bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of sea ice parameters with the NIMBUS 7 SMMR
Authors: Cavalieri D. J. , Gloersen P. , Campbell W. J.
Published: February 2008

A method of determining sea ice parameters using dual‐polarized multispectral radiance data obtained with the NIMBUS 7 Scanning Multichannel Microwave Radiometer (SMMR) is presented. Sea ice concentration is determined both at a 60‐km resolution from the polarization at the 1.7‐cm wavelength and at a 30‐km resolution using the polarization at the 0.81‐cm wavelength. Multiyear sea ice fraction is obtained from the spectral gradient ratio, which is the difference of the 0.81 cm and the 1.7 cm vertically polarized radiances divided by their sum. In addition, an ice temperature is calculated from the 4.6‐cm vertical channel radiances. The use of radiance ratios greatly reduces uncertainties in the derived parameters resulting from temporal and horizontal spatial variations of ice temperature. Observed SMMR radiances from selected areas in the Arctic region for the period February 3–7, 1979, are used in computing algorithm coefficients. Polar maps of sea ice concentration, multiyear fraction, and ice temperature are illustrated for this period. The variation of the mean and standard deviation of ice concentration and multiyear ice fraction for a region of perennial ice cover over the first 11 months of SMMR operation is also presented. The standard deviation about the mean for the computed concentration varies from 2 to 5% over the 11‐month period, while that of the multiyear fraction is about 8% for all but the summer months. Discrimination between first‐year and multiyear sea ice during the summer period is indeterminate largely because the general surface melt conditions mask the distinguishing properties of the two ice types. Based on the time variation of ice concentration and multiyear fraction for the central Arctic region and on an analysis of histograms of these parameters, the precision of the calculated ice concentration is estimated to be in the range of 5–9% and that of the multiyear fraction in the range of 13–25%. Comparisons are made between the calculated sea ice parameters and information obtained from previous studies using aircraft, submarine, and surface observations. From these comparisons it is concluded that the absolute accuracy of the SMMR parameters remains uncertain. The precision of the sea ice concentration is sufficient to provide useful data on the large‐scale polar ice cover, but further study is required to increase the confidence in the multiyear ice fraction which at present contains significant uncertainties.
Land surface temperature measurements from the split window channels of the NOAA 7 Advanced Very High Resolution Radiometer
Authors: Price John C.
Published: February 2008

The Advanced Very High Resolution Radiometer (AVHRR) on the NOAA 7 satellite acquires 1‐km spatial resolution data in “split window” channels at 10.8 and 11.9 μm. Data from these spectral channels may be used to estimate surface temperature and the atmospheric correction to radiation from the earth's surface. Analysis of a data set from July 1981 shows that (1) there is satisfactory agreement between the equation resulting from radiative transfer theory and the atmospheric correction algorithm as obtained by analysis of an area of incipient cloud street formation; (2) agreement is also satisfactory between this algorithm and the statistically derived NOAA algorithm used to obtain sea surface temperatures from the satellite data (However, the comparison assumes the NOAA algorithm is valid outside its range of derivation.); (3) in areas of cloud street formation, variations of atmospheric moisture produce radiance temperature differences of order 2–3°C, which if neglected would cause errors in the derivation of surface thermal characteristics. This meteorological variation over distances of 5–10 km would not be inferred from conventional radiosonde measurements or from lower‐resolution satellite soundings.
A study of the dynamics of drought initiation using a global general circulation model
Authors: Voice M. E. , Hunt B. G.
Published: February 2008

A global circulation model has been used to explore observed relationships between cold sea surface temperature anomalies in the Australian region and drought over the Australian continent. The model employed a comprehensive physics package, was set up for fixed January conditions, and used climatological sea surface temperatures. Two experiments were performed: one involving a large cold sea surface temperature anomaly located north of Australia but extending well into the Pacific and Indian Oceans, together with a much smaller cold anomaly in the tropical Atlantic; the other added a warm anomaly in the tropical eastern Pacific to the previous anomalies. The overall results were very similar in the two experiments. Droughtlike conditions were produced over parts of Australia, southern Africa, South America, and North America. By relating variations in evaporation and precipitation rates to changes in the synoptic meridional velocity distribution, a reasonably coherent understanding of the model's responses to the anomalies was obtained. The dominant response was in the Australian region, with secondary responses being produced over southern Africa and South America. This might indicate some form of synchronous behavior over the continents of the southern hemisphere to such sea surface temperature anomalies. The tropical easterlies were enhanced by the SST anomalies, resulting in a single westerly duct remaining between the two hemispheres. Difference charts of the 200‐mbar height field for the anomaly and control experiments revealed a weak wave train that originated in the duct region and propagated to North America, where it apparently caused large changes in the synoptic conditions over North America. Overall the experiments help to establish a cause‐and‐effect relationship between cold sea surface temperature anomalies and drought in the adjacent Australian region together with a re‐inforcement of these effects when an El Nino type warm anomaly is located in the east Pacific. Nevertheless, the need is highlighted for much further research before the requirements for forecasting drought can be assessed.
Diurnal variations of atmospheric nitric oxide: Ground‐based infrared spectroscopic measurements and their interpretation with time‐dependent photochemical model calculations
Authors: Rinsland C. P. , Boughner R. E. , Larsen J. C. , Stokes G. M. , Brault J. W.
Published: February 2008

