bluuebunny/crossref_metadata_2025 huggingface dataset:
Low‐frequency wind‐induced sea level oscillations along the east coast of North America
Authors: Noble Marlene , Butman Brad
Published: April 2008

Atmospherically adjusted coastal sea level observations (ASL) and wind measurements at stations along the east coast of North America from Cape Hatteras, North Carolina, to Eddy Point, Nova Scotia, for a 6‐month winter period were used to study the spatial structure of ASL and wind stress on the continental shelf and to determine the low‐frequency response of ASL to wind forcing. ASL and wind stress were coherent over distances of 1300 km for motions with periods between 60 and 600 hours. Northward movement of storm systems and of the associated ASL response was observed for stations north of Cape May, New Jersey. South of Cape May the phase of ASL suggested southward movement of pressure disturbances. Longshore wind accounted for 55% of ASL energy and led ASL by 8–12 hours. Cross‐shore winds were generally not coherent with ASL. In the Middle Atlantic Bight (MAB), sea level response was 17 cm for a 1 dyn cm−2 longshore wind and symmetric in the longshore wind stress directions. In contrast, from Nantucket north, sea level response to longshore wind stress was weaker (9 cm for a 1 dyn cm−2 wind to the northeast). The response for wind to the northeast was twice as large as the response for wind stress toward the southwest. If coastal winds were representative of winds over the shelf, the observations imply that the wind‐driven longshelf geostrophic currents were larger for unit wind stress in the MAB than in the Georges Bank‐Scotian Shelf region. The regional change in ASL response may be due to the large semidiurnal tidal currents which occur in the Georges Bank region or to the rough topography on the Scotian Shelf, which effectively increases bottom friction. The regional change in ASL response suggests a divergence in longshore flow and an onshore flow on the shelf south of Nantucket for winds to the southwest. A low‐frequency longshelf ASL slope was observed in the MAB that was incoherent with longshelf wind stress.
Atmospheric nitrous oxide in the mid‐latitudes of the southern hemisphere
Authors: Roy C. R.
Published: April 2008

Results from the first continuous program for studying atmospheric nitrous oxide (N2O) in the southern hemisphere are presented. Daily measurements at Aspendale, Australia (38.1°S, 145.2°E), yield an average N2O mixing ratio of 340 ppb in dry air for the period October 1976 to May 1978. No significant long‐term trend has been detected. Analysis of air collected at several clean air (marine and rural) locations reveals a significantly lower mixing ratio of 337–338 ppb. The difference is attributed to an urban source of N2O. Results from an extensive air sampling network illustrate the homogeneous distribution of N2O in the troposphere and reveal no variations in mixing ratio which could be attributable to seasonal or synoptic variations. The N2O mixing ratio decreases above the tropopause. Preliminary results of the direct measurement of N2O exhalation from soil are reported. Both the constancy of the N2O mixing ratio in the troposphere and the low exhalation rates from soil suggest a long lifetime for N2O in the atmosphere. This implies small sources and sinks and makes the atmospheric N2O cycle susceptible to anthropogenic inputs. All measurements were made by electron capture gas chromatography with a precision of approximately 1%. The uncertainty in the absolute value of the N2O mixing ratio is 10–15%. The need for accurate and reproducible gas standards and for regular interlaboratory comparisons of standards is discussed.
The sensitivity of an energy balance climate model to variations in the orbital parameters
Authors: Suarez Max J. , Held Isaac M.
Published: April 2008

The responses of a zonally symmetric model of the global energy balance to perturbations in incident solar radiation are analyzed. The model is forced with seasonally varying insolation and incorporates in a simple way the positive feedback due to the high albedo of snow and sea ice. Meridional energy transport due to atmospheric motions is simulated with lateral diffusion of heat. Meridional energy transport by oceanic currents is ignored, as are possible variations in cloudiness. Emphasis is placed on the model's sensitivity to the latitudinal and seasonal redistribution of insolation produced by variations in the obliquity, the eccentricity, and the longitude of perihelion of the earth's orbit. It is found that when albedos are allowed to vary, increased seasonal variation of insolation leads to increased temperature in the northern hemisphere. In all cases considered, the latitudinal extent of perennial snow cover in the northern hemisphere is particularly sensitive to the perturbations, a response suggestive of the large fluctuations of continental glaciers during the Pleistocene. When the model is forced with the orbital variations of the past 150,000 years, its response is qualitatively similar to the geologic record of that period.
A statistical model for groupiness in wind waves
Authors: Hamilton J. , Hui W. H. , Donelan M. A.
Published: April 2008

A simple nonspectral model for wind waves is proposed. It is found that a model based on a single ‘carrier’ wave with random phase shifts between groups reproduces the essential characteristics of the autocorrelation function of real wind waves. It is not purported to be a general wind‐wave model but is used simply to explain the statistical significance of the tail of the correlation function and to obtain good masking functions for the computation of smoothed wave spectra. Engineering applications of such simple wave models are briefly discussed.
The coastal longshore pressure gradient: Temporal variations and driving mechanisms
Authors: Chase R. R. P.
Published: April 2008

