bluuebunny/crossref_metadata_2025 huggingface dataset:
Sources of Atmospheric nitrous oxide from combustion
Authors: Hao W. M. , Wofsy S. C. , McElroy M. B. , Beer J. M. , Toqan M. A.
Published: February 2008

Emissions of nitrous oxide (N2O) have been analyzed from industrial boilers and from a large experimental combustor burning natural gas, oil, or coal. Production of N2O and production of NOx were observed to be correlated, with an average molar ratio of 0.58:1 (N2O‐N: NO). The content of fuel nitrogen plays an important role in determining emissions of both N2O and NOx. In conventional single‐stage combustors, about 14% of fuel nitrogen is converted to N2O and 24% is converted to NOx. Conversion of fuel nitrogen to N2O was much less efficient (2–4 %) in a two‐stage experimental combustor and in wood fires. A model is presented describing emissions of N2O globally, from the beginning of the industrial revolution to the present. Combustion of fossil fuel is estimated to release 3.2×106 tons N2O (as N) y−1 at present, with 83% of this derived from burning of coal in large industrial boilers. The biospheric source of N2O is calculated as 8.8×106 t y−1. The tropospheric concentration of N2O in 1860 is estimated to have been 280.7 ppb. We expect that concentrations of N2O should rise more than 20% to about 367 ppb by the year 2050, based on conservative projections of world energy consumption.
Measurement of methane and other light hydrocarbons in the troposphere and lower stratosphere
Authors: Aikin A. C. , Gallagher C. C. , Spicer C. W. , Holdren M. W.
Published: February 2008

The volume mixing ratios of methane, acetylene, ethane, and propane were measured in the troposphere and stratosphere on April 5, 1984, at 33°N, over New Mexico, using the technique of grab sampling by evacuated spheres on a balloon platform. Following recovery, analysis was carried out in the laboratory. The evacuated sphere technique was also employed to obtain a tropospheric sample from Catherine Peak, New Mexico (2.86 km altitude). Tropospheric volume mixing ratios were CH4, 1.59 ppm; C2H2, 358 ppt (parts per trillion); C2H6, 365 ppt; and C3H8, 1440 ppt. In the stratosphere, acetylene was 60 ppt. For ethane and propane the mixing ratios at 11.6 km were 441 ppt and 84 ppt, respectively.
Effects of radiative processes in thin cirrus
Authors: Starr David O'C.
Published: February 2008

Results of four numerical simulations of convective thin cirrus are presented. Midday and nighttime cases at subtropopause (−60°C) and lower (−35°C) levels are considered. Each case is weakly forced by large‐scale ascent. Radiative processes are shown to strongly regulate the convective structure and ice water budget of the cloud (30% denser at night). Day‐night differences result primarily from radiative modulation of buoyancy and the resultant differences in the organization of convection. The nature of this coupling between radiative processes and cloud circulations is discussed. The direct effects of radiative heating or cooling on the saturation vapor pressures are found to be of secondary importance in these convective cases.
The Pacific marine aerosol: Evidence for natural acid sulfates
Authors: Clarke Antony D. , Ahlquist Norman C. , Covert David S.
Published: February 2008

Optical, chemical, and physical measurements of marine boundary layer aerosol were made during two oceanographic cruises in the central Pacific in the fall of 1983 and spring of 1984. Both cruises revealed a ubiquitous accumulation mode atmospheric aerosol that showed marked increases in the region of equatorial upwelling, 4°N to 15°S, between Hawaii and Tahiti. Changes in the aerosol size distribution in response to thermal conditioning revealed properties consistent with those of sulfuric acid and/or ammonium sulfate/bisulfate depending upon the sampling location. Changes in the apparent acidity of the accumulation mode varied in conjunction with physical and chemical properties of the region sampled, while the number concentration suggests that it is the dominant and possibly limiting aerosol for cloud condensation nuclei in the remote central Pacific.
Global circuit variability from multiple stratospheric electrical measurements
Authors: Norville Kent , Holzworth Robert
Published: February 2008

In this paper we have examined the vertical component of the electric field, conductivity, and the derived current density from eight superpressure balloons. Special emphasis was placed on the fair‐weather, simultaneous measurements from widely spaced constant‐altitude (26 km) balloons. The conductivity measurements were well organized by a simple ionization rate parameterization depending on the geomagnetic latitude. The variability of all the electrical parameters was found to be independent of the balloon separation. Much of the time the current density measurements were within 20%, for simultaneous flights, even though the balloons were up to 6000 km apart. Also, these simultaneous current density data show that the global current source was significantly variable on hourly and daily time scales. Finally, the use of the simultaneous current density data are discussed as a possible “geoelectric index.” Advantages and limitations of such an index are discussed.
Relationships between available potential energy, kinetic energy, and extratropical cyclone activity within East Coast cyclogenetic regions
Authors: Zapotocny John V.
Published: February 2008

Interrelationships between the available potential energy and kinetic energy associated with extratropical cyclones are examined for portions of the First GARP Global Experiment (FGGE) year. The study is confined to the cyclogenetically active regions encompassing the eastern coasts of Asia and North America. Calculations of vertically integrated available potential energy (APE) and kinetic energy (KE) are done for an active winter storm period (February 14–28, 1979) and a relatively inactive summer period (July 1–15, 1979) using gridded isentropic data produced from the FGGE Level IIIa set of global analyses. During both the winter and summer study periods, good agreement is indicated between cyclone tracks and the spatial distributions of time mean and standard deviations of vertically integrated APE and KE. Energy distributions composited for rapidly strengthening and weakening storms show the patterns of available potential energy and kinetic energy which are associated with cyclones in these stages of development. The rapidly intensifying storms are accompanied by strong gradients in APE equatorward of the surface cyclone with maximum KE to the south and southwest of the storm center. Smaller values of kinetic energy and weaker gradients of available potential energy accompany the rapidly decaying storms. An examination of twice daily distributions of APE and KE for 29 individual cyclones reveals that a similar temporal evolution of vertically integrated energy patterns accompanies storms in these east coast regions. An example of this evolution is presented in conjunction with a case analysis of the February 1979 Presidents' Day cyclone along the east coast of North America.
Assessment of a class of Neyman‐Scott models for temporal rainfall
Authors: Foufoula‐Georgiou Efi , Guttorp Peter
Published: February 2008

Neyman‐Scott type cluster point processes have been used in several studies to model temporal rainfall at a single location. In this paper we study the applicability of such models with the rainfall thought of as instantaneous bursts at the points of the Neyman‐Scott process. We find that this class of models does not provide adequate fit to some observed rainfall series. We also discuss some estimation problems associated with the fitting procedure, and examine the importance and appropriateness of the distributional assumptions made in the modeling.
Upward streamers produced by a lightning strike to radio transmission towers
Authors: Krider E. Philip , Wetmore Ralph H.
Published: February 2008

A lightning strike to the center of three 78‐m radio transmission towers produced upward discharges with lengths of 40 and 79 m from each of the neighboring towers. This strike also caused a number of insulators on guy wires that supported the tower to flash over, and the locations of these points and the two‐dimensional geometry of the discharge channels are projected onto a vertical plane that is centered on the tower.
Chemical composition of fresh snow on Mount Everest
Authors: Jenkins Mark D. , Drever James I. , Reider Richard G. , Buchanan Thomas
Published: February 2008

One hundred freshly fallen snow samples were collected from the north side of Mount Everest between 5600 and 7100 m elevation in April and May of 1986. Compared to snow from the Rocky Mountains of Wyoming, the Everest samples have lower sulfate and nitrate concentrations, reflecting a lesser anthropogenic input and much higher calcium concentrations and pH. The calcium concentrations and high pH presumably reflect a large but variable input of calcium carbonate dust either from arid areas to the west and north or from more local glacial deposits.
The role of electric space charge in nuclear lightning
Authors: Williams Earle R. , Cooke Chathan M. , Wright Kenneth A.
Published: February 2008

The phenomenon of nuclear lightning is reexamined with theoretical models and laboratory‐scale experiments. It is shown that the distribution of electric space charge, rather than the electric field alone, must be considered in accounting for the shapes and locations of nuclear lightning channels in the atmosphere. A self‐consistent distribution of space charge requires a consideration of both electronic and ionic conduction in the irradiated atmosphere, in agreement with earlier findings (Grover, 1980). The magnitudes of nuclear lightning currents (105–106 A) (Colvin et al., 1987) are compatible with predictions for electrical conduction currents based on contemporary theory. Comparisons between the theoretical predictions and laboratory discharge experiments for the nuclear lightning case emphasize the dominant influence of electric space charge on discharge paths in both solid insulators and thunderclouds.
On the fundamental solution of the radiative transfer equation
Authors: Flatau Piotr J. , Stephens Graeme L.
Published: February 2008

This paper outlines the general solution of the one‐dimensional, azimuthally averaged radiative transfer equation in terms of a matrix exponential. The link between this fundamental solution and those more commonly used in radiative transfer is established. The formulation is developed for a general vertically inhomogeneous atmosphere with sources. Several new concepts, based on properties of the matrix exponentials, are described in the context of radiative transfer, including the use of the commutator and product integrals. It is also demonstrated how the matrix exponential formulation provides for new insights, not only into improvements of the numerical efficiency and stability of the solution, but also into the understanding of radiative transfer through a layered atmosphere. The various concepts introduced in this paper are illustrated throughout by the two‐stream simplification of the general radiative transfer equation.
The eddy transport of nonconserved trace species derived from satellite data
Authors: Smith Anne K. , Lyjak Lawrence V. , Gille John C.
Published: February 2008

The two‐dimensional transport of conserved tracers by planetary waves results from two processes: dispersion and organized nondispersive advection. For nonconserved quantities an additional transport mechanism is the chemical eddy effect. This paper is concerned with the latter, which depends on spatial variation in the production and loss of a trace species and can occur in the absence of dispersion. A simple and commonly used form of representing the eddy flux is as a transport matrix multiplied by the mean gradient. Such a matrix is often called a diffusion matrix, although with off‐diagonal components it can represent transport across, as well as parallel to, the mean gradient. The two‐dimensional transport matrix in this form can, with the assumptions of linearity, stationarity, and a simple form of production and loss, be derived from the eddy tracer continuity equation. We have computed the chemical eddy contribution to the components of the matrix from LIMS satellite observations, using specified photochemical damping time scales. The dominant (Kyy) component of the transport matrices for several winter months are given for ozone, nitric acid, and quasi‐geostrophic potential vorticity (PV). The parameterized transports for these three species are compared with the “exact” transports, computed directly from the eddy LIMS data. The results indicate that the chemical eddy effect can account for most of the observed ozone transport in early winter, decreasing to less than half in late winter. The agreement between the parameterized and observed nitric acid and PV fluxes is not as good. In the lower stratosphere the observed eddy fluxes (the “exact” fluxes) for ozone and nitric acid exceed the parameterized chemical eddy fluxes by a substantial margin. This may be because dispersion, which is not included in the parameterization, is the primary mechanism for eddy transport in that part of the atmosphere. Other reasons that might explain the discrepancies between the parameterized chemical eddy fluxes and the observed fluxes are the inability of a simple flux‐gradient relation to characterize the transport, the approximations made in the calculation of the transport matrix, the inaccuracies in the specified damping times, or the problems with the observed (“exact”) eddy fluxes, which can be sensitive to errors in the wave data.
Measurements of stratospheric columns of nitric oxide made with Zeeman Modulator Radiometer during MAP/GLOBUS 1985
Authors: McKenzie R. L. , Peskett G. D. , Roscoe H. K.
Published: February 2008

Results of observations made with the Zeeman Modulator Radiometer (ZMR) at a high‐altitude observatory during the MAP/GLOBUS NOx campaign in September 1985 are presented. These results show unexpected short‐term variabilities in the NO column above 25 km. Possible causes for these are discussed. These variations are filtered out in hourly averages, which show NO columns that typically increase from 2×1015 molecule cm−2 shortly after sunrise to an afternoon maximum of 3×1015 molecule cm−2, followed by a small decrease in the late afternoon. These columns are similar from day to day over the 3‐week observation period. The observed column amount of NO and its diurnal variability are consistent with the predictions of the Cambridge one‐dimensional diurnal photochemical model. Observations of NO2 imply that when the likely mesospheric contribution to the NO column is considered, the measured and predicted NO/NO2 column ratios are in agreement.
Electric field pulses in close lightning cloud flashes
Authors: Bils John R. , Thomson Ewen M. , Uman Martin A. , Mackerras David
Published: February 2008

Electric field pulses, their times of occurrence in the flash, and their relationship to slower electric field variations were studied for lightning cloud flashes at a distance of about 10 km in Florida. Large pulses with a width of a few microseconds tended to occur more frequently early in the flash. If only pulses with amplitudes greater than 50% above the system noise and widths greater than 1.6 μs were counted, 58% of 332 pulses in 89 flashes occurred in the first third of the field records, while only 14% occurred in the final third. The mean total flash duration was 660 ms. The 31 largest pulse peaks (those with amplitudes more than 3 times the system noise) in six flashes that were analyzed in detail had a median 30–90% risetime of 1.0 μs. The 25 pulses in which these peaks occurred had a median half width of 2.7 μs and had mean full widths, including the positive overshoot, of 74 μs. All these pulses were of negative polarity and were superimposed on negative‐going field changes. Most occurred in the first third of the overall field change. In the latter part of these six records, microsecond‐scale field variations were more than 50% above the tape noise (effectively 4 V/m) in only nine of 49 K changes. Not all pulses associated with K changes had the same polarity as the K change, and their pulse structure was relatively complex in contrast to the negative pulses that occurred early in the records. We infer that the process that produces the K change pulses is different from that which produces the large pulses that occur earlier in the discharges.
Comparisons of satellite ozone data in the lower stratosphere for 1978/1979
Authors: Remsberg Ellis E. , Wu Chung‐Yu
Published: February 2008

Lower stratospheric zonal mean ozone distributions are compared in both hemispheres from the Nimbus 7 Solar Backscattered Ultraviolet (SBUV) (version 5) and Limb Infrared Monitor of the Stratosphere (LIMS) data sets. Generally, there is very good agreement with regard to individual profile shape and magnitude and with their longitudinal variability about the zonal mean. When the data are considered in terms of Umkehr layer amounts, there are subtle but significant differences in the respective meridional ozone gradients and their variations with time. These differences do not seem to be related to SBUV diffuser plate drift effects because differences are not apparent in the upper stratosphere and because they are pronounced in late spring to summer of both hemispheres of the lower stratosphere. It appears more likely that the differences are related to a changing ozone optical depth (LIMS) and constraints to an assumed profile climatology in the retrieval (SBUV). Stratospheric Aerosol and Gas Experiment (SAGE) satellite ozone results are also presented for April 1979 at 10, 16, and 30 mbar, and they tend to split the differences between SBUV and LIMS. Additional comparisons with electrochemical concentration cell (ECC) sonde and Mastsonde ozone profiles are presented in an attempt to sort out the more noticeable differences. At tropical latitudes, LIMS ozone is too large in layer 4; no measurements were available for layer 3. SBUV is too high in layer 3. Layer 5 results are not conclusive, but LIMS appears high by about 10% while SBUV appears low by a similar percentage. At higher latitudes (38°–55°N) of the northern hemisphere, ECC and Mastsonde comparison results are not accurate enough to differentiate between SBUV and LIMS in layer 5, even though there are persistent differences in the satellite data of the order of 10–15%. LIMS ozone is about 10% larger than balloon values in layer 4 during northern hemisphere spring. Both SBUV and LIMS are too high in layer 3. The sign of the SBUV/LIMS satellite differences changes with latitude in layers 4 and 5, and the differences in layer 4 approach 20% at mid‐latitudes during late spring and summer. The May SBUV/LIMS differences at 30°N are similar to the SBUV/ECC differences found at Palestine, Texas (32°N) in the June 1983 Balloon Ozone Intercomparison Campaign (BOIC) I ozone intercomparison. All of this means that annual variations in the SBUV and LIMS satellite ozone data and their meridional gradients in the middle to lower stratosphere must be judged as only qualitative at this time.
Solar irradiance between 2000 and 3100 Angstroms with spectral band pass of 1.0 Angstroms
Authors: Anderson G. P. , Hall L. A.
Published: February 2008

A new estimate of solar irradiance in the wavelength range 2000–3100 Angstroms at 1‐Å resolution has been developed from stratospheric balloon measurements. This “top of the atmosphere” extrapolated spectrum derives from measurements made by two separately calibrated detector assemblies mounted within the same spectrometer optical train, one at 0.12‐Å resolution between 2000 and 2370 Å, the other at 1.0‐Å resolution between 2000 and 3100 Å. The resulting composite spectrum exhibits excellent spectral repeatability, with an instrumental wavelength accuracy of better than 0.25 Å and relative precision of better than 3%. The final radiometric error estimate is 10–12%, based on both the absolute calibration (∼10%) and the extrapolation procedures (1–5%). Comparisons with other recent measurements of the solar irradiance are generally within these error bars.
Numerical simulation of visibility degradation due to particulate matter: Model development and evaluation
Authors: Pilinis Christodoulos
Published: February 2008

The model presented predicts visibility degradation due to aerosol, using thermodynamic equilibrium calculations and Mie theory. Observed scattering coefficients bsca at Mead View, Nevada, are successfully predicted. The model is used to examine the dependence of bsca on certain changes in the ambient sulfate concentrations, as well as the sensitivity of bsca to the ambient relative humidity. The model predicts that aerosol water plays an important role in the visibility degradation at relative humidities higher than the deliquescent point of the aerosol particles. We have also shown that reduction in the ambient sulfate levels does not necessarily result in improvements in the ambient visibility, unless it is accompanied by reductions in the ambient nitrate concentrations.
Nitrogen oxides produced from lightning
Authors: Franzblau Edward , Popp Carl J.
Published: February 2008

Independent measurements of nitrogen oxides (NOx = NO + NO2) were made in proximity to lightning using both a chemiluminescent NOx analyzer and an absorption spectrometer (COSPEC) tuned to the NO2 absorption at Langmuir Laboratory (elevation 3300 m), near Socorro, New Mexico. COSPEC data obtained from three separate lightning events, two from distant storms and one from direct observation of the plume from a single flash a few hundred meters away, yielded 4 to 10 × 1026 molecules NO2/flash after normalizing to flashes at sea level. Measurements from the NOx analyzer during two different thunderstorms indicated that the ratio of NO to NOx can remain high (0.7–0.8±0.1) for several minutes after a flash. Combining the data from the COSPEC with the NOx analyzer yields a production rate of approximately 3×1027 molecules N0x/flash. If 100 flashes/second is an assumed global lightning flash frequency, this production rate becomes 100 TgN/yr (TgN/yr = 1012 g nitrogen/yr) as an order of magnitude estimate.
Intensity and line width measurements in the ν4 fundamental band of 13CH4
Authors: Varanasi Prasad , Chudamani Sury
Published: February 2008

Intensities and collision‐broadened line widths have been measured in the ν4 fundamental band of 13CH4 at 295 K, employing the Doppler‐limited spectral resolution of a tunable diode laser spectrometer and a 13C‐enriched sample of CH4. H2, He, Ar, N2, O2, and air were chosen as the broadening gases in order to provide the data needed in atmospheric and planetary atmospheric applications.
Charge transfer during multiple large ice crystal interactions with a riming target
Authors: Keith W. D. , Saunders C. P. R.
Published: February 2008

Laboratory studies of charge transfer between ice crystals and riming soft hailstones (graupel) have been extended using ice crystals of several hundred micrometers in diameter. The sign of the charge transfer is affected by cloud water content and temperature, being positive to soft hailstones at temperatures higher than about −18°C with typical values of cloud liquid water content. The d4 dependence of charge transfer on crystal size reported previously for smaller ice crystals decreases with larger crystals. The new data can be included in numerical models of thunderstorm electrification.
Characteristics of magnetic field pulses in Earth lightning measured by the Galileo Probe instrument
Authors: Rinnert K. , Lauderdale R. , Lanzerotti L. J. , Krider E. P. , Uman M. A.
Published: February 2008

A lightning‐measuring instrument designed for the Galileo Probe mission to Jupiter has monitored the magnetic field signals of Earth lightning for several years. The instrument performs spectral measurements in the narrow‐band channels at 3, 15, and 90 kHz (frequency domain) and waveform measurements (time domain) in the band 0.1–100 kHz. In the time domain the instrument accumulates statistical distributions of pulse amplitude, pulse duration, and interpulse interval or gap time during a preset measuring period. The largest amplitude waveform that occurs during the measuring period is also digitized for a window of 1 ms. This paper summarizes the time domain statistics that were made during four storms that exhibited low to moderate lightning rates. Waveforms are presented that appear to be typical cloud discharge waveforms, and their characteristics are presented. For individual pulses or pulse bursts, the mean interpulse gap time and duration time were found to be 74 and 42 μs, respectively. On the average, bipolar pulses were found to be asymmetric, with the ratio of the amplitude of the first half cycle to the second half cycle being 1.4. The evaluation of the waveform statistics shows that the instrument does provide statistics that are representative of terrestrial intracloud and cloud‐to‐ground discharges. A minimum was found around 100 μs in the gap time distribution of waveform pulses in several studied storms. During one local storm, a periodicity was observed in the lightning pulse rate. The pulse activity was modulated within a broad envelope that peaked every 2–3 min. This modulation may be an indication of the existence of locally active charge regions that have lifetimes of a few minutes.
Nucleation and particle formation in the upper atmosphere
Authors: Keesee R. G.
Published: February 2008

In the high latitudes of the summer mesopause, temperatures can be sufficiently cold that the region becomes strongly supersaturated in water at ambient vapor concentrations around a part per million by volume. With supersaturation, water vapor can be removed from the vapor phase to form and grow cloud particles. Meteoric dust and ions are suspected to be the dominant sources of nuclei upon which water can collect. The development of ice particles from cores of meteoric dust involves a process known as heterogeneous nucleation. Particle formation promoted by ionic nuclei is called ion‐induced nucleation. The formalisms for these two competitive mechanisms and their application to conditions of the summer polar mesopause are reviewed. Results suggest that both processes are feasible mechanisms for initiating noctilucent cloud formation. However, because calculated nucleation rates are highly uncertain, the predominance of one or the other nucleation mechanism for noctilucent cloud formation cannot be unambiguously established.
The effect of spatial resolution upon texture‐based cloud field classifications
Authors: Welch R. M. , Navar M. S. , Sengupta S. K.
Published: February 2008

The previous cloud classification investigations in parts 1–3 of this study have been conducted using 1/16‐km Landsat Multispectral Scanner (MSS) imagery. However, for global monitoring, much lower spatial resolutions of the order of 1–8 km generally are used. The present study examines the loss of cloud classification accuracy as a function of spatial resolution by degrading the imagery through progressive averaging. Textural measures are computed using the Gray Level Difference Vector approach. Significant improvement in cloud classification accuracy can be obtained using 1/2‐km spatial resolution data rather than the current 1‐km resolution data available today from AVHRR and GOES. Cirrus classification accuracy is especially compromised as the spatial resolution is degraded. However, the use of texture measures defined at the combination of pixel separations d = 1, 4 improves classification accuracies by several percent even for 1‐km spatial resolution data. Cirrus accuracy is significantly improved by use of multiple distance features. Classification accuracies using 1/8‐km spatial resolution data are similar to those obtained using the full spatial resolution features. The implications are that there are no advantages to be gained in cloud classification accuracies by using even higher spatial resolutions available from Landsat Thematic Mapper or SPOT imagery. Finally, it is found that multiple resolution imagery can be used to improve classification accuracy. Indeed, the “global” rather than the “local” aspects of texture appear to be most important to the classifier.
Photochemistry of CO and H2O: Analysis of laboratory experiments and applications to the prebiotic Earth's atmosphere
Authors: Wen Jun‐Shan , Pinto Joseph P. , Yung Yuk L.
Published: February 2008

The role photochemical reactions in the early Earth's atmosphere played in the prebiotic synthesis of simple organic molecules was examined. We have extended an earlier calculation of formaldehyde production rates to more reduced carbon species, such as methanol, methane, and acetaldehyde. We have simulated the experimental results of Bar‐Nun and Chang (1983) as an aid in the construction of our photochemical scheme and as a way of validating our model. Our results indicate that some fraction of CO2 and H2 present in the primitive atmosphere could have been converted to simple organic molecules. The exact amount is dependent on the partial pressure of CO2 and H2 in the atmosphere and on what assumptions are made concerning the shape of the absorption spectra of CO2 and H2O. In particular, the results are most sensitive to the presence or absence of absorption at wavelengths longward of 2000 Å. We also find that small quantities of CH4 could have been present in the prebiotic Earth's atmosphere as the result of the photoreduction of CO.
A class of unusual lightning electric field waveforms with very strong high‐frequency radiation
Authors: Willett J. C. , Bailey J. C. , Krider E. P.
Published: February 2008

The first wideband dE/dt recordings have been obtained for the narrow bipolar pulses previously identified by Le Vine (1980) as “sources of the strongest RF radiation from lightning.” These dE/dt waveforms are dramatically different from those of other known lightning processes. A burst of high‐frequency “noise” is superimposed on the slower bipolar pattern one might expect from the relatively smooth E waveforms. For 18 such pulses from an isolated thunderstorm cell at known range, the mean peak E and dE/dt, range‐normalized to 100 km, were 8.0±5.3 V/m and 20±15 V/m/μs, respectively. Spectral analysis indicates that the sources of these pulses radiate much more strongly than first‐return strokes at frequencies from 10 MHz to at least 50 MHz. Absolutely calibrated power and energy spectra are presented which are reliable from 200 KHz to perhaps 20 MHz. At 18 MHz the narrow pulses appear to contain nearly 16 dB more spectral energy than first return‐stroke waveforms from the same range. Supporting evidence shows that they generally occur as isolated pulses in intracloud flashes but are not associated with K changes or other known phenomena. They can occur in either polarity.
Measurements of nitric oxide and total reactive nitrogen in the Antarctic stratosphere: Observations and chemical implications
Authors: Fahey D. W. , Murphy D. M. , Kelly K. K. , Ko M. K. W. , Proffitt M. H. , Eubank C. S. , Ferry G. V. , Loewenstein M. , Chan K. R.
Published: February 2008

Measurements of nitric oxide, NO, and the sum of reactive nitrogen species, NOy, were made as part of the Airborne Antarctic Ozone Experiment (AAOE) on flights of the NASA ER‐2 aircraft over the Antarctic continent. Reactive nitrogen species include NO, NO2, NO3, N2O5, HNO3, and ClONO2. The technique utilized the conversion of NOy components to NO on a gold catalyst and the subsequent detection of NO by the chemiluminescent reaction of NO with O3. NO was measured on two of the flights by removing the catalyst from the sample line. The flights ranged from 53°S to 72°S latitude in the lower stratosphere, with the majority of flights following the 425 K (±10 K) or 450 K (±10 K) potential temperature surfaces. The boundary of a chemically perturbed region (CPR) above the continent occurred on average near 66°S as indicated by a sharp increase in the level of ClO. Outside or equatorward of the CPR, NOy mixing ratios ranged between 6 and 12 parts per billion by volume (ppbv), with values increasing with latitude. At the edge of the CPR, large latitude gradients of NOy and NO were found with values decreasing poleward. Total NOy levels dropped to 4 ppbv or less within 5° poleward of the boundary. NO values were 0.1–0.2 ppbv outside and below the detection limit of 0.03 ppbv inside the CPR. The levels of NO and NOy observed preclude a chemical loss of ozone due to reaction with NO. The NOy values outside the CPR are in accord with the results of two‐dimensional photochemical models that incorporate only homogeneous chemistry when allowance is made for enhanced diabatic descent of air parcels. NO is somewhat lower than the model predictions. Inside the CPR, low NOy values indicate denitrification, defined as the removal of NOy from an air parcel. Low H2O levels, which indicate dehydration, are observed to coincide with denitrification, suggesting that the respective processes are coupled. The partitioning of the remaining NOy inside the CPR likely favors HNO3 and ClONO2. Outside the CPR, the concurrent measurements of ClO, NO, NOy, and O3 along with photochemical steady state relations indicate that NO2 and ClONO2 are minor NOy components. Near the boundary, the variation of NO with ClO is shown to be consistent with heterogeneous reactions of HCl and ClONO2 producing reactive chlorine.
On the sensitivity of a residual circulation model to differences in input temperature data
Authors: Guthrie Paul D. , Jackman Charles H. , Kucsera Tom L. , Rosenfield Joan E.
Published: February 2008

The residual mean circulation (RMC) formulation of zonally averaged transport in the middle atmosphere produces a circulation which depends on the distributions of net diabatic heating and temperature. We have derived such circulations from two temperature data sets, National Meteorological Center (NMC) and Limb Infrared Monitor of the Stratosphere (LIMS), using the same radiative transfer code (Rosenfield et al., 1987). We have used these circulations to transport N2O in a photochemical model. The circulations and the resulting N2O distributions are notably different during the northern hemisphere winter, with that based on the NMC temperatures producing too much upward transport in the tropical stratosphere as judged by comparison with the stratospheric and mesoscale sounder data. The experiment demonstrates that model calculations, in general, and perturbation assessments, in particular, are likely to be quite sensitive to the choice of input temperature data (where this is not computed self‐consistently). It also reveals what appears to be a seasonally dependent bias in NMC zonally averaged temperatures with respect to those obtained from the LIMS instrument during 1978/1979.
Soot in the atmosphere and snow surface of Antarctica
Authors: Warren Stephen G. , Clarke Antony D.
Published: February 2008

Samples of snow collected near the south pole during January and February 1986 were analyzed for the presence of light‐absorbing particles by passing the melted snow through a nuclepore filter. Transmission of light through the filter showed that snow far from the station contains the equivalent of 0.1–0.3 ng of carbon per gram of snow (ng/g). Samples of ambient air were filtered and found to contain about 1–2 ng of carbon per kilogram of air, giving a scavenging ratio of about 150. The snow downwind of the station exhibited a well‐defined plume of soot due to the burning of diesel fuel, but even in the center of the plume 1 km downwind, the soot concentration was only 3 ng/g, too small to affect snow albedo significantly. Measurements of snow albedo near large inland stations are therefore probably representative of their surrounding regions.
A low‐order dynamical model of global climatic variability over the full Pleistocene
Authors: Maasch Kirk A. , Saltzman Barry
Published: February 2008