Total vertical column amounts of NO have been derived from infrared solar absorption spectra recorded near sunrise and sunset with the 0.01‐cm−1 resolution Fourier transform interferometer at the National Solar Observatory on Kitt Peak (elevation 2095 m, latitude 31.9°N) on February 23, 1981. The results show an increase in NO concentration in the morning, late afternoon values about 40% higher than in the morning, and a decrease in NO concentration prior to sunset. The measured diurnal changes in the total vertical column amount are compared with values obtained from time‐dependent photochemical calculations.
Deuterium and oxygen 18 in precipitation: Modeling of the isotopic effects during snow formation
Authors: Jouzel Jean , Merlivat Liliane
Published: February 2008

The classical Rayleigh model assuming isotopic equilibrium fails to explain the deuterium and oxygen 18 contents of polar snow. This model leads to too high temperature‐isotope gradients (both for δD and δ18O), to too low δD ‐ δ18O slopes, and consequently to an excessively large range of deuterium excess values (d = δD ‐ 8δ18O). We present a new model that takes into account the existence of an isotopic kinetic effect at snow formation as a result of the fact that vapor deposition occurs in an environment supersaturated over ice. This kinetic effect is thoroughly discussed from a microphysical point of view and tested against experimental data and field observations. This new formulation reconciles predicted and observed values both for the temperature‐isotope and δD ‐ δD18O relationships for reasonable values of supersaturation over ice.
An evaluation of optical particle counter measurements of the dry deposition of atmospheric aerosol particles
Authors: Katen Paul C. , Hubbe John M.
Published: February 2008

Eddy correlation flux measurements of total atmospheric aerosol particulates were collected over a grass surface at Champaign, Illinois, in June 1982. PMS ASAS‐300A and Royco 225 optical particle counters were used as sensors to measure fluxes in four size ranges from 0.15 to 2.5 μm. The fluxes were quite variable, both in time and between sensors. The sensor signals are also quite noisy, but we demonstrate that, with certain limitations, the sensor systems are suitable for making flux measurements. This variability in the flux measurements is, in part, a result of the sensor noise and is also at times possibly the result of the transport through vertical moisture gradients, flux divergence, and changes in particulate concentration. However, frequent occurrences of upfluxes indicate it is also possibly the result of organic emissions from the surface. Ensemble average deposition velocities for each sensor were negative and quite small and, in most cases, not statistically significant. However, daily average values were often quite large and negative and showed good agreement between sensors.
Isotopic diffusion in cold snow and firn
Authors: Whillans I. M. , Grootes P. M.
Published: February 2008

Molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion. Diffusion through or along the ice matrix is slow, whereas diffusion from the air to within separate grains is comparatively rapid. Thus mixing occurs in the vapor phase, and exchange with the local ice involves all the water molecules. A quantification of these concepts is applied to the diffusion of oxygen‐isotopic depth profiles in southern Greenland and at Dome C, Antarctica. It successfully describes the smoothing of measured profiles. The smoothing rate is strongly dependent on temperature and density of the firn.
Trace gas trends and their potential role in climate change
Authors: Ramanathan V. , Cicerone R. J. , Singh H. B. , Kiehl J. T.
Published: February 2008

This study examines the potential climatic effects of the radiatively active trace gases that have been detected in the atmosphere including chlorofluorocarbons, chlorocarbons, hydrocarbons, fluorinated and brominated species, and other compounds of nitrogen and sulfur, in addition to CO2 and O3. A one‐dimensional radiative‐convective model is used to estimate trace gas effects on atmospheric and surface temperatures for three cases: (1) modern day (1980) observed concentrations are adopted and their present trends are extrapolated 50 years into the future. These projections are based on analyses of observed trends and atmospheric residence times; (2) the preindustrial to present increase in CO2 and other trace gases are inferred from available observations; (3) a hypothetical increase of 0–1 ppbv is considered to provide insights into the radiative processes. Trace gases other than CO2 are shown to be potentially as important as CO2 for long‐term climate trends. The relative importance of the 30 or so trace gases included in this study depends on the problem under consideration. The inferred CO2 increase from preindustrial to the present causes an equilibrium warming of the model surface by 0.5 K, which is amplified by 50% by CH4, CFCl3 (F11), CF2Cl2 (F12), and tropospheric ozone. For the projected increase from year 1980 to 2030, the other trace gases amplify the estimated CO2 warming of 0.7 K by about 110%: CFCl3, CF2Cl2, ozone, and CH4 each contribute in the 0.1–0.2 K range followed by N2O, CHClF2 (F22), CH3CCl3, and CCl4 in the 0.03–0.1 K range. Finally, on a per ppb basis, about 12 trace gases are identified to be important: CBrF3, C2F6 (F116), CHF3, and CF3Cl (F13) have greenhouse effects comparable to those of CFCl3 (F11) and CF2Cl2 (F12). The narrow‐band overlap treatment and the accurate spectral and angular integration techniques employed in the present radiation model enable quantitative interpretation of the differences between various published estimates for the greenhouse effects of CFCl3 and CF2Cl2. For the projected trace gas increase, we compute the stratospheric O3 change by employing a photochemical model coupled to the radiative‐convective model. The O3 change cools the stratosphere and the magnitude of the cooling is as large as that due to the projected CO2 increase. Because of the O3‐induced stratospheric cooling and the surface warming due to the greenhouse effect, the trace gas effects on climate are virtually indistinguishable from those of CO2.
Global atmospheric CO2 distribution and variations from 1968–1982 NOAA/GMCC CO2 flask sample data
Authors: Komhyr W. D. , Gammon R. H. , Harris T. B. , Waterman L. S. , Conway T. J. , Taylor W. R. , Thoning K. W.
Published: February 2008