Along the northern coastal boundary of the Mid‐Atlantic Bight, synthetic subsurface pressure records derived from 1975 tide gage and airway weather observations are examined for fluctuations having monthly time scales. Additional calculations are performed to determine the factors controlling variance in these pressure data. Similar analyses are applied to the longshore gradient in synthetic subsurface pressure. Results of the study indicate that synthetic subsurface pressures are controlled by three mechanisms, two each at either end of the coastal segment. Fluctuations in Gulf Stream position have a significant effect on monthly mean pressures, which are uniform along the coast. At the western end of the coastal segment, east‐west winds are also important, while changes in water density contribute significantly to subsurface pressure variance at the eastern end. Coastal steric differences are found to be a minor contributor to monthly fluctuations of longshore pressure gradient, while the coastal mean east‐west winds effect a linear response in the gradient. Using this relationship and upon removal of geodetic leveling errors, the annual mean longshore sea surface slope is calculated to be 1.6×10−7, forming a westward pressure gradient along the northern boundary of the Mid‐Atlantic Bight.
The effect of wind on the microwave emission from the ocean's surface at 37 GHz
Authors: Wilheit Thomas T.
Published: April 2008

The microwave brightness temperature measurements from the electrically scanned microwave radiometer (frequency = 37 GHz) are compared with oceanic wind measurements from data buoys. It is shown that the brightness temperature can be manipulated to yield a measure of the surface roughening, which can be very well accounted for by a simple geometric optics model. The data of Hollinger (1971) at 1.4, 8,36, and 19.34 GHz were similarly manipulated and shown to require a surface with less slope variance than that predicted by the Cox and Munk (1955) optical measurements. It is also shown that the surface may be treated as isotropic to an accuracy equivalent to the roughening produced by a 2‐m/s wind speed increment.
Energetics of breaking waves within the surf zone
Authors: Thornton Edward B.
Published: April 2008

Surface elevations and velocities were measured for a variety of breaking wave conditions including collapsing, plunging, and spilling breakers. Turbulent and wave‐induced velocity components are separated by associating the wave‐induced velocities with contribution coherent with the surface. Most of the measurements were made in the lower half of the water column and are indicative of conditions in this region. The average velocity intensity for all experiments was 85% wave induced, indicating that the kinetic energy is primarily wave induced. Remarkably little difference was found between collapsing, plunging, and spilling breakers in terms of percent wave‐induced velocity intensity. Breaking waves can be characterized as highly nonlinear with strong wave‐wave interactions resulting in energy being transferred away from the primary wave frequency, resulting in a saturation region at higher frequencies. Similarity arguments assuming kinematic instability with phase speed the only relevant parameter suggest a −3 slope for the log‐log frequency spectrum of both the surface and horizontal velocities in shallow water. The surface elevation spectra of collapsing and plunging breakers have a slope more closely approximated by a −7/3 slope, indicating the possible importance of surface tension in the breaking processes; the velocity spectra show a −3 slope. The saturation region for spilling breakers surface elevation spectra varied from −3 at lower frequencies to −5 at highest frequencies.
Intrusive density flows in the lower troposphere: A source of atmospheric solitons
Authors: Christie D. R. , Muirhead K. J. , Hales A. L.
Published: April 2008

This paper is concerned with the properties of complex propagating nonlinear tropospheric disturbances observed near Tennant Creek in the arid interior of the Northern Territory of Australia. Many of these unusual atmospheric disturbances resemble the well‐known internal undular surges observed in the oceans and in inland stratified bodies of water. A description is presented of a wide variety of observations of solitary‐wave‐dominated evolving density intrusions, and it is shown that many of the features of these unique disturbances are in qualitative agreement with the predictions of nonlinear dispersive wave theory. In particular, it is shown that the evolutionary behavior of these disturbances is governed by the Benjamin‐Ono equation and that intrusive motions of this type play an important role in the generation of boundary layer solitary atmospheric waves. Existing experimental evidence indicates that these disturbances originate primarily in the interaction of katabatic flows, propagating sea breeze vortices, and ‘morning glory’ phenomena with the stably stratified nocturnal radiation inversion.
Atmospheric feedback in a Coupled Ocean‐Atmosphere Model
Authors: Wells N. C. , Puri K.
Published: April 2008

Results are presented for the atmospheric response in a coupled mixed layer ocean‐atmosphere model of the southern hemisphere. The model is integrated for a period of 72 days for fixed January radiation conditions. The main feature of the model is a warming trend which occurs throughout the period in both the ocean and the atmosphere. This is shown to be due to the excess solar radiation at all latitudes, which causes an increase in sea surface temperature (SST), with the maximum increase of 3°K occurring between 30°S and 40°S. As a consequence, the evaporation is increased in middle latitudes, and the resultant increased water vapor is transported to the equatorial region and higher latitudes, where condensation causes a warming of the troposphere. It is further shown that changes in the meridional temperature gradient occur which result in a poleward movement of the jet stream. These features of the model are shown to be similar to the observed seasonal change during the southern hemisphere summer, particularly in middle latitudes. An unexpected feature of the model is that the changes in atmospheric circulation result in changes in surface heat fluxes and wind stress which produce a further increase in hemispheric SST. The implications of this positive feedback mechanism on the development of SST anomalies are briefly discussed.
Effect of electrical forces on charge separation caused by the combined effect of the precipitative and convective mechanisms in thunderclouds
Authors: Kamra A. K.
Published: April 2008

