bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of satellite data to study tropospheric ozone in the tropics
Authors: Fishman Jack , Minnis Patrick , Reichle Henry G.
Published: February 2008

Three independent examples are discussed which suggest that photochemical ozone production in the troposphere can be observed in the tropics from an analysis of total ozone data. The first finding shows that the seasonal cycle of total columnar ozone is dominated by the seasonal cycle of tropospheric ozone, even though tropospheric ozone accounts for only 5–15% of the total ozone. Second, a case study is presented which shows that enhanced total ozone observed over the Amazon Basin can be associated with the presence of biomass burning. In situ measurements have confirmed that biomass burning does result in the production of photochemically generated ozone, analogous to the formation of “smog” near industrialized areas. Third, an analysis of the distribution of carbon monoxide obtained from a space shuttle platform is strongly correlated with the concurrent distribution of total ozone between 5°S and 10°N. Because all of the sources of carbon monoxide are located in the troposphere, this finding likewise suggests that the gradients of total ozone at low latitudes must also reflect processes occurring in the troposphere.
Evaluation of standard radiation atmosphere aerosol models for a coastal environment
Authors: Whitlock C. H. , Suttles J. T. , LeCroy S. R. , Sebacher D. I. , Fuller W. H.
Published: February 2008

Calculations are compared with data from an experiment to evaluate the utility of standard radiation atmosphere (SRA) models for defining aerosol properties in atmospheric radiation computations. Initial calculations with only SRA aerosols in a four‐layer atmospheric column simulation allowed a sensitivity study and the detection of spectral trends in optical depth, which differed from measurements. Subsequently, a more detailed analysis provided a revision in the stratospheric layer, which brought calculations in line with both optical depth and skylight radiance data. The simulation procedure allows determination of which atmospheric layers influence both downwelling and upwelling radiation spectra.
Absolute absorption cross sections of ozone in the 185‐ to 350‐nm wavelength range
Authors: Molina L. T. , Molina M. J.
Published: February 2008

The absorption cross sections of ozone have been measured in the wavelength range 185–350 nm and in the temperature range 225–298 K. The absolute ozone concentrations were established by measuring the pressure of pure gaseous samples in the 0.08‐ to 300‐torr range, and the UV spectra were recorded under conditions where less than 1% of the sample decomposed. The temperature dependence is significant for wavelengths longer than ∼280 nm. The absorption cross‐section values around 210 nm were found to be about 10% larger than the previously accepted values.
The isotopic composition of precipitation at Mohonk Lake, New York: The amount effect
Authors: Gedzelman Stanley David , Lawrence James R. , White James W. C. , Smiley Daniel
Published: February 2008

The deuterium/hydrogen ratios, expressed in terms of δD, of precipitation at Mohonk Lake, New York, from 118 individual storms during the six summers 1977–1982 have been measured and considered in light of the concurrent meteorological conditions. The so‐called amount effect of Dansgaard—summers with above average precipitation totals tend to have below average δD values is observed at Mohonk Lake and is also registered in the tree ring cellulose of water‐stressed Eastern White Pine. A similar amount effect is also observed for individual events and can be explained in terms of differences between convective and cyclonic precipitation. Stable cyclonic precipitation has much lower δD values (−64.8) but much greater amounts (3.77 cm) on average than purely convective storms (δD = −27.2, 1.30 cm). The seasonal amount effect is related to the fact that during the 6‐year observational period, wetter than normal summers at Mohonk Lake also had a higher than normal percentage of stable cyclonic precipitation and a lower than normal percentage of purely convective precipitation.
Operational overview of NASA GTE/CITE 1 airborne instrument intercomparisons: Carbon monoxide, nitric oxide, and hydroxyl instrumentation
Authors: Beck Sherwin M. , Bendura Richard J. , McDougal David S. , Hoell James M. , Gregory Gerald L. , Curfman Howard J. , Davis Douglas D. , Bradshaw John , Rodgers Michael O. , Wang Charles C. , Davis Leighton I. , Campbell Malcolm J. , Torres Arnold L. , Carroll Mary Anne , Ridley Brian A. , Sachse Glen W. , Hill Gerald F. , Condon Estelle P. , Rasmussen Reinhold A.
Published: February 2008

An overview of the airborne intercomparisons of CO, NO, and OH instrumentation is presented in this first paper of the series on the NASA Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 1). This paper provides the reader with background information about several important characteristics of the project. These include the overall objectives and approach; the measurements taken; the intercomparison protocol, aircraft platform, profiles of each aircraft flight; and the participants. A synopsis of the overall results of the CO, NO, and OH instrument intercomparisons is also included. Companion papers discuss the detailed results of the CO and NO intercomparison tests as well as pertinent scientific findings.
Fast‐response, high‐precision carbon monoxide sensor using a tunable diode laser absorption technique
Authors: Sachse Glen W. , Hill Gerald F. , Wade Larry O. , Perry Murray G.
Published: February 2008