CO2 data obtained from discrete sampling during 1968–1982 at 23 National Oceanic and Atmospheric Administration/Geophysical Monitoring for Climatic Change and foreign cooperative stations are presented, together with a description of the measurement program and data quality. Monthly, seasonal, and annual CO2 concentrations are determined by the individual stations from select (background) data. Temporal and spatial global CO2 distributions yield annual and seasonal latitudinal gradients, abundances, airborne fractions, annual cycle amplitudes and phases, annual cycle amplitude growth rates, and global growth rate variations of CO2. The time‐series data sets reveal variations related to several El Niño/Southern Oscillation events, particularly with respect to the strength of the CO2 source in the equatorial Pacific Ocean and global CO2 growth rates. CO2 growth rate anomalies correlate highly with the Southern Oscillation Index, which is related to the strength of the easterly trade winds that blow along the equator.
Airborne Doppler radar velocity measurements of precipitation seen in ocean surface reflection
Authors: Atlas David , Matejka Thomas J.
Published: February 2008

Airborne Doppler radar measurements over the ocean reveal mirror images of precipitation echoes in reflection from the ocean surface at their virtual positions “below” the surface. Because the detected vertical component of the precipitation motion changes sign on reflection, the velocity field in the reflection appears shifted by amounts depending on the mean reflectivity‐weighted hydrometeor fall speed, wind speed, and viewing angle. The shift of the zero‐velocity isotach, for example, from the upwind side of the aircraft in the direct echoes to the downwind side in the mirror image is readily observed. With two views of each precipitation volume, one direct and the other in mirror image, one may solve for both a horizontal wind component and the net mean particle fall speed. These components may thereby be mapped in an appreciable volume. Measurements of divergence may be made by either flying or scanning the beam in a circle. The availability of mean fall speed with radar reflectivity provides a promising two‐parameter system for improved measurements of rainfall rate. The airborne radar also provides measurements of the normalized radar backscatter cross section at all angles from nadir to glancing incidence, thus providing a variety of estimates of ocean surface properties and winds. The availability of direct Doppler wind measurements using echoes from either precipitation or chaff provides a much needed “ground truth” system for the radar used as a scatterometer or for corresponding observations from space.
Quantitative estimation of global circuit
Authors: Makino Masahiko , Ogawa Toshio
Published: February 2008

Quantitative estimations of the global circuit parameters have been made to test the terrestrial and/or extraterrestrial controls of the global atmospheric electric circuit. A global model of electrical conductivity in the lower atmosphere between 0 and 60 km was constructed first. In this model we consider the ionization caused by cosmic rays and radioactive substances and attachment of ions to condensation nuclei or cloud particles. The responses of the atmospheric electrical parameters to the variations of the cosmic ray ionization and the condensation nuclei concentration were then examined. In the first case, when the cosmic ray ionization decreases by 20%, the ionospheric potential increases by 15%, and the electric fields above the ocean and the continent increase by 20% and 7%, respectively. On the other hand the global current does not increase so much (0.8%), and the air‐earth current decreases by 0.7% above the ocean but increases by 3% above the continent. This difference between responses above the ocean and above the continent is caused by the ionization resulting from the radioactive substances over the continent. In the second case, when the condensation nuclei concentration increases by 20%, the ionospheric potential increases by 8%, and the electric field increases in the nonmountain region more than in the high mountain region, while the air‐earth current increases obviously in the high mountain region.
Computed response of the space charge layer created by corona at ground level to external electric field variations beneath a thundercloud
Authors: Chauzy Serge , Rennela Christian
Published: February 2008

The present numerical simulation deals with ion creation by corona at ground level and their evolution between the ground and the thundercloud. The study starts from a previous model in which the external electric field was constant in time. As an extension, the new model includes several types of variation of the external electric field responsible for ion creation. The following phenomena are taken into account: (1) ion creation of both polarities (bipolar medium), (2) capture of small ions by neutral aerosol particles as well as by other ions of opposite polarity, and (3) influence of turbulent diffusion. The model provides the transient response of the space charge to two types of variation of the electric field created by a thundercloud: the rapid variation due to a lightning stroke and the slow recovery which occurs during regeneration. Time and space evolution of the various parameters are deduced from the computation: small and large ion concentrations, space charge density, and electric field. The different results reveal the tremendous influence of the space charge on the electric field variation at ground level, especially after a lightning stroke. Pulses of corona current higher than 20 nA m−2 following 20 kV m−1 field steps can create such a high ion concentration that the surface electric field can be rapidly reduced to a value close to the corona threshold regardless of the intensity aloft. Electric field profiles plotted after a lightning stroke often show opposite polarities of the electric field at ground level and aloft.
Tropospheric ozone: Seasonal behavior, trends, and anthropogenic influence
Authors: Logan Jennifer A.
Published: February 2008

