: Idone Vincent P. , Orville Richard E.
Published: February 2008

Time‐resolved photographic records of three strokes of a triggered lightning flash are examined. These strokes exhibit several examples of novel behavior that include (1) the abrupt transformation of dart leaders to stepped leaders and (2) the partial “reflection” of dart leader luminosity back up the channel. Both phenomena are associated with an apparent discontinuity in channel characteristics between the natural and artificial (wire) sections of the channel. We estimate the ratio of characteristic impedances for these sections to have an upper bound of about a factor of 3. Analysis of one of the dart leader“reflections” yields a propagation speed of 9.6×107 m/s, whereas the dart leader and return stroke speeds (two‐dimensional) over the same channel section are 1.7×107 m/s and 13×107 m/s respectively. Also, one of the return strokes reveals the occurrence of two distinct waves of luminosity that are separated by only 5 μs and that travel up nearly identical channels that differ only in the channel terminus.
The temporal behavior of upper stratospheric ozone at low latitudes: Evidence from Nimbus 4 BUV data for short‐term responses to solar ultraviolet variability
Authors: Hood L. L.
Published: February 2008

Ozone mixing ratios at pressure levels near 2 mbar, derived from Nimbus 4 backscattered ultraviolet (BUV) profile data and averaged within 13 latitude zones between 65°N and 65°S, are studied for the period November 1970 to April 1972. In agreement with previous analyses the largest temporal variations are negatively correlated with changes in zonally averaged equivalent temperature measured simultaneously with the Nimbus 4 selective chopper radiometer. After approximately removing this component using a first‐order photochemical model, residual mixing ratios for latitudes ≲30° contain short‐term variations (periods ≲35 days; rms amplitude ∼1%) that are positively correlated with variations in the solar 10.7‐cm flux and in the 185–190 nm solar ultraviolet flux model of Lean et al. (1982). The correlation coefficients (R = 0.2–0.5; p> 0.95) are larger for each latitude zone when computed versus the ultraviolet flux model than when computed versus the 10.7‐cm flux, suggesting that photochemical responses of upper stratospheric ozone to solar ultraviolet variability at wavelengths near 200 nm are primarily responsible. At latitudes ≳40°, larger‐amplitude wintertime ozone fluctuations associated with planetary‐scale pressure waves become dominant and reduce the computed correlation coefficients to statistically insignificant levels. Linear regression analyses are performed to obtain estimates for the average percent change of ozone at low latitudes and on the considered time scale for given changes in 10.7‐cm flux and in the UV flux model.
A diabatic circulation experiment in a two‐dimensional photochemical model
Authors: Guthrie P. D. , Jackman C. H. , Herman J. R. , McQuillan C. J.
Published: February 2008

A two‐dimensional photochemical model based on diabatic circulation has been used to simulate the behavior of N2O, CFCl3 (F‐11), and CF2Cl2 (F‐12). The circulation is based on estimates of net heating from the ground to 60 km. Eddy diffusion has been reduced with respect to other model studies with Kzz = 2 × 103 cm2 s−1 everywhere above 100 mbar. Resulting tracer profiles show reasonable agreement with measured profiles in the tropics and fall off much more sharply with altitude than those produced by models using larger values of Kzz. The agreement obtained is at least as good as that obtained with adjustable, eddy diffusion parameters. The diabatic circulation treatment is more closely related to real physical processes and thus more easily interpreted. Diffusive mixing appears to be more important in determining the details of the tracer distributions than the basic morphology.
Stratospheric HF mixing ratio profiles in the Northern and Southern Hemispheres
Authors: Park J. H. , Kendall D. J. W. , Buijs H. L.
Published: February 2008

Spectra obtained by balloon‐borne Michelson interferometers over South Australia in 1977 and New Mexico in 1978 have been analyzed to obtain HF mixing ratios using a recently developed, sensitive analysis method for Fourier transform spectroscopy. The stratospheric HF mixing ratio appears to be significantly larger in the northern hemisphere than in the southern hemisphere for similar respective latitudes with the profiles having a similar vertical shape: the HF mixing ratio increases from 20 to 25 km, stays approximately constant between 25 and 35 km, and increases upward from 35 km. A brief discussion is given of possible causes for the HF profile shape.
Further characteristics of positive radiation fields from lightning in sweden
Authors: Cooray Vernon
Published: February 2008

