Anomalous Temperatures Research Articles

What is happening near Sq focus?

Abstract Rocket measurements of electron temperatures (Te) in the E region over Kagoshima Space Center, Japan, carried out in a serees of experiments conducted from 1970 to 1988 are analysed in this paper. All the 13 flights whose results are presented here took place around 11 AM, close to the Sq current intensity maximum. Anomalously high electron temperatures associated with large increases of high energy tail electron population were observed whenever the estimated Sq current vortex was very close to the launch site. Such anomalous temperatures were observed only in local winter months. A mechanism for the anomalous heating is proposed based on the solsticial asymmetry of the Sq electric potentials and the resulting field-aligned current that could flow from winter to summer hemisphere.

Deep mantle plume osmium isotope signature from West Greenland Tertiary picrites

Picrites from Nuussuaq Peninsula and Qeqertarssuaq (Disko) Island, West Greenland, preserve trace element and isotopic signatures reflecting the composition of the Icelandic plume head. Os isotope ratios are low (187Os/188Os(i)=0.1272–0.1371) in terms of global plume related magmatism, and this is coupled with anomalously high Os abundances and radiogenic 143Nd/144Nd(i) isotopes. Crustally contaminated basalts within the West Greenland sequences possess Os and Nd isotopic signatures consistent with mixing between initial plume head compositions and two discrete types of West Greenland continental crust. One crustal component is of a local sedimentary origin, and the other is typical of ancient felsic crust. The low Os isotopic signatures of the picritic units are considered to be those of the initial mantle plume. The fact that such low Os isotope ratios occur in sequences with high 3He/4He, and the non-systematic variation in Os isotopes with indices of fractionation/accumulation and Pb isotopes, argue against mixing with depleted MORB mantle or ancient subcontinental lithospheric mantle. The high Os concentrations in the picrites are attributed to high degrees of partial melting (>25%) of mantle containing no residual sulphide. This is consistent with models for plume heads in which anomalous mantle temperatures initiate melting at high pressures generating large degrees of partial melting. Unradiogenic Os and radiogenic Nd components in plume-related CFB magmatism may preserve contributions from a reservoir which is sampled only occasionally in young oceanic basalts. Such a reservoir shares Os isotopic features with the primitive upper mantle (PUM), which may also be manifest in the ‘Kea’ component of Hawaiian magmatism. Therefore, portions of the West Greenland continental flood basalt province arguably represent the first direct sampling of unmodified plume head material derived from the lower mantle or lower portions of the upper mantle.

The Effect of the 1997/98 El Niño on Individual Large-Scale Weather Events

Can an individual weather event be attributed to El Nino? This question is addressed quantitatively using ensembles of medium-range weather forecasts made with and without tropical sea surface temperature anomalies. The National Centers for Environmental Prediction (NCEP) operational medium-range forecast model is used. It is found that anomalous tropical forcing affects forecast skill in midlatitudes as early as the fifth day of the forecast. The effect of the anomalous sea surface temperatures in the medium range is defined as the synoptic El Nino signal. The synoptic El Nino signal over North America is found to vary from case to case and sometimes can depart dramatically from the pattern classically associated with El Nino. This method of parallel ensembles of medium-range forecasts provides information about the changing impacts of El Nino on timescales of a week or two that is not available from conventional seasonal forecasts. Knowledge of the synoptic El Nino signal can be used to attribute aspect...

The influence of a stratified rheology on the flexural response of the lithosphere to (un)loading by extensional faulting

SUMMARY We present a two-layered finite diVerence model for the flexural response of the lithosphere to extensional faulting. The model allows for three modes of flexure: (1) fully coupled, with the upper crust and mantle welded together by the lower crust; (2) fully decoupled, with the upper crust and mantle behaving as independent layers; and (3) partly decoupled, signifying that the response of the upper crust to small-wavelength loads is superimposed on the response of the entire lithosphere to long-wavelength loads. Which of these modes of flexure is to be expected depends on the rheology and especially the thermal state of the lithosphere. Coupled behaviour is related to a cold and strong lithosphere. The Baikal Rift Zone provides a typical example for this mode of flexure. A fully decoupled lithosphere is an exceptional case, related to anomalous high temperatures in the lower crust, and is observed in the Basin and Range province. The most common case is a partly decoupled lithosphere, with the degree of decoupling depending on the thickness and viscosity of the lower crust. This is inferred, for example, for the Bay of Biscay margin.

