bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyzing absolute paleointensity determinations: Acceptance criteria and the software ThellierTool4.0
Authors: Leonhardt R. , Heunemann C. , Krása D.
Published: January 2005

The ThellierTool4.0 is an intuitive and easy‐to‐use software which provides the possibility to analyze a wide range of different modifications of the Thellier absolute paleointensity experiment (available at http://earthref.org/tools/). Besides the Arai plot for paleointensity determination, orthogonal projections of the direction, decay of NRM during thermal demagnetization, and additional plots regarding alteration and multidomain checks enable the user to visualize the quality of individual determinations. Experimental checks for magnetomineralogical changes, either in‐field or zero‐field pTRM* checks, are evaluated regarding their differences to the corresponding pTRM* acquisition in two most commonly used ways. Furthermore, a measure for the cumulative alteration differences beginning at room temperature is calculated, and the possibility to correct for magnetomineralogical changes is provided. Two different experimental methods to check for multidomain bias are supported and analyzed by the software. Intensity differences recorded by pTRM*‐tail checks are calculated. Accounting for the directional difference between applied laboratory field and magnetization of the sample, the effective pTRM*‐tail is determined, and thus failures of Thellier's law of independence are monitored. Failures of the law of additivity, experimentally observed by additivity checks, are also evaluated by the software. The vectorial character of individual measurements is fully considered for all calculations. Uniform selection criteria for acceptance and rejection of determinations can be applied, and a set of such criteria with emphasis on minimal bias due to alteration, multidomain remanence, and analysis/experimental inaccuracies is suggested.
Mg/Ca ratios of the benthic foraminifera Oridorsalis umbonatus obtained by laser ablation from core top sediments: Relationship to bottom water temperature
Authors: Rathmann Söhnke , Hess Silvia , Kuhnert Henning , Mulitza Stefan
Published: January 2005

A laser ablation system connected to an inductively coupled plasma mass spectrometer was used to determine Mg/Ca ratios of the benthic foraminifera Oridorsalis umbonatus. A set of modern core top samples collected along a depth transect on the continental slope off Namibia (320–2300 m water depth; 2.9° to 10.4°C) was used to calibrate the Mg/Ca ratio against bottom water temperature. The resulting Mg/Ca–bottom water temperature relationship of O. umbonatus is described by the exponential equation Mg/Ca = 1.528*e0.09*BWT. The temperature sensitivity of this equation is similar to previously published calibrations based on Cibicidoides species, suggesting that the Mg/Ca ratio of O. umbonatus is a valuable proxy for thermocline and deep water temperature.
Trace element cartography of Globigerinoides ruber shells using particle‐induced X‐ray emission
Authors: Gehlen M. , Bassinot F. , Beck L. , Khodja H.
Published: January 2005

Micro particle‐induced X‐ray emission (PIXE) is a nondestructive elemental analysis technique that can be used to map the distribution of elements with a spatial resolution of ±4 μm2 and a penetration depth of ±2 μm in a calcite matrix. To test its potential to improve our understanding of trace element distribution in foraminifera shells, we mapped the Mg distribution across individual chambers of the planktonic species Globigerinoides ruber. G. ruber shells were picked from equatorial Atlantic surface sediments (Sierra Leone Rise). They ranged from well‐preserved to heavily dissolved tests. The mapping of trace elements across test chambers made it possible to discriminate between variability inherent to the shell material and heterogeneity linked to contaminant phases. Contaminating mineral phases were characterized by high Mg concentrations (Mg/Ca = 19.7 mmol/mol) and high levels of Si, Al, and Fe. Mg/Ca values of well‐preserved shells ranged from 3.9 to 4.5 mmol/mol. The Mg to Ca ratios of partially dissolved shells varied between 1.8 and 3.4 mmol/mol between outer and inner chambers. Low and homogeneous Mg/Ca values of 2.0 and 2.3 mmol/mol were determined for chambers of a severely dissolved test.
Characteristic scale of convective organization and monsoon intensity
Authors: Goswami P. , Patra G. K.
Published: January 2005

Many aspects of the inter‐annual variability of the Indian summer monsoon (ISM) remain unexplained. While boundary forcing like SST, snow cover and land surface processes are known to play significant roles, they cannot explain all of the inter‐annual variability of ISM. We identify and show that nature and organization of dynamics play a critical role in the intensity, and hence the variability of ISM. Investigation using a 55‐year dataset from NCEP at different scales and locations clearly shows a sharp contrast in organized convergence at a scale of 20° between excess and deficit monsoon years; the deficit monsoon years, including 2002, are marked by suppressed organized convergence. The general conclusions are valid even in presence of moist convergence, indicating that it is the efficient organization through convergence that plays a critical role in monsoon intensity. The results thus provide new insight into the dynamics and simulation of monsoon.
Orographic influences on the annual cycle of Namibian stratocumulus clouds
Authors: Richter I. , Mechoso C. R.
Published: January 2005

