bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of temperature variability in observations and sixteen climate model simulations
Authors: Bell J. , Duffy P. , Covey C. , Sloan L.
Published: February 2004

Understanding how much, if any, of observed climate changes are anthropogenic depends upon understanding the magnitude and spatial patterns of natural climate variability. We have compared simulated surface air temperature (SAT) variability in 16 coupled ocean‐atmosphere‐sea ice climate model simulations to observed temperature variability. The majority of the simulations exhibit excessive air temperature variability over land while simulated temperature variability over oceans is generally too low. The ratio of variability over land to over oceans is too high in all the simulations, relative to observations. We have identified several factors which may contribute to the differences in temperature variability. In particular, many of the models use ”bucket” land surface schemes which produce greater temperature variability over land, due to lower levels of soil moisture, than more realistic land surface schemes produce.
Retrospective simulation of a storm event: A first step in coupled climate/hydrologic modeling
Authors: Yu Zhongbo , Barron E. J. , Schwartz F. W.
Published: February 2004

Global and regional climate models are valuable tools for assessing the effects of natural and anthropogenic perturbations to climate and hydrology. Results of a coupled regional climate and hydrologic model system, designed for the integrated assessment of climate‐hydrologic impacts at regional scales demonstrate that (a) simulated precipitation in a storm event is sensitive to the spatial resolution of the regional climate model and (b) spatial variability of precipitation and hydraulic variables must be accounted for in order to realistically capture the basin‐scale hydrologic response to a storm event. The regional climate model (with a spatial resolution of 4 to 36 km) can be driven either by global climate model output (with resolutions at the order of 100 km) or by observed climate data. The meteorological fields simulated over the mid‐Atlantic region of the USA were disaggregated to drive the basin‐scale hydrologic model (with a resolution of 1 km). With the improved treatment of spatial variability, the simulated streamflow at the basin outlet compares well with observations. These results from coupled climate‐hydrologic models at regional scales suggest that climate‐hydrology modeling studies that do not allow for spatial variability may be misleading.
Cause of tropical Pacific warming trend
Authors: Liu Zhengyu , Huang Boyin
Published: February 2004

Combining observations and model simulations, the equatorial upper ocean heat budget is closed to diagnose the cause of the 1945–93 sea surface temperature (SST) trend. The equatorial Pacific SST exhibits a clear warming trend, in spite of a cooling trend in the net downward surface heat flux. This warming is caused primarily by the reduction of wind‐driven cold ocean current.
A new εfunction for atmospheric correction algorithm
Authors: Su Wenying
Published: February 2004

In this paper the atmospheric correction algorithms for two ocean color sensors, CZCS and SeaWiFS, were analyzed. Based upon the analysis, the 6S model was used to study the relationship between ρas( λ) and ρa(λ)+ρra(λ) and to develop a new ε function. The new ε3(λ, 865) function considered the aerosol scattering effect and the interaction between aerosols and atmospheric molecules as a whole. Using the ε3(λ865) instead of the original SeaWiFS defined ε(λ, 865) could avoid the converting between ρas(λ) and ρa(λ)+ρra(λ) and help to simplify the atmospheric correction algorithm to a great extent.
Fast ductile failure of passive margins from sediment loading
Authors: Branlund J. , Regenauer‐Lieb K. , Yuen D.
Published: February 2004

Sediment loading at continental margins has been interpreted as a very inefficient mechanism for initiating subduction. We have re‐investigated this problem using a time‐dependent, non‐linear ductile failure analysis in which the effects of power‐law plastic strain‐hardening are assessed. The results follow classical flexural rigidity solutions until wholesale lithosphere failure occurs. Sediment loading causes two shear zones to develop from the bottom of the lithosphere upwards. For strong strain‐hardening, shear zones nucleate earlier but the plate may never break. For small hardening, the instability grows much faster and the plate can break under the sediment load with a limiting yield stress lower than 0.4 GPa. When the ductile faults growing from the top and the bottom of the plate merge in the center, the flexurally supported gravitational energy is released; the lithosphere becomes unstable and shears off super‐exponentially within a few million years.
Feedback effects of variable thermal conductivity on the cold downwellings in high Rayleigh number convection
Authors: Dubuffet Fabien , Yuen David A. , Yanagawa Tomo
Published: February 2004

The thermal structure of the vertical boundary layers in mantle convection can be seriously influenced by the phonon contribution of the thermal conductivity because of its decreasing nonlinear dependence with increasing temperature. Such a dependence would induce the cold descending slabs to be considerably warmer than the canonical models with constant conductivity. We have carried out both 2‐D and 3‐D convection calculations, using a temperature and pressure‐dependent thermal conductivity with a jump at 670 km depth. In order to determine the influence of advection in counteracting the nonlinear thermal diffusion, we have gone up to a Rayleigh number of 7 × 106 for a constant viscosity model with variable conductivity. Our comparison shows unequivocally that the cold downwellings with a high conductivity are disappearing to a greater degree in the lower mantle at depths of around 1500 to 2000 km than models with constant conductivity. This divergence in the visibility of cold downwellings increases with larger Rayleigh numbers, because of the negative feedback nature of the nonlinear dependence in the temperature‐dependent conductivity. Our results would suggest that many cold slabs sinking through the lower mantle with a realistic conductivity would become thermally assimilated in the bottom 1000 km of the mantle.
Satellite magnetic anomalies related to seafloor spreading in the South Atlantic Ocean
Authors: Purucker Michael E. , Dyment Jerome
Published: February 2004

