bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflectance characteristics of uniform Earth and cloud surfaces derived from NIMBUS‐7 ERB
Authors: Taylor V. Ray , Stowe Larry L.
Published: February 2008

Data from the scanning channels of the NIMBUS 7 Earth Radiation Budget (ERB) experiment are combined with other data on earth surface conditions and cloudiness. Patterns of bi‐directional reflectance are constructed from this data for uniform earth and cloud surfaces. Examples are shown that illustrate the bi‐directional properties of surfaces and how these properties vary with solar zenith angle (SZA). Dependence of albedo on SZA is also shown. Conclusions may be summarized as follows: (1) Water surfaces exhibit limb brightening at all SZAs; (2) cloud and land surfaces change from limb darkening to brightening as SZA increases; (3) the land surface exhibits higher backward reflection for SZAs less than about 50°; (4) all of the surfaces in this study become more specular as SZA increases; (5) snow is the most nearly isotropic of these surfaces; (6) snow albedo shows very little variation with SZA and even shows a slight decrease over a limited range; (7) albedo generally increases with increasing SZA for other than snow surfaces; (8) angular patterns for high water and ice clouds are quite similar, but ice clouds are more nearly isotropic; (9) the angular patterns developed in this study are in qualitative agreement with those from other investigations.
Validation of water vapor results measured by the Limb Infrared Monitor of the Stratosphere Experiment on NIMBUS 7
Authors: Russell James M. , Gille John C. , Remsberg Ellis E. , Gordley Larry L. , Bailey Paul L. , Fischer Herbert , Girard Andre , Drayson S. Roland , Evans Wayne F. J. , Harries John E.
Published: February 2008

The LIMS experiment on NIMBUS 7 used the technique of thermal infrared limb scanning to sound the composition and structure of the upper atmosphere. One of the LIMS channels was spectrally centered at 6.9 μm to measure the vertical profile and global distribution of stratospheric water vapor. This paper describes the characteristics of and data from the water vapor channel and the steps taken to validate results. The mean difference between LIMS measurements and data from 13 balloon under‐flights is about 0.6 ppmv with LIMS mixing ratios biased high with respect to in situ data. This difference is of about the same order as the estimated LIMS accuracy and is less than the sum of the errors for LIMS and the balloon techniques. The precision measured in orbit is 0.2–0.3 ppmv, and the accuracy, based on computer simulations, is estimated to be 20–30% over the range from 50 mbar to about the stratopause. The vertical distribution in the tropics shows the presence of a hygropause where the mixing ratio decreases to a minimum above the tropopause and then increases with altitude. In extratropical regions, the profile is nearly constant with height and has a value of about 5 ppmv. An unexplained diurnal variation exists in the data which is largest at the 1‐mbar level (1–2 ppmv) and virtually nonexistant at 10 mbar. Day values are higher than night. Until this phenomenon is better understood, caution must be used in drawing conclusions about the H2O altitude behavior in the upper stratosphere. An anti‐correlation exists in the fine structure of the vertical water and temperature profiles. This is brought about primarily by small temperature errors and should not be taken as real. For this and other reasons, more confidence is placed in zonal mean distributions averaged over several days rather than in single profiles. A zonal mean pressure‐latitude cross section is described for January.
Intercomparison of NIMBUS 7 solar backscattered ultraviolet ozone profiles with rocket, balloon, and Umkehr profiles
Authors: Bhartia P. K. , Klenk K. F. , Fleig A. J. , Wellemeyer C. G. , Gordon D.
Published: February 2008

A global ozone data set covering the two years from November 1978 until October 1980, with an average of 1200 profiles per day, has been produced and archived from the solar backscattered ultraviolet (SBUV) instrument flown on the NIMBUS 7 spacecraft. The SBUV ozone profiles are compared with measurements from chemical and optical sensors launched on balloons and rockets and with ozone profiles obtained from the ground‐based Dobson spectrophotometers using the Umkehr method. The biases between the SBUV results and the balloon and Umkehr results are generally less than 10%. These biases are functions of layer height and latitude and are believed to be largely due to inconsistencies in the ozone absorption cross sections used for the various measurement systems. The precision of the SBUV measurements is found to be better than 8% for pressures between 1 and 64 mbar and better than 15% from 64 to 253 mbar.
Observations of CH4 and N2O by the NIMBUS 7 SAMS: A comparison with in situ data and two‐dimensional numerical model calculations
Authors: Jones R. L. , Pyle J. A.
Published: February 2008

Monthly mean, zonal mean measurements of CH4 and N2O for 1979 made by the stratospheric and mesospheric sounder (SAMS) on the NIMBUS 7 satellite are presented for the first time. Comparison with in situ and other available data confirms a general pattern of mixing ratios decreasing with height and of maxima, at a given pressure level, in low latitudes. The SAMS data, by virtue of its extensive coverage, reveals new features. These include during certain months a “double peak” when, along a constant pressure surface, mixing ratio maxima are found in low latitudes of both hemispheres with a local minimum at the equator. In the upper stratosphere are found regions of weak and strong horizontal gradients. Comparison with a two‐dimensional model shows many areas of agreement, especially for CH4, and the model is used to interpret atmospheric behavior. The model overestimates the observed N2O in the upper stratosphere. This is investigated in terms of a possible underestimation of the photochemical sink. We believe strongly, however, that uncertainties in transport representation cannot be ruled out.
Retrieval of temperature and composition from NIMBUS 7 SAMS measurements
Authors: Rodgers C. D. , Jones R. L. , Barnett J. J.
Published: February 2008

