The roles of radiation and dynamical processes in the El Niño-like response to global warming     

B. Yu  G. Boer 《Climate Dynamics》2002,19(5-6):539-554

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A multicolour CCD photometric and mass function study of the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253     

Ram Sagar  U. Munari  K.S. de Boer 《Monthly notices of the Royal Astronomical Society》2001,327(1):23-45

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Seasonal climatic variability     

G. J. Boer  K. Higuchi 《大气与海洋》2013,51(2):90-102

Abstract

An analysis of variance of the 1000–500 mb thickness field is performed to investigate the possibility of seasonal change in climatic variability during the period 1949 to 1975.

The mean thickness and measures of transient eddy, standing eddy and north‐south variance, averaged over the region from 25°N to the Pole, are analysed for the annual average and for each of the four seasons. For the annually averaged data, the only statistically significant trend is a linear decrease in mean thickness. None of the variability measures display significant trends in annually averaged values.

On a seasonal basis, a significant trend in mean thickness is found in three of the four seasons. Several seasonal measures of variability show statistically significant trends. The most notable result of the analysis is an apparent increasing trend in summer season values of both transient and standing eddy measures of variability.

The results of this study reiterate those of a previous study that found no overall change in climatic variability during the period. In addition, however, the data suggest an increase in variability during the summer season although this increase is not sufficient to affect the overall annually averaged value.  相似文献   

Organotins (TBT and DBT) in water, sediments, and gastropods of the southern Venice lagoon (Italy)   总被引：3，自引：0，他引：3  

Berto D  Giani M  Boscolo R  Covelli S  Giovanardi O  Massironi M  Grassia L 《Marine pollution bulletin》2007,55(10-12):425-435

The release of tributyltin (TBT) from maritime traffic represents one of the main problems of direct, diffuse, and continued contamination of the marine environment. In the present survey, the concentrations of TBT and dibultytin (DBT) in brackish waters, sediments, and the gastropods Nassarius nitidus were evaluated in order to estimate the contamination of the southern part of the Venice lagoon. TBT and DBT were determined by GC-MS/MS. Recent contamination of TBT was found in brackish waters near marinas, whereas the highest concentrations of TBT and DBT were observed in surface sediments at dockyards and harbours. High content of organotin in the gastropods sampled near the dockyards, harbours, and marinas showed a mobilisation from the sediments through the food web. The present study allowed assessment of whether, despite the ban on the use of TBT paints, waters, sediments, and biota were still being contaminated by organotin compounds in the southern Venice lagoon.  相似文献   

Structure and variances of equatorial zonal circulation in a multimodel ensemble     

B. Yu  F. W. Zwiers  G. J. Boer  M. F. Ting 《Climate Dynamics》2012,39(9-10):2403-2419

The structure and variance of the equatorial zonal circulation, as characterized by the atmospheric mass flux in the equatorial zonal plane, is examined and inter-compared in simulations from 9 CMIP3 coupled climate models with multiple ensemble members and the NCEP-NCAR and ERA-40 reanalyses. The climate model simulations analyzed here include twentieth century (20C3M) and twenty-first century (SRES A1B) simulations. We evaluate the 20C3M modeled zonal circulations by comparing them with those in the reanalyses. We then examine the variability of the circulation, its changes with global warming, and the associated thermodynamic maintenance. The tropical zonal circulation involves three major components situated over the Pacific, Indian, and Atlantic oceans. The three cells are supported by the corresponding diabatic heating extending deeply throughout the troposphere, with heating centers apparent in the mid-troposphere. Seasonal features appear in the zonal circulation, including variations in its intensity and longitudinal migration. Most models, and hence the multi-model mean, represent the annual and seasonal features of the circulation and the associated heating reasonably well. The multi-model mean reproduces the observed climatology better than any individual model, as indicated by the spatial pattern correlation and mean square difference of the mass flux and the diabatic heating compared to the reanalysis based values. Projected changes in the zonal circulation under A1B forcing are dominated by mass flux changes over the Pacific and Indian oceans. An eastward shift of the Pacific Walker circulation is clearly evident with global warming, with anomalous rising motion apparent over the equatorial central Pacific and anomalous sinking motions in the west and east, which favors an overall strengthening of the Walker circulation. The zonal circulation weakens and shifts westwards over the Indian Ocean under external forcing, whereas it strengthens and shifts slightly westwards over the Atlantic Ocean. The forced circulation changes are associated with broad SST and atmospheric diabatic heating changes in the tropics. Linear trends of these forced circulation changes, as characterized by regional spatial maximum amplitudes of mass fluxes and their longitudes over the three oceans, are statistically significant at the 5?% level for 2000–2099 for the multi-model mean. However, wide differences of the trends are apparent across the models, because of both deficiencies in the simulation of the circulations in different models and the high internal variability of the circulations.  相似文献   

