bluuebunny/crossref_metadata_2025 huggingface dataset:
The Saudi Arabian heat low: Aerosol distributions and thermodynamic structure
Authors: Ackerman Steven A. , Cox Stephen K.
Published: February 2008

Radiation and microphysical data are employed to deduce the bulk radiative and microphysical characteristics of the aerosol layer over the Saudi Arabian Peninsula and the adjacent Arabian Sea. Observed particle size distributions, total mass loadings, and vertical distributions of the dust are presented for five analysis periods. There is a large daily variability of the dust mass loading over the desert. The broadband radiative characteristics of the dust are inferred by comparing calculations for a dust free atmosphere with in situ broadband radiative measurements. The dust had no detectable effect on the longwave radiative fluxes, while it approximately doubled the clear sky shortwave absorption. The total shortwave absorption by the dust is dependent on the underlying surface albedo. The solar absorptance of the dust is expressed in terms of the dust mass loading and is incorporated into a broadband shortwave radiative transfer model to assess the surface and tropospheric energy budgets. For the desert cases the dust is largely responsible for a net 24 hour radiative energy convergence between, 530 and 800 mbar. A 24‐hour radiative energy convergence is also found over the ocean; however, the layer depth is shallower than the desert case, being limited to the top of the dust layer. The thermodynamic structure of the heat low is presented. Calculations of temperature advection from the Saudi Arabian Peninsula to the Arabian Sea, suggest that horizontal advection aids in offsetting a net 24 hour tropospheric energy convergence over the desert. This warm air advection, along with the transport of dust over the Arabian Sea, may assist in maintaining the low level inversion and shallow moist layer observed over the western and central Arabian Sea.
Recent long‐term moored instrument observations in the western North Pacific
Authors: Schmitz William J. , Niiler Pearn P. , Bernstein Robert L. , Holland William R.
Published: February 2008

Selected results based on the first deployment (duration was 298–324 days depending on specific location) of an array of 38 current‐temperature meters on 10 moorings along 152°E from 28°N to 41°N are discussed. Abyssal eddy kinetic energies along 152°E near the Kuroshio Extension are a factor of 2 to possibly 5 lower than those previously observed at similar depths close to the energetic regions of the Gulf Stream. The thermocline kinetic energy frequency distribution at 28°N, 152°E is similar in shape to that observed at a site near 31°N, 70°W (but not 28°N, 70°W), although the total energy levels are quite different. However, the distance from the corresponding strong current regimes is nearly the same. The largest scale latitudinal distribution of the off‐diagonal component of horizontal Reynolds' stress has a characteristic general shape, that is, negative to the south and positive to the north of the Gulf Stream or Kuroshio Extension or mid‐latitude jet, at all depths for all longitudes where such data are available in both oceans, and in the numerical experiments examined.
Gulf Stream meanders: Observations on propagation and growth
Authors: Watts D. Randolph , Johns William E.
Published: February 2008

We present a new method for continuously tracking the location of the Gulf Stream using a moored array of inverted echo sounders. Time series of lateral displacements of the front, shown accurate to ± 8 km, have been collected along three sections spaced 100, 150, and 200 km downstream (NE) of Cape Hatteras, North Carolina, for a period of 12 months. These records are highly coherent at all periodicities longer than 4 days. From the observed phase lags, a dispersion relationship is presented for the meanders: As the period and wavelength (T, λ) increase from (4 days, 180 km) to (30 days, 600 km), the phase speed decreases smoothly from 40 to 20 km d−1. The meanders exhibited rapid growth at periods longer than 4 days, doubling in variance in each 50‐km step downstream. This downstream growth is most appropriately described by a spatial e‐folding scale κ−1 ∼400 km for (T, λ) ≲ (9 days, 300 km), and a temporal e‐folding scale σ−1 ∼ 6 days for (T, λ) ≳ (14 days, 400 km).
Some results of climatic generalization of meteorological observations in the Antarctic
Authors: Borisenkov E. P. , Dolganov L. V.
Published: February 2008

Some new climatic characteristics of the Antarctic are presented. Maps of atmospheric pressure, temperature, humidity, and wind regime, as well as probabilistic curves detailing the Antarctic climate, particularly in terms of extreme values, are given.
Sensitivity of an annual mean diffusive energy balance model with an ice sheet
Authors: Bowman Kenneth P.
Published: February 2008

The sensitivity of a diffusive energy balance model that contains a simple ice sheet is compared with that of a model with snow cover only. The effect of the elevated ice sheet surface on the radiative cooling is calculated by using a radiative transfer model. Because the temperature in the atmosphere decreases with height, the main effect of the ice sheet elevation is to reduce the outgoing infrared radiation. This reduction in the radiative cooling decreases the sensitivity of the ice sheet size to changes in the solar constant by partially counteracting the albedo feedback. For a reasonable choice of parameters, this effect can reduce the strength of the albedo feedback by a factor of 2.
Study of the particulate sulfur‐light scattering relationship using in situ aerosol thermal analysis
Authors: Cobourn W. Geoffrey , Husar Rudolf B.
Published: February 2008