Oceanic magnetic anomalies have been observed from satellite. The strongest anomalies are the long‐wavelength components of the sea‐floor spreading signature. Unfortunately, because of technical issues involving the treatment of satellite magnetic data, these signals are obscured in the South Atlantic Ocean because they trend north‐south. However, a map does exist in which such features are observed, essentially because of a better data processing technique. Further, this map agrees with a physically motivated model based on non‐satellite magnetic input. Hence, with properly treated data, the magnetic anomaly maps should be useful for saying something about the geology, rather than vice‐versa. This situation will be considerably improved by ongoing advances in methods and new data sets. The amplitude of the observations, a factor of two larger than previous estimates, confirms that the extrusive basaltic layer alone is inadequate to produce the signal and that deeper oceanic sources are required.
In situ Observation of ilmenite‐perovskite phase transition in MgSiO3 using synchrotron radiation
Authors: Ono S. , Katsura T. , Ito E. , Kanzaki M. , Yoneda A. , Walter M. J. , Urakawa S. , Utsumi W. , Funakoshi K.
Published: February 2004

In situ observations of the ilmenite‐perovskite transition in MgSiO3 were carried out in a multianvil high‐pressure apparatus interfaced with synchrotron radiation. The phase boundary between ilmenite and perovskite in the temperature range of 1300–1600 K was determined to be P (GPa) = 28.4(±0.4) ‐ 0.0029(± 0.0020)T (K) based on Jamieson's equation of state of gold [Jamieson et al., 1982] and P (GPa) = 27.3(±0.4) ‐ 0.0035(±0.0024)T (K) based on Anderson's equation of state of gold [Anderson et al., 1989]. The consistency of our results, using Jamieson's equation of state, with previous studies obtained by quench methods leads us to conclude that the 660 km seismic discontinuity in the mantle can be attributed a phase transition to perovskite phase. However, the phase boundary based on the Anderson's equation of state implies that the depth of the 660‐km seismic discontinuity does not match the pressure of this transition.
Performances of ground penetrating radars in arid volcanic regions: Consequences for Mars subsurface exploration
Authors: Paillou Ph. , Grandjean G. , Malézieux J.‐M. , Ruffié G. , Heggy E. , Piponnier D. , Dubois P. , Achache J.
Published: February 2004

A GPR field experiment in the Republic of Djibouti provides evidence for very low radar penetration in arid volcanic materials, in the range 100–500 MHz. This phenomenon is attributed to the high iron oxide and evaporite concentration in soils, which significantly increases the conductivity, thus leading to poor subsurface imaging performances. The geologic context in Djibouti is shown to provide a good terrestrial analogue to Mars geology. Results of this study show that the future sounding radar missions to Mars may not reach the penetration depths previously anticipated.
January 30, 1997 eruptive event on Kilauea Volcano, Hawaii, as monitored by continuous GPS
Authors: Owen Susan , Segall Paul , Lisowski Michael , Miklius Asta , Murray Mark , Bevis Michael , Foster James
Published: February 2004

A continuous Global Positioning System (GPS) network on Kilauea Volcano captured the most recent fissure eruption in Kilauea's East Rift Zone (ERZ) in unprecedented spatial and temporal detail. The short eruption drained the lava pond at Puèu Oèo, leading to a two month long pause in its on‐going eruption. Models of the GPS data indicate that the intrusion's bottom edge extended to only 2.4 km. Continuous GPS data reveal rift opening 8 hours prior to the eruption. Absence of precursory summit inflation rules out magma storage overpressurization as the eruption's cause. We infer that stresses in the shallow rift created by the continued deep rift dilation and slip on the south flank décollement caused the rift intrusion.
Insights into Martian water reservoirs from analyses of Martian meteorite QUE94201
Authors: Leshin Laurie A.
Published: February 2004

The martian atmospheric D/H value of 5.2 times terrestrial is significantly higher than any found on Earth, and has been ascribed to preferential loss of H relative to D from the atmosphere through Jeans escape over time. Here, based on ion microprobe analyses of apatite grains from martian meteorite QUE94201, it is shown that the pre‐Jeans escape martian water reservoir has a D/H value ∼twice that of terrestrial water, rather than the “terrestrial” value that has been assumed in prior work. The data support a two‐stage history for martian volatiles in which early hydrodynamic escape enriched martian water to ∼2x terrestrial D/H values. Subsequent Jeans escape to produce the current atmospheric values has thus been responsible for less D‐enrichment than previously thought. A martian crust containing 2–3 times more water than previously proposed is implied by the results.
Co‐seismic deformation during the Mw7.3 Aqaba Earthquake (1995) from ERS‐SAR interferometry
Authors: Klinger Yann , Michel Rémi , Avouac Jean‐Philippe
Published: February 2004

The Mw7.3 1995 Aqaba earthquake is the largest instrumental earthquake along the Dead Sea Fault. We complement previous seismological studies by analyzing co‐seismic ground displacement from differential interferometry computed from ERS images spanning 3 different areas. They are compared with a synthetic model derived from seismological study. Only far‐field deformation related to the main sub‐event could be revealed because the near‐field area lies within the gulf. The interferometric data imply a 56 km long and 10 km wide fault segment, connecting the Elat Deep to the Aragonese Deep, which strikes N195°E and dips 65° to the west, with 2.1 m left‐lateral slip and a 15.5° rake indicating a slight normal component. The geodetic moment compares well with the seismic moment.
New constraints on the structure of the inner core from P’P’
Authors: Bréger Ludovic , Romanowicz Barbara , Rousset Sébastien
Published: February 2004

