bluuebunny/crossref_metadata_2025 huggingface dataset:
The tropical tropopause and the El Niño of 1982–1983
Authors: Gage K. S. , Reid G. C.
Published: February 2008

An earlier study of the behavior of the tropical tropopause during 1982 is extended through 1984. The earlier study focused on the influence of the El Chichón volcanic eruption, but it also considered the influence of the 1982–1983 El Niño event during its onset phase in the latter half of 1982. Here we present anomalies of tropopause height, tropopause potential temperature, and lower stratospheric potential temperature through 1984. These anomalies clearly show a much warmer than normal tropopause potential temperature over the western tropical Pacific, associated with El Niño. The abnormally warm tropopause potential temperature, which was evident in late 1982, reaches a peak in early 1983 and continues abnormally warm until about October 1983. During this period the tropopause is also abnormally high, but the lower stratospheric potential temperature is near normal.
OH measurement near the Intertropical Convergence Zone in the Pacific
Authors: Davis L. I. , James John V. , Wang Charles C. , Guo Chuan , Morris Peter T. , Fishman Jack
Published: February 2008

Airborne measurements of OH were made near the Intertropical Convergence Zone in the Pacific, and the averaged results for each data run were compared with those calculated from a photochemical model. The measured OH concentrations were found to vary along the flight path. Possible causes for the observed variations are discussed.
Statistical analysis of total ozone and stratospheric Umkehr data for trends and solar cycle relationship
Authors: Reinsel Gregory C. , Tiao George C. , Miller Alvin J. , Wuebbles Donald J. , Connell Peter S. , Mateer Carl L. , Deluisi John J.
Published: February 2008

We report on trend analysis of Dobson total ozone data through 1984 and stratospheric Umkehr profile ozone data through 1981, including an examination of the relationship between ozone and long‐term solar cycle activity using the 10.7‐cm solar flux data. The estimate of the overall global trend in total ozone during the period 1970–1984, with associated 95% confidence (two standard error) limits, is (−0.26±0.92)% per decade, which indicates no significant overall trend. Based on use of the 10.7‐cm flux measurements, an overall estimate of the total ozone‐solar flux relationship is (1.18±0.66)% change in total ozone from solar cycle minimum to maximum, which indicates a statistically significant positive relationship. Trend analysis of Umkehr data through 1981 yields statistically significant negative trends on the order of (−0.30±0.17)% per year in layers 7 and 8 (∼34–43 km), with Mauna Loa transmission data being used to account for volcanic aerosol effects on the Umkehr data. The analysis also indicates significant relationships between Umkehr data and solar flux in layers 6 and 7 (∼29–38 km) of (2.57±1.25)% and (3.40±2.16)% change, respectively, from solar cycle minimum to maximum, with no significant relationship detected in the higher layers 8 and 9 where the estimates are more variable. Comparison of these empirical estimates with theoretical model calculations is discussed. Trend analysis of Umkehr data using data through 1984 is not reported in this paper because of the severe impact of volcanic aerosols from El Chichon on the Umkehr measurements during 1982–1984, although further research on methods for adjustment of Umkehr data for aerosol effects during this period is continuing.
A study of global ozone transport and the role of planetary waves using satellite data
Authors: Wu Mao‐Fou , Geller Marvin A. , Olson Jerry G. , Larson Edmund M.
Published: February 2008

Global ozone fluxes and flux divergences within the region between 30 and 0.4 mbar are computed for the period from December 1, 1978, to November 30, 1979, using Nimbus 7 solar backscattered ultraviolet ozone profiles and meteorological data derived from National Oceanic and Atmospheric Administration satellites. The annual cycle of ozone transports in the northern and southern hemispheres is presented and discussed. It is found that planetary scale waves are responsible for initiating the high‐latitude ozone buildup in winter. The time of occurrence and the position of the annual maximum ozone are found to be closely related to the planetary wave activity in both hemispheres.
On the effects of ice crystal porosity on the radiative characteristics of cirrus clouds
Authors: Stephens Graeme L.
Published: February 2008

This paper attempts to illustrate how the porous nature of ice crystals might influence the relationships between the radiative properties of ice clouds and the ice water path. Solutions of the electromagnetic wave equation were obtained for a simplified, hollow, infinitely long circular cylinder. On the basis of these solutions it was implied that the effects of ice crystal porosity on the particle‐scattering parameters can be expected to be small and that the major influence of porosity on radiation‐ice water path (IWP) relationships will be primarily on the definition of IWP. It is suggested that this effect probably accounts for the existing discrepancy noted in this paper between the theoretical and observed ε‐IWP relationships.
Cloud fields retrieved from analysis of HIRS2/MSU sounding data
Authors: Susskind J. , Reuter D. , Chahine M. T.
Published: February 2008