A general purpose stochastic sequential estimator is described, which allows the inverse problem of remote sounding to be solved in an optimum manner. The use of a sequential estimator allows continuity in the horizontal or in time to be included, making the a priori estimate close to the final solution, so that iteration is not required. The scan pattern in which measurements are made is not used and need not be known, so that the problem of spacecraft attitude stability is minimized. The method gives both a solution profile and its error covariance. It is applied to both temperature and composition sounding from a limb scanning instrument, the SAMS on NIMBUS 7.
SAGE and SAM II measurements of global stratospheric aerosol optical depth and mass loading
Authors: Kent G. S. , McCormick M. P.
Published: February 2008

Several volcanic eruptions between November 1979 and April 1981 have injected material into the stratosphere. The SAGE and SAM II satellite systems have measured, with global coverage, the 1‐μm extinction produced by this material and examples of the data product are shown in the form of global maps of stratospheric optical depth and altitude‐latitude plots of zonal mean extinction. These data, and that for the volcanically quiet period in early 1979, have been used to determine the changes in the total stratospheric mass loading. Estimates have also been made of the. contribution to the total aerosol mass from each eruption. It has been found that between early 1979 and mid‐1981, the total stratospheric aerosol mass increased from a background level of approximately 570,000 metric tons to a peak of approximately 1,300,000 metric tons.
A comparative study of aerosol extinction measurements made by the SAM II and SAGE satellite experiments
Authors: Yue Glenn K. , McCormick M. P. , Chu W. P.
Published: February 2008

SAM II and SAGE are two satellite experiments designed to measure stratospheric aerosol extinction using the technique of solar occultation or limb extinction. Although each sensor is mounted aboard a different satellite, there are occasions when their measurement locations are nearly coincident, thereby providing opportunities for a measurement comparison. In this paper, the aerosol extinction profiles and daily contour plots for some of these events in 1979 are reported. The comparisons shown in this paper demonstrate that SAM II and SAGE are producing similar aerosol extinction profiles within their measurement errors and that since SAM II has been previously validated, these results show the validity of the SAGE aerosol measurements.
Reaction kinetics of O + ClO → Cl + O2 between 252–347 K
Authors: Schwab James J. , Toohey D. W. , Brune W. H. , Anderson J. G.
Published: February 2008

A discharge flow system with laser magnetic resonance (LMR), resonance fluorescence (RF), and resonance absorption (RA) detection axes is used to study the kinetics of the title reaction. Pseudo‐first‐order decays of O in excess ClO and of ClO in excess O agree very well and yield a rate constant of (3.5±0.5)×10−11 cm3 molecule−1 s−1 near 300 K, with no discernable temperature dependence over the range 252–347 K. Both reactants, and for some experiments the Cl atom product, are detected directly with high sensitivity. Experiments are done both in helium and in argon, and the cited uncertainties include an estimate of systematic errors at the 2σ or 95% confidence level. Results are compared with other recent work, and implications of the somewhat slower rate constant on the chlorine‐induced destruction of O3 in the stratosphere are considered.
Observational results on the vertical column abundance of atmospheric hydroxyl: Description of its seasonal behavior 1977–1982 and of the 1982 El Chichon Perturbation
Authors: Burnett Clyde R. , Burnett Elizabeth Beaver
Published: February 2008

The OH vertical column abundances measured with the Pepsios spectrometer from the National Oceanic and Atmospheric Administration Aeronomy Laboratory's Fritz Peak Observatory (40°N, 105°W) for the 1977–1982 period are presented. Analysis of the ground state absorption shows a general seasonal variation of 28% with maximum in January and minimum in July. An A.M.‐P.M. asymmetry in the observations is found which has a 27% seasonal reversal, which is in phase with total ozone. A unique perturbation of +30% is found for summer 1982 OH abundances, which is attributed to the El Chichon eruption in April 1982.
An upper limit for stratospheric hydrogen peroxide
Authors: Chance K. V. , Traub W. A.
Published: February 2008

We present measurements of an altitude‐dependent upper limit for stratospheric hydrogen peroxide that is substantially lower than previously determined limits. The data were obtained with a remote‐sensing far‐infrared spectrometer during a balloon flight on 23 January 1983. Our 2 sigma upper limit is 0.05 ppbv near 26.5 km, and is larger above and below that altitude. This new upper limit is compared with two currently available modelling calculations for H2O2; in the neighborhood of 32 km, it is slightly lower than, but comparable to these theoretical profiles. The implications for measurement of H2O2 at different latitudes and seasons are briefly discussed.
Long‐period variations in the solar semidiurnal atmospheric tide
Authors: Hamilton Kevin , Garcia Rolando R.
Published: February 2008

