bluuebunny/crossref_metadata_2025 huggingface dataset:
Tropical‐extratropical connection in the Atlantic atmosphere‐ocean variability
Authors: Watanabe Masahiro , Kimoto Masahide
Published: December 2003

A question how sea surface temperature (SST) fluctuations in the tropical Atlantic affect the North Atlantic atmosphere‐ocean system is addressed using an atmospheric general circulation model coupled to a 50‐m‐deep slab ocean (MGCM), and a linear baroclinic model. A comparison of a 60‐yr integration, in which the tropical SSTs are prescribed to observations (TOGA‐ML), with the control MGCM run shows that the tropical SST variations selectively enhance variance of the North Atlantic Oscillation (NAO) by about 80%. This is partly due to extratropical height anomalies associated with two dominant modes, monopole and dipole, of tropical Atlantic SST variability because they both have a projection on to the NAO in the TOGA‐ML run. The simulated midlatitude height anomalies accompany characteristic SST anomaly patterns beneath, and they are consistent with observations. Analyses of steady linear responses to the heating in the tropical Atlantic and transient eddy feedback in midlatitude reveal that the substantial part of height anomalies is generated by the latter rather than the former. The anomalous eddy forcing is, however, organized not only by the heating in the tropical Atlantic but also by the tropical Pacific SST variations through the teleconnection over North America. It is suggested that the tropical Atlantic SST variability does affect the North Atlantic atmosphere and ocean, but the dynamical connection is tenuous in comparison with the Pacific.
A reconstruction of total solar irradiance since 1700
Authors: Solanki S. K. , Fligge M.
Published: December 2003

The irradiance of the Sun is reconstructed from 1700 to the present, whereby the contributions of active regions and the quiet Sun are modelled separately. A method is proposed which allows the contribution of active‐region faculae and sunspots to irradiance changes to be isolated even when only a single proxy of solar activity, such as sunspot relative number, Rz, is available. The resulting reconstruction explicitly takes the non‐linear relationship between Rz and irradiance variations into account. Nevertheless, due to the decreasing accuracy of the solar proxy data the accuracy of the reconstruction decreases at earlier epochs. The main uncertainty, however, lies in the reconstruction of the quiet‐sun irradiance variations.
Poleward‐displaced electron precipitation from lightning‐generated oblique whistlers
Authors: Lauben D. S. , Inan U. S. , Bell T. F.
Published: December 2003

New simulation results show that obliquely‐propagating lightning‐generated whistlers which fill vast volumes of the magnetosphere readily induce significant energetic electron precipitation over large regions of the ionosphere, depositing appreciable energy flux to the upper atmosphere at locations substantially poleward of the lightning source. These results provide a new interpretation for the observed spatial relationships between lightning discharges and subsequently disturbed ionospheric regions inferred from subionospheric signal perturbations (i.e. Trimpi events) reported in several lightning‐induced electron precipitation (LEP) studies.
The GPS strain rate field in the Aegean Sea and western Anatolia
Authors: Kahle Hans‐Gert , Cocard Marc , Peter Yannick , Geiger Alain , Reilinger Robert , McClusky Simon , King Robert , Barka Aykut , Veis George
Published: December 2003

The GPS velocity field of the Aegean Sea and western Anatolia is used to determine crustal deformation strain rates for the period 1988 to 1996. The zone from the Marmara Sea to the North Aegean Trough is associated with strong right‐lateral shear motion, with maximum strain rates of 170 nstrain/a. In the northern Aegean Sea the extensional deviatoric axes are oriented NNE‐SSW, associated with strain rates reaching 150 nstrain/a, and in western Anatolia varying around N‐S with rates of up to 95 nstrain/a. The extensional areas mostly coincide with active graben features. The south‐western Aegean Sea is almost strain‐free. In general, the areas of high geodetic strain rates are accompanied by distinct seismic clusters whereas the strain‐free regions are nearly aseismic.
Crustal structure and seismicity of the Havre Trough at 26°S
Authors: Nishizawa Azusa , Takahashi Narumi , Abe Shintaro
Published: December 2003

An ocean bottom seismographic (OBS) experiment was carried out to investigate the present‐day tectonics at the northern end of the Havre Trough, a backarc basin in the southwestern Pacific. Hypocenter distribution shows no seismicity within 50 km of the OBS array but two active regions outside the Trough; one is to the northeast of the array at a bathymetric high between the Lau Basin and Havre Trough; the other is to the southeast of the array beneath the landward slope of the Kermadec Trench. P wavespeed structure obtained from the refraction survey is characterized by a thinned island arc crust with a thickness of 9–10 km. Many volcanic intrusions shown in reflection profiles that support extension tectonics are covered by undisturbed sediments. These suggest little present activity related to rifting and/or spreading.
Water activity and equilibrium freezing temperatures of aqueous NH4HSO4 solutions from −30 to 25°C
Authors: Chelf J. Holly , Martin Scot T.
Published: December 2003

