Cold Circulation Research Articles

Hydrothermal alteration and tectonic evolution of an intermediate‐ to fast‐spreading back‐arc oceanic crust: Late Ordovician Solund‐Stavfjord ophiolite, western Norway

Abstract The Solund‐Stavfjord ophiolite complex (SSOC) in western Norway represents a remnant of the Late Ordovician oceanic lithosphere, which developed in an intermediate‐ to fast‐spreading Caledonian back‐arc basin. The internal architecture and magmatic features of its crustal component suggest that the SSOC has a complex, multistage sea floor spreading history in a supra‐subduction zone environment. The youngest crustal section associated with the propagating rift tectonics consists of a relatively complete ophiolite pseudostratigraphy, including basaltic volcanic rocks, a transition zone between the sheeted dyke complex and the extrusive sequence, sheeted dykes, and high‐level isotropic gabbros. Large‐scale variations in major and trace element distributions indicate significant remobilization far beyond that which would result from magmatic processes, as a result of the hydrothermal alteration of crustal rocks. Whereas K2O is strongly enriched in volcanic rocks of the extrusive sequence, Cu and Zn show the largest enrichment in the dyke complex near the dyke–volcanic transition zone or within this transition zone. The δ18O values of the whole‐rock samples show a general depletion structurally downwards in the ophiolite, with the largest and smallest variations observed in volcanic rocks and the transition zone, respectively. δ18O values of epidote–quartz mineral pairs indicate 260–290°C for volcanic rocks, 420°C for the transition zone, 280–345°C for the sheeted dyke complex and 290–475°C for the gabbros. The 87Sr/86Sr isotope ratios show the widest range and highest values in the extrusive rocks (0.70316–0.70495), and generally the lowest values and the narrowest range in the sheeted dyke complex (0.70338–0.70377). The minimum water/rock ratios calculated show the largest variations in volcanic rocks and gabbros (approximately 0–14), and generally the lowest values and range in the sheeted dyke complex (approximately 1–3). The δD values of epidote (−1 to −12‰), together with the δ18O calculated for Ordovician seawater, are similar to those of present‐day seawater. Volcanic rocks experienced both cold and warm water circulation, resulting in the observed K2O‐enrichment and the largest scatter in the δ18O values. As a result of metal leaching in the hot reaction zone above a magma chamber, Zn is strongly depleted in the gabbros but enriched in the sheeted dyke complex because of precipitation from upwelling of discharged hydrothermal fluids. The present study demonstrates that the near intact effect of ocean floor hydrothermal activity is preserved in the upper part of the SSOC crust, despite the influence of regional lower greenschist facies metamorphism.