A 79‐year record (1866–1944) of hourly surface pressure observations at Batavia (6.2°S, 106.8°E) was analyzed to detect systematic long‐period variations in the solar semidiurnal barometric oscillation (S2(p)). Evidence was found for a quasi‐biennial oscillation (QBO) in S2(p) throughout the latter half of the record (1905–1944). This is attributed to the effect of the familiar QBO of the tropical stratospheric mean winds and temperatures on the solar semidiurnal tide. The results thus suggest that the stratospheric QBO itself has been proceeding in something like its present form since at least the beginning of the twentieth century. Some theoretical calculations were performed of the change expected in S2(p) between the minimum and maximum in the sunspot cycle by employing different published estimates of the solar ultraviolet flux variability. It is clear from the present S2(p) observations that, if there is any regular 11‐year cycle in the solar ultraviolet flux at wavelengths >200 nm, then it must be much smaller than some of the published estimates based on direct flux measurements. However, for periods around two individual sunspot minima (1867 and 1913) there are changes in the Batavia S2(p) consistent with a large drop in solar ultraviolet output.
Boundary layer flow characteristics at the Georg von Neumayer Antarctic Station in summer 1983
Authors: Kottmeier Christoph
Published: February 2008

Based on climatological information over a long period, two case studies of typical flow situations near the Georg von Neumayer station (70°37′S, 8°22′W) are presented. A shallow katabatic layer develops under a small pressure gradient and considerable cooling of the surface layer. In situations with large horizontal pressure gradients, which are more frequent in winter than in summer, the flow is affected by the sloping terrain that leads to the Antarctic plateau. In this case, a marked difference between the temperatures of the air just above the ice shelf and the warmer air from the ocean can be observed within the lowest 45 m.
Solar‐induced oscillations in the stratosphere: A myth or reality?
Authors: Chandra S.
Published: February 2008

The response of the stratosphere to 27‐day variability in solar activity is studied by using ozone and temperature data obtained from the SCR (Selective Chopper Radiometer) and the BUV (backscattered ultraviolet) experiments on Nimbus 4. In the upper stratosphere (∼2 mbar), where solar UV effects are likely to be maximum, the zonally averaged temperature and ozone mixing ratio in the tropics seem to be related to changes in conventional indices of solar activity over several solar rotations. The temperature and ozone are, however, anticorrelated, with temperature varying in phase and ozone out of phase with solar activity. The tropical oscillations appear to be manifestations of oscillations at high latitudes that are very strong during fall‐spring epoch of both the hemispheres. The high‐ and low‐latitude oscillations are almost 180° out of phase with a transition region at mid‐latitudes (30°–40°). Their spectral characteristics and phase suggest a complex interaction of dynamical and chemical processes in the upper stratosphere. This conclusion is further strengthened from the inferred changes in ozone sensitivity with respect to temperature, which shows a continuous decrease from the tropics to high latitudes in both the hemispheres.
An estimate of the effect of El Chichon aerosol on SBUV profiling for summer 1982
Authors: Mergenthaler John L.
Published: February 2008

A case study of the error introduced by the presence of high stratospheric aerosol concentrations into ozone mixing ratio profiles inferred from “simulated measurements” of solar backscattered ultraviolet radiation (SBUV) has been made for the northern tropics (for average stratospheric conditions) during the summer of 1982, a period of unusually high stratospheric turbidity due to the eruptions of El Chichon in the spring. The spectral radiance reflected from the earth's atmosphere was computed for seven wavelengths used in ozone profile recovery by the SBUV instrument. These “simulated measurements,” based on the average July 1979 ozone profile for the 10°–20°N latitude belt and published aerosol optical data, were inverted by a procedure that does not take aerosol scattering or multiple scattering into consideration for the purpose of investigating the accuracy of the aerosol‐free approximation. Comparison is made of the “actual” ozone mixing ratio profile and the inversion solution profiles for aerosol‐free and volcanically perturbed conditions. It is found that the presence of El Chichon aerosol could cause an error in the neighborhood of −25% in the inferred cumulative ozone between zero and 100 mbar if aerosol effects are neglected.
Air‐to‐sea fluxes of lipids at Enewetak Atoll
Authors: Zafiriou Oliver C. , Gagosian Robert B. , Peltzer Edward T. , Alford Jane B. , Loder T.
Published: February 2008

