bluuebunny/crossref_metadata_2025 huggingface dataset:
The vertical distribution of ozone in the mesosphere and lower thermosphere
Authors: Allen Mark , Lunine Jonathan I. , Yung Yuk L.
Published: February 2008

An assessment is made of the ability of current theory to explain the phenomenology of upper atmospheric ozone as revealed by the sizeable body of measurements presently available. The chemistry of ozone in the mesosphere and lower thermosphere is closely coupled to the chemistries of other oxygen/hydrogen‐containing species, which must be considered concurrently. To provide insight into the sensitivity of model calculations to the choice of values used for key chemical rate constants and climatological parameters, simple analytical expressions for ozone are derived for those situations when it is in photochemical steady state, the mesosphere during daylight hours and the lower thermosphere throughout the full diurnal period. The model is found to reproduce the detailed Aladdin 74 rocket measurements of ozone from 50 to 95 km, numerous other measurements of mid‐latitude ozone in the lower mesosphere, the secondary maximum in the ozone vertical distribution at the mesopause, and the diurnal variability of ozone seen in the radio measurements of Wilson and Schwartz (1981) and other observations. The agreement with the Aladdin 74 data results from adjusting some key parameters within the uncertainties of laboratory measurements or known natural climatological variability. The variety of mid‐latitude observations can be understood in terms of the estimated variability of environmental factors: diurnal, seasonal, and solar cycles in the solar illumination; the abundance of water vapor; and the details of the thermal profile of the atmosphere. The ozone secondary maximum results from the onset of the coupling between active‐hydrogen and active‐oxygen chemistry and its observed variability may be a consequence of secular changes in mesopause dynamics. Above ∼95 km, ozone observations are consistently higher than model results and cannot be accounted for by the set of reactions currently included in the model.
On the temporal variation of stratospheric aerosol size and mass during the first 18 months following the 1982 eruptions of El Chichón
Authors: Hofmann D. J. , Rosen J. M.
Published: February 2008

Baloon‐borne particle counters at Laramie and in southern Texas are used to investigate the size and mass distribution of the aerosol which formed in the stratosphere during the first 18 months following the volcanic eruption of El Chichón. The latter appears to have reached a peak at Laramie in early 1983 and began a decline in May. Measurements of average aerosol radius versus time are used to estimate a sulfuric acid concentration of about 107 cm−3 40 days after the eruption and a net acid vapor lifetime of 25–50 days in the 18–25‐km altitude region.
The Earth Radiation Budget (ERB) Experiment: An overview
Authors: Jacobowitz Herbert , Soule Harold V. , Kyle H. Lee , House Frederick B.
Published: February 2008

The development of ERB observational systems is traced from its beginnings in the late 1950's through to the current ERB on the NIMBUS 7 satellite. The instruments comprising the current 22‐channel ERB experiment are described in some detail. Noteworthy are the inclusion in one solar channel, of a self‐calibrating cavity to measure the solar constant and the use of biaxial scanning telescopes to determine the angular reflection and emission model required for processing the narrow‐angle radiometric data. A fairly detailed description of the prelaunch and in‐flight calibrations is given along with an analysis of the radiometric performance of the instruments. The data processing system is traced with the aid of a schematic flow diagram showing the steps required to produce the many tape and microfilm products archived. Future plans for improving the quality and accuracy of the data products are discussed. Finally, the upcoming Earth Radiation Budget Experiment (ERBE) is briefly mentioned. It will be capable of simultaneously measuring the radiation budget from three satellites, each having a different equator crossing time and angle.
An assessment of NIMBUS 7 ERB Shortwave Scanner data by correlative analysis with narrowband CZCS data
Authors: Davis P. A. , Major E. R. , Jacobowitz H.
Published: February 2008

As a check on calibration adjustment factors, the broadband ERB shortwave scanning channel data from NIMBUS 7 were compared with independent narrowband satellite measurements. This check required the establishment of appropriate broadband‐narrowband radiance relationships, which also become the basis for generating or evaluating radiation budget parameters in either spectral range from data in the other. As a theoretical basis for comparison both broadband and narrowband radiances were simulated from the DAVE dataset of radiative transfer model computations for a variety of angles through several model atmospheres. Spectrally varying reflectances for five basic surface types (vegetations, desert, cloud, water, snow) were introduced along with spectral response functions for narrowband intervals. Linear regression relationships were developed for individual surface types and for the combination of all surface types under identical illumination‐viewing conditions. Empirical relationships were generated from actual matchups of earth radiation budget (ERB) scanner data with coincident data from CZCS channel 5 (0.7–0.8 μm) over a variety of scenes. Since each of the four scanning channels of ERB was compared separately with narrowband data from the same sensor, relative differences were accurately determined from the empirical data. Previously established calibration adjustment factors for the ERB shortwave scanning channels verified, in a relative sense, regardless of surface type, to within 2%.
The validation of NIMBUS 7 LIMS measurements of ozone
Authors: Remsberg Ellis E. , Russell James M. , Gille John C. , Gordley Larry L. , Bailey Paul L. , Planet Walter G. , Harries John E.
Published: February 2008