We measured absolute P’P’df as well as differential P’P’bc‐P’P’df and P’P’ab‐P’P’df travel time residuals for earthquakes in Alaska and the Aleutians recorded at NORSAR array (Norway). For such paths, P’P’df samples two regions of the inner core which have been identified as strongly anisotropic (∼3.5%), respectively beneath the Central Pacific and Africa, and should arrive some ∼6s earlier than predicted by a standard model. Absolute and differential travel times do not appear to be anomalous. A very complex texture and/or heterogeneity of the top ∼400km of the inner core, or a significant contribution from the strongly heterogeneous D”, is required to explain this discrepancy.
Radon‐222 monitoring of soil diffusivity
Authors: Lehmann Bernhard E. , Lehmann Martin , Neftel Albrecht , Tarakanov Sergei V.
Published: February 2004

The temporal evolution of activity profiles of the radon isotope 222Rn in the top 50 cm of soil is used to quantify diffusive gas transport in the air‐filled pore space. Air is continuously collected from gas‐permeable, hydrophobic membrane tubes placed at various depths under the surface and circulated through a high‐sensitivity Rn detector. With a micro‐processor controlled inlet system an automatic monitoring of several levels is possible for extended periods of time with a typical time resolution of one hour. In addition, a new dynamic approach to measure the in‐situ soil diffusivity Ds (m²/s) around the subsurface tubes is presented where the recovery from air injection is evaluated every 3 hours. Within a test period of 3 weeks Ds dropped from 10−6 m²/s to 3 10−7 m²/s at a depth of z=50 cm due to increasing water content of the soil.
Diffusion creep of fine‐grained garnetite: Implications for the flow strength of subducting slabs
Authors: Wang Zichao , Ji Shaocheng
Published: February 2004

Creep experiments were performed on synthetic fine‐grained garnetite to investigate the flow strength of the Earth's subducting slabs. Experiments were conducted at temperatures (T) of 1373–1543 K and total pressure (P) of 0.1 MPa in controlled atmospheres of fO2 =10−17‐10–8 MPa. The mechanical data indicate a grain‐size sensitive diffusion flow and the creep behavior can be described by an equation of the form: where T in Kelvin, d in meter, σ and fO2 in MPa. Based on the diffusivities (D) calculated from creep and diffusion experiments, we proposed that grain boundary diffusion is the dominant mechanism for high temperature creep of the fine‐grained garnetite. Normalized creep strength of the garnetite is found to be comparable to those of feldspar and olivine in diffusion creep regime, suggesting that garnetite may not form a strong layer in the subducted oceanic lithosphere if it deforms by grain boundary diffusion creep.
The Statistics of Helium Isotopes Along the Global Spreading Ridge System and the Central Limit Theorem
Authors: Anderson Don L.
Published: February 2004

An unbiased estimate of the arithmetic mean of the ³He/4He ratio (R) of basalts from the global spreading ridge system is 9.14 ± 3.59 Ra (n=503), where Ra is the atmospheric ratio and n is the number of data points. The ± two standard deviation (2σ) range covers much of the oceanic island and continental flood basalt data that have been attributed to ‘plume’ or ‘lower mantle’ components. The highest R values along the ridge system are associated with new ridges, backarc basins and near‐ridge seamounts. Low values are associated with long‐lived or abandoned ridges. The median, a more robust measure of the average, is 8.51 Ra.
Effects of planetary wave‐breaking on the seasonal variation of total column ozone
Authors: Nathan Terrence R. , Cordero Eugene C. , Li Long , Wuebbles Donald J.
Published: February 2004

The effects of planetary wave breaking on the seasonal variation of total column ozone are investigated using a zonally averaged chemical‐radiative‐transport model of the atmosphere. The planetary wave breaking effects of zonal wavenumbers k=1 and k=2 are significant in the middle latitude stratosphere during Northern Hemisphere (NH) winter, whereas only wave k=1 is important during Southern Hemisphere (SH) winter. The mixing and induced meridional circulation due to the planetary wave breaking increases the seasonal variation of total column ozone in NH (SH) middle latitudes by ∼20% (∼10%).
Sub‐surface nuclear tests monitoring through the CTBT Xenon Network
Authors: Hourdin Frédéric , Issartel J. ‐P.
Published: February 2004

We present the first evaluation of the atmospheric xenon network to be installed as part of the International Monitoring System (IMS) in the frame of the Comprehensive Test Ban Treaty (CTBT). We show that this network should, by itself, provide a significant contribution to the total efficiency of the IMS. For this evaluation, we introduce an inverse approach based upon the time symmetry of the atmospheric transport of trace species. This approach may find applications in a variety of environmental problems.
The influence of the pressure head on the Indonesian Seas circulation
Authors: Burnett William H. , Kamenkovich Vladimir M. , Mellor George L. , Gordon Arnold L.
Published: February 2004

A high resolution, regional, non‐linear, barotropic ocean model (2D POM) was used to show that a pressure difference between the Pacific and Indian Ocean does not significantly influence the total transport of the Indonesian throughflow.
A mechanism for the influence of vegetation on the response of the diurnal temperature range to changing climate
Authors: Collatz G. James , Bounoua L. , Los S. O. , Randall D. A. , Fung I. Y. , Sellers P. J.
Published: February 2004