We report data for the Enewetak site of the SEAREX program from the rainy season in 1979. The concentrations of n‐alkanes, n‐alkanols, sterols, n‐alkanoic acids and their salts, and total organic compounds in rain are reported, as well as the apparent gaseous hydrocarbon concentrations. These data and information on the particulate forms are analyzed in conjunction with ancillary chemical and meteorological data to draw inferences about sources, fluxes, and chemical speciations. While the higher molecular weight lipid biomarker components are exclusively terrestrial, the organic carbon in rain may be derived from atmospheric transformations of terrestrial carbon. Distinctively marine components are nearly absent. Comparison of the scavenging ratios of the organic components in rain vs. those for clays reveals that the alkanoic acids and the higher molecular weight alkanols behave as essentially particulate materials, whereas lower alkanols and most hydrocarbons show much higher scavenging ratios, probably due to the involvement of a gaseous phase or sampling artifact. Vaporization in the atmosphere and scavenging of a gas phase would lead to higher scavenging ratios; vaporization during sampling would give low aerosol concentrations and high gas‐phase concentrations, leading to high scavenging ratios. The major fluxes at Enewetak result from rain rather than dry deposition, and extrapolating the measured values to meaningful annual averages requires adjustment for seasonally varying source intensity and rain dynamics. Aerosol data for other seasons and other substances are used to correct for source‐strength intensity variations, and a 210Pb/organic compound correlation is established and extrapolated to adjust for rainfall volume effects. These corrections, assumed independent and applied together, yield inferred fluxes 2.5–9 times larger than the fluxes calculated for mean concentrations. The inferred fluxes to the ocean, while small compared to primary production, are large enough to have potential impacts in the cycle of dissolved organic carbon and the sedimentary geochemistry of refractory lipid components.
Measurement of nitric oxide from 7 to 32 km and its diurnal variation in the stratosphere
Authors: Kondo Y. , Matthews W. A. , Iwata A. , Takagi M.
Published: February 2008

A chemiluminescent balloon‐borne sonde, designed to measure nitric oxide with a high degree of precision, has been developed. Within the framework of the MAP/GLOBUS campaign, the sonde was launched on Septemer 20, 1983, from Aire sur l'Adour, France (44°N, 0°W). The balloon was piloted to perform an excursion from 32 to 22 km during the flight and returned to float at 32 km 1 hour before sunset to enable a sunset study to be made. The first ascent and descent profiles, obtained with solar zenith angles of less than 57° coincided even in detail to within 5% between 22 and 32 km, which not only assured instrumental precision but the unchanging NO mixing ratio during the day. The first ascent profile showed a rapid increase in the NO mixing ratio from 50 pptv at 7 km to 250 pptv at the tropopause indicating a downward transport of NO into the troposphere. After local sunset, the NO concentration was observed to rapidly decrease to 0±10 pptv.
Sensitivity of N2O, CFCl3, and CF2Cl2 two‐dimensional distributions to O2 absorption cross sections
Authors: Jackman Charles H. , Guthrie Paul D.
Published: February 2008

The distribution of the trace gases N2O, CFCl3, and CF2Cl2 is influenced by the O2 absorption cross sections. There has been a recent indication in the literature that the O2 cross sections used in past model studies may overestimate the true values. We have used a two‐dimensional model to perform a sensitivity study on the effects of changes in the O2 cross sections on N2O, CFCl3, and CF2Cl2. Decreases in the O2 cross sections between 180 and 230 nm resulted in altitude‐, latitude‐, and season‐dependent reductions in the computed species' concentrations. The altitude dependence of the reductions at mid‐latitudes agrees qualitatively with similar one‐dimensional model studies (Froidevaux and Yung, 1982; Brasseur et al., 1983). The vertical profiles of CFCl3 are most affected and the vertical profiles of N2O are least affected by the O2 cross‐section changes. The greatest changes in the trace gases occur above 20 km, at high latitudes, and in the winter. In general, the reduced O2 cross sections led to better agreement between model calculations and experimental measurements for all three trace gases; however, there still remain some unexplained differences between observations and model predictions. This result implies that the reduced O2 cross sections may be the better set. The accuracy of the lifetime calculations for the trace gases is not sufficient to recommend either set of O2 cross sections. More precise measurements of O2 absorption cross sections are thus required to determine the true values.
“Nuclear winter”: A diagnosis of atmospheric general circulation model simulations
Authors: Covey Curt , Thompson Starley L. , Schneider Stephen H.
Published: February 2008

We investigate the adiabatic and diabatic thermal balance of an atmospheric general circulation model (GCM) under two conditions: the control case, representing today's atmosphere, and a “nuclear winter” scenario in which virtually all sunlight in northern hemisphere mid‐latitudes is absorbed in the upper troposphere by prescribed dense smoke clouds hypothesized to result from the burning of many cities in a nuclear war. We also examine the changes in moisture and cloudiness simulated by the model. Our object is to examine the reliability of existing simulations of the climatic response to assumed dense, widespread, high‐altitude smoke and to identify improvements needed in model parameterizations. We find that in the smoke‐perturbed case our model simulation of land surface temperature is particularly influenced (i.e., warmed) by parameterized diffusion of heat downward from the lower troposphere. In turn the lower troposphere over land is supplied with heat transported from the relatively warm oceans. Thermal balance in the perturbed atmosphere as a whole is dominated by intense solar heating of the upper troposphere smoke layer in mid‐latitudes balanced by parameterized dry convection and large‐scale dynamical heat transport. Clouds largely disappear in the mid to upper troposphere in smoke‐affected regions as a consequence of a decrease in local relative humidity that results from temperature increases and, to a smaller extent, from a reduction of vertical moisture transport. The computation of substantial downward vertical heat diffusion into the lowest model layer is almost certainly an overestimate for the smoke‐perturbed conditions of high vertical stability. Consequently, the use of the present diffusive parameterization will, in the absence of other errors, result in an underestimate of the magnitude of land surface cooling in the “nuclear winter” scenario. Current three‐dimensional model simulations, however, contain numerous additional omissions and approximations that make it difficult to say whether “nuclear winter” simulations, to date, produce effects that are more or less severe than those that might really occur given the hypothesized smoke amounts and distribution. We believe that the most important areas for GCM enhancement to study climatic effects of nuclear war‐generated aerosols include improved surface and planetary boundary layer processes and incorporation of radiatively active aerosol tracer transport and removal.
Methane flux from coastal salt marshes
Authors: Bartlett Karen B. , Harriss Robert C. , Sebacher Daniel I.
Published: February 2008