Characteristics of the fields radiated by lightning in Sweden have been reported recently by Cooray and Lundquist (1982). That study is supplemented here by presenting additional characteristics of those fields that are hypothesized to be produced by positive return strokes. The new data presented here indicate that the currents in the sources of these radiation fields are either similar in duration to the currents in negative return strokes or of longer duration. This is based on the observation that the duration of these radiation fields are either similar to that of negative return strokes or of longer duration. During the first 50–100 μs both normal and long‐duration waveforms, and hence the inferred currents, seem to behave in a similar manner. That is, there is an initial peak in the first few tens of microseconds and then a decay. After this the field and the inferred currents in some positive strokes continue to decay and in others start to increase again and reach a second peak in a few hundred microseconds. While the current is flowing, in some cases, a burst of electromagnetic pulses with a separation between pulses of about 3 μs or less occur. The shape of the inferred long‐duration currents are similar to the shapes of the positive return stroke currents measured in lightning strikes to high towers.
Test of a prototype eddy accumulator for measuring atmospheric vertical fluxes of water vapor and particulate sulfate
Authors: Speer R. E. , Peterson K. A. , Ellestad T. G. , Durham J. L.
Published: February 2008

An eddy accumulator was developed and operated during the Dry Deposition Intercomparison Study at Champaign, Illinois, in June 1982. The system collected paired samples for water vapor and particulate sulfate flux measurements, one sample for upward eddies and the other for downward eddies. Nineteen water vapor samples were analyzed gravimetrically, and two sulfate samples were analyzed by ion chromatography. Comparison of water vapor results with eddy correlation measurements showed that discrepancies exceeded predicted errors. No significant results were obtained from the sulfate samples.
Comparison of horizontal winds from the LIMS satellite instrument with rocket measurements
Authors: Smith A. K. , Bailey P. L.
Published: February 2008

Statistical results are given for a comparison between horizontal geostrophic winds computed from satellite height data and all available in situ rocket wind soundings during a 7‐month period. The satellite data are the daily mapped fields from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument, which extend from 100 to 0.1 mbar. Results indicate that in both the tropics and the extratropical northern hemisphere, the average zonal and meridional wind speeds agree to within 2–4 m s−1 throughout the stratosphere. The rms differences are much larger, with values of 5–10 m s−1 in the lower stratosphere, increasing to 20–40 m s−1 in the lower mesosphere. Time series show that LIMS and rocketsonde zonal wind speeds show coherent variations with temporal periods of 1–2 weeks and more, and both exhibit irregular variations on time scales of less than 1 week.
Fair‐weather electricity
Authors: Ogawa Toshio
Published: February 2008

Large‐scale fair‐weather electricity is reviewed. First, it is shown that the source current flowing out from a model thunderstorm cloud extends within an area ∼±100 km in the horizontal distance in fair weather. Next the global circuit theory using the spherical harmonic function is reviewed to understand the global spreading of the thunderstorm‐produced electrical potential. Then the quantitative estimation of global distribution of the electric field and the air‐earth current is made by a simple equipotential ionospheric model to see responses to changes of atmospheric conductivity and condensation nuclei. It is then shown where transition of the fair‐weather electricity from the local type to the global type occurs. Recent topics on large electric fields measured in the middle atmosphere by using rockets and the international cooperation effort hosted by the atmospheric research group at the University of Wyoming are mentioned last.
Ice conductivity restraints on the inductive theory of thunderstorm electrification
Authors: Illingworth A. J. , Caranti J. M.
Published: February 2008

According to the inductive theory of thunderstorm electrification, a small ice crystal bouncing off the underside of a larger hydrometeor falling in the presence of an electric field should remove some of the field‐induced polarization charge from the surface of the larger particle; subsequent gravitational separation of the two particles should then result in a rapid growth of the electric field. However, because of the finite surface conductivity of the ice, it is not obvious that the polarization charges can flow along the ice surface in the short interaction time. We report laboratory experiments on the effect of an external electric field on the charge transferred during individual collisions of small (typically, 100‐μm) ice spheres with larger ice targets. When the surface conductivity of the ice was artificially increased by using 10−2 M NaCl, the full theoretical charge transfer was observed, but at 10−5 M NaCl, no field‐dependent charge transfer could be detected. Airborne measurements of cloud and precipitation purity have shown that 10−4 M NaCl is occasionally reached in low‐level stratiform clouds in polluted regions, but even with this degee of contamination the inductive mechanism operates at less than 20% of its potential efficiency at −10°C; at lower temperatures this fraction is reduced still further. We conclude that the inductive mechanism cannot account for the observed electrification of thunderstorms unless other contaminants are having an unexpectedly large effect on the conductivity.
Positive cloud‐to‐ground lightning observations
Authors: Beasley William
Published: February 2008

