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1

Comparison between linear and nonlinear trends in NOAA-15 AMSU-A brightness temperatures during 1998-2010  

NASA Astrophysics Data System (ADS)

Brightness temperature observations from Microwave Sounding Unit and Advanced Microwave Sounding Unit-A (AMSU-A) on board National Oceanic and Atmospheric Administration (NOAA) satellites have been widely utilized for estimating the global climate trend in the troposphere and stratosphere. A common approach for deriving the trend is linear regression, which implicitly assumes the trend being a straight line over the whole length of a time series and is often highly sensitive to the data record length. This study explores a new adaptive and temporally local data analysis method—Ensemble Empirical Mode Decomposition (EEMD)—for estimating the global trends. In EEMD, a non-stationary time series is decomposed adaptively and locally into a sequence of amplitude-frequency modulated oscillatory components and a time-varying trend. The AMSU-A data from the NOAA-15 satellite over the time period from October 26, 1998 to August 7, 2010 are employed for this study. Using data over Amazon rainforest areas, it is shown that channel 3 is least sensitive to the orbital drift among four AMSU-A surface sensitive channels. The decadal trends of AMSU-A channel 3 and other eight channels in the troposphere and stratosphere are deduced and compared using both methods. It is shown that the decadal climate trends of most AMSU-A channels are nonlinear except for channels 3-4 in Northern Hemisphere only and channels 12-13. Although the decadal trend variation of the global average brightness temperature is no more than 0.2 K, the regional decadal trend variation could be more (less) than 3 K (-3 K) in high latitudes and over high terrains.

Qin, Z.; Zou, X.; Weng, F.

2012-10-01

2

Linear trend analysis: a comparison of methods  

Microsoft Academic Search

In this paper, we present an overview of statistical approaches available for detecting and estimating linear trends in environmental data. We evaluate seven methods of trend detection and make recommendations based on a simulation study. We also illustrate the methods using real data.

Ann Hess; Hari Iyer; William Malm

2001-01-01

3

Review of mesospheric temperature trends  

Microsoft Academic Search

In recent times it has become increasingly clear that releases of trace gases from human activity have a potential for causing change in the upper atmosphere. However, our knowledge of systematic changes and trends in the temperature of the mesosphere and lower thermosphere is relatively limited compared to the Earth's lower atmosphere, and not much effort has been made to

G. Beig; P. Keckhut; R. P. Lowe; R. G. Roble; M. G. Mlynczak; J. Scheer; V. I. Fomichev; D. Offermann; W. J. R. French; M. G. Shepherd; A. I. Semenov; E. E. Remsberg; C. Y. She; F. J. Lübken; J. Bremer; B. R. Clemesha; J. Stegman; F. Sigernes; S. Fadnavis

2003-01-01

4

Global Warming Trend of Mean Tropospheric Temperature Observed by Satellites  

Microsoft Academic Search

We have analyzed the global tropospheric temperature for 1978 to 2002 with the use of passive microwave sounding data from the NOAA series of polar orbiters and the Earth Observing System Aqua satellite. To accurately retrieve the climatic trend, we combined the satellite data with an analytic model of temperature that contains three different time scales: a linear trend and

Konstantin Y. Vinnikov; Norman C. Grody

2003-01-01

5

Estimating population trends with a linear model  

USGS Publications Warehouse

We describe a simple and robust method for estimating trends in population size. The method may be used with Breeding Bird Survey data, aerial surveys, point counts, or any other program of repeated surveys at permanent locations. Surveys need not be made at each location during each survey period. The method differs from most existing methods in being design based, rather than model based. The only assumptions are that the nominal sampling plan is followed and that sample size is large enough for use of the t-distribution. Simulations based on two bird data sets from natural populations showed that the point estimate produced by the linear model was essentially unbiased even when counts varied substantially and 25% of the complete data set was missing. The estimating-equation approach, often used to analyze Breeding Bird Survey data, performed similarly on one data set but had substantial bias on the second data set, in which counts were highly variable. The advantages of the linear model are its simplicity, flexibility, and that it is self-weighting. A user-friendly computer program to carry out the calculations is available from the senior author.

Bart, J.; Collins, B.; Morrison, R. I. G.

