bluuebunny/crossref_metadata_2025 huggingface dataset:
Insolation during STREX: 1. Comparisons between surface measurements and satellite estimates
Authors: Gautier Catherine , Katsaros Kristina B.
Published: February 2008

Comparison between measurements of insolation from pyranometers mounted on ships and estimates from satellite visible measurements during STREX are presented. In general for both hourly and daily insolation values the comparison is quite favorable. The root mean square (rms) difference between the two measurements of daily insolation was about 13 W m−2. From a detailed analysis of the errors and measurement discrepancies it was found that a large part of the difference between the two estimates of insolation could be due to inaccuracies in the surface measurements, interpolation during periods of radio interference, and ship motion. Comparisons between time‐averaged insolation values over periods of about 10 days and limited statistical analysis of the pyranometric time series suggest that, on that time scale, the accuracy of the satellite estimates is of the order of 4 W m−2. Large‐scale insolation fields derived from satellite during STREX will be presented in the companion paper (C. Gautier and S. Masse, manuscript in preparation, 1984).
A zonal mean model of stratospheric tracer transport in isentropic coordinates: Numerical simulations for nitrous oxide and nitric acid
Authors: Ko Malcolm K. W. , Tung Ka Kit , Weisenstein Debra K. , Sze Nien Dak
Published: February 2008

The use of the linear wave treatment to describe the eddy motions in a zonal mean model leads to the identification of the irreversible transient waves as the process responsible for the diffusive transport of tracers in the stratosphere. Recent estimates based on an idealized general circulation model (GCM) calculation and the observed transient wave statistics between 20°N and 80°N suggest that, in the stratosphere, the horizontal diffusion coefficient should be ≲3×109 cm2 s−1, a value about 1 order of magnitude smaller than values previously used in most two‐dimensional models. A simple model of zonally averaged transport of stratospheric trace gases in isentropic coordinates is developed to test this hypothesis of small eddy diffusion. In this model, the eddy transport arising from the irreversible transient waves is assumed to act along the isentropic surfaces and is represented by a single horizontal diffusion coefficient, Kyy. The advective transport in the model is effected by the zonal mean diabatic circulation calculated diagnostically from a given zonal mean diabatic heating rate, of which no post hoc adjustment has been attempted. We show that the observed stratospheric distribution of N2O and HNO3 may be adequately simulated in the model with small values of Kyy that are consistent with physical estimates mentioned above. The result that the observed concentrations of the stratospheric trace gases can be simulated using small values of eddy diffusion coefficients is expected to be equally applicable for models in pressure coordinates using the residual mean circulations.
Computations of ozone transport using Nimbus 7 solar backscatter ultraviolet and NOAA/National Meteorological Center data
Authors: Wu Mao‐Fou , Geller Marvin A. , Olson Jerry G. , Miller Alvin J. , Nagatani Ronald M.
Published: February 2008

The ozone fluxes and flux convergences within the region between 30 and 0.4 mbar for the Northern Hemisphere are investigated for the period January 1 to March 31, 1979, using Nimbus 7 solar backscatter ultraviolet ozone profiles and the meteorological data derived from NOAA satellites. The results indicate that large contributions to the ozone transport and the transport convergence are due to mean vertical advection and horizontal eddy processes. The contribution from the vertical eddies is insignificant. The transport of ozone into the polar latitudes during winter and early spring is mainly accomplished by the large‐scale horizontal eddies. The results also show that more ozone is transported into the polar region by the large‐scale eddies on disturbed days than on quiet days.
A diabatic circulation two‐dimensional model with photochemistry: Simulations of ozone and long‐lived tracers with surface sources
Authors: Stordal Frode , Isaksen Ivar S. A. , Horntveth Kjell
Published: February 2008

A two‐dimensional zonally averaged time dependent model is developed to describe the transport and chemical transformations of species in the troposphere and the stratosphere. The constituents are advected by the residual Eulerian circulation, which is shown to equal the diabatic circulation under certain circumstances. Prescribed values of temperatures and diabatic heating rates are used to calculate the diabatic velocities. Slow diffusion, with Kyy = 3 × 109 cm2 s−1 and Kzz = 103 cm2 s−1, is included in the tracer transport calculations in the stratosphere, to simulate mixing due to wave transience. High diffusion coefficients are used in the troposphere. We show that the observed distribution of ozone is adequately reproduced in the model. In early spring, when the ozone columns attain the maximum values at middle and high latitudes, deviations from observations are 5–10% for all latitudes in the northern hemisphere. Stratospheric water vapor, which is extremely sensitive to the latitude of transport across the tropopause, is also well reproduced. Studies of the global atmospheric lifetimes for CF2Cl2, CFCl3, and CCl4 confirm that the strength of the global circulation is realistic in the model. Model experiments are performed with the recently measured low values of oxygen cross sections in the Herzberg continuum as well as with previous high values. In most cases, including ozone calculations, the low values improve the model results.
The variability of carbon monoxide in the terrestrial mesosphere as determined from ground‐based observations of the J = 1 → 0 emission line
Authors: Bevilacqua Richard M. , Stark Antony A. , Schwartz Philip R.
Published: February 2008