NCAR-TIEGCM을 이용한 이온권과 열권의 상호작용 연구: 행성간 자기장(IMF)에 따른 고위도 하부 열권의 운동량 강제에 대한 연구

본 연구에서는 미 국립대기연구소(NCAR)의 열권-이온권 전기역학적 대순환 모델(TIEGCM)을 이용하여 행성간 자기장(IMF)의 방향과 세기 그리고 고도에 따라 여름철 남반구 고위도 하부 열권의 바람에 작용하는 운동량 강제력을 정량적으로 구하였다. 그리고 이들을 서로 비교 분석함으로써 IMF 조건과 고도에 따른 고위도 하부 열권의 풍계(wind system)를 유지시켜주는 주된 물리적인 과정을 살펴보았다. 고위도 하부 열권(<180km)에서 양(<TEX>$B_y$</TEX> > 0.8|<TEX>$\overline{B}_z$</TEX>|)또는 음(<TEX>$B_y$</TEX> < -0.8|<TEX>$\overline{B}_z$</TEX>|)의 IMF By 조건인 경우에 운동량 강제력 차이, 즉 IMF 기준치 <TEX>${\neq}$</TEX> 0 일 때와 IMF 기준치=0 일 때의 운동량 강제력 차이(difference momentum force)는 자기위도 -80<TEX>$^{\circ}$</TEX>에서 최대값을 가지면서 극관과 오로라 영역에 국한된 단순한 형태의 분포를 보인다. 그리고 IMF <TEX>$B_z$</TEX> 성분이 양과 음일 때 강제력 차이의 세기는 비슷하지만 분포양상은 반대방향을 취한다. 한편 IMF <TEX>$B_z$</TEX>가 양(<TEX>$B_z$</TEX> > 0.3125|<TEX>$\overline{B}_y$</TEX>|) 또는 음(<TEX>$B_z$</TEX> < -0.3125|<TEX>$\overline{B}_y$</TEX>|)인 조건인 경우에는 강제력 차이가 아오로라(subauroral) 위도까지 분포하며 IMF <TEX>$B_z$</TEX>가 양 또는 음의 조건일 때 보다 복잡한 구조를 보인다. 그리고 IMF <TEX>$B_z$</TEX>가 음인 경우의 강제력 차이가 양인 경우보다 더 크며 반대방향으로 작용한다. 125km 보다 더 높은 고도(>125km)에서 바람차이를 결정하는 주된 강제력은 기압경도력, 전향력, 수평이류 그리고 비발산 성분이 강한 Pedersen 이온항력인 것으로 확인되었다. 고도 약 125km 에서는 이 네 가지 힘에 더불어 비회전 성분이 강한 Hall 이온향력과 극관내 의 연직 이류가 지역과 시간에 따라 바람차이의 형성에 작용한다. 한편 고도 108-125km 에서는 IMF <TEX>$B_z$</TEX> 조건일 경우의 극관영역을 제외하고는 기압경도력, 전향력 그리고 Hall 이온항력이 이 고도에서의 바람차이를 유발시키는 주된 강제력으로 작용한다. 고도 108km 이하에서는 기압경도력과 전향력이 균형을 이루어 지균 운동을 유지시킨다. IMF-<TEX>$\overline{B}_y$</TEX>의존 MLT 평균 운동량 강제력들은 이온항력을 제외한 다른 모든 남북성분이 동서성분에 비해 더 강하게 중성대기에 작용하는 것으로 확인되었다. 108-125km의 고도에서 IMF B?가 음인 경우에 이온항력은 하강운동 및 단열압축가열과 관련된 시계방향의 온난순환(warm circulation)을 극관 내에 형성시킨다. 반면 IMF <TEX>$B_y$</TEX>가 양인 경우에는 극관 내에 상승운동 및 단열팽창냉각과 관련된 반시계방향의 한랭순환(cold circulation)을 형성시킨다. 이온항력은 IMF <TEX>$B_z$</TEX>가 음인 경우에는 새벽영역에 상승운동과 관련된 반시계방향의 한랭순환을, 반면에 IMF <TEX>$B_z$</TEX>가 양인 경우에는 새벽영역에 하강운동과 관련된 시계방향의 온난순환을 형성시킨다. To understand the physical processes that control the high-latitude lower thermospheric dynamics, we quantify the forces that are mainly responsible for maintaining the high-latitude lower thermospheric wind system with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM). Momentum forcing is statistically analyzed in magnetic coordinates, and its behavior with respect to the magnitude and orientation of the interplanetary magnetic field (IMF) is further examined. By subtracting the values with zero IMF from those with non-zero IMF, we obtained the difference winds and forces in the high-latitude 1ower thermosphere(<180 km). They show a simple structure over the polar cap and auroral regions for positive(<TEX>$B_y$</TEX> > 0.8|<TEX>$\overline{B}_z$</TEX> |) or negative(<TEX>$B_y$</TEX> < -0.8|<TEX>$\overline{B}_z$</TEX>|) IMF-<TEX>$\overline{B}_y$</TEX> conditions, with maximum values appearing around -80<TEX>$^{\circ}$</TEX> magnetic latitude. Difference winds and difference forces for negative and positive <TEX>$\overline{B}_y$</TEX> have an opposite sign and similar strength each other. For positive(<TEX>$B_z$</TEX> > 0.3125|<TEX>$\overline{B}_y$</TEX>|) or negative(<TEX>$B_z$</TEX> < -0.3125|<TEX>$\overline{B}_y$</TEX>|) IMF-<TEX>$\overline{B}_z$</TEX> conditions the difference winds and difference forces are noted to subauroral latitudes. Difference winds and difference forces for negative <TEX>$\overline{B}_z$</TEX> have an opposite sign to positive <TEX>$\overline{B}_z$</TEX> condition. Those for negative <TEX>$\overline{B}_z$</TEX> are stronger than those for positive indicating that negative <TEX>$\overline{B}_z$</TEX> has a stronger effect on the winds and momentum forces than does positive <TEX>$\overline{B}_z$</TEX> At higher altitudes(>125 km) the primary forces that determine the variations of tile neutral winds are the pressure gradient, Coriolis and rotational Pedersen ion drag forces; however, at various locations and times significant contributions can be made by the horizontal advection force. On the other hand, at lower altitudes(108-125 km) the pressure gradient, Coriolis and non-rotational Hall ion drag forces determine the variations of the neutral winds. At lower altitudes(<108 km) it tends to generate a geostrophic motion with the balance between the pressure gradient and Coriolis forces. The northward component of IMF By-dependent average momentum forces act more significantly on the neutral motion except for the ion drag. At lower altitudes(108-425 km) for negative IMF-<TEX>$\overline{B}_y$</TEX> condition the ion drag force tends to generate a warm clockwise circulation with downward vertical motion associated with the adiabatic compress heating in the polar cap region. For positive IMF-<TEX>$\overline{B}_y$</TEX> condition it tends to generate a cold anticlockwise circulation with upward vertical motion associated with the adiabatic expansion cooling in the polar cap region. For negative IMF-<TEX>$\overline{B}_z$</TEX> the ion drag force tends to generate a cold anticlockwise circulation with upward vertical motion in the dawn sector. For positive IMF-<TEX>$\overline{B}_z$</TEX> it tends to generate a warm clockwise circulation with downward vertical motion in the dawn sector.