Cloud‐to‐ground lightning discharges have been studied for more than 50 years by means of visual, photographic, and electromagnetic observations as well as direct measurements of current. One of the first questions to be addressed was that of the sign of net effective charge transferred to earth. The conventional wisdom on the subject has been that most cloud‐to‐ground lightning flashes transfer net negative charge from cloud to ground. There is also evidence that up to one third of the flashes observed in a given study could transfer net positive charge to earth. Both the subject of positive charge transfer to earth in general and the subject of positive return strokes received attention by Workman, Brook, and others in New Mexico occasionally over the last 30 years. Relatively recently, there have been increasingly numerous reports of cloud‐to‐ground lightning that transfers positive charge to earth in winter thunderstorms in Japan, in summer thunderstorms in Scandinavia, in severe storms in the U.S. Great Plains, in summer thunderstorms in the western United States, in summer thunderstorms in Florida, and in fall and winter thunderstorms in the northeastern United States. Furthermore, from the most recent observations it appears that positive cloud‐to‐ground flashes often have return strokes similar to those in negative cloud‐to‐ground flashes, except for polarity; that most often there is only a single return stroke; and that often a continuing current of large amplitude, or possibly a discharge in the cloud, follows the return stroke.
Correlated peak relative light intensity and peak current in triggered lightning subsequent return strokes
Authors: Idone Vincent P. , Orville Richard E.
Published: February 2008

We have examined the correlation between peak relative light intensity (LR) and stroke peak current (IR) for 39 subsequent return strokes in two triggered lightning flashes. One flash contained 19 strokes and the other 20 strokes for which direct measurements were available of the return stroke peak current at ground. Peak currents ranged from 1.6 to 21 kA. The measurements of peak relative light intensity were obtained from photographic streak recordings using calibrated film and microsecond resolution. Correlations, significant at better than the 0.1% level, were found for the following functional relationships: LR vs. IR, log LR vs. log IR, log LR vs. IR, and log LR vs. IR2. Although a relation between LR and IR is evident in these data, none of the analytical relations considered is clearly favored. We also examined the correlation between LR and the maximum rate of current rise (dI/dt)max but found less correlation than that between LR and IR. In addition we evaluated the peak relative intensity near ground for 22 dart leaders and found a mean ratio of peak dart leader to peak return stroke relative light intensity of 0.1 with a range of 0.02–0.23. Using two different methods, we estimated the peak current near ground in these dart leaders to range from 0.1 to 6 kA.
A global climatology of total ozone from the Nimbus 7 total ozone mapping spectrometer
Authors: Bowman Kenneth P. , Krueger Arlin J.
Published: February 2008

A global climatology of total column ozone has been computed from 4 years of daily observations by the total ozone mapping spectrometer aboard the Nimbus 7 polar‐orbiting satellite. Observations were made at local noon; no observations are available in polar regions during the polar night. The orbital data have been area averaged onto a regular 5° by 5° latitude‐longitude grid. The global coverage is more than 90% complete during the last 3 observing years (October 1979 to September 1982) and approximately 70% complete during the first year (October 1978 to September 1979). Global maps of the temporal mean and rms variance and the amplitude and phase of the annual and semiannual harmonics are presented. Similar analyses of the zonal mean values are given along with a time‐latitude section of the zonal‐mean total ozone. This climatology should be useful both for validating numerical models and for inspiring theoretical analyses.
Model for dry snow metamorphism by interparticle vapor flux
Authors: Gubler H.
Published: February 2008

Kinetic growth metamorphism lowers the mean number of bonds between the ice particles in snow. During the beginning state of snow metamorphism, at a large mean temperature gradient, significant particle growth occurs only at preferred growth sites. Three‐dimensional approximations of the sink‐source geometry are introduced to model particle growth and shrink rates. The calculations show that enhanced growth occurs at very small and at large sink‐source distances. The consideration of growth rate enhancement by differences in radii of curvature between sink‐source particles accounts for metamorphism at very low mean temperature gradients. Final particle size distributions and the reduction of the particle number density by metamorphism are calculated and may be compared with measured distributions.
Atmospheric fluxes and marsh‐soil inventories of 7Be and 210Pb
Authors: Olsen C. R. , Larsen I. L. , Lowry P. D. , Cutshall N. H. , Todd J. F. , Wong G. T. F. , Casey W. H.
Published: February 2008