Approximately
months of stratospheric ozone profiles have been processed from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment on NIMBUS 7. Data profiles cover the stratosphere and mesosphere from 100 to 0.1 mbar and from 84°N to 64°S latitude. The retrieved ozone profiles are not constrained in any way to an initial guess profile or to an ozone climatology. This paper describes the ozone channel characteristics, precision, systematic uncertainties, and comparisons with data from balloon and rocket underflights, Umkehr soundings, and Dobson measurements. Comparisons with Dobson total ozone are made by integrating combined LIMS plus balloon profiles. The estimated on‐orbit precision is 0.02–0.16 ppmv. Simulations of the experiment indicate potential systematic uncertainties ranging from 15% in the 1‐mbar to the 3‐mbar region to an upper limit of 40% at 100 mbar and 0.1 mbar. Comparisons with sets of correlative ozone profiles show mean differences of less than 10% from 7 to 50 mbar for mid‐latitude balloon‐borne sensors and 16% from 0.3 to 50 mbar for rocket data. Such results are well within the uncertainties for the correlative sensors themselves. Agreement with balloon measurements degrades somewhat at tropical latitudes in the lower stratosphere. LIMS detects significant vertical structure in the ozone profile even below the ozone mixing ratio peak. Preliminary comparisons with Umkehr data at four stations show generally good agreement from 1 to 30 mbar. The zonal mean ozone cross section for March 1979 compares well with ozone climatologies reported by Dutsch (1974) and with more recent data obtained for a similar time of year using satellite instruments operating at the much different ultraviolet and visible wavelengths. When taken together with the other LIMS parameters (temperature, H2O, HNO3, and NO2), this new ozone data set can be used to study middle atmospheric processes.
Observation of the CO (J = 6 ← 5) rotational transition in the Earth's upper atmosphere
Authors: Wattenbach R. , Durwen E. J. , Röser H. P. , Schultz G. V.
Published: February 2008

A submillimeter heterodyne receiver with an open structure mixer and a laser local oscillator was used to detect the CO (J = 6 ← 5) absorption transition at 691.473 GHz in the earth's upper atmosphere. Spectra were taken toward the sun with a 1024‐channel acousto‐optical spectrometer. The resolution was 250 kHz. The CO volume mixing ratio profile was calculated from the spectral line shape. It is shown that the CO (J = 6 ← 5) measurement results in a well‐determined CO profile for the lower mesospheric layers, as compared with the results of other authors for observations of CO transitions with lower J values.
Radon 222 and tropospheric vertical transport
Authors: Liu S. C. , McAfee J. R. , Cicerone R. J.
Published: February 2008

Radon 222 is an inert gas whose loss is due only to radioactive decay with a half life of 3.83 days (5.51‐day “exponential” lifetime). It is a very useful tracer of continental air because only ground level continental sources are significant. Thus it is similar in several ways to many air pollutants (e.g., NOx (NO+NO2), SO2, and certain hydrocarbons). Previously published measured 222Rn profiles are analyzed here by averaging for the summer, winter, and spring‐fall seasons. The analysis shows that in summer, about 55% of the 222Rn is transported above the planetary boundary layer, considerably more than during the other seasons. Similarly, in summer, about 20% rises to over 5.5 km (500 mbar). The average profiles have been used to derive vertical eddy diffusion coefficients with maximum values of 5–7×105 cm2 s−1 in the midtroposphere and 8×103 to 5×104 cm2 s−1 near the surface.
Factors affecting exhalation of radon from a gravelly sandy loam
Authors: Schery S. D. , Gaeddert D. H. , Wilkening M. H.
Published: February 2008

Measurements of radon exhalation from a gravely sandy loam have been made in a semi‐arid climate by using a combination of closed accumulation, flow‐through accumulation, and 222Rn and 210Pb soil profiles. The meteorological factors that most affected the instantaneous value of exhalation of 222Rn were atmospheric pressure and rain. Effects due to other parameters such as wind or temperature were either comparatively small or undetectable. No evidence was seen for migration of radon from distant (≫10m) sources or for an effect on exhalation due to limited nearby seismic activity. Measurements for 220Rn indicated its exhalation was also sensitive to pressure variation but to a lesser extent than for 222Rn. While instantaneous exhalation of 222Rn could easily vary by a factor of 2 or more, time‐averaged exhalation was found to be close to that expected for pure diffusion. There is thus some indication that the time‐averaged effect of cyclic environmental variables is small for this soil. Comparison with transport equations indicates that it is difficult to explain the observed variation in surface flux density solely in terms of the radon concentration gradient in the top few decimeters of soil. A contribution to transport from direct flow, perhaps through inhomogeneities such as cracks or channels, is one possible explanation.
An analysis of the annual cycle in upper stratospheric ozone
Authors: Frederick J. E. , Serafino G. N. , Douglass A. R.
Published: February 2008