TREATMENT OF SEWAGE SLUDGE BY COLD CIRCULATION FREEZE-DRYING EQUIPMENT

Cold Circulation Freeze-Drying Equipment of a pilot plant was produced to freeze-dry sewage sludge with a view to recovering cellulose of a biomass resource. The recovery yields of solids and water by the produced equipment were 90.0-96.0% (w/w) and 170-250% (v/v), respectively. The moisture content of the dewatered sewage sludge was about 12%. The cost of the freeze-drying treatment for sewage sludge was estimated to be approximate for present sewage sludge treatment using liquefied natural gas (LNG) waste cold heat. These results also suggested that freeze-drying treatment for sewage sludge did not occur by-products (dioxin, etc.) derived from incineration.

Temporal fluctuations in heat waves at Prague–Klementinum, the Czech Republic, from 1901–97, and their relationships to atmospheric circulation

AbstractTemporal fluctuations in heat wave occurrence and severity are analysed in long‐term daily temperature series at Prague–Klementinum, the Czech Republic. Although the observations have been continuous since 1775, the period 1901–97 with the most credible data is mainly examined. Most of the warmest summers of the 20th century appeared within the periods 1943–52 and 1992–95; the temporal distribution of heat waves corresponds to this pattern and shows two maxima, in the 1940s to early 1950s and in the 1990s. A very low occurrence of heat waves was typical of the beginning of the 20th century and around 1980. The peak of heat wave severity in the 1940s–early 1950s, as well as their almost total absence in the first two decades of the 20th century, may be a common feature for a large area, as indicated by the comparison between two stations within central Europe, Prague–Klementinum and Basel (Switzerland), and by other studies. An extraordinary heat wave occurred in July and August 1994. It greatly exceeded other heat waves, mainly in the much higher cumulative temperature excess above 30°C and a record‐breaking duration of a continuous period of tropical days.Relationships between heat wave characteristics in warm and cold decades and circulation conditions were analysed using the subjective Hess–Brezowsky catalogue of weather types (Grosswetterlagen). The link to the atmospheric circulation is evident, e.g. situations with an anticyclone or a ridge over central Europe were more (less) frequent during all the warm (cold) decades. Moreover, the occurrence of long and severe heat waves in the 1990s may reflect an enhanced persistence of the atmospheric circulation over Europe in the summer season because all groups of weather types have considerably increased residence times in 1988–97 compared with long‐term means. Copyright © 2002 Royal Meteorological Society

Sources of systematic errors in the climatology of a regional climate model over Europe