The seasonal flux of methane to the atmosphere from salt marsh soils was examined in three different vegetation zones within a single marsh near Yorktown, Virginia. A total of 100 measurements were made over a 2‐year period, with maximum rates occurring during summer and fall. Spatial and temporal variability in fluxes was high; rates ranged from −2.4 to 21.3×10−3 g CH4/m2/d. Estimates of annual methane losses to the atmosphere were 0.43 g CH4/m2 for a salt meadow zone, 1.3 g CH4/m2 for short Spartina alterniflora, and 1.2 g CH4/m2 for tall creek‐bank S. alterniflora. A total of 63 flux measurements, made in a variety of other coastal salt marshes along the east coast of the United States, suggest that the Virginia site may be fairly typical for this region. In addition to diffusional losses across the air‐soil interface, methane can be lost from the marsh system to the atmosphere through the lateral movement of pore waters supersaturated with methane into tidal creeks, with subsequent degassing across the water‐air interface. Estimates of the magnitude of methane input to the atmosphere by this mechanism indicate it may be as important as diffusional losses across the air‐soil interface. These data suggest that salt marshes of this type make only a minor contribution to global atmospheric methane.
Atmospheric chlorine and stratospheric ozone nonlinearities and trend detection
Authors: Herman J. R. , McQuillan C. J.
Published: February 2008

The percent decrease of total stratospheric ozone column content due to the injection of fluorocarbons (F‐11 and F‐12) has been found to be a nearly linear function of the atmospheric mixing ratio of ClX between 1.2 and 10 parts per billion by volume (ppbv). In contrast, Cicerone et al. (1983) found a broad region of slightly positive change in ozone column content between 10 and 80 km for small ClX perturbations in addition to a nonlinear negative decrease for larger perturbations. The presence of a nonlinear response in column ozone to moderate ClX changes appears to depend strongly on the method of diurnal averaging employed in the calculation. The immediate decrease in ozone column content for our small ClX perturbation results leads to the prediction of an earlier date for possible experimental detection of total ozone trends related to chlorine. For larger ClX perturbations the response in column ozone is nonlinear when the amount of ClX in the stratosphere becomes comparable to or larger than the amount of NOx. On the basis of our time‐dependent calculations using a specified rate of fluorocarbon injection obtained from Logan et al. (1978), and similar previously obtained results from other models, the first evidence of an ozone decrease induced by ClX may be observable in the vicinity of 40 km by 1987–1990 with present‐day satellite instrumentation (Nimbus 7). The actual detection of an ozone decrease by 1990 might be obscured by seasonal and longer‐term atmospheric variations. Because of increasing fluxes of several minor constituents (e.g., CH4), possible long‐term temperature changes in the stratosphere, and possible secular solar flux changes, observation of an ozone decrease is not necessarily an indicator of damage to ozone caused by atmospheric chlorine. Comparing the percent difference curves near 40 km for the diurnal variation of ozone corresponding to different amounts of ClX may provide a means of distinguishing ClX effects from other atmospheric changes. The change should be detectable when ClX finally reaches 5 ppbv in the upper stratosphere (about 2020). By the year 2020 the total ozone decrease due to ClX should be about 3% (2.5% with increasing methane) and may already pose environmental problems.
Bipolar model of the electrical environment of the high‐voltage direct current power line
Authors: Hoppel William A.
Published: February 2008

A numerical model of the ion flow in the vicinity of a high‐voltage direct current (HVDC) transmission line operating in corona has been developed. The model solves the system of equations governing electrical potential and positive and negative ion concentrations in bipolar coordinates and includes the effect of horizontal wind. The model predicts the downwind space charge plume and ionic current densities at ground similar to those measured near power lines.
Thundercloud electric field measurement in the 553‐m CN Tower during 1978–1983
Authors: Chang J. S. , Beuthe T. G. , Hu G. G. , Stamoulis G. , Janischewskyj W.
Published: February 2008