2003-01-01

6

Model space visualization for multivariate linear trend discovery  

Microsoft Academic Search

Discovering and extracting linear trends and correlations in datasets is very important for analysts to understand multivariate phenom- ena. However, current widely used multivariate visualization tech- niques, such as parallel coordinates and scatterplot matrices, fail to reveal and illustrate such linear relationships intuitively, especially when more than 3 variables are involved or multiple trends coex- ist in the dataset. We

Zhenyu Guo; Matthew O. Ward; Elke A. Rundensteiner

2009-01-01

7

Global warming trend of mean tropospheric temperature observed by satellites.  

PubMed

We have analyzed the global tropospheric temperature for 1978 to 2002 with the use of passive microwave sounding data from the NOAA series of polar orbiters and the Earth Observing System Aqua satellite. To accurately retrieve the climatic trend, we combined the satellite data with an analytic model of temperature that contains three different time scales: a linear trend and functions that define the seasonal and diurnal cycles. Our analysis shows a trend of +0.22 degrees to 0.26 degrees C per 10 years, consistent with the global warming trend derived from surface meteorological stations. PMID:12970572

Vinnikov, Konstantin Y; Grody, Norman C

2003-09-11

8

Trend analysis of temperature parameters in Iran  

NASA Astrophysics Data System (ADS)

In this study, long-term annual and monthly trends in mean maximum, mean minimum and mean temperature are investigated at 35 synoptic stations in Iran. The statistical significance of trends is assessed by the Mann-Kendall test. Most stations, especially those in western and eastern parts of country, had significant positive trends in monthly temperature time series in summer season. However, the maximum number of stations with the positive trend were observed in April (30 stations), and then in August (29 stations) while the negative trends were seen in February (16 stations) and March (15 stations). On annual scale, most stations in western and southern parts of Iran had significant positive trend. Overall, about 71%, 66% and about 40% of stations had statistically significant trends in mean annual temperature, mean annual minimum temperature and in mean annual maximum temperature, respectively. These results, however, indicate that the climate in Iran is growing warmer, especially in summer.

Saboohi, R.; Soltani, S.; Khodagholi, M.

2012-08-01

9

Temperature and precipitation of Alaska: 50 year trend analysis  

Microsoft Academic Search

Summary  ?Temperature and precipitation records from 1949 to 1998 were examined for 25 stations throughout the State of Alaska. Mean,\\u000a maxima, and minima temperatures, diurnal temperature range, and total precipitation were analyzed for linear trends using\\u000a least squares regressions. Annual and seasonal mean temperature increases were found throughout the entire state, and the\\u000a majority were found to be statistically significant at

J. M. Stafford; G. Wendler; J. Curtis

2000-01-01

10

Dynamic contribution to hemispheric mean temperature trends  

SciTech Connect

On the basis of land station data from the Northern Hemisphere, it was determined that roughly half of the temporal variance of monthly mean hemispheric mean anomalies in surface air temperature during the period from 1900 through 1990 were linearly related to the amplitude of a distinctive spatial pattern in which the oceans are anomalously cold and the continents are anomalously warm poleward of 40 degrees north when the hemisphere is warm. Apart from an upward trend since 1975, to which El Nino has contributed, the amplitude time series associated with this pattern resembles seasonally dependent white noise. it is argued that the variability associated with this pattern is dynamically induced and is not necessarily an integral part of the fingerprint of global warming. 12 refs., 5 figs., 1 tab.

Wallace, J.M.; Zhang, Y.; Renwick, J.A. [Univ. of Washington, Seattle, WA (United States)

1995-11-03

11

Linear trends of temperature at intermediate and deep layers of the North Atlantic and the North Pacific Oceans: 1957-1981  

SciTech Connect

Using all available hydrographic station data on ocean temperature observations from World Data Center-B (Obninsk, Russia), investigation of temperature changes in the North Atlantic and North Pacific oceans within the depth range of 300 to 3,000 m has been carried out for the period 1957--1981. Results of statistical data analysis show that in the upper layer to about 500-m depths of both oceans, on average, seawater temperature declined. Deeper than 500--600 m in the North Pacific Ocean, no significant temperature changes have been revealed for this 25-year time interval. On average, for the North Atlantic Ocean, a statistically significant temperature rise (about 0.1[degrees]C 25 yr[sup [minus]1]) is observed in the 800- to 2,500-m layer. 28 refs., 20 figs., 2 tab.