Two ten-year simulations made with a European regional climate model (RCM) are compared. They are driven by the same observed sea surface temperatures but use different lateral boundary forcing. For one simulation, RCM AMIP, this forcing is obtained from a standard integration of a global general circulation model (GCM AMIP), whereas for the other simulation, RCM ASSIM, it is derived from a time series of operational analyses. The archive of analysis fields (surface pressure plus winds and temperatures on various pressure levels) is not sufficiently comprehensive to provide directly the full set of driving fields required for the RCM (in particular, no moisture fields are present), so these are obtained via a GCM integration, GCM ASSIM, in which the model is continuously relaxed towards the analysis fields using a data assimilation technique. Errors in RCM AMIP can arise either from the internal RCM physics or from errors in the lateral boundary forcing inherited from GCM AMIP. Errors in RCM ASSIM can arise from the internal RCM physics or the boundary moisture forcing but not from the driving circulation. Although previous studies have considered RCM integrations driven either by output from standard GCM integrations or operational analyses, our study is the first to compare parallel integrations of each type. This allows the total systematic error in an RCM integration driven by standard GCM output to be partitioned into components arising from the driving circulation and the internal RCM physics. These components indicate the scope for reducing regional simulation biases by improving either the driving GCM or the RCM itself. The results relate mainly to elements of surface climate likely to be influenced by both the driving circulation and regional physical processes operating in the RCM. For cloud cover, errors are found to arise largely from the internal RCM physics. Values are too low despite a positive relative humidity bias, indicating shortcomings in the parametrisation scheme used to calculate cloud cover. In summer, surface temperature and precipitation errors are also explained principally by regional processes. For example excessive solar heating leads to anomalously high surface temperatures over southern Europe and excessive drying of the soil reduces precipitation in the south eastern sector of the domain. The lateral boundary forcing reduces precipitation in the south eastern sector of the domain. The lateral boundary forcing also exerts some influence, mainly via a tropospheric cold bias which partially offsets the warming over southern Europe and also increases precipitation. In other seasons the lateral boundary forcing and the regional physics both contribute significantly to the errors in surface temperature and precipitation. In winter the boundary forcing (apart from moisture) is responsible for about 60% of the total error variance for temperature and about 40% for precipitation, due to the cold bias and circulation errors such as a southward shift in the storm track. The remaining errors arise from the regional physics, although for precipitation an excessive supply of moisture from the lateral boundaries also contributes. The skill of the mesoscale component of the surface temperature and precipitation distributions exceeds previous estimates, due to more realistic observed climatology. The mesoscale patterns are very similar in the two RCM simulations indicating that errors in the simulation of fine scale detail arise mainly from inadequate representations of local forcings rather than errors in the large-scale circulation. Circulation errors in RCM AMIP (e.g. cold bias, southward shift of storm track) are also present in GCM AMIP, but are largely absent in RCM ASSIM except in summer. This confirms evidence from previous work that the key to reducing most circulation errors in the RCM lies in improving the driving GCM. Regional processes only make a major contribution to circulation errors in summer, when reduced advection from the boundaries allows errors in surface temperature to be transmitted more effectively into the troposphere. Finally, we find evidence of error balances in the GCM which act to minimise biases in important climatological variables. This reflects tuning of the model physics at GCM resolution. In order to achieve simultaneous optimisation of the RCM and GCM at widely differing resolutions it may be necessary to introduce explicit scale dependences into some aspects of the physics.

Climatology and Interannual Variation of the East Asian Winter Monsoon: Results from the 1979–95 NCEP/NCAR Reanalysis