The impact of African orography on the persistence and seasonal cycle of Namibian stratocumulus is examined in the context of an atmospheric general circulation model. A control simulation with realistic orography and simulated stratocumulus is compared to a sensitivity experiment, in which African orography is removed. In the absence of orography, stratocumulus incidence off the Namibian and Angolan coast is significantly reduced during austral winter and spring. It is argued that through the combined effects of obstruction and deflection of atmospheric flow, orography acts to enhance static stability of the lower troposphere over the Atlantic off the Namibian coast, which provides an environment conducive to the development of stratocumulus in that region.
The May 17, 1992 earthquakes in southeastern Philippines
Authors: Besana G. M. , Tanioka Y. , Ando M. , Mirabueno M. H. , Manahan J. , De Ocampo J. , Perez J. , Bautista B.
Published: January 2005

Two large earthquakes (Q1 and Q2) occurred off the eastern coast of Mindanao along the Philippine Trench on May 1992. During these events, the southeastern coasts of the island experienced one strong ground shaking and suffered from one set of tsunamis waves. To investigate this phenomenon, teleseismic body wave inversions and tsunami waveform analysis were undertaken for the quakes. Correlation of simulation results and field observations show that Q1 was the most probable source of the damaging tsunami wave. Results also imply that the relation between the Q1 and Q2 that may have ruptured the southern and northern portion of the one‐day aftershock area, respectively. Furthermore, closer examination of the Philippine trench indicates the presence of a bend in between the events that could have prevented the Q1 to rupture in just one big event.
BrO emission from volcanoes: A survey using GOME and SCIAMACHY measurements
Authors: Afe Oluyemi T. , Richter Andreas , Sierk Bernd , Wittrock Folkard , Burrows John P.
Published: January 2005

Volcanic eruptions are known to be a major source of SO2 and some reactive halogen species notably HCl and HF. Recent studies have however observed the presence of large amounts of BrO with tight correlation to SO2 in a volcanic plume by ground‐based spectroscopic measurements. In this work, upper limits of BrO columns have been estimated for a number of volcanic eruptions observed in measurements made by two satellite instruments ‐ the Global Ozone Monitoring Experiment (GOME), and the new SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The results obtained for the eruptions covered by satellite overpasses over the Etna, Nyamuragira, Popocatépetl, and Reventador volcanoes show no correlation between enhanced volcanic SO2 during large eruptions and the corresponding BrO columns. Evidence for BrO enhancement was also not found in the vicinity of the Soufrière Hills volcanoes. The possible reasons for the differences between ground‐based and satellite observations are considered.
Tidal perturbations and variability in the mesopause region over Fort Collins, CO (41N, 105W): Continuous multi‐day temperature and wind lidar observations
Authors: She C. Y. , Li Tao , Collins Richard L. , Yuan Tao , Williams Bifford P. , Kawahara Takuya D. , Vance Joe D. , Acott Phil , Krueger David A. , Liu Han‐Li , Hagan Maura E.
Published: January 2005

An unusually long data set was acquired at the sodium lidar facility at Colorado State University (41N, 105W), between Sep 18 and Oct 01, 2003, including a 9‐day continuous observation. This time is long enough to average out the perturbations of gravity waves and short‐period planetary waves. As such, it can be used to define tidal‐period perturbations in temperature and horizontal wind. Assuming the sodium mixing ratio is a constant of motion, the observed tidal‐period oscillation in sodium density follows that of vertical wind. Thus, the data set defines tidal‐period perturbations of temperature and wind vector. The observed amplitudes and phases were compared to Global Scale Wave Model predictions (both GSWM00 and GSWM02). We found excellent agreement in diurnal phases and reasonable agreement in semidiurnal phases. However, GSWM02 overestimates diurnal amplitudes and both model versions underestimate observed semidiurnal amplitudes. Since the data period is long enough for the study of planetary waves and of tidal variability, we perform spectral analysis of the data, revealing a strong quasi 3‐day wave in meridional wind, a 14 hour perturbation in zonal wind, and both 14‐hour and 10‐hour periods in meridional wind, likely the result of nonlinear interactions. The observed semidiurnal amplitudes are much larger than the corresponding diurnal amplitudes above 85 km, and over a few days the diurnal and semidiurnal amplitudes vary by factors of 2–3. Causes for the observed tidal variability in terms of planetary wave modulation and tide‐gravity wave interaction are explored qualitatively.
Multi‐fluid simulations of Ganymede's magnetosphere
Authors: Paty Carol , Winglee Robert
Published: January 2005

Comparative studies of 3D multi‐fluid simulations with Galileo magnetometer data are used to develop a quantitative model of the currents and fields within Ganymede's magnetosphere as well as its bulk plasma environment. The model includes contributions from Jupiter's magnetosphere and the flux of different ion species originating from Ganymede's ionosphere. Comparisons between the magnetometer data and the simulation demonstrate good agreement for the strength and structure of Ganymede's magnetosphere. An ionospheric outflow rate of ∼1026 ions/s was found for the simulation, which is well correlated to the sputtering rate determined for the surface of Ganymede that actively supplies the ionosphere. Qualitative comparisons are made with the Hubble Space Telescope observations of Ganymede's UV aurora. The size and location of regions of Jovian magnetospheric plasma precipitation are similar to the observed UV emissions. Plasma acceleration due to reconnection and the size of Ganymede's cusps are also examined.
An intermediate deep earthquake rupturing on a dip‐bending fault: Waveform analysis of the 2003 Miyagi‐ken Oki earthquake
Authors: Wu Changjiang , Takeo Minoru
Published: January 2005