The maximum electric field that can be generated by the combined effect of precipitative and convective mechanisms in thunderclouds has been calculated. The derivation includes leakage currents produced by the electrical forces acting on precipitation and cloud particles. It is found that although these leakage currents significantly influence the charge separation process, very high electric fields, generally exceeding breakdown values, can be generated under moderately convective conditions. Dependence of the maximum electric field on updraught velocity, precipitation intensity, liquid water content, particle charges, etc., has been evaluated. The results demonstrate that while in nonconvective or weakly convective clouds, higher values of precipitation intensity can generate higher electric fields, in convective clouds with updraughts of about 0.5 m/s or higher, higher precipitation intensities saturate the electric field at lower values. Further, larger electrical charges on the precipitation and cloud particles generally lower the maximum electric field that can be generated. Limitations and significance of the results have been discussed in view of the simplified assumptions and available observations.
Analysis of monoterpene hydrocarbons in rural atmospheres
Authors: Holdern M. W. , Westberg H. H. , Zimmerman P. R.
Published: April 2008

Gas chromatographic/mass spectrometric analysis of monoterpenes from a rural forested site in the northwestern United States is described. Use of a glass capillary column provided excellent resolution of the hydrocarbons. Increased sensitivity and specificity of the mass spectrometer detector over the flame ionization detector were demonstrated for trace (parts per trillion) atmospheric hydrocarbons. As little as 10 ppt of compound was detectable in 100‐cc air samples. Two analytical methods (cryogenic and solid adsorbent‐Tenax‐GC) were used in the collection of ambient air. Analytical results from the two techniques compared very well. Rural concentrations of the monoterpenes varied considerably depending upon location within the forest canopy. The concentration of individual species never exceeded 1 ppb of compound during a 10‐month sampling period. The monoterpene total for all samples fell in the range of 0.5‐to 16‐ppb compound for C10 terpene.
A moored instrument for vertical temperature gradients
Authors: Dean Jerome P.
Published: April 2008

Vector averaging current meters have been modified to measure the temperature gradient in addition to current and absolute temperature. The modified instrument measures the temperature difference between sensors spaced vertically 1.74 m apart (or closer) using thermistors in a Wheatstone bridge circuit. Calibrations provide corrections for drift and static offset resulting in temperature gradient measurements accurate to about 0.5 m °C/m. Originally developed to infer vertical velocities, the instrument has also been successfully used to study mixed layer motions and thickness variations and to investigate temperature fine structure.
Effect of surface roughness on the microwave emission from soils
Authors: Choudhury B. J. , Schmugge T. J. , Chang A. , Newton R. W.
Published: April 2008

The effect of surface roughness on the brightness temperature of a moist terrain has been studied through the modification of Fresnel reflection coefficient and using the radiative transfer equation. The modification involves introduction of a single parameter to characterize the roughness. It is shown that this parameter depends on both the surface height variance and the horizontal scale of the roughness. Model calculations are in good quantitative agreement with the observed dependence of the brightness temperature on the moisture content in the surface layer. Data from truck mounted and airborne radiometers are presented for comparison. The results indicate that the roughness effects are great for wet soils where the difference between smooth and rough surfaces can be as great as 50K.
Numerical case studies for oceanic thermal anomalies with a dynamic model
Authors: Huang Joseph Chi Kan
Published: April 2008

Numerical investigations to identify the physical processes responsible for the generation, evolution, and dissipation of oceanic thermal anomalies (OTA) were carried out using the numerical dynamic model of the North Pacific Experiment (Norpax). The Norpax model is based on time‐integrations of the finite‐difference forms of the primitive equations. It possesses an actual coastal configuration and 10 vertical layers, with a constant maximum depth of 4 km. The horizontal grid spacing, both longitudinal and latitudinal, is 2.5°. The seasonally varying model climatology is generated by integrating the model over 80 years of simulations under the climatological atmospheric forcing, of which the first 60 years are the long‐term annual mean conditions and the last 20 years vary with the seasonal cycle. Large‐scale features of the model ocean climatology compare favorably with observed large‐scale motions and structure in the North Pacific Ocean. The model is used for oceanic thermal anomaly studies. Two simulated cases are presented: one demonstrates the generation and evolution of OTA's under anomalous atmospheric wind forcing of winter 1949–1950, and the other portrays the evolution and dissipation of the OTA's under climatological atmospheric conditions in winter 1971–1972. The resulting model simulations are compared with observational data to examine to what extent change of the oceanic thermal structure is accounted for by the anomalous wind forcing and how much by the internal adjustments in the ocean. The model indicates that OTA's are generated by anomalous atmospheric winds and that thermal advection, both horizontal and vertical, plays the most important role in the generation. During winter, anomalous wind‐induced upwelling has more influence on a cold anomaly in the tropic and subtropic regions than anomalous downwelling has on a warm anomaly in the subarctic region under a weak stable state. The behavior of an initial anomaly under climatological conditions is closely related to large‐scale features, such as the circulation pattern and the thermal gradient in the ocean, and is also subject to modifications due to the presence of OTA's. Aside from limitations of the present course‐grid model, most discrepancies found between the simulated and observed anomalies can generally be attributed to the lack of reliable and accurate meteorological and subsurface data. As better oceanic and atmospheric data become available, further studies of anomaly dynamics through numerical experiments will lead to understanding anomalous heat distributions in the upper layers of the ocean and hence to better ocean predictions.
A Hindcast study of extreme wave conditions in the North Sea
Authors: Ewing J. A. , Weare T. J. , Worthington B. A.
Published: April 2008