This paper presents the climatology and interannual variation of the East Asian winter monsoon based on the 1979–95 National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis. In addition to documenting the frequency, intensity, and preferred propagation tracks of cold surges and the evolution patterns of related fields, the authors discuss the temporal distribution of the Siberian high and cold surges. Further, the interannual variation of the cold surges and winter monsoon circulation and its relationship with ENSO were examined. There are on average 13 cold surges in each winter season (October–April), of which two are strong cases. The average intensity of cold surges, measured by maximum sea level pressure, is 1053 hPa. The cold surges originate from two source regions: 1) northwest of Lake Baikal, and 2) north of Lake Balkhash. The typical evolution of a cold surge occurs over a period of 5–14 days. Trajectory and correlation analyses indicate that, during this time, high pressure centers propagate southeastward around the edge of the Tibetan Plateau from the mentioned source regions. Some of these high pressure centers then move eastward and diminish over the oceans, while others proceed southward. The signatures of the associated temperature, wind, and pressure fields propagate farther southward and eastward. The affected area encompasses the bulk of the maritime continent. Although the intensity of the Siberian high peaks during December and January, the frequency of cold surges reaches a maximum in November and in March. This result suggests that November through March should be considered as the East Asian winter monsoon season. Two stratifications of cold surges are used to examine the relationship between ENSO and the interannual variation of the winter monsoon. The first one, described as conventional cold surges, indicates that the surge frequency reaches a minimum a year after El Niño events. The second one, defined as a maximum wind event near the South China Sea, shares the same origin as the first. The surge frequency is in good agreement with the Southern Oscillation index (SOI). A low (high) SOI event coincides with a low (high) frequency of cold surges. The interannual variation of winter northerlies near the South China Sea is dominated by the South China Sea cold surges and is well correlated (R = 0.82) with the SOI. Strong wind seasons are associated with La Niña and high SOI years; on the other hand, weak wind seasons are associated with El Niño and low SOI years. This pattern is restricted to an area north of the equator within the region of (0°–20°N, 100°–130°E) and is confined to the near-surface layer. The SST variation in the same region is similar to the wind pattern but lags the wind for approximately 1–5 months, which suggests that the SST variation is forced by the wind. The surface Siberian high, 500-hPa trough, and200-hPa jet stream, all representing the large-scale monsoon flow, are weaker than normal during El Niño years. In particular, the interannual variation of the Siberian high is in general agreement with the SOI.

El Niño, La Niña, and the Nonlinearity of Their Teleconnections

The paradigm of an atmospheric system varying linearly with respect to extreme phases of the El Nino- Southern Oscillation is questioned. It is argued that the global response to tropical Pacific sea surface temperature forcing will be inherently nonlinear. A physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection. Climate statistics for warm and cold events of the tropical Pacific are analyzed separately for the northern winter periods during 1950-96. Composite analysis of 500-mb heights reveal planetary-scale teleconnection patterns, as noted in earlier studies. A new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites, and the two wave trains appear to have different tropical origins. A large nonlinear component in North American surface climate anomalies is also found, which is consistent with such a phase shift in teleconnections. In the Tropics, rainfall anomalies also show evidence of nonlinear behavior. The maximum rain anomalies along the equator are located east of the date line during warm events, but west of the date line during cold events. The interpretation of this behavior is complicated, however, by the fact that composite warm event SST anomalies are not the exact inverse of their cold event counterparts. Idealized atmospheric general circulation model (AGCM) experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system. The model is forced with a composite SST anomaly that undergoes a realistic seasonally varying ENSO life cycle, as described by E. Rasmusson and T. Carpenter. Both positive and negative phases of the SST anomaly are used, and a 40-member ensemble of warm and cold event model simulations is conducted. A nonlinear climate response in the AGCM is found that closely resembles the observed composites, including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere. Barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns.

Spatial temperature control with a 27 MHz current source interstitial hyperthermia system

Purpose : This article gives an overview of the properties of a 27 MHz current source interstitial hyperthermia system, affecting temperature uniformity. Methods and Materials : Applicators can be inserted in standard flexible afterloading catheters. Maximum temperatures are measured with seven-point constantan-manganin thermocouple probes inside each applicator. Temperature can be controlled automatically using a simple control algorithm. Three-dimensional power absorption and thermal models for inhomogeneous tissues are available to optimize applicator geometry and phase configuration. Properties of the interstitial heating system have been verified both in phantom experiments and in in vivo treatments of rhabdomyosarcomas implanted in the flank of a rat. Results : An experiment with four electrodes in one catheter proves that longitudinal control fo the specific absorption rate (SAR) is feasible. Local cooling applied by cold water circulation through a catheter perpendicular to the afterloading catheter could be compensated by independent control of electrode power. Furthermore, comparison of two different phase configurations using four dual electrode applicators shows that the SAR distribution can be manipulated significantly, utilizing the phase of the electrodes. Finally, the temperature can be controlled safely and model calculations are in fair agreement with the measurements. Conclusions : The features of the 27 MHz current source interstitial hyperthemia system enable spatial temperature control at approximately 1.5 cm.