We present an analysis of data for tropospheric ozone with a focus on spatial and temporal variations. Surface ozone at mid‐latitudes displays two modes of seasonal behavior: a broad summer maximum within a few hundred kilometers of populated and industrialized regions in Europe and the United States and a minimum in summer or autumn in sparsely populated regions remote from industrial activity‐in Tasmania and Canada for example. The current data base for different regions, in combination with limited historical data, indicates that summertime concentrations of ozone near the surface in rural areas of Europe and the central and eastern United States may have increased by approximately 6–22 ppb (20%–100%) since the 1940's. The seasonal cycle of ozone in the middle troposphere over Europe, the United States, and northern Japan is very similar to that at the surface with a summer maximum, but it is quite different from that at 300 mbar, which is characterized by a maximum in spring. There is good evidence for an increase in ozone in the middle troposphere over Europe during the past 15 years and weaker evidence for a similar increase over North America and Japan. The increase in tropospheric ozone contributes significantly to the trend in the column of ozone and may compensate for 20%–30% of the decrease in ozone in the stratosphere over middle and high latitudes of the northern hemisphere. We argue that the summer maximum in ozone and the observed trends are due to photochemical production associated with anthropogenic emissions of NOx, hydrocarbons, and CO from combustion of fossil fuels. A strong seasonal variation in ozone observed at Natal, Brazil (6°S), may also result from emissions of NOx and hydrocarbons, in this case from agricultural burning. Maximum concentrations at Natal are similar to values found at mid‐latitudes in summer. Tropical ozone exhibits strong spatial and temporal variability.
Measurements of OCS and CS2 in the free troposphere
Authors: Carroll Mary Anne
Published: February 2008

Distributions of the ambient atmospheric mixing ratios of OCS and CS2 were determined from grab samples collected at altitudes ranging from 6 to 8 km (20,000 to 26,000 feet) during an aircraft flight between San Juan, Puerto Rico, and Albany, New York (July 11–12, 1982). No spatial variation is observed for OCS mixing ratios at these altitudes and latitudes within the uncertainty of the collection and analysis techniques. The average OCS mixing ratio is 517±65 pptv, where the standard deviation includes atmospheric as well as experimental variability. CS2 values, on the other hand, show considerable spatial variability that may be correlated with intense local cumulonimbus activity.
Latitudinal variation of spectral optical thickness and columnar size distribution of the El Chichon stratospheric aerosol layer
Authors: Spinhirne James D. , King Michael D.
Published: February 2008

Multiwavelength solar radiometer observations of directly transmitted solar radiation have been obtained at 10 discrete wavelengths between 0.440 and 2.233 μm during an airborne latitudinal survey in late April and early May 1983. These observations have been used to derive the spectral optical thickness of the El Chichon stratospheric aerosol layer from 68°N to 56°S. The stratospheric optical thicknesses 1 year after the eruptions of El Chichon were still greatly enhanced over background levels for the stratosphere. The maximum optical thickness of 0.14 (0.670‐μm wavelength) was found at 50°N, rather than at 20°N as was found during an airborne latitudinal survey in late October and early November 1982. Columnar aerosol size distributions have been inferred from the 1982 and 1983 data sets by numerically inverting the aerosol optical thickness measurements as a function of wavelength. In May 1983, latitudes north of 5°S had bimodal stratospheric aerosol size distributions, while latitudes south of 5°S had monomodal size distributions. During October 1982, when optical thickness measurements were obtained only from 0.440 to 0.871 μm, the size distributions showed a strong latitudinal variation but were everywhere monomodal. For both dates the northern hemisphere distribution indicated a significantly higher ratio of large particles to small particles than the southern hemisphere distribution. The addition of the near‐infrared wavelengths in the May 1983 experiment increased the accuracy of the size distribution determinations at the large‐particle end of the spectrum, as anticipated, but was also found to increase the accuracy at the small‐particle end.
Sources of atmospheric trace metals over the subtropical North Atlantic
Authors: Schneider Bernd
Published: February 2008

Air filter samples were taken over the subtropical North Atlantic under the temporary influence of a Saharan dust plume. Analyses for trace metals showed that most of the determined elements (Al, Sc, Cr, Fe, Co, Zn, Cs, La, Ce, Sm, and Th) were predominantly of crustal origin. Additionally, for Mn and Se a significant marine contribution could be detected.
Atmospheric dust in polar ice and the background aerosol
Authors: Gayley Robert I. , Ram Michael
Published: February 2008