One mechanism of cirrus cloud formation is homogeneous ice nucleation within ammoniated sulfuric acid particles. An important constraint on ice formation is the (NH4)2SO4‐H2SO4‐H2O phase diagram. In the completed laboratory work, the NH4HSO4‐H2O phase diagram is determined over the domain relevant to the troposphere. The H2O vapor pressures of aqueous NH4HSO4 solutions are measured from −30 to 25°C, and the compositions of the aqueous phase in equilibrium with a solid phase (i.e., ice or letovicite) are determined at several temperatures. Below 25°C and above 42 wt% NH4HSO4(aq), the first solid to form from supersaturated NH4HSO4(aq) is (NH4)3H(SO4)2(S), not NH4HSO4(s). Supercooling of nearly 20 K is required to initiate letovicite formation for 100 mL samples. The results of this study are in good agreement with the calculations of Clegg et al. [1998].
Particle production near marine clouds: Sulfuric acid and predictions from classical binary nucleation
Authors: Clarke A. D. , Kapustin V. N. , Eisele F. L. , Weber R. J. , McMurry P. H.
Published: December 2003

Recent experiments demonstrate that cloud processes in the free troposphere, and at times in the marine boundary layer (MBL), can result in the production of new aerosol particles linked to sulfuric acid production that is photochemically driven. Here we provide observational evidence from the tropics and mid‐latitudes indicating that this nucleation is often in accord with predictions of classical binary nucleation theory when it is applied to the high humidity environment near evaporating clouds edges located above the MBL. Coupled with suitable models for the relevant chemical species and conditions, these observations suggest a means for modeling natural particle production in these regions.
Effects of aircraft on aerosol abundance in the upper troposphere
Authors: Ferry G. V. , Pueschel R. F. , Strawa A. W. , Kondo Y. , Howard S. D. , Verma S. , Mahoney M. J. , Bui T. P. , Hannan J. R. , Fuelberg H. E.
Published: December 2003

A significant increase in H2SO4 aerosol concentration coincidental with an enhancement in NO was detected above 10 km pressure altitude during a cross‐corridor flight out of Shannon on October 23, 1997. The source of this aerosol is ascribed to commercial aircraft operations in flight corridors above 10 km, because (1) a stable atmosphere prevented vertical air mass exchanges and thus eliminated surface sources, (2) air mass back trajectories documented the absence of remote continental sources, and (3) temperature profiler data showed the tropopause at least one kilometer above flight altitude throughout the flight, thus excluding stratospheric sources. Particle volatility identified (60‐80)% H2SO4, ≈20% (NH4)2SO4 and ≈10% nonvolatile aerosol in the proximity of flight corridors, and (10‐30)% H2SO4, up to 50% (NH4)2SO4, and (40‐60)% nonvolatile aerosols in air that was not affected by aircraft operations below 10 km. The newly formed H2SO4 particles did not measurably affect surface area and volume of the background aerosol due to their small size, hence did not influence radiative transfer directly.
Type II shock and CME from the corona to 1 AU
Authors: Dulk George A. , Leblanc Yolande , Bougeret Jean‐Louis
Published: December 2003

We explore the relationship among solar flares, type II‐associated shock waves in the corona and solar wind, coronal mass ejections (CMEs), and shock waves observed at 1 AU. A clear example is that of 1997 Nov 4, where radio waves were observed continuously from 1800 MHz to 30 kHz. The CME was observed from 2.3 to 30 Ro. A shock was observed at 1 AU, followed by CME material. In addition a 2B, X 2.1 flare initiated a wave in the low corona, and streams of fast electrons produced intense type III bursts along their path, and Langmuir waves at 1 AU.

The liftoff time of the CME coincided to within a few minutes with the time of the impulsive flare and the initiation of the type II shock wave. The speed of the CME in the plane of the sky was similar to the derived speed of the type II shock from 1.26 to 78 Ro and the average speed of the shock detected at 1 AU, 646 km/s. Therefore, the observations of this event demonstrate that type II shock waves, CMEs and flares can be closely interrelated, that coronal and interplanetary type II shock waves can be inseparable, and that the ensemble can commence at ≲ 1.3 Ro and continue outward to produce a shock and geophysically important effects at Earth.
Sudden compression of the outer magnetosphere associated with an ionospheric mass ejection
Authors: Russell C. T. , Zhou X. W. , Chi P. J. , Kawano H. , Moore T. E. , Peterson W. K. , Cladis J. B. , Singer H. J.
Published: December 2003

On September 24, 1998 at 2345 UT the magnetosphere was suddenly compressed as the dynamic pressure of the solar wind rapidly rose from 2 to 15 nPa. At the Polar spacecraft, at high altitudes above the center of the northern polar cap, a remarkably smooth increase in the field strength occurred while the plasma properties changed abruptly, as described in an accompanying paper. Comparisons with models and an examination of the wave amplitudes during the compression indicate that the initial change in plasma properties was most probably due to convection of pre‐existing boundary layer plasma to the location of Polar rather than due to local heating by betatron acceleration and ion cyclotron waves. The smoothness of the increase in field strength is attributed to the very high velocity of compressional waves in the tail that outrun the advancing solar wind disturbance. The signatures as measured by GOES 10 at 1444 LT and at GOES 8 at 1846 LT in low latitude geosynchronous orbit are the more familiar sudden jump on the dayside, where the density is high and the compressional wave velocity low, and a weak change on the nightside, where tail current changes oppose the effects of the dayside magnetopause currents. This event is an ideal candidate for collaborative investigation of the effects of a classical sudden storm commencement on the magnetosphere.
Ionospheric mass ejection in response to a CME
Authors: Moore T. E. , Peterson W. K. , Russell C. T. , Chandler M. O. , Collier M. R. , Collin H. L. , Craven P. D. , Fitzenreiter R. , Giles B. L. , Pollock C. J.
Published: December 2003