寒気循環を伴う重力流

Density currents with cold air circulation are analytically investigated in a 2-dimensional model. Both the propagation speed and depth of density currents are shown to be unaffected by the direction of the cold air circulation for any vorticity distribution. In particular, the propagation speed and depth are explicitly calculated for the case of small vorticities of the cold and warm air masses. The result shows that they increase with the cold air vorticity irrespective of its sign to the leading order approximation. Consistent with the previously published results, they increase also with the warm air vorticity when the vertical integral of the far upstream warm air velocity relative to the ground value is positive.

A New Combustion Process Utilizing Horizontal Wells And Gravity Drainage

Abstract The Combustion Override Split-production Horizontal-well (COSH) process has been conceived to combine the high recovery potential of gravity drainage with the energy efficiency of combustion processes while minimizing problems associated with combustion operations. COSH should be less sensitive to oil composition and combustion kinetics and it has minimal water supply and disposal requirements. The mechanisms for the COSH process have been identified within the limitations of numerical simulation. A simulation study indicates that the COSH process has technical performance approaching that for the highly rated steam-assisted gravity drainage (SAGD) process, and has much lower energy costs. Introduction In-situ combustion has been studied and piloted for several decades because it has the potential of the highest energy efficiency and lowest production cost among thermal processes(1) Unfortunately, overall field experience has been disappointing because of numerous problems such as slow production response difficulty in sustaining combustion, early oxygen breakthrough, severe sanding, gas locking of down-hole pumps, corrosion, and scaling. The literature on combustion studies relates primarily to frontal displacement of the combustion zone. This involves linear or radial areal displacement from vertical injection wells to vertical production wells with the pay-zone visualized as being divided into successive zones including a combustion zone followed by a condensing zone and an oil bank which is displaced ahead of the combustion front. Many elegant and sophisticated studies have been conducted on the dynamics of the combustion process for linear displacement, particularly with combustion tubes(2). Unfortunately, it is very difficult to model in the laboratory the three-dimensional effects of gravity segregation of fluids and poor vertical and horizontal sweep efficiency which are at the heart of many of the problems in field combustion projects. It is also difficult to analyze the process mechanisms in combustion field projects which have been reported to increase oil production. In particular, for field projects it is difficult to determine the relative importance of thermal effects, gravity drainage (particularly in dipping reservoirs) and complex three-phase relative permeability effects caused by the large volumes of gas and water used. This paper will present a new approach to take advantage of the theoretical efficiency of combustion by combining the best features of successful steam pilots that the Alberta Oil Sand Technology and Research Authority (AOSTRA) has participated in while minimizing the negative features responsible for problems reported in earlier field combustion projects. COSH Process The main features in the Combustion Override Split-production Horizontal-well (COSH) process(3) are described as follows, with reference to Figures I and 2:Gas containing oxygen is injected via rows of vertical injection wells. The gas may be air, oxygen or recycled gas with oxygen added. The gas is generally injected in the upper part of the pay-zone. Maintaining continuous gas injection into the reservoir and cold water circulation within the wells will prevent combustion damage. The vertical wells can also serve to define the geology and locate the base of the pay-zone accurately prior to drilling the horizontal production well and they could be used to monitor temperature profiles in the lower part of the gas chamber with cemented-in thermocouples.

Geothermal state of DSDP Holes 333A, 395A AND 534A: Results from the Dianaut Program

Heat‐flow values determined from the DIANAUT program provide insight into the geothermal state of three DSDP holes situated on the western flank of the Mid‐Atlantic Ridge. Very low values (20 mW/m2 max.) observed in 3.5‐m.y.‐old crust at Hole 333A decrease with depth and indicate persistent basement cooling due to cold water circulation in the porous level of the upper oceanic crust. Cold ocean bottomwater continues to invade the upper level of fractured 7.3‐m.y.‐old basement at Hole 395A, but temperature v. time records show large‐scale temperature fluctuations, probably associated with borehole convection, at 500 mbsf and stable temperatures, probably indicating a slow return to thermal equilibrium, at 600 mbsf. The 154‐m.y.‐old crust at Hole 534A exhibits a relatively steady thermal state with a heat flow close to theoretical values for a conductively cooling plate; small variations in the thermal gradient recorded in this well probably represent very slow and subtle movement of borehole fluids. The close comparison of these latest results with those obtained several years previously, demonstrates the presence of relatively stable thermal regimes.