Anomalous sea surface temperatures and local air-sea energy exchange on intraannual timescales in the northeastern subtropical Pacific

Anomalous sea surface temperatures and local air-sea energy exchange on intraannual timescales in the northeastern subtropical Pacific

Interdecadal Climate Fluctuations That Depend on Exchanges Between the Tropics and Extratropics

The unexpected and prolonged persistence of warm conditions over the tropical Pacific during the early 1990s can be attributed to an interdecadal climate fluctuation that involves changes in the properties of the equatorial thermocline arising as a result of an influx of water with anomalous temperatures from higher latitudes. The influx affects equatorial sea-surface temperatures and hence the tropical and extratropical winds that in turn affect the influx. A simple model demonstrates that these processes can give rise to continual interdecadal oscillations.

Anomalous Sea Surface Temperatures and Local Air–Sea Energy Exchange on Intraannual Timescales in the Northeastern Subtropical Pacific*

Abstract Here 11 years of surface data (1961–72, excluding 1963) taken at ocean weather ship N (OWS N) are analyzed. OWS N is located in the subtropical eastern Pacific Ocean (140°W, 30°N). Bulk formulas are employed to calculate each component of the surface heat flux (sensible, latent, longwave, and shortwave) from the 3-h measurements of sea surface temperature (SST), air temperature, surface humidity, wind speed, and cloudiness. Analyses are performed on fluxes averaged over daily and monthly intervals. Results indicate a large fraction of the variance in net surface energy flux is associated with anomalies in the latent heat flux; the latter are principally due to variability in the surface wind speed. Cross correlation and regression analyses of monthly anomalies of SST and SST tendency (∂SST/∂t) with the surface heat flux components indicate over 50% of the variance in SST-tendency anomalies is accounted for by local anomalies in the net surface energy flux. In the summer, the summed variance in th...

Assessing a GCM's Suitability for Making Seasonal Predictions

Abstract This study investigates the predictability of seasonal mean circulation anomalies associated purely with the influence of anomalous sea surface temperatures (SSTs). Within this framework, seasonal mean atmospheric anomalies on a case by case basis are understood to consist of a potentially predictable boundary-forced component and an unpredictable naturally varying component. The predictive capability of an atmospheric general circulation model (AGCM) for seasonal timescales should therefore be assessed in terms of the average skill over many cases, since it is only then that the boundary-forced predictable signal in observations can be identified. To illustrate, experiments for 1982–1993 using two versions of an AGCM are presented. The models, referred to here as MRF8 and MRF9, differ in the parameterization of a single process. Each model is run nine times for the 12 years using different initial conditions but identical observed global SSTS. The nine-member ensemble mean anomalies for each sea...

Hurricane vane

The 1995 hurricane season in the Atlantic is likely to be near average, according to William M. Gray of Colorado State University in Fort Collins. Gray forecasts about 6 hurricanes, 10 named storms, 50 named storm days, 25 hurricane days, 2 intense hurricanes, 5 intense hurricane days, and a hurricane destruction potential of 75, which is a measure of a hurricane's potential for wind and storm surge destruction. The 1995 season should be more active that the four previous hurricane seasons, says Gray who presented his findings at the 17th Annual National Hurricane Conference in Atlantic City, N.J. However, Gray downgraded his expectations for a very active Atlantic tropical storm season because of new data on anomalous Atlantic sea surface temperatures and Caribbean sea level pressures.

Anomalous Anomalies in Averaged Hydrographic Data

Abstract A comparison of a recently assembled hydrographic database for the North Atlantic with the Lovitus atlas shows striking differences in the vicinity of the Gulf Stream and the North Atlantic Current. On isopycnal surfaces in the main thermocline, isolated pools of warm, saline water are found in the Levitus database but are absent in the new database. Using synoptic data as a proxy for temporally averaged climatological data, it is shown that the anomalous features can be accounted for by the differences in the averaging process. To produce a gridded database from irregularly spaced station data, Levitus averaged the data on pressure surfaces while the new database was prepared with averaging an potential density surfaces. It is shown that averaging on a pressure surface in an area of sharply sloping isopycnals produces a water mass with a θ–S signature uncharacteristic of the local water mass(es). The anomalous potential temperatures and salinities that result are compared to the large-scale wate...

Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal‐body theory

The spatial correlation between a horizontal gradient in heat flow and a horizontal gradient in residual gravity in the Western Cascades of central Oregon has been interpreted by others as evidence of the western edge of a pervasive zone of high temperatures and partial melting at midcrustal depths (5–15 km). Both gradients are steep and relatively linear over north‐south distances in excess of 150 km. The Western Cascades gravity gradient is the western margin of a broad gravity depression over most of the Oregon Cascade Range, implying that the midcrustal zone of anomalous temperatures lies throughout this region. Ideal‐body theory applied to the gravity gradient, however, shows that the source of the Western Cascades gravity gradient cannot be deeper than about 2.5 km and is considerably shallower in some locations. These calculations are unique determinations, assuming that density contrasts associated with partial melting and elevated temperatures in the crust do not exceed 500 kg m−3. Consequently, the gravity gradient and the heat flow gradient in the Western Cascades cannot be caused directly by the same source if the heat flow gradient originates at midcrustal depths. This conclusion in itself does not disprove the existence of a widespread midcrustal zone of anomalously high temperatures and partial melting in this area, but it does eliminate a major argument in support of its existence. The gravity gradient is most likely caused by lithologic variations in the shallow crust, perhaps reflecting a relict boundary between the Cascade extensional trough to the west and Tertiary oceanic crust to the west. The boundary must have formed prior to Oligocene time, the age of the oldest rocks that now conceal it.

Geophysical survey as a basis for regeneration of waste dump Halde 10, Zwickau, Saxony

About 90 years ago a natural depression in the vicinity of the town of Zwickau was filled with waste left after floatation of coal exploited in the area. Later on the locality became a dumping site for municipal and industrial waste from the town of Zwickau. Waste was disposed for years without any records, and at the present time the town faces an uneasy task of securing a harmless and controlled operation of the waste dump in accordance with environmental laws now in effect in Germany. A project has been launched sponsored by the ENMOTEC GmbH, company. Tübingen, subsidiaries Freiberg and Zwickau. At the initial stages of the project an important role was played by geophysical methods applied in mapping the tectonic structure of the dumping area including other desirable geological information, mapping the extent, distribution and thickness of floatation coal layers within the mound, and mapping the disposed refuse itself. The following geoelectric methods were applied: resistivity profiling, VLF and VES. They proved to be effective tools of investigation in the specific conditions of an operating dump. Results of these measurements are presented in graphic form in schematic situation of tectonic faults and lithological boundary-lines and in a geological profile of the dump. On the basis of geophysical results monitoring boreholes were placed in the vicinity of the dump. Layers of floatation coal and of municipal and industrial waste were delineated. Another aim of the geophysical survey was to find out whether there were any active processes going on in the disposed coal refuse. A temperature survey was carried out over the dumping area in a network of points at two depth levels, 0.5 and 1 m under the surface. Localitions of anomalous temperatures with a relative increase of over 20°C and maximum values of over 40°C at 1 m depth were mapped. At the final stage of the geophysical survey logging measurements were conducted in 10 cased monitoring boreholes in the surrounding of the dump. Measurements of total gamma activity of rocks were carried out, and measurements of physical properties of fluids in the boreholes: temperature (TM), transparency (FM) and resistivity (RM). Resistivity fluid log and photometry were applied for determination of groundwater dynamics in boreholes by measuring the time cycle of RM and FM curves after sodium chloride or nigrosine dye had been added to the mud fluid. These special measurements resulted in locating water inflows and leakages from the boreholes, and in mapping water circulation in the boreholes. Information on groundwater quality, stratification, temperature and filtration rate served as a basis for projecting and installing an effective monitoring system.

The Global Climate of December 1991–February 1992: Mature-Phase Warm (ENSO) Episode Conditions Develop

The December 1991-February 1992 (DJF 91/92) season featured global scale atmospheric circulation, temperature, and precipitation anomalies consistent with those generally found during the mature phase of tropical Pacific warm ENSO episodes. The anomalous upper-tropospheric circulation features usually observed developed slowly during the season, but were well developed by February. The tropical and subtropical precipitation anomaly patterns reflected mature-phase ENSO conditions. A persistent anomalous circulation pattern in Europe was associated with highly anomalous temperatures and precipitation in sections of Europe and the eastern Mediterranean. 14 refs., 18 figs., 1 tab.