The methods used to determine effective cloud fraction (cloud fraction times cloud emissivity at 11–14 μm) and cloud top pressure from analysis of HIRS2/MSU sounding data are described. Identical procedures are used day and night so as to allow for meaningful day‐night difference fields. Results are shown for June 1979. The monthly mean effective cloud fraction is 43.4%, resulting from a 45.2% value at 0300 LT and 41.6% at 1500 LT. The retrieved single‐day cloud field for June 11 shows good agreement with high spatial resolution visible and infrared imagery.
Cloud cover over the equatorial eastern Pacific derived from July 1983 International Satellite Cloud Climatology Project data using a hybrid bispectral threshold method
Authors: Minnis Patrick , Harrison Edwin F. , Gibson Gary G.
Published: February 2008

A revised hybrid bispectral threshold method is developed to improve retrievals of clear‐sky and cloud‐top temperatures, low‐level cloud amounts, and thin cirrus clouds. These changes include the setting of constraints on the cloud albedo and the temperatures which may be included in the calculations of clear‐sky temperature and cloud amount. When any of the limits are exceeded, an alternative method is used for the determination of cloud amount from the two‐dimensional visible‐infrared histogram. The alternate method used depends on the type of constraint violated by the results from the standard cloud amount calculation. Even though it appears that the overall average cloud amount derived with the revised method is not much different than that which would have been derived from the original technique, the new methodology produced substantial changes in about one third of the cloud amount retrievals. Low cloud retrievals were affected most often by the new constraints. Thin, high clouds were detected in many instances when they would have been missed with the original methodology. The revised method was used to analyze a 15‐day set of 3‐hourly, 32‐km resolution visible and infrared data taken with the GOES‐West satellite over the tropical eastern Pacific for the International Satellite Cloud Climatology Project (ISCCP). Four different types of cloud regimes were prevalent over the 2.5°×2.5° regions within the study area: trade cumulus characterized by low albedo (∼29%), low altitude, and low cloud amount (<40%); low‐altitude stratocumulus, with mean albedos of about 33% and total cloud amount >40%; Intertropical Convergence Zone (ITCZ) cloudiness characterized by a predominance of middle‐ and high‐altitude clouds, with cloud albedos >35% and cloud amounts >50%; and tropical storms, with a predominance of high clouds, high albedos, and mean cloud amounts as great as 74%. Diurnally averaged albedos of 29%, 34%, and 44% were found over low, middle, and high clouds, respectively. Cloud amounts and albedos are similar to those derived from other data sets. Total and low cloud amounts in areas with trade cumulus and stratocumulus fields were usually greatest in the early morning and at a minimum in the midafternoon. A harmonic analysis of mean 3‐hourly cloudiness over the trade and stratocumulus regions revealed a very strong diurnal component over both cloud types. A significant semidiurnal component was found over the trade cumulus regions. Its phase corresponds to the semidiurnal tide. The semidiurnal component was much weaker over the stratocumulus regions. Over the ITCZ and the areas where the tropical storms passed, high cloud amounts generally peaked during the midafternoon. The diurnal variations of midlevel clouds were marked by early morning maxima and midday minima.
Measurements of surface energy budgets in the Rocky Mountains of Colorado
Authors: Sheaffer John D. , Reiter Elmar R.
Published: February 2008

The surface energy balance of a mountain valley and a mountain peak were continuously monitored for periods of 126 and 34 days, respectively. The data yielded temporally resolved, high‐quality measurements of the radiative, soil, and total atmospheric turbulent heat fluxes. Comparative data for the two sites reveal the effects of terrain setting and surface cover in modulating the heat balance. A procedure is suggested for accommodating local advective affects due to variable terrain and surface cover to allow partitioning of the total turbulent flux into values for sensible and latent heat. This procedure relies on a stability‐dependent coefficient of turbulent transfer which is locally calibrated to systematically minimize advection‐related errors. Scaling functions for the transfer coefficient are based on the effective blackbody temperature of the surface. Consequently, the procedure offers an opportunity for developing reliable bulk representations of heat transfer at the surface for use with remote sensing data and with models of the soil and surface cover in complex terrain.
In situ measurement of atomic hydrogen in the upper mesosphere
Authors: Sharp W. E. , Kita D.
Published: February 2008

In situ measurements of [H] between 73 and 93 km are reported for conditions of winter solstice, magnetic quiet, and a solar depression angle of 12°. The data were obtained by a rocket‐borne instrument using the resonance fluorescence technique. A discharge source emitting photons at 1216 Å was an integral part of the instrument. The instrument was radially deployed 80 cm by a boom from the front of the payload in order to avoid the shock created by the gas flow over the front of the payload. An attitude control system oriented the payload so that the gas flow was nearly perpendicular to the plane containing the incident and scattered photons, thus minimizing any correction for Doppler shift. The resonance radiation detector viewed a black backstop in order to minimize background radiation from the hydrogen geocorona; however, the background was not entirely eliminated. The signal‐to‐noise ratio was improved by summing the data in 1.8‐s bins. The observed hydrogen concentration maximized at 85 km at 1.5±1.1×108 atoms cm−3.
Cloud‐to‐ground lightning flash characteristics from June 1984 through May 1985
Authors: Orville Richard E. , Weisman Robert A. , Pyle Richard B. , Henderson Ronald W. , Orville Richard E.
Published: February 2008