We have measured insoluble particle size distributions covering the radius range 0.05–1.31 μm for 15 samples from a 3‐year (1782–1785) section of ice core from Crête, central Greenland, and for a 2500‐year‐old, 2‐year section of south pole ice. We predict that 60% of all the insoluble particles in this range in the northern hemisphere background aerosol are in the radius range 0.05–0.13 μm, 30% are in the range 0.13–0.38 μm, and 10% are in the range 0.38–1.31 μm. The corresponding values for the southern hemisphere are 74, 22, and 4%. Also, we have found that the small and large particle profiles for our Crête ice core section show similar variability features, but peaks in the large particles are much more pronounced.
Concentrations and uncertainties of stratospheric trace species inferred from limb infrared monitor of the stratosphere data: 2. Monthly averaged OH, HO2, H2O2, and HO2NO2
Authors: Kaye Jack A. , Jackman Charles H.
Published: February 2008

Monthly, zonally averaged limb infrared monitor of the stratosphere data from the Nimbus 7 satellite are used with an essentially algebraic photochemical equilibrium model presented in part 1 of this series (Kaye and Jackman, this issue) to infer concentrations and uncertainties of the odd hydrogen species OH, HO2, H2O2, and HO2NO2 as a function of altitude, latitude, and season. The inferred concentrations for OH and H2O2 are found to be reasonably consistent with some but not all previous observations; most of the inferred HO2 concentrations are below those which have been observed. Concentrations of all inferred species at mid‐latitudes are expected to maximize in the summer. Uncertainties ui are found to be largest in the lower stratosphere for all species and to decrease approximately in the order uH2O2 > uHO2NO2 > uHO2 > uOH over most of the stratosphere. In the tropics and at mid‐latitudes the variation of the uncertainties with latitude and season is substantially smaller than the inferred variation of the concentrations.
Evolution of potential vorticity in the winter stratosphere of January‐February 1979
Authors: Dunkerton Timothy J. , Delisi Donald P.
Published: February 2008

Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) observations are used to study the evolution of potential vorticity in the stratosphere, January–February 1979. Daily analysis of this quantity at 850° and 1200°K provides circumstantial evidence of planetary wave “breaking” by which air parcels undergo rapid and irreversible separation from the circumpolar vortex during stratospheric warmings. Complementing this effect is the advection of subtropical, low‐vorticity air into the polar region. Temporal evolution of the size, shape, and orientation of the main circumpolar vortex is revealed very clearly by the potential vorticity field. All three factors are important, although some have been emphasized more strongly in previous literature. The size of the vortex determines the range of latitudes over which planetary Rossby waves are able to propagate vertically. Diminution of vortex area during the observed warmings is believed to precondition the flow, focusing subsequent Rossby wave activity into the polar cap, as in the major warming of late February 1979. The shape of the vortex undergoes both reversible and irreversible deformation. Examples of irreversible deformation are seen in the advective formation of extended high‐vorticity tongues over subtropical latitudes in connection with the warmings of late January, early February, and late February 1979. Two of these were recently discussed by McIntyre and Palmer. Reversible deformation is observed in the sudden cooling and concurrent wave 1, wave 2 vacillation, after the January warming. The orientation of the vortex can also be important, as in the period of rotation leading up to the major wave 2 warming of late February 1979. We suggest that the orientation of the vortex be included as part of the preconditioning process, in accord with numerical results of Butchart et al. We briefly consider the vertical structure of potential vorticity and ozone on two disturbed days in late January 1979. Meridional cross sections of potential vorticity in the middle stratosphere resemble ozone cross sections shown in the work of Leovy et al. and exhibit good vertical coherence extending into the lower mesosphere, where ozone (unlike potential vorticity) no longer serves as a tracer of the motion.
Doppler ducting of atmospheric gravity waves
Authors: Chimonas G. , Hines C. O.
Published: February 2008

Atmospheric gravity waves are subject to horizontal ducting in a stably stratified atmosphere that contains levels of wind maximum or minimum, quite apart from any superimposed consequences of vertical variation of stability and quite apart from the existence or otherwise of critical levels. The process, “Doppler ducting”, is examined here for two prototype cases (an isolated wind maximum and a wind minimum at ground level) and for two more realistic model cases (a strong tropospheric jet and a nocturnal boundary layer jet). The wave structure, modal behavior, and dispersion curves of all four are very similar. It is argued that Doppler ducting is available to a part of the gravity wave spectrum in all real circumstances and that it should be considered as a possible candidate whenever observations indicate that some ducting process is operative. One particular wave event is discussed in some detail, and it is shown that Doppler ducting in its simplest form provides a plausible alternative to a more complicated ducting process (which involved critical levels and energy leakage) previously inferred. Doppler ducting is available equally to gravity waves in the oceans when background currents vary with depth.
Results of spatial and temporal characterization of the VHF‐UHF radiation of lightning
Authors: Richard P. , Delannoy A. , Labaune G. , Laroche P.
Published: February 2008