Light scattering coefficient and particulate sulfur concentrations were monitored continuously in St. Louis from July 1977 to June 1978. The measurements were made with an in situ aerosol thermal analysis system, which performed a thermal separation on each of the two aerosol parameters. Each parameter was divided into a number of components by volatility, so that the corresponding components of light scattering coefficient and particulate sulfur concentration could be compared, both individually and statistically. During one summer event, particulate sulfur compounds (and associated water) were estimated to contribute 60–80% to particle light scattering; during another summer event, the percentage was about 66%; and during one winter event, the percentage contribution was less than 41%. The statistical analyses indicated approximately equal scattering efficiencies for sulfuric acid and ammonium sulfate salt compounds. It is estimated that the average overall sulfur percentage contribution to particle light scattering during the July 1977 to June 1978 study period was 50–75%.
Uncertainties of predictions of future atmospheric CO2 concentrations
Authors: Oeschger H. , Heimann M.
Published: February 2008

Linear carbon cycle models, tuned to reproduce the CO2 increase observed at Mauna Loa, independently of their individual assumptions, predict almost identical CO2 concentration trends for fossil energy scenarios assuming a slightly increasing production in the next few decades. The basic information for such prognoses therefore is the airborne fraction observed over the last 20 years. Uncertainties in this quantity are due to possible errors in the estimate of fossil fuel consumption and the corresponding CO2 emission, possible natural fluctuations in the baseline CO2 level, and uncertainties regarding the biospheric CO2 input and uptake as a result of deforestation and reforestation and land management. Depending on different assumptions the effective airborne fraction, defined as the ratio of CO2 increase due to fossil fuel CO2 alone to the integrated CO2 production, might be as low as 0.38 or as high as 0.72, compared to the apparent airborne fraction of 0.55. The effective airborne fraction derived from carbon cycle models, considering only the CO2 uptake by the ocean, lies in the range 0.60–0.70. A value as low as 0.40 seems therefore highly improbable. A high biospheric anthropogenic CO2 input therefore must have been accompanied by a high CO2 fertilization effect. Model considerations, however, are not in contradiction with a high biospheric input with the maximum production before 1958, which also would imply low preindustrial CO2 concentrations in the range 270–280 ppm as reported recently.
CO2 and radon 222 as tracers for atmospheric transport
Authors: Dörr H. , Kromer B. , Levin I. , Münnich K. O. , Volpp H.‐J.
Published: February 2008

Time variations of the CO2 concentration and the radon 222 daughter activity in the atmosphere are observed 16 m above the ground in the outskirts of Heidelberg (Germany), situated in the rather densely populated and intensively cultivated upper Rhine valley. These parallel recorded data series are used to estimate the CO2 respiration rate from the soil and from plant leaves. Atmospheric concentration variations of both gases appear to be merely due to variations in atmospheric mixing. From direct measurements of concentration profiles in the soil air we deduce the 222Rn exhalation rate, which is nearly constant with time and about 4000 dpm m−2 h−1. This flux is consistent with the one derived from observed pileup of the 222Rn activity of an air mass during passage over the continent. The constant 222Rn exhalation rate quoted serves as a reference for atmospheric dilution of the soil‐borne CO2. The comparison of the two concentrations leads to a total CO2 respiration flux to the atmosphere of 21 mmol CO2 m−2 h−1 for a short time period in August 1980. Direct measurements derived from CO2 concentration profiles in the soil yield an average regional CO2 flux from the soil alone of 12 mmol m−2 h−1 with a maximum of 20 mmol m−2 h−1 in June and July and a minimum of 3 mmol m−2 h−1 or less in winter. The different 222Rn exhalation rates from the continent and ocean (where it is smaller by 2 orders of magnitude) are further used to identify the continental or the maritime origin of air masses.
On the relationship between the greenhouse effect, atmospheric photochemistry, and species distribution
Authors: Callis Linwood B. , Natarajan Murali , Boughner Robert E.
Published: February 2008

A radiative‐convective‐photochemical model that extends from 0 to 53 km is used to examine the effect on atmospheric constituents and thermal structure of changes in the atmospheric levels of CO2, CFM's, CO, N2O, and combinations of these species. Calculations were carried out for two reference atmospheres, one with high (HINOX) and one with low (LONOX) levels of NOx. The HINOX atmosphere has a vertical distribution of NOx similar to that resulting from recently published measurements. Such a distribution requires an unrealistically large value for the integrated tropospheric source of NOx. This suggests that the HINOX profile, and the measurements from which it was drawn, are more characteristic of contaminated, rather than clean, air masses. The HINOX troposphere provides a net photochemical source of O3 and is not greatly sensitive to downward transport of O3 from the stratosphere. The LONOX troposphere is a photochemical sink for O3 and, as a result, is sensitive to such variations in downward transport. Results of this study suggest that (1) infrared opacity changes due to CO2 and CFM increases can cause significant changes in tropospheric O3, OH, CH4, CO, and other species through changes in tropospheric water vapor; (2) perturbation or sensitivity studies conducted with tropospheric photochemical models may be subject to significant errors due to the absence of modulating effects provided by the stratosphere; (3) the response to given perturbations is significantly dependent upon the tropospheric NOx distribution present in the model; (4) CO2 growth rates must be included in the calculation of CFM‐O3 time scenarios and must account for surface temperature changes, especially in the steady state; and (5) that thermal or chemical perturbations introduce a variety of coupling or interactive mechanisms which are significant and which may provide compensating effects.
Absolute band strengths of halocarbons F‐11 and F‐12 in the 8‐ to 16‐μm region
Authors: Kagann R. H. , Elkins J. W. , Sams R. L.
Published: February 2008

The infrared strengths of three vibrational band systems of halocarbon F‐11 and four vibrational band systems of halocarbon F‐12 in the ‘atmospheric window’ between 8 and 16 μm were measured at 296±1 K using a Fourier transform infrared spectrometer. These results were obtained at a maximum instrumental resolution of 0.06 cm−1 Our measurements of the total infrared band strengths for F‐11 and F‐12 would indicate approximately 17% and 5% greater absorbance, respectively, than those strengths used in recent greenhouse warming calculations by Ramanathan (1975), Wang et al. (1976), and Lacis et al. (1981), and consequently, a corresponding increase in the possible atmospheric warming effect by these halocarbons.
Applications of SEASAT altimeter data in seismotectonic studies of the south‐central PACIFIC
Authors: Sailor Richard V. , Okal Emile A.
Published: February 2008

Individual tracks of SEASAT altimeter data can be used effectively to identify significant bathymetric features in remote and unsurveyed ocean areas. It Is especially important, for studies of oceanic seismicity, to identify correlation (or lack of correlation) between seismicity and bathymetric features. However, in many seismically active regions, bathymetric data are sparse or nonexistent. A typical example is the south‐central Pacific, an area studied by Okal et al. (1980), who identified several sites of active intraplate seismicity. The purpose of the present paper is to demonstrate how SEASAT data can be used to aid in bathymetric and seismotectonic Interpretation of this remote ocean area. We present two illustrations: (1) SEASAT observations of Macdonald seamount, a volcanically active seamount representing the youngest member in the Austral Island chain, and (2) SEASAT observation of a previously undiscovered fracture zone located at approximately 21.4°S and trending east‐west between 2320E and 236°E. This fracture zone is located approximately 70 km to the south of a small region of active seismicity (96 events of magnitude greater than 2.7 from 1976 to 1980). On the basis of the demonstrated ability to observe active seamounts such as Macdonald and small fracture zones, we conclude that the observed seismicity in the region near 21°S, 233°E is due to intraplate stresses but is not associated with large‐scale volcanism or with an active or fossil fracture zone.
Detection of Massachusetts Bay internal waves by the synthetic aperture radar (SAR) on SEASAT
Authors: Trask Richard P. , Briscoe Melbourne G.
Published: February 2008

We have examined all eight SEASAT passes over Massachusetts Bay that yielded synthetic aperture radar (SAR) imagery. Four of the passes showed banded surface features that suggested a group of internal waves propagating southwestward from Stellwagen Bank. Comparison of the positions of the SAR features with predictions of internal wave locations derived from earlier in situ work at Massachusetts Bay confirms that the SAR features are indeed rough and smooth bands of water caused by a propagating packet of internal waves. (The packet is caused by tidal currents interacting with the stratification over and the topography of Stellwagen Bank.) Even the four passes that do not show internal waves are consistent with the above conclusions since the predicted packet positions occur outside the region covered by those four passes. These comparisons are presented to show that the SEASAT SAR is indeed capable of detecting internal waves in Massachusetts Bay, even though these waves are considerably less intense than in some other reported areas of the world.
Total precipitable water and rainfall determinations from the SEASAT scanning multichannel microwave radiometer
Authors: Alishouse John C.
Published: February 2008

Three of the SEASAT scanning multichannel microwave radiometer's (SMMR's) five frequencies can be used to determine the total precipitable water in the atmosphere, the liquid water content, and the rainfall rate. In addition, two distinct algorithms were used to derive geophysical parameters from brightness temperature. Comparisons with surface observations from the Gulf of Alaska SEASAT Experiment and other selected sources were made for both algorithms. Generally, very good agreement was found between satellite and radiosonde observations of total precipitable water. An estimate of the precision of radiosonde‐derived total precipitable water amounts was made. Comparisons of precipitation occurrence as determined from the SMMR and surface observations also were made. In the tropics, very good agreement is found between satellite and surface observations. In the mid‐latitudes (Gulf of Alaska) it is found that small cells of precipitation are often missed by the SMMR but larger synoptic scale precipitation is detected.
Property distributions and deep chemical measurements within the western Gulf of Mexico
Authors: Morrison John M. , Merrell William J. , Key Robert M. , Key Tonalee C.
Published: February 2008

Distribution of salinity, dissolved oxygen, nitrate, phosphate, and silicate are presented for the western Gulf of Mexico in 1978. Plots of chemical concentration versus potential density are used to identify the presence of gulf water, tropical Atlantic central water, Antarctic intermediate water, Caribbean midwater, and upper North Atlantic deep water within the upper 1600 m of the western Gulf of Mexico. Property distributions are closely related to the current regime described by Merrell and Morrison (1981). Also, we present values for tritium, carbon 14, radium 226, and radon 222 that were taken at a deep station located at 23°02′N and 92°28′W.
Tidal phase of internal‐wave generation
Authors: Sawyer C.
Published: February 2008