Using waveform analysis, we propose a dip‐bending fault model for the 2003 Miyagi‐ken Oki earthquake. Dip angle of the upper fault plane is estimated as 87° on the basis of focal mechanism from P‐wave first motions. S‐wave polarization analysis leads to a dip angle of 60° for the lower portion of the fault plane. Inversion results show that the rupture started on the southern fault plane. In the beginning 5 seconds, slip was mainly confined in the hypocenter area on the southern fault. From 5 seconds on rupture propagated to the northern part, where the largest slip (3 m) occurred in the northern deep part. The complex stress field in the slab and compositional difference in the upper and the other portion of the slab account for such a bending fault even at intermediate depth.
Tall precipitation cells in tropical cyclone eyewalls are associated with tropical cyclone intensification
Authors: Kelley Owen A. , Stout John , Halverson Jeffrey B.
Published: January 2005

The association of tall precipitation with tropical cyclone intensification may have implications for the difficult task of forecasting the destructive potential of tropical cyclones. This study uses all of the well‐centered overflights of tropical cyclones from 1998 to 2003 seen by the TRMM Precipitation Radar. The chance of intensification increases when one or more extremely tall convective towers exist in the tropical cyclone's eyewall. We define an extremely tall convective tower as a convective cell with a 20 dBZ reflectivity signal that reaches an altitude of at least 14.5 km. In addition, we adapt this radar technique for use with more plentiful infrared and passive microwave data.
Global measurement of the mesospheric sodium layer by the star occultation instrument GOMOS
Authors: Fussen D. , Vanhellemont F. , Bingen C. , Kyrölä E. , Tamminen J. , Sofieva V. , Hassinen S. , Seppälä A. , Verronen P. , Bertaux J.‐L. , Hauchecorne A. , Dalaudier F. , Renard J.‐B. , Fraisse R. , Fanton d'Andon O. , Barrot G. , Mangin A. , Théodore B. , Guirlet M. , Koopman R. , Snoeij P. , Saavedra L.
Published: January 2005

We present the first global measurement of the sodium mesospheric layer obtained from the processing of about 100 000 star occultations by the GOMOS instrument onboard the ENVISAT satellite. The retrieval method is developed on the basis of a simple DOAS retrieval applied to averaged transmittances. The vertical inversion of the sodium slant path optical thickness is performed by using a modified Gaussian extinction profile. A global climatology is derived by using monthly bins of 20 degrees in latitude. The high variability of the sodium layer is confirmed on a global scale as well as the presence of an important modulation in the annual cycle. Also, we present some evidence for the existence of a diurnal cycle characterized by an increase of the sodium concentration in daylight.
Variability of Antarctic circumpolar transport and the Southern Annular Mode associated with the Madden‐Julian Oscillation
Authors: Matthews Adrian J. , Meredith Michael P.
Published: January 2005

The variability of oceanic Antarctic circumpolar transport and the atmospheric Southern Annular Mode (SAM) on intraseasonal (30–70‐day) timescales is shown to be related to the tropical atmospheric Madden‐Julian Oscillation (MJO) during southern winter. Approximately 7 days after anomalous MJO convection in the equatorial Indian Ocean peaks, an atmospheric extratropical response is set up with anomalous surface westerlies around almost the entire latitude circle at 60°S. This pattern projects strongly onto the SAM and leads to an acceleration of the eastward circumpolar transport around Antarctica, as measured by tide gauges and bottom pressure recorders. This ocean response is confirmed by a global ocean model, which shows a maximum in the transport through Drake Passage 3 days after the atmospheric extratropical response.
Isostasy of the Moon from high‐resolution gravity and topography data: Implication for its thermal history
Authors: Sugano T. , Heki K.
Published: January 2005

The Lunar Prospector line‐of‐sight acceleration data after terrain correction have been inverted to the high‐resolution Bouguer gravity anomalies of the lunar nearside. Lithospheric thicknesses of the early Moon were investigated by comparing the gravity anomalies of craters and impact basins of various dimensions. The lithosphere was already thick enough to support craters with diameters up to 300 km in the Pre‐Nectarian and Nectarian Periods. Degree of isostatic compensation of larger impact basins suggested lithospheric thickness of 20–60 km at that time, which depended more on localities rather than age differences.
Generation of transient dayside subauroral proton precipitation
Authors: Fuselier S. A. , Gary S. P. , Thomsen M. F. , Claflin E. S. , Hubert B. , Sandel B. R. , Immel T.
Published: January 2005

The Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) spacecraft obtained the first global images of the proton aurora. One of the discoveries from these images was a region of proton precipitation equatorward of the nominal auroral oval. This precipitation can be observed for ∼10 min immediately following a large solar wind pressure pulse. Various mechanisms have been proposed for producing this precipitation. This study focuses on one of the proposed mechanisms, the scattering and precipitation of protons due to interaction with electromagnetic ion cyclotron (EMIC) waves. Using data from the IMAGE spacecraft FUV and EUV imagers, in situ ring current data from the Los Alamos geosynchronous spacecraft, and in situ solar wind data from the ACE spacecraft, two features of the precipitation, the local time occurrence and limited latitudinal extent, are explained. The local time occurrence of the precipitation is correlated with the orientation of the pressure pulse front in the solar wind. The limited latitudinal extent of the emissions appears to be related to the interaction between the hot ring current protons and the cold plasmaspheric ions that gives rise to EMIC wave growth.
Vertical wind distribution in the polar thermosphere during Horizontal E Region Experiment (HEX) campaign
Authors: Ishii M. , Kubota M. , Conde M. , Smith R. W. , Krynicki M.
Published: January 2005

