Parhelia in the planetary boundary layer at newmarket,Ontario: Note     

Y.S. Chung 《大气与海洋》2013,51(3):328-331

Abstract

Observations of parhelia at Newmarket, Ontario on December 10, 1977 support an earlier suggestion regarding observations made in Toronto on January 22 of the same year. Parhelia were found to occur in the planetary boundary layer (PBL), particularly during the morning hours under blowing snow conditions on clear, cold (ca —17°C) winter days. Thus parhelia which occur in southern Ontario during the winter months can develop in the PBL without the presence of cirrostratus‐type clouds.  相似文献   

A complementary depiction of the interannual variation of atmospheric circulation associated with ENSO events: Research note     

Tsing‐Chang Chen  Ming‐Cheng Yen  James Pfaendtner  Y.C. Sud 《大气与海洋》2013,51(2):417-433

Abstract

A simple diagnostic scheme, which combines a low‐pass temporal filter (with an 18‐month cutoff time) with a regular empirical orthogonal function (EOF) analysis, is used to delineate the synchronous evolution of El Nino‐Southern Oscillation‐related (ENSO‐related) modes in various variables of the ocean‐atmosphere system. Based on the causal relation chain of diabatic heating, divergent circulation and rotational flow, the diagnostic scheme extracts ENSO modes from the following data sources: the Pacific sea surface temperature (SST), the past 14‐years (1979–1992) of data generated by the Global Data Assimilation System of the National Meteorological Center, and a 10‐year (1979–1988) general circulation model climate simulation made at the Goddard Laboratory for Atmospheres. The analysis reveals the following: (a) the eigencoefficient time series of the first eigenmodes of selected filtered variables, which explain about 40–50% of their total variance, synchronize with the filtered SST averaged over Area NINO‐3; (b) the spatial structures of the first eigenmodes resemble the ensemble departures associated with ENSO events of these variables from their long term means; and (c) the results show that the proposed scheme can be easily applied to isolate and illustrate the time evolution of ENSO modes which exist in the long term observational database as well as in climate simulations.  相似文献   

Canadian middle atmosphere model: Preliminary results from the chemical transport module     

J. de Grandpré  J.W. Sandilands  J.C. McConnell  S.R. Beagley  P.C. Croteau  M.Y. Danilin 《大气与海洋》2013,51(4):385-431

Abstract

An important objective of middle atmosphere global climate modelling is the development of the capability of predicting the response of the middle atmosphere to natural or anthropogenic perturbations. To achieve this, a comprehensive chemistry package interactively coupled with radiative and dynamical modules is required. This paper presents preliminary results obtained with a photochemistry module which has been incorporated in the Canadian Middle Atmosphere Model (CMAM). The module contains 42 species including necessary oxygen, hydrogen, nitrogen, chlorine, bromine and methane oxidation cycle species. Photochemical balance equations are solved on‐line throughout the middle atmosphere at every dynamical time step. A full diurnal cycle is simulated with photolysis rates provided by a look‐up table. The chemistry solver is a mass conserving, fully implicit, backward difference scheme which currently uses less than 10% of the GCM run time. We present the results obtained from short integrations and compare them with UARS measurements. The model ozone distribution appears in quantitative agreement with observations showing peak values near 10 ppmv and confined to the 35‐km region. The abundance of nitrogen, chlorine, bromine oxides and their respective contributions to the overall ozone budget is realistic. The study illustrates the capability of the model to simulate middle atmosphere photochemistry for the disparate conditions occurring throughout the region.  相似文献   

Surface pulses in the lower St. Lawrence Estuary     

R.F. Marsden  Y. Gratton 《大气与海洋》2013,51(3):271-295

Abstract

Temperature, salinity, sea level and meteorological data from the ‘couplage entre les processus physiques et biogéochimiques’ (COUPPB) study of 1990 were examined to determine the forcing of fresh water pulses in the lower St. Lawrence Estuary. Anchor stations, during and after the passage of a pulse event, indicated that profound changes occurred in the hydrography at the head of the Laurentian Channel. A factor analysis of rotated eigenmodes of surface temperature and salinity indicated three co‐varying groups ‐ the first, on the north shore of the river, the second, on the south slope of the Laurentian Channel and the third in the middle of the estuary. A multivariate regression was used to relate salinity and temperature variations to forcing variates. It was found that sea level elevation and local winds accurately predicted fluctuations on the north shore. Salinity and temperature fluctuations on the south shore were best explained by propagation. In the middle of the estuary, salinity fluctuations were only weakly explained by propagation while temperature fluctuations could not be predicted by any of the forcing variates.  相似文献   

A verification framework for interannual-to-decadal predictions experiments   总被引：2，自引：1，他引：1  