A magnetic direction‐finding network for the detection of lightning cloud‐to‐ground strikes has been installed along the east coast of the United States. Time, location, flash polarity, stroke count, and peak signal amplitude are recorded in real time. Results are presented from nine direction finders for 1 year, June 1, 1984, through May 31, 1985. The data were recorded from Maine to North Carolina and as far west as Ohio; analyses were restricted to flashes within 300 km of a direction finder. Measurements of peak signal strength have been obtained from 720,284 first return strokes lowering negative charge. These return strokes are assumed to have a median peak current of 30 kA. It is also assumed that the return stroke speed is constant. The resulting distribution indicates that few negative strokes have peak currents exceeding 100 kA. Measurements have also been obtained of peak signal strength from 17,694 first return strokes lowering positive charge. These strokes have a median peak current of 45 kA, with some peak currents reaching 300–400 kA. The same assumptions are made for positive strokes as for negative strokes. The median peak signal strength, and we believe the peak current, doubles from summer to winter for both negative and positive first return strokes. The polarity of ground flashes is observed to be less than 5% positive throughout the summer and early fall, then increases to over 50% during the winter, and returns to less than 10% in early spring. The percent of positive flashes with one stroke is observed to be approximately 90% throughout the year. The percent of negative flashes with one stroke is observed to increase from 40% in the summer to approximately 80% in January, returning to less than 50% in the spring.
Vertical constituent transport in the mesosphere
Authors: Strobel Darrell F. , Summers Michael E. , Bevilacqua Richard M. , DeLand Matthew T. , Allen Mark
Published: February 2008

Ground‐based microwave spectroscopy measurements of mesospheric CO and H2O vertical mixing ratio profiles are used to infer vertical mixing rates in the upper mesosphere. The CO and H2O data consistently imply vertical eddy diffusion coefficients in the 70‐ to 85‐km region of ≲(1–2) × 105 cm2 s−1 during spring through summer at mid‐latitudes. Although chemical acceleration of vertical transport is substantial for O and O3 below the mesopause, the divergences of their associated fluxes are modest, with at most a factor of 2 effect on the concentrations of O and O3 for measured variability in gravity wave activity. Comparison of Solar Mesosphere Explorer (SME) O3 data with model results reinforces the conclusions of slow vertical mixing in the upper mesosphere as a consequence of the reduced HOx catalytic loss of odd oxygen. The changes in chemical rate constants recommended by Rusch and Eckman (1985), in conjunction with slow vertical mixing, yield good agreement with SME O3 data. The slow vertical mixing deduced in this study is consistent with upper limits obtained from studies of the mesospheric heat budget and could be construed as evidence for an advectively controlled mesosphere. A comparison of the vertical eddy diffusion coefficients for momentum stresses, constituent transport, and heat transport suggests that the eddy Prandtl number must be of order 10.
Correlated behavior of the aerosol and ozone contents of the stratosphere after the El Chichon eruption
Authors: Adriani Alberto , Fiocco Giorgio , Gobbi Gian Paolo , Congeduti Fernando
Published: February 2008

Stratospheric aerosol contents measured by lidar in Frascati and ozone contents measured by Dobson spectrophotometers and by ozonesondes at geographically close stations in the period following the El Chichon eruption of 1982 have been compared. The total contents as well as the vertical profiles of the two quantities show large, negatively correlated fluctuations. Estimates of the change in the ozone photodissociation frequency due to enhanced scattering by the volcanic aerosol as well as changes in the reaction rates due to heating indicate that radiative processes should be considered amongst the causes of the ozone anomaly.
Chemistry and physics of a winter stratus cloud layer: A case study
Authors: Daum P. H. , Kelly T. J. , Strapp J. W. , Leaitch W. R. , Joe P. , Schemenauer R. S. , Isaac G. A. , Anlauf K. G. , Wiebe H. A.
Published: February 2008

The chemical and physical properties of a supercooled stratus cloud layer and surrounding clear air covering southern Ontario on February 20, 1984, were studied with the objectives of identifying the processes responsible for the cloud water chemical composition. The cloud layer, which extended from circa 650 to 1050 m mean sea level, was bounded by a strong temperature inversion just at cloud top. The air below this inversion was well mixed vertically, as indicated by the near independence of concentrations of various trace gas species with altitude and by conservation of number concentration of particles from the surface to cloud top, with below‐cloud aerosol number concentrations (0.2 < d < 3 μm) approximately equal to the sum of the interstitial aerosol and cloud droplet (2 < d < 30 μm) number concentrations. Fractional incorporation of aerosol sulfate into cloud water, determined by comparison of interstitial and cloud water sulfate concentrations, was in the range of 85–90%, similar to the result inferred from comparison of interstitial aerosol and cloud droplet number concentrations. Gas phase equivalent concentrations of cloud water species were the same (within experimental error) as the concentrations of aerosol and soluble trace gas species in the below‐cloud air. These results suggest that the dominant processes determining cloud water composition in this cloud layer were nucleation scavenging of sulfate aerosol and scavenging of gaseous HNO3, with no significant contribution from reactive scavenging processes.
CF4 and C2F6 in the atmosphere
Authors: Fabian P. , Borchers R. , Krüger B. C. , Lal S.
Published: February 2008