A tunable diode laser instrument denoted as DACOM (Differential Absorption CO Measurement) has been developed to meet the fast‐response, high‐precision CO measurement needs of the GTE (Global Tropospheric Experiment) program. Under the GTE program, DACOM participated in the three field missions of CITE 1 (Chemical Instrumentation Test and Evaluation 1), a project involving the intercomparison of trace gas measurement techniques. DACOM performance, including analyses of measurement error sources, is discussed for the ground‐based mission at Wallops Island, Virginia (summer 1983), and two missions on the NASA CV‐990 (fall 1983 and spring 1984). Examples of fast‐response (≈1 s), high‐precision (±1 part per billion by volume, ±1.5% of reading) airborne data are included to illustrate the capability of this instrument.
Tropopause fold structure determined from airborne lidar and in situ measurements
Authors: Browell E. V. , Danielsen E. F. , Ismail S. , Gregory G. L. , Beck S. M.
Published: February 2008

The first remote measurements of O3 and aerosols across a tropopause fold are presented in this paper. An airborne differential absorption lidar (DIAL) system was used to obtain profiles of O3 and aerosols along a cross section of a fold on April 20, 1984, over southern Nevada and California. The DIAL measurements across the tropopause fold show a 2.0‐km‐deep layer, with high O3 concentrations and enhanced aerosol backscattering, that slopes downward from north of Las Vegas, Nevada, to the top of the planetary boundary layer (PBL) over Yuma, Arizona. This is the first continuous mapping of a tropopause fold from the upper troposphere to the PBL. Mixing ratios of O3 in excess of 200 parts per billion by volume (ppbv) were measured remotely in the fold, and these values were corroborated by in situ measurements of O3 through the fold at an aircraft altitude of 6.7 km. Enhanced aerosol back‐scattering was observed in the tropopause fold and attributed to stratospheric aerosols from the El Chichon eruption. An analysis of the potential vorticity distribution along the DIAL flight track was performed using radiosonde data. A high positive correlation was found between the DIAL O3 mixing ratios and the potential vorticity values in the fold. The average ratio between O3 and potential vorticity was found to be 50.2 ppbv/10−5 cm2 deg g−1 s−1 in the fold. The decrease in layer thickness, potential vorticity, ozone mixing ratio, and aerosol backscatter down the axis of the fold is consistent with a convergent entrainment of tropospheric air across both boundaries of the fold and subsequent irreversible mixing by small‐scale turbulent motions.
The production of methane from solid wastes
Authors: Bingemer H. G. , Crutzen P. J.
Published: February 2008

An analysis is presented of possible worldwide production of methane from anaerobic decay of organic municipal and industrial wastes in landfills. The amount of methane released to the atmosphere from this source may now be in the range of 30–70×106 T/yr, which is between 6% and 18% of the total CH4 source. By far, most of this emission comes from the industrialized world. Release rates from these countries have been increasing steadily during the past decades, but growth rates are now gradually stagnating. In the future, the contribution from developing nations is expected to grow rapidly because of increasing population and urbanization. Consequently, methane release from landfills may become one of the main sources of atmospheric methane in the next century.
Application of Advanced Very High Resolution Radiometer vegetation index to study atmosphere‐biosphere exchange of CO2
Authors: Fung I. Y. , Tucker C. J. , Prentice K. C.
Published: February 2008

Normalized difference vegetation indices derived from radiances measured by the Advanced Very High Resolution Radiometer aboard the NOAA 7 polar‐orbiting satellite were used to prescribe the phasing of terrestrial photosynthesis. The satellite data were combined with field data on soil respiration and a global map of net primary productivity to obtain the seasonal exchange of CO2 between the atmosphere and the terrestrial biosphere. The monthly fluxes of CO2 thus obtained were employed as source/sink functions in a global three‐dimensional atmospheric tracer transport model to simulate the annual oscillations of CO2 in the atmosphere. Reasonable agreement was found between the simulated and observed annual cycles of atmospheric CO2 at the locations of the remote monitoring stations. The results demonstrate that satellite data of high spatial and temporal resolution can be used to provide quantitative information about seasonal and longer‐term variations of photosynthetic activity on a global scale. Atmospheric CO2 observations and a three‐dimensional atmospheric model have been used to validate the translation of the nondimensional satellite data into dimensional carbon fluxes. Direct calibration will require extensive ground truth and field measurements at ecosystem scales.
On the variability of desert aerosol radiative characteristics
Authors: d'Almeida Guillaume A.
Published: February 2008

Size distributions of desert aerosol observed in arid regions of Senegal, Mali, and Niger under different weather conditions are classified in terms of visibility ranges into three categories and converted to lognormal distributions. The resulting curves are considered to represent average distributions encountered during fair weather, wind carrying dust, and sandstorm episodes. By means of the Mie theory, main radiative characteristics, i.e., attenuation coefficients, single scattering albedo, asymmetry factor, and phase functions, are computed for the spectral range between 0.3 and 40 μm. Regardless of the prevailing atmospheric conditions, extinction and scattering coefficients indicate a nearly wavelength independent pattern in the solar spectral range due to the large and effective particle scattering diameter. All size distributions yield strong absorption peaks at 10 μm, clogging the atmospheric window. Moreover, the temporal variation of single scattering albedo and asymmetry factor is most sensitive in the solar spectrum. For climate modeling purposes, average values are computed for seven spectral bands of the European Centre for Medium Range Weather Forecast radiation scheme. In addition, phase functions for eight characteristic wavelengths are presented and show predominantly forward scattering properties. Optical depth measurements performed in the framework of the African turbidity monitoring network between November 1980 and February 1984 indicate a high space and time fluctuation of aerosol concentration over the Sahara and surrounding areas. Daily average optical depth values (base e) between 0.03 in the Hoggar mountains and 3.5 during sandstorms in Boutilimit (Mauritania) have been observed for the mandatory wavelength 0.5 μm. Turbidity values in Zaria (Nigeria) indicate that the Sahel region is an insignificant area for mineral dust production.
Biotic changes consistent with the increased seasonal amplitude of atmospheric CO2 concentrations
Authors: Houghton R. A.
Published: February 2008