The mid‐latitude upper stratospheric ozone profiles obtained by the solar backscatter ultraviolet instrument on the Nimbus 7 satellite show a clear annual cycle both in the absolute ozone amounts between 0.98 and 15.6 mbar and in the magnitude of disturbances that reveal themselves as longitudinal structure. At the lowest pressures analyzed a winter maximum in ozone exists, but as one progresses downward in altitude a shift in the temporal phase of the annual cycle occurs in the vicinity of 3 to 4 mbar. Comparison of the observed behavior with the predictions of a one‐dimensional photochemical model shows a systematic tendency for calculated ozone amounts to be 20–27% below the data for pressures less than 7.8 mbar. The chemical model successfully predicts the change in phase of the annual cycle, although at a pressure greater than observed. Diagnosis of model results shows the observed shift to be closely coupled to the magnitude of the ozone column density near 3–4 mbar. The wavelength‐dependent attenuation of the solar radiation field by ozone alters the relative magnitude of the molecular oxygen and ozone dissociation rates, leading to a change in the temporal phase of the annual cycle.
Estimates of the transport of trace metals from the ocean to the atmosphere
Authors: Weisel C. P. , Duce R. A. , Fasching J. L. , Heaton R. W.
Published: February 2008

The Bubble Interfacial Microlayer Sampler (BIMS) was used in the North Atlantic to determine the enrichment factors, relative to sodium and the ocean (EFsea), for a series of trace metals on bubble‐derived atmospheric sea salt particles. No enrichment was found for K and Mg within the analytical precision of ±10%. Mean EFsea values determined for Al, Co, Cu, Fe, Mn, Pb, V, and Zn ranged from 10 to 20,000. Positive correlations were found between bubble generation depth and the EFsea values for Fe, Pb, Sc, and Zn. Estimates suggest that the ocean is the primary global source of atmospheric K and Mg, that it is potentially a nontrivial (5–20% of the total) source of atmospheric Cu, V, and possibly Zn, and that it is an insignificant source of Al, Co, Fe, Mn, Pb, and Sc. In the remote North Pacific, during certain periods of the year, the ocean may be the primary source for all these elements present on aerosol particles with diameters greater than ∼3 μm.
Diurnal variation of ClO: Implications for the stratospheric chemistries of ClONO2, HOCl, and HCl
Authors: Ko Malcolm K. W. , Sze Nien Dak
Published: February 2008

Numerical results are presented for the diurnal variations of stratospheric species, including the chlorine species. The calculated diurnal variation of the column density of stratospheric chlorine monoxide (ClO) appears to be in good agreement with the recent measurement obtained from ground‐based millimeter‐wave spectroscopy. The observed large diurnal variation of the column density of ClO above 30 km can be understood in terms of various exchange processes between ClOx (Cl+ClO) and the temporary chlorine reservoirs (ClONO2 and HOCl). The rapid early morning rise in the column density of ClO above 30 km is mainly attributed to photolysis of ClONO2, whereas its continual decrease during the nighttime may be attributed to the recombination of ClO with NO2, forming ClONO2 as the major product. The predicted diurnal behavior of the upper stratospheric ClO, however, is mainly due to the exchange between ClOx and HOCl. Observation of the diurnal behavior of ClO in the upper stratosphere can place important constraints on the chemistry of HOCl.
Measurements and parameterization of particulate sulfur dry deposition over grass
Authors: Wesely M. L. , Cook D. R. , Hart R. L. , Speer R. E.
Published: February 2008

Eddy correlation measurements of participate sulfur fluxes at the 1981 and 1982 Dry Deposition Intercomparison Experiments indicate a strong diurnal variation in deposition velocity (downward flux divided by concentration, at a height near 6 m). Most of the run‐to‐run variability for data collection periods of 30 min seems to be due to unwanted sensor noise. Systematic changes of fluxes wth height due to possible advection from strong point sources of sulfur can occur but should be quite small. A parameterization for deposition velocity is derived in terms of friction velocity u* and the Obukhov stability length scale L. When the parameterization is applied in conjunction with nearly continuous measurements of mean micrometeorological variables such as wind speed and temperature difference, the resulting long‐term mean deposition velocity found is 0.22±0.06 cm/s with a variation greater than ±50% from day to day, depending on local atmospheric conditions. Peak deposition velocities greater than 0.5 cm/s occur on windy afternoons. Such values are considerably greater than suggested from wind‐tunnel and theoretical investigations, but are similar to past results obtained by use of the same techniques over lush vegetation. Boundary layer convective motions that increase wind gustiness near the surface seem to increase particle deposition velocities considerably. Relatively small deposition velocities are found in neutral and stable atmospheric conditions or over surfaces that lack complex fine structure.
The influence of continental ice sheets on the climate of an ice age
Authors: Manabe S. , Broccoli A. J.
Published: February 2008

The climate influence of the land ice that existed 18,000 years before present (18K B.P.) is investigated by use of a general circulation model of the atmosphere coupled with a static mixed layer ocean. Simulated climates are obtained from two versions of the model: one with the land ice distribution of the present and the other with that of 18K B.P. In the northern hemisphere the tropospheric flow field is strongly influenced by the Laurentide ice sheet and features a split flow straddling the ice sheet, with a strong jet stream forming the southern branch. The northern branch of the flow brings very cold air over the North Atlantic Ocean, where thick sea ice is maintained. The distribution of sea surface temperature (SST) difference between the two experiments in the northern hemisphere resembles the difference between the SST at 18K B.P. and at present, as estimated by the CLIMAP Project (1981). The 18K B.P. ice sheets have very little influence upon atmospheric temperature and SST in the southern hemisphere. This is because the interhemispheric heat transport hardly changes as the loss of heat energy due to the reflection of solar radiation by continental ice sheets in the northern hemisphere is almost completely counterbalanced by the in situ reduction of upward terrestrial radiation. Hydrologic changes in the model climate are also found, with statistically significant decreases in soil moisture occurring in a zone located to the south of the ice sheets in North America and Eurasia. These findings are consistent with some geological evidence of regionally drier climates from the last glacial maximum.
Sensitivity of a thermodynamic sea ice model with leads to time step size
Authors: Ledley Tamara Shapiro
Published: February 2008