We report two single‐day spectral observations of the terrestrial J = 1 → 0 CO emission line (January 28, 1982, and April 18, 1984). We use these observations to deduce the mesospheric CO mixing ratio profile. The measurements were obtained by using the 7‐m Cassegrain antenna located at the AT&T Bell Laboratories (millimeter‐wave) Observatory in Holmdel, New Jersey (latitude, 40.4°). The CO mixing ratios in the lower mesosphere inferred from the January 1982 observation are larger by a factor of 10–100 than those indicated by previous measurements, while the April 1984 observation is in good agreement with previous work. Thus our measurements indicate that the abundance of CO in the mesosphere can be extremely variable.
Ice crystal interactions with a riming target: Charge transfer and collection efficiencies
Authors: Saunders C. P. R. , Wheeler M. F. S. , Jallo N. , Jayaratne E. R.
Published: February 2008

Recent laboratory studies have shown that the sign and magnitude of electric charge transferred to a riming pellet of soft hail when ice crystals collide then separate are sensitive functions of the cloud liquid water content and the temperature. Certain differences between these results, obtained with crystal/rimer relative velocities of ∼3 m s−1, and those of other workers at ∼10 m s−1 have been reconciled in the present work in terms of a dependence of the sign of the charge transfer on velocity. By measuring the charge transferred to two ice targets of different size, an estimate has been made of the product of collision and separation probabilities of crystals interacting with a 5‐mm‐diameter target.
Automatic short‐range measurement of the cloud flash to ground flash ratio in thunderstorms
Authors: Mackerras D.
Published: February 2008

The principle of operation of an instrument designed for automatic long‐term measurement of the cloud flash to ground flash ratio in thunderstorms is described. The instrument uses a simple antenna to detect the electric field of lightning and is designed to have an effective range of about 14 km and a maximum range of about 20 km. Wave‐shape feature measurement is used to distinguish between the electric field wave‐shapes corresponding to cloud and ground flashes and is based principally on the presence of relatively large, well‐spaced, positive‐going changes (R changes) in the field changes caused by ground flashes. From observations with the instrument over two thunderstorm seasons from September 1982 to May 1984 in Brisbane, Australia, the cloud flash to ground flash ratio was 3.0. Large variations were observed in the ratio of cloud flashes to ground flashes for individual thunderstorm days. For days on which at least 100 total registrations occurred, the range was 0.9 to 24.7. Possible applications of an instrument of this type in atmospheric electricity studies are discussed.
Nitric oxide and nitrogen dioxide content of whole air samples obtained at altitudes from 12 to 30 km
Authors: Gallagher Charles C. , Forsberg Charles A. , Pieri Robert V. , Faucher Gerard A. , Calo Joseph M.
Published: February 2008

Whole air samples were obtained in the stratosphere using a liquid helium‐cooled cryosampler mounted on a balloon platform. Approximately 1 g mol of sample was obtained at each of three altitudes per balloon flight and was maintained at 4 K until desorption just prior to analysis. Samples were obtained at six altitudes ranging from 12 to 30 km and at five latitudes from 9° to 64°N. Nitric oxide and the sum of nitric oxide and nitrogen dioxide content of the samples were determined using two chemiluminescence analyzers. Results from flights conducted between 1977 and 1981 are correlated with atmospheric motions and other significant variables and evaluated in terms of both one‐ and two‐dimensional models of the stratosphere.
Seasonal amplitude increase in atmospheric CO2 concentration at Mauna Loa, Hawaii, 1959–1982
Authors: Bacastow R. B. , Keeling C. D. , Whorf T. P.
Published: February 2008

The concentration of atmospheric carbon dioxide at Mauna Loa Observatory exhibits a seasonal pattern that repeats with striking regularity from year to year. The amplitude of this seasonal signal, expressed either by peak‐to‐peak changes in concentration or as a series of harmonic terms, increased at an average rate of about 0.7% per year from 1958 to 1982. The estimated standard error in the linear coefficient of increase is 0.09%. Thus the increase appears to be highly significant statistically. A detailed examination of methods of calibration and of data analysis during this long record do not reveal any inconsistencies large enough to be responsible for the increase. Because the seasonal cycle of CO2 in the northern hemisphere is thought to be due principally to the metabolic activity of terrestrial vegetation, it is likely that at least part of the increase is a result of increasing plant activity.
A simple scheme for generating two layers of radiatively constrained effective clouds in GCM's
Authors: Gordon Charles T. , Stern William F. , Hovanec Russell D.
Published: February 2008