Monthly estimates of gross primary production (gross uptake of CO2 by plants) and ecosystem respiration (gross release of CO2 from the ecosystem) in an oak‐pine forest in the northeastern United States were used in this study to examine the types of metabolic changes in terrestrial systems that might yield the increased seasonal amplitude of CO2 concentrations observed at several monitoring stations in recent years. In this study, increases in either photosynthesis or respiration increased the amplitude of the seasonal oscillation of CO2 concentrations if the increases were predominantly in the northern hemispheric summer and winter, respectively. The quantitative changes in metabolism required to produce the observed increase in amplitude, however, were too large to be explained by CO2 fertilization or by a temperature‐induced increase in winter respiration. Investigations of the role of the biota in causing seasonal and year‐to‐year variations in atmospheric CO2 concentrations are limited by the lack of stations monitoring CO2 in continental air.
An empirical study of the nuclear explosion‐induced lightning seen on IVY‐MIKE
Authors: Colvin J. D. , Mitchell C. K. , Greig J. R. , Murphy D. P. , Pechacek R. E. , Raleigh M.
Published: February 2008

We report the results of a unique study of the lightninglike phenomena that were seen to accompany the MIKE shot of operation IVY on October 31 1952. MIKE was a thermonuclear surface burst yielding 10.4 MT, which took place on Enewetak Atoll. During the period of approximately 10 ms after detonation, five discrete luminous channels were seen to start from the ground or sea surface at a distance of approximately 1 km from the burst point and to grow up into the clouds. We have reexamined the original photographic records of IVY‐MIKE, obtaining effective brightnesses (optical powers per unit length) for the luminous channels at different altitudes as functions of time. The absolute calibration for the MIKE records was deduced by comparison with the photographic records of other events of that era, laboratory measurements of film sensitivity, and use of atmospheric transmission data taken just prior to the MIKE event. Errors in this analysis lead to an uncertainty of a factor of ∼2 in the brightnesses of the luminous channels. In the laboratory we have used laser‐guided electric discharges to create long (100 cm), arclike plasma channels to simulate the observed luminous channels and to allow determination of an empirical relation between the brightness of the channel and the electric current flowing in the channel. These laboratory discharges had peak currents up to 100 kA and periods of ∼2 ms. Spectroscopic analysis showed that the luminous channels consisted primarily of normal air plasma with typical ground‐level contaminants. Photographic studies showed that these long‐duration discharges are unstable to the m = 1 magnetohydrodynamic (MHD) instability and become severely distorted in less than 1 ms. By direct comparison of the luminous channels seen at MIKE and the laboratory discharges, we deduce: (1) the peak current in the prominent (brightest) channel at MIKE was between 200 and 600 kA. Here the most likely value of the peak current was 250±50 kA, but potential systematic errors in the film calibration and the comparison of MIKE and laboratory data make higher currents possible. (2) The rapid decline in the brightness of the luminous channels seen at MIKE is caused by a combination of the effects of the MHD instability, which eventually leads to a broadening of the current‐carrying channel, and channel cooling by turbulent convective mixing.
Chemistry of the global troposphere: Fluorocarbons as tracers of air motion
Authors: Prather Michael , McElroy Michael , Wofsy Steven , Russell Gary , Rind David
Published: February 2008

Winds and convective mixing from a general circulation model of the atmosphere have been applied in a chemical tracer model (CTM) to simulate the global distribution and temporal variability of chlorofluorocarbons (CFCs). The seasonal cycle in moist convection, with maximum activity over continents in summer, leads to an annual cycle in the surface concentration of CFCs. Emissions are retained in the lowest levels of the atmosphere during winter, and surface concentrations peak near sources. In this season, CFCs from European sources are carried by low‐level winds into the Arctic. During summer, vertical exchange is more efficient, and pollutants are transported more rapidly to the middle atmosphere. Consequently, concentrations of CFCs during summer are relatively low near the surface and elevated in the middle troposphere. Time series analysis of data from Adrigole, Ireland, indicates that the model accurately simulates long‐range transport of air pollution. The model reproduces global distributions and trends for CFC‐11 and CFC‐12 observed by the ALE experiment; however, subgrid diffusion must be introduced into the model in order to reproduce the observed interhemispheric gradient. Interhemispheric exchange occurs mainly in the upper tropical troposphere, producing a profile which increases with altitude in the southern hemisphere, in agreement with observations. The distribution of CFCs is such that it is necessary to apply important corrections to observations at surface stations in order to derive global distributions.
Primary quantum yields of NO2 photodissociation
Authors: Gardner Edward P. , Sperry Paul D. , Calvert Jack G.
Published: February 2008