The atmospheric flux of 7Be over a 2‐year period at a coastal site (Norfolk, Virginia) and at an inland site (Oak Ridge, Tennessee) typically supports inventories ranging from 1.0 to 2.0 pCi/cm2 (1 pCi = 0.037 Bq), with the highest inventories generally occurring in the spring and the lowest occurring in the fall. The calculated average daily fluxes required to support these inventories range from 0.013 to 0.026 pCi cm−2 d−1. Despite the different production‐source terms for 7Be and 210Pb, there is a high degree of correlation between their measured total monthly deposition reflecting the importance of washout in removing both radionuclides from the atmosphere. Beryllium 7 inventories in soil and vegetated marsh cores compare favorably with inventories calculated from the atmospheric deposition data. Lead 210 inventories in soil and vegetated marsh cores may be enriched (by 20–30%) in relation to inventories calculated from its depositional flux to bucket samplers. Possible explanations for this enrichment are that above‐ground vegetation is more efficient at collecting dry aerosols (containing short‐lived radon daughters) than buckets or that foliage is an effective trap for particles containing sorbed 210Pb which may be eroded from unvegetated surfaces by wind or water. The vertical distribution and inventory of both 7Be and 210Pb in marsh cores are affected by the presence of vegetation and the location of the groundwater table.
Quality of remote sensing measurements of cloud physical parameters in the Cooperative Convective Precipitation Experiment
Authors: Wu Man‐Li C.
Published: February 2008

In order to develop the remote sensing techniques to infer cloud physical parameters, a multispectral cloud radiometer (MCR) was mounted on a NASA high‐altitude aircraft in conjunction with the Cooperative Convective Precipitation Experiment in 1981. The MCR has seven spectral channels, of which three are centered near windows associated with water vapor bands in the near infrared, two are centered near the oxygen A band at 0.76 μm, one is centered at the 1.14‐μm water vapor band, and one is centered in the thermal infrared. The reflectance and temperature measured on May 31, 1981, are presented together with theoretical calculations. The results indicate that the MCR produces quality measurements. Therefore several cloud parameters can be derived with good accuracy. The parameters are the cloud scaled optical thickness, cloud top pressure, volume scattering coefficient, particle thermodynamic phase, effective mean particle size, and cloud top temperature.
Theory of natural convection in snow
Authors: Powers D. , O'Neill K. , Colbeck S. C.
Published: February 2008

Buoyancy‐driven flows of air in show are modeled including the effects of phase change and inclination. Phase change between water vapor and ice is important because of latent heat terms in the energy equation. Upper boundaries of the snow are taken as either permeable or impermeable, with temperature or heat flux specified at the lower boundary. When the ratio of thermal to mass diffusivity is greater than 1, phase change intensifies convection. When this ratio is less than 1, phase change damps convection. The effects of permeable top and uniform heat flux bottom boundary conditions on heat transfer are quantified and described as linear functions of Ra/Racr, where Ra is the Rayleigh number and Racr refers to the critical value for the onset of Benard convection. The slope of each function depends only on the thermal boundary condition at the lower boundary. If a snow cover is inclined, Rayleigh convection occurs for any nonzero Rayleigh number. Velocity profiles for flows in inclined layers with permeable tops are derived, and it is found that velocity is proportional to Ra sin Φ, where Φ is the angle of inclination from the horizontal. The numerical results for different boundary conditions compare reasonably well with experimental results from the literature.
Modeling atmospheric transport to the Marshall Islands
Authors: Merrill John T. , Bleck Rainer , Avila Lixion
Published: February 2008

Isentropic trajectory analyses are presented which support the hypothesis that atmospheric continental material found at Enewetak Atoll (11.3°N, 162.3°E) during the Sea‐Air Exchange (SEAREX) experiments in 1979 had its origin primarily in Asia in the springtime (dry season experiment) and in North and Central America in the summer (wet season experiment). Fields of wind, Montgomery potential, and pressure on isentropic surfaces are obtained from global isobaric analyses by vertical interpolation. Trajectories backward in time from the area at and upwind of the experiment site were calculated using these fields. In April and May 1979 the atmospheric chemistry at Enewetak was influenced strongly by long‐range transport from Asia; this transport was primarily in the potential temperature range 305–315 K with travel times of 8–13 days. Westerly winds over Asia at 350–600 mbar carry continental materials over the ocean, and as the air moves southward, subsidence occurs until the air is entrained in the trade wind flow. During July and August 1979 the transport paths were from open ocean areas and from near North and Central America at 305–310 K with travel times of 17–21 days. The trajectories remained at low levels within the boundary layer during this period. Also discussed is a meteorological analysis of dust storms in China, which shows that a mechanism exists for lifting eolian material to the upper troposphere. There is substantial uncertainty in the individual trajectories, and the factors limiting their accuracy are discussed. Given the consistency of the trajectory analyses with the chemical results, we now have a coherent picture of some of the processes responsible for long‐range transport to the subtropical open ocean.
Implications of the comparison of ozone abundances measured by the Solar Mesosphere Explorer to model calculations
Authors: Rusch David W. , Eckman Richard S.
Published: February 2008