We report observations of a direct ionospheric plasma outflow response to the incidence of an interplanetary shock and associated coronal mass ejection (CME) upon the earth's magnetosphere. Data from the WIND spacecraft, 185 RE upstream, document the passage of an interplanetary shock at 23:20 UT on 24 Sept. 1998. The polar cap plasma environment sampled by the POLAR spacecraft changed abruptly at 23:45 UT, reflecting the compressional displacement of the geopause relative to the spacecraft. POLAR left the polar wind outflow region and entered the mantle flows. Descending toward the dayside cusp region, POLAR later returned from the mantle to an enhanced polar wind flux dominated by O+ plasma and eventually containing molecular ions. The enhanced and O+− dominated outflow continued as the spacecraft passed through the high altitude cleft and then the southern cleft at lower altitude. Such a direct response of the ionosphere to solar wind dynamic pressure disturbances may have important impacts on magnetospheric dynamics.
Observations of suprathermal electron conies in an interplanetary coronal mass ejection
Authors: Feldman W. C. , Skoug R. M. , Gosling J. T. , McComas D. J. , Tokar R. L. , Burlaga L. F. , Ness N. F. , Smith C. W.
Published: December 2003

Solar wind suprathermal electron velocity distributions measured by the SWEPAM experiment aboard ACE were studied to determine the internal magnetic structure of the coronal mass ejection (CME) that passed 1 AU on 4–5 February, 1998. Pitch‐angle distributions range from symmetric counter‐streaming to complex distributions that include conics. Identification of suprathermal electron conies in interplanetary CMEs (ICMEs) is reported here for the first time. The origin of these conies is highly uncertain. We suggest, however, that the conics may originate in transient electron heating associated with magnetic reconnection within the magnetic legs of the CMEs. Such reconnection generates large, complex magnetic loops that have enhanced anti‐solar electric fields at their solar edge to maintain charge neutrality. This field must be sufficiently strong to bind electrons with high pitch angles to the bottom of the loops as they propagate away from the Sun.
A loop current‐induced jet along the edge of the West Florida Shelf
Authors: Hetland Robert D. , Hsueh Ya , Leben Robert R. , Niiler Pearn P.
Published: December 2003

The pressure imposed upon the West Florida Shelf by the Gulf of Mexico Loop Current is found to give rise to a southward flowing jet along the shelf edge. The pressure‐induced jet is simulated by a general circulation model of the Gulf. However, the physics causing formation of the jet are well represented by a simple continental shelf model incorporating an idealized geometry for the West Florida Shelf. The pressure response over the shelf, in an analogy to conductive heat transfer in a rod, is limited by the “insulating” effect of the steep topography of the West Florida Escarpment, which hinders the onshore spreading of the pressure influence. The shelf‐edge jet is apparent in the trajectories of satellite‐tracked surface drifters deployed from February 1996 through March 1997. Evidence for the requisite pressure distribution over the escarpment is provided by measurements of sea level from the satellite altimeter aboard the TOPEX/POSEIDON satellite.
Viewing seismic velocity anomalies with 3‐D continuous Gaussian wavelets
Authors: Bergeron Stephen Y. , Vincent Alain P. , Yuen David A. , Tranchant Benoît J. S. , Tchong Catherine
Published: December 2003

Seismic velocity anomalies (SVA) have traditionally been viewed as spatial objects. We present a new method for looking at SVA, based on a 3‐D continuous Gaussian wavelet transform. Local spectra of the seismic anomalies are calculated with the wavelet transforms. Two proxy quantities based on wavelets are used for viewing SVA. These proxy quantities are the 3‐D spatial distributions of (1.) the local maxima of the L2‐norm of the seismic anomalies, E‐max, and (2.) the associated local horizontal wavenumber k‐max. The P1200 tomographical model [Zhou 1996] has been used for this purpose. Geographical distributions of E‐max and k‐max yield information which are not obvious from direct visual inspection of SVA. Some examples are the depth extent of the tectonic boundaries and the inference of a plume‐like object beneath the transition zone under Iceland.
Large change of mesoscale variability in the Kuroshio Extension Region during the first 5 years of the TOPEX/Poseidon Mission
Authors: Wang Liping , Koblinsky Chester
Published: December 2003

Analysis of the first 5 years of TOPEX/Poseidon altimetry data reveals that mesoscale variability (MV) in the Kuroshio Extension region has a large, well structured temporal change. The mesoscale variance varies by more than a factor of 2 over the 5‐year span. The temporal variation appears to be the combination of two forms: a large‐scale standing (from 140°E to 170°E) modulation, and accompanying with it a variation that propagates westward slowly with a phase speed of about 0.7 cm/s. Along with the westward propagation, the center of maximum MV retreats westward. As a comparison, variation of MV in the Gulf Stream region is computed. The analysis shows that MV in the Gulf Stream region also undergoes large temporal change. But it is much less well structured.
The role of magma buoyancy in Caldera‐forming eruptions
Authors: McLeod Paul
Published: December 2003

Large calderas are formed by collapse of the crust into magma chambers during the eruption of vast quantities of silicic magma. Here I show that magmatic buoyancy can play a key role in attaining the conditions necessary for these eruptions to occur. During an eruption, magma buoyancy allows the simultaneous conditions of the chamber becoming underpressurized, whilst the conduit remains open, consequently the eruption continues and reduces chamber pressures further. The maximum chamber underpressures attained, and the associated stresses imposed on the surrounding crust, are dependent on the magma‐crust density contrast and chamber size. Sufficiently large imposed stresses cause the crust surrounding the chamber to collapse, stimulating a voluminous eruption and caldera formation. The increase in magma buoyancy associated with the compositional evolution of a magma body accounts for the common transition from initial small or moderate sized intermediate composition eruptions, to ultimately large silicic caldera collapse events.
The role of BrNO3 in marine tropospheric chemistry: A model study
Authors: Sander R. , Rudich Y. , von Glasow R. , Crutzen P. J.
Published: December 2003