A large discrepancy exists among recent estimates of the primary quantum efficiencies (ϕ1) of nitrogen dioxide photodecomposition, NO2 + hν → NO + O(3P), in the wavelength range from 374 to 396 nm. To resolve this problem, quantum yields of formation of NO, O2, and NO2 loss have been measured for NO2 vapor at low pressures (0.13–0.30 torr) irradiated at selected wavelengths (334.1–404.3 nm) and temperatures (273–370 K). From these data, estimates of ϕ1 were derived which confirm the previous findings of Jones and Bayes (1973b): ϕ1 increases rapidly from near zero at 424 nm to near unity for excitation at λ < 394 nm. The temperature and wavelength dependences of ϕ1 appear to be in qualitative accord with the simple theory of Pitts et al. (1964) that the energy deficiency for photodissociation of NO2 excited at λ > 397.9 nm (λdiss) is made up in large part from the rotational and vibrational energy of the NO2 molecules. Recommended values for ϕ1 based upon a review of these data and estimates made over a period of 58 years, are given as a function of wavelength.
Ozone vapor pressure and absorption cross‐section measurements: Introduction of an ozone standard
Authors: Mauersberger K. , Hanson D. , Barnes J. , Morton J.
Published: February 2008

During the last few years, two standards for ozone have been developed. One is based on the vapor pressures above liquid or solid ozone, the other is based on the UV light absorption of ozone at the 253.7‐nm Hg line. Recent measurements of cross sections at vapor pressures above liquid ozone have provided the correlation between the two standards. The measurements at various vapor pressures resulted, for the 253.7‐nm line, in a cross section at room temperature of 1.131×10−17 cm2 with an rms uncertainty of ±0.7%. Direct cross‐section measurements by simultaneously measuring absolute ozone pressures and temperatures and, in addition, performing a gas purity analysis yielded a cross section of 1.136×10−17 cm2 with an rms uncertainty of ±0.5% The measurements reported show that the two ozone standards agree to better than ±0.5%.
Fractal structure and exponential decorrelation in rain
Authors: Zawadzki I.
Published: February 2008

Statistics of rain rate increments are obtained from a 10‐year record of a tipping‐bucket rain gage. These statistics are analyzed for various effects: smoothing of data, sampling of data, noise in the data, and their consequences on the evidence for the fractal structure of rain. Furthermore, it is shown that rain becomes effectively decorrelated after ∼20 min. No evidence for scaling of rain rate increments in time is apparent from this analysis.
Real‐time flash flood prediction
Authors: Georgakakos Konstantine P.
Published: February 2008

A prototype hydrometeorological model for real‐time, site‐specific, flash flood prediction is presented. Precipitation prediction components are coupled with runoff‐generating and flood‐routing components through the water mass conservation law and a state estimator which was used for updating the model state variables from real‐time observations. The model is capable of operating under the various data availability conditions existing in flash flood prone areas. Sensitivity analysis using data from significant past flash floods indicates that short‐term model predictions are not significantly sensitive to the runoff‐generating model component when updating is performed. In addition, the sensitivity analysis suggested that model performance is best when all available meteorological and hydrological data are utilized by the state estimator. Remarkably (given the data available for calibration) good predictions of stream stage were obtained by the model for several flash flood cases.
Application of spatial Poisson models to air mass thunderstorm rainfall
Authors: Eagleson P. S. , Fennessey N. M. , Qinliang Wang , Rodriguez‐Iturbe I.
Published: February 2008

Eight years of summer storm rainfall observations from 93 stations in and around the 154 km2 Walnut Gulch catchment of the Agricultural Research Service, U.S. Department of Agriculture, in Arizona are processed to yield the total station depths of 428 storms. Statistical analysis of these random fields yields the first two moments, the spatial correlation and variance functions, and the spatial distribution of total rainfall for each storm. The sample is then split, and half is used to estimate, for each storm day, the distributions of the three parameters of each of the three conceptual spatial Poisson process models proposed previously by Rodriguez‐Iturbe et al. (1986). The absolute and relative worth of the three Poisson models are evaluated by comparing their prediction of the spatial distribution of storm rainfall with observations from the second half of the sample. The effect of interstorm parameter variation is examined.
Mesoscale atmospheric dynamics and modeling of rainfall fields
Authors: Cho Han‐Ru , Chan Douglas S. T.
Published: February 2008

A nonuniform potential vorticity model for frontogenesis is used to study the effects of height‐dependent inhomogeneities in the potential temperature and potential vorticity fields at the mesoscale. The model simulation results show that these irregularities induce in the vertical velocity field mesoscale patterns which have considerable vertical extent. It is suggested that these mesoscale inhomogeneities may be possible causes for the high degree of organization of precipitation fields and the formation of middle‐level rainbands.
Temperature dependence of the ozone absorption cross section at the 253.7‐nm mercury line
Authors: Barnes J. , Mauersberger K.
Published: February 2008

The temperature dependence of the ozone absorption cross section at 253.7 nm has been measured between 195 and 351 K. The experimental technique employed circumvents the necessity to determine the absolute ozone concentration for each temperature measurement. Below 273 K the cross section increases approximately 0.6%, while toward higher temperatures the cross section decreases rapidly. In a comparison, good agreement with other recently made measurements is shown.
Trace gas transport in the vicinity of frontal convective clouds
Authors: Pickering K. E. , Dickerson R. R. , Huffman G. J. , Boatman J. F. , Schanot A.
Published: February 2008

Airborne measurements of NOx, NOy, CO, and O3 were conducted in the vicinity of a line of towering cumulus and cumulonimbus clouds (approximate altitude, 9 km) in south‐central Oklahoma, on the afternoon of June 17, 1985. NOx, NOy, and CO concentrations in the upper tropospheric outflow region of these clouds were near environmental levels. Meteorological analyses show that these clouds were located above a cold front, which prevented the entry of air from the boundary layer directly below and near the cloud. Examination of the [NOy]/[CO] and [NOx]/[CO] ratios, as well as determination of the lifting condensation level and other thermodynamic analyses, indicated that the most likely origin of the air in the cloud outflow region was the layer immediately above the top of the boundary layer, which was quite clean. It appears that very little NOy was available to be scavenged by the clouds. The results for this case suggest that the large amount of vertical trace gas transport that has been noted in previous observations and model results cannot simply be extrapolated to all convective cells. The results also show the usefulness of CO as a conserved tracer.
Boundary layer ozone: An airborne survey above the Amazon Basin
Authors: Gregory Gerald L. , Browell Edward V. , Warren Linda S.
Published: February 2008

This paper discusses ozone data obtained in the Amazon Basin during July and August 1985 as part of NASA's Global Tropospheric Experiment (GTE) Amazon Boundary Layer Experiment (ABLE 2A). ABLE 2A, based at Manaus, Brazil, was a concentrated site study over the Amazon Basin to investigate source/sink relationships between the tropical forest and the troposphere during non‐biomass‐burning conditions. Ozone data obtained in the mixed layer above the forest canopy (100–2000 m altitude) in the Manaus area are discussed. In addition, profiles obtained during Amazon Basin flights from Belem (50°W) to Tabatinga (70°W), Brazil, are analyzed to determine any cross‐basin effects. The ozone discussions are primarily centered on the mixed layer. Companion papers discuss ozone behavior in the forest canopy and cross‐basin observations above the mixed layer. The data clearly show the tropical forest to be a strong ozone sink. Within the mixed layer, ozone gradients are observed with ozone values, during daylight, in the range of 10–20 ppbv. Amazon cross‐basin (70°–50°W) ozone observations are similar to those over the forest at Manaus (60°W). Near the Atlantic coast a forest‐to‐marine transition zone is noted within the mixed layer. Using a box model calculation for the mixed layer and for midmorning times, ozone loss rates are calculated to be as large as 5×1012 molecules s−1 cm−2, with a midmorning average of 1.6×1012 molecules s−1 cm−2.
Surface ozone measurements in Amazonia
Authors: Kirchhoff Volker W. J. H.
Published: February 2008

Surface ozone concentrations have been measured continuously for the first time, in a forest preserve area near Manaus (3°S, 60°W) during the ABLE 2A field expedition of July–August 1985. Major subjects addressed are diurnal variations and processes that might control it, both dynamic and chemical. Intense transient variations have been observed in association with showers and thunderstorms. The diurnal variations are well defined, with minimum concentrations during the night and maximum concentrations in the daytime. At night it is not uncommon to find zero O3 mixing ratios, whereas the daytime maximum of between 7 and 31 parts per billion by volume occurs around 1200–1300 LT. Below a height of 6 m a very strong O3 concentration gradient is found. On two occasions, nearby thunderstorms have caused strong abnormal enhancements of the O3 concentration.
Biomass‐burning emissions and associated haze layers over Amazonia
Authors: Andreae M. O. , Browell E. V. , Garstang M. , Gregory G. L. , Harriss R. C. , Hill G. F. , Jacob D. J. , Pereira M. C. , Sachse G. W. , Setzer A. W. , Dias P. L. Silva , Talbot R. W. , Torres A. L. , Wofsy S. C.
Published: February 2008

Biomass‐burning plumes and haze layers were observed during the ABLE 2A flights in July/August 1985 over the central Amazon Basin. The haze layers occurred at altitudes between 1000 and 4000 m and were usually only some 100 to 300‐m thick but extended horizontally over several 100 km. They could be traced by satellite imaging and trajectory studies to biomass burning at the southern perimeter of the Amazon Basin, with transport times estimated to be 1–2 days. These layers strongly influenced the chemical and optical characteristics of the atmosphere over the eastern Amazon Basin. The concentrations of CO, CO2, O3, and NO were significantly elevated in the plumes and haze layers relative to the regional background. The NO/CO ratio in fresh plumes was much higher than in the aged haze layers, suggesting that more than 80% of the NOx in the haze layers had been converted to nitrate and organic nitrogen species subsequent to emission. The haze aerosol was composed predominantly of organic material, NH4+, K+, NO3−, SO4=, and anionic organic species (formate, acetate, and oxalate). While the concentrations of most aerosol ions were substantially higher in the haze layers than in the regional background aerosol, the ratios between the aerosol ions in the haze layer aerosols were very similar to those in the boundary layer aerosol over the central Amazon region. Simultaneous measurements of trace gas and aerosol species in the haze layers made it possible to derive emission ratios for CO, NOx, NH3, sulfur oxides, and aerosol constituents relative to CO2. Regional and global emission estimates based on these ratios indicate that biomass burning is an important contributor in the global and regional cycles of carbon, sulfur, and nitrogen species. Similar considerations suggest that photochemical ozone production in the biomass‐burning plumes contributes significantly to the regional ozone budget.
Temperature‐dependent absorption cross sections for hydrogen peroxide vapor
Authors: Nicovich J. M. , Wine P. H.
Published: February 2008