The tidal phase at which ocean internal waves are generated is examined by using two sets of data. The first data set, consisting of 21 time series of internal‐wave packets located with respect to the continental shelf edge on satellite images, clearly indicates generation near flood tide. In the second data set, observations of thermal oscillations shoreward of a sill can be modeled either as generated shortly after ebb tide on the seaward side of the sill or slightly before flood on the shoreward side. The absence in both sets of observations of evidence of internal waves over the sill or seaward of the sill points to flood generation at the sill as well as at the shelf. The shelf edge is found to be the most likely site of tidal generation of internal waves observed over the shelf.
A comparison between computed and measured oceanic winds near the British Columbia coast
Authors: Thomson Richard E.
Published: February 2008

Winds measured over the continental shelf off Vancouver Island during the summers of 1979 and 1980 are compared with winds computed by the National Marine Fisheries Service (Monterey, California), using synoptic surface atmospheric pressures. Although there is considerable qualitative similarity between the two sets of data, the computed 6‐hourly winds fail accurately to resolve short‐period fluctuations associated with transient wind systems and tend to underestimate the percentages of time of low and high wind speeds. In the frequency domain, the computed winds are representative of the oceanic winds for periods exceeding roughly 2 days but only marginally representative for periods of 1½–2 days. At periods less than about 1½ days, computed winds are not reliable indicators of oceanic wind variability. Moreover, the computed winds possess a large‐amplitude sea breeze (diurnal) component that is present in the inner shelf wind data but not in the outer shelf wind data. This sea breeze component in the computed winds originates through use of land‐based atmospheric pressure values and is not indicative of the offshore wind field. Spectra of the observed winds suggest a k−5/3law behavior (k is the horizontal wave number) consistent with the existence of a mesoscale, two‐dimensional, reverse cascading energy inertial range. Spectra for computed winds, on the other hand, are more consistent with a k−3 law appropriate to geostrophic turbulence and the existence of a macroscale, two‐dimensional, cascading enstrophy inertial range.
A model of the atmospheric boundary layer over the marginal ice zone
Authors: Overland J. E. , Reynolds R. Michael , Pease C. H.
Published: February 2008

A one‐layer, primitive equation model is presented for the atmospheric boundary layer over the marginal ice zone (MIZ). The model simulates the slow rate of inversion growth and rate of warming of the boundary layer seaward of an ice edge for off‐ice winds observed on two cruises in the Bering Sea by the NOAA R/V Surveyor. The horizontal temperature gradient in the boundary layer, caused by the oceanic heat flux seaward of an ice edge, induced an increase in wind speed with a maximum increase of 8% at 50 km seaward of the edge. At 100 km off ice, a momentum balance is established between accelerative terms (boundary layer baroclinity, momentum entrainment, synoptic‐scale scale pressure gradient) and decelerative terms (surface drag and the local pressure force resulting from inversion rise). Wind velocity in the boundary later over the MIZ during off‐ice winds is sensitive to changes in surface roughness. When an MIZ is modeled as a smooth interior (CD = 2 × 10−3) and a 30‐km‐wide rough marginal ice zone (CD = 3.8 × 10−3) with an unstable surface layer over the ocean, the model shows a decrease in wind speed of 9% at the windward side of the MIZ and an 18% increase in wind speed from 5 km interior to the ice edge to 40 km seaward of the edge. These results suggest an atmospheric mechanism for rafting at the windward side of the marginal ice zone, divergence of the ice at the edge, and ice‐band formation seaward of the edge.
Sea ice melting in the marginal ice zone
Authors: Josberger Edward G.
Published: February 2008

The heat and salt flux boundary conditions together with the freezing curve relationship are a necessary component of any ice‐sea water thermodynamic model. A neutral two‐layer oceanic planetary boundary layer model that incorporates these boundary conditions gives the following results: The interfacial salinity is within 10% of the far‐field salinity for conditions commonly encountered in the MIZ and depends only on the turbulent Lewis number and the far‐field temperature and salinity. The predicted melt rates agree with the limited field observations, of the order of 1 m day−1. The Obukov lengths, determined from the predicted interface conditions and melt rates, are generally much greater than the Ekman layer thicknesses; hence, the surface buoyancy flux has little effect on the turbulence in the planetary boundary layer.
The delta band dissociation of nitric oxide: A potential mechanism for coupling thermospheric variations to the mesosphere and stratosphere
Authors: Frederick J. E. , Abrams R. B. , Crutzen P. J.
Published: February 2008

