Book review     

Charles Fairhurst  Renata Dmowska  Gregory L. Duckworth  Brian J. Mitchell  David V. Wiltschko  Charles G. Sammis 《Pure and Applied Geophysics》1985,123(5):791-803

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Characteristics and origins of lee-side stratification sequences in late pleistocene drumlins,northern Ireland     

George F. Dardis  A. Marshall McCabe  W. Ian Mitchell 《地球表面变化过程与地形》1984,9(5):409-424

Spindle- and parabolic-shaped drumlins examined at fifty-five localities in northern Ireland possess stratification sequences on their lee-side flanks. These forms lack the distinctive steep stoss- and tapering lee-ends of classical drumlins and tend to occur in linear zones transverse to late Pleistocene ice-flow. In most cases (90 per cent) the stratified deposits infill embayments excavated in the lee-side of barkhanoid forms and, in the remainder (10 per cent), they are superimposed on the lee-side of whaleback forms. The stratification sequences developed as a result of sedimentation in interconnected subglacial water-filled cavities and are unlike remanie proglacial sediments moulded by ice into drumlin form. Stratigraphic evidence indicates that the lee-side sequences developed during drumlin streamlining, which supports the view that subglacial hydraulic processes played an important role in drumlin formation.  相似文献   

Comparative growth of juvenile white sturgeon and striped bass: Effects of temperature and hypoxia   总被引：1，自引：0，他引：1  

Joseph J. Cech  Stephen J. Mitchell  Trent E. Wragg 《Estuaries and Coasts》1984,7(1):12-18

The influences of temperature and environmental hypoxia on the growth rates of two California anadromous fishes, white sturgeon (Acipenser transmontanus) and striped bass (Morone saxatilis) were examined. Fish (0.5–0.6 g initial weight) were fedad libitum rations ofArtemia in flow-through aquaria regulated for temperature (15, 20, and 25°C) and oxygen tension (130 and 90 torr P_{o 2}). Growth of sturgeon was significantly greater at 20 °C compared with 15 °C, but there was no difference between 20 and 25 °C. Striped bass growth increased with each 5° increment of temeprature elevation to 3.2% body weight per d at 25 °C, the fastest growth rate measured. The temperature of maximum growth reflected the temperature of the native estuarine rearing area. Environmental hypoxia (90 torr P_{o 2}) reduced growth of sturgeon within each temperature level, whereas striped bass growth was reduced by hypoxia only at the upper two temperatures. Sturgeon were much more active in the growth chambers than striped bass. Sturgeon activity increased with each 5 °C temperature increase under normoxia and hypoxia, except at 25 °C (hypoxia) where activity was insignificantly different from that at 20 °C (hypoxia).  相似文献   

Zonal and meridional circulations in the equatorialzone as deduced from the divergence field of the surface wind     

Wang Shaowu  Todd P. Mitchell  John M. Wallace 《大气科学进展》1987,4(4):432-446

The zonal and meridional circulations and their variability are examined on the basis of the surface wind data for 1950-1979. The climatological mean zonal wind and its divergence are examined in reference to the Walker Circulation. The role played by the meridional circulation in contributing to convergence of the surface wind field within the equatorial zone is emphasized. Regression coefficients are used to infer seasonal mean anomalies of divergence of the surface wind in years when the sea level pressure is 1 hPa above normal at Darwin, a condition representative of El Nino events. It is shown that anomalies in the divergence associated with the meridional wind component are primarily responsible for the heavy precipitation in the Central Pacific, while the anomalous divergence associated with the zonal wind component may cause the drought in the Western Pacific near Indonesia. A similar pattern of divergence anomalies is evident during three consecutive seasons beginning in northern summer and ending in northern winter. The reinforcement of the Hadley Circulation during El Nino episodes is noted. It is shown that the circulations over the Atlantic Ocean and Pacific Ocean are relatively uncorrelated. The interrelation between the dipole anticyclones and the meridional cir-culation over the central Pacific is discussed.  相似文献   

Simulated climate and CO2—Induced climate change over Western Europe     

C. A. Wilson  J. F. B. Mitchell 《Climatic change》1987,10(1):11-42

The use of a relatively high resolution general circulation model (the Meteorological Office 5-layer model) to determine climate changes for impact studies is evaluated. The simulation of present day climate over Western Europe is assessed by comparing not only different seasons with climatological data, but also the mean annual cycle and the frequency of extreme events. It is found that while the broad features of the simulation are satisfactory, the model produces too many cold episodes in spring, and an excessive number of wet days over northern Europe. When atmospheric CO₂ concentrations are quadrupled, and sea surface temperatures and sea ice extents changed appropriately, the number of cold episodes is reduced and precipitation is less frequent in summer and autumn over much of Europe, and throughout the year in the south. The relevance of both the model data and the statistical tests to climate impact studies is discussed.  相似文献   

Book review     

William D. Stuart  Kacper Rybicki  Brian J. Mitchell  Daniel Moos  Jeanne Sauber  Bernard Vonnegut  Ross J. Salawitch  David S. Gutzler 《Pure and Applied Geophysics》1987,125(5):853-855

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Impaired osmoregulation in the shrimp Palaemon adspersus exposed to crude oil extract     

Susanne Pihl Baden 《Marine pollution bulletin》1982,13(6):208-210

Palaemon adspersus is a hyper- and hypo-osmoregulating shallow-water shrimp. For a maximum period of 34 days P. adspersus were exposed to 20, 70, 100 and 200 ppb WSF of North Sea crude oil. The osmotic concentration of the haemolymph was measured by freezing point depression once a week. The ability to maintain hyper-osmolality was significantly decreased (p<0.05) after one, two and three weeks exposure to 200, 70 and 100 ppb, respectively. No effect was observed in 20 ppb. After an accidental exposure of shrimps to 24 h acute oil pollution, they were placed in pure sea water. The ability to maintain hyper-osmolality was reduced one week after the accidental oil exposure, but was regained within three weeks.  相似文献   

WAVE HEIGHTS IN THE SURF ZONE     

H. L. Mitchell 《The Photogrammetric Record》1983,11(62):183-193

The advantages and disadvantages of measuring ocean wave heights in the surf zone by using terrestrial photogrammetry are outlined. Difficulties arising from a lack of control points can be overcome by using the apparent horizon to provide camera orientations about two axes, provided that the apparent horizon is the sea surface and that an unconventional orientation of the camera axis system is adopted. Following practical tests and error simulation studies, height differences were determined for 12 points in the breaking wave zone off a Newcastle (New South Wales) beach. It is hoped that the method can be developed as a convenient means of collecting wave data.  相似文献   

Impact assessments and policy responses to sea-level rise in three US states: An exploration of human-dimension uncertainties   总被引：2，自引：0，他引：2  

Susanne C. Moser   《Global Environmental Change》2005,15(4):353-369

Uncertainties in the human dimensions of global change deeply affect the assessment and responses to climate change impacts such as sea-level rise (SLR). This paper explores the uncertainties in the assessment process and in state-level policy and management responses of three US states to SLR. The findings reveal important political, economic, managerial, and social factors that enable or constrain SLR responses; question disasters as policy windows; and uncover new policy opportunities in the history of state coastal policies. Results suggest that a more realistic, and maybe more useful picture of climate change impacts will emerge if assessments take more seriously the locally embedded realities and constraints that affect individual decision-makers’ and communal responses to climate change.  相似文献   

Towards evaluating cloud response to climate change using clustering technique identification of cloud regimes     

Keith D. Williams  Catherine A. Senior  Anthony Slingo  John F. B. Mitchell 《Climate Dynamics》2005,24(7-8):701-719

Most of the discrepancies in the climate sensitivity of general circulation models (GCMs) are believed to be due to differences in cloud radiative feedback. Analysis of cloud response to climate change in different ‘regimes’ may offer a more detailed understanding of how the cloud response differs between GCMs. In which case, evaluation of simulated cloud regimes against observations in terms of both their cloud properties and frequency of occurrence will assist in assessing confidence in the cloud response to climate change in a particular GCM. In this study, we use a clustering technique on International Satellite Cloud Climatology Project (ISCCP) data and on ISCCP-like diagnostics from two versions of the Hadley Centre GCM to identify cloud regimes over four different geographical regions. The two versions of the model are evaluated against observational data and their cloud response to climate change compared within the cloud regime framework. It is found that cloud clusters produced by the more recent GCM, HadSM4, compare more favourably with observations than HadSM3. In response to climate change, although the net cloud response over particular regions is often different in the two models, in several instances the same basic processes may be seen to be operating. Overall, both changes in the frequency of occurrence of cloud regimes and changes in the properties (optical depth and cloud top height) of the cloud regimes contribute to the cloud response to climate change.  相似文献