Mid‐latitude vertical profiles of CF4 and C2F6 are presented. They show CF4 decreasing from about 67 parts per trillion by volume (pptv) in the troposphere to 60 pptv at 35 km, while C2F6 falls off more rapidly, from 2 to 1.3 pptv. Assuming that the electrolytic aluminum reduction process is the dominating anthropogenic source, past emission scenarios for both fluorocarbons were determined. The comparison of observed profiles with those computed with a time‐dependent model shows that 100% of C2F6 but only 35% of CF4 present in the atmosphere is from anthropogenic sources. The present global emission rates are 28×103 t/yr for CF4 and 3.2×103 t/yr for C2F6. The global abundances of both halocarbons are expected to grow by 2.8%, or 1.9 pptv/yr, and 6.4%, or 0.13 pptv/yr, respectively.
Analysis of the effects of zonal averaging on reaction rate calculations in two‐dimensional atmospheric models
Authors: Kaye Jack A.
Published: February 2008

The usual assumption by which chemical reaction rates are calculated in two‐dimensional atmospheric models is by using a product of zonal means of rate coefficients and constituent concentrations rather than the rigorous zonal mean of the corresponding products. This assumption has been tested for the reactions O + NO2 → NO+ O2 and NO + O3 → NO2 + O2 using mapped limb infrared monitor of the stratosphere data from the Nimbus 7 satellite and found to be quite satisfactory for winter 1979 at 60°N in the upper stratosphere. Relative differences between the two‐dimensional averaged rate and the more rigorous rate, calculated from the full, longitudinally varying temperatures and mixing ratios, were small (usually below 5%) and exceeded 15% only during times of strong dynamical activity. At those times or locations where stratospheric circulation is primarily zonal, the two averages agreed to within a few percent.
A two‐stream model of the vertical transport of trace species in the convective boundary layer
Authors: Chatfield Robert B. , Brost Richard A.
Published: February 2008

A conceptually simple two‐stream model (TSM) of the convective planetary boundary layer (PBL) provides a surprisingly realistic description of basic boundary layer transport features. The model is empirically fitted to a variety of important passive tracer problems. This model, unlike previous eddy diffusion models of vertical transport, is constructed to have a basic similarity to the underlying physics of transport. One parameterization can describe sources at the top or the bottom boundary or at all points within the domain and thereby may be used in simulations describing chemical or radiative forcings throughout the PBL. The TSM also allows estimates of concentration variations due to sources, chemical processes, and temporal variation in the boundary conditions. However, it is intended for use only in problems in which the relatively exact description of the PBL provided by a large‐eddy model is not practical. The model is likely to be most useful in parameterizing vertical turbulent transfer in the convective boundary layer when the chemical time scale is comparable to or greater than the convective time scale zi/w*, around 15 min. We present one model set of parameters which appears to perform well in a variety of situations. A methodology is available which may be applied to fit the model to a variety of PBL transport situations as accurate tracer measurements or three‐dimensional model data become available.
A global atmospheric selenium budget
Authors: Mosher Byard W. , Duce Robert A.
Published: February 2008

An examination of the major anthropogenic and natural sources of atmospheric selenium indicates that approximately 13–19×109 g Se are cycled through the troposphere annually. Perhaps 60% of this flux is natural in origin, and both man‐made and biological emissions appear to be predominantly gaseous in nature. Emissions from the marine biosphere and the combustion of coal account for 50–65% of the total atmospheric selenium emissions, and the natural marine flux appears to be roughly twice as large as that due to coal combustion.
Irregular and diurnal variability in asynoptic measurements of stratospheric trace species
Authors: Salby Murry L.
Published: February 2008

Two classes of variability in stratospheric trace species: (1) dynamically introduced tracer irregularities and (2) diurnal variations in photochemically active species, are investigated with regard to asynoptic satellite measurements. The fidelity with which the continuous synoptic behavior may be derived from discrete asynoptic measurements is explored. For both classes of variability several diagnostics of the continuous behavior (e.g., space‐time spectra, synoptic maps, time‐mean fields) are constructed from asynoptic measurements and compared with the true variability. Irregular tracer behavior of dynamical origin, as may follow large amplitude wave events or stratospheric warmings, is treated in a stochastic framework. An advected space‐time process is constructed according to prescribed correlation scales, reflecting the spatial extent and lifetime of tracer anomalies which are introduced randomly into the field and advected about the globe in a specified zonal flow. In the case of diurnal variations, e.g., in photochemically active gases in the upper stratosphere and mesosphere, a solar waveform is prescribed to propagate through a latitudinal envelope. The structure of this solar signature is truncated to the sunlit side of the globe to mimic the response of photochemically active species. For both classes of variability (under plausible scales and advection speeds in the case of random tracer fluctuations) the continuous synoptic behavior is corrupted by aliasing from variance unresolved by asynoptic sampling. While some of this contamination may be eliminated by correctly assimilating combined (ascending plus descending) data, the behavior interpolated to synoptic times can be pathological. For random tracer variability the time‐mean field, at least, can be correctly retrieved even if the behavior is undersampled, owing to cancellation of aliases in the averaging process. However, time‐mean distributions of photochemically active species may not be faithfully captured, because diurnal fluctuations alias to the time‐mean, and this aliasing is not eliminated by averaging over time. With the availability of contemporaneous measurements from several instruments viewing different regions of the globe (e.g., the Upper Atmosphere Research Satellite (UARS)), it may be possible to alleviate these difficulties, rooted in sampling deficiencies, by capitalizing on the extended information content of the combined data. The success of such a procedure will hinge on explicitly accounting for sampling irregularities inherent to the collective data ensemble.
Trace gas emissions from a mid‐latitude prescribed chaparral fire
Authors: Cofer Wesley R. , Levine Joel S. , Riggan Philip J. , Sebacher Daniel I. , Winstead Edward L. , Shaw Edwin F. , Brass James A. , Ambrosia Vincent G.
Published: February 2008