Role of Nonthermal Velocity Fluctuations on Anomalous Impurity Temperatures in the TJ-I Tokamak

Role of Nonthermal Velocity Fluctuations on Anomalous Impurity Temperatures in the TJ-I Tokamak

Influence of terrain on bedrock temperatures

Changing terrain and underground water flows can produce anomalous underground temperatures similar to those expected from climatic changes. They can also modify the anomalies produced by past climatic changes. If these effects or their causes are not recognized, incorrect past climatic changes may be inferred from the subsurface temperatures. Three examples of terrain effects are presented and analysed: a warm lake, representing spatial differences in terrain; a deforested region, representing a temporal change in terrain; and small water flows, representing an indirect effect of terrain. There is a better chance of recognizing small anomalies due to terrain by using very accurately measured temperatures and a good representation of the thermal conductivity of the rock. Repeat temperature logs of the same hole and/or more holes in the same region also improve the detection of these effects, especially those caused by small, variable water flows. The relation of ground temperature to air temperature is a function of terrain. At two of these locations the effects of snow and surface water (shallow lakes, swampy areas) on average ground temperatures are large. Consequently climatic changes affecting either the average snow cover or precipitation and drainage at these sites would also change the average ground surface temperature even if the average air temperature remained constant. Similarly, deforestation produces directly a large warming of the ground surface (up to 4 K).

Influence of terrain on bedrock temperatures

Changing terrain and underground water flows can produce anomalous underground temperatures similar to those expected from climatic changes. They can also modify the anomalies produced by past climatic changes. If these effects or their causes are not recognized, incorrect past climatic changes may be inferred from the subsurface temperatures. Three examples of terrain effects are presented and analysed: a warm lake, representing spatial differences in terrain; a deforested region, representing a temporal change in terrain; and small water flows, representing an indirect effect of terrain. There is a better chance of recognizing small anomalies due to terrain by using very accurately measured temperatures and a good representation of the thermal conductivity of the rock. Repeat temperature logs of the same hole and/or more holes in the same region also improve the detection of these effects, especially those caused by small, variable water flows. The relation of ground temperature to air temperature is a function of terrain. At two of these locations the effects of snow and surface water (shallow lakes, swampy areas) on average ground temperatures are large. Consequently climatic changes affecting either the average snow cover or precipitation and drainage at these sites would also change the average ground surface temperature even if the average air temperature remained constant. Similarly, deforestation produces directly a large warming of the ground surface (up to 4 K).

Observations of thermospheric temperatures at 23°S

Observations of night-time thermospheric temperatures from measurements of Doppler widths of the OI 630.0 nm airglow emission line, using a Fabry-Perot interferometer, have been carried out from 23°S geographic latitude in the Brazilian sector, during the period March 1988–October 1989. The observing location is situated inside both the equatorial ionospheric and South Atlantic magnetic anomalies. In this paper we present and discuss salient features of the average nocturnal variations of the thermospheric temperature during equinox and winter seasons. The results are compared with the thermospheric temperatures predicted by the MSIS-86 model. The observed temperatures are in good agreement compared with the MSIS-86 model temperatures. They are comparable with those reported from other low latitude stations and no anomalous high thermospheric temperatures have been observed in this region of the South Atlantic magnetic anomaly.

Deformation of single-crystal Mn 3Sn

Single-crystal Mn 3Sn was chosen to investigate the behavior of a DO 19 intermetallic compound. The alloy of composition 23.75 at.% Sn was made from the pure elemental materials and single crystals were grown using the Bridgman process. Compression samples were prepared using an electric discharge machine and tested at moderate strain rates in an air or argon environment, depending upon the test temperature. Testing temperatures ranged from 77 to 1200 K and various orientations within the standard unit triangle were chosen so as to produce slip on several slip systems. Preliminary results show that the dominant mode of deformation is basal slip accompanied by an anomalous flow stress vs. temperatures behavior. There was, however, also some prismatic and pyramidal slip observed. For most orientations slip traces were observed on the sample surfaces; however, for some orientations with low Schmid factors, local crushing or even brittle fracture were observed.

A three-dimensional theory of wind pumping

AbstractQuantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source.Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface.

A three-dimensional theory of wind pumping

AbstractQuantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source.Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface.