Expeditions 304 and 305 of the Integrated Ocean Drilling Program cored and logged a 1.4 km section of the domal core of Atlantis Massif. Postdrilling research results summarized here constrain the structure and lithology of the Central Dome of this oceanic core complex. The dominantly gabbroic sequence recovered contrasts with predrilling predictions; application of the ground truth in subsequent geophysical processing has produced self-consistent models for the Central Dome. The presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100-220 kyr, and not as a single magma pulse. Isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth. Below 800 m, alteration is restricted to narrow zones surrounding faults, veins, igneous contacts, and to an interval of locally intense serpentinization in olivine-rich troctolite. Hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies, but was predominantly in the amphibolite and greenschist range. Deformation of the sequence was remarkably localized, despite paleomagnetic indications that the dome has undergone at least 45 degrees rotation, presumably during unroofing via detachment faulting. Both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent Southern Ridge of the massif. There, the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises similar to 70% of recovered samples. We develop a working model of the evolution of Atlantis Massif over the past 2 Myr, outlining several stages that could explain the observed similarities and differences between the Central Dome and the Southern Ridge.

The temporal and spatial behaviors of atmospheric pressure spectra over the northern Italy and the Alpine massif were analyzed using data on surface pressure measurements carried out at two microbarograph stations in the Po Valley, one 50 km south of the Alps, the other in the foothills of the Dolomites. The first 15 days of the study overlapped with the Alpex Intensive Observation Period. The pressure records were found to be intrinsically nonstationary and were found to display substantial time variability, implying that the statistical moments depend on time. The shape and the energy content of spectra depended on different time segments. In addition, important differences existed between spectra obtained at the two stations, indicating a substantial effect of topography, particularly for periods less than 40 min.

New data obtained at the Boulder Atmospheric Observatory (BAO) has been compared with a linear stability analysis of the background atmospheric state as measured by rawinsonde ascents. Good agreement was obtained between measured wave parameters such as wavelength, period, and vector phase velocity, and the eigenvalues of the linear solution, but linear eigenvectors scaled by measured pressure at the base of the BAO tower less well with measurement. An investigation of the wave kinetic energy budget revealed that buoyant production of wave energy was a significant gain despite the strong stability (Ri greater than or similar to 5). Further analysis of the budgets of wave heat flux and temperature variance revealed the essential role of wave-turbulence interaction in maintaining a large amplitude temperature wave and countergradient wave heat flux. A consideration of the turbulent kinetic energy budget showed many of the same features as the wave budget. A comparison with earlier near-neutral and stable cases analyzed in comparable detail suggests that countergradient wave heat fluxes maintained by nonlinear wave-turbulence interaction and an essential transfer of kinetic energy from wave to turbulence may be generic features of such situations. A mechanism for maintenance of turbulence by waves in strongly stratified boundary layers is described, which emphasizes that the time-mean Richardson number is an irrelevant parameter at such times. In the analysis of the data, general methods are described for extracting wave signals from nonstationary turbulence records and for assessing the statistical significance of the waveform so derived.

Brittle structures (open fractures and veins) from basaltic oceanic crust drilled at Ocean Drilling Program (ODP) Site 1256 (Guatemala Basin, Pacific Ocean) during Leg 206 were reoriented to the geographic coordinates by (1) correlating structures observed on the core with unoriented images of the exterior of the core and (2) correlating core structures and unoriented images with oriented borehole images. The images of the exterior of the core were obtained by scanning wholecore pieces with the Deutsche Montan Technologie Digital Color CoreScan system. In the unrolled core images, nonhorizontal planar structures (e.g., veins, faults, or fractures) produce sinusoidal-shaped curves. These can be matched to similar-shaped features imaged along the borehole wall. The borehole images were obtained by the Formation MicroScanner (FMS)-sonic (Dipole Sonic Imager) tool string and the Ultrasonic Borehole Imager (UBI). The FMS provides high-resolution electrical resistivity–based images of borehole walls. FMS images are oriented to magnetic north using the General Purpose Inclinometer Tool. This allows the dip and azimuth of geological features intersecting the hole to be measured from the processed FMS image. The UBI features a high-resolution transducer that provides acoustic images of the 1Tartarotti, P., Crispini, L., Einaudi, F., and Campari, E., 2006. Data report: reoriented structures in the East Pacific Rise basaltic crust from ODP Hole 1256D, Leg 206: integration of core measurements and electrical-acoustic images. In Teagle, D.A.H., Wilson, D.S., Acton, G.D., and Vanko, D.A. (Eds.), Proc. ODP, Sci. Results, 206: College Station, TX (Ocean Drilling Program), 1–26. doi:10.2973/ odp.proc.sr.206.004.2006 2Dipartimento di Scienze della Terra, Universita di Milano, via Mangiagalli 34, 20133 Milano, Italy. Correspondence author: paola.tartarotti@unimi.it 3DIPTERIS, Dipartimento per lo Studio del Territorio e delle sue Risorse Universita’ di Genova, Corso Europa 26, 16132 Genova, Italy. 4Laboratoire de Geophysique et Hydrodynamique en Forage, Universite de Montpellier II, ODP/ Naturalia et Biologia (NEB) ISTEEM, cc56, 34095 Montpellier, France. Initial receipt: 30 April 2005 Acceptance: 22 December 2005 Web publication: 20 November 2006 Ms 206SR-004 P. TARTAROTTI ET AL. DATA REPORT: REORIENTED STRUCTURES IN THE EAST PACIFIC RISE 2 borehole wall. The UBI was used in hard rocks for the first time in the history of the ODP during Leg 206.

Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.

Integrated ocean drilling program expedition 309 preliminary report: Superfast Spreading Rate Crust 2 A complete in situ section of upper oceanic crust formed at a superfast spreading rate / JC Alt, DAH Teagle, S. Umino, S. Miyashita, NR Banerjee, DS Wilson, F. Einaudi, A. Belghoul, C. Cordier, L. Crispini, L. Galli, Y. Gao, J. Geldmacher, LA Gilbert, E. Herreo-Bervera, SA Holter, C. Laverne, HL Lledo Vasques, S. Rodriguez Durand, T. Sakuyama, T. Sano, CE Smith-Duque, S. Tominaga, P. Tartarotti, EA Veloso Espinosa, M. Reichow, R. Anma, J. Carlut, DM Christie, R. Coggon, NW Hayman, N. Hirano, S. Ingle, J. Koepke, J. MacLennan, S. Morgan, N. Neo, SH Park, B. Scheibner, SA Swift, AA Tikku, T. Yamazaki, S. Yamazaki. - College Station, TX … Integrated ocean drilling program expedition 309 preliminary report: Superfast Spreading Rate Crust 2 A complete in situ section of …

Abstract Physical properties of gabbroic samples from Ocean Drilling Program Hole 1105A were measured in the laboratory, with a particular emphasis on the analysis of electrical properties. This data-set includes the major lithologies sampled in ODP Hole 1105A: gabbros, olivine gabbros, oxide-rich gabbros, and, for all rock types, different ranges of alteration were sampled: from fresh to highly altered. All these lithologies correspond to the seismic Layer 3 layer of the oceanic crust, and large-scale geophysical data interpretation requires a complete understanding of the physical properties of rocks in this section. Electrical conductivities measured on brine-saturated gabbros reveal strong excess conductivity for samples rich in oxide minerals and, to a lesser extent, for altered samples. However, the classical models do not explain the excess conductivity reported in the oxide-rich samples when saturated with brine. The electrical conduction via electronic processes in metallic minerals has been taken into account in our analysis of the electrical properties. The oxide minerals’ contribution has been independently estimated through measuring dry electrical resistivity. These measurements allowed quantification of the electronic conduction, which can reach 80% of the full conductivity for the most oxide-rich gabbros.