Sound propagation conditions in the equatorial South Pacific Ocean

A major part of the South Pacific Ocean is impacted by a cold water circulation induced by the Antarctic Circumpolar Current. This results in either a double or a very broad deep sound channel axis [R. N. Denham et al., J. Acoust. Soc. Am. 81, 787–789 (1987)]. However, nearer the equator this impact is reduced and a series of equatorial currents and counter currents come into play. An analysis is made of existing oceanographic data to determine the resulting sound‐speed profile shape and sound channel axis depth. A comparison is made to profiles from the temperate regions of the South Pacific Ocean.

Executive Summary of the Ozone Trends Panel Report

The report evidently focuses on global aspects of ozone, and the Antarctic ozone hole is just one part. But it is mainly in the Antarctic, where the extreme cold and unique atmospheric circulation of the southern spring occur, that the evidence for drastic decreases in ozone is unequivocal and where, because of direct measurements of the chemical composition of the statosphere during the Antarctic ozone expeditions, the primary responsibility for ozone depletion can be assigned to CFCs. Small decreases in ozone have been found over the rest of the globe, but they are not yet alarming since they are comparable to natural variations. In fact, most of the decrease in ozone in the Northern Hemisphere from 1979 to 1985 appears to have been associated with the 11-year sunspot cycle and with the reduction in ultraviolet radiation emitted from the sun during that period. As well, previously published reports of much larger decreases in ozone amounts were biased by drift in the calibration of the satellite instruments used, as the executive summary explains.

Once‐a‐day hot circulation cleaning of milking plants

Twice‐a‐day hot circulation cleaning of milking plants was compared with one hot and one cold circulation clean on each of 32 farms practising twice‐a‐day milking. The bacteriological condition and visual cleanliness of plants were monitored over periods of eight weeks for each treatment. Although the geometric mean colony counts of plant rinses were higher for the once‐a‐day hot treatment, it was concluded that one hot and one cold clean gave satisfactory results provided the basic requirements of circulation cleaning were met.

Evidence for cold water circulation at DSDP site 395: Isotopes and chemistry of alteration products

A variety of low temperature alteration products occurs in the 573‐m‐thick section of basaltic rock from Site 395. Carbonate veins, smectites (pre‐dominantly saponite), zeolites, goethite, opal, and gypsum, listed in order of decreasing abundance, are present. Values of δ18O (SMOW) of calcite veins range from +31.8 to +34.8‰, and δ13C (PDB) ranges from +2.3 to +4.4‰. Apparently the calcite veins were formed at 0–15°C in equilibrium with deep ocean water. Some veins may have formed during glacial periods when δ18O of the deep water was higher than it is presently. The deepest calcite veins were formed in the temperature range 8 – 15°C. Saponite veins associated with an intrusive dolerite sill (δ18O = +9.8 to +24.3‰, SMOW) are estimated to have formed in the temperature range 30 – 160°C. Very extensive circulation (i.e., large water/rock ratios) predominated during alteration of the basalts as evidenced by seawater carbon and sulfur isotope ratios in calcite and gypsum and carbon, sulfur and magnesium mass balance considerations.

Global paleoceanography and its deep water linkage to the Antarctic glaciation

Abstract The world climate has changed from equitable global warmth during the Mesozoic to the present glacial climate which is characterized by strong differentiation between warm low latitudes and ice-capped polar regions. Partially at least, this climatic deterioration is due to the progressive dismemberment of the one world ocean, Panthalassa. The global climatic change did not proceed uniformly, but was marked by often very sudden declines and occasional reversals. Many of these sudden events, particularly during the Tertiary, coincide with marked change in the geometry of ocean basins and associated changes in ocean circulation, suggesting a cause and effect relationship between ocean circulation and climate. The most prominent of these events are the formation of an almost circum-Antarctic seaway near the Eocene/Oligocene boundary, coinciding with the beginning of cold deep water circulation; the linkage of the north polar sea to the world deep water circulation during mid-Miocene, leading to the Antarctic ice-cap formation, and the mid-Pliocene closing of the Panamanian isthmus, consituting the final trigger for Northern Hemisphere glaciation.