Relative absorption cross sections for hydrogen peroxide vapor were measured over the temperature ranges 285–381 K for 230 nm ≤ λ ≤ 295 nm and 300–381 K for 193 nm ≤ λ ≤ 350 nm. The well‐established 298 K cross sections at 202.6 and 228.8 nm were used as an absolute calibration. A significant temperature dependence was observed at the important tropospheric photolysis wavelengths, λ > 300 nm. Measured cross sections were extrapolated to lower temperatures, using a simple model which attributes the observed temperature dependence to enhanced absorption by molecules possessing one quantum of O–O stretch vibrational excitation. Upper tropospheric photodissociation rates calculated using the extrapolated cross sections are about 25% lower than those calculated using currently recommended 298 K cross sections.
Interactions between HCl, NOx and H2O ice in the Antarctic stratosphere: Implications for ozone
Authors: Wofsy S. C. , Molina M. J. , Salawitch R. J. , Fox L. E. , McElroy M. B.
Published: February 2008

Thermodynamic properties of solid phases containing H2O and HCl are examined for conditions expected over Antarctica in winter. It is shown that solid solutions with 0.02–0.035 mole fraction HCl in H2O ice will form in the stratosphere at temperatures between 193° and 190°K. Crystalline HNO3·H2O and/or HNO3·3H2O form in the same temperature range. Thus condensation of small quantities of H2O (<1 ppm) leads to nearly complete removal of both HCl and HNO3 from the gas phase. Formation of ice‐HCl solid solutions provides a favorable setting for the heterogeneous reaction of HCl with ClNO3, initiating a rapid sequence of reactions that converts solid‐phase HCl into gaseous ClNO3 or chlorine oxide radicals. Odd nitrogen species are simultaneously converted into solid‐phase nitrates. The cycle producing reactive chlorine gases is likely to be completed before particles grow large enough to fall from the stratosphere. Hence precipitation of particles from the polar stratospheric clouds is expected to remove odd nitrogen from the stratosphere efficiently, leaving chlorine gases behind. High concentrations of reactive chlorine oxide radicals are rapidly produced by heterogeneous reactions if the initial concentration of HCl exceeds a critical value, 0.5 times the concentration of NOx before onset of condensation. Production of unreactive ClNO3 and HOCl is favored if HCl levels are lower than this value. The onset of Antarctic ozone depletion in the late 1970s may in part reflect growth of HCl levels beyond this threshold.
Photodissociation of pernitric acid (HO2NO2) at 248 nm
Authors: MacLeod Hélene , Smith Gregory P. , Golden David M.
Published: February 2008

The photodissociation of pernitric acid (PNA) has been studied at 248 nm. The quantum yield for production of OH radicals is 34±16%. The yield of OH from PNA was measured relative to that from H2O2. The translational and rotational energy current of the OH photofragment from PNA has been characterized. A fluorescent emission was also observed and characterized. It is attributed to electronically excited NO2 produced in the PNA photodissociation. A maximum yield of 30% for NO2* production was determined. The intensity of this emission, and a mass spectrometric peak at m/e = 33, have been found to be useful means of characterizing the purity of the PNA sample.
Prediction of all‐India summer monsoon rainfall with regional and large‐scale parameters
Authors: Parthasarathy B. , Diaz H. F. , Eischeid J. K.
Published: February 2008

Using multiple regression, several statistical models were developed to predict Indian monsoon rainfall from conditions antecedent to the start of the monsoon season (defined as the period June–September). The predictors were selected in a stepwise fashion from a set of 11 predictors. These predictors were in turn chosen from a larger pool of 31 potential predictors on the basis of the strength of their correlation with all‐India rainfall and on whether the predictor variable exhibited a significant difference in predictor mean values between wet (seasonal rainfall exceeding one standard deviation from the long‐term mean) and dry (seasonal rainfall lower than one standard deviation below the mean) years over the period 1951–1980. The models account for between 70 and 83% of the interannual variance of all‐India rainfall depending on the calibration period. The regressions were tested on sets of independent years. In these trials the amount of predictand (rainfall) variance realized varied from near zero to near 60% depending on the period. The models with the highest skill (except one) actually included data from years prior to the calibration period. Hence, these models were really performing “hindcasts,” and as such would be useful only in a diagnostic rather than a prognostic mode. However, the sliding calibration model, where the regression coefficients are recalculated annually did show some predictive skill. Many of the model predictors, such as the mean April latitude of the 500‐mbar ridge over India have been previously identified in the work of other investigators. New predictors, such as the preceeding winter to spring sea level pressure change at Bombay, India, which was a leading predictor in all the models, could alone account for 50–60% of the predictand variance. The latitudinal position of the 500‐mbar ridge axis in April along 75°E longitude was generally the second predictor to be entered. The regression model based on the earliest development sample (1951–1970), however, had the Southern Oscillation Index of Tahiti‐Darwin winter‐to‐spring sea level pressure tendency as its number two predictor.
Mars global atmospheric oscillations: Annually synchronized, transient normal‐mode oscillations and the triggering of global dust storms
Authors: Tillman James E.
Published: February 2008