Two years of ozone measurements from the Solar Mesosphere Explorer satellite are compared to the results of a model of lower mesospheric photochemistry. The measured ozone mixing ratios are larger than those predicted by the model by as much as a factor of two at pressures near 0.1 mbar and 1.3 at 1.0 mbar using currently accepted reaction rate coefficients. The model is brought into good agreement with the measurements over a wide range of latitudes and solar zenith angles only if the efficiency of the odd hydrogen catalytic cycle which destroys odd oxygen is decreased by 30–50%.
A critical analysis of CLO and O3 in the mid‐latitude stratosphere
Authors: Froidevaux Lucien , Allen Mark , Yung Yuk L.
Published: February 2008

In the upper stratosphere, an altitude range in which ozone should be in photochemical steady‐state, calculated ozone abundances that are derived from a one‐dimensional photochemical model with updated chemistry are up to 60% smaller than mean observed values. On the other hand, the model results for the key free radicals (HOx, NOx, and ClOx species) in the catalytic destruction of ozone are shown to be in reasonable agreement with available measurements. The general validity of the model simulation of ClOx chemistry is confirmed through a detailed intercomparison between the computed ClO diurnal variation and recently published ground‐based microwave observations. Since many field measurements are performed near sunrise or sunset, the uncertainties in the model results arising from the details of the radiation field calculations at large zenith angles are discussed. Although the calculated ozone discrepancy could be the result of a number of errors in adopted photochemical parameters, a sensitivity analysis shows that no reasonable change in any one or two parameters can resolve this problem. The limited available observations regarding the ratio of atomic oxygen to ozone suggest a possible discrepancy in that quantity, which could be responsible for a large part of the ozone problem.
An observed upper limit on stratospheric hydrogen peroxide
Authors: de Zafra Robert L. , Parrish A. , Barrett J. , Solomon P.
Published: February 2008

We have conducted a search for emission from the 70,7 → 61,5 rotational‐torsional transition of stratospheric hydrogen peroxide at 270.610 GHz, using a ground‐based millimeter‐wave heterodyne receiver which has been used successfully to measure stratospheric ClO, HO2, HCN and other trace gases. Observations were made at Mauna Kea, Hawaii (19.5°N) in late May and early June of 1983. No definitive signal was detected in the output of a 256‐channel filter bank spectrometer. From this result we deduce an upper limit on the H2O2 mixing ratio between approximately 30 and 50 km altitude which is approximately 2 times that predicted from a recent stratospheric model by Sze and Ko. Towards its middle altitude range, this limit overlaps a recent upper limit set by K. V. Chance and W. A. Traub (1984) between 22 and 38 km and is ∼2 × lower in the mixing ratio at 32 km than that implied by a tentative H2O2 detection by J. W. Waters et al. (1981).
A dynamically based transport parameterization for one‐dimensional photochemical models of the stratosphere
Authors: Holton James R.
Published: February 2008

The net vertical tracer flux in the stratosphere is due primarily to advection by the global‐scale mean meridional circulation, not to diffusion by turbulent eddies. Using a simple model of this circulation, it is shown that the net flux can be approximated by a flux‐gradient relationship in which the vertical “eddy transport” coefficient is proportional to the square of the diabatic heating rate and inversely proportional to the rate at which meridional tracer gradients are destroyed by horizontal eddy mixing and chemical damping. Thus the transport coefficient will differ for tracers with differing chemical lifetimes. Profiles computed for various source gases (CH4, N2O, CF2Cl2, and CFCl3) show that this parameterization provides an improvement over conventional formulations that utilize a single transport coefficient for all species.
Dry deposition models and the air/sea exchange of trace elements
Authors: Arimoto R. , Duce R. A.
Published: February 2008