A thermodynamic sea ice model numerically structured to take time steps on the order of a week is found to be sensitive to time step size when new ice formed on open ocean is assumed to cover the ice‐free area. This sensitivity is caused by the extrapolation of initial ice growth rates on open ocean, which can be very high, over the length of the time step. The sensitivity to time step size is tremendously reduced when the parameterization for the formation of new ice is altered so that the new ice thickness is specified. However, the sensitivity continues during the winter, when the area of open ocean is small because the volume of ice formed over the time step is more than enough to fill the open area at the specified thickness. Therefore ice thickness during the winter is again determined by time step size. Suggestions are made on how the sea ice model's sensitivity to time step size can be further reduced without sacrificing computational efficiency.
Finite field of view effects on inversion of limb thermal emission observations
Authors: Abbas Mian M. , Guo Jing , Conrath Barney J. , Kunde Virgil G. , Maguire William C.
Published: February 2008

The effects of finite field of view of observing instruments on the inversion of infrared thermal emission measurements are examined. Analytical and numerical techniques are discussed for calculation of the weighting functions and for retrieval of temperature and constituent distributions from thermal emission observations with a finite field of view. Calculations and plots of the weighting functions with various instrumental fields of view are presented. Results for retrieval of temperature and constituent profiles from synthetic limb radiance data with a finite field of view are given.
Interannual variations in the height of the tropical tropopause
Authors: Reid George C. , Gage Kenneth S.
Published: February 2008

Radiosonde data obtained over the past 30 years from nine tropical stations have been analyzed to investigate the variability in height of the tropical tropopause on interannual time scales and on hemispheric spatial scales. A high degree of spatial coherence was found to exist among the stations, indicating that the tropical tropopause responds to large‐scale driving forces as well as to local influences. The tropopause height was found to have a significant dependence on the phase of the quasi‐biennial oscillation in the zonal winds of the tropical stratosphere and on the sea surface temperature anomalies of the tropical Pacific Ocean (the El Nino/Southern Oscillation phenomenon). A strong positive correlation between tropical tropopause heights and solar activity, reported earlier by several authors, is shown to have been transitory and possibly coincidental. The implications of these results are discussed. A comparison of tropopause height/temperature and height/saturation water vapor mixing ratio relationships at Yap and Curacao is consistent with suggestions that the western tropical Pacific is an important source region for stratospheric water vapor.
Lightning return stroke electric and magnetic fields
Authors: Uman Martin A.
Published: February 2008

Our present understanding of the microsecond‐ and submicrosecond‐scale electric and magnetic fields generated by lightning return strokes is reviewed. First, the experimental data for strokes lowering both negative and positive charge are discussed. Then theory relating the remotely measured fields to the channel currents is presented. The significant gaps in our understanding of the return stroke fields are identified.
The response of ozone to solar proton events during solar cycle 21: A theoretical interpretation
Authors: Jackman Charles H. , McPeters Richard D.
Published: February 2008

Substantial ozone decreases at the stratopause and in the Mesosphere have now been observed by instruments on the NIMBUS 7 solar backscattered ultraviolet (SBUV) and Solar Mesosphere Explorer (SME) satellites during solar proton events (SPE's) of solar cycle 21. Since the ozone depletion was only observed during the SPE's, we believe that increased production of short‐lived HOx species by protons is responsible for the depletion. We find that one‐dimensional time‐dependent model calculations are close to agreement with the two satellite instrument measurements in the upper stratosphere and lower Mesosphere only when the observed ozone decrease as a function of altitude is used in our model calculations. Most of the ozone depletion between 2 and 0.5 mbar (∼45 and 55 km) was caused not by direct particle effects, but by the large ozone decreases at higher altitudes allowing increased penetration of ultraviolet to lower than normal altitudes. Our calculations are qualitatively in agreement with the SBUV measurements but tend to underestimate the ozone depletion for pressure levels between 1 and 0.3 mbar (∼50 and 60 km). The calculated ozone depletions at 0.5 and 0.3 mbar (∼55 and 60 km) agree fairly well with the observations of SME. The strong solar zenith angle (SZA) dependent depletion that was observed is predicted by the model. Larger SZA's generally reflected larger ozone depletions. However, for SZA's greater than 84° during the July 13, 1982, SPE an ozone decrease less than the ozone decrease at 84° SZA and 1 mbar (∼50 km) was predicted by theory and observed in SBUV data. Similar behavior was observed in three other SPE's. As far as we know, this ozone response is the first reported evidence for the much discussed self‐healing effect.
Two‐dimensional tracer transport: Derivation of residual mean circulation and eddy transport tensor from a 3‐D model data set
Authors: Pitari Giovanni , Visconti Guido
Published: February 2008