A deep water hybrid parametrical wave model, first discussed in the Joint North Sea Wave Project (Jonswap), has been used to hindcast long‐term wave height statistics in the northern North Sea. The wave model was validated against wave measurements at two stations near the British Isles. A representative subset of the vigorous gales over the period 1966–1976 was used as input to the model. Extreme value significant wave height statistics were estimated from the independent storm events, taking into account possible secular changes of the wind field extremes. The results are compared with wave height estimates derived in two other studies.
Anisotropic properties of sea ice in the 50‐ to 150‐MHz range
Authors: Kovacs A. , Morey R. M.
Published: April 2008

Results of impulse radar studies of sea ice near Prudhoe Bay, Alaska, show that where there is a preferred current direction under the ice cover, the crystal structure of the ice becomes highly ordered. This includes a crystal structure with a preferred horizontal c axis that is oriented parallel with the local current. The radar studies show that this structure behaves as an anisotropic dielectric. The result is that when electromagnetic energy is radiated from a dipole antenna in which the E field is oriented perpendicular with the c axis azimuth, no bottom reflection is detected. It was also found that the frequency dispersion of anisotropic sea ice varies in the horizontal plane. This is demonstrated by the center frequency of the reflected signal spectrum, which is maximum in the preferred c axis direction and minimum perpendicular to it. In addition, it was found that the frequency dispersion is related to the average bulk brine volume of the ice but that the bulk dielectric constant of the ice, as determined from impulse travel time, shows little correlation with the coefficient of anisotropy.
The temporal structure of the HF and VHF radiation Produced by intracloud lightning discharges
Authors: Krider E. P. , Weidman C. D. , LeVine D. M.
Published: April 2008

Measurements of the radio frequency emissions produced by large‐amplitude intracloud lightning impulses are presented in correlation with the associated electric radiation field. The RF radiation starts at almost the same time as the field, and the peak RF tends to occur during the initial half cycle of the field pulse. This temporal behavior is in marked contrast to that exhibited by the RF during the return stroke portions of cloud‐to‐ground flashes.
Characterization of lightning return stroke electric and magnetic fields from simultaneous two‐station measurements
Authors: Lin Y. T. , Uman M. A. , Tiller J. A. , Brantley R. D. , Beasley W. H. , Krider E. P. , Weidman C. D.
Published: April 2008

We present a characterization of Florida lightning return stroke electric and magnetic fields derived from simultaneous measurements of the fields at two separate stations, one station being within 15 km of the lightning, the other at either about 50 or 200 km from the lightning. We give (1) examples of correlated wave forms, (2) typical first and subsequent stroke wave forms over the distance range 1.0–200 km, and (3) the following statistical data from which the typical wave forms were derived: for electric field, rise time, initial peak value, ramp starting time, ramp slope, value at 170 μs, ratio of value at 170 μs to initial peak, zero‐crossing time for 50 and 200 km wave forms; for magnetic fields, time of hump following initial peak, ratio of hump value to initial peak value, zero‐crossing time for 50 and 200 km wave forms. Return stroke electric and magnetic field characteristics appear to be independent of location in Florida.
Simultaneous measurement of atmospheric CH2O, O3, and NO2 by differential optical absorption
Authors: Platt U. , Perner D. , Pätz H. W.
Published: April 2008

Formaldehyde mixing ratios are reported for rural areas around Jülich and for maritime air at the north coast of Germany. The measurements were made using a ground‐based UV‐optical absorption technique which allowed the simultaneous determination of CH2O, NO2, and O3 with detection limits of 0.1, 0.1, and 1 ppb, respectively. In Jülich, which may be regarded as typical for central European background atmosphere, mixing ratios varied from 0.1 to 6.5 ppb from May through October 1978. In maritime air under conditions when photochemical equilibrium was expected, formaldehyde concentrations of 0.2 ppb were observed, which can be accounted for by photochemical oxidation of methane alone. However, the high concentrations of formaldehyde found at Jülich indicate other sources of formaldehyde.
Seasonal patterns of onshore/offshore sediment movement
Authors: Aubrey David G.
Published: April 2008