Gas samples were collected in smoke plumes over the San Dimas Experimental Forest during a 400‐acre prescribed chaparral fire on December 12, 1986. A helicopter was used to collect gas samples over areas of vigorous flaming combustion and over areas of mixed stages (vigorous/transitional/smoldering) of combustion. Sampling was conducted at altitudes as low as 35 m and as high as 670 m above ground level. The samples, collected in 20‐L Tedlar bags, were returned by helicopter to our field laboratory and immediately transferred to electropolished stainless steel canisters. Analyses for the trace gases carbon dioxide (CO2), carbon monoxide (CO), hydrogen (H2), methane (CH4), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N2O) were performed within hours after collection. Samples of gas were also collected upwind of the burn and analyzed to determine ambient background levels. Mean emission ratios (ΔX/ΔCO2, where X is equal to each species, vol/vol) determined for these gases relative to CO2 were generally lower (except for N2O) than mean emission ratios previously reported for large biomass‐burning field experiments. No substantial differences in CO2 normalized emission ratios for these gases (except for N2O) were determined when samples from vigorously flaming and mixed stages of combustion were compared. Emissions from flaming portions of chaparral, however, would be expected to release disporportionately larger volumes of trace gases into the sampled smoke plumes. This, coupled with the very high surface‐to‐volume fuel ratio typical of a chaparral fire (which minimizes the smoldering stage), may have accounted for the consistency in the emission ratios.
Infrared intensities of some chlorofluorocarbons capable of perturbing the global climate
Authors: Varanasi P. , Chudamani S.
Published: February 2008

The absolute intensities of the strong infrared absorption bands of several chlorofluorocarbons (CFCs) located in the atmospheric window have been measured. The CFCs studied in the present experiments are, in addition to CFC11 and CFC12, CFCs 13, 14, 13B1, 22, 113, 114, and 116.
Accelerating the convergence of seasonal climate models with mixed layer oceans
Authors: Gutowski William J. , Molnar Gyula
Published: February 2008

We explore the possibility accelerating the convergence to statistical equilibrium of seasonal climate models whose ocean is a simple mixed layer. The procedure developed involves reducing the thermal inertia of the ocean and increasing the frequency of the solar forcing cycle during an acceleration period. Determining the appropriate duration and ending time for the acceleration is important, especially for avoiding problems posed by the annual temperature cycle. We present a method for calculating the ending time that requires no knowledge beforehand about details of the model's behavior other than an estimate of the temperature cycle's lag behind the solar forcing cycle. Uncertainties about the coupling between a model's atmosphere and ocean limit the degree of allowable acceleration. Model noise can also limit successful application if high accuracy is demanded. Using a numerical climate model, we obtain savings of over 50% in the amount of time necessary to reach convergence. Our success occurs in part because the accelerated integration's time average temperature field is nearly the same as that of the nonaccelerated integration. The procedure will be less effective in a model whose time average temperature is instead a strong function of the degree of acceleration. The procedure developed is simple to apply and can allow more extensive use of these models to study climate change.
A vertically integrated snow/ice model over land/sea for climate models: 2. Impact on orbital change experiments
Authors: Neeman Binyamin U. , Joseph Joachim H. , Ohring George
Published: February 2008

The VIF sea ice/snow and land snow models developed in a companion paper are implemented in a seasonal dynamic zonally averaged climate model. The simulation of the seasonal cycle of the present climate is compared to climatological data and to results of other models. The addition of ice/snow is found to have interesting consequences for the relative dominance of the opposing winter and summer effects of variations in the Earth's orbital elements, as already implied by Held (1982). In response to a change between extreme high and low summer insolation orbits, it is found that for sea ice (but not for land snow) the winter orbital change dominates over the opposite summer change, causing sea ice shifts which are contrary to the direction predicted by the Milankovitch theory. This is explained by the orbitally induced changes in the length of the seasons, causing insolation anomalies that peak at high latitudes in October and March, coupled with the lag effect of sea ice accretion/Melting/heat storage, large thermal capacity of seawater, and sea ice area‐thermal inertia feedback. On the other hand, for snow over land the shorter but more pronounced summer orbital change dominates, causing shifts in the region of positive annual snow budgets that agree in direction with the Milankovitch theory.
Atmospheric effects of the El Chichón volcanic eruption observed by a multiwavelength sun‐photometer, 1982–1985
Authors: Levizzani V. , Prodi F.
Published: February 2008