A study of atmospheric electric field measurements at the CN Communications Tower in Toronto, Canada (height 553 m above ground level (AGL)) has been conducted during the period from 1978 to 1983. Of particular interest were the field conditions during the times when lightning struck the tower. Measurements were carried out using fixed radioactive probes and a movable Stanford‐University‐type field mill located at 366 m AGL. Results show that the electric field measurements at 366 m AGL are significantly influenced by their azimuthal location under cloudy conditions and that approximately 23% of the lightning strikes to the tower occur in the absence of a strong vertical electric field.
Lightning channel properties determined with a vertically pointing Doppler radar
Authors: Mazur Vladislav , Zrnic' Dusan S. , Rust W. David
Published: February 2008

Measurements of lightning have been made with a vertically pointing, 10 cm wavelength Doppler radar and have shown that the lightning echoes produce identifiable coherent peaks in the Doppler spectrum. We have used the evolution of intensity and position of the spectral peaks in the velocity domain to infer some channel properties. From our analysis of 40 lightning echoes, all of them produced by intracloud flashes, we have determined that (1) the ionized lightning channels remain overdense for 25–200 ms, with a mean of 93±44 ms, which is in agreement with earlier theoretical studies; (2) the decay of the lightning channel radar cross section is exponential with an average rate of about 0.2 dB ms−1; and (3) lightning channels are accelerated most probably by a combination of buoyancy and the earth's magnetic field acting on the hot plasma channel through which a current flows. The resulting channel velocity is apparently due to accelerations from these forces combined with the velocity of the air in which the lightning is embedded. Using the lightning as a tracer, we infer vertical air velocities of −2.0 to 17.5 ms−1, most of which are positive. Our observations suggest that lightning occurs usually within updraft regions.
Global fluctuations in the distribution of atmospheric mass
Authors: Trenberth Kevin E. , Christy John R.
Published: February 2008

Two global data sets have been analyzed to determine the interannual variability of the zonal mean mass distribution. The first is a National Meteorological Center (NMC) global data set of sea level pressures beginning in December 1977 and surface pressures beginning in April 1979. The second is an 11‐year (1972–1982) hybrid set of sea level pressures from the Australian southern hemisphere and U.S. Navy northern hemisphere analyses. The two sets are compared and evaluated by seeing how well they satisfy the constraint of conservation of mass. Anomalies in total mass due to changes in water vapor content of the atmosphere are lost in the data problems. Several inhomogeneities or discontinuities are found and are identified either with changes in analysis procedures in both data sets or the introduction of new orography and operational models at NMC. Consequently only limited periods of data are suitable for determining the dominant modes of variability. Nevertheless, hemispheric mean anomalies in mass in one hemisphere tend to be mirrored in the other, and it is clear that previously deduced fluctuations in hemispheric mean mass are mostly real. Predominant modes of variability of zonal means reveal systematic exchanges of mass (1) almost entirely confined within each hemisphere in isolation, (2) between the extratropics of each hemisphere with little impact on the tropics as an antisymmetric mode, and (3) between the tropics and extratropics in a symmetric mode. The second mode played a strong role in redistributing mass during April–July of 1979 during the First GARP Global Experiment (FGGE) and resulted in an exceptionally deep circumpolar trough over the southern hemisphere and record high pressures over the northern hemisphere. The possible origin of these modes is briefly considered.
Global climate variation due to fluctuations in the rate of deep water formation
Authors: Watts Robert G.
Published: February 2008

A simple climate model that includes a horizontally averaged deep ocean with vertical diffusive and advective exchange indicates that variations in the rate of deep water formation can cause substantial global climatic fluctuations.
Parameterization of the photochemistry of stratospheric ozone including catalytic loss processes
Authors: Stolarski R. S. , Douglass A. R.
Published: February 2008

A parameterization has been developed which accurately describes the photochemical response of odd oxygen to dynamically induced perturbations in odd oxygen and temperature. The temperature and odd oxygen dependencies of the loss processes for odd oxygen through catalytic cycles involving odd nitrogen, odd chlorine, and odd hydrogen have been specifically included. The assumption that a linear perturbation equation may be used to describe the response of odd oxygen to perturbations in odd oxygen and temperature has been tested and found to be acceptable for a physically reasonable range of perturbations, i.e., up to approximately 50% in odd oxygen mixing ratio and approximately 10 K in temperature. This scheme should prove useful for analyzing the feedback between ozone chemistry and ozone transport and also for analysis of ozone and temperature data.
A two‐photon laser‐induced fluorescence field instrument for ground‐based and airborne measurements of atmospheric NO
Authors: Bradshaw J. D. , Rodgers M. O. , Sandholm S. T. , KeSheng S. , Davis D. D.
Published: February 2008