Vertical winds in the thermosphere were measured with two Fabry‐Perot Interferometers at the Poker Flat Research Range (PFRR) and Eagle observatory, Alaska during the Horizontal E Region Experiment (HEX) campaign (Feburary and March 2003). Since these two observatories have almost the same geomagnetic latitude, we could deduce vertical wind distributions along the same auroral arc. The OI557.7‐nm and OI630.0‐nm emissions were separated using a dichroic mirror, which enabled us to estimate temporal variations in vertical winds in the E and F regions simultaneously. To measure the optical auroral distribution, we used all‐sky imagers at the PFRR. We had 13 clear nights out of a total of 23. We obtained the following results from the observations. (1) The temporal variations in vertical wind observed at OI557.7 nm at the two observatories had a high degree of correlation, despite being ∼300 km apart. The correlation coefficients exceeded 0.6 on six of the 13 nights. The chance of exceeding a correlation coefficient of 0.6 on an individual night is about 0.1%. (2) The correlation was relatively low in the OI630.0‐nm observation. (3) Some low‐correlation cases for both wavelengths indicated that the location of the auroral arc with respect to the observatory was different for the two sites, namely, whether the auroral arc was poleward or equatorward of the observational area. These results suggest that the vertical wind structures along one auroral arc are uniform at least 300 km apart. This wind distribution was consistent with previous works in most cases, but some exceptions were also found.
Global variability of mesospheric temperature: Mean temperature field
Authors: Shepherd Marianna G. , Evans Wayne F. J. , Hernandez G. , Offermann Dirk , Takahashi Hisao
Published: January 2005

Daytime zonally (longitudinally) averaged temperatures from the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS) and nightly temperatures from various ground‐based hydroxyl airglow observations are employed in the study of the global and seasonal variability of the upper mesospheric temperature field. The study examines the latitudinal variability of the annual cycle of mesospheric temperature at 75, 82, and 87 km employing 7 years (1991–1997) of WINDII mesospheric temperature data at latitudes from 20°S to 65°N at 75 km, 35°S to 65°N at 82 km, and from 45°S to 65°N at 87 km height. Particular attention is given to the latitude region of ±40° around the equator. Harmonic analysis of the 7‐year temperature time series reveals the presence of a dominant annual, ∼90‐ and 60‐day oscillations at high northern latitudes and a strong semiannual oscillation (SAO) at equatorial and tropical latitudes. A quasi‐biennial oscillation (QBO) is also identified extending from 45°S to 65°N. At 75 km the SAO is manifested as minima in the temperature composites at spring and fall equinox and maxima at winter and summer solstice; at 87 km the SAO is out of phase with respect to the 75‐km SAO, with maxima at equinox and minima around the solstice periods. The phase reversal takes place around 82 km and is associated with a mesospheric temperature inversion between 77 and 86 km height. Accounting for tidal contribution by adopting tidal predictions by the Extended Canadian Middle Atmosphere Model (CMAM) shows that a strong temperature decrease (∼35 K) seen during the 1993 March equinox at equatorial and tropical latitudes is not associated with solar migrating tides. WINDII global climatology derived at 75, 82, and 87 km revealed mesospheric SAO asymmetry with a stronger September equinox and interhemispheric asymmetry with a quieter and colder southern hemisphere. Comparisons with independent ground‐based observations and the Solar Mesospheric Explorer (SME) satellite data are also presented showing good to excellent agreement in the derived annual and SAO parameters. The results presented provide the first high‐vertical‐and‐temporal resolution global daytime temperature climatology in the upper mesosphere and in the vicinity of the mesopause.
Temperatures and horizontal winds in the Antarctic summer mesosphere
Authors: Lübken Franz‐Josef , Müllemann Arno , Jarvis Martin J.
Published: January 2005

A series of 26 meteorological rockets (“falling spheres,” FS) were launched in January and February 1998 from the Antarctic research station Rothera (68°S, 68°W). These flights gave densities and temperatures below ∼93 km and horizontal winds below ∼75 km, respectively. The lowest altitude is approximately 35 km. The instrumental technique is identical to the one applied in similar studies in the Northern Hemisphere (NH). In this paper, we summarize the experimental results and compare them with climatologies in the NH summer and with empirical models. We concentrate on the mesosphere. In January, temperatures in the upper mesosphere are very low (<135 K) and are very similar to the NH. In February, temperatures increase substantially, certainly more than in the corresponding time period in the NH. The zonal winds show a similar behavior: SH/NH values are very similar in January/July but differ in February/August. This indicates that (at least in 1998) the seasonal transition from summer to winter occurs earlier in the SH compared to the NH. Mass densities are generally similar in both hemispheres. The difference is less than 2–6% and shows a seasonal variation similar to temperatures and zonal winds. Our experimental results at Rothera differ significantly from empirical reference atmospheres such as the COSPAR International Reference Atmosphere (CIRA). For example, in the upper mesosphere our mass densities are up to 35–40% smaller compared to CIRA. Such differences can be important, for example, when modeling the sedimentation of ice particles leading to noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE). Furthermore, zonal winds in the mesosphere in January/July in the SH/NH are very similar in our measurements but different in CIRA. Recent lidar and radar measurements of NLC at Rothera and PMSE at Davis (68.6°S), respectively, show very similar mean altitudes compared to the NH supporting the similarity of the thermal structures in both hemispheres in January/July.
Advances in characterization of size‐resolved organic matter in marine aerosol over the North Atlantic
Authors: Cavalli F. , Facchini M. C. , Decesari S. , Mircea M. , Emblico L. , Fuzzi S. , Ceburnis D. , Yoon Y. J. , O'Dowd C. D. , Putaud J.‐P. , Dell'Acqua A.
Published: January 2005

Size‐segregated marine aerosols were collected at Mace Head Atmospheric Research Station (Ireland) during spring and autumn 2002 corresponding with the phytoplankton bloom periods in the North Atlantic. Strict control of the sampling, air mass back trajectory analysis, and analysis of pollutant tracers allowed the selection of a set of samples representative of clean marine conditions. A comprehensive chemical characterization of both (1) water‐soluble and water‐insoluble organic fraction and (2) water‐soluble inorganic ions was performed. The selected samples illustrated a consistent picture in terms of chemical composition. The supermicron mode predominantly comprises sea‐salt aerosol with a mass concentration of 10.16 ± 0.80 μg m−3, the remainder being non‐sea‐salt (nss) sulphate, 0.03 ± 0.01 μg m−3, and nitrate, 0.13 ± 0.04 μg m−3. By comparison, the mass of sea salt, nss sulphate, and nitrate in the submicron mode is found to be 0.39 ± 0.08 μg m−3, 0.26 ± 0.04 μg m−3, and 0.02 ± 0.01 μg m−3, respectively. Water‐soluble organic carbon (WSOC) is observed in the submicron mode with a mass concentration of 0.25 ± 0.04 μg m−3, comparable to that of nss sulphate, and in the supermicron mode with a mass concentration of 0.17 ± 0.04 μg m−3. The WSOC to total carbon (TC) ratio is found to be 0.20 ± 0.12 for the submicron fraction and 0.29 ± 0.08 for the supermicron fraction, while the black carbon (BC) to TC ratio is, on average, 0.032 ± 0.001 for both aerosol modes. The remaining carbon, water‐insoluble organic carbon, contributes 0.66 ± 0.11 μg m−3 and 0.26 ± 0.06 μg m−3 to the submicron and supermicron modes, respectively and, thus, represents the dominant submicron aerosol species. Furthermore, the WSOC chemical composition comprises mainly aliphatic and only partially oxidized species and humic‐like substances, resulting in appreciable surface‐active properties. The observed organic matter chemical features (size‐dependent concentration, hydrophobic nature of a substantial fraction of the organic matter, and low oxidized and surface‐active WSOC species) are consistent with the hypothesis of a primary marine source; bubble‐bursting processes, occurring at the surface of the North Atlantic Ocean during phytoplankton blooms, effectively transfer organic matter into marine aerosol particles, particularly enriching the fine‐aerosol fraction.
Stratosphere‐troposphere exchange of mass and ozone
Authors: Olsen Mark A. , Schoeberl Mark R. , Douglass Anne R.
Published: January 2005

This study examines the relationship between the extratropical cross‐tropopause fluxes of mass and ozone. The adiabatic and diabatic components of the net fluxes are also compared. The rate of change of mass in the lowermost stratosphere and the flux across the 380 K isentropic surface are used to determine the net tropopause mass flux in the framework of a global circulation model. The diabatic mass flux is calculated from the heating rate at the tropopause, and the adiabatic component is determined by the difference of the net and diabatic fluxes. Consistent ozone fields are obtained by driving the Goddard Chemistry and Transport Model with meteorological output of the global circulation model for the same years. The ozone flux is determined by convolving the mass flux and ozone mixing ratio. The results show the following: (1) The seasonal cycle of the ozone mixing ratio is out of phase with the transport cycle leading to a temporal offset of the mass and ozone fluxes; (2) the downward net diabatic flux of mass and ozone occurs primarily at middle latitudes while the adiabatic mass flux is dominated by troposphere‐to‐stratosphere transport at higher latitudes; and (3) the Southern Hemisphere stratospheric vortex is more effective at blocking meridional transport, resulting in a phase difference of mean tropopause ozone mixing ratio in the higher Southern Hemisphere latitudes with respect to the corresponding Northern Hemisphere season and location. Finally, this study suggests that individual pathways of cross‐tropopause transport are unlikely to be the result of simultaneous adiabatic and diabatic mechanisms.
Comparison of trends and low‐frequency variability in CRU, ERA‐40, and NCEP/NCAR analyses of surface air temperature
Authors: Simmons A. J. , Jones P. D. , da Costa Bechtold V. , Beljaars A. C. M. , Kållberg P. W. , Saarinen S. , Uppala S. M. , Viterbo P. , Wedi N.
Published: January 2005