Measurements of beach profiles from southern California spanning a 5‐year period have been examined for temporal changes in beach configuration. On an annual time scale the data suggest two distinct seasonal pivotal points separating eroding and accreting regions. Empirical eigenfunction analysis of combined onshore and offshore profiles shows a pivotal point for seasonal onshore/offshore sediment movement at a depth of 2–3 m below mean sea level and suggests another at a 6‐m depth. Analysis of accurate reference rod measurements at 4‐, 6‐, 10‐, 14‐, and 20‐m depths supports the presence of the 6‐m pivotal point. A simple model of depth‐dependent seasonal sand movement suggests that during initial winter storms, sand is eroded from both the foreshore and from depths of 6–10 m and is deposited in water depths from 2 to 6 m. During less energetic periods, sediment migrates both shoreward (to the beach face) and seaward (to depths of 10 m) from its winter site of deposition (water depths from 2–6 m). This observation of depth‐dependent motion contradicts the simple single pivotal point model previously suggested for nearshore seasonal onshore/offshore sediment motion and emphasizes the complexity of nearshore sediment transport. A sediment budget for seasonal onshore/offshore transport, based on the dual pivotal point model, consists of exchanges of 85 m3/m of beach length across the 3‐m pivotal point and 15 m3/m across the 6‐m pivotal point. Over a longer time scale (i.e., the entire 5 years of study) the beaches showed no net erosion or accretion, suggesting that this limited coastal region is stable over these short time scales.
Characteristics of the fortnightly shelf wave along the Ghana Coast
Authors: Houghton Robert W.
Published: April 2008

Data from the Ghana shelf has been analyzed to elucidate further the properties of the fortnightly wave that has been observed propagating westward along the Gulf of Guinea coast. Harmonic analysis reveals a highly coherent signal with a large quality factor Q and signal to noise ratio at the luni‐solar synodic Msƒ fortnightly tidal frequency. The energy is trapped below the thermocline, suggestive of a topographic shelf wave. The wave is not confined to the coastal upwelling season but is manifest in the surface temperature only when the thermocline rises to the surface. Since the Rossby radius of deformation is greater than the shelf width, the model by Wang and Mooers [1976] of a hybrid topographic shelf wave modified by stratification is probably the most appropriate. The coherence and precise frequency of the wave corroborates with the suggestion by Picaut and Verstraete [1979] that the wave is induced by the Msƒ tide, enhanced by a nonlinear M2‐S2 interaction. The eastern Gulf of Guinea is the most likely source region.
A catalog of perturbing influences on stratospheric ozone, 1955–1975
Authors: Bauer Ernest
Published: April 2008

There exist worldwide data on the total burden of atmospheric ozone since about 1955, and for comparison of these data with calculations using two‐dimensional radiative/chemical/dynamics computer codes, a list is needed and is here presented of all major time‐varying perturbations that have been suggested over the time frame 1955–1975. Detailed consideration is given to the following: variations in solar UV radiation with sunspot cycle, atmospheric nuclear explosions, halocarbons, major volcanic eruptions, galactic cosmic rays, and solar proton events. For material injected directly into the stratosphere, the time‐, altitude‐, and latitude‐dependent source strengths are listed, while for ground‐based sources the time‐ and latitude‐dependent atmospheric emission rates are given. Some other factors that may affect the long‐term behavior of stratospheric ozone but that cannot yet be modeled quantitatively are also listed.
Atmospheric implications of studies of Central American volcanic eruption clouds
Authors: Cadle R. D. , Lazrus A. L. , Huebert B. J. , Heidt L. E. , Rose W. I. , Woods D. C. , Chuan R. L. , Stoiber R. E. , Smith D. B. , Zielinski R. A.
Published: April 2008

During February 1978 a group of scientists from the National Center for Atmospheric Research, several colleges and universities, the U.S. Geological Survey, and NASA used a specially equipped Beech Queen Air aircraft to make 11 sampling flights in Guatemala through the eruption clouds from the volcanoes Pacaya, Fuego, and Santiguito. Measurements were made of SO42−, SO2, HCl, HF, and 11 cations that were in water‐soluble form, on samples collected by a specially designed filter pack. Particle size distributions were obtained with a piezoelectric cascade impactor, and the particles were identified by energy dispersive X ray analysis. Evacuated canisters were flown to obtain samples for gas Chromatographic analysis. Some of the conclusions reached are that since most of the sulfur was found to be in the form of SO2, the H2SO4 droplets resulting from major explosive eruptions must largely result from the reaction of SO2 with OH, at the same time depleting the atmosphere of OH; the volume concentration ratio [SO2]/[HCl] always somewhat exceeded unity; and the amount of fine ash remaining in the stratosphere for long periods of time may depend on the crystallinity of the magma. Correlation spectrometry showed that each volcano was emitting 300–1500 metric tons of SO2 per day.
Seasonal and interannual variations in total ozone Revealed by the Nimbus 4 Backscattered Ultraviolet Experiment
Authors: Hilsenrath Ernest , Heath Donald F. , Schlesinger Barry M.
Published: April 2008