This paper reports on a new two‐photon laser‐induced fluorescence (TP‐LIF) sensor capable of making routine measurements at the few parts per trillion volume level. This direct spectroscopic detection method has been demonstrated to be a reliable instrument while performing both on the ground and in the air. As currently designed it is unique in being “signal” rather than “signal‐to‐noise” limited. The latter characteristic enables the TP‐LIF sensor to make atmospheric measurements of NO under environmental conditions that might normally be considered unsuitable for a laser technique. These include clouds, rain, and, in general, high‐atmospheric‐aerosol loading conditions. Of special interest is the insensitivity of the TP‐LIF NO instrument to changes in pressure while operating in the troposphere. This characteristic has enabled this sensor to be used to record real‐time altitude profiles of NO. Future improvements should make possible two measurement opportunities: (1) NO flux measurements via the airborne eddy‐correlation method and (2) nitrogen isotopic distribution measurements (e.g., N15O16 versus N14O16) as a means of identifying specific NOx, sources.
Early electrification and precipitation development in a small, isolated Montana cumulonimbus
Authors: Dye J. E. , Jones J. J. , Winn W. P. , Cerni T. A. , Gardiner B. , Lamb D. , Pitter R. L. , Hallett J. , Saunders C. P. R.
Published: February 2008

Instrumented aircraft and radar were used to investigate the microphysical, electrical, and dynamic evolution of the life cycle of a small thunderstorm which occurred in southeastern Montana. The observations commenced as precipitation development was just beginning, continued through the active stage of growth as the cloud produced graupel up to 8 to 9 mm diameter and reflectivities aloft of 45 dBZ, through the dissipation stage when only an anvil with a trail of light precipitation remained. The largest particles and the primary development of precipitation were found to occur in the fringes of the updraft. The electric fields inside the cloud did not exceed 100 V m−1 until 5 mm graupel, ice particle concentrations of 10 L−1, and reflectivities of 35 dBZ were already present, but then rapidly electrified to produce a single intracloud discharge 8 min later, near the peak of microphysical development. Early in the electrical development of the cloud when observed electric fields were only 200 V m−1, negative charge accumulation was observed near the 7 km (−20°C) level and was associated with the high reflectivity region. In the early stages of precipitation fallout, particle charge measurements near 4.5 km showed primarily negatively charged particles which appeared to be associated with precipitation falling from the cloud. Less than 5 to 10% of the observed particles larger than 100 μm were carrying charges larger than 5 pC, the detection limit of the instrument. These observations are discussed from the point of view of charge generation in thunderstorms, particularly, charge transfer between colliding ice particles.
Three‐dimensional simulations of stratospheric N2O: Predictions for other trace constituents
Authors: Mahlman J. D. , Levy H. , Moxim W. J.
Published: February 2008

The Geophysical Fluid Dynamics Laboratory (GFDL) three‐dimensional general circulation/tracer model has been used to investigate the stratospheric behavior of N2O under a range of photodestruction hypotheses. A comparison of observations with these simulations shows that the atmospheric N2O lifetime lies between 100 and 130 years. For the three experiments conducted, it was found that the model‐derived global one‐dimensional eddy diffusion coefficients Kz for one experiment are appropriate for the other two experiments as well. In addition, the meridional slopes of N2O mixing ratio isolines are virtually identical in the lower stratosphere for all three experiments. The generality of these two results was explored with a simple “two‐slab” model. In this model the equilibrium meridional slopes of trace gas isolines and Kz values are solved directly. The model predicts that long‐lived gases with weak photodestruction rates should have similar meridional slopes, but the effect of faster destruction is to flatten the meridional slopes. The simple model also predicts that Kz depends upon chemical processes through a direct dependence upon the meridional slope for a given gas as well as upon the intensity with which upward propagating tropospheric disturbances force the stratospheric zonal winds. The three N2O experiments have been compared against detailed observational analyses. These analyses show that the model meridional N2O slopes are too flat by about 30%. The simple two‐slab model indicates that this results from a somewhat weak forcing of the model stratospheric zonal winds. A comparison of the temporal variability of model N2O against the “Δ” statistics of Ehhalt et al. (1983) shows good agreement. Another simple theoretical model is proposed that shows why Δ statistics are so useful and predicts the circumstances under which different destruction chemistries should lead to different Δ statistics. These results have allowed a very general extrapolation of the three N2O numerical experiments to predicted structure for a wide class of long‐lived trace gases. Specifically, the supporting theoretical developments allow predictions for the effect of chemistry on the global (one‐dimensional) behavior, meridional‐height (two‐dimensional) structure, and local temporal variability. Finally, some examples of transient behavior are presented through model time series at points corresponding to available measurements. These time series, with the support of horizontal N2O charts, show complex behavior, including pronounced seasonal cycles, transport‐produced N2O “inversions,” and detailed meridional transport events associated with transient stratospheric disturbances.
Effect of ocean mixing on the transient climate response to a CO2 increase: Analysis of recent model results
Authors: Harvey L. D. Danny
Published: February 2008