Dry deposition rates of representative trace elements were calculated from measured mass‐particle size distributions and two deposition models (Slinn and Slinn, 1980; Williams, 1982). The aim of the study was to investigate how deposition rates were affected by (1) differences in transfer velocities to smooth and broken water surfaces, (2) wind speed, and (3) relative humidity. Comparisons of the dry deposition rates that were calculated for sodium and aluminum suggest that surface waves do not greatly affect the dry deposition rates of sea‐salt or mineral aerosol particles, respectively. In contrast, the deposition rate for 210Pb was as much as 5 times higher when a term was included to account for the effects of broken water surfaces. These results suggest that the air/sea exchange of a substance whose mass is predominately associated with small particles may be significantly enhanced by deposition to broken water surfaces.
On the acidity of dew
Authors: Pierson William R. , Brachaczek Wanda W. , Gorse Robert A. , Japar Steven M. , Norbeck Joseph M.
Published: February 2008

Nightly dew samples were collected on Allegheny Mountain in southwest Pennsylvania in August 1983. The dew was found to be acidic, with meanpH∼4.0. Free H+comprised >80% of the total acidity, and the composition approximated an H2SO4/HNO3mixture with average SO42−/NO3−mol ratio ∼1.3. The chemistry of the dew resembled that of rain at Allegheny, though the dew was generally more dilute. Atmospheric HNO3(g) was chiefly responsible for the dew NO3−. SO2was the source of ∼80% of the dew SO42−. The allocation of dew H+among atmospheric precursors was HNO3∼30%, SO2≥ 60%, aerosol H+≤ 10%. The most acidic dews were associated with wind from the west. Average deposition velocities (stated in centimeters per second) to dew were HNO3, 0.24; NO2, <0.02; SO2, ∼0.04; aerosol SO42−, ∼0.02; aerosol NH4+, 0.024; and aerosol species, 0.02–1. Comparison of the HNO3deposition velocity with ten‐fold higher summer daytime values reveals a pronounced diurnal variation. The 0.24 cm/s value for HNO3may represent a maximum for any gas or submicron aerosol species whenever the atmosphere is strongly stable. Not all of the S(IV) in dew had been converted to SO42−by morning; thus the rate of oxidation must have been on a time scale of hours at nighttime ambient temperatures. In contrast, S(IV) in rain and fog samples was not evident. Deposition fluxes and cumulative deposition totals involving dew, rain, and settled fog water were compared. Rain proved by far the most important for deposition of all solute species, including acid.
Mass spectrometric study of tropospheric ions in the northeastern and southwestern United States
Authors: Eisele F. L. , McDaniel E. W.
Published: February 2008

Ground level measurements of naturally occurring atmospheric ions were performed in a remote desert area of southeastern Arizona and on top of Mount Washington in New Hampshire. High‐resolution measurements of the positive ion spectrum revealed the presence of the NH+4·(H2O)n ion family and a stable core ion at mass 80. Two more variable peaks at mass 60 and 94 were also observed at both locations. The negative spectrum was dominated by ion peaks corresponding to the ion family NO−3·(HNO3)m·(H2O)n. The variability of the observed ion spectra and meteorological effects are discussed and compared to measurements from the previous year.
On the atmospheric photochemistry of nitric acid
Authors: Austin J. , Garcia R. R. , Russell J. M. , Solomon S. , Tuck A. F.
Published: February 2008

Measurements of the temporal and spatial variations in HNO3, particularly those from the Nimbus 7 limb infrared monitor of the stratosphere (LIMS) satellite experiment, are compared to both a two‐dimensional chemical/dynamical model and to chemistry/parcel trajectory analyses. Significant discrepancies are found between the observed and modeled variations in the winter season, especially in the polar night region. The study of the evolution of HNO3 suggests that an important source exists for this species in the high‐latitude winter stratosphere that is not included in presently accepted photochemical schemes. Possible reactions to account for this discrepancy are explored.
Sodium nightglow: Chemically independent of sodium content
Authors: Swider William
Published: February 2008

The process Na + O2 + M → NaO2 + M apparently is the first in a sequence of reactions which chemically controls the sodium content of the mesosphere. The effectiveness of this reaction is reduced by NaO2 + O → NaO + O2, which generates only one tenth as much NaO as does the Chapman process Na + O3 → NaO + O2, using current rate coefficients. Hence Chapman's mechanism, which requires the formation of some Na(2P) when NaO reacts with O, remains the principal source of the sodium D‐lines at night. However, the net loss of sodium by Na + O3 → NaO + O2 is small since the reaction between NaO and O is fast and since [O]≫[O3] in the mesosphere. The chemistry of the nightglow, a catalytic cycle with sodium as the catalyst, is shown to be virtually uncoupled from that of the sodium content. It follows that seasonal variations of the content and the nightglow can be fairly independent of each other, as has been observed. Observations that both mesospheric ozone and the sodium nightglow attain maxima during the equinoxes is in qualitative accord with the Chapman mechanism as the dominant source of the sodium nightglow at 5893 Å.
Comparison of stratospheric air parcel trajectories calculated from SSU and LIMS satellite data
Authors: Austin John
Published: February 2008