Anomalies in monthly mean surface air temperature from the 45‐Year European Centre for Medium‐Range Weather Forecasts (ECMWF) Re‐Analysis (ERA‐40) and the first National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis are compared with corresponding values from the Climatic Research Unit (CRU) CRUTEM2v data set derived directly from monthly station data. There is mostly very similar short‐term variability, especially between ERA‐40 and CRUTEM2v. Linear trends are significantly lower for the two reanalyses when computed over the full period studied, 1958–2001, but ERA‐40 trends are within 10% of CRUTEM2v values for the Northern Hemisphere when computed from 1979 onward. Gaps in the availability of synoptic surface data contribute to relatively poor performance of ERA‐40 prior to 1967. A few highly suspect values in each of the data sets have also been identified. ERA‐40's use of screen‐level observations contributes to the agreement between the ERA‐40 and CRUTEM2v analyses, but the quality of the overall observing system and general character of the ERA‐40 data assimilation system are also contributing factors. Temperatures from ERA‐40 vary coherently throughout the boundary layer from the late 1970s onward, in general, and earlier for some regions. There is a cold bias in early years at 500 hPa over the data‐sparse southern extratropics and at the surface over Antarctica. One indicator of this comes from comparing the ERA‐40 analyses with results from a simulation of the atmosphere for the ERA‐40 period produced using the same model and same distributions of sea surface temperature and sea ice as used in the ERA‐40 data assimilation. The simulation itself reproduces quite well the warming trend over land seen in CRUTEM2v and captures some of the low‐frequency variability.
ENSO signals of the twentieth century in an ice core from Nevado Illimani, Bolivia
Authors: Knüsel S. , Brütsch S. , Henderson K. A. , Palmer A. S. , Schwikowski M.
Published: January 2005

An ice core from Nevado Illimani in the eastern Bolivian Altiplano was used to establish proxy data for past climate conditions. For this purpose a principal component analysis (PCA) was performed on the records of ionic species of the upper 59.2 m (time period 1887 ± 6 to 1999 A.D.). The first principal component (PC1) shows high loadings of mainly dust‐related ions. This signal is inversely correlated on a monthly basis with precipitation on the Bolivian Altiplano. Maxima in the PC1 time series correspond to the dry season on the Altiplano during the austral winter, whereas minima occur during the wet season from November to March. Interannual variability of PC1 reveals correlations with indices of the El Niño–Southern Oscillation (ENSO), showing elevated (reduced) dust values at the Nevado Illimani site during warm (cold) phases. This relationship may be explained by below (above) average December–February precipitation in the Bolivian Altiplano during El Niño (La Niña) episodes. Persistent El Niño events such as those in the years 1915, 1942, and 1993 A.D. seem to imprint very strong dust signals in the Illimani ice core. Out of the six PCs extracted, only the PC1 time series is correlated with the Tropical Southern Atlantic index. Thus we suggest that the major climate variability on the Bolivian Altiplano as recorded in the Nevado Illimani ice core is more closely related to conditions in the Pacific, even though the moisture source at this site is ultimately the Atlantic Ocean.
Evaluation of automated flow‐through time‐resolved analysis of foraminifera for Mg/Ca paleothermometry
Authors: Klinkhammer G. P. , Haley B. A. , Mix A. C. , Benway H. M. , Cheseby M.
Published: January 2005

The primary Mg/Ca ratio of foraminiferal shells is a potentially valuable paleoproxy for sea surface temperature (SST) reconstructions. However, the reliable extraction of this ratio from sedimentary calcite assumes that we can overcome artifacts related to foraminiferal ecology and partial dissolution, as well as contamination by secondary calcite and clay. The standard batch method for Mg/Ca analysis involves cracking, sonicating, and rinsing the tests to remove clay, followed by chemical cleaning, and finally acid‐digestion and single‐point measurement. This laborious procedure often results in substantial loss of sample (typically 30–60%). We find that even the earliest steps of this procedure can fractionate Mg from Ca, thus biasing the result toward a more variable and often anomalously low Mg/Ca ratio. Moreover, the more rigorous the cleaning, the more calcite is lost, and the more likely it becomes that any residual clay that has not been removed by physical cleaning will increase the ratio. These potentially significant sources of error can be overcome with a flow‐through (FT) sequential leaching method that makes time‐ and labor‐intensive pretreatments unnecessary. When combined with time‐resolved analysis (FT‐TRA) flow‐through, performed with a gradually increasing and highly regulated acid strength, produces continuous records of Mg, Sr, Al, and Ca concentrations in the leachate sorted by dissolution susceptibility of the reacting material. Flow‐through separates secondary calcite from less susceptible biogenic calcite and clay, and further resolves the biogenic component into primary and more resistant fractions. FT‐TRA reliably separates secondary calcite (which is not representative of original life habitats) from the more resistant biogenic calcite (the desired signal) and clay (a contaminant of high Mg/Ca, which also contains Al), and further resolves the biogenic component into primary and more resistant fractions that may reflect habitat or other changes during ontogeny. We find that the most susceptible fraction of biogenic calcite in surface dwelling foraminifera gives the most accurate value for SST and therefore best represents primary calcite. Sequential dissolution curves can be used to correct the primary Mg/Ca ratio for clay, if necessary. However, the temporal separation of calcite from clay in FT‐TRA is so complete that this correction is typically ≤2%, even in clay‐rich sediments. Unlike hands‐on batch methods, that are difficult to reproduce exactly, flow‐through lends itself to automation, providing precise replication of treatment for every sample. Our automated flow‐through system can process 22 samples, two system blanks, and 48 mixed standards in <12 hours of unattended operation. FT‐TRA thus represents a faster, cheaper, and better way to determine Mg/Ca ratios in foraminiferal calcite.
Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral
Authors: Cohen Anne L. , Hart Stanley R.
Published: January 2005