Two‐dimensional distributions for long‐lived species, N2O, CFCl3, and CF2Cl2, have been calculated by using a 2‐D model extending from the ground to 70 km. The model utilizes a residual mean meridional circulation and a set of eddy diffusion coefficients. Both these fields have been obtained from the output of the MIT‐GIT three‐dimensional general circulation model of the stratosphere. The calculation of the residual mean circulation takes into account consistent fields of temperature and diabatic heating, meridional temperature advection, and vertical eddy fluxes. The diffusion tensor is obtained following Holton (1981) and utilizes the eddy field that is an output of the 3‐D model. The chemical source term is treated by introducing an additional tensor, following the suggestion by Tung (1982). This approach has the advantage of using the same matrix for all the chemical compounds. Values obtained for the residual mean meridional mass flux are in good agreement with similar results. The trace gas distributions obtained show a fairly good agreement in the equatorial regions but overpredict the concentration in the mid‐latitude stratosphere. This is a common modeling problem, especially with fluorocarbons, and is attributed, in our case, to values of the Kyy and Kzz components that are too large in the lower stratosphere. This particular result is probably due to the heating parameterization adopted in the original general circulation model.
A volcanic ash transport model and analysis of Mount St. Helens ashfall
Authors: Hopkins Arthur T. , Bridgman Charles J.
Published: February 2008

A model is presented to compute the transport and deposition of volcanic ash particles. Calculations use variable winds along the particle trajectories. The model was exercised by performing numerical experiments with data from the May 18, 1980, eruption of Mount St. Helens, Washington. Ashfall arrival times, location of grounded ash, a particle size distribution, and particle size sorting across the grounded ash lobes were calculated and compared to observations. Agreement was generally found, except for the particle size distribution. The calculated size distribution contained particles that were larger than measured particle sizes. This result supports the speculation made by others that falling aggregates break during landing and subsequent measurement.
Application of a boundary‐layer model to flow over an eolian dune
Authors: Walmsley John L. , Howard Alan D.
Published: February 2008

As part of a larger project to model sand transport over isolated dunes and the temporal evolution of such dunes the present paper describes a wind flow simulation that results from an application of the MS3DJH/1.5 model (Walmsley et al., 1982) to the dune studied by Howard et al. (1978). A comparison is made between the calculations and observations of surface wind direction and wind speed at 80 cm above terrain on the upwind side of the dune. The mean error and rms deviation from the mean error, respectively, are about 0.2° and 7° for surface wind direction and −9.09 and 0.08 for normalized wind speed.
Structure of the katabatic winds at Mizuho Station, East Antarctica
Authors: Ohata Tetsuo , Kobayashi Shun'ichi , Ishikawa Nobuyoshi , Kawaguchi Sadao
Published: February 2008

The structure of katabatic wind at Mizuho Station (70°42′S 44°20′E, 2230 m above sea level) in East Antarctica is described using data from radiosondes and a 30‐m tower. This station is characterized by a so‐called “cold katabatic” region. The frequency of occurrence of a single wind direction (in this case, east) is higher at Mizuho than at any other station in Antarctica. Because of this and the strong wind, well‐developed sastrugi can be seen in the vicinity. The characteristics of the temperature inversion during clear sky conditions in winter were a quasi‐isothermal layer from the surface up to 50 m capped by a thermocline of stronger temperature gradient. The maximum wind speed occurred near this height. The height of the top of the boundary layer, where turbulence becomes quite small, can be considered as the height above this thermocline. The d value of the stable boundary layer obtained by using the above height was 0.048–0.19 in the present case. This value is lower than the values obtained on the flat horizontal surface and on a slope of 0.002 m km−1 in the mid‐latitudes. Taking the above height as the top of the katabatic wind, the two‐layer model including the surface friction can explain the observational results well, better than the inversion wind model. This seems to indicate that the surface stress is important in the development of the katabatic wind at Mizuho but that the interfacial stress at the top of the inversion layer is not important in its development.
Interpretation of ozone temperature correlations: 2. Analysis of SBUV ozone data
Authors: Douglass Anne R. , Rood Richard B. , Stolarski Richard S.
Published: February 2008

In an effort to understand the behavior of ozone in the transition region, the terms in the perturbation continuity equation have been evaluated from solar backscattered ultraviolet ozone data, National Meteorological Center temperature data, and geostrophic winds derived from the temperature data at 2 mbar, winter 1978–1979. A linear parameterization is used to estimate the chemical source term. The perturbation ozone field calculated by integrating the net forcing evaluated from the data compares well with the measured perturbation ozone field. There are occasions during the winter when the sum of the dynamic terms is small due to cancellation, and the ozone and temperature perturbations are anticorrelated. The −1 correlation between the ozone and temperature perturbations does not necessarily imply that chemical forcing is dominant.
Stratospheric hydrogen peroxide: The relationship of theory and observation
Authors: Connell Peter S. , Wuebbles Donald J. , Chang Julius S.
Published: February 2008