We propose a new mechanism that could contribute to the observed decrease in the diurnal temperature range (DTR) over the last century: the physiological behavior of vegetation in response to climate. Using a physiologically based land surface model, we analyze the influence of vegetation on the response of the DTR to perturbations in the state of the climate and vegetation. Increasing down‐welling long wave radiation and surface air temperature together, conditions that could occur as a result of doubling of atmospheric CO2, produced little change in the DTR. Changes in the state of the vegetation (i.e. amount, physiological capacity, stress) produce changes in the DTR of the order or larger than observed. Results emphasize that DTR modeling studies need to consider vegetation responses and suggest that recently reported increases in vegetation over the last decade could contribute to the observed decreases in the DTR.
Excitation process of infrasonic waves associated with Merapi‐type pyroclastic flow as revealed by a new recording system
Authors: Oshima Hiromitsu , Maekawa Tokumitsu
Published: February 2004

We investigate excitation process of the infrasonic waves associated with Merapi‐type pyroclastic flows at Unzen volcano, Japan, using data set obtained by a new system that permits recording of geophysical data with accompanying visual events on a single videotape. The accurate correlation of infrasonic waves with video images reveals that: (1) successive impulsive waves and the low‐frequency wave (<∼0.8Hz) are excited during the collapse of lava blocks falling from the dome, which generates a pyroclastic flow; (2) an impulsive wave is excited by an explosive blowout of the pore‐gases which are released by the breakdown of the falling blocks; (3) the low‐frequency wave is excited by the volumetric change which results from expansion of the pore‐gases released by pulverization of the falling blocks. The comparison between the observed and the synthetic low‐frequency waves shows that the amount of volume change is about 2 times that of the initial falling blocks.
A multiwavelength investigation of the ring effect in the day sky spectrum
Authors: Pallamraju D. , Baumgardner J. , Chakrabarti S.
Published: February 2004

Ring effect refers to the ‘filling‐in‧ of the Fraunhofer absorption lines in the day sky spectrum as compared to the solar spectrum. Rotational Raman scattering is believed to be the main cause for this excess in the sky spectrum. Earlier measurements showed contradictory behavior of this effect with solar zenith angle and wavelength. It is important to take proper account of this effect as it otherwise results in overestimating the dayglow emission intensities and underestimating the number densities of atmospheric trace gases. The present study details the results obtained from a simultaneous 11‐wavelength investigation carried out using a newly built daytime spectrograph. This data demonstrates that the absorption line strength (normalized depth × half width) has a major control on the Ring effect contribution irrespective of the solar zenith angle and the wavelength.
Influence of the ocean loading effect on GPS derived precipitable water vapor
Authors: Dach Rolf , Dietrich Reinhard
Published: February 2004

For meteorology the precipitable water vapor becomes a more and more important product in the data analysis of the Global Positioning System (GPS). It is derived from the wet part of the tropospheric refraction obtained as zenith path delay in the data analysis. However, the estimates of the zenith path delay and of the station height are strongly correlated. The ocean loading effect has a periodic influence on station heights with major frequencies in the diurnal and semidiurnal band and with amplitudes up to several centimeters. If one ignores this effect it affects the estimates of the zenith path delay and thus the precipitable water vapor. This will be demonstrated by some examples.
A balanced nitrogen budget of the surface layer of the southern Ross Sea, Antarctica
Authors: Smith Walker O. , Asper Vernon A.
Published: February 2004

To understand marine biogeochemical cycles, it is critical to quantitatively balance organic matter transformations within the euphotic zone. Such an assessment for nitrogen is difficult because of lateral advection, uncertainties in individual measurements, the complexity of elemental transformations (including nitrification and denitrification), and the difficulty of collecting data on appropriate space and time scales. Two cruises were conducted to the southern Ross Sea, Antarctica, to understand the time‐varying fluxes of nitrogen into its various pools. From these data a balanced inventory was constructed. Nitrate removal in the upper 200 m was balanced by particulate and dissolved organic nitrogen production, ammonification, and vertical flux. In austral spring nearly all (92%) of the new production remained as particulate nitrogen, but this percentage decreased markedly (52%) by mid‐summer, when nitrogen regeneration, PN flux, and DON production were 23, 13 and 12% of net production, respectively. The organic matter budget in this coastal Antarctic site is dominated by particle transformations.
Photochemical regimes in urban atmospheres: The influence of dispersion
Authors: Honoré Cécile , Vautard Robert , Beekmann Matthias
Published: February 2004

The dependence on emissions of urban photochemistry is studied under meteorological conditions favouring pollution episodes. We use a simple chemistry‐transport model, yet realistic with respect to the main chemical and physical processes and considering the diurnal cycle of forcing parameters. For a range of NOx emissions, the diurnal equilibria of the system are searched for. It is shown that, if the photochemistry over a large city mostly exhibits a negative sensitivity to NOx emissions, there are meteorological situations under which it becomes (positively) NOx sensitive, the dispersion time scale being a key parameter. We show that, under specific conditions, the urban atmosphere might reach two very different diurnal equilibria. We demonstrate that the sensitivity to NOx emissions evolves with time: under specific conditions, the urban atmosphere becomes NOx sensitive within two days.
Simultaneous inversion for temperature and water vapor from IMG radiances
Authors: Lubrano Alberta M. , Serio C. , Clough Shepard A. , Kobayashi H.
Published: February 2004