No abstract available. doi:10.22 04/iodp.sd.1.05.2005

The data and analysis presented in this paper provide an assessment of lava morphologies and the geochemistry of lavas from the Oman ophiolite. In order to provide detailed constraints on the construction of the upper oceanic crust, a continuous volcanic transect (300 m‐thick) was sampled at high‐frequency in the Semail ophiolite along Wadi Shaffan. The Wadi Shaffan section is composed mainly of pillow lavas interbedded with massive flows and occasional hyaloclastites. The sampling performed along Wadi Shaffan implies temporal variations in the activity of the ridge. The section is characterized by chemical compositions consistent with those of V1‐Geotimes volcanism. The Wadi Shaffan transect was built through two main petrological and geochemical sequences of volcanic activity. Trace element ratios (e.g. Zr/Nb and La/Yb) allow us to distinguish two main sequences with two different parental magmas. Differences in the degree of partial melting are required to explain these trace element ratio variations. Beyond these differences in parent melt composition, variations in trace element abundances (TiO 2 , Zr, REE) involve differentiation processes prior to emplacement. In the lower sequence, less differentiated lavas are in the upper part of the cycle. Magma mixing is proposed to explain this reversed geochemical evolution through time. In the upper sequence, geochemical analysis suggests a different magma chamber process. This sequence consists of multiple events of magma emplacement. Variations in trace element abundance suggest four magmatic cycles. Each magmatic cycle is characterized by primitive lavas evolving to more differentiated lavas with time. The upper sequence lavas appear to be in equilibrium with clinopyroxene and lower sills from the MTZ (Mantle‐Crust Transition Zone) and with lower gabbros. We propose a model in which the upper sequence lavas were directly derived from the MTZ and lower gabbro sills and then transported to the surface without interaction with higher crustal levels.

The Goddard Cumulus Ensemble (GCE) model was utilized in two and three dimensions in order to examine the behavior and response of simulated deep tropical cloud systems occurred in west Pacific warm pool region and Atlantic ocean. The periods chosen for simulation were convectively active period over the TOGA-COARE IFA (19-27 December 1992) and GATE (September 1 to 7, 1974). The TOGA COARE IFA period was also in the framework of the GEWEX Cloud System Study (GCSS) WG4 case 2. We will examine the differences between the microphysics (warm rain and ice processes, evaporation/sublimation and condensation/deposition), Q1 (Temperature) and Q2 (Water vapor) budgets between these two convective events occurred in different large-scale environments. The contribution of stratiform precipitation and its relationship to the vertical shear of the large-scale horizontal wind will also be examined. The results from GCSS model intercomparsion will be presented. The new improvements (i.e., microphysics, cloud radiation interaction, surface processes and numerical advection scheme) of the GCE model as well as their sensitivity to the model results will be discussed.

Fields from chemical transport models (CTMs) driven by assimilated winds have been shown to represent many aspects of observations at middle and high latitudes. Comparisons of modeled fields with observations have been much poorer in the tropics. Noise in the tropical winds produces variability in constituents in the tropics that greatly exceeds what is observed, Constituent gradients between the tropics, subtropics and middle latitudes are weaker than observed in the lower stratosphere. Tropical transport is shown to be much more realistic using a CTM driven by winds from the assimilation system that has recently been developed by the Data Assimilation Office at Goddard Space Flight Center. The Finite Volume Community Climate Model (FV-CCM), a general circulation model model that uses the NCAR CCM physics and the Lin and Rood dynamical core, is at the core of the new assimilation system. Realistic transport in the tropics, particularly troposphere to stratosphere exchange, is an obvious requirement for realistic representation of the stratosphere to troposphere transport of ozone and other stratospheric constituents to the middle latitude upper troposphere.

Abstract A symposium celebrating the first fifty years of Dr. Joanne Simpson's career took place at the NASA Goddard Space Flight Center 1–3 December 1999. This symposium consisted of presentations that focused on historical and personal points of view concerning Dr. Simpson's research career, her interactions with the American Meteorological Society, and her leadership in Tropical Rainfall Measuring Mission (TRMM); scientific interactions with Dr. Simpson that influenced personal research; research related to observations and modeling of clouds, cloud systems, and hurricanes; and research related to the TRMM. There were a total of 36 presentations and 103 participants from the United States, Japan, and Australia. The specific presentations during the symposium are summarized in this paper.

As opposed to discontinuous seafloor dredging and coring, ophiolites and downhole geophysical measurements provide continuous sections along which high frequency accretion processes at mid‐ocean ridges may be studied. A multidisciplinary study carried out on a volcanic section of the Semail ophiolite with MORB‐like chemical composition reveals two main petrological and geochemical members. The boundary between the two is marked by the presence of a massive flow equating to the most primitive lava sampled, and across which significant changes are obtained. Petrophysical profiles are correlated to geochemical variations and provide thus a description of the magmatic activity through time. These temporal variations may be compared to those derived from crustal drilling and continuous logging measurements.

This paper presents a climatology of coherent disturbances detected during 1991‐95 by a network of barometers with a diameter of about 50 km located in a very flat terrain centered on the Flatland Atmospheric Observatory in east-central Illinois. An automatic, wavelet-based adaptive filter is used to extract the waveforms of all disturbance events with amplitudes larger than a frequency-dependent threshold. The extracted events cover characteristic temporal scales from about 30 min to 6 h, that is, the range that includes mesoscale disturbances that affect the weather and the forecasts. The analysis resulted in two classes of events. One class, called coherent events, or CEs, consists of disturbances that propagated coherently through the barograph network and for which the phase propagation velocity, dominant period, and horizontal wavelength could be estimated with good accuracy. The propagation directions of 97% of the CEs were between 08 and 1808 (i.e., had an eastward component) and the speeds of 96% were between 10 and 50 ms 21 with a mode at 25‐30 m s21. The other class, called incoherent events, or IEs, consists of disturbances that had significant amplitudes but that did not propagate coherently across the network, so that the propagation velocity could not be estimated. This class consists of localized disturbances and wave packets with short periods and/or wavelengths, or with pressure signatures that were too different at the network stations. The extracted events are attributed to gravity waves, wave packets, gravity currents, pressure jumps, solitary waves, bores, etc. The rate of occurrence of events had a strong seasonal dependence, with a maximum in fall and winter and a minimum in summer. The CEs occurred about 20%‐21% of the total time in fall and winter and 12% in summer, while all events occurred 34% in both fall and winter and 23% in summer. The seasonal dependence of events confirms the strong relation of these disturbances to the baroclinicity of the atmosphere. Concurrent vertical velocity fluctuations observed by the 50-MHz radar at the Flatland Atmospheric Observatory showed that many of the large-amplitude events extended up to at least 7 km, the highest altitude reliably observed by the radar.

This paper presents a wavelet-based algorithm for the detection, identification, and extraction of gravity waves from atmospheric pressure traces. The main data processing tool is a nonlinear adaptive filter based on the selective reconstruction of a waveform from its wavelet coefficients. The time-frequency localization of the wavelet transform provides an ideal framework for the decomposition of long-period gravity waves (30 min-6 h), which are characterized by a generally broad spectrum and few oscillation cycles. The procedure is iterative and allows the exhaustive processing of all the events present in a fixed time period. The waveform of each disturbance is reconstructed with high accuracy. This minimizes the influence of the data-processing technique on the estimate of horizontal speed and direction of propagation, obtained by maximization of the cross-correlation functions between the reconstructed waveforms at the different stations. The introduction of coherency criteria through the network of seven stations allows the authors to separate the events into two classes. The first includes the events that propagate with very small distortion through the network, while the second includes less coherent but still highly energetic events. The size of the network and the algorithm developed for the analysis is well suited for the identification and the extraction of those mesoscale disturbances that have a particularly strong influence on the weather as well as on the forecast.

A fog episode characterized by quasi-periodic oscillations in visibility is described. Gravity waves are also present, and frequencies at which pressure and transparency fluctuate are compared. The existence of intervals during which they are synchronized and the presence of strong winds aloft suggest that shear instabilities in the troposphere can influence the fog behaviour at ground.