Laboratory studies have shown that bromine nitrate (BrNO3) reacts on sulfuric acid and on ice particles. Here we investigate the potential role of BrNO3 in the marine boundary layer (mbl) assuming that it reacts on sea‐salt particles as well. Using the chemical box model MOCCA we find that heterogeneous reactions of BrNO3 on aerosol particles could affect the chemistry in four major ways: 1) They increase loss of NOx (=NO+NO2) from the gas phase; 2) They accelerate loss of bromide and chloride from sea‐salt aerosols. This dehalogenation occurs without the consumption of aerosol acidity; 3) The resulting loss of NOx and the increase of gas‐phase bromine species both lead to O3 destruction; 4) The resulting increase of reactive chlorine species affects gas‐phase hydrocarbons as well as S(IV) oxidation by HOCl in sea‐salt aerosols.
On the importance of weak steady shear in the refraction of short internal waves
Authors: Buckley Greg , Broutman Dave , Rottman James W. , Eckermann Stephen
Published: December 2003

Ray theory is used to study the refraction of short oceanic internal waves by a spectrum of large amplitude inertia waves superimposed on a weakly sheared steady current. The results suggest that the steady current has a significant cumulative effect on short‐wave propagation over the timescale of a few inertia periods. The strength of ray convergence is also computed, as this affects short‐wave amplitudes. Typically we find weak ray convergence and much slower growth toward instability with increasing vertical wavenumber than in a steady‐shear critical‐layer model.
Long‐term drift of the coronal source magnetic flux and the total solar irradiance
Authors: Lockwood M. , Stamper R.
Published: December 2003

We test the method of Lockwood et al [1999] for deriving the coronal source flux from the geomagnetic aa index and show it to be accurate to within 12% for annual means and 4.5% for averages over a sunspot cycle. Using data from four solar constant monitors during 1981–1995, we find a linear relationship between this magnetic flux and the total solar irradiance. From this correlation, we show that the 131% rise in the mean coronal source field over the interval 1901‐1995 corresponds to a rise in the average total solar irradiance ΔI = 1.65±0.23 Wm−2.
Observations and modeling of the April 10–12, 1997 ionospheric storm at Millstone Hill
Authors: Schlesier A. C. , Buonsanto M. J.
Published: December 2003

The Millstone Hill Ionospheric Model is used to simulate the April 10–12, 1997 ionospheric storm. For the first time determinations of the height‐varying wind from incoherent scatter radar measurements are used to simulate the ionospheric plasma. Results indicate that the observed dusk effect is due to a rise in HmF2 combined with an enhanced downward flux of ionization, associated with an altitude variation in the neutral wind. The negative phase on April 11 is fully explained by increased recombination due to the increased neutral composition ratios N2/O and O2/O given by the MSIS model, except that reproduction of the observed G‐condition during the morning hours requires these ratios to be larger than those in MSIS‐86. This is consistent with the concept of a composition disturbance zone rotating into the morning sector following a storm which commenced during the nighttime hours.
Initial measurements of the lunar induced magnetic dipole moment using Lunar Prospector Magnetometer data
Authors: Hood Lon L. , Mitchell David L. , Lin Robert P. , Acuna Mario H. , Binder Alan B.
Published: December 2003

Twenty‐one orbits of Lunar Prospector magnetometer data obtained during an extended passage of the Moon through a lobe of the geomagnetic tail in April 1998 are applied to estimate the residual lunar induced magnetic dipole moment. Editing and averaging of individual orbit segments yields a negative induced moment with amplitude −2.4 ±1.6 × 1022 Gauss‐cm³ per Gauss of applied field. Assuming that the induced field is caused entirely by electrical currents near the surface of a highly electrically conducting metallic core, the preferred core radius is 340±90 km. For an iron‐rich composition, such a core would represent 1 to 3% of the lunar mass.
Lodestone: Natures only permanent magnet‐What it is and how it gets charged
Authors: Wasilewski Peter , Kletetschka Günther
Published: December 2003

Magnetite and Titanomagnetite exhibit magnetic properties which are attributable to the micro‐structures developed during oxidation and exsolution: All magnetite iron ores which are lodestones contain maghemite. These lodestones have Hc between 10 and 30 mT, SIRM between 8 and 18 Am²kg¹ and RI between 0.10 and 0.26. Magnetite, titanomagnetite and metals have REM values (ratio of NRM to SIRM) < 0.05. Samples (called fulgarites) obtained from the Smithsonian Institution have REM values ranging from 0.45 to 0.92. The REM value serves as a witness parameter to the magnetic fields associated with the lightning bolt. If a high REM value (say ≫ 0.1) can be verified as not to be due to contamination by man and does not contain MD hematite then the rock has LRM (lightning remanent magnetization). The magnetic field associated with lightning can be revealed from an isothermal remanent acquisition (RA) curve.
Role of nitrogen oxides in the stratosphere: A reevaluation based on laboratory studies
Authors: Portmann Robert W. , Brown Steven S. , Gierczak Tomasz , Talukdar Ranajit K. , Burkholder James B. , Ravishankara A. R.
Published: December 2003