Midstratospheric trajectories for February and March 1979 are calculated using geopotential analyses derived from limb infrared monitor of the stratosphere (LIMS) data. These trajectories are compared with the corresponding results using stratospheric sounding unit (SSU) data. The trajectories are quasi‐isentropic in that a radiation scheme is used to imply cross‐isentrope flow. The results show that in disturbed conditions, quantitative agreement between the trajectories, that is, within 25 great circle degrees (GCD) (one GCD ≈ 110 km) may be valid for only 3 or 4 days, whereas during quiescent periods quantitative agreement may last up to 10 days. By comparing trajectories calculated with different data, some insight can be gained as to errors due to vertical resolution and horizontal resolution (due to infrequent sampling) in the analyzed geopotential height fields. For the disturbed trajectories described in this paper, the horizontal resolution of the data was more important than vertical resolution. For the quiescent trajectories described in this paper, which could be calculated accurately for a longer duration because of the absence of appreciable transients, the vertical resolution of the data was found to be more important than the horizontal resolution. It is speculated that these characteristics are also applicable to trajectories calculated during disturbed and quiescent periods in general. A review of some recently published trajectories shows that the qualitative conclusions of such works remains unaffected when the calculations are repeated using different data.
The Mg 280‐nm doublet as a monitor of changes in solar ultraviolet irradiance
Authors: Heath Donald F. , Schlesinger Barry M.
Published: February 2008

Five years of 160‐ to 400‐nm solar flux measurements by the Solar Backscattered Ultraviolet experiment on Nimbus 7 have been analyzed. The flux in the center of strong lines and at shorter wavelengths varies with periods that correspond to modulation by the rotation of active regions. The modulation is greater at the centers of strong lines and at shorter wavelengths, corresponding to radiation that originates at higher levels in the solar atmosphere. The ratio of the irradiance in the core of the Mg 280‐nm line to the irradiance at neighboring wavelengths is used as an index of solar variation. A scaling factor is derived by comparing rotational modulation at other wavelengths with the rotational modulation of the index. The scaled Mg II 280‐nm strength successfully represents both rotational and long‐term variations across the Al absorption edge near 210 nm. This ratio can therefore provide an empirical representation of long‐term ultraviolet solar variability. Scaling factors are derived and changes estimated at several ultraviolet wavelengths. At 204 nm, in the wavelength region that drives atmospheric photochemistry, the solar irradiance drops about 4% from its average level for 1979–1980 to late 1983. The total estimated range of variation of the 27‐day averaged (one rotation) 204‐nm irradiance is 6%, over the 5 years of measurements. A least squares fit shows that over the 5 years, 27‐day averages of 10.7‐cm radio flux and of the Mg II index follow a linear relation. The radio flux can therefore be used to estimate changes in the solar ultraviolet for times before the launch of Nimbus 7.
A particle dry‐deposition parameterization scheme for use in tracer transport models
Authors: Giorgi Filippo
Published: February 2008

A particle dry‐deposition parameterization scheme for use in tracer transport models is presented. The scheme produces particle deposition velocities relative to the bottom transport model level expressed in terms of wind speed, temperature, and air density at the bottom model level; surface momentum drag coefficient; particle size and density; characteristics of the surface roughness elements; and several parameters derived for different surface types. A two‐layer boundary layer model is employed to calculate the surface deposition velocities. Formulas for the particle deposition velocity are derived for four surface types: smooth surfaces, surfaces with bluff roughness elements, ocean surfaces, and vegetative canopies. The following processes are included in the model: turbulent transport through the boundary layer, gravitational settling, deposition by Brownian diffusion, interception and impaction on the surface roughness elements, diffusiophoresis on water surfaces, and, in limited cases, particle bounce‐off. Electrical and thermophoretic effects are ignored as well as particle blow‐off. As an illustrative example, the scheme is applied to a general circulation model to calculate the deposition velocities of ambient tropospheric aerosols. The calculated deposition velocities show a strong dependence upon the wind field in the bottom model level, the particle size distribution, and, to a lesser extent, the surface type. Particle mass deposition velocities of continental aerosols are found to lie in the range 0.003–0.036 cm/s for the accumulation mode and in the range 0.5–2.5 cm/s for the coarse mode.
Factor of 2 error in balloon‐borne atmospheric conduction current measurements
Authors: Few A. A. , Weinheimer A. J.
Published: February 2008