Simultaneous retrieval of temperature and water vapor profiles have been obtained by using spectral radiances from the Japanese IMG high resolution interferometer spectrometer. Forward model computations have been performed with the LBLRTM code. The spectral residuals between the IMG measurements and the LBLRTM radiative transfer model are dominated by uncertainty in the IMG spectral instrument function. The impact of these residuals on the retrievals has been significantly mitigated though an approach using reduced resolution.
Simulation of ocean temperature change due to the opening of Drake Passage
Authors: Nong Giang T. , Najjar Raymond G. , Seidov Dan , Peterson William H.
Published: February 2004

An ocean general circulation model (GCM) is used to test the hypothesis that the opening of Drake Passage in the Oligocene may have lead to cooling in southern high latitudes. Results of previous studies show that no ocean models using restoring boundary conditions for the surface heat flux could reveal substantial southern high latitude cooling without prescribing atmospheric cooling a priori. To compute the surface heat flux that would be free from the restoring constraints we use another method, which is derived from an atmospheric energy balance model with lateral heat transport. In experiments conducted with both idealized and realistic topography the energy balance method produces substantial cooling not only in high latitudes but in deep waters as well.
An estimate of the eddy‐induced circulation in the Labrador Sea
Authors: Khatiwala Samar , Visbeck Martin
Published: February 2004

Regions of oceanic deep convection such as the Labrador Sea are prone to baroclinic instability. The resulting geostrophic eddies play a crucial role in the post‐convection adjustment process which involves both rearrangement of mass so as to release available potential energy and exchange of heat and salt with the boundaries. In this study it is proposed that the slumping of isopycnals associated with baroclinic instability drives an eddy‐induced “overturning circulation” consisting of a surface intensified flow transporting low salinity water from the boundary currents into the interior; sinking motion in the interior; and an “outflow” at depth transporting newly ventilated Labrador Sea Water towards the boundaries. Typical eddy‐induced velocities estimated from hydrographic data are roughly 0.5 cm/s for the surface inflow, 1 m/day for the vertical motion, and 0.1 cm/s for the deeper outflow, in close agreement with those calculated in a numerical model.
Thermophysical properties of Alaskan loess: An analog material for the Martian polar layered terrain?
Authors: Johnson Jerome B. , Lorenz Ralph D.
Published: February 2004

The Martian surface has several regions where thermal inertia measurements indicate a porous ice‐free insulating surface, yet are mechanically competent enough to sustain substantial slopes. In support of the interpretation of those regions within the Martian polar layered terrain, we report measurements of thermal conductivity for loess from the field and in the USA CRREL Permafrost Tunnel. Permafrost Tunnel loess is a desiccated material that can form vertical walls, but is of low density (800–1000 kg/m³), modest shear strength (4 kPa), and has a low thermal conductivity (0.1 W/m‐K at 1 bar). These properties are similar to the inferred properties of the Martian polar layered terrain. The Birch Hill field sample has a density of 1160 kg/m³ and a conductivity of 0.15 W/m‐K. The Chena Spur Road sample has a density of 1360 kg/m³ and a conductivity of 0.7 W/m‐K. The relatively high conductivity for the Chena Spur Road is due to the cementation of soil grain contacts, its higher density, coarser grain size, and higher quartz grain content.
Bias correction of an ocean‐atmosphere coupled model
Authors: Chen Dake , Cane Mark A. , Zebiak Stephen E. , Cañizares Rafael , Kaplan Alexey
Published: February 2004

A serious problem in the initialization of a climate forecast model is the model‐data incompatibility caused by systematic model biases. Here we use the Lamont model to demonstrate that these biases can be effectively reduced with a simple statistical correction, and the bias‐corrected model can have a more realistic internal variability as well as an improved forecast performance. The results reported here should be of practical use to other ocean‐atmosphere coupled models for climate prediction.
Simulation of eddy‐driven phytoplankton production in the Black Sea
Authors: Oguz Temel , Salihoglu Baris
Published: February 2004

A three dimensional, three‐layer biological model is used to assess impact of eddy‐dominated horizontal circulation on the spatial and temporal variations of plankton biomass in the Black Sea. Simulations are shown to exhibit patchy distributions of phytoplankton biomass as inferred from satellite images, and their intensities agree reasonably well with observations. Overall performance of the three layer model points to its potential capability as a practical alternative tool to more complex and computationally expensive multi‐level models, without sacrificing much from the basics of the ecosystem dynamics.
Forecasts of tropical Pacific SST and sea level using a Markov model
Authors: Xue Yan , Leetmaa Ants
Published: February 2004

A seasonally varying Markov model is constructed in a multivariate EOF space of observed SST and sea level analysis for 1981–98. The hindcast skill of SST and sea level is estimated with a cross‐validation scheme. For SST, the correlation skill is highest in the central‐eastern equatorial Pacific at about 0.5 at 9 month lead. The Markov model has a marginal SST forecast skill at 3 month lead (>0.4) in the north‐western Pacific (NWP) around 10°N. For sea level, the correlation skill is highest in the central equatorial Pacific and the NWP around 10°N at above 0.5 at 9 month lead. In the western Pacific, sea level anomalies are generally more predictable than SST anomalies. The real time forecast of sea level by the Markov model is available at the official web site of the Climate Prediction Center, NOAA (http://www.cpc.ncep.noaa.gov/pacdir).
Change of crustal potential energy by earthquakes: An indicator for extensional and compressional tectonics
Authors: Tanimoto Toshiro , Okamoto Taro
Published: February 2004