A long‐term analysis of turbidity data, obtained by operating a multiwavelength sun‐photometer at a mountain station in northern Italy, has been carried out to investigate the influence of the El Chichón volcanic eruption on the optical characteristics of the atmosphere. An estimate of the vertical load of aerosol particles indicates that it exceeds 2–12 times the normal background value for the station. Aerosol size distributions, obtained by inversion of spectral optical thickness measurements, show a clearly bimodal nature during the period of greater volcanic influence, with the appearance of a distinct large‐particle mode centered between 0.4 and 0.5 μm, revealing the presence of sulphate aerosol particles of volcanic origin in the stratosphere above the station. Sun‐photometric measurements prove to be an effective technique for the analysis of the stratospheric aerosol characteristics and their influence on the Earth's radiation budget. The eight wavelengths of the instrument provide a whole series of spectral information which is not ordinarily obtainable from lidar measurements and leads to specific considerations on the suspended aerosol and its variations in time.
The profile of upwelling 11‐μm radiance through the atmospheric boundary layer overlying the ocean
Authors: Hagan Denise E.
Published: February 2008

The gradient of the upwelling 11‐μm radiance from the ocean surface through the atmospheric boundary layer has been measured with a high‐precision radiometer to test a radiative transfer model prediction of the outgoing sea surface radiance. The measured values of radiance agree with standard line‐by‐line radiative transfer calculations of the outgoing flux to within a few percent, suggesting that present empirical expressions for the water vapor continuum absorption are accurate, at least over the range of atmospheric conditions studied here. Using a pressure squared Weighting function to describe the mean value of the partial pressure of water vapor, the mean absorption coefficient for the spectral range 900–980 cm −1 is determined for the first kilometer vertical path length. For a water vapor mean partial pressure of 0.020 atm and a mean temperature of 20°C the, coefficient is 2.556×10−22 mol−1 cm2 atm−1. When the contribution from line absorption is removed, the coefficient decreases by 15%. Infrared data acquired from a satellite sensor (advanced very high resolution radiometer) are compared with numerical computations of the brightness temperature as seen from space for the measured atmospheric conditions; the observed and modeled values are found to agree to within 0.5°C. The emissivity of the ocean surface is shown to be less than unity by about 1%, a result that is qualified by the possibility of anomalous absorption effects very near the ocean surface. Simple radiative transfer model simulations show that the atmospheric component dominates the total outgoing radiation to space for all but the driest conditions and for average geometries of observation; such predictions are confirmed by the experimental results described here.
A search for large ions in the stratosphere
Authors: Rosen J. M. , Hofmann D. J.
Published: February 2008

A series of balloon soundings was conducted in which the bipolar ion density, conductivity and ion production rate profiles were measured. Near‐simultaneous measurements of the aerosol profile were also made. The results are used to calculate profiles of the effective average mobility and the recombination coefficient. Above the atmospheric boundary layer, both polarities of ions were found to have relatively constant mobilities to balloon ceiling (35 km) with the positive ion mobilities being somewhat smaller at low altitudes and somewhat larger at high altitudes. The absolute value of the mobilities was somewhat smaller than those calculated from measurements of the ion mass. It was also found that the value of the recombination coefficient calculated from the basic flight data agrees well with theory. The basic ion equilibrium equation was tested by making soundings at two locations where the cosmic ray ion production rate differed significantly in the stratosphere. The results indicate that the equation is, in fact, generally applicable to the stratosphere. A considerable effort was made to obtain mobility profiles during atmospheric events when it was believed that there was a high probability of heavy H2SO4 ions being present. However, only minimal evidence was found for the existence of these ions.
Isotopic modeling of climatic oscillations: Implications for a comparative study of marine and ice core records
Authors: Le Treut Hervé , Portes Jacques , Jouzel Jean , Ghil Michael
Published: February 2008

A simple climate model of Quaternary glaciations is combined with a simple isotopic model in order to study phase relationships between δ18O records in deep‐sea cores and in ice cores. Power spectra of the model's climatic and isotopic variables show a dominant peak near 100 kyr (1 kyr = 1000 years), the continuous background of all paleoclimatic spectra, smaller peaks at the orbital periodicities of 41, 23, and 19 kyr, and additional peaks at 14.7, 13, 11.5, 10.4, and 9.5 kyr. Time lags between the model's isotopic profiles are highly variable: ice core events, identified as sharp maxima or minima, can lead apparently homologous events in the marine record or lag them by a few thousand years. This time domain instability of lags is due to the complexity of the power spectrum, with its continuous component and large number of lines. Since the complex spectrum is present in both model and paleoclimatic data, we expect lag relations in the data to be quite variable as well. Independent dating of ice cores is preferable therefore to dating by comparison with marine records. Absolute dating can be based on a combination of ice flow models and of accelerator mass spectroscopy. Time‐averaged cross spectra of independently dated isotopic profiles should be stable and should help us to understand the mechanisms which lead to internal climatic variability.
An algorithm for estimating the water quality parameters from irradiance just below the sea surface
Authors: Sugihara Shigehiko , Kishino Motoaki
Published: February 2008