Results of several recent reports on the role of ocean mixing in the transient response to a CO2 doubling are analyzed and compared. Wigley and Schlesinger (1985) obtained an analytical solution to a one‐dimensional box‐diffusion (BD) ocean model in which the mixed layer e‐folding time τe ∝ ƒ02KΔTeq2, where ƒ0 is the planetary ocean fraction, K is the ocean diffusivity, and ΔTeq is the equilibrium temperature response. The dependence of τe obtained by Wigley and Schlesinger is compared with that obtained using simple land‐sea resolved and box‐advection‐diffusion (BAD) models. For a BAD model the dependence of τe on both K and ΔTeq is significantly less than for a BD model. A comparison of the transient response of BD and BAD models using the same effective K indicates that the behavior of the BAD model cannot be captured using a BD model, except during the first few decades of the transient response. Schlesinger et al. (1985) estimated atmospheric and mixed layer values of τe for their coupled atmosphere‐ocean general circulation model (A/O GCM) by fitting a BD model to the first 16 years of their A/O GCM transient response and then integrating the BD model for 200 years. However, Schlesinger et al. appear to have overestimated values of τe for their long‐term A/O GCM by fitting their short‐term A/O GCM transient response to a model in which the equilibrium globally averaged atmospheric and mixed layer temperature responses are equal, whereas this is apparently not true for their A/O GCM. Hansen et al. (1984) estimated τe by modeling three‐dimensional ocean mixing as a series of isolated BD models, one below each horizontal grid point, and by using tritium‐based diffusion coefficients, which probably are too large when applied to heat and probably lead to an overestimate of the actual τe.
Zonal and geographical distributions of cirrus clouds determined from SAGE data
Authors: Woodbury Gerard E. , McCormick M. P.
Published: February 2008

An analysis using Stratospheric Aerosol and Gas Experiment (SAGE) data for the period February 1979 to November 1981 was performed to determine the spatial extent and frequency of occurrence of cirrus clouds over a large portion of the earth's surface. The effective field of view corresponding to the determined frequency was 100 km2. A by‐product of the study reveals the statistics of tropospheric observational opportunities for a limb‐sounding satellite sensor by determining the percentage of times of successful penetration to a given height or depth below the tropopause.

The results of the analysis showed that optically thick cirrus clouds form most often in the midlatitudes and over the tropics, with distinct minima near latitude bands of 20°–30° north and south. The zonally averaged latitudinal distributions of cirrus clouds observed by SAGE compared very well with the Nimbus 5 selective chopper radiometer (SCR) observations in shape but not in magnitude. SAGE showed about twice the magnitude of the SCR results. The percentage of tropospheric observational opportunities down to 7 km was as high as 60% in the upper latitudes. A geographical presentation of the SAGE results showed the growth and seasonal movement of high‐cloud features were in good agreement with previous studies.
Kinetics of the formation and decomposition of hydroxymethanesulfonate
Authors: Kok Gregory L. , Gitlin Sonia N. , Lazrus Allan L.
Published: February 2008

The kinetics of the formation and decomposition of hydroxymethanesulfonate (HMSA) have been examined at pH 4 and 5. The second‐order rate constant for the formation of HMSA at 25°C was measured to be 1.94 ± 0.11 and 12.60 ± 1.04 mol−1 s−1 at pH values of 4 and 5, respectively. The rate constant of HMSA decomposition to form formaldehyde (HCHO) and aqueous sulfur dioxide S(IV) at pH 4 and 5 was 4.8 ± 0.4 × 10−7 and 3.5 ± 0.2 × 10−6 s−1, respectively. In addition, no reaction between hydrogen peroxide (H2O2) and HMSA was observed when a tenfold molar excess of H2O2 was present at pH values of 4 and 5.
A new source of ozone in the terrestrial upper atmosphere?
Authors: Allen Mark
Published: February 2008

The simultaneous measurements of atomic O, O2, O3, and N2 between 90 and 110 km obtained by a rocket‐borne mass spectrometer flown during the Aladdin 74 program provide an opportunity to test directly the simple atmospheric chemical model first proposed more than 50 years ago by S. Chapman, which is today the core of the complex chemistry controlling stratospheric O3. The Aladdin 74 O3 results are found to be significantly in excess of model abundances computed using the most current values of the key chemical parameters. The calculations may possibly be in error due to uncertainties in these key parameters and/or in the measurement of the related species. However, the extra O3 may be a consequence of reactions between ground state O2 and electronically excited O2 resulting from the recombination of atomic O.
Reaction of atomic bromine with acetylene and loss rate of atmospheric acetylene due to reaction with OH, Cl, O, and Br
Authors: Payne W. A. , Nava D. F. , Brunning J. , Stief L. J.
Published: February 2008

Acetylene (C2H2) is an important hydrocarbon species which is present in trace quantities in the troposphere and lower stratosphere. Potential loss processes for atmospheric C2H2 include reactions with OH, Cl, O, and Br as well as photodissociation. Rate data for the first three reactions are available in the literature, but the latter reaction has not been the subject of any previous studies. We have measured the rate constant for the reaction at four temperatures over the range 210–393 K and at pressures between 15 and 100 torr Ar. The technique employed was flash photolysis combined with time‐resolved detection of atomic bromine via Br resonance radiation. The reaction was shown to be independent of total pressure (Ar) and temperature over the indicated ranges. The average of all experiments gives the value k = (4.0 ± 0.8) × 10−15 cm3 s−1, where the error is 2 standard deviations. The result is compared with previous data from our laboratory for reactions of H, Cl, OH, and NH2 with C2H2. Loss rates for atmospheric C2H2 have been calculated as a function of altitude for reactions with OH, Cl, O, and Br.