Earthquakes cause a potential energy change in Earth's interior because they generate permanent vertical deformation in the gravitational field. The cumulative change of this potential energy in the crust, computed for the period between 1977 and 1998, shows systematic patterns in various tectonic provinces. Regions of extensional tectonics show systematic potential energy loss and regions of compressional tectonics typically show energy gain. Therefore, we claim that the crustal potential energy change can serve as a good indicator of compressional and extentional tectonics.
Monitoring fracture evolution with compressional‐mode interface waves
Authors: Pyrak‐Nolte Laura J. , Roy Sanjit
Published: February 2004

As a tensile fracture was induced in a sandstone core sample under compressional loading, compressional waves were propagated parallel to the plane of tensile stress. Long before catastrophic failure, when a macroscopic fracture was formed, the energy in the compressional wave showed a dramatic shift in spectral frequency from 0.644 MHz to 1 MHz. This frequency shift is a signature of the partitioning of energy from a compressional body wave into a compressional‐mode interface wave. The presence of this signature before failure suggests the presence of an incipient interface wave that is supported by a network of oriented but disconnected microcracks.
Do the 1998 Antarctic Plate earthquake and its aftershocks delineate a plate boundary?
Authors: Conder James A. , Forsyth Donald W.
Published: February 2004

Plate motion data along the eastern Southeast Indian Ridge (SEIR) are not fit by a rotation pole consistent with data along the western SEIR. DeMets et al. (1988) looked for, but did not find, evidence of a microplate north of the SEIR to explain the discrepancy. We test the hypothesis that the large (Mw=8.2), strike‐slip, 1998 Antarctic earthquake lies on the boundary of a microplate (here termed “Balleny”) south of the SEIR that explains the plate motion discrepancy. A small circle about an Antarctic‐Balleny Euler pole, determined by plate closure, fits the east‐west band of aftershocks, consistent with a strike‐slip boundary. However, the Antarctic‐Balleny pole predicts right‐lateral slip, while the seismicity exhibits left‐lateral, strike‐slip motion. The opposite sense of slip not only rules out the Balleny plate hypothesis, but requires deformation elsewhere to accommodate both the plate motion differences along the SEIR and the strain accumulated from the Antarctic event.
Lithospheric and upper mantle structure of the Indian Shield, from teleseismic receiver functions
Authors: Saul Joachim , Kumar M. Ravi , Sarkar Dipankar
Published: February 2004

Receiver functions derived from teleseismicPwaveforms of 297 earthquakes recorded at broadband station Hyderabad (HYB) are analysed to investigate the lithospheric and upper mantle structure in the vicinity of the station, located in the northeastern part of the Archaean Dharwar Craton. The internal structure of the 33±2 km thick crust is simple. It can be approximated by a single layer withSvelocity linearly increasing with depth from 3.4 to 4.0 km/s, the average being 3.7±0.2 km/s. The crustal Poisson's ratio is 0.25±0.01. A seismic discontinuity at 90 km depth is inferred from a signal particularly prominent on the SH component and possibly indicative of a layer of depth‐localized anisotropy in the lithospheric mantle. The two principal mantle discontinuities are at depths of 406 and 659 km, which are close to the global averages.
Did stress triggering cause the large off‐fault aftershocks of the 25 March 1998 Mw=8.1 Antarctic Plate earthquake?
Authors: Toda Shinji , Stein Ross S.
Published: February 2004

The 1998 Antarctic plate earthquake produced clusters of aftershocks (Mw≤6.4) up to 80 km from the fault rupture and up to 100 km beyond the end of the rupture. Because the mainshock occurred far from the nearest plate boundary and the nearest recorded earthquake, it is unusually isolated from the stress perturbations caused by other earthquakes, making it a good candidate for stress transfer analysis despite the absence of near‐field observations. We tested whether the off‐fault aftershocks lie in regions brought closer to Coulomb failure by the main rupture. We evaluated four published source models for the main rupture. In fourteen tests using different aftershocks sets and allowing the rupture sources to be shifted within their uncertainties, 6 were significant at ≥ 99% confidence, 3 at > 95% confidence, and 5 were not significant (< 95% level). For the 9 successful tests, the stress at the site of the aftershocks was typically increased by 1–2 bars (0.1–0.2 MPa). Thus the Antarctic plate event, together with the 1992 Mw=7.3 Landers and its Mw=6.5 Big Bear aftershock 40 km from the main fault, supply evidence that small stress changes might indeed trigger large earthquakes far from the main fault rupture.
A key source area and constraints on entrainment for basin‐scale sediment transport by Arctic sea ice
Authors: Eicken Hajo , Kolatschek Josef , Freitag Johannes , Lindemann Frank , Kassens Heidemarie , Dmitrenko Igor
Published: February 2004