Observation and analyses of the atmospheric pressure at the surface on Mars for several Martian years has led to the discovery of transient events in the daily pressure variations of an unusual nature. These events last only a few sols (Mars days), appear to repeat on an annual basis to within a few sols, appear to cover a large portion of the hemisphere on the same sol or at least within a few sols, occur in pairs with separations of 20 sols in some instances, are coincident with the annual pressure minimum (i.e., the maximum concentration of carbon dioxide in the southern hemisphere), and consist of spectral components near to, and sometimes identical in, frequency to the diurnal and semidiurnal harmonics. It is suggested that these events are Kelvin, normal‐mode, transient, global oscillations. Examination of the initiation of the 1977A, 1977B, and 1982A global dust storms indicate that pseudo‐diurnal and some‐times pseudo‐semidiurnal oscillations exist during the initiation phase and might be involved in triggering the global dust storms, possibly in conjunction with winds due to longer‐period circulations. The diurnal harmonic disappears prior to the 1977B global dust storm and is replaced by an oscillation at 1.1 cycles/sol. If the lack of a classical diurnal tide indicates the suppression of convection, this might partially explain the slow growth of the 1977B storm. The daily average pressure during the transient season, which precedes the global dust storm season by almost one fourth of a year, exhibits a different behavior during the global dust storm years than during the nonglobal dust storm years. This implies that the global circulation must differ significantly in these cases and may be related to the presence or absence of global dust storms later in a given year. These analyses suggest that an almost diurnal and an almost semidiurnal, high‐frequency global oscillation, different from the classical solar‐driven tides, may be quite common on Mars.
Vertical resolution of middle atmospheric measurements by ground‐based microwave radiometry
Authors: Bevilacqua Richard M. , Olivero John J.
Published: February 2008

The measurement of trace constituents in the middle atmosphere by ground‐based microwave spectroscopy has emerged as an important tool for probing that region of the atmosphere. However, the vertical resolution attainable with the technique has remained somewhat ambiguous and is worthy of further study. In order to explore this question, we first applied the Backus‐Gilbert inversion technique, which automatically yields quantitative estimates of the inversion spatial resolution, to this particular inverse problem. This indicated that the optimum resolution of Backus‐Gilbert inversions of microwave spectroscopic measurements is about 10 km. We then developed a general technique, based on inversion of delta function simulated profiles, for evaluating the resolution of any inversion technique. This was applied to the Chahine inversion technique, which is representative of inversion methods typically used in microwave spectroscopy. These results indicated that the optimum resolution of the Chahine technique is about 6 or 7 km, or nearly a factor of 2 better than the equivalent Backus‐Gilbert results. With the addition of simulated measurement error this resolution is degraded somewhat, especially near the inversion boundaries. However, for random measurement errors up to about the 1% level, 6‐ or 7‐km resolution is still attainable in the interior of the inversion domain.
PIPs and POPs: The reduction of complex dynamical systems using principal interaction and oscillation patterns
Authors: Hasselmann K.
Published: February 2008

A general method is described for constructing simple dynamical models to approximate complex dynamical systems with many degrees of freedom. The technique can be applied to interpret sets of observed time series or numerical simulations with high‐resolution models, or to relate observation and simulations. The method is based on a projection of the complete system on to a smaller number of “principal interaction patterns” (PIPs). The coefficients of the PIP expansion are assumed to be governed by a dynamic model containing a small number of adjustable parameters. The optimization of the dynamical model, which in the general case can be both nonlinear and time‐dependent, is carried out simultaneously with the construction of the optimal set of interaction patterns. In the linear case the PIPs reduce to the eigenoscilations of a first‐order linear vector process with stochastic forcing (principal oscillation patterns, or POPs). POPs are linearly related to the “principal prediction patterns” used in linear forecasting applications. The POP analysis can also be applied as a diagnostic tool to compress the extensive information contained in the high‐dimensional cross‐spectral covariance matrix representing the complete second‐moment structure of the system.
The role of gravity wave generated advection and diffusion in transport of tracers in the mesosphere
Authors: Holton James R. , Schoeberl Mark R.
Published: February 2008