The first 2 years of backscattered ultraviolet (BUV) ozone data from the Nimbus 4 spacecraft have been processed to a more refined level. The seasonal variations of total ozone for the period April 1970 to April 1972 are described using daily means for 10° latitude zones and a time‐latitude cross section. In addition, the BUV data are compared with analyzed Dobson data and with infrared interferometer spectrometer data also obtained from the Nimbus 4 spacecraft. A harmonic analysis was performed on the daily zonal means. Amplitudes, days of peak ozone values, and percentage of variance have been computed for the annual and semiannual waves and for higher harmonics of an annual period for the 2 years. Asymmetries are found in the annual waves in the two hemispheres, with a subtle interannual difference which may be due to changes in the general circulation. A significant semiannual component is detected in the tropics for the first year. This component appears to result from influences of the annual waves in the two hemispheres. A search for shorter periods using the harmonic analysis revealed no periodicity whose amplitude was higher than the noise level.
Mercury in southern New England coastal rains
Authors: Fogg Thomas R. , Fitzgerald William F.
Published: April 2008

Mercury analyses were performed on nine different rain samples collected from Connecticut and Cape Cod (Massachusetts) coastal locations. Concentrations of Hg averaged 10±5 ng l−1 for 29 determinations. Total washout of Hg from the atmosphere was not observed, suggesting that the quantity of Hg in rain may depend on the simple solution of various volatile species of Hg according to Henry's law. Existing global models use concentrations of 30–80 ng l−1 and appear to overestimate the rainfall Hg flux to the ocean.
The spring transition in currents over the Oregon Continental Shelf
Authors: Huyer A. , Sobey E. J. C. , Smith R. L.
Published: April 2008

Current meter moorings maintained over the Oregon continental shelf in 1973 and 1975 clearly show the difference between winter and spring oceanographic regimes and the rapid transition between the regimes. In winter the mean alongshore current is northward at all depths and strongest near shore; there is no mean vertical shear, no mean offshore density gradients, and mean sea level is high. In spring the mean alongshore current is weak near the bottom and strongly southward at the surface with a maximum over the mid‐shelf; the strong vertical shear is balanced by strong offshore density gradients, and mean sea level is low. In both 1973 and 1975 the transition between these regimes occurs within about a week during a strong southward wind event. In many respects the transition event does not differ significantly from previous southward wind events, but the lateral density gradients established during the transition event exceed those of earlier events. The transition appears to be the result of a large cumulative offshore Ekman transport caused by local wind stress rather than by propagation of effects generated elsewhere. The lateral density gradients and the vertical shear established during the transition event subsequently persist, even during northward wind events with moderate onshore Ekman transport.
Acoustic remote sensing of high‐frequency internal waves
Authors: Kaye G. T.
Published: April 2008

A method is presented to extract internal wave information from acoustic reverberation data. The method is a tracking scheme which estimates the mean vertical motion of acoustic scatterers and infers the internal oscillations. Good coherence is found between isotherm depth histories and the tracking output for frequencies of 0.5–10 cph, especially in the octave of 3–6 cph.
Trace gas concentrations, intertropical convergence, atmospheric fronts, and ocean currents in the tropical Pacific
Authors: Wilkniss P. E. , Rodgers E. B. , Swinnerton J. W. , Larson R. E. , Lamontagne R. A.
Published: April 2008

Shipboard measurements of atmospheric 222Rn, CO, and CH4 and of dissolved CO in surface waters have been carried out in the equatorial Pacific on a cruise from Ecuador to Hawaii, Tahiti and Panama in March and April of 1974, and during transit from Los Angeles to Antarctica in November and December of 1972. Trace gas results, combined with conventional meteorological data and with satellite images from Nimbus 5 and the defense meteorological satellite project (DMSP), have provided descriptions of the intertropical convergence zones (ITCZ) near 04°N, 102°W and 03°N, 154°W in March of 1974, near 04°N, 86°W in April of 1974, and near 05°N, 139°W in November of 1972. In all cases the ITCZ seems to be located north of the south equatorial current (SEC) as shown by dissolved CO peaks in surface waters. In April of 1974 a ‘second’ ITCZ was observed near 01°S, 102°W just south of the SEC. A stationary front near Hawaii (20°N, 147°W) in March of 1974 was investigated. The ITCZ was marked by light shifting winds near a zone of heavy cloud cover and precipitation. In the eastern Tropical Pacific atmospheric 222Rn increases distinctly north of the ITCZ and thus serves as an indicator for the ITCZ. CO and CH4 do not always increase coincident with atmospheric 222Rn The atmospheric features of the stationary front near Hawaii are in many ways similar to those observed for the ITCZ. The front is marked by cloud cover, precipitation zone and light shifting winds. 222Rn CO and CH4 increase significantly behind the front in subsiding air which was traced back to the Asian continent. The variation of atmospheric 222Rn, CO and CH4 with time and geographical area over the equatorial Pacific seems to be a consequence of seasonal variations of the trade wind field and long range transport to the central Pacific from Asia and to the eastern equatorial Pacific from North and Central America.
Aircraft search for millimeter‐wavelength emission by stratospheric ClO
Authors: Waters J. W. , Gustincic J. J. , Kakar R. K. , Roscoe H. K. , Swanson P. N. , Phillips T. G. , De Graauw T. , Kerr A. R. , Mattauch R. J.
Published: April 2008

Three millimeter‐wavelength transitions of ClO were searched for in the stratospheric emission spectrum during May–August 1977 using aircraft‐based instruments. The measurements indicate that if stratospheric ClO has a vertical distribution of the form predicted by present photochemical models, then the ClO volume mixing ratio at the profile peak did not exceed 10−9at the time and place of the measurements. The observed spectra suggest the presence of ClO in the stratosphere but do not provide a definitive detection.
Carbon monoxide evolution from Arctic surfaces during spring thaw
Authors: Gosink T. A. , Kelley J. J.
Published: April 2008