The balloon‐borne, vertical‐wire antenna system used for measurement of the atmospheric conduction current above the boundary layer of the earth was introduced by Kasemir (1960) and has been utilized by several investigators to measure globally representative values of the air‐earth current. The values of the atmospheric conduction current density measured by this technology and presented in the literature (∼2 pA/m2) ought to be multiplied by a factor of 2 to correct for physical processes at the antenna boundary. An analysis of the interaction of the balloon‐borne, vertical‐wire antenna with the atmospheric electrical environment shows that this technology can be employed to produce reliable measurements of the atmospheric conduction current; however, some of the reported measurements exhibit a possible deviation in performance, some of which can be explained by our analysis. The solution for the conducting spheroid is further developed in the appendix to obtain additional results. Analytical solutions are found for the electric field, conductor charging, and current measurements when the polar conductivities are unequal. Electric field enhancement factors for spheroids and approximate solutions for spheroids and other elongated objects are given. The distribution of induced charge along the axis of spheroids is shown to be linear and the solution indicates a similar induced charge distribution along all long conductors. The theory indicates that the 45° cone of protection rule probably overestimates the area protected by tall conductors.
Ozone in the boundary layer of the equatorial Pacific Ocean
Authors: Piotrowicz Stephen R. , Boran Deborah A. , Fischer Charles J.
Published: February 2008

Shipboard (∼7 m) ozone measurements made in the equatorial Pacific Ocean between 20°N and 17°S and 140°–160°W confirm the existence of a distinct ozone minimum in the vicinity of the equator in the late spring, its decline in the summer, and its absence in autumn. This minimum could not be correlated with high biological activity in surface waters. Coincident aircraft measurements of ozone from near sea surface (50–100 m) to 2 km in altitude were made along 150°W at stations at 10°N, 0°, 5° and 12°S in May–June 1984. Aircraft data identified the existence of a distinct ozone maximum between the lifting condensation level (LCL) or cloud base (Zb) and the trade wind inversion, with ozone mixing ratios amounting to 2–2.5 times the ozone levels in the well‐mixed subcloud layer. A gradient of decreasing ozone with decreasing altitude extended from the LCL (or Zb) to the near‐surface superadiabatic region but did not include it.
A numerical model for sulfur and nitrogen scavenging in narrow cold‐frontal rainbands: 1. Model description and discussion of microphysical fields
Authors: Rutledge Steven A. , Hegg Dean A. , Hobbs Peter V.
Published: February 2008

Chemical processes involving sulfur and nitrogen species in clouds and precipitation have been incorporated into a diagnostic, two‐dimensional numerical model for narrow cold‐frontal rainbands (NCFR). The chemical species include sulfur dioxide, sulfate, ammonium, nitric acid, hydrogen peroxide, and peroxyacetyl nitrate. The model is initialized through specification of the airflow field, a temperature‐humidity sounding, and initial profiles of the various chemical species. Outputs of the model (discussed in detail in Part 2) (Hegg et al., this issue) are the steady state, two‐dimensional fields of the mass mixing ratio of various chemical species (e.g., cloud water sulfate or nitrate, precipitation sulfate, or nitrate). In view of similarities between NCFR and moderately strong convective systems, this model should also be useful in diagnostic studies of the sulfur and nitrogen chemistry of a variety of convective clouds and storms.
Solar variability due to sunspots and faculae
Authors: Chapman G. A.
Published: February 2008

Results of photometry of solar active regions and their effect on the solar irradiance in the visible part of the spectrum are presented. The effects of sunspots and faculae are given separately, since the measurement of sunspot irradiance fluctuations is less uncertain. It is argued that energy balance may exist between sunspot deficits and facular excesses. The uncertainty however, is ±15% (1σ). This possible balance also depends on the correct mathematical model for the contrast of faculae as a function of position on the solar disk. Extreme Limb Photometer (ELP) data are presented in such a way as to show that the model for facular limb darkening is consistent with the assumptions inherent in the irradiance modeling. The ELP data support the notion that energy balance between spots and faculae is possible. It is emphasized that even if there is energy balance, there will still be variations in the solar irradiance at the earth.