A two‐dimensional model is used to study the comparative roles of advection and turbulent diffusion in controlling tracer transport in the meridional plane in the mesosphere. The Lindzen gravity wave drag and diffusion model is used to parameterize the effects of gravity waves on the zonal mean circulation. Sensitivity tests are conducted to determine the comparative roles of the mean meridional circulation and vertical diffusion by small‐scale turbulence in accounting for tracer transport. We compare a case in which turbulent diffusion by gravity waves is modeled using Lindzen's parameterization for the vertical eddy diffusion coefficient with a case that employs a much reduced diffusivity based on calculations by Schoeberl. Integrations are carried out for a simulated annual cycle in order to test the sensitivity of the tracer distribution to the assumed magnitude of the vertical diffusion coefficient. In both cases, eddy diffusion plays a secondary role compared to tracer advection by the mean meridional circulation for tracers with chemical lifetimes greater than about 10 days. We conclude that global transport in the mesosphere for long‐lived tracers, such as water vapor and carbon monoxide, is dominated by advection, and that for such tracers the eddy diffusion coefficient used in one‐dimensional chemical models of the mesosphere should be regarded as a parameterization of the transport by the meridional circulation, not as a parameterization of mixing by small‐scale diffusion.
The Milankovitch theory and climate sensitivity: 1. Equilibrium climate model solutions for the present surface conditions
Authors: Neeman Binyamin U. , Ohring George , Joseph Joachim H.
Published: February 2008

An examination of the results of climate models testing the Milankovitch theory suggests that this theory may be closely linked to the broader and as yet unresolved question of the evaluation of climate sensitivity. With this point in mind, a climate model intended to test climate sensitivity in general and the Milankovitch theory in particular is described, and its equilibrium solutions for the present surface boundary conditions are analyzed. The statistical‐dynamical hemispheric climate model is zonally averaged, with expanded longitudinal separation at the surface level, and includes topography, and detailed sea ice/snow and land snow schemes capable of simulating nonlinear effects of heat transfer through the layers of ice and snow, a modified long‐wave scheme, a provision for a variable cloud top temperature (VCT) model, and an eddy exchange parameterization connecting the eddy coefficients to the n th power of the meridional temperature gradient. The value of n in the latter relation is varied between the traditional value of 2 associated with the Green theory and a value of 4, which we believe to be more suitable for seasonal climate models of the present type. Four climate model versions are implemented with the aim of investigating three basic feedback mechanisms associated with the ice/snow albedos, the long‐wave radiation, and the meridional eddy transport, and estimating the upper bound of climate sensitivity due to their effect. The differences between the results of the four versions are rather small for the simulation of the present climate but are more than tripled for a 1% decrease in the solar constant. It is therefore concluded that an agreement with the observed fields does not automatically guarantee a correct simulation of climate sensitivity. The approach suggested by the present study is to explore a range of variability of some tunable parameters, rather than to tune these parameters to a single optimal set of values. The resulting sensitivity to a 1% decrease in the solar constant varies between 1° and 4°C in these four versions. The equilibrium response to a change between extreme high and low summer insolation orbits is a shift in the region of positive annual snow budgets, varying between 6° and 10° of latitude according to the sensitivity of the particular model version. The experiments presented in Part 1 of this study offer an estimate of the range of response of the equilibrium climate solution, leaving the investigation of the feedback effects that the building of ice sheets has on the climate system to Part 2.
Outgoing longwave radiation and its diurnal variation at regional scales derived from Meteosat
Authors: Schmetz Johannes , Liu Quanhua
Published: February 2008

The outgoing longwave radiative flux (hereafter OLR) is estimated from radiance observations in the infrared (IR: 10.5–12.5 μm) and water vapor (WV: 5.7–7.1 μ) channels aboard the geostationary satellite Meteosat 2. The OLR is obtained from the IR and WV radiance and the satellite viewing angle via a regression scheme. The scheme involves two steps. First, the narrow‐band radiances are converted into narrow‐band fluxes, using empirical limb darkening functions. Then, the OLR is computed from the narrow‐band fluxes with a third‐order polynomial. Regression coefficients were determined with a radiative transfer model. It is shown that inclusion of the WV information more than halves the rms error of the OLR retrieval, as compared to a single IR channel approach. The OLR estimation technique is applied to four regional areas: (1) marine stratocumulus in the South Atlantic; (2) Saharan desert; (3) Intertropical Convergence Zone (ITCZ) over central Africa; and (4) ITCZ over the Atlantic Ocean. All areas extend over about 800 × 800 km. The satellite data comprise observations for the full month of July 1983, with eight samples per day. Time series and monthly mean diurnal variations of the OLR are analyzed. For the stratocumulus regime we find a highly coherent diurnal range of the OLR of 6 W m−2. Over the Sahara the monthly mean diurnal range is 62 W m−2, with maximum values of 75 W m−2. In multilevel cloud situations within the ITCZ, we attempt to segregate the individual OLR contributions of the clear‐sky, low‐, medium‐ and high‐level cloud scenes. The height attribution of clouds is based on their brightness temperature (corrected for semitransparency) and climatology or forecast temperature profiles from the European Centre for Medium‐Range Weather Forecasts (ECMWF), in Reading, England. We find pronounced diurnal variations over the continental ITCZ for the altitude of high‐level cloud and the coverage with medium‐level cloud. Over the oceanic area the signal is not conclusive for high‐ and medium‐level cloud, whereas the OLR from the low‐cloud scene undergoes a clear diurnal cycle resembling the observation for marine strato‐cumulus.