Combining field measurements, remote sensing and numerical modelling, a key site for ice entrainment and basinwide dispersal of sediments by sea ice has been identified near the New Siberian Islands. The total ice‐bound sediment export of 18.5 × 106 t for an entrainment event documented in 1994/95 is of the same order of magnitude as annual sediment supply to the deep sea sector of the Eurasian Arctic and the Greenland Sea. Satellite imagery and ancillary data indicate that ice advection from this source may play an important role in sedimentation downstream in the Transpolar Drift.
Possible splay fault slip during the 1946 Nankai earthquake
Authors: Cummins Phil R. , Kaneda Yoshiyuki
Published: February 2004

This paper considers seafloor deformation associated with the 1946 Nankai earthquake, which occurred in the Nankai Trough subduction zone off the coast of southwest Japan. We note that recent high‐resolution determinations of the slip distribution, assumed to be confined to the plate boundary, result in a pronounced maximum in seafloor displacement midway between the coast of Shikoku and the trough axis. We show that this feature could be due to slip on a splay fault rather than the plate boundary. Such a model for the western part of the slip distribution is able to account for the main features of the tsunamigenic seafloor deformation obtained in previous studies, with a maximum slip consistent with the plate convergent rate and history of earthquake recurrence at the Nankai Trough.
Effects of hyperdiffusivities on dynamo simulations
Authors: Grote E. , Busse F. H. , Tilgner A.
Published: February 2004

A comparison of stationary and time periodic convection driven spherical dynamos computed with and without the use of hyperdiffusivities is presented.
Observation of stratospheric ozone depletion associated with Delta II rocket emissions
Authors: Ross M. N. , Toohey D. W. , Rawlins W. T. , Richard E. C. , Kelly K. K. , Tuck A. F. , Proffitt M. H. , Hagen D. E. , Hopkins A. R. , Whitefield P. D. , Benbrook J. R. , Sheldon W. R.
Published: February 2004

Ozone, chlorine monoxide, methane, and submicron particulate concentrations were measured in the stratospheric plume wake of a Delta II rocket powered by a combination of solid (NH4ClO4/Al) and liquid (LOX/kerosene) propulsion systems. We apply a simple kinetics model describing the main features of gas‐phase chlorine reactions in solid propellant exhaust plumes to derive the abundance of total reactive chlorine in the plume and estimate the associated cumulative ozone loss. Measured ozone loss during two plume encounters (12 and 39 minutes after launch) exceeded the estimate by about a factor of about two. Insofar as only the most significant gas‐phase chlorine reactions are included in the calculation, these results suggest that additional plume wake chemical processes or emissions other than reactive chlorine from the Delta II propulsion system affect ozone levels in the plume.
An empirical model of the ionospheric electric potential
Authors: Ridley A. J. , Crowley G. , Freitas C.
Published: February 2004

We present an empirical model of the ionospheric electric potential based on output from the assimilative mapping of ionospheric electrodynamics technique (AMIE). The model is derived using a multivariable linear regression analysis technique to relate the potential at each grid point to the interplanetary magnetic field Byand Bzcomponents. AMIE output over a one week period was used to construct the model. The results of the model are very similar to other electric potential models; namely, the background pattern and the model response to Byand Bzare typical. The unique aspect of this model is the use of the linear response to changes in IMF for the forward prediction of the potential pattern. We show an example of how the model can significantly improve predictions of the potential when it is coupled to a real‐time specification model such as the real‐time version of AMIE.
Interannual changes of total ozone and northern hemisphere circulation patterns
Authors: Steinbrecht W. , Claude H. , Köhler U. , Winkler P.
Published: February 2004

Linear regression accounting for the quasi‐biennial oscillation, the 11‐year solar cycle, stratospheric volcanic aerosol loading, and a long‐term trend, accounts for 53% of the interannual ozone variance observed in February at Hohenpeissenberg (48°N, 11°E). When tropospheric circulation patterns are added to the regression, a substantially larger fraction (81%) of the observed total ozone variance can be described. The Polar Eurasia circulation pattern, negative anomalies of tropospheric geopotential height over Greenland and Arctic Canada coupled to opposite anomalies over Central Europe and North‐Eastern China, is essential in accounting for interannual variations of February total ozone at Hohenpeissenberg. A large part (≈ 25%) of the February long‐term ozone decline at Hohenpeissenberg appears to be related to a more frequent positive phase of this pattern. Circulation could influence ozone directly through transport, or indirectly enhance Arctic chemical ozone depletion through cold temperatures. Since climate change in the northern hemisphere winter manifests itself in a pattern very similar to the Polar Eurasia pattern, this study gives a strong indication that climate change might affect the stratospheric ozone layer.
Statistics of momentum flux estimation using the dual coplanar beam technique
Authors: Thorsen Denise , Franke Steven J. , Kudeki Erhan
Published: February 2004

We examine the statistical estimation error for the dual coplanar beam momentum flux estimator in the presence of geophysical noise. Included in our derivation are the effects of measurement noise and finite spatial correlation of the wind fluctuations. We show that there is an optimal beam separation that minimizes the statistical estimation error at a value nearly equal to the irreducible error observed by an “ideal” anemometer measuring u and w at a point. For typical mesopause parameters this beam separation is approximately ±13°. The optimal angle is dependent in part on the ratio of vertical to horizontal wind variances and is therefore variable. For optimal momentum flux measurements a system, radar or lidar, with steerable beams becomes necessary.
A new theory of heterogeneous ice nucleation for application in cloud and climate models
Authors: Khvorostyanov Vitaly I. , Curry Judith A.
Published: February 2004