Current theory of stratospheric photochemistry indicates that the photochemical lifetime of hydrogen peroxide (H2O2) is short enough in the middle stratosphere (1 day) that the H2O2 abundance can be considered to be photochemically controlled. However, H2O2 should still be expected to show significant temporal and spatial variability through its sensitivity to transport‐related fluctuations in O3, NOy (=NO + NO2 + HNO3 + HNO4), and H2O. From the available observational data on short‐term variability in these longer‐lived species, H2O2 concentrations should vary temporally four‐ or fivefold at altitudes between 15 and 35 km. This concentration range about the model profile includes two recently reported upper limits for mid‐stratospheric H2O2. The earlier tentative identification of stratospheric H2O2 by Waters et al. (1981) is somewhat larger than the expected upper limit of variation based on a one‐dimensional transport‐kinetics model. Several implications for stratospheric observation of H2O2 arise from its expected variability. Model‐predicted H2O2 abundances are very sensitive to important kinetic parameters, but small sets of H2O2 measurements alone will not be useful to test model behavior. In concert with simultaneous measurements of O3, H2O, and NOy, H2O2 abundances could be used to closely verify model treatment of HOx( = HO + HO2) photochemistry. Finally, the HOx abundance and its partitioning between HO and HO2 are quantities of great importance in the chemistry of the mid and lower stratosphere. Inference of these values from H2O2 and some other independent quantity related to HOx involves knowledge of only a small set of photochemical parameters and could supplement direct observation of the radical species.
Total chlorine content in the lower stratosphere
Authors: Gallagher Charles C. , Forsberg Charles A. , Mason Allen S. , Gandrud Bruce W. , Janghorbani Morteza
Published: February 2008

A cryogenic whole air sampler and a filter sampler were used, simultaneously, on a balloon platform to capture and preserve all significant stratospheric chlorine species with the exception of Cl and ClO at altitudes of 15, 20, 25, and 30 km. The whole air samples were analyzed by gas chromatography to determine mixing ratios of CF2Cl2, CFCl3, CH3Cl, CH3CCl3, and CCl4. Liquid extractions of the filter samples were analyzed for acidic and particulate chlorine content using neutron activation and wet chemistry techniques. Summation of the contributions from the major species produced total chlorine mixing ratios that decreased from 2.6 ppbv at 15 km to 2.2–2.5 ppbv for the higher altitudes. Omission of Cl and ClO introduced about a 3–7% error at 25–30 km and negligible error at 15 and 20 km. The combined contributions of all other omitted species introduced 1–2% error to the total chlorine values for all altitudes investigated. The increase in total acidic species content with increasing altitude correlates with the decrease in the mixing ratios of the chlorine species of tropospheric origin.
A method to correct satellite measurements of sea surface temperature for the effects of atmospheric aerosols
Authors: Griggs M.
Published: February 2008

Multichannel sea surface temperature (MCSST) measurements with the NOAA 7 advanced very high resolution radiometer (AVHRR) have been corrected for the effects of the El Chichon aerosol layer by using a previously developed method of inferring the aerosol optical thickness (τ) from the channel 1 radiance. A theoretical model shows that the error in the MCSST is directly proportional to τ sec θ, where θ is the satellite zenith angle. Data using moored buoy SST's and AVHRR MCSST's at five locations verify this relationship. Analysis of the data also shows empirically that the MCSST error is more closely related to ln (τ sec2θ). Linear regressions for these relationships for the combined data of two locations show correlation coefficients of 0.80 and 0.88 for the τsec θ and ln (τ sec2θ) relationships, respectively. These regression lines are used to correct the MCSST values in the independent data sets of the other three locations. Statistics of the comparison between the corrected MCSST's and the buoy SST's show that the root mean square difference in the MCSST and buoy SST comparison is 1.14°C and 1.01°C for the τsec θ and ln (τsec2θ) relationships, respectively. These values are close to the value of 1.05°C found in an extensive study at NOAA of an earlier MCSST algorithm that was not influenced by aerosols. Before this correction, considerable daytime data were rejected by the MCSST algorithm, and errors as large as 7°C were observed. It appears that the correction procedure can be used in the presence of partial cloud in a pixel, since both the MCSST and the aerosol algorithms interpret the partial cloud as a uniform haze. Thus the technique also results in the retrieval of more MCSST values (than are currently available with the NOAA cloud filter tests) in the presence of clouds in normal aerosol conditions. The technique also offers the potential of increasing the accuracy of MCSST measurements in normal atmospheres where the aerosols are mostly in the troposphere.
A model study of the greenhouse effects due to increasing atmospheric CH4, N2O, CF2Cl2, and CFCl3
Authors: Wang Wei‐Chyung , Molnar Gyula
Published: February 2008