GCM‐dependent, radiatively constrained cloud amount fields could be preferrable to currently available observed fields for calculating radiative fluxes in GCM's used in long‐range weather forecast studies. Motivated by this premise, we formulate an economical effective cloud algorithm for GCM's called “SATCLD,” which utilizes compact, readily accessible analyses of observed satellite‐derived radiative flux data. We then examine the plausibility of preliminary effective cloud fields. Analysis of SATCLD and other cloud fields and associated radiative fluxes (diagnosed by our GCM's cloud radiation model from observed atmospheric temperature and water vapor data) also provides some insight into biases in our GCM's cloud radiation model and surface albedo field. “SATCLD” generates effective low and high cloud amounts at each GCM grid point by minimizing the sum of the squares of the local residual (i.e., model‐diagnosed minus observed) shortwave and longwave radiative fluxes. The preliminary SATCLD effective cloud amount fields seem plausible in many respects, based upon comparison with the satellite‐derived 3DNEPH and surface‐based SFCOBS analyses. In the tropics the SATCLD effective high cloud amount is rather well correlated with 3DNEPH, while systematic differences in low cloud amount are evident in July. Off the west coasts of Central and South America and southern Africa, the SATCLD effective low cloud resembles SFCOBS in July. At mid‐latitudes the strongest similarities are between SATCLD versus 3DNEPH high cloud amount in July and SATCLD versus SFCOBS low cloud amount over the oceans. The SATCLD analysis is ill conditioned in the polar night region. Limitations of the present scheme as well as deficiencies in our GCM's cloud‐radiation model and surface albedo fields and in the archived satellite data are discussed. Suggestions are made for reducing discrepancies between effective versus real clouds without sacrificing consistency between GCM‐diagnosed versus observed radiative fluxes.
Variations in stratospheric aerosol optical depth during northern warmings
Authors: Wang Pi‐Huan , McCormick M. P.
Published: February 2008

In this paper the properties of the stratospheric aerosol optical depth (above 50 mbar) have been studied by using aerosol extinction profiles (at 1 μm) derived from the Stratospheric Aerosol Measurement (SAM II) and Stratospheric Aerosol and Gas Experiment (SAGE) during warming periods in the northern hemisphere. It is shown that, during the disturbed periods in winter, low values of aerosol optical depth (<0.2×10−3) are found within the low‐pressure system(s) (at the 30‐mbar pressure surface), while high values are found outside. Similar characteristics are found to exist for the simultaneously observed SAGE O3 and NO2 columnar density distributions. Strong longitudinal gradients are shown with the low values within and wherever the vortex exists. This characteristic is maintained during and after the circumpolar vortex is disturbed, even after breakdown, indicating an isolation of the material within the vortex.
An intercomparison of nitric oxide measurement techniques
Authors: Hoell J. M. , Gregory G. L. , McDougal D. S. , Carroll M. A. , McFarland M. , Ridley B. A. , Davis D. D. , Bradshaw J. , Rodgers M. O. , Torres A. L.
Published: February 2008

Results from an intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted at Wallops Island, Virginia, in July 1983. Instruments intercompared included a laser‐induced fluorescence system and two chemiluminescence instruments. The intercomparisons were performed with ambient air at NO mixing ratios ranging from 10 to 60 pptv and NO‐enriched ambient air at mixing ratios from 20 to 170 pptv. All instruments sampled from a common manifold. The techniques exhibited a high degree of correlation among themselves and with changes in the NO mixing ratio. Agreement among the three techniques was placed at approximately ±30%. Within this level of agreement, no artifacts or species interferences were identified.
Photoabsorption cross section of CH3CN: Photodissociation rates by solar flux and interstellar radiation
Authors: Suto Masako , Lee L. C.
Published: February 2008

The photoabsorption cross section of CH3CN vapor was measured in the 106–180 nm region using synchrotron radiation as a light source. The cross section and the quantum yield for the production of CN (A, B → X) fluorescence were measured and were used to infer the photodissociation cross section of CH3CN. The cross sections were used to calculate the photodissociation rates of CH3CN by the solar flux and by the interstellar radiation. In both the stratosphere and the troposphere, the solar photo‐dissociation of CH3CN is negligible in comparison with chemical degradation.
Convection and entrainment across stratified interfaces
Authors: Breidenthal R. E. , Baker M. B.
Published: February 2008

We examine entrainment across stratified interfaces as a fluid mechanical process which depends on the local Reynolds, Schmidt, and Richardson numbers. We show that the observed dependence of entrainment velocity on the local Richardson number over a wide range of fluid dynamical parameters can be explained in terms of simple models of the turbulence at the interface. In the particular case of entrainment into nocturnal stratocumulus we derive an analytic, linear model of the radiatively driven convective turbulence in the layer. The model is applied to the observations of Caughey and Kitchen (1984), and it is shown that this model reproduces the gross features of the convection and the magnitude of the entrainment rate.
Anomalous light output from lightning dart leaders
Authors: Guo C. , Krider E. P.
Published: February 2008

About 5% of the multiple‐stroke cloud‐to‐ground lightning discharges recorded at the NASA Kennedy Space Center during the summer of 1981 contained dart leaders that produced an unusually large light output. An analysis of these cases indicates that the average peak light output per unit length in the leader may be comparable to or even exceed that of the return stroke that follows.
Seasonal estimates of global atmospheric sea‐salt distributions
Authors: Erickson D. J. , Merrill J. T. , Duce R. A.
Published: February 2008