L. Goddard  A. Kumar  A. Solomon  D. Smith  G. Boer  P. Gonzalez  V. Kharin  W. Merryfield  C. Deser  S. J. Mason  B. P. Kirtman  R. Msadek  R. Sutton  E. Hawkins  T. Fricker  G. Hegerl  C. A. T. Ferro  D. B. Stephenson  G. A. Meehl  T. Stockdale  R. Burgman  A. M. Greene  Y. Kushnir  M. Newman  J. Carton  I. Fukumori  T. Delworth 《Climate Dynamics》2013,40(1-2):245-272

Decadal predictions have a high profile in the climate science community and beyond, yet very little is known about their skill. Nor is there any agreed protocol for estimating their skill. This paper proposes a sound and coordinated framework for verification of decadal hindcast experiments. The framework is illustrated for decadal hindcasts tailored to meet the requirements and specifications of CMIP5 (Coupled Model Intercomparison Project phase 5). The chosen metrics address key questions about the information content in initialized decadal hindcasts. These questions are: (1) Do the initial conditions in the hindcasts lead to more accurate predictions of the climate, compared to un-initialized climate change projections? and (2) Is the prediction model’s ensemble spread an appropriate representation of forecast uncertainty on average? The first question is addressed through deterministic metrics that compare the initialized and uninitialized hindcasts. The second question is addressed through a probabilistic metric applied to the initialized hindcasts and comparing different ways to ascribe forecast uncertainty. Verification is advocated at smoothed regional scales that can illuminate broad areas of predictability, as well as at the grid scale, since many users of the decadal prediction experiments who feed the climate data into applications or decision models will use the data at grid scale, or downscale it to even higher resolution. An overall statement on skill of CMIP5 decadal hindcasts is not the aim of this paper. The results presented are only illustrative of the framework, which would enable such studies. However, broad conclusions that are beginning to emerge from the CMIP5 results include (1) Most predictability at the interannual-to-decadal scale, relative to climatological averages, comes from external forcing, particularly for temperature; (2) though moderate, additional skill is added by the initial conditions over what is imparted by external forcing alone; however, the impact of initialization may result in overall worse predictions in some regions than provided by uninitialized climate change projections; (3) limited hindcast records and the dearth of climate-quality observational data impede our ability to quantify expected skill as well as model biases; and (4) as is common to seasonal-to-interannual model predictions, the spread of the ensemble members is not necessarily a good representation of forecast uncertainty. The authors recommend that this framework be adopted to serve as a starting point to compare prediction quality across prediction systems. The framework can provide a baseline against which future improvements can be quantified. The framework also provides guidance on the use of these model predictions, which differ in fundamental ways from the climate change projections that much of the community has become familiar with, including adjustment of mean and conditional biases, and consideration of how to best approach forecast uncertainty.  相似文献   

Trends and low frequency variability of extra-tropical cyclone activity in the ensemble of twentieth century reanalysis   总被引：3，自引：2，他引：1  

Xiaolan L. Wang  Y. Feng  G. P. Compo  V. R. Swail  F. W. Zwiers  R. J. Allan  P. D. Sardeshmukh 《Climate Dynamics》2013,40(11-12):2775-2800

An objective cyclone tracking algorithm is applied to twentieth century reanalysis (20CR) 6-hourly mean sea level pressure fields for the period 1871–2010 to infer historical trends and variability in extra-tropical cyclone activity. The tracking algorithm is applied both to the ensemble-mean analyses and to each of the 56 ensemble members individually. The ensemble-mean analyses are found to be unsuitable for accurately determining cyclone statistics. However, pooled cyclone statistics obtained by averaging statistics from individual members generally agree well with statistics from the NCEP-NCAR reanalyses for 1951–2010, although 20CR shows somewhat weaker cyclone activity over land and stronger activity over oceans. Both reanalyses show similar cyclone trend patterns in the northern hemisphere (NH) over 1951–2010. Homogenized pooled cyclone statistics are analyzed for trends and variability. Conclusions account for identified inhomogeneities, which occurred before 1949 in the NH and between 1951 and 1985 in the southern hemisphere (SH). Cyclone activity is estimated to have increased slightly over the period 1871–2010 in the NH. More substantial increases are seen in the SH. Notable regional and seasonal variations in trends are evident, as is profound decadal or longer scale variability. For example, the NH increases occur mainly in the mid-latitude Pacific and high-latitude Atlantic regions. For the North Atlantic-European region and southeast Australia, the 20CR cyclone trends are in agreement with trends in geostrophic wind extremes derived from in-situ surface pressure observations. European trends are also consistent with trends in the mean duration of wet spells derived from rain gauge data in Europe.  相似文献   

Evaluation and response of winter cold spells over Western Europe in CMIP5 models     

Y. Peings  J. Cattiaux  H. Douville 《Climate Dynamics》2013,41(11-12):3025-3037

This paper is dedicated to the analysis of winter cold spells over Western Europe in the simulations of the 5th phase of the Coupled Model Intercomparison Project (CMIP5). Both model biases and responses in a warming climate are discussed using historical simulations and the 8.5 W/m² Representative Concentration Pathway (RCP8.5) scenario, respectively on the 1979–2008 and 2070–2099 periods. A percentile-based index (10th percentile of daily minimum temperature, Q10) with duration and spatial extent criteria is used to define cold spells. Related diagnostics (intensity, duration, extent, and severity as a combination of the former three statistics) of 13 models are compared to observations and suggest that models biases on severity are mainly due to the intensity parameter rather than to duration and extent. Some hypotheses are proposed to explain these biases, that involve large-scale dynamics and/or radiative fluxes related to clouds. Evolution of cold spells characteristics by the end of the century is then discussed by comparing RCP8.5 and historical simulations. In line with the projected rise of mean temperature, “present-climate” cold spells (computed with the 1979–2008 10th percentile, Q10P) are projected to be much less frequent and, except in one model, less severe. When cold spells are defined from the future 10th percentile threshold (“future-climate” cold spells, Q10F), all models simulate a decrease of their intensity linearly related to the seasonal mean warming. Some insights are given to explain the inter-model diversity in the magnitude of the cold spells response. In particular, the snow-albedo feedback is suggested to play an important role, while for some models changes in large-scale dynamics are also not negligible.  相似文献   

A note on climate change adaptation for seaports: a challenge for global ports, a challenge for global society     

Austin H. Becker  Michele Acciaro  Regina Asariotis  Edgard Cabrera  Laurent Cretegny  Philippe Crist  Miguel Esteban  Andrew Mather  Steve Messner  Susumu Naruse  Adolf K. Y. Ng  Stefan Rahmstorf  Michael Savonis  Dong-Wook Song  Vladimir Stenek  Adonis F. Velegrakis 《Climatic change》2013,120(4):683-695

With 80 % of world trade carried by sea, seaports provide crucial linkages in global supply-chains and are essential for the ability of all countries to access global markets. Seaports are likely to be affected directly and indirectly by climatic changes, with broader implications for international trade and development. Due to their coastal location, seaports are particularly vulnerable to extreme weather events associated with increasing sea levels and tropical storm activity, as illustrated by hurricane “Sandy”. In view of their strategic role as part of the globalized trading system, adapting ports in different parts of the world to the impacts of climate change is of considerable importance. Reflecting the views of a diverse group of stakeholders with expertise in climate science, engineering, economics, policy, and port management, this essay highlights the climate change challenge for ports and suggests a way forward through the adoption of some initial measures. These include both “soft” and “hard” adaptations that may be spearheaded by individual port entities, but will require collaboration and support from a broad range of public and private sector stakeholders and from society at large. In particular, the essay highlights a need to shift to more holistic planning, investment and operation.  相似文献   

Do people “personally experience” global warming,and if so how,and does it matter?   总被引：1，自引：0，他引：1  

Karen Akerlof  Edward W. Maibach  Dennis Fitzgerald  Andrew Y. Cedeno  Amanda Neuman 《Global Environmental Change》2013,23(1):81-91

For most people, the direct and personally observable signals of climate change should be difficult to detect amid the variability of everyday weather. Yet, previous research has shown that some people believe they have personally experienced global warming. Through four related studies, our paper sheds light on what signals of global warming some people believe they are detecting, why, and whether or not it matters. These studies were conducted using population survey and climatic data from a single county in Michigan. Study 1 found that 27% of the county's adult residents felt that they had personally experienced global warming. Study 2 – based on content analysis of people's open-ended responses – found that the most frequently described personal experiences of global warming were changes in seasons (36%), weather (25%), lake levels (24%), animals and plants (20%), and snowfall (19%). Study 3 – based on NOAA climatic data – found that most, but not all, of these detected signals are borne out in the climatic record. Study 4 – using the survey data – found that personal experience of global warming matters in that it predicts perceptions of local risk of global warming, controlling for demographics, political affiliation, and cultural beliefs about national policy outcomes. We conclude that perceived personal experience of global warming appears to heighten people's perception of the risks, likely through some combination of direct experience, vicarious experience (e.g., news media stories), and social construction.  相似文献   

Effects of economic recession and local weather on climate change attitudes     

Robert Y. Shum 《Climate Policy》2013,13(1):38-49

How are large companies responding to the challenges of reducing their greenhouse gas (GHG) emissions? An analysis of the published climate change policies and performance of 125 large European companies is presented. The results suggest that most large European companies have now developed the management systems and processes necessary for them to effectively manage their GHG emissions and related business risks. However, there is a significant disconnect between the targets that companies set for themselves and the more ambitious targets being set by the European Union (which has committed to a 20% reduction in its emissions by 2020 against a 1990 baseline). Of the companies surveyed, just over one-third had stabilized or reduced their total GHG emissions over the period 2002–2007, and fewer than one-third expected their emissions to stabilize or reduce in the coming years. The relationship between the quality of corporate policies and performance outcomes (in terms of GHG emissions) suggests that while companies with stronger policies are likely to have relatively better performance, only a minority of those companies with the highest-quality policies are committing to absolute reductions in their GHG emissions.  相似文献