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Wanli Wu, Amanda H. Lynch, Sheldon Drobot, James Maslanik, A. David McGuire, and Ute Herzfeld

study by Drobot et al. ( Drobot et al. 2006 ) conducted a comprehensive intercomparison for precipitation and surface air temperature (SAT) among a number of data sources including the RCM simulation presented in this paper. Thus, the validation and intercomparison in this paper will focus on spatial patterns of mean states, variations, and corresponding seasonality. We also examine trends in the regional climate, with an emphasis on trends in the seasonality of surface climate. This paper is

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Patrick Minnis, J. Kirk Ayers, Rabindra Palikonda, and Dung Phan

and D. Fahey for their comments, K. Gierens for providing the contrail distributions, C. Hahn for assistance with the cirrus data, D. Doelling for assistance in analyzing the radiosonde data, and D. Minnis for continued encouragement. This research was supported by the NASA Office of Earth Science Pathfinder Program under NRA-99-OES-04. REFERENCES Angell , J. K. , 1999 : Variation with height and latitude of radiosonde temperature trends in North America, 1975–94. J. Climate , 12 , 2551

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Zuohao Cao and Jianmin Ma

of a trend for summer severe-rainfall frequency over Ontario and examine how large-scale climate conditions are linked with the observed variability in summer severe-rainfall frequency over Ontario. The data and methods used in this study are briefly described in sections 2 and 3 . The results obtained from trend and variability analyses for summer severe-rainfall frequency over Ontario are presented in section 4 . The discussion and conclusions are given in sections 5 and 6 , respectively

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United States, and it is consideredpossible that the expected accompanying temperaturechange may also be at hand, in view of the trends shownfor Montana. The evidence certainly shows that Mon-tana has tended toward wetter and colder climate now forseveral years, but the persistence of such a trend remainsimpossible to predict in spite of the fact that it appearsestablished. Moreover, in climatic trends of many yearswhich are available for study, an occasional year has beenencountered which was an

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Christian Seiler, Ronald W. A. Hutjes, and Pavel Kabat

South America’s subtropical east coast ( Garreaud et al. 2009 ). Along climate variability, long-term climate trends have been detected in South America. In the tropical Andes, mean surface air temperatures have increased from 1950 to 1994 by 0.15°C per decade ( Vuille et al. 2003 ). The same study found no clear pattern on trends in annually accumulated rainfall. Espinoza Villar et al. (2009) found a negative trend in rainfall in the Amazon basin (756 stations) with an annual rate of −0

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Robert E. Livezey, Konstantin Y. Vinnikov, Marina M. Timofeyeva, Richard Tinker, and Huug M. van den Dool

space scales relevant to the myriad applications for which they are needed. The reason for this is threefold: The contemporary climate is changing at a pace rapid enough to already have important impacts. Climate statistics, including normals, are nonstationary. In the case of U.S. climate divisions, there are many instances in which linear trend estimates (discussed later) yield changes in seasonal temperature and precipitation normals over the last 30 yr that are between 1 and 3 standard

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Melissa S. Bukovsky

1. Introduction Regional climate models (RCMs) should be able to capture large-scale temperature trends when forcing for these trends is included in the driving boundary conditions. This is logical, but it is only recently that the RCM community has tested its models’ performances in this way, and examples are still not prevalent in the literature. Testing for skill in reproducing trends is a relatively recent phenomenon (e.g., Giorgi et al. 2004 ), while testing for general skill in regional

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Hussein Wazneh, M. Altaf Arain, and Paulin Coulibaly

well. Adamowski et al. (2010) analyzed annual short-duration extreme rainfall for 15 stations in the Canadian province of Ontario and found increasing trends but with a nonuniform rate of change for all short durations. Razavi et al. (2016) studied past and future trends in temperature and precipitation across the Hamilton region of Ontario using a range of downscaled climate models. They showed an increasing trend for the mean and maximum temperature and annual total precipitation over various

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Colin Gallagher, Robert Lund, and Michael Robbins

typical of climate time series in that they have a time trend and multiple mean-shift changepoints that act to influence overall trend inferences. The four changepoints here are viewed as artificial as they are induced by changes in data collection (gauge and location changes). Methods that adjust data for artificial shifts of this type are called homogenization techniques. The homogenization changepoint problem is well known in the climate literature; numerous authors have presented changepoint tests

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Donald B. Percival and D. Andrew Rothrock

1. Introduction There is currently a strong scientific and societal interest in the issue of climate change. It is not uncommon that one examines a simple time series of a scalar climatic variable and asks whether it contains a trend that might indicate if by how much and in what direction climate has changed. We offer here some thoughts about the pitfalls in estimating trends and their significance from selected portions of a time series. Our example is one familiar in our own field of

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