A 300‐MHz interferometric imaging system has been used for the characterization of the VHF‐UHF electromagnetic radiation from lightning flashes. Results are presented, with emphasis on typical phenomenology, in particular through correlations with the electrical activity description from an E field sensor network. At the microsecond time scale the VHF‐UHF radiation appears impulsive, either as low rate pulsed emissions or as bursts of pulses. The low‐rate emissions (below 20 pulses/ms) are usually present during important intracloud charge transfers and correspond to spread out sources over distances of the order of 1 km. The bursts last from several hundred microseconds to a few milliseconds, and they are associated with highly organized propagations of sources in the 107‐m/s velocity range extending over distances of several kilometers. They appear in all phases of the lightning flash and are not associated with large charge transfers. Their spatial evolution and chronology with respect to the electrical phenomenology, in particular during precursor phenomena, indicate a decorrelation between electromagnetic phenomenology and the typical electrical phenomenology.
In situ stratospheric ozone measurements by long path UV absorption: Developments and interpretation
Authors: Weinstock Elliot M. , Schiller Craig M. , Anderson James G.
Published: February 2008

A high‐sensitivity, in situ UV absorption ozone sensor has been developed for use in the stratosphere. The instrument couples 254‐nm radiation from a low‐pressure mercury discharge lamp into a 40‐pass White cell (1200‐cm pathlength) to attain a high‐sensitivity ozone absorption measurement. Preflight/postflight laboratory tests utilizing an ozone source coupled to a laboratory UV ozone photometer in a fast‐flow system as well as in‐flight diagnostics verify the successful operation of the instrument. We present evidence to verify that in situ UV absorption ozone photometers can measure stratospheric ozone with better than 3% precision and 5% accuracy, provided proper attention is given to both the thermal field surrounding the gondola and the ambient pressure measurements. We compare our ozone data with modeled profiles in the 28‐ to 40‐km region. An assessment of the disagreement between observations and modeled profiles is given along with suggestions for future experiments designed to constrain photochemical models.
Coupled stratospheric ozone and temperature responses to short‐term changes in solar ultraviolet flux: An analysis of Nimbus 7 SBUV and SAMS data
Authors: Hood L. L.
Published: February 2008

The nature of stratospheric ozone and temperature responses to changes in solar ultraviolet flux occurring at low latitudes on the time scale of the solar rotation period is investigated using 22 months of Nimbus 7 solar backscattered ultraviolet (SBUV) ozone and stratosphere and mesophere sounder (SAMS) temperature data. After filtering to remove periods ≳35 days, average cross‐correlation functions for low‐latitude residual ozone versus SBUV measurements of the solar irradiance at 205 nm are largest (R = 0.3–0.6) at phase lags ranging from −3.6 ± 0.6 days at 0.7 mbar to 3.2 ± 0.5 days at 10 mbar. Maximum correlation coefficients for residual temperature variations (R = 0.2–0.35) are obtained versus the 205‐nm flux at lags ranging from 3.6 ± 0.9 days at 0.3 mbar to 13.0 ± 0.7 days at 10 mbar. In both cases, correlations generally increase when the 205‐nm flux is used as the solar ultraviolet variable rather than proxy indicators such as the 10.7‐cm flux. The consistency between response estimates calculated for separate latitude bands and the tendency for correlation coefficients to be larger during time periods of relatively strong 27‐day solar ultraviolet flux variations supports a causal relationship. Linear regression analyses are therefore performed to determine mean ozone and temperature response amplitudes for given changes in the 205‐nm flux at low latitudes as a function of pressure level in the upper stratosphere. Peak‐to‐peak variations in the 205‐nm flux were as large as 6% on the solar rotation time scale during the study period, yielding maximum ozone responses of 3% (∼0.37 μg g−1) near 3 mbar and maximum temperature responses of 0.36% (∼1 K) near the stratopause. The observed ozone and temperature responses and their phase lags are interpreted, using a model that accounts to first order for the coupled behavior of solar‐induced ozone and temperature perturbations in the upper stratosphere and lower mesosphere. The model appears capable of accounting for gross features of the observed ozone and temperature responses, including the negative ozone phase lags relative to the 205‐nm flux found above 3 mbar. Using the measured response amplitudes and phase lags, the model is applied to estimate the change in O2 photolysis rate in the upper stratosphere produced by a given change in the 205‐nm flux on the considered time scale. The mean temperature dependence of perturbation‐order ozone concentration changes is also constrained by the data.
Upper stratospheric (30–50 km) lidar observations of the ozone vertical distribution
Authors: Pelon J. , Godin S. , Mégie G.
Published: February 2008

A maximum reduction of 20% of the ozone content in the altitude range 35–45 km is presently expected within the next 50 years. Early detection of trends is thus of particular importance to confirm such extrapolations. An active lidar system, which uses a powerful exciplex laser as the emitting source at 308 nm, has been operated at the Observatoire de Haute Provence to probe the upper stratospheric ozone distribution. A description of the lidar system and results of the measurements are given and compared with those obtained simultaneously by already proven techniques, such as Brewer‐Mast sondes and Umkehr spectroscopic measurements. A general agreement within the uncertainties of the various methods is found. The data are further analyzed to determine a total error budget and to extrapolate the potentiality of lidar systems, using up‐to‐date laser sources to reach a precison better than 3% in the considered altitude range.
Solar ultraviolet irradiance variations: A review
Authors: Lean Judith
Published: February 2008