Seasonal estimates of sea‐salt aerosol particle concentration distributions 15 m above the sea are presented on global contour maps. Measured data from a variety of sources relating atmospheric sea‐salt concentration to wind speed have been combined, yielding relationships of form C = exp (as + b), where C is sea‐salt concentration in micrograms per cubic meter and s is the horizontal wind speed in meters per second. These relationships, coupled with a Gaussian wind speed frequency distribution, allow us to calculate the atmospheric sea‐salt concentration accounting for the variance about mean wind speeds. We use monthly wind mean speed and variance information in 5° × 5° latitude/longitude squares over the world ocean to estimate the global sea‐salt aerosol particle mass distribution. The atmospheric sea‐salt concentrations in the northern hemisphere marine troposphere display a substantial seasonal dependence. The 3‐month seasonal average sea‐salt concentrations in this region differ by a factor of 2–3 between the boreal winter and summer, and the highest values are between 40 and 49 μg m−3. The seasonal variability of atmospheric sea‐salt concentrations in the high‐latitude southern hemisphere is much less than that in the northern hemisphere, varying by less than a factor of 2 between the austral winter and summer, and again the highest values are about 45 μg m−3. The equatorial areas have uniformly lower atmospheric sea‐salt concentrations than the high‐latitude regions. The monsoonal winds over the Indian Ocean produce sea‐salt concentrations in excess of 40 μg m−3 for the 3‐month boreal summer average.
Observational evidence of an inertial wind structure in the stratosphere
Authors: Sidi C. , Barat J.
Published: February 2008

A nearly inertial evolution of the relative velocities measured by differential sounding (Barat, 1982a) has been observed along a balloon flight in the 26–30 km altitude range. The vertical structure of the flow appears to be a stack of layers a few hundred meters wide undergoing independent, nearly inertial oscillations added to the mean flow, the transitions between adjacent layers being characterized by abrupt rotations of the horizontal wind. We show that the stability of such a structure, despite the very high wind shears encountered within transitions, is consistent with the very weak turbulent viscosity coefficient independently estimated. As a tentative interpretation of our observations we suggest that they are related to the dissipation of an internal gravity wave near a critical level.
Ions in the mesosphere and lower thermosphere: A two‐dimensional model
Authors: Brasseur G. , De Baets P.
Published: February 2008

The behavior of ions in the D and E regions is shown to exhibit large latitudinal and seasonal variations. These are due to the meridional transport of neutral species (NO, O, H2O), which interact with ion chemistry, to temperature variations, and to differences in the solar input and in high‐energy particle precipitation. This paper presents a two‐dimensional model of the ion composition in the D and E regions, which shows that the lower ionosphere is clearly dynamically controlled. The importance of the latitudinal and seasonal dependence of the nitric oxide concentration is pointed out. The model also shows that noticeable changes in the meridional distribution of ions should be attributed to the variability in the solar irradiance and in the strength of particle precipitation in relation to the 11‐year solar cycle.
Ozone perturbations by enhanced levels of CFCs, N2O, and CH4: A two‐dimensional diabatic circulation study including uncertainty estimates
Authors: Isaksen Ivar S. A. , Stordal Frode
Published: February 2008

Ozone perturbation estimates are performed in a two‐dimensional diabatic circulation model of the stratosphere and troposphere. Increased future release rates of N2O, CH4, and chlorofluorocarbons (CFCs) are considered in separate as well as in combined scenarios. As there are clear observational indications that the atmospheric concentrations of CH4 and N2O are increasing, in addition to the well‐established fact that CFCs are increasing, model studies of future ozone perturbations should focus on the combined effects of these compounds and their chemical interaction, which we find play a significant role. With our “best estimate” of combined scenarios of N2O, CH4, and CFCs (CFCl3 + CF2Cl2), leading to N2O increases of 40% and CH4 increases of 100% above their 1980 concentrations and CFC levels corresponding to steady state with 1980 releases as representative for the year 2050, the calculations show an average total global ozone depletion of 2.6%. The latitudinal gradients are particularly large. Total ozone depletion ranges from less than 2% at low latitudes to larger than 10% at high latitudes. The transport scheme adopted in our model (diabatic circulation with low eddy diffusivity in the stratosphere) is important for the obtained pattern in distribution of species and ozone depletion. Furthermore, increases in methane contribute strongly to the large variations we estimate for the ozone perturbation with height and latitude, making methane particularly important from a climatic point of view. Because of the strong coupling of the NOx and the Clx chemistry, future ozone perturbations by CFCs, including the nonlinear response in ozone depletion to chlorine increases, depend on levels of odd nitrogen in the stratosphere. The uncertainties connected with present stratospheric NOx measurements and also with key chemical reactions (for example, N2O + O(1D) → NO + NO) are shown to introduce large uncertainties in ozone perturbation calculations. Significant uncertainties may also be introduced by inadequate knowledge of the chlorine chemistry (for example, reactions converting Cl + ClO to HCl) in future high‐chlorine situations.
Kinetics and mechanisms of the gas phase reactions of the NO3 radical with a series of reduced sulfur compounds
Authors: Mac Leod Hélène , Aschmann Sara M. , Atkinson Roger , Tuazon Ernesto C. , Sweetman Janet A. , Winer Arthur M. , Pitts James N.
Published: February 2008

The gas phase reactions of the NO3 radical, a ubiquitous constituent of nighttime atmospheres with the reduced sulfur compounds COS, CS2, CH3SH, C2H5SH, and CH3SSCH3 have been investigated. Using a relative rate technique and long path length Fourier transform infrared (FT‐IR) absorption spectroscopy, rate constants for these reactions have been determined at 297 ± 2 K in one atmosphere of air. The resulting rate constants (in units of 10−13 cm3 molecule−1 s−1) are: COS, <0.0004; CS2, <0.008; CH3SH, 10 ± 3; C2H5SH, 12 ± 3; and CH3SSCH3, 0.42 ± 0.09. A number of products from these reactions were determined using FT‐IR absorption spectroscopy and combined gas chromatography/mass spectrometry. Atmospheric implications of these kinetic and product data are discussed.
Sea‐salt corrections and interpretation of constituent ratios in marine precipitation
Authors: Keene William C. , Pszenny Alexander A. P. , Galloway James N. , Hawley Mark E.
Published: February 2008

Differentiation of sea‐salt and non‐sea‐salt (or excess) components is essential for many studies of marine aerosol and precipitation chemistry. Uncertainties in such calculations arise from (1) uncertainties in the composition of seawater, (2) analytical uncertainties, (3) the amount of dry deposited sea salt in samples, (4) the validity of assuming a purely marine source for the sea‐salt reference species, and (5) the validity of assuming no fractionation during or after production of sea‐salt aerosols. We assessed these uncertainties, and, using the reduced major axis regression technique, evaluated these assumptions by analyzing the composition of precipitation at Amsterdam Island (38°S, 78°E) and at Bermuda (32°N, 65°W). Precipitation on Amsterdam Island contained significant excess concentrations of Na+ (2%) and Cl− (5%) relative to Mg2+. Indirect evidence indicates that these departures from seawater ratios are probably not due to the influence of terrestrial material. The excess Cl− was sufficient to account for approximately 20% of free acidity, suggesting that scavenging of vapor phase HCl may affect the acid‐base chemistry of precipitation at the site. Volume‐weighted excess SO42− based on Na+ and Mg2+ differed by 11%, a nonnegligible source of bias in estimating the wet deposition of non‐sea‐salt sulfur. Precipitation on Bermuda contained significant concentrations of locally derived alkali and alkaline earth metals. The influence of continental and non‐sea‐salt marine sources on concentrations of excess SO42− was also evident. These observations suggest that assumptions involved in sea‐salt corrections are not always satisfied and that it is therefore necessary to evaluate individual data sets, using objective criteria, to select the appropriate reference species.
Transport of ozone between boundary layer and cloud layer by cumulus clouds
Authors: Greenhut Gary K.
Published: February 2008

Turbulence data obtained from over 100 aircraft penetrations of isolated, nonprecipitating cumulus clouds are used to derive statistical parameters associated with the transport of ozone to and from the underlying boundary layer. The parameters are determined by the difference in ozone concentration between the cloud layer and boundary layer, ΔO3. The total cloud flux of ozone, defined as the transport across a horizontal plane within a cloud due to mean and turbulent cloud motions, is given by
, where
is the cloud vertical velocity averaged over an observing period. Cloud turbulence contributes about 30% to the total cloud flux.
Recombination of atomic oxygen near the mesopause: Interpretation of rocket data
Authors: Brasseur G. , Offermann D.
Published: February 2008

From the observations of atomic oxygen concentrations during the Energy Budget Campaign 1980, heating rates in the lower thermosphere at high latitude for late fall are derived and are found to be rather high. Useful information is also inferred for the vertical transport of mass and heat at these heights. The eddy diffusion coefficient which is derived from the data decreases with decreasing altitude below 100 km and reaches a minimum value of the order of 10 m2 s−1 near the mesopause. Such low value implies a low minimum concentration of nitric oxide (105–106 cm−3) near 80 km.
Rate of precipitation scavenging of nitrates on central Long Island
Authors: Sperber Kenneth R. , Hameed Sultan
Published: February 2008

By comparing deposition of nitrate in successive hours of precipitation samples taken over a six year period at Brookhaven National Laboratory (BNL), Long Island, New York, we have estimated scavenging coefficients in air, λ, for nitrate under a variety of meteorological and seasonal conditions. The square root transformation of the scavenging coefficients λ½ yields an approximately normal distribution; the mean value is 1.1 × 10−4 s−1, in general agreement with previous experimental and theoretical estimates. An interesting property of the distribution of the scavenging coefficients is that the ratio of the mean value of λ½ to its standard deviation varies little from 2.4 for various subsets of data; this property may limit the choice of stochastic models which describe the scavenging process. A trend analysis of the relationship between scavenging coefficients and rainfall rate indicates that the scavenging coefficient of nitrate does not increase for rainfall rates ≤3.2 mm h−1. The indicated increase at greater rainfall rates is qualitatively similar to model predictions but is based upon a small number of data points. The mean scavenging coefficient for winter rain events is greater than for snow.
Stratospheric aerosols and the Indian monsoon
Authors: Handler Paul
Published: February 2008