A previously formulated dynamical model of the late Pleistocene ice ages (based on the hypothesis that the global CO2 system can provide the instability to drive a natural oscillation involving feedbacks between the cryosphere, atmosphere, and ocean) is extended to include (1) additive earth orbital forcing (summer insolation changes at 65°N) and (2) tectonic forcing in the form of a postulated variation in the multiplicative parameters (rate constants) of the model system. The structural (e.g., bifurcation) properties of the model are examined in detail to reveal the regions of parameter space wherein the geologically inferred features of the full Pleistocene can be simulated, including the observed chronology, the phase relationships between ice, CO2, and North Atlantic Deep Water formation, and the mid‐Pleistocene transition.
Estimation of mean rain rate: Application to satellite observations
Authors: Kedem Benjamin , Chiu Long S. , North Gerald R.
Published: February 2008

A method for the estimation of the mean area average rain rate from dependent data is developed and applied to the GARP Atlantic Tropical Experiment GATE data. The method consists of fitting a mixed distribution, containing an atom at zero, by minimum chi‐square in combination with certain time‐space sampling designs. In modeling the continuous component of the mixed distribution it is shown that the lognormal distribution provides a very close fit for the nonzero area average rainrates. A comparison with the gamma distribution shows that the lognormal distribution is a better choice as expressed by the minimum chi‐square criterion. Some of the time‐space sampling designs correspond to satellite sampling. The results indicate that a satellite visiting an area of about 350 × 350 km2 in the tropics approximately every 10 hours over a period can provide a rather close estimate for the mean area average rain rate.
Tuned perfect prognosis forecasts of mesoscale snowfall for southern Ontario
Authors: Burrows William R.
Published: February 2008

A procedure for producing site‐specific 1‐ and 2‐day categorical forecasts of 24‐hour accumulated snowfall by statistical forecast methods has been developed and tested for a small area of Ontario adjacent to southern Georgian Bay. A perfect prognosis (“perfect prog,” or PP) method was used, with predictors designed to handle lake‐effect and nonlake‐effect snowfall. Predictors were selected from a basic set of potential predictors by a stepwise multiple discriminant analysis (MDA) procedure done in three stages, where the third stage involved adding functions of predictors already selected in the first two stages to the basic predictor set. The third stage appears to enhance the discriminating power of the original predictor set because the number of “hits” of snowfall forecasts made with independent data was significantly increased and the distribution of forecasts was brought closer to the observed distribution. A two‐step, rule‐based tuning procedure was applied to the PP‐MDA forecasts to help compensate for errors that arise when the PP‐MDA statistical equations are used with numerical weather prediction model data, and for errors that arise from the conservative nature of MDA forecasts. A rule‐based nonparametric statistical classification procedure (CART) was used in the first step. When the rules for tuning forecasts were tested with independent data, CART was found to increase the skill of the tuned forecasts, particularly in the common categories (1,2), and to improve the reliability of category 1 forecasts at a majority of the stations. However, CART was unable to find rules for infrequent and rare snow categories. Step B of the tuning procedure, a semicomputerized manual search for additional rules not seen by CART, was undertaken in an attempt to “do something” about this problem. When tested with independent data, overall improvement was found in the skill of forecasts tuned by two‐step procedure, but it was too small to make an appreciable difference. Several suggestions are made in regard to exploring methods that should result in significantly improved skill of snowfall forecasts for southern Ontario by statistical forecast methods.
On the role of vibration‐vibration transitions in radiative cooling of the CO2 15 μm band around the mesopause
Authors: Zhu Xun , Strobel Darrell F.
Published: February 2008

We determine the importance of V‐V transitions in the radiative cooling by the CO2 15 μm band near the mesopause where the maximum error in cooling rate by two‐level model is expected to occur. It is shown that the effect of including V‐V transitions is to locally smooth the source functions for different sub‐bands toward a single mean value. This effect allows the changes in cooling rate for each sub‐band to partially cancel each other, so the total change in cooling rate for the whole band is not very significant. It is found that the maximum error in cooling rate around the mesopause is ∼0.5°K day−1. We have also examined errors in the cooling rate of the CO2 15‐μm band for an equivalent two‐level model suggested by Zhu (1990). The maximum error in cooling rate for the equivalent two‐level model is ∼1.3°K day−1 around the summer mesopause. Present calculations confirm that the equivalent two‐level model can be used in GCMs to calculate the CO2 15‐μm band cooling rate.
Formaldehyde production in photochemical smog as predicted by three state‐of‐the‐science chemical oxidant mechanisms
Authors: Dodge Marcia C.
Published: February 2008