Despite the geophysical importance of solar ultraviolet radiation, specific aspects of its temporal variations have not yet been adequately determined experimentally, nor are the mechanisms for the variability completely understood. Satellite observations have verified the reality of solar ultraviolet irradiance variations over time scales of days and months, and model calculations have confirmed the association of these short‐term variations with the evolution and rotation of regions of enhanced magnetic activity on the solar disc. However, neither rocket nor satellite measurements have yet been made with sufficient accuracy and regularity to establish unequivocally the nature of the variability over the longer time of the 11‐year solar cycle. The comparative importance for the long‐term variations of local regions of enhanced magnetic activity and global scale activity perturbations is still being investigated. Solar ultraviolet irradiance variations over both short and long time scales are reviewed, with emphasis on their connection to solar magnetic activity. Correlations with ground‐based measures of solar variability are examined because of the importance of the ground‐based observations as historical proxies of ultraviolet irradiance variations. Current problems in understanding solar ultraviolet irradiance variations are discussed, and the measurements planned for solar cycle 22, which may resolve these problems, are briefly described.
A fast radiation parameterization for atmospheric circulation models
Authors: Harshvardhan  , Davies Roger , Randall David A. , Corsetti Thomas G.
Published: February 2008

Several currently available broadband parameterizations for longwave and shortwave radiation have been combined to produce a computationally fast radiation parameterization that is well suited for atmospheric circulation models. The main features of the parameterization are the ability to include overlapping partly cloudy layers in the longwave, the use of a delta‐Eddington technique to treat clouds in the shortwave, and a computational structure that is amenable to vectorization on supercomputers. Selected results of off‐line one‐dimensional computations using the code have been compared with more rigorous methods as part of an international intercomparison program and found to be quite accurate.
Variations in radon 222 daughter concentrations in surface air with atmospheric stability
Authors: Fujinami Naoto , Esaka Shinobu
Published: February 2008

Simultaneous measurements of short‐lived radon daughter concentrations and atmospheric stability in surface air have been continuously made at a site near the Japan Sea coast for a period of about 1 year. The atmospheric stability is related more closely to the concentration difference with respect to time than to the concentration level at that time.
Meteorological context for fall experiments including distributions of water vapor, ozone, and carbon monoxide
Authors: Danielsen Edwin F. , Gaines Steven E. , Hipskind R. Stephen , Gregory Gerald L. , Sachse Glen W. , Hill G. F.
Published: February 2008

Meteorological contexts for the NASA GTE/CITE 1 fall 1983 flight series are presented and discussed. The large‐scale wind, cold cloud, and moisture patterns are illustrated by composite diagrams based on the National Oceanic and Atmospheric Administration 700‐, 500‐, and 250‐mbar analyses and the GOES‐West broadband and 6.7‐μm (water vapor) infrared photographs. Detailed flight path diagrams are included for seven maritime flights and one continental flight in the free troposphere and boundary layer. For three flights from Hickam Field, in Honolulu, Hawaii, to the Intertropical Convergence Zone, vertical profiles of temperature, dew/frost point departures, wind velocity, and ozone, and carbon monoxide mixing ratios also are presented and discussed. Excellent agreement is demonstrated between the in situ and remote measurements. In particular, the predictive and diagnostic value of the 6.7‐μm water vapor photographs is demonstrated.
An estimate of the NOx production rate in electrified clouds based on NO observations from the GTE/CITE 1 fall 1983 field operation
Authors: Chameides W. L. , Davis D. D. , Bradshaw J. , Rodgers M. , Sandholm S. , Bai D. B.
Published: February 2008

During the NASA GTE/CITE 1 fall 1983 airborne field operation the NASA Convair 990 penetrated the anvils of two active cumulonimbus clouds. While NO levels outside the anvils averaged about 20 parts per trillion per volume (pptv), the average NO inside the anvils was about 440 pptv. Extrapolation of this observation along with data on the amount of air typically advected out of cumulonimbus clouds and the total number of thunderclouds occurring over the globe at any moment, implies a rate of nitrogen fixation in electrified clouds of about 7×106 t/yr. Although the data base used to make this estimate is quite limited, our approach differs from that used in previous studies of the global production of nitrogen oxides by lightning and thus represents an independent assessment of the role of electrified clouds in the atmospheric nitrogen oxide budget.
Nimbus 7 earth radiation budget wide field of view climate data set improvement: 1. The Earth albedo from deconvolution of shortwave measurements
Authors: Hucek Richard R. , Kyle H. Lee , Ardanuy Philip E.
Published: February 2008