A new formulation is presented of the thermodynamical theory of heterogeneous ice crystal nucleation in clouds by freezing. This theory unifies and explains the empirical ice nuclei dependence on temperature and supersaturation, predicts crystal formation via condensation‐freezing at a subsaturation over water. The theory also explains observations of high nucleation rates and crystal concentrations at warm (−5 > −12°C) temperatures when the splintering mechanism may be not effective. This theory can be applied to parameterizations for use in cloud and climate models.
Comparison of measured and modeled stratospheric BrO: Implications for the total amount of stratospheric bromine
Authors: Harder H. , Bösch H. , Camy‐Peyret C. , Chipperfield M. P. , Fitzenberger R. , Payan S. , Perner D. , Platt U. , Sinnhuber B.‐M. , Pfeilsticker K.
Published: February 2004

Stratospheric BrO was spectroscopically monitored by its UV absorption in direct sunlight on 8 balloon flights that were conducted at middle and high latitudes in 1996 through 2000 [e.g., Ferlemann et al.,1998, 2000]. For conditions where detailed photochemical model calculations [Chipperfield, 1999] correctly predict other measured chemical (e.g., NO2, O3) and dynamical (e.g. N2O, F12, et cetera) tracers, the total stratospheric bromine (organic and inorganic) amount (Bry) is inferred. An excellent agreement between measured and modeled stratospheric BrO is found, assuming JPL‐97 kinetics and Bry=20 ppt in the photochemical model. As the BrO absorption cross section (σBrO) is the only external parameter used in the measurement, our finding tightly constrains the amount of total inorganic bromine (Bryin), 20±2.5 ppt above 25 km in 1996/97, as well as the photochemistry of stratospheric bromine.
Inertia‐gravity waves associated with the tropical easterly jet over the Indian subcontinent during the South West Monsoon Period
Authors: Sasi M. N. , Ramkumar Geetha , Deepa V. , Murthy B. V. Krishna
Published: February 2004

Using the MST radar located at Gadanki (13.5°N, 79.2°E) winds were measured every four hours in the troposphere and lower stratosphere during a 72‐hour period from 23 to 26 September 1997 when the tropical tropospheric easterly jet (TEJ) was present south of Gadanki with its core at a height of ∼16 km. Analysis of the radar data shows the presence of ∼56 hour oscillations (close to local inertial period of ∼51 hours) in the wind components with significant amplitudes. Examination of the corresponding horizontal wind vector shows clockwise rotation with altitude (upward energy propagation) in an altitude region (17.7–20.8 km) above the TEJ and anticlockwise rotation (downward energy propagation) in another altitude region (8.3–10.5 km) below. This indicates the generation of Inertia Gravity Waves (IGW) in the TEJ and their propagation both upwards and downwards from the source region. The inferred vertical and horizontal wavelengths of the IGW are ∼0.7 and ∼75 km respectively in the stratosphere and ∼1 and ∼143 km respectively in the troposphere.
Climatology and seasonal variability of ocean fronts in the East China, Yellow and Bohai seas from satellite SST data
Authors: Hickox Ryan , Belkin Igor , Cornillon Peter , Shan Zhengqiang
Published: February 2004

Front detection and declouding algorithms developed at the URI have been applied to the 12‐year (1985–1996) Pathfinder SST data set to produce the first comprehensive, objectively derived, year‐round climatology of ocean thermal fronts in the eastern China Seas, from 24°N to 41°N. Ten fronts have been distinguished, namely Kuroshio, Zhejiang‐Fujian, Jiangsu, Shandong Peninsula, Bohai Sea, Seohan Bay, Kyunggi Bay, Western and Eastern Chejudo (South Korean Coastal Front), and Yangtze Bank Ring Front. The fronts are seasonally persistent: they emerge and disappear in the same seasons of different years. The frontal pattern remains fairly stable from one year to another, whereas individual fronts display different modes of seasonal variability.
Forecasting the SST Space‐time variability of the Alboran Sea with genetic algorithms
Authors: Álvarez Alberto , López Cristóbal , Riera Margalida , Hernández‐García Emilio , Tintoré Joaquín
Published: February 2004

We propose a nonlinear ocean forecasting technique based on a combination of genetic algorithms and empirical orthogonal function (EOF) analysis. The method is used to forecast the space‐time variability of the sea surface temperature (SST) in the Alboran Sea. The genetic algorithm finds the equations that best describe the behaviour of the different temporal amplitude functions in the EOF decomposition and, therefore, enables global forecasting of the future time‐variability.
Modeling recent climate variability in the Arctic Ocean
Authors: Maslowski W. , Newton B. , Schlosser P. , Semtner A. , Martinson D.
Published: February 2004

Dramatic changes in the circulation of sea ice and the upper layers of the Arctic Ocean have been reported during the last decade. Similar variability is modeled using a regional, coupled ice‐ocean model. Realistic atmospheric forcing fields for 1979–93 are the only interannual signal prescribed in the model. Our results show large‐scale changes in sea ice and oceanic conditions when comparing results for the late 1970s/early 1980s and the 1990s. We hypothesize that these changes are in response to even larger scale atmospheric variability in the Northern Hemisphere that can be defined as either the Arctic Oscillation or the North Atlantic Oscillation. Agreement between the direction and scale of change in the model and observations, in the absence of interannual forcing from the global ocean thermohaline circulation, suggests that the atmospheric variability by itself is sufficient to produce basin‐scale changes in the Arctic Ocean and sea ice system.