The changes in chemical partitioning and stratospheric O3 abundance due to the recently measured rate coefficients for the O + NO2, OH + HNO3, and OH + NO2 reactions are examined using a two‐dimensional model. The rate constant changes increase NOx abundance (up to 40%) and NOx‐catalyzed O3 destruction, and extend down by several kilometers the altitude region where NOx dominates catalytic O3 destruction. Reductions in the abundance of HOx (10–30%) and ClOx (20‐40–) in the lower stratosphere partially buffer the effect on column O3 amount. Column O3 at middle and high latitudes is reduced by 2–10% depending on season for current halogen levels. The model derived long‐term O3 trend at midlatitudes due to increases in anthropogenic halogens is reduced by approximately 30%.
Increases in early season ecosystem uptake explain recent changes in the seasonal cycle of atmospheric CO2 at high northern latitudes
Authors: Randerson J. T. , Field C. B. , Fung I. Y. , Tans P. P.
Published: December 2003

We report changes in the seasonal cycle of atmospheric CO2 at high northern latitudes from 1980 to 1997 based on NOAA/CMDL observation stations. Using a combination of biogeochemical and atmospheric modeling approaches, we show that increases in early season net ecosystem uptake explain the recent trends in the seasonal cycle. A strong year‐to‐year correlation between spring temperatures and early season uptake further suggests that increased photosynthetic activity is the primary mechanism. At the end of the growing season, a strong correlation between fall temperatures and late season releases provides evidence for a large active pool of decomposing soil carbon. Taken together, our results suggest that the seasonal timing of temperature anomalies may have important consequences for the interannual carbon balance of northern ecosystems.
Two modes of appearance of the Odden Ice Tongue in the Greenland Sea
Authors: Wadhams Peter , Comiso Josefino C.
Published: December 2003

The Odden ice tongue of the Greenland Sea normally forms locally in winter as frazil‐pancake ice allowing for high positive salt fluxes during freezing that leads to open ocean convection. We report that another type of Odden can develop usually late in the season and is composed of old ice advected through the East Greenland Current and by the Jan Mayen Current. This type causes the introduction of more meltwater that stabilizes the water column, enhances productivity, and affects the carbon cycle in the region. The history of Oddens is reviewed and our results indicate that from 1978 through 1997, the first type occurred almost every year except in 1984, 1994, and 1995, while the second type has been observed to occur in 1987 and 1996.
North Pacific sea surface temperatures: Past variations inferred from tree rings
Authors: D'Arrigo Rosanne , Wiles Gregory , Jacoby Gordon , Villalba Ricardo
Published: December 2003

March–August sea surface temperatures (SST) are reconstructed for the Gulf of Alaska (GOA) from 1750–1983 based on tree‐ring data from coastal and south‐central Alaska and the Pacific Northwest. Some of the trends resemble those documented in other northern instrumental and proxy records, including cooler SSTs in the early and middle 1800s, during the Little Ice Age. There is overall warming in this century, including a positive trend from the mid‐1970s to 1980s, following cooler 1960s–1970s. The twentieth century warming exceeds maxima in the reconstructed SSTs back to AD 1750 and is consistent with other evidence for unusual Northern Hemisphere warming. Changes over the period of recorded North Pacific SST have been linked to a pattern of variability known as the Pacific Decadal Oscillation (PDO). Maps comparing the reconstruction to the North Pacific SST field and other analyses suggest that it may reflect variations related to the PDO over several centuries.
Steller Brewer, ozonesonde, and DIAL measurements of Arctic O3 column over Eureka, N.W.T. during 1996 winter/spring
Authors: McDonald Michael K. , Turnbull David N. , Donovan David P.
Published: December 2003

Ozone total column amounts derived from differential UV absorption of starlight measurements made using the new Stellar Brewer instrument are compared with simultaneous measurements using a DIAL system and ECC ozonesondes. Good agreement within the 2% error estimate of the Stellar Brewer is shown between the various methods after correction is made for a calibration offset error for the Stellar Brewer. All three methods identify a generally decreasing trend of total ozone column between day 15 and 75 of the 1996 spring season.
Role of planetary waves in the stratosphere‐troposphere coupled variability in the northern hemisphere winter
Authors: Kuroda Yuhji , Kodera Kunihiko
Published: December 2003

The role of planetary waves in stratosphere‐troposphere coupled variability is investigated using an extended singular value decomposition analysis of zonal‐mean zonal wind and the vertical component of the Eliassen‐Palm (E‐P) flux for the winters from 1979/80 to 1995/96. The results suggest a close relationship between anomalies of zonal‐mean zonal wind and the convergence zone of E‐P flux, which together shift poleward and downward from the stratosphere to the troposphere as time advances. Following enhanced vertical propagation of waves into the stratosphere, the Arctic Oscillation (AO) pattern is seen in the 500 hPa geopotential height field in association with an increased poleward propagation of tropospheric waves.
Connections among ice, runoff and atmospheric forcing in the Beaufort Gyre
Authors: Macdonald R. W. , Carmack E. C. , McLaughlin F. A. , Falkner K. K. , Swift J. H.
Published: December 2003