A Comparison of the relative efficiencies of cold circulation and acidified bioling water cleaning systems for milk parlour pipelines

The relative eficiencies of acidified boiling water used twice per day (A2), acidified boiling water used once per day (A1) and cold circulation (C) cleaning as used on 24 Northern Ireland farms were compared over a nine month period divided into three cleaning periods each of three months. Overall, the A1 system gave inferior results to the A2 and C systems which gave similar results. These diflerences between the cleaning systems were the same in each of the three cleaning periods. When a comparison of cleaning periods was made, irrespective of cleaning systems, it was found that better plant hygiene occurred during the first period (January‐April) than during the other two periods.A periodic hot clean (approximately once per month) was found to be effective in reducing bacterial numbers when the C cleaning system was in operation. It was also found that a build‐up of bacterial numbers occurred on plants during the last two cleaning periods when the A1 and A2 cleaning systems were in operation.Finally, irrespective of the cleaning system employed, it was found that poor plant hygiene prevailed on many of the farms on several occasions.

Thermal conductivity of polyethylene pipes embedded in concrete

Multilayer pipes three inches in diameter were made by casting concrete around 3 4 inch polyethylene pipes of different densities and wall thicknesses. Water at the combination of six temperatures, 35, 45, 100, 125 and 150 °F, and four pressures: 10, 25, 40 and 50 1b/in 2; was circulated through the pipes. The temperatures of the water entering and leaving each pipe were measured and used to calculate the thermal conductivity of the polyethylene pipes. Cyclic effect experiments were also conducted by circulating hot and cold water through the test pipes. Thermal conductivities of the polyethylene pipes were determined after 5, 10, 15 and 20 cycles of hot and cold water circulation.

Some modified forms of hygrometers

The Paper describes experiments made with the object of developing suitable apparatus for the measurement of humidity at low temperatures. The three classical methods - the wet and dry bulb hygrometer, the dew-point apparatus, and the hair hygrometer - were studied and so modified that they could be used in a low temperature room inaccessible to the observer. The common form of wet and dry bulb hygrometer is notoriousl unreliable, but the ventilated form is quite satisfactory provided the wind velocity past the bulb exceeds about 3 meters per second. A tubular form of wet and dry bulb hygrometer was developed with an electric fan for aspiring the air past the bulbs. A continuously-recording, resistance thermometer, type was also made, which had a cam device for rapidly dipping and withdrawing the thermometer bulb at periodic intervals from a reservoir of water. The dew-point apparatus was modified into a form suitable for permanent installation; the cooling of the polished metal surface being effected by pipe connections to the cold brine circulation of the stores. In another form a silver thimble, cooled by the evaporation of ether, was placed at one end of a long aluminium tube and a telescope at the other. By suitable arrangements of mirrors and lamps both the silver surface and the thermometer column were thrown into the field of the telescope. The end containing the thimble was inserted into the enclosure through a circular aperture. The instrument was portable and self-contained. A distant reading type of dew-point apparatus was constructed, in which the formation of dew was indicated by the change of reflecting power of the cooled surface. A beam of heat radiation was reflected from the polished surface and concentrated on to a minute thermopile. The thermo-junctions were connected to a pivoted indicator situated at the observation station where the observer controlled the flow of cooling fluid by means of a solenoid valve. The formation of dew resulted in a sharp falling-off of the reflecting power and was indicated by the movement of the pointer of the instrument. The hair hygrometer was studied under a variety of conditions and the changes in the calibration of this type of instrument, caused by exposure to low and high temperature, &c., were determined. A very simple form of distant reading hair hygrometer was developed. In this the clockwork drum of the ordinary recorder was replaced by a tubular rheostat. The pointer was pressed into contact with the drum when a reading of the humidity was desired. The two portions of the resistance winding then constituted the two arms of a Wheatstone's bridge. A number of other forms of hygrometers were also studied, notably the one utilising the heating effect on dry cotton when exposed to a humid atmosphere. A convenient form of apparatus for the calibration of hygrometers over a wide range of humidities is described. It consists essentially of a drum fitted with a heavy glass front making an air-tight joint. The drum contains an electric fan which circulates the air over a dish of strong sulphuric acid. This method of reducing the humidity is more effective than bubbling and does not produce acid spray. The acid dish can be cut out of communication with the chamber by a ground glass cover operated by a lever projecting out of the drum.