Study of the greenhouse effects of increasing atmospheric trace gases has so far relied mainly on the use of one‐dimensional models, especially the radiative‐convective models (cf. World Meteorological Organization, 1982; National Research Council, 1983). Here we use the two‐dimensional (altitude‐latitude) radiative‐dynamical model of Wang et al. (1984) to investigate the effects on vertical and meridional temperatures of increases of atmospheric methane, nitrous oxide, and chlorofluorocarbons. The model, consisting of a high‐latitude zone and a low‐latitude zone, couples the meridional and vertical temperature structure through energy balance between radiative flux and vertical and meridional heat transports. First, we show that the thermal radiation flux perturbations, i.e., the driving force for the subsequent climate change, caused by increases of these trace gases and carbon dioxide, are different in nature. Next, a comparison of model‐calculated present climate and climate change between the one‐dimensional and two‐dimensional models is performed. The results indicate that the two‐dimensional model simulates much more realistic temperature and humidity distributions. For a doubling of the atmospheric CO2 concentration of 330 parts per million by volume, the two‐dimensional model computes a global surface warming of 3.7 K with larger high‐latitude amplification, which is in good agreement with results obtained from general circulation models. For the study of the surface warming due to increases of trace gases, it is found that the one‐dimensional model using a 6.5 K km−1 critical lapse rate for convective adjustment appears to calculate a much larger surface warming than the two‐dimensional model. On the other hand, the one‐dimensional model using the moist adiabatic critical lapse rate, although it can not simulate adequately the present tropospheric temperature structure, calculates surface warming effects in close agreement with those of two‐dimensional model results. We have used the two‐dimensional model to estimate on the time scale of decades the potential greenhouse effects due to increases of these gases. Although the calculations depend largely on the adopted scenarios for future increases, the results nevertheless reveal that the trace gases could potentially augment the surface warming due to carbon dioxide increase by more than 60%.
Positive ion composition of the high‐latitude summer D region with noctilucent clouds
Authors: Kopp E. , Eberhardt P. , Herrmann U. , Björn L. G.
Published: February 2008

Positive ion composition and electron and total positive ion densities were measured on July 30 (S26/1) and August 13 (S26/2), above Kiruna as part of a multinational rocket campaign to study noctilucent clouds (NLC). Two magnetic ion mass spectrometers took measurements at altitudes of 65–126 km in twilight at times of very low magnetic activity and of NLC sightings at 82.5–83.4 km. The hydration order of the most abundant proton hydrates increased with height from n = 3 below 76 km to n = 6 and n = 5 at 88 and 87 km, respectively. Temperatures inferred from ion composition revealed a minimum of 104° + 20°K at 90.5 km. At this altitude a special ion spectrum with heavy proton hydrates up to H+(H2O)12 was measured, which seems to indicate the possibility for ice particle formation through ion nucleation in a narrow layer. The composition measurements were also used to infer mesospheric concentrations of nitric oxide, water vapor, and hydrogen peroxide. The water vapor mixing ratio in the NLC region was found to be around 3 parts per million by volume.
Energy balance constraints on gravity wave induced eddy diffusion in the mesosphere and lower thermosphere
Authors: Strobel Darrell F. , Apruzese John P. , Schoeberl Mark R.
Published: February 2008

Breaking gravity waves generate and maintain a background level of turbulence which is capable of producing substantial cooling and/or heating in the upper mesosphere and lower thermosphere. The net thermodynamic effect of breaking gravity waves is critically dependent on the eddy Prandtl number (Pr) applicable to mesospheric turbulence. When Pr ∼ 1, our calculations of the heat budget for the mesopause region imply that the globally averaged eddy or turbulent diffusion coefficient cannot exceed 106 cm2 s−1. This upper limit on turbulent diffusion applies to both potential temperature transport and chemically inert tracer transport when radiative damping is negligible. For chemically active species, larger diffusion coefficients are permitted because the effective eddy diffusion coefficient is increased by an additive term L/2γ2, where L is the chemical loss rate and γ is the vertical wave number. For Pr ∼ 4–6, the turbulent diffusion of momentum DM is sufficiently greater than the turbulent diffusion of heat DH that the conversion of gravity wave energy to heat with high efficiency nearly balances the divergence of the downward eddy heat flux in the wave breaking zone. Therefore the heat budget of the mesopause region would no longer provide a powerful and useful constraint on DH. If Pr exceeds 6 with high efficiency for energy conversion to heat, gravity waves would heat the mesosphere throughout the wave breaking region.
Wave‐turbulence interaction in the stratosphere: A case study
Authors: Cot C. , Barat J.
Published: February 2008

We present simultaneous in situ measurements of a long‐period inertio‐gravity wave and of clear air turbulence events associated with wave propagation. The energy budget of the wave‐turbulence interaction shows that a wave of long period and of short vertical wavelength may propagate upward over several wavelengths close to the shear instability conditions. This result allows one to interpret the spatiotemporal structure of CAT layers as reported in the literature and in particular their horizontal and vertical extent, their thickness, and their persistence.
A global three‐dimensional model of the circulation and chemistry of CFCl3, CF2Cl2, CH3CCl3, CCl4, and N2O
Authors: Golombek Amram , Prinn Ronald G.
Published: February 2008