During SHEBA, thin ice and freshening of the Arctic Ocean surface in the Beaufort Sea led to speculation that perennial sea ice was disappearing [McPhee et al., 1998]. Since 1987, we have collected salinity, δ18O and Ba profiles near the initial SHEBA site and, in 1997, we ran a section out to SHEBA. Resolving fresh water into runoff and ice melt, we found a large background of Mackenzie River water with exceptional amounts in 1997 explaining much of the freshening at SHEBA. Ice melt went through a dramatic 4–6 m jump in the early 1990s coinciding with the atmospheric pressure field and sea‐ice circulation becoming more cyclonic. The increase in sea‐ice melt appears to be a thermal and mechanical response to a circulation regime shift. Should atmospheric circulation revert to the more anticyclonic mode, ice conditions can also be expected to revert although not necessarily to previous conditions.
A comparison of competing explanations for the 100,000‐yr Ice Age cycle
Authors: Roe Gerard H. , Allen Myles R.
Published: December 2003

There currently exists no consensus as to the cause of the ice ages of the late Pleistocene. Many of the competing hypotheses have been formulated into mathematical models which enables a rigorous comparison to be made. Spectral analysis fails to distinguish rival models. Using regression analysis, we examine the relative performance of several models, each representative of a different type of modeling approach, as explanations of both the global ice volume and also the time rate of change of the global ice volume. We find there is no objective evidence in the record in favor of any particular model. The respective merits of the different theories must therefore be judged on physical grounds.
Particle nucleation by recondensation in combustion exhausts
Authors: Chen Jen‐Ping
Published: December 2003

Observational and experimental evidence is presented here to verify a hypothesized “recondensation‐induced” nucleation mechanism. While analyzing the diurnal variations in particle number concentration in an urban area, intense particle production was found to occur during the commuting hours even when there was no significant photochemical activity. Combustion‐induced nucleation processes occurring in fresh automobile exhausts are believed to be responsible for the observed phenomenon. It is hypothesized that besides the more familiar fuel‐sulfur conversion mechanism, particle nucleation may also result from the recondensation of chemicals vaporized from preexisting particles in the intake air during combustion. An experimental verification was performed by heating the ambient air without the use of fuel, then cooling it down to allow for nucleation. A net particle production of over 700,000 cm−3 was achieved during this heating‐then‐cooling procedure. The results indicate that the recondensation‐induced mechanism is potentially important in various types of combustion exhausts.
Interplate coupling in the Tokai District, central Japan, deduced from continuous GPS data
Authors: Sagiya Takeshi
Published: December 2003

I invert GPS displacement rates in the Tokai district to investigate strain accumulation associated with the anticipated Tokai earthquake. I apply a representation of interseismic strain accumulation at subduction zones by Savage [1983] and estimate a distribution of virtual normal fault slip (back‐slip) on the plate boundary surface. Estimated back‐slip takes its maximum value of 30–40mm/year under the Sea of Enshu. This value is nearly equal to the relative plate motion there, implying almost complete coupling. Back‐slip is smaller under Suruga Bay, and its direction is different from the relative motion between the Eurasian and the Philippine Sea plates. Localized deformation at the northern tip of the Philippine Sea plate may be responsible for this discrepancy, partitioning tectonic strain due to the plate convergence into faults on both sides of the Izu peninsula and also distributed strain inside the peninsula.
Melting of a subducting slab and production of high‐mg andesite magmas: Unusual magmatism in SW Japan at 13∼15 Ma
Authors: Furukawa Y. , Tatsumi Y.
Published: December 2003

Characteristic high‐Mg andesite magmas were produced in the SW Japan arc at 13∼15 Ma that was synchronous with the commencement of subduction of a very young (<11 m.y.) lithosphere of the Shikoku Basin. Numerical simulation suggests that temperature at the surface of such a young subducting plate is high enough for partial melting both of the subducting sediments and oceanic crust at the beginning of the subduction. High‐Mg andesite magmas were likely to be produced by interaction between silicic slab melts and the overlying mantle wedge. HMA magmas may be commonly produced in the Archean subduction zones under relatively high mantle temperature conditions, contributing to making continental crusts.
Comparison of aerosol optical depth from four solar radiometers during the fall 1997 ARM intensive observation period
Authors: Schmid B. , Michalsky J. , Halthore R. , Beauharnois M. , Harrison L. , Livingston J. , Russell P. , Holben B. , Eck T. , Smirnov A.
Published: December 2003

In the Fall of 1997 the Atmospheric Radiation Measurement (ARM) program conducted an Intensive Observation Period (IOP) to study aerosols. Five sun‐tracking radiometers were present to measure the total column aerosol optical depth. This comparison performed on the Southern Great Plains (SGP) demonstrates the capabilities and limitations of modern tracking sunphotometers at a location typical of where aerosol measurements are required. The key result was agreement in aerosol optical depth measured by 4 of the 5 instruments within 0.015 (rms). The key to this level of agreement was meticulous care in the calibrations of the instruments.
Thermospheric composition changes deduced from geomagnetic storm modeling
Authors: Förster M. , Namgaladze A. A. , Yurik R. Y.
Published: December 2003