Thawing tundra soils and newly rotting sea ice bubbles are rich in carbon monoxide (5–100 ppm) for a few weeks in May–June. Recent air samples in the vicinity of Barrow, Alaska, showed dramatic increase near the coast and overland. Several hundred kilometers out over winter sea ice the atmosphere concentration of CO was 0.02–0.06 ppm. Near the coast over rotting sea ice the concentration was 0.09 ppm.Inland, atmospheric carbon monoxide rose to a 0.2 ppm. Short term enrichments of carbon monoxide at the tundra and sea ice surfaces have been observed in the past.
Eddies off the Somali Coast during the southwest monsoon
Authors: Bruce J. G.
Published: April 2008

The development and decay of the large eddy in the northern Somali Basin and its smaller associated eddies each southwest monsoon in the northwestern Indian Ocean has been monitored for four consecutive years by a time series of temperature sections obtained along the tanker sea lane across the Somali Basin. The evidence suggests that the large eddy first forms between 4°N to 12°N during late May and tends to remain approximately in this location throughout the entire southwest monsoon.
Submarine slide‐generated water waves in Kitimat Inlet, British Columbia
Authors: Murty T. S.
Published: April 2008

A major submarine slide occurred on April 27, 1975, in Kitimat Inlet in the Douglas Channel system on the west coast of Canada. Following this slide at least two water waves were observed, and it was estimated that the range (crest plus trough) of the first wave could have been 8.2 m. Two simple theories have been used here to estimate the wave height. By considering the uncertainties both in the observed data as well as in the calculated wave height, there is reasonable agreement.
Turbulence measurements in the boundary layer over a sand wave field
Authors: McLean Stephen R. , Smith J. Dungan
Published: April 2008

To assist in elucidating the turbulent structure of flow over regular sets of bed forms, data procured with small mechanical current meters above 2 m high 96 m long sand waves in the Columbia River are analyzed. The high‐frequency resolution of the flow sensors and the half hour records that were collected with them are shown to be sufficient to yield reliable Reynolds stresses. In addition, an expression from which the sampling error in Reynolds shear stresses can be estimated from the sampling frequency, the local flow speed, and the distance from the boundary is presented. Although the κ−5/3 region of the energy spectrum was found, the conditions for isotropy were not satisfied anywhere within the measured band. Spatial structure of the Reynolds stress components was found to be complicated in character but explicable in basic fluid mechanical terms. Owing to the near boundary effects of form drag induced by the sand waves, the spatially averaged shear stress increased from 20 dyn/cm2 at 35 cm to 40 dyn/cm2 at 100 cm. Furthermore, the Reynolds shear stress was found to vary with the structure of the variance of the vertical velocity component rather than with that of turbulent kinetic energy as assumed in the simple closure models that have been used so far in theories for flow over such bed forms. The data also were examined for flow intermittency, and the results of Gordon and Witting [1977] were not confirmed.
Water column anomalies in dissolved silica over opaline Pelagic sediments and the origin of the deep silica maximum
Authors: Edmond J. M. , Jacobs S. S. , Gordon A. L. , Mantyla A. W. , Weiss R. F.
Published: April 2008

Recent estimates based on pore water studies and mass balance considerations put the average flux of dissolved silica from the sediments into the deep water at about 3 μmol cm−2 yr−1. This flux, if mixed uniformly in a bottom layer 100 m thick, results in an anomaly increment of 0.3 μmol kg−1 yr−1. In basins of restricted circulation containing opaline sediments the residence time of the bottom waters should be long enough that the resulting anomaly be easily resolvable using existing data. Examination of the many hundreds of detailed, precise silica profiles presently available in unpublished reports shows that this is indeed the case. The largest effects (∼50 μmol/kg) are seen in the Weddell‐Enderby Basin. Intermediate anomalies (∼20 μmol/kg) are prevalent in the northern Indian Ocean. Lesser features (∼10 μmol/kg) are clearly discernable in the other antarctic basins and in the north Pacific. No anomalies are observed over the equatorial Pacific and Indian bands of opaline deposits, even in the basins east of the East Pacific Rise or in the Central Basin of the Indian Ocean. The flux of dissolved silica from the sea floor is generally unaccompanied by any resolvable oxygen consumption, indicating that relatively minor amounts of organic material reach the sediments in these regions. However, in the north Indian Ocean there are pronounced effects on all the nutrients, oxygen, and alkalinity, with regeneration approximating the Redfield prediction. In the northern Indian Ocean and the extreme northeast Pacific (northeast of 45°N, 160°W) the silica profiles increase to the bottom. This is a strong indication that the deep silica maximum observed over much of these oceans may have a large advective component, the feature itself being induced by the northward flow of the underlying low‐silica bottom waters. In the Indian Ocean the data coverage is sufficient to demonstrate unequivocally the dominance of this effect.
New precipitation maps for the North Atlantic and North Pacific oceans
Authors: Reed R. K. , Elliott W. P.
Published: April 2008