An efficient three‐dimensional spectral model is used to investigate the tropospheric and stratospheric circulation, chemistry, and photochemistry of the long‐lived atmospheric species CFCl3, CF2Cl2, CH3CCl3, CCl4, and N2O. The model uses precalculated three‐dimensional spectral fields of vorticity, vertical velocity, temperature, and ozone concentration and current estimates of the magnitudes and distributions of industrial and natural sources of the various species. Explicit calculations of instantaneous photodissociation rates for each species are carried out, and reactions with atmospheric OH and O(1D) and dissolution in the ocean are also included in the model where relevant. Available measurements of the horizontal, vertical, and temporal distribution of the modeled atmospheric species generally compare favorably with our calculations. However, there are some disagreements, particularly between the observed and calculated surface distributions of CH3CCl3 and the vertical distributions of CCl4, which are critically discussed. Assuming that their destruction is dominated by photodissociation and reaction with O(1D), the calculated present‐day global atmospheric lifetimes of CFCl3, CF2Cl2, CCl4, and N2O are 73, 210, 48, and 182 years, respectively. Decreasing the O2 absorption cross sections in the Schumann‐Runge continuum (2000–2200 Å) by 40% results in a decrease of the CFCl3 lifetime to 44 years. The calculated atmospheric lifetime of CH3CCl3 due to photodissociation and reaction with OH and O(1D) is 12 years, but this result depends on the prescribed seasonally dependent zonally invariant OH distribution used in the model.
Acetonitrile in the stratosphere and implications for positive ion composition
Authors: Arijs E. , Brasseur G.
Published: February 2008

The present paper describes a probable budget for acetonitrile and discusses the release of this gas through biomass burning and human activity. The different loss processes in the middle atmosphere are mainly due to the reaction with hydroxyl radicals and atomic oxygen. It is shown that the destruction of CH3CN by scavenging due to precipitation is probably not more efficient than the direct gas phase reactions. Losses due to ion chemistry are very difficult to estimate at present but are probably of secondary importance, except locally, where formation of multi‐ion complexes is significant. A one‐dimensional calculation shows that the vertical profiles of CH3CN, deduced from ion mass spectrometry data, can be reproduced satisfactorily if an annual global emission ranging from 1.5 × 1010 g to 5 × 1011 g is adopted, depending on the values of the reaction rate constants and eddy diffusion coefficient. The global atmospheric lifetime of CH3CN is estimated to be about 0.5 to 1.4 years. Finally, the calculated acetonitrile profiles are introduced in an ion model to calculate the abundances of the major positive stratospheric ions. The results are consistent with present observations.
Monochromatic calculations of atmospheric radiative transfer due to molecular line absorption
Authors: Chou Ming‐Dah , Kouvaris Louis
Published: February 2008

Sensitivity studies related to the effects of line cutoff, spectral resolution, and temperature and pressure interpolations in radiative transfer have been performed so that a data set of absorption coefficients for water vapor, CO2, and O3 may be created efficiently. Results show that computations of absorption coefficients are affected only slightly by cutting a line off at a wave number 190 times the Lorentz half width from the center, or, equivalently, cutting off 0.33% of the line intensity from the wings. To achieve a relative cooling rate error smaller than 2%, it is sufficient to precompute the absorption coefficient at three temperatures (210, 250, and 290 K) and 19 pressures with Δ(log10 p) = 0.2. The absorption coefficient at other conditions can be interpolated linearly with pressure and exponentially with a quadratic in temperature. For the spectral resolution the absorption coefficients can be adequately computed at 0.01, 0.002, 0.005, and 0.025 cm−1 intervals in the thermal water vapor, the CO2 and O3 bands, and the solar water vapor bands, respectively, which limits the error to only a few percent in the cooling and heating rates. Using the precomputed absorption coefficients, repeated monochromatic calculations of atmospheric heating/cooling rates for radiation model developments and for comparison with less detailed calculations are no longer difficult.
Distribution and geochemistry of aerosols in the tropical north Atlantic troposphere: Relationship to Saharan dust
Authors: Talbot R. W. , Harriss R. C. , Browell E. V. , Gregory G. L. , Sebacher D. I. , Beck S. M.
Published: February 2008

The spatial distribution and water‐soluble chemical composition of aerosols in the tropical North Atlantic troposphere were examined during the NASA Global Tropospheric Experiment/Atlantic Boundary Layer Experiment (GTE/ABLE 1) conducted in the vicinity of Barbados, West Indies. During the June 1984 study period the atmospheric aerosol at 1.5–3.5 km altitudes, the region composing the so‐called Sahara air layer, consisted primarily of Saharan dust. The aerosol mass concentration reached 400 μg (m3 STP)−1 in the mainstream of a massive Saharan dust outbreak which passed through the longitude of Barbados between June 13 and 18, 1984. Measurements of the particle size distribution of the Saharan dust indicated that about 85% of the mass was contained in the 1‐ to 8‐μm diameter range; a distribution that was consistent among the three dust outbreaks observed during ABLE. Enrichment of water‐soluble aerosol chemical species in Sahara air compared to clean tropospheric air at >4 km altitude, ranged from about tenfold for NH4+ to more than a factor of 400 for NO3−. Calculations suggest that Saharan dust represented a significant source of airborne NO3−, non‐sea‐salt SO42−, and PO43− in boundary layer air over the tropical North Atlantic. Estimates of the annual input of Saharan dust‐related chemical species to the equatorial Atlantic suggested that deposition of mineral aerosol to oligotrophic surface waters may be an important source of the nutrient species NO3− and PO43−. This atmospheric input probably occurs principally in the form of dry deposition.