To test various hypotheses about positive ionospheric storm development, we numerically simulated the magnetic storm of 24–27 January 1974 to obtain the global pattern of its thermospheric and ionospheric effects. We use a global self‐consistent numerical model of the thermosphere‐ionosphere‐magnetosphere system which calculates all plasma parameters as well as electric fields both of magnetospheric and thermospheric dynamo origin. The predicted neutral composition changes are consistent with observations of the AE‐C and ESRO‐4 satellites. The storm‐to‐quiet density ratio of [O]/[N2] (at a fixed height) does not change significantly at middle and low latitudes while the absolute density of all neutral constituents is enhanced. The density ratio at a fixed pressure level can be slightly enhanced under certain conditions. Positive ionospheric storm effects during the main phase of the storm are shown to be mainly due to the uplifting of the ions along the field lines by an equatorward directed disturbance wind component at middle latitudes and their equatorward (convergent) movement at low latitudes. This is driven by the passage of travelling atmospheric disturbances and by the large‐scale disturbance wind circulation. Under daylight conditions minor contributions arise from the general thermal density enhancement of all constituents favoring positive ionospheric response due to a stronger ion production rather than loss. Height dependent deviations from diffusive equilibrium of minor thermospheric constituents are due to the relatively rapid (in comparison with their diffusion) vertical bulk motion.
WINDII measurements of nightglow enhancements in the South Atlantic Magnetic Anomaly Zone
Authors: Wiens R. H. , Bhatnagar V. P. , Cogger L. L.
Published: December 2003

Enhancements of the O(¹D) 630 nm and O(¹S) 558 nm volume emission rates were detected by WINDII, the Wind Imaging Interferometer on board the Upper Atmosphere Research Satellite, UARS, as its limb‐locked fields of view crossed the South Atlantic magnetic anomaly zone during periods of high geomagnetic activity. The enhancement attributed to electron precipitation is 20 R for the 630 nm red line and 3 R for the 558 nm green line, less than the natural variability of these nightglow emissions as seen from below. Nevertheless, statistical tests indicate with 95% confidence that the enhancements are significantly distinguishable from the natural variability. The red enhancement lies west of the green because eastward drifting trapped electrons move toward lower mirror altitudes in this region. These enhancements are energetically consistent with earlier measurements of electron fluxes in this region; we estimate the total precipitation energy deposition rate at a few megawatts.
Simulation of the December 1998 Stratospheric Major Warming
Authors: Manney G. L. , Lahoz W. A. , Swinbank R. , O'Neill A. , Connew P. M. , Zurek R. W.
Published: December 2003

An atypically early major stratospheric sudden warming in mid‐Dec 1998 resulted in an abnormally warm and weak polar vortex through most of the 1998–99 winter. The first major warming in nearly 8 years, it was only the second major warming observed before the end of Dec, and strongly resembled the previous Dec 1987 major warming in several characteristics atypical of major warmings later in winter. 3D mechanistic model simulations reproduced most characteristics of the Dec 1998 major warming, including the magnitudes of zonal mean easterlies and temperature increases and the 3D evolution of the flow, paving the way for more detailed future studies of the mechanisms involved in this unusual event.
Characterization of particles from stratospheric launch vehicle plumes using wavelength‐dependent lidar techniques
Authors: Dentamaro Anthony V. , Dao Phan D. , Farley Robert , Ross Martin
Published: December 2003

Our Mobile Lidar Trailer (MLT) has been deployed to Cape Canaveral Air Station for the purpose of studying the characteristics of launch vehicle plumes in the stratosphere. In addition to measurements of plume extent and dispersion rates, information on particle species and size can be obtained from the wavelength dependence of the Mie return signal. We measure the backscattering ratio of Mie to Rayleigh return at several wavelengths and compare the results to a model of Mie scattering cross sections for homogeneous spheres of specific refraction index and radius. Of primary interest are the calculations for particles which are present in the exhaust of solid rocket motors (SRM) and are conjectured to be instrumental in the catalysis of halogenic destruction of stratospheric ozone. Our data indicate that these particles, at least within the first half‐hour after launch, are small (r < 50 nm as an upper limit). The data also shows a trend of the mean particle radius increasing with time.
Ulysses measurements of variations in the solar wind‐interstellar hydrogen charge exchange rate
Authors: McComas D. J. , Funsten H. O. , Gosling J. T. , Pryor W. R.
Published: December 2003

Charge exchange with solar wind protons is the primary ionization process for interstellar hydrogen traveling through the heliosphere. In this study we use Ulysses solar wind observations to examine and quantify variations in charge exchange. We find that these variations are largest within stream interaction regions where the charge exchange rate is tens of times larger in compressional, corotating interaction regions (CIRs) than in rarefactions. Similarly, we find enhanced charge exchange in compression regions ahead of fast CMEs. As a consequence, much of the interstellar hydrogen at low latitudes is picked up in pulses as CIRs and fast CMEs sweep past. Observations over Ulysses' first full polar orbit indicate that the charge exchange rate is higher at low than at high latitudes, and that this rate drops off more slowly than the inverse square of heliocentric distance. We believe that this is due to the growth of CIRs as they propagate out through the inner heliosphere. The variability of hydrogen charge exchange has implications for the analysis of scattered Lyman‐α observations and produces variations in the pickup rates of newly ionized interstellar hydrogen, which is a seed population for anomalous cosmic rays.
Paleoenvironmental conditions in a Travertine Complex deduced from rock magnetism
Authors: Reinders Jan , Hambach Ulrich
Published: December 2003

We present a rock magnetic study on ca. 100 specimens from a 7.5 m travertine section (BMH) and a parallel 1.0 m profile (BMP) to evaluate vertical and lateral variations. Concentration dependent parameters and inter‐parametric ratios point to varying redox conditions through time and space suggesting local paleoenvironmental rather than paleoclimatic control of the rock magnetic properties.
Scattering pattern of lightning‐induced ionospheric disturbances associated with early/fast VLF events
Authors: Johnson M. P. , Inan U. S. , Lev‐Tov S. J. , Bell T. F.
Published: December 2003