Depletion of solar radiation at discrete wavelengths by nitric oxide has a significant impact on the dissociation rate of this gas in the δ(0, 0) and δ(1, 0) bands. Inclusion of the opacity provided by a typical NO profile reduces the dissociation rate in the upper stratosphere to 50–70% of that predicted when the optical depth calculation omits this contribution. A substantial fraction of the nitric oxide column abundance as measured near the stratopause resides in the lower thermosphere where correlations of NO with solar and magnetic activity are well documented. Variations in the thermospheric NO abundance therefore modulate the radiation field at the precise wavelengths absorbed by this molecule in the mesosphere and upper stratosphere. Predicted changes in the dissociation rate arising from a varying thermospheric opacity exceed 8% throughout the mesosphere and reach 15% between 65 km and 95 km.
Determining the form drag contribution to the total stress of the atmospheric flow over ridged sea ice
Authors: Joffre Sylvain M.
Published: February 2008

Profile measurements from a meteorological mast installed in the middle of a sea ice floe in the Bothnian Bay allowed the skin roughness parameter and drag to be computed. Radiosonde and pibal profiles at the same location enabled the large‐scale stress and roughness parameter to be estimated by the geostrophic departure method. The generally significant form drag contribution appears to depend also on thermal stability. These results are compared with the predictions from a model of Arya (1975) as a function of sea ice surface features statistics. The qualitative agreement is good, but uncertainty in the numerical values is considerable.
On the response of a wind‐driven current over a continental shelf
Authors: Mæland Einar
Published: February 2008

The response of a coastal current forced by a steady wind stress over a sloping continental shelf is investigated. A Laplace transform technique is used, and it is shown that in the adjustment to a steady state the response consists of a damped, propagating disturbance, carrying energy offshore and longshore. This may be associated with shelf waves, but the response is not related to any poles of the image function. The spectrum is continuous, and a discrete set of ‘normal modes’ does not exist.
Temperature and current variability of a Gulf Stream meander observed off Onslow Bay, August 1977
Authors: Levine Edward R. , Bergin John M.
Published: February 2008

Eighteen temperature sections were obtained during August 1977 using expendable bathythermograph probes along a 110 km tract oriented perpendicular to the mean direction of the Gulf Stream off Onslow Bay. Concurrent velocity and temperature measurements were obtained beneath the Stream from an Aanderra current meter moored 48 m above the bottom (620 m depth). The measurements revealed the passage of a Gulf Stream meander with a period of approximately 5 days, vertical changes in isotherm level as large as 200 m, and a lateral meander amplitude of approximately 39 km as defined by the 16°C isotherm at 200 m. A study of the meander amplitude as a function of depth is carried out in terms of the migration of the sloping frontal surface. The envelope of frontal migration is defined by curves which are found to approximate the bottom slope down to the ‘knee’ in the bottom topography at 700 m. The peak‐to‐peak meander amplitude decreases from 39 km near the sea surface to 26 km at a depth of 700 m, which suggests that the meander process off Onslow Bay is not confined to the upper slope. A strong correlation exists between the current and temperature field at the moored near‐bottom sensor and frontal migration at the 200 m level with the overall impression that the meander process has an extensive horizontal correlation scale, comparable to the width of the Gulf Stream. A downstream phase speed of 25 cm/s is derived for the meander based on a relationship between characteristics of the temperature field and characteristics of the velocity field.
CO2 radiative parameterization used in climate models: Comparison with narrow band models and with laboratory data
Authors: Kiehl J. T. , Ramanathan V.
Published: February 2008

Absorptances for the 15‐μm band system of CO2 are calculated from three models: the Goody model, the Malkmus model, and a wide band formulation. The wide band formulation used in this study explicitly accounts for hot and isotopic bands of CO2. Comparison is made between these calculated absorptances and measured absorptances. The band models are in good agreement with the measured absorptances. The sensitivity of these models to increased CO2 is investigated by intercomparing flux and heating rate changes computed by the three models. It is concluded that little difference exists between the narrow band and the wide band absorptance models, provided the wide band models account explicitly for the various hot and isotopic bands of CO2. We show that significant errors result if the Goody or Malkmus model is applied to spectral intervals larger than 10 cm−1. Thus, our results suggest that climate models that employ Goody or Malkmus type models with coarser spectral resolution (>10 cm−1) may be subject to errors (in CO2 fluxes and heating rates) larger than 10%. We also show the differences between the narrow and the wide band model treatment of H2O‐CO2 overlap in the 15‐μm region. The H2O continuum absorption in the 15‐μm region alters significantly the vertical distribution of CO2 heating in the lower troposphere.
Analysis of upper stratospheric ozone profile data from the ground‐based umkehr method and the Nimbus‐4 BUV satellite experiment
Authors: Reinsel Gregory , Tiao G. C. , Lewis R. , Bobkoski M.
Published: February 2008

We present a statistical trend analysis of stratospheric ozone profile data in the five highest Umkehr layers (layers 5–9), which cover approximately the 24 to 48 km region of the stratosphere, from the ground‐based Umkehr measurements and from the Nimbus‐4 BUV satellite experiment. Time series modeling of monthly Umkehr profile ozone data in Umkehr layers 5–9 from a collection of 13 ground‐based Dobson stations over the period 1958–1980 is considered for the detection of trends that may be associated with the release of CFMs. Using a random effects model to account for various sources of variation among individual station trend estimates in each Umkehr layer, our findings show little evidence of any significant trend in ozone in any of the Umkehr layers over the period 1970–1980. These trend results depend to some extent, of course, on the particular choice of explanatory factors employed in the time series models to describe variations in the Umkehr data. A possibly important source of variation on the Umkehr data, especially in the uppermost two or three layers, which has not been explicitly accounted for in these models is the presence of stratospheric aerosols, caused primarily by volcanic activity. The possible impact of such aerosol effects on long‐term trend estimates obtained from Umkehr data is currently under investigation, and results of such an analysis will be presented in a future report. We also analyze BUV ozone profile data from the Nimbus‐4 satellite over the period April 1970 to April 1977. These BUV profile data have first been interpolated to yield ozone amounts corresponding to the Umkehr layers 5–9. The globe has then been made into a grid with blocks of 10° latitude by 20° longitude, and monthly averages of ozone have been computed for the layers 5–9 for each block. Linear regression models that contain a linear trend term are estimated from the monthly BUV time series data for each of the five Umkehr layers in each block over the 7 year period April 1970 to April 1977. The results show a large negative overall trend on the order of 1.5 to 2.0% per year in the BUV data at Umkehr layers 8 and 9, with little or no trend indicated in layers 5 and 6. However, a comparison of monthly BUV satellite data with the corresponding Umkehr ground profile ozone data is also performed, which indicates a substantial downward drift in the BUV data at layers 8 and 9, relative to the collection of Umkehr stations, of about the same magnitude as the estimated trend in BUV data in those layers.
Turbulence originating from convectively stable internal waves
Authors: Lindzen R. S. , Forbes J.
Published: February 2008

A theory has recently been developed for the generation of turbulence by unstable tides and gravity waves (Lindzen, 1981). Omitted from this theory was consideration of the possibility that turbulence could be generated by gravity waves which were not convectively unstable (i.e., breaking). The possibility of such generation was suggested by a result of McComas and Bretherton (1977) showing that internal gravity waves are indeed unstable to other gravity waves with shorter wavelengths. The present paper estimates the maximum turbulence which might be generated by such a process and shows that even this turbulence would not greatly alter earlier results.
On some radiative features of the el chichon volcanic stratospheric dust cloud and a cloud of unknown origin observed at Mauna Loa
Authors: Deluisi John J. , Dutton Ellsworth G. , Coulson Kinsell L. , DeFoor Thomas E. , Mendonca Bernard G.
Published: February 2008

We present some results of our initial optical observations of the El Chichon volcanic cloud. These observations were made at the Geophysical Monitoring for Climatic Change Mauna Loa Observatory, Hawaii, and consist of lidar profiles, optical thickness, spectral variation in optical thickness and changes in global and direct solar broadband fluxes. Particle size distribution and cloud mass information contained in the optical thickness observations are discussed. It is clear that the atmospheric radiative effects of the El Chichon cloud far exceed the effects of all other volcanic clouds observed at Mauna Loa since observations were begun in 1958.
The Atmospheric Lifetime Experiment: 6. Results for carbon tetrachloride based on 3 years data
Authors: Simmonds P. G. , Alyea F. N. , Cardelino C. A. , Crawford A. J. , Cunnold D. M. , Lane B. C. , Lovelock J. E. , Prinn R. G. , Rasmussen R. A.
Published: February 2008

The automated electron capture gas chromatographic determination of the atmospheric concentrations of CCl4 are reported for the period July 1978 to June 1981 at five coastal monitoring stations, Adrigole (Ireland), Cape Meares (Oregon), Ragged Point (Barbados, West Indies), Point Matatula (American Samoa), and Cape Grim (Tasmania). Daily measurements at approximately 6‐hourly intervals are always complimented by an equivalent number of on‐site calibration measurements. Estimates of CCl4 emissions to the atmosphere from known industrial sources are compared with the measured trends and the absolute values of the observed concentrations. A globally averaged atmospheric lifetime for CCl4 is calculated by using an optimal estimation technique incorporating a nine‐box model of the atmosphere. The average global concentration of CCl4 from July 1978 to June 1981 in the lower troposphere was 118 pptv, and it was increasing 2.1 pptv/year over this period. Both the absolute concentration observed and its trend are consistent with the calculated releases of CCl4 and its expected destruction by stratospheric photolysis.
The turbulent electrode effect as influenced by interfacial ion transfer
Authors: Willett John C.
Published: February 2008

The turbulent electrode effect at the earth's surface is treated as an exchange of small and large ions between the atmosphere and an aerodynamically rough boundary. Results of past experimental and theoretical work on the interfacial transfer of gases and small particles between the surface layer and the ocean or vegetated land are reviewed to establish the correct boundary conditions. The conclusion that the conductivity does not vanish at the effective lower boundary implies that charge separated by the conduction current there must be accounted for. This leads to the development of a new physical model of the electrode effect which is applied over the ocean, ignoring aerosol attachment, and over land, assuming that attachment predominates over recombination of small ions. The strong‐turbulence limit of Willett (1978) can still be exploited in many circumstances to yield a simplified, linear, mathematical description of charge convection in the “electrode layer.” It is concluded that this layer produces upward convection currents with magnitudes between 60 and 90% of the total fair‐weather current density over a wide variety of conditions. The effects of “surface radioactivity” appear to be small unless the ionization rate is enhanced by a large factor within the plant canopy.
Star line‐of‐sight refraction observations from the Orbiting Astronomical Observatory Copernicus and deduction of stratospheric structure in the tropical region
Authors: White Robert L. , Tanner Walter E. , Polidan Ronald S.
Published: February 2008

Night‐time observations from the orbiting astronomical observatory Copernicus on May 14 and July 11, 1980, of visible light refraction by the limb of the atmosphere are presented. Irregularities of the measured refraction angle are then interpreted to be probably the result of the thermal fine structure in the stratosphere. The observations are very sensitive to horizontally stratified structures with temperature deviations of 2 to 5°K, if the vertical dimension is less than 3 km. Since under selected geometric conditions the star's line of sight to the orbiting satellite sweeps out hundreds of kilometers at almost constant altitude, the observations are used to estimate the horizontal dimensions of thermal structures; Particularly large structures were found in the ozone region of the stratosphere. The refraction measurements are in general agreement with balloon soundings, UHF vertical soundings, and infrared radiometer observations of the limb.
The optical power radiated by lightning return strokes
Authors: Guo Changming , Krider E. Philip
Published: February 2008

During 1981 the optical signals radiated by Florida lightning were recorded in correlation with wideband electric field signatures. Measurements of the initial linear slopes of the signals produced by return strokes in the 0.4‐ to 1.1‐μm wavelength interval indicate that the space‐and‐time‐averaged radiance emitted during the early phase of first strokes averages about 1.3±1.2×106 W/m and that subsequent strokes produce about 3.9±4.9 × 105 W/m, values that are in reasonably good agreement with those obtained in 1980 by Guo and Krider (1982) who used a different detector at longer ranges. The average peak radiance in subsequent return strokes near the ground is estimated to be in the range from about 6×105 W/m to 1×106 W/m.
Measurement of high frequency waves using a wave follower
Authors: Tang S. , Shemdin O. H.
Published: February 2008

High frequency waves were measured using a laser‐optical sensor mounted on a wave follower. Measured down‐wind wave slope spectra are shown to be wind speed dependent; the mean square wave‐slopes are generally larger than those measured by Cox and Munk (1954) using the sun glitter method.
A model study of the effects of intermittent loss on odd nitrogen concentrations in the lower troposphere
Authors: Stewart Richard W. , Hameed Sultan , Matloff Gregory
Published: February 2008

We have developed a time‐dependent box model of the lower troposphere which includes a description of photochemical and physical processes. This model has been applied to the calculation of nitric acid and NOx (NO + NO2) concentrations over a diurnal cycle which includes precipitation. Nitric acid concentrations and the HNO3/NOx ratio are found to be highly variable under the assumptions regarding the frequency, duration, and intensity of precipitation employed in this model. The chemistry of odd nitrogen compounds during the night is potentially important in establishing the level of nitric acid in the lower troposphere. These calculations also indicate that relatively large (factor of 2) errors may occur when the continuity equation describing nitric acid variations is averaged over a diurnal cycle which includes precipitation. Interpretation of simultaneous measurements of HNO3 and NOx will require some knowledge of the history of the observed air mass and may require an improved understanding of nighttime odd nitrogen chemistry.
Stratospheric‐tropospheric ozone exchange in Antarctica caused by mountain waves
Authors: Robinson Elmer , Clark David , Cronn Dagmar R. , Bamesberger W. Lee , Hogan Austin W.
Published: February 2008

Under suitable meteorological conditions, mountainous terrain may induce atmospheric wave formations that propagate across the tropopause and into the stratosphere. This study presents results of a NSF C‐130 research aircraft flight over the Ellsworth Mountains of Antarctica (78°S, 85°W) on December 3–4, 1978. The aircraft was in the study area for more than 6 hours and flew a total of 14 flight tracks generally parallel to the mountain ridge at 4 primary altitudes between 7.3 and 8.7 km, MSL. Data analyses included horizontal and cross‐sectional fields of temperature, potential temperature, ozone, frost point, and wind. The results showed that over the mountain area there was a pattern of changes in these variables that could be explained by the apparent vertical motion expected to occur in mountain wave situations. In this case there was vertical displacement of air parcels across the tropopause zone that was shown by ozone and potential temperature patterns. In the patterns at various constant levels the measured values appear to be organized into a series of bands or zones characteristic of wave troughs and ridges oriented across the mean wind direction and parallel to the terrain ridges. Ozone flux calculations were made by using concentrations measured in upwind and downwind zones. The results showed that at about 7.4 km, 1.1 km below the tropopause, the flux of ozone leaving the mountain wave zone was 268 μgm−2 s−1. This was a 61% increase over the incoming ozone flux of 167μgm−2 s−1. This increased flux produces a change in concentration at the 7.4 km altitude from about 12 ppb in the background air flow to about 20 ppb downwind of the mountains. The downwind flux was larger above 7.4 km. It is concluded that the increases in ozone observed in the downwind tropospheric layers were the result of mountain wave‐induced downward mixing of ozone‐rich stratospheric air parcels.
Topographic and inertial waves on the continental rise of the Mid‐Atlantic Bight
Authors: Hamilton Peter
Published: February 2008

Analysis of an array of four closely spaced moorings, 2800 m water depth, instrumented by near‐bottom current meters, has been performed with a view to isolating coherent wave motions in the low‐frequency and inertial bands. The low‐frequency motions are dominated by topographic Rossby waves similar to the results of previous studies of deep currents on the continental rise of the Mid‐Atlantic Bight. Estimated wave parameters show good agreement with the linear topographic Rossby wave theory of Rhines (1970). Inertial oscillations are shown to be coherent over the array (horizontal separations ∼15–20 km). The peak frequency and phase and group velocity estimates are consistent with surface layer generation at a site north of the array. The relative vorticity of the mean currents and the low‐frequency wave motions do not account for the observed shift of the near‐inertial peak to frequencies ∼7% above f. An event of strong near‐bottom inertial currents (amplitudes ∼10 cm s−1) appears to be attributable to the passage of Hurricane Belle (August 9–10, 1976) 24 days earlier, primarily because the vertical travel times are consistent with the estimates of vertical group velocity. Strong ringing inertial currents north of the array (amplitude ∼40 cm s−1), due to Hurricane Belle were observed at the shelf edge (Mayer et al., 1981) with peak frequencies comparable to the near‐inertial frequencies observed at the array on the rise.
Surface front displacement in the Gulf Stream by Hurricane/Tropical Storm Dennis
Authors: Horton Charles W.
Published: February 2008

Using airborne radiation thermometer measurements and air dropped expendable bathythermographs, the near‐surface thermal structure of a section of the Gulf Stream northeast of Cape Hatteras was monitored before and immediately after the passage of Hurricane/Tropical Storm Dennis in August 1981. The passage of Dennis increased the average horizontal separation between the surface and subsurface Gulf Stream fronts from about 1 to 19 km. This increase in separation between the two fronts was apparently caused by wind‐driven cross‐stream advection in the mixed layer.
A field performance test of the Sippican deep aircraft‐deployed expendable bathythermograph
Authors: Bane John M. , Sessions Meredith H.
Published: February 2008

A field test of the performance of the initial design, deep (760 m/2500 ft.) Sippican aircraft‐deployed expendable bathythermograph (AXBT) has been conducted. Thirty‐seven AXBTs were deployed beside a research vessel, which was conducting conductivity, temperature, and depth (CTD) casts to 1000 m. A total of five CTD casts were made. A comparison between the AXBT and CTD data showed that the AXBT's provided temperature profiles with accuracies that depended upon the particular formulae chosen for frequency‐to‐temperature conversion and fall rate. The three sets of formulae used here were the standard Navy formulae, the formulae published by the Sippican Corporation, and a combination of a frequency‐to‐temperature formula published by the Naval Oceanographic Office (NAVOCEANO) and a fall rate determined from data collected during this study. Two of the three methods produced data that appeared to be within the Navy's AXBT accuracy specifications, taking the CTD data as standard. A temperature offset of about 0.4°C was found in the data set using the Sippican formulae, and this puts the temperature accuracy just outside the Navy's specified limits for higher temperatures. The best comparison between AXBT and CTD data was found with the NAVOCEANO formula and our fall rate, which provide a temperature accuracy better than 0.25°C. Our fall rate was quite close to the standard Navy fall rate (less than 2 m difference at 760 m depth), so the use of the latter is suggested. The recommended formulae for the initial design Sippican 760 m AXBT's are as follows: T= −66.8857 + (7.0273 × 10−2)F ‐ (2.1807 × 10−5)F2 + (3.6311 × 10−9)F3, D = 1.52t, where T = temperature in degrees Celsius, F = frequency in hertz, D = depth in meters, and t = elapsed time in seconds. The statistics of the AXBT data set suggest that the precision of the Sippican thermistor is better than 0.06°C.
Comparison of profiling and moored current measurements in the equatorial Pacific
Authors: Freitag H. Paul , Firing Eric
Published: February 2008

Profiling current meter measurements of near‐surface equatorial currents are compared with concurrent moored current meter measurements. Rms differences between the two are less than 15 cm s‐1 when PCM measurements are referenced to 300–500 m and less than 10 cm s−1 when considered as relative velocity. The lack of an absolute reference level was the major contributor to differences in transport per unit width.
Equatorial modes in the eastern Pacific (85°W)
Authors: Behringer D. W.
Published: February 2008

The net isopycnal displacements between early March and early December 1982 is shown for a section traversing the equator at 85°W. This time period includes the onset of the 1982/1983 El Niño. The section is analyzed in terms of both empirical orthogonal functions and dynamical modes derived from linear equatorial wave theory. Only a few functions, whether empirical or dynamical, are needed to describe most of the variance in the section. In particular, functions representing the structures of the Kelvin and first mode Rossby waves associated with the first three baroclinic modes of linear theory, when fitted to the section in a least squares sense, can describe 86% of the variance. These waves may ultimately have been caused by a failure of the trade winds which began in the vicinity of the dateline prior to mid‐June 1982 and subsequently spread eastward.