This paper reports on a research study of the association between stratospheric aerosols and Indian monsoon precipitation. It was found that low‐latitude aerosols precede below average precipitation and high‐latitude aerosols precede above average precipitation. A chi‐squared analysis shows that the association is above the 99% level of significance. The second part of the research concerns the transformation of low‐latitude aerosols into high‐latitude aerosols as they move poleward in the second year of their existence. The model predicts that below average monsoon precipitation of the first year after a low‐latitude eruption would be followed by above average monsoon precipitation in the second year. The findings support the prediction. Table 7 shows that below average monsoon years are twice as likely to be followed by above average monsoon years as by below average monsoon years. Because aerosol research suffers from inadequate reporting of the events (see appendices A, B, and C), the third section of this research study uses El Niño events as a proxy for the presence of low‐latitude stratospheric aerosols. Previous research of Handler (1984, 1986) and Parker (1986) has shown that there is a high level of statistical association (>98%) between the presence of low‐latitude stratospheric aerosols and El Niño events. The 22 moderate and strong El Niño events (Quinn et al., 1978) are used as a proxy for the presence of low‐latitude aerosols. Six of the 22 events are not useful for the analysis because of the presence of interfering aerosols. Of the 16 possible El Niño events with no interfering aerosols present, 13 show the proper sequence of below average and then above average monsoon precipitation. Since recent aerosols data are generally more complete, a separate analysis of the 1942–1984 period is presented. In that 43 year period, the Indian monsoon fits the stratospheric forcing model very closely. Low‐latitude aerosols are associated with below average monsoon precipitation and high‐latitude aerosols are associated with above average monsoon precipitation. Six years are indeterminate because of the interfering effects of high‐ and low‐latitude aerosols. The data are consistent with the global climate models of Kutzbach and Guetter (1986). The forcing of a low‐latitude aerosol is assumed equivalent to a decrease in solar radiation in that both reduce the equator‐to‐pole temperature gradient. The Kutzbach and Guetter study has shown that a small change of solar radiation can produce a large change in monsoon precipitation. Finally, the research suggests that the long term, secular behavior of Indian monsoon precipitation can be related to the frequency of low‐latitude volcanic eruptions. During the early part of the 20th century, low‐latitude eruptions were frequent and the average monsoon precipitation was low. During the period 1942–1962 the frequency of low‐latitude eruptions was low and the average monsoon precipitation was high.
Stratospheric determination of O2 cross sections and photodissociation rate coefficients: 191–215 nm
Authors: Anderson G. P. , Hall L. A.
Published: February 2008

Measurements of the transmittance and deposition of solar ultraviolet energy into the middle stratosphere have been made using a balloon‐borne, solar‐pointing spectrometer with both 0.012‐ and 0.10‐nm resolution. The full spectral range (185–311 nm) includes much of the molecular oxygen Schumann‐Runge [B‐X] absorption and the underlying Herzberg [A‐X] continuum, allowing the derivation of atmospherically appropriate effective absorption cross sections for these bands. In addition to verifying the recent laboratory measurements of the Herzberg continuum cross section, an analysis of the O2 transmittance suggests that window regions within the Schumann‐Runge bands (λ≤200 nm) may also allow deeper penetration of solar energy than predicted by current photochemical modeling schemes.
Vertical distributions of molecular hydrogen off the Eastern and Gulf Coasts of the United States
Authors: Cofer Wesley R. , Harriss Robert C. , Levine Joel s. , Edahl Robert A.
Published: February 2008

The vertical distributions of molecular hydrogen (H2) and carbon monoxide (CO) were determined during spiraling maneuvers from aircraft off the eastern coast of the United States and over the Gulf of Mexico. H2 was always at its lowest levels in the boundary layer, averaging about 500 parts per billion by volume (ppbv). H2 mixing ratios determined in the free troposphere were typically higher (600–700 ppbv) and often suggested a small progressive increase with altitude. Several large free‐tropospheric H2 plumes (mixing ratios as high as 1–2 parts per million by volume) were implied by the data. These H2 plumes were not always accompanied by corresponding increases in CO mixing ratios. This result is most difficult to explain when it is noted that the primary atmospheric sources for molecular H2 are considered to be combustion and photochemistry, both of which should be strong CO sources also.
Variability of the solar “constant” on time scales of minutes to years
Authors: Fröhlich C.
Published: February 2008

Solar irradiance variability has been studied from measurements of total solar irradiance at 1 AU, the solar “constant” S0, since the late 1960s. Power spectra of time series from satellite and balloon experiments show that the irradiance varies, with periods of minutes to several hours and with amplitudes of parts per million to a few hundredths of a percent. Part of this variance is due to coherent pressure and, possibly, gravity oscillations as spherical harmonics of the sun. On time scales of days to months most of the variance is a modulation of the solar irradiance by photospheric features related to solar activity and reaches amplitudes of a few tenths of a percent. Because of its origin the variance in this range changes by up to 1 order of magnitude with the solar cycle, as shown by comparison of the power spectra from 1980 and 1984/1985, respectively. The first evidence of a persistent long‐term change comes from satellite data, which show a downward trend of S0 since 1980 by about 0.02% per year. The S0 determinations between 1967 and 1970, compared with the modern ones show a statistically significant increase during that period of similar magnitude. Both trends together could be part of a 22‐year cycle related to the magnetic cycle of the sun.
Measurements of nitric oxide in the boundary layer and free troposphere over the Pacific Ocean
Authors: Ridley B. A. , Carroll M. A. , Gregory G. L.
Published: February 2008

Measurements of NO and O3 are presented from 13 aircraft flights made over the Pacific Ocean in the autumn of 1983 during one phase of the NASA Global Tropospheric Experiment (GTE). All of the flights were made between 15° and 42°N and from the coast of California to west of the Hawaiian Islands. Within the upper marine boundary layer the median daytime mixing ratio of NO was near 1 part per trillion by volume (pptv). As well, values of NO less than 10 pptv were often observed up to altitudes near 6 km. Thus for the location and season of the measurements, a net photochemical destruction of O3 would be anticipated for the boundary layer region and to altitudes of 2–3 km. At higher altitudes of 7–11 km in the free troposphere, larger mixing ratios and greater variability were usually observed for NO. Both features are consistent with observed examples of injection of NO and O3 from the lower stratosphere and with the injection of NO from towering, electrically active, cumulonimbus clouds.
Three‐dimensional analysis of potential vorticity associated with tropopause folds and observed variations of ozone and carbon monoxide
Authors: Danielsen Edwin F. , Hipskind R. Stephen , Gaines Steven E. , Sachse Glen W. , Gregory Gerald L. , Hill G. F.
Published: February 2008

A temporal comparison of potential vorticity, ozone mixing ratio, and carbon monoxide mixing ratio along the flight path of the CV‐990 on April 20, 1984, is presented and discussed. The flight path was designed to obtain in situ measurements of O3 and CO in the lower stratosphere of a rapidly developing cyclone and above, within, and below an associated folded tropopause structure extruded into the troposphere. The potential vorticity is computed from vertical cross‐sectional analyses of potential temperature and wind speed along the flight path. These analyses, in turn, were derived from three‐dimensional analyses, including vertical cross sections, constant pressure, and constant potential temperature surfaces, iteratively adjusted for consistency. Only radiosonde observations were used in all of the analyses to provide an objective test of the subjective analysis methods and of the assumptions that potential vorticity, like ozone, is a quasi‐conservative stratospheric tracer and that both quantities would be negatively correlated with carbon monoxide, a tropospheric tracer. The resulting correlations are remarkably high and the data is of sufficient quality to permit quantitative evaluations of the deformational growth of the tropopause fold, including the effective eddy diffusion coefficient, the compensating entrainment velocity, and the mass of air and ozone entrained.
Albedos of homogeneous semi‐infinite canopies: Comparison of two‐stream analytic and numerical solutions
Authors: Dickinson Robert E. , Sellers Piers J. , Kimes Daniel S.
Published: February 2008

The albedo of plant canopies is treated as a problem in radiative transfer. We compare albedos calculated from an iterative multistream numerical model with those calculated with an analytic two‐stream solution. With the assumption of a randomly homogeneous distribution of leaf positions and orientations and isotropic scattering by individual leaves the single‐scattering albedo of the canopy can be found analytically. This single‐scattering solution is incorporated into the two‐stream solution and used to benchmark the multistream numerical model in the single‐scattering limit. Relative errors so established in the multistream model are O(0.3%) or less. The two‐stream model is also found to be remarkably accurate, with the error in multiply scattered radiation O(5%) or less, corresponding to absolute errors in visible albedo of <0.001 and near‐infrared albedo of ≤0.01. Thus the two‐stream model should be adequate for many purposes, such as climate modeling, provided the assumptions of homogeneous canopy and isotropic scattering are not too unrealistic.
Lightning location relative to storm structure in a supercell storm and a multicell storm
Authors: Ray Peter S. , Macgorman Donald R. , Rust W. David , Taylor William L. , Rasmussen Lisa Walters
Published: February 2008

Relationships between lightning location and storm structure are examined for one radar volume scan in each of two mature, severe storms. One of these storms had characteristics of a supercell storm, and the other was a multicell storm. Data were analyzed from dual‐Doppler radar and dual‐VHF lightning‐mapping systems. The distributions of VHF impulse sources were compared with radar reflectivity, vertical air velocity, and their respective gradients. In the supercell storm, lightning tended to occur along streamlines above and downshear of the updraft and reflectivity cores; VHF impulse sources were most concentrated in reflectivities between 30 and 40 dBZ and were distributed uniformly with respect to updraft speed. In the multicell storm, on the other hand, lightning tended to coincide with the vertical reflectivity and updraft core and with the diverging streamlines near the top of the storm. The results suggest to us that the location of lightning in these severe storms was most directly associated with the wind field structure relative to updraft and reflectivity cores. Since the magnitude and vertical shear of the environmental wind are fundamental in determining the reflectivity and wind field structure of a storm, we suggest that these environmental parameters are also fundamental in determining lightning location.
Distribution of total ozone and stratospheric ozone in the tropics: Implications for the distribution of tropospheric ozone
Authors: Fishman Jack , Larsen Jack C.
Published: February 2008

Climatologies of total columnar ozone and integrated stratospheric ozone amounts at low latitudes (15°N to 15°S), derived from satellite observations, are presented. A significant longitudinal variability in total ozone is present, with highest values generally located between 60°W and 60°E. The integrated stratospheric component of total ozone, on the other hand, does not exhibit a longitudinal preference for high values. Therefore we hypothesize that the climatological longitudinal distribution of total ozone reflects the variability of the abundance of tropospheric ozone at low latitudes. Furthermore, we speculate that in situ photochemical production of ozone resulting from biomass burning may be responsible for the observed enhancement of total ozone at these longitudes.
The use of atmospheric measurements to constrain model predictions of ozone change from chlorine perturbations
Authors: Douglass Anne R. , Stolarski Richard S.
Published: February 2008

Atmospheric photochemistry models have been used to predict the sensitivity of the ozone layer to various perturbations. These same models also predict concentrations of chemical species in the present day atmosphere which can be compared to observations. Model results for both present day values and sensitivity to perturbation depend upon input data for reaction rates, photodissociation rates, and boundary conditions. This paper develops a method of combining the results of a Monte Carlo uncertainty analysis with the existing set of present atmosphere species measurements. The method is used to examine the range of values for the sensitivity of ozone to chlorine perturbations that is possible within the currently accepted uncertainty ranges for input data. It is found that model runs which predict ozone column losses much greater than 10% as a result of present fluorocarbon fluxes produce concentrations and column amounts in the present atmosphere which are inconsistent with the measurements for ClO, HCl, NO, NO2, and HNO3.
Sampling errors in satellite estimates of tropical rain
Authors: McConnell Alan , North Gerald R.
Published: February 2008

The GATE rainfall data set is used in a statistical study to estimate the sampling errors that might be expected for the type of snapshot sampling that a low earth‐orbiting satellite makes. For averages over the entire 400‐km square and for the duration of several weeks we find strong evidence that sampling errors less than 10% can be expected in contributions from each of four rain rate categories which individually account for about one quarter of the total rain.
Estimation of surface moisture availability from remote temperature measurements
Authors: Flores Alberto L. , Carlson Toby N.
Published: February 2008

Analyses of moisture availability, determined from GOES infrared surface temperature measurements and a boundary layer model, and antecedent precipitation are presented for data taken over Texas and Argentina. Correlations between antecedent precipitation and moisture availability are high (∼0.8) where the spatial variation in moisture availability (or ground temperature) is much larger than an inherent uncertainty in the method, which we judge to be about ±0.2 for the moisture availability parameter. In regions where there are large gradients of precipitation the infrared method can provide useful information on variations in soil moisture availability and, by implication, in precipitation.
Rectangular pulses point process models for rainfall: Analysis of empirical data
Authors: Rodríguez‐Iturbe I. , de Power B. Febres , Valdés J. B.
Published: February 2008

A detailed analysis of some rainfall data from Denver, Colorado, is carried out at different levels of aggregation which range from 1 to 24 hours. Two classes of models are then fitted to the data; In the first class of models, storm events arise in a Poisson process, each such event being associated with a period of rainfall of random duration and constant but random intensity. Total rainfall intensity is formed by adding the contributions from all storm events. In the second class of models, storms arise in a Poisson process, each storm giving rise to a cluster of rain cells and each cell having a random duration and constant but random intensity. The estimation of the model parameters is performed through the first‐ and second‐order moments of the cumulative rainfall process, at different levels of aggregation. It is found that the first class of models gives a poor fit at levels of aggregation different from the one at which the model parameters are estimated. Cluster‐based models are able to take account of the cumulative rainfall characteristics over a range of time scales from 1 to 24 hours without changing the model parameters. These models also perform well in regard to the extreme values of rainfall for different periods of aggregation and the time concentration of total rainfall.
Survey of ozone concentrations in an equatorial region during the rainy season
Authors: Cros B. , Delmas R. , Clairac B. , Loemba‐Ndembi J. , Fontan J.
Published: February 2008

Ground level ozone concentrations were measured in Brazzaville (4°20′S, 15°20′E), Congo, from November 1983 to October 1984 and during shorter periods in other typical locations. The daily variations are of the same type as those observed at other weakly polluted continental sites. In the wet season the average concentration in the atmospheric boundary layer (30 ppb) is similar to that found over the Amazon tropical forest but higher than that found over the oceans. An ozone episode with maxima of about 70 ppb was observed; this episode may have had a photochemical origin.
Infrared spectroscopic measurements of halogenated source gases in the stratosphere with the ATMOS instrument
Authors: Zander R. , Rinsland C. P. , Farmer C. B. , Norton R. H.
Published: February 2008

The volume mixing ratios of the six most important halogenated source species (CH3Cl, CF2Cl2, CFCl3, CHF2Cl, CCl4, and CF4) have been retrieved over the 10‐ to 30‐km altitude range from the analysis of 0.01 cm−1 resolution infrared solar occultation spectra recorded near 30°N and 47°S latitudes with the ATMOS (Atmospheric Trace Molecule Spectroscopy) instrument, operating from on board Spacelab 3 (April–May 1985). The results reported here, although in satisfactory agreement with recent in situ values obtained from air sampling techniques, are limited in accuracy by the limited absorption representative of most of the species and by uncertainties in the Spectroscopic parameters currently available for these gases. They demonstrate, however, the powerfulness of the IR remote sensing approach for evaluating on a global scale the total chlorine budget of the atmosphere, and they provide an independent set of simultaneous data acquired for the important source and reservoir halogenated molecular species in the upper atmosphere.