QBO influence on extratropical predictive skill     

G. J. Boer  K. Hamilton 《Climate Dynamics》2008,31(7-8):987-1000

The quasi-biennial oscillation (QBO) in the zonal wind in the tropical stratosphere is one of the most predictable aspects of the circulation anywhere in the atmosphere and can be accurately forecast for many months in advance. If the stratospheric QBO systematically (and significantly) affects the tropospheric circulation, it potentially provides a predictable signal useful for seasonal forecasting. The stratospheric QBO itself is generally not well represented in current numerical models, however, including those used for seasonal prediction and this potential may not be exploited by current numerical-model based forecast systems. The purpose of the present study is to ascertain if a knowledge of the state of the QBO can contribute to extratropical boreal winter seasonal forecast skill and, if so, to motivate further research in this area. The investigation is in the context of the second Historical Forecasting Project (HFP2), a state-of-the-art multimodel two-tier ensemble seasonal forecasting system. The first tier, consisting of a prediction of sea surface temperature anomalies (SSTAs), is followed by the second tier which is a prediction of the state of the atmosphere and surface using an AGCM initialized from atmospheric analyses and using the predicted SSTs as boundary conditions. The HFP2 forecasts are successful in capturing the extratropical effects of sea surface temperature anomalies in the equatorial Pacific to the extent that a linear statistical correction based on the NINO3.4 index does not provide additional extratropical skill. By contrast, knowledge of the state of the stratospheric QBO can be used statistically to add extratropical skill centred in the region of the North Atlantic Oscillation. Although the additional skill is modest, the result supports the contention that taking account of the QBO could improve extratropical seasonal forecasting skill. This might be done statistically after the fact, by forcing the QBO state into the forecast model as it runs or, preferably, by using models which correctly represent the physical processes and behaviour of the QBO.  相似文献   

南非Sabie-Pilgrim's Rest金矿田中温热液型矿化作用     

Ｒ．Ｈ．Ｂｏｅｒ  赵子基  陈树旺 《地质与资源》1997,6(1):72-76

南非Ｓａｂｉｅ－ＰｉｌｇｒｉｍｓＲｅｓｔ金矿田中温热液型矿化作用１地质背景在Ｓａｂｉｅ－ＰｉｌｇｒｉｍｓＲｅｓｔ地区，Ｗｏｌｋｂｅｒｇ群原生盆积物构成了元古宇Ｔｒａｎｓｖａａｌ超群的最底部．它不整合于Ｎｅｌｓｐｒｕｉｔ岩基之上．后者由巨大的花岗闪...  相似文献   

Numerical convergence of the dynamics of a GCM   总被引：1，自引：0，他引：1  

G. J. Boer  B. Denis 《Climate Dynamics》1997,13(5):359-374

 Atmospheric general circulation models (GCMs) are characterized by many features but especially by: (1) the manner of discretizing the governing equations and of representing the variables involved at a given resolution, and (2) the manner of parameterizing unresolved physical processes in terms of those resolved variables. These two aspects of model formulation are not independent and it is difficult to untangle their intertwined effects when assessing model performance. The attempt here is to separate these aspects of GCM behaviour and to ask, “Given a perfect parameterization of the physical processes in a model, what resolution is needed to capture the dominant dynamical aspects of the atmospheric climate?” Alternatively, “At what resolution do the dynamics of a GCM converge”? The perfect parameterization approach assumes that the calculation of the physical terms returns the “correct” result at all resolutions. In the idealized case, a time-independent forcing is one of the simplest that satisfies this condition. However, experiments show that it is difficult for the dynamics of a GCM to balance a time-independent forcing with atmosphere-like flows and structures. The model requires, and the atmosphere presumably includes, physical feedback mechanisms which act so as to maintain the kinds of flows and structures that are observed. Resolution experiments are performed with a simplified forcing function for the thermodynamic equation which combines a dominant time-independent specified forcing with a weak linear relaxation feedback. These experiments show that the dynamics of the GCM have essentially converged at T32 and certainly by T63 which is the next resolution considered. This is shown by the constancy of structures, variances, covariances, transports and energy budgets with increasing resolution. Experiments with an alternative forcing proposed by Held and Suarez, which has the form of a linear relaxation, show somewhat less evidence of convergence at these resolutions. In both cases the “physics” are known by assumption. However, the form and nature of the forcing is different, as is the behaviour with resolution. The implication for the real system is that the resolution required for simulating the dynamical aspects of climate is rather modest. The simulated climate does, however, apparently depend on the ability to correctly and consistently parameterize the physical processes in a GCM, involving both forcing and feedback mechanisms, as a function of resolution. Received 19 January 1996/Accepted 22 August 1996  相似文献   

The nonlinear association between the Arctic Oscillation and North American winter climate     

Aiming Wu  William W. Hsieh  Amir Shabbar  George J. Boer  Francis W. Zwiers 《Climate Dynamics》2006,26(7-8):865-879

Nonlinear projections of the Arctic Oscillation (AO) index onto North American winter (December–March) 500-mb geopotential height (Z500) and surface air temperature (SAT) anomalies reveal a pronounced asymmetry in the atmospheric patterns associated with positive and negative phases of the AO. In a linear view, the Z500 anomaly field associated with positive AO resembles a positive North Atlantic Oscillation pattern with statistically significant positive and negative anomalies stretching zonally into central-eastern USA and Canada, respectively, resulting in a cold climate anomaly over northeastern and eastern Canada, Alaska and the west coast of USA, and a warm climate anomaly over the rest of the continent. By contrast, the nonlinear behavior, mainly a quadratic association with AO, which is most apparent when the amplitude of the AO index is large, has the same spatial pattern and sign for both positive and negative values of the index. The nonlinear pattern reveals negative Z500 anomalies over the west coast of USA and the North Atlantic and positive Z500 anomalies at higher latitudes centered over the Gulf of Alaska and northeastern Canada accompanied by cooler than normal climate over the USA and southwestern Canada and warmer than normal climate over other regions of the continent. A similar analysis is conducted on the data from the Canadian Center for Climate Modelling and Analysis second generation coupled general circulation model. The nonlinear patterns of North American Z500 and SAT anomalies associated with the AO in the model simulation are generally consistent with the observational results, thereby confirming the robustness of the nonlinear behavior of North American winter climate with respect to the AO in a climate simulation that is completely independent of the observations.  相似文献   

A coupled climate model simulation of the Last Glacial Maximum,Part 2: approach to equilibrium   总被引：3，自引：2，他引：3  

S.-J. Kim  G. Flato  G. Boer 《Climate Dynamics》2003,20(6):635-661

The climate of the last glacial maximum (LGM) is simulated with a coupled climate model. The simulated climate undergoes a rapid adjustment during the first several decades after imposition of LGM boundary conditions, as described in Part 1, and then evolves toward equilibrium over 900 model years. The climate simulated by the coupled model at this period is compared with observationally-based LGM reconstructions and with LGM results obtained with an atmosphere-mixed layer (slab) ocean version of the model in order to investigate the role of ocean dynamics in the LGM climate. Global mean surface air temperature and sea surface temperature (SST) decrease by about 10 °C and 5.6 °C in the coupled model which includes ocean dynamics, compared to decreases of 6.3 and 3.8 °C in slab ocean case. The coupled model simulates a cooling of about 6.5 °C over the tropics, which is larger than that of the CLIMAP reconstruction (1.7 °C) and larger than that of the slab ocean simulation (3.3 °C), but which is in reasonable agreement with some recent proxy estimates. The ocean dynamics of the coupled model captures features found in the CLIMAP reconstructions such as a relative maximum of ocean cooling over the tropical Pacific associated with a mean La Niña-like response and lead to a more realistic SST pattern than in the slab model case. The reduction in global mean precipitation simulated in the coupled model is larger (15%) than that simulated with the slab ocean model (~10%) in conjunction with the enhanced cooling. Some regions, such as the USA and the Mediterranean region, experience increased precipitation in accord with proxy paleoclimate evidence. The overall much drier climate over the ocean leads to higher sea surface salinity (SSS) in most ocean basins except for the North Atlantic where SSS is considerably lower due to an increase in the supply of fresh water from the Mississippi and Amazon rivers and presumably a decrease in salt transport by the weakened North Atlantic overturning circulation. The North Atlantic overturning stream function weakens to less than half of the control run value. The overturning is limited to a shallower depth (less than 1000 m) and its outflow is confined to the Northern Hemisphere. In the Southern Ocean, convection is much stronger than in the control run leading to a stronger overturning stream function associated with enhanced Antarctic Bottom Water formation. As a result, Southern Ocean water masses fill the entire deep ocean. The Antarctic Circumpolar Current (ACC) transport through the Drake Passage increases by about 25%. The ACC transport, despite weaker zonal winds, is enhanced due to changes in bottom pressure torque. The weakening of the overturning circulation in the North Atlantic and the accompanying 30% decrease in the poleward ocean heat transport contrasts with the strengthening of the overturning circulation in the Southern Ocean and a 40% increase in heat transport. As a result, sea ice coverage and thickness are affected in opposite senses in the two hemispheres. The LGM climate simulated by the coupled model is in reasonable agreement with paleoclimate proxy evidence. The dynamical response of the ocean in the coupled model plays an important role in determining the simulated, and undoubtedly, the actual, LGM climate.  相似文献