Oceanic precipitation intensity values derived in a previous study were combined with precipitation frequency data in the recently revised marine climatic altases to prepare new annual and seasonal precipitation maps for the North Atlantic and North Pacific oceans. The greatest precipitation over both oceans occurs in the eastern and central tropical regions. A distinct minimum is present across both oceans in the subtropical regions, being most marked along the eastern margins. Secondary maxima are present over the northern regions, where considerable snow falls in winter. The principal seasonal changes are an increase in size and northward migration of the subtropical dry zone from winter to summer as well as reduced magnitude and gradients of precipitation to the north in summer. The tropical Pacific shows a remarkably stable distribution during the year, but the zone of maximum rainfall in the tropical Atlantic undergoes considerable variation in location. The new maps show generally less precipitation in extratropical regions than earlier ones, although in the tropics they give values between those of the widely varying previous maps.
Turbidity of the atmosphere determined from satellite: Calculation of optimum viewing geometry
Authors: Koepke P. , Quenzel H.
Published: April 2008

By numerical modeling, the variability of the upward emerging spectral radiance is investigated due to the variability of the optically acting atmospheric constituents (no clouds) and due to the state of the earth's surface, in particular of wind‐ruffled oceans. With the objective of determining the atmospheric turbidity (aerosol optical depth) from radiances at only one wavelength, those geometrical configurations between incoming and outgoing radiation are probed, where the variability of the radiance due to the variability of the perturbing optical parameters is minimal. This has been done for maritime aerosols and Sahara dust. It is found that with these aerosol types it is possible to determine the turbidity with an accuracy of better than ±25% within cloud‐free areas over oceans, if the limited measurement accuracy of the radiometers is not taken into account.
Effect of a major warming upon stratospheric NO2
Authors: Noxon J. F. , Marovich E. , Norton R. B.
Published: April 2008

In late February 1979 a stratospheric warming occurred during which the winter polar vortex near 10 mbar split into two smaller vortices situated on opposite sides of the north pole. Measurements of stratospheric NO2 over North America showed a very low NO2 abundance (4×1014 cm−2) near the center of one of the new vortices at ∼50°N, suggesting that polar air had been carried to this location and had maintained its high‐latitude partitioning of odd nitrogen for up to a week at lower latitude. The ‘missing’ odd nitrogen near the center of the dsiplaced vortex must have been stored as a photolytically stable species, presumably HNO3. Colorado remained near the outer edge of the new vortex and had higher NO2 (∼4×1015 cm−2) than normal. The displaced vortex thus carried with it a radial gradient in stratospheric NO2 even larger than that known to be associated with the normal undisplaced winter polar vortex.
The multiparameter remote measurement of rainfall
Authors: Atlas David , Ulbrich Carlton W. , Meneghini Robert
Published: April 2008

This paper is a critical survey of the measurement of rainfall by remote sensors. It is shown that single‐parameter radar rainfall measurements are limited because both reflectivity and rain rate are dependent on at least two parameters of the drop size distribution, viz., representative raindrop size and number concentration. Simulations are presented which use experimental raindrop size spectra and show the improvement in accuracy attainable through the use of combinations of two and three remote measurables. The spectrum of remote measurables is then reviewed. These include path integrated techniques of radiometry and of microwave and optical attenuation. A carefully designed short‐path microwave attenuation experiment which employs these techniques is sufficiently persuasive to show that the disappointing results achieved in many others was due largely to a combination of rain sampling problems and vertical air motions between the path and the gages. Other experiments reviewed show that when paths are colinear, attenuation deduced from radar and radiometry is in good agreement with that measured directly. Several dual‐wavelength radar methods are described which were aimed at improved measurements in small range increments but have produced generally disappointing results. However, when the total path attenuation estimated in this way, or by radiometry, is used as a constraint on the retrieval of rain profiles from the radar, the results are more promising. Selected experiments involving combinations of two or more of the three measurables, radar reflectivity Z, attenuation, and/or radiometry, show considerable promise when adequate account is taken of the sampling and air motion problems. The best results in gate‐by‐gate measurements have been achieved with dual polarization or differential reflectivity (ZDR). However, even these are subject to potentially large errors when the rainfall does not behave according to a priori assumptions embodied in the technique. An accompanying paper in this issue shows that the use of a third remote parameter in addition to Z and ZDR offers great promise. With a growing appreciation of the needs and the capabilities of the various techniques, the future of highly improved remote rainfall measurements seems bright.
A review of the application of multiple‐parameter radar measurement of precipitation
Authors: Hall Martin P. M.
Published: April 2008

Multiple‐parameter radars have now been developed to the point at which they are being used, usually by radio scientists (but not necessarily so), to provide data for the community not primarily committed to radio science (e.g., those concerned with radio engineering, meteorology, hydrology, or aerospace). At the same time, the full potential of such radars is still being explored. Most progress in these applications has been in providing data from which to model conditions on radio paths, but their use for examining the spatial distribution of various hydrometeor forms is no less promising, and, indeed, the two are closely related. This paper examines various practical applications to which multiple‐parameter radars are being put.