An algorithm for estimating the water quality parameters such as chlorophyll concentration, backseattering coefficient of particles and absorption coefficient of yellow substance from the irradiance reflectance observed just below the sea surface is developed and discussed with a view to application in optical remote sensing. In this algorithm, an optical model technique is coupled with the fluorescence technique. The computed water quality parameters are compared with those observed directly from concurrent surface water samples. In this comparison, efforts have been made to minimize the number of spectral irradiance reflectances used in the computation while ensuring that computed water quality parameters fit well to the observed ones. The results show that the observed water quality parameters can be closely represented by those computed from at least four selected wavelengths: 480, 520, 600 and 685 nm. Further, it has been observed that a similar approach utilizing three coastal zone color scanner (CZCS) bands, 443, 520 and 620 nm, is applicable for interpretation of CZCS data.
Comparison of LIMS temperatures and geostrophic winds with Berlin radiosonde temperature and wind measurements
Authors: Grose W. L. , Miles T. , Labitzke K. , Pantzke E.
Published: February 2008

The compatibility of radiosonde (RAOB) and satellite temperature and wind data in the lower–middle stratosphere is evaluated via comparison of daily measurements from the Berlin (Tempelhof) RAOB station and colocated synoptically mapped temperature retrievals and geostrophic winds obtained from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) experiment for November 1978 to May 1979. Both on a slowly varying (seasonal) time scale and during large‐amplitude sudden warming episodes, RAOB and LIMS are found to agree quite closely in terms of the local tendency of temperature and horizontal wind speed and direction. The overall similarity between RAOB winds and the LIMS‐derived geostrophic values suggests that the horizontal wind flow in the lower‐middle stratosphere over Berlin is essentially in thermal wind balance. This finding implies that ageostrophic wind motions in this region are rather small in magnitude, approaching the estimated level of uncertainty in the measurement/derivation of RAOB and LIMS winds. Low‐frequency fluctuations are found to dominate the RAOB and LIMS time series. Nevertheless, on occasion, high‐frequency structure in altitude and time appears in the RAOB data. These small‐scale features, which generally possess small amplitudes, are either attenuated or virtually absent from the LIMS time series, consistent with the comparative sampling properties of the two observing systems. The results demonstrate that the LIMS‐mapped temperature and wind analyses represent a valuable resource for investigating large‐scale dynamics and transport.
Stratospheric NO2 over Antarctica as measured by the solar mesosphere explorer during Austral Spring, 1986
Authors: Thomas Ronald J. , Rosenlof Karen H. , Clancy R. Todd , Zawodny Joseph M.
Published: February 2008

The visible spectrometer on the Solar Mesosphere Explorer measured stratospheric NO2 in the 24‐ to 40‐km region. In September and October 1986 the spatial density of the measurements was increased over Antarctica in order to examine the NO2 change during the period of the “ozone hole.” These measurements are compared with 1985 austral spring observations, with northern polar spring measurements for both years, and with model results. A polar low in NO2 is seen between 10 and 24 mbar. The geographic extent of the low decreases as hours of sunlight increase, in marked contrast to the behavior of the total ozone column during the same period. The latitude and time dependence of the NO2 is similar for both years, and during the same season, in the northern hemisphere. Comparison of measurements and model imply that much of the odd nitrogen is converted to HNO3 during the polar night. Observed vertical profiles and comparison to measurements from the ground indicate that the bulk of the NO2 column lies above 24 km. The observed behavior does not appear to be anomalous when compared to simple model calculations, indicating no obvious connection between the polar stratospheric NOx above 24 km and the development of the ozone hole below 24 km.
Component signals in the record of atmospheric carbon dioxide concentration at American Samoa
Authors: Halter Bradley C. , Harris Joyce M. , Conway Thomas J.
Published: February 2008

Variability in atmospheric CO2 concentration over periods of 1–5 days at Cape Matatula, American Samoa, was studied. The variability was found to be the result of the alternating influences of three air mass source regions. Partitioning of Samoa CO2 data according to these air mass source regions revealed annual cycles in the partitioned data sets corresponding to those of the tropical South Pacific, the mid‐latitude southern hemisphere, and the tropical North Pacific regions.
Sulfur dioxide incorporation into ice depositing from the vapor
Authors: Valdez Marc P. , Dawson George A. , Bales Roger C.
Published: February 2008

An experimental study has been made of the incorporation of SO2 into ice depositing from the vapor at −15°C. Surprisingly, SO2 was captured in deposited ice at concentrations comparable to those given by SO2/S(IV) aqueous equilibrium at 0°C. A consequence of this result is that, in the remote troposphere, unrimed snow scavenging ratios for SO2 may be comparable to those for sulfate. In addition, ozone and HCHO appeared to inhibit, rather than enhance, SO2 uptake. An aqueous‐film model is developed to account for SO2 capture. If SO2 dissolves in a liquidlike layer on growing ice surfaces, the concentration of S(IV) species may become enhanced within the layer as a result of retarded diffusional transport away from the advancing ice/layer interface. Such a concentration increase can produce significant solute incorporation into the bulk ice, despite effective solute rejection from the ice.
Analysis of lightning field changes during active Florida thunderstorms
Authors: Koshak William J. , Krider E. Philip
Published: February 2008

A computer algorithm has been developed to derive accurate values of lightning‐caused changes in cloud electric fields under active storm conditions. This algorithm has been applied to data obtained from a network of ground‐based electric field mills at the NASA Kennedy Space Center and the U.S. Air Force Cape Canaveral Air Force Station during portions of two storms. The resulting field changes have been analyzed using a least squares optimization procedure and point‐charge (Q) and point‐dipole (P) models. The results indicate that the values and time variations of the Q‐model parameters under active storm conditions are similar to those reported previously for small storms (Maier and Krider, 1986) when the computations are done with the same analysis criteria and comparable biases. The parameters of P solutions seem to vary with time within the storm interval and from storm to storm. The P vectors at low altitudes all tend to point upward, and those at high altitudes almost always point downward. When a P solution is located in the altitude range corresponding to Q altitudes, the direction of P tends to be horizontal. Since Q solutions typically describe cloud‐to‐ground lightning and P solutions describe cloud discharges (Maier and Krider, 1986), the altitude dependence of the P vectors is consistent with the classic thundercloud charge model that has an excess negative charge at altitudes corresponding to the Q altitudes.
Surface drag over the snow surface of the Antarctic Plateau: 2. Seasonal change of surface drag in the katabatic wind region
Authors: Inoue Jiro
Published: February 2008

The seasonal change of the surface drag coefficient (Cd) over the snow surface in the Antarctic katabatic wind region was evaluated from year‐round wind profile measurements at Mizuho Station, East Antarctica, in 1979. The average stability is near‐neutral throughout the year. Roughness heights (Z0) are estimated from hourly averaged wind speeds at four heights (8, 4, 2, 1, and 1 m) assuming a logarithmic law. Values of Z0 do not vary significantly with wind direction in winter, but they show marked symmetric directional dependence with the smoothest direction around 90° in azimuth in summer. The smoothest direction is formed by the prevailing high wind in a narrow directional range in summer, but it is not formed by high winds in winter because of the scatter over a wider directional range. The results of the first paper can be used throughout the year; Cd10 is estimated to be 0.0013, but decreases to 0.00075 in the smoothest direction in summer. The winter value is similar to previous results over a polar snow surface, but the minimum value in summer is smaller than any previous values in the literature.
Investigation of scene identification algorithms for radiation budget measurements
Authors: Diekmann F. J. , Smith G. L.
Published: February 2008

Computation of the Earth radiation budget from satellite measurements requires identification of the scene in order to select spectral factors and bidirectional models. Evaluation of the effects of scene identification errors on the resulting radiant exitances requires scene identification probability matrices, which quote the probability that a scene which is, in truth, type j is identified as type i. These matrices are empirically evaluated by intercomparing the results from the Earth Radiation Budget Experiment (ERBE) scene identification algorithm with results using Advanced Very High Resolution Radiometer (AVHRR) data. A scene identification procedure is developed for AVHRR data by using radiative transfer models. Scene types for these AVHRR pixels are attached to matching ERBE pixels, and the results are sorted into scene identification probability matrices. These scene intercomparisons explain some of the strengths and problems of the ERBE scene identification algorithm. A tendency for underestimation of cloudiness over ocean at high cloud amounts for the ERBE relative to the AVHRR results is found and explained. Estimates of the errors of exitances due to scene misidentification demonstrate the high dependency on the probability matrices. While the longwave error can generally be neglected, the shortwave deviations can reach maximum values of more than 13% of the respective exitances.
Measurements of NOx over the eastern Pacific Ocean and southwestern United States during the spring 1984 NASA GTE aircraft program
Authors: Ridley B. A. , Carroll M. A. , Dunlap D. D. , Trainer M. , Sachse G. W. , Gregory G. L. , Condon E. P.
Published: February 2008

Measurements of NO, NOx (NO + NO2), O3, and CO are presented from seven aircraft flights made over the eastern Pacific Ocean and the southwestern United States in spring of 1984. The sampling region was characterized by large‐ and small‐scale variability for all of the measurements, likely as a result of vigorous synoptic‐scale meteorology and the influence of tropopause folds. Median values for NO, NOx, O3, and CO from the flights made over the ocean in the region of 5.8–7.6 km were 10 parts per trillion by volume (pptv), 32 pptv, 46 parts per billion by volume (ppbv) and 120 ppbv, respectively. Corresponding values from two flights made over the continent at similar altitudes were 16 pptv, 38 pptv, 42 ppbv, and 111 ppbv. There was a strong tendency for NO or NOx to be correlated positively with O3 and to be anticorrelated with dew‐point/frost‐point measurements. No significant overall correlation occurred between NOx and CO for the ocean data. The variability of NOx was such that regions of net destruction and regions of net production of O3 were sampled both over the ocean and over the continent. However, in the middle free troposphere over the ocean, net O3 destruction was predominant.