A deconvolution technique to recover the daily average earth albedo from a set of wide field of view (WFOV) satellite measurements is presented. For each shortwave observation in space a corresponding synthetic WFOV integral is formulated to simulate the satellite value. This is done by including the known earth‐sun‐satellite geometry and a compromise diurnal model, depicting reflection from the earth‐atmosphere system as isotropic and occurring at an effective top of the atmosphere (TOA), and by representing the unknown albedo field as a truncated series of spherical harmonic functions. The series expression for the albedo reduces the measurement integral to a linear equation in the now unknown expansion amplitudes. A typical sampling period leads to many such Satellite measurements and their associated linear representations. This system of linear equations will generally be overdetermined and is solved in a least squares sense for the expansion amplitudes and resulting albedo field. Simulation studies show that a maximum of about 289 pieces of information can be extracted from a set of Nimbus 7 WFOV satellite measurements. These correspond to the number of linearly independent modes of variation definable in the TOA albedo expansion. Zonally, variations through eight waves may be resolved and, meridionally, through 16 nodes. When compared to the current WFOV archived albedo product, the deconvolved albedo field achieves about a 20% reduction in the global rms regional reflected flux density errors. This error reduction is attained within a data collection period containing as few as 6 sampling days and remains constant for longer periods. Global mean measurements are, of course, not changed. An application of these results is used to derive the mean, daily average TOA albedo field for January 1983. An unusually strong and extensive albedo maximum is noted over the south central Pacific Ocean. It has a central maximum of 0.42 and corresponds to the El Niño/Southern Oscillation event of 1982–1983.
Ozone production in the rural troposphere and the implications for regional and global ozone distributions
Authors: Liu S. C. , Trainer M. , Fehsenfeld F. C. , Parrish D. D. , Williams E. J. , Fahey D. W. , Hübler G. , Murphy P. C.
Published: February 2008

The relationship between O3 and NOx (NO + NO2) which was measured during summer and winter periods at Niwot Ridge, Colorado, has been analyzed and compared to model calculations. Both model calculations and observations show that the daily O3 production per unit of NOx is greater for lower NOx. Model calculations without nonmethane hydrocarbons (NMHC) tend to underestimate the O3 production rate at NOx higher than 1.5 parts per billion by volume and show the opposite dependence on NOx. The model calculations with NMHC are consistent with the observed data in this regime and demonstrate the importance of NMHC chemistry in the O3 production. In addition, at eight other rural stations with concurrent O3 and NOx measurements in the central and eastern United States the daily O3 increase in summer also agrees with the O3 and NOx relationship predicted by the model. The consistency of the observed and model‐calculated daily summer O3 increase implies that the average O3 production in rural areas can be predicted if NOx is known. The dependence of O3 production rate on NOx deduced in this study provides the basis for a crude estimate of the total O3 production. For the United States an average summer column O3 production of about 1×1012Cm−2S−1 from anthropogenically emitted NOx and NMHC is estimated. This photochemical production is roughly 20 times the average cross‐tropopause O3 flux. Production of O3 from NOx that is emitted from natural sources in the United States is estimated to range from 1.9×1011 to 12×1011 cm−2 s−1, which is somewhat smaller than ozone production from anthropogenic NOx sources. Extrapolation to the entire northern hemisphere shows that in the summer, 3 times as much O3 is generated from natural precursors as those of anthropogenic origin. The winter daily O3 production rate was found to be about 10% of the summer value at the same NOx level. However, because of longer NOx lifetime in the winter, the integrated O3 production over the lifetime of NOx may be comparable to the summer value. Moreover, because the natural NOx sources are substantially smaller in the winter, the wintertime O3 budget in the northern hemisphere should be dominated by ozone production from anthropogenic ozone precursors. The photochemical lifetime of O3 in the winter in the mid‐latitude is approximately 200 days. We propose that this long lifetime allows anthropogenically produced O3 to accumulate and contribute substantially to the observed spring maximum that is usually attributed to stratospheric intrusion. Furthermore, the anthropogenic O3 may be transported not only zonally but also to lower latitudes. Thus the long‐term interannual increase in O3, observed in the winter and spring seasons at Mauna Loa, may be due to the same anthropogenic influences as the similar winter trend observed at Hohenpeissenberg, Germany.
Tidal influences on vertical diffusion and diurnal variability of ozone in the mesosphere
Authors: Bjarnason Gudmundur G. , Solomon Susan , Garcia Rolando R.
Published: February 2008

Possible dynamical influences on the diurnal behavior of ozone are investigated. A time dependent one‐dimensional photochemical model is developed for this purpose. All model calculations are made at 70°N during summer, because of available data on turbulence and zonal winds at Poker Flat, Alaska, and ozone observations from the Solar Mesosphere Explorer (SME) satellite. The model includes vertical diffusion induced by breaking gravity waves, as parameterized by Lindzen (1981). We show that the vertical diffusion can vary as much as 1 order of magnitude within a day as a result of large changes in the zonal wind induced by atmospheric thermal tides. It is found that by introducing a dissipation time scale for turbulence produced by breaking gravity waves, the agreement with Poker Flat echo data is improved. Comparisons of results from photochemical model calculations where the vertical diffusion is a function of height only with those in which Kzz is changing in time show large differences in the diurnal behavior of ozone between 70 and 90 km. By including the dynamical effect, much better agreement with the SME data is obtained. The results are, however, sensitive to the background zonally averaged wind. The influence of including time‐varying Kzz on the OH densities is also large, especially between 80 and 90 km. This suggests that dynamical effects are important in determining the diurnal behavior of the airglow emission from the Meinel bands.