Using Secondary Ion Mass Spectrometry (SIMS) ion microprobe techniques, we generated annual Sr/Ca cycles with subweekly resolution from chunks of Porites coral retrieved from a Tahiti barrier reef drill core (149°W, 17°S), representing the period 13,650 to 13,100 years B.P. The centers of pristine skeletal septa were selectively targeted with a 10 μm diameter ion beam spot, avoiding adjacent pore spaces occupied by secondary aragonite needles. Applying a Sr/Ca–sea surface temperature (SST) calibration equation derived from modern Tahiti Porites having the same low growth rate as the fossil specimens, we obtained SSTs ∼0.5°–1.5°C cooler during the Bølling‐Allerod relative to the present day, with no significant change in seasonality. On the contrary, we estimate that analysis of bulk samples would yield excessively cool Sr/Ca‐based SST estimates due to the occupation by secondary aragonite crystals of up to 50% of the skeletal pore space in the ancient samples. We find that growth rate effects on coral Sr/Ca further depress the apparent mean annual derived SSTs (by >3°C) and amplify the apparent seasonality by selectively enhancing wintertime cooling. Our microscale analysis of pristine skeleton and application of an appropriate growth‐dependent calibration yield Sr/Ca‐derived SSTs that are in good agreement with those derived from Mg/Ca ratios of calcitic foraminifera which indicate a continuous postglacial warming of the western tropical Pacific, in phase with the warming of the tropical Atlantic.
Mesoscale convective systems
Authors: Houze Robert A.
Published: January 2005

Mesoscale convective systems (MCSs) have regions of both convective and stratiform precipitation, and they develop mesoscale circulations as they mature. The upward motion takes the form of a deep‐layer ascent drawn into the MCS in response to the latent heating and cooling in the convective region. The ascending layer overturns as it rises but overall retains a coherent layer structure. A middle level layer of inflow enters the stratiform region of the MCS from a direction determined by the large‐scale flow and descends in response to diabatic cooling at middle‐to‐low levels. A middle level mesoscale convective vortex (MCV) develops in the stratiform region, prolongs the MCS, and may contribute to tropical cyclone development. The propagation of an MCS may have a discrete component but may further be influenced by waves and disturbances generated both in response to the MCS and external to the MCS. Waves of a larger scale may affect the propagation velocity by phase locking with the MCS in a cooperative mode. The horizontal scale of an MCS may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the Rossby radius of the MCV. The vertical redistribution of momentum by an MCS depends on the size of the stratiform region, while the net vertical profile of heating of the large‐scale environment depends on the amount of stratiform rain. Regional variability of the stratiform rain from MCSs affects the large‐scale circulation's response to MCS heating.
Estimation of gradients from sparse data by universal kriging
Authors: Pardo‐Igúzquiza Eulogio , Chica‐Olmo Mario
Published: January 2005

The determination of a gradient, or directional derivative, of a spatial variable is a common problem in many Earth science applications. For hydraulic heads, for example, the gradient defines the direction of the groundwater flow and is used in solving groundwater flow and transport equations. Kriging provides a methodology for estimating gradients directly from experimental data without the need to estimate the variable at the nodes of a regular grid (even when the data are widely and irregularly scattered) and without the need to use finite difference approximations. Kriging is more efficient than other methods of gradient estimation because it uses a probabilistic approach that gives an estimator that is unbiased and with minimum estimation variance. In addition, it provides a standard error of estimation, which is not available from deterministic methods. We extend the kriging formulation of gradient estimation to the universal kriging formulation to account for the frequently observed drift in spatial variables; this is almost always present at the regional scale, for example, for hydraulic head. We present an alternative approach to kriging the gradient that is simpler than previous formulations. This new formulation uses linear systems theory, which facilitates the inference of the required covariances as functions of the covariance of the primary variable whose gradient is to be estimated. An example of estimating the gradient of hydraulic head in an aquifer in southern Spain is presented to illustrate the methodology.
Variational estimation of soil and vegetation turbulent transfer and heat flux parameters from sequences of multisensor imagery
Authors: Caparrini Francesca , Castelli Fabio , Entekhabi Dara
Published: January 2005

Turbulent heat fluxes from the surface do not have a unique signature that can be detected by remotely deployed instruments. In order to retrieve the fluxes, the measurements need to be merged into models that infer fluxes from their space and time patterns. This study is based on variational assimilation of land surface temperature (LST) into a surface energy balance model with dual‐source soil and vegetation flux components. There are two major unknown parameters in the estimation of land evaporation: near‐surface air turbulent conductivity (that scales the magnitude of the fluxes) and evaporative fraction (that partitions the total flux into latent and sensible heat flux). This study advances the data assimilation approach in two major new directions. First and foremost, it recasts the variational assimilation system as a multiscale problem with LST estimates from a constellation of satellites. The assimilation system can ingest measurements with varying scales and overlapping coverages. Second, the remotely sensed LST is treated as a combination of contributions from the canopy and the exposed soil surface. Application to a large area within the U.S. Great Plains is shown. Spatial patterns of the retrieved parameters, their correspondence to observed land use maps, and their consistency with seasonal phenology are demonstrated. Finally, the performance of a combined‐source formulation is compared with the dual‐source model. Remarkably, the spatial patterns of the heat transfer coefficient reflect dominant vegetation patterns, even though there was no vegetation index information used in the combined‐source formulation.
Experimental evolution of conflict mediation between genomes
Authors: Sachs Joel L. , Bull James J.
Published: January 2005

Transitions to new levels of biological complexity often require cooperation among component individuals, but individual selection among those components may favor a selfishness that thwarts the evolution of cooperation. Biological systems with elements of cooperation and conflict are especially challenging to understand because the very direction of evolution is indeterminate and cannot be predicted without knowing which types of selfish mutations and interactions can arise. Here, we investigated the evolution of two bacteriophages (f1 and IKe) experimentally forced to obey a life cycle with elements of cooperation and conflict, whose outcome could have ranged from extinction of the population (due to selection of selfish elements) to extreme cooperation. Our results show the
de novo
evolution of a conflict mediation system that facilitates cooperation. Specifically, the two phages evolved to copackage their genomes into one protein coat, ensuring cotransmission with each other and virtually eliminating conflict. Thereafter, IKe evolved such extreme genome reduction that it lost the ability to make its own virions independent of f1. Our results parallel a variety of conflict mediation mechanisms existing in nature: evolution of reduced genomes in symbionts, cotransmission of partners, and obligate coexistence between cooperating species.
The neocortical microcircuit as a
tabula rasa
Authors: Kalisman Nir , Silberberg Gilad , Markram Henry
Published: January 2005

The neocortex has a high capacity for plasticity. To understand the full scope of this capacity, it is essential to know how neurons choose particular partners to form synaptic connections. By using multineuron whole-cell recordings and confocal microscopy we found that axons of layer V neocortical pyramidal neurons do not preferentially project toward the dendrites of particular neighboring pyramidal neurons; instead, axons promiscuously touch all neighboring dendrites without any bias. Functional synaptic coupling of a small fraction of these neurons is, however, correlated with the existence of synaptic boutons at existing touch sites. These data provide the first direct experimental evidence for a
tabula rasa
-like structural matrix between neocortical pyramidal neurons and suggests that pre- and postsynaptic interactions shape the conversion between touches and synapses to form specific functional microcircuits. These data also indicate that the local neocortical microcircuit has the potential to be differently rewired without the need for remodeling axonal or dendritic arbors.
Noncanonical Wnt signaling regulates midline convergence of organ primordia during zebrafish development
Authors: Matsui Takaaki , Raya Ángel , Kawakami Yasuhiko , Callol-Massot Carles , Capdevila Javier , Rodríguez-Esteban Concepción , Izpisúa Belmonte Juan Carlos
Published: January 2005

Several components of noncanonical Wnt signaling pathways are involved in the control of convergence and extension (CE) movements during zebrafish and Xenopus gastrulation. However, the complexity of these pathways and the wide patterns of expression and activity displayed by some of their components immediately suggest additional morphogenetic roles beyond the control of CE. Here we show that the key modular intracellular mediator Dishevelled, through a specific activation of RhoA GTPase, controls the process of convergence of endoderm and organ precursors toward the embryonic midline in the zebrafish embryo. We also show that three Wnt noncanonical ligands wnt4a, silberblick/wnt11, and wnt11-related regulate this process by acting in a largely redundant way. The same ligands are also required, nonredundantly, to control specific aspects of CE that involve interaction of Dishevelled with mediators different from that of RhoA GTPase. Overall, our results uncover a late, previously unexpected role of noncanonical Wnt signaling in the control of midline assembly of organ precursors during vertebrate embryo development.
Premature targeting of a cell division protein to midcell allows dissection of divisome assembly in Escherichia coli
Authors: Goehring Nathan W. , Gueiros-Filho Frederico , Beckwith Jon
Published: January 2005

Cell division in Escherichia coli requires the recruitment of at least 10 essential proteins to the bacterial midcell. Recruitment of these proteins follows a largely linear dependency pathway in which depletion of one cell division protein leads to the absence from the division site of “downstream” proteins in the pathway. Analysis of events that underlie this pathway is complicated by the fact that a protein's ability to recruit “downstream” proteins is dependent on its own recruitment by “upstream” proteins. Hence, one cannot separate the individual contributions of various upstream proteins to any specific recruitment step. Here we present a method—premature targeting—for bypassing the normal localization requirements of a cell division protein and apply it to FtsQ, a protein recruited midway through the pathway. We fused FtsQ to the FtsZ-binding protein ZapA such that FtsQ was targeted to FtsZ rings independently of proteins FtsA and FtsK, which are normally required for FtsQ localization. Analysis of the resulting ZapA–FtsQ fusion suggests that FtsQ associates with a large complex of cell division proteins and that premature targeting of FtsQ can restore localization of this complex under conditions in which neither FtsQ nor the associated proteins would normally be localized.