A moving box model was used to compare formaldehyde (HCHO) predictions obtained with three photochemical oxidant mechanisms. In simulations using a typical urban mix of organic pollutants, the mechanisms were found to yield HCHO predictions that agreed to within 10% of each other provided the same reaction rates were used in all three mechanisms to describe the photolysis of HCHO. The agreement for simulations using pollutant mixtures containing only one organic species showed more variability. Formaldehyde predictions obtained for ethene, propene, and acetaldehyde were in excellent agreement under most conditions; significant differences, however, were noted for the 2‐alkenes and aromatic hydrocarbons. Predictions of ozone and hydrogen peroxide obtained with the urban mixture were very sensitive to the initial concentration of HCHO included in the simulations. Depending on whether HCHO was assumed to constitute 0% or 2% of the initial mix of organic pollutants, resulting ozone yields varied by as much as 15–30%; hydrogen peroxide yields differed by factors of 4–10 depending on the mechanism used. To estimate the effectiveness of various control measures for limiting HCHO production, simulations were also conducted where individual organic species within the urban mix were reduced and the resulting decreases in HCHO yields were noted. The largest decreases in HCHO occurred for reductions in ethene and the other 1‐alkenes; the smallest decreases were obtained when the monoalkylbenzenes or the alkanes were reduced.
A case study of the Thunderstorm Research International Project storm of July 11, 1978 2. Interrelations among the observable parameters controlling electrification
Authors: Nisbet John S. , Kasha John R. , Forbes Gregory S.
Published: February 2008

In Part 1 of this paper, the data obtained at the time of the Thunderstorm Research International Project storm at the Kennedy Space Center on July 11, 1978, are discussed and analyzed in a model‐independent manner. Here the parameters of the electrical system that would be consistent with these observations are discussed. Three‐dimensional electrodynamic modeling of the thundercloud electrification allowed estimates to be made of the current moments and electrical power generated continuously throughout the evolution of the two cells of the storm that were studied. The evolution and configuration of the currents were consistent with the separation of an originally neutral ensemble of particles by gravity in the region of 7 km in the region close to the maximum of the updraft velocity. After about 370 s the effect of wind shears would have caused the particles to separate in the convective system of the cells. Rain did not appear to be the dominant charge carrier. The current moments generated were compared with the current moments transferred by intercloud and cloud‐to‐ground lightning. It is shown that for the southern cell, which produced a charge moment of about 8.4 (MC m), lightning utilized about 84% of the charge moment separated, while for the northern cell, which produced about 1.1 (MC m), this figure was approximately 60%. It was shown that the times of initiation and maximum electrical power generated corresponded best with the normalized mass above 7.5 km. It was deduced that the median diameter heavier particles had a fall velocity of about 3 m s−1. The generator currents, flash rates, cloud conductivities, and mean charge per flash were used to estimate the volume associated with the lower region of current divergence.
Modification of the energy‐wave number spectrum for heavy proton hydrates as tracers for isotropic turbulence at the summer mesopause
Authors: Hall C. M.
Published: February 2008

An ion‐chemical model for the terrestrial D region is used to investigate the change in degree of hydration for proton hydrates when the summer polar neutral atmosphere is perturbed by a gravity wave. The drastically changing ion composition which results has consequences for the energy‐wave number spectrum of the scalar tracer plasma.
A regional scale model for ozone in the United States with subgrid representation of urban and power plant plumes
Authors: Sillman Sanford , Logan Jennifer A. , Wofsy Steven C.
Published: February 2008

A new approach to modeling regional air chemistry is presented for application to industrialized regions such as the contintental United States. Rural chemistry and transport are simulated using a coarse grid, while chemistry and transport in urban and power plant plumes are represented by detailed subgrid models. Emissions from urban and power plant sources are processed in generalized plumes where chemistry and dilution proceed for 8–12 hours before mixing with air in a large resolution element. A realistic fraction of pollutants reacts under high‐NOx conditions, and NOx is removed significantly before dispersal. Results from this model are compared with results from grid models that do not distinguish plumes and with observational data defining regional ozone distributions. Grid models with coarse resolution are found to artificially disperse NOx over rural areas, therefore overestimating rural levels of both NOx and O3. Regional net ozone production is too high in coarse grid models, because production of O3 is more efficient per molecule of NOx in the low‐concentration regime of rural areas than in heavily polluted plumes from major emission sources. Ozone levels simulated by our model are shown to agree with observations in urban plumes and in rural regions. The model reproduces accurately average regional and peak ozone concentrations observed during a 4‐day ozone episode. Computational costs for the model are reduced 25‐ to 100‐fold as compared to fine‐mesh models.
Tropospheric hydrocarbon and CO profiles over the U.S. West Coast and Alaska
Authors: Greenberg J. P. , Zimmerman P. R. , Haagenson P.
Published: February 2008

Methane, carbon monoxide, and non‐methane hydrocarbons were measured in seven profiles from the boundary layer up to 13 km over the Pacific Ocean off the west coast of the United States and over Alaska in April 1985. Mid‐latitude profiles displayed the altitudinal variability of hydrocarbons and CO in the marine troposphere. Mixing ratios, in general, decreased with increasing altitude. Over Alaska, mixing ratios of hydrocarbons and CO were higher than at mid‐latitudes. Most profiles showed measurable mixing ratios of many hydrocarbons up to the tropopause and suggested that many non‐methane hydrocarbons may be present throughout the troposphere in the northern hemisphere.