Simultaneous observations of early/fast Very Low Frequency (VLF) events at nine closely spaced (∼65 km) sites are used together with a numerical model of the propagation and scattering of VLF signals in the earth‐ionosphere waveguide to directly measure the scattering pattern of associated ionospheric disturbances. In cases when the causative lightning is within 700 km of the north‐south array of observing sites, early/fast VLF events are typically observed at no more than 2 or 3 sites, which indicates a narrow beam of the scattered signal in the forward direction. In the different cases studied, forward scattering patterns exhibit 15 dB beamwidths of less than 30° consistent with horizontal extent of 90±30 km.
A wave interference experiment with HAARP, HIPAS, and WIND
Authors: Rodriguez P. , Kennedy E. J. , Keskinen M. J. , Basu Sa. , McCarrick M. , Preston J. , Zwi H. , Engebretson M. , Wong A. , Wuerker R. , Kaiser M. L. , Desch M. D. , Goetz K. , Bougeret J.‐L. , Manning R.
Published: December 2003

We report on the first experiment using two high power, high frequency transmitting facilities in a bistatic, interferometer mode. The HAARP and HIPAS facilities in Alaska radiated at 4525 kHz with total combined power of about 700 kW, in the direction of the WIND spacecraft. The WAVES experiment aboard WIND received the transmissions at a distance of about 25 earth radii. The experimental setup thus resembled Young's two‐slit experiment. The expected interference pattern was observed; at the distance of WIND, the fringe size was about 30 km peak to peak.
A new mechanism for interpreting the motion of auroral arcs in the nightside ionosphere
Authors: Semenov V. S. , Bogdanova Y. V. , Rijnbeek R. P. , Buchan M. J.
Published: December 2003

A new mechanism is proposed for predicting and interpreting the motion of auroral arcs observed in the nightside ionosphere during the expansion phase of a substorm. This mechanism is centred on the idea that such arcs act as visible manifestations of the arrival of earthward‐propagating shock waves in the near‐Earth magnetosphere. These shock waves are generated at a near‐Earth X‐line, and propagate at the local Alfvén speed. Because of the non‐uniform nature of the magnetised plasma in the magnetotail, dispersion results in a change in the shape of the wave fronts as the shocks propagate towards the ionosphere. Theoretical analysis shows that a variety of arc motions can occur as a result of this dispersion, depending on factors such as the reconnection rate, the location of the reconnection site, and gradients in the magnetic field strength and plasma density.
A model of the lightning discharge at Jupiter
Authors: Farrell W. M. , Kaiser M. L. , Desch M. D.
Published: December 2003

Based on the lightning waveform and spectra observed by the Galileo Atmospheric Probe, we present a discharge, radiation, and propagation model of the Jovian lightning that explains the absence of detectable HF spherics along with the measurement of ELF whistler emissions by the Voyager radio and plasma wave instruments. We find that although there is signal attenuation in the ionosphere, the controlling factor in determining lightning detectability at Jupiter is the intrinsically slow nature of the lightning discharge itself. The proposed discharge model is not unique, but matches the observed spectrum which spans several frequency decades and provides a basis for comparing lightning discharge models for other planets.
How does plate coupling affect crustal stresses in northeast and southwest Japan?
Authors: Wang Kelin , Suyehiro Kiyoshi
Published: December 2003

Plate subduction causes compression of the continental crust in Northeast (NE) Japan but not in Southwest (SW) Japan. We propose that the different effects are both consistent with weak subduction faults, of which the static shear stress is described using an effective coefficient of frictionμ′. Stresses in the overriding plate are controlled by two competing factors, the plate coupling force, inducing compression, and the gravitational force, inducing tension. In cold subduction zones such as NE Japan the frictionally coupled portion of the thrust fault is wider and extends to a greater depth. Thus even a lowμ′ can give rise to a large total plate coupling force and hence compression in the upper plate. Using a model of two converging plates in frictional contact, we find that aμ′ of 0.03 explains the first‐order stresses of both NE and SW Japan.
A model analysis of Galileo electron densities on Jupiter
Authors: Majeed T. , McConnell J. C. , Gladstone G. R.
Published: December 2003

A one‐dimensional chemical‐diffusive model of the Jovian ionosphere, in conjunction with measured upper atmospheric temperatures, is used to analyze the upper ionospheric electron densities on Jupiter measured by the Galileo RSS instrument on December 8, 1995. The analyses of these measurements have yielded quite different ionospheric properties at ingress and egress in terms of both the magnitude and the altitude of the peak electron density (ne). At ingress, the peak ne was ∼105 cm−3 at an altitude of ∼900 km. However, at egress the ne peak was ∼5 times smaller than at ingress and was located at ∼1800 km altitude. As with our previous studies, we find it necessary to invoke a combination of vibrationally excited H2 and vertical plasma flow to explain the measured ionospheric structure. The most interesting conclusion of this study is that a downward drift of plasma is required to fit the peak altitude of the ingress ne profile. The direction of the vertical flow is most likely determined by the horizontal neutral wind. At egress, the situation is quite different because a strong field‐aligned drift of 90 m/s, most likely caused by the meridional component of the neutral wind, is required to maintain the peak ne at the measured altitude. The role of vibrationally excited H2 in determining the magnitude of the measured ne appears to be less important at ingress than at egress.