Antonov, J.I. (State Hydrological Institute, St. Petersburg (Russian Federation))

1993-10-01

12

Stratospheric temperature trends: Observations and model simulations  

Microsoft Academic Search

Trends and variations in global stratospheric temperatures are an integral part of the changes occurring in the Earth's climate system. Data sets for analyzing long-term (a decade and more) changes in the stratospheric temperatures consist of radiosonde, satellite, lidar, and rocketsonde measurements; meteorological analyses based on radiosonde and\\/or satellite data; and products based on assimilating observations using a general circulation

V. Ramaswamy; M.-L. Chanin; J. Angell; J. Barnett; D. Gaffen; M. Gelman; P. Keckhut; Y. Koshelkov; K. Labitzke; J.-J. R. Lin; A. O'Neill; J. Nash; W. Randel; R. Rood; K. Shine; M. Shiotani; R. Swinbank

2001-01-01

13

Simulation of recent global temperature trends.  

PubMed

Observations show that global average tropospheric temperatures have been rising during the past century, with the most recent portion of record showing a sharp rise since the mid-1970s. This study shows that the most recent portion of the global temperature record (1970 to 1992) can be closely reproduced by atmospheric models forced only with observed ocean surface temperatures. In agreement with a diverse suite of controversial observational evidence from the past 40 years, the upward trend in simulated tropospheric temperatures is caused by an enhancement of the tropical hydrologic cycle driven by increasing tropical ocean temperatures. Although it is possible that the observed behavior is due to natural climate variability, there is disquieting similarity between these model results, observed climate trends in recent decades, and the early expressions of the climatic response to increased atmospheric carbon dioxide in numerical simulations. PMID:17745844

Graham, N E

1995-02-01

14

Spring phenology trends in Alberta, Canada: links to ocean temperature  

NASA Astrophysics Data System (ADS)

Warmer winter and spring temperatures have been noted over the last century in Western Canada. Earlier spring plant development in recent decades has been reported for Europe, but not for North America. The first-bloom dates for Edmonton, Alberta, were extracted from four historical data sets, and a spring flowering index showed progressively earlier development. For Populus tremuloides, a linear trend shows a 26-day shift to earlier blooming over the last century. The spring flowering index correlates with the incidence of El Niño events and with Pacific sea-surface temperatures.

Beaubien, E. G.; Freeland, H. J.

15

Spring phenology trends in Alberta, Canada: links to ocean temperature.  

PubMed

Warmer winter and spring temperatures have been noted over the last century in Western Canada. Earlier spring plant development in recent decades has been reported for Europe, but not for North America. The first-bloom dates for Edmonton, Alberta, were extracted from four historical data sets, and a spring flowering index showed progressively earlier development. For Populus tremuloides, a linear trend shows a 26-day shift to earlier blooming over the last century. The spring flowering index correlates with the incidence of El Niño events and with Pacific sea-surface temperatures. PMID:10993558

Beaubien, E G; Freeland, H J

2000-08-01

16

Long-term trend analysis for temperature in the Jinsha River Basin in China  

NASA Astrophysics Data System (ADS)

On the basis of the mean annual and seasonal temperatures from 30 meteorological stations in the Jinsha River Basin (JRB) from 1961 to 2008, the temperature trends are analyzed by using Mann-Kendall test and linear trend analysis. There is an increasing trend in mean annual and seasonal temperatures during this period, and the increasing trends in winter seem more significant than those in the other three seasons. The mean annual temperature has increased by 0.0158°C/year during the last 48 years. There are more than 70% of stations exhibiting increasing trends for annual and seasonal temperatures. The increasing trends in the headwater and upper reaches are more dominant than those in the middle and lower reaches. The largest increase magnitude occurred in the low temperature area, while the largest decrease magnitude occurred in the high temperature area. The decreasing trends are mainly characterized for the maximum temperature time series, and summer is the only season showing a slight and insignificant increasing trend. All the time series showed a statistically significant increasing trend at the level of ? = 0.05 for the minimum temperature time series. As a whole, the increasing magnitude of the minimum temperature is significantly greater than the decreasing magnitude of the maximum temperature.

Wang, Shunjiu; Zhang, Xinli

2012-08-01

17

Influence of the Atlantic Ocean on the magnitude of air temperature trends under current warming  

Microsoft Academic Search

An analysis is made of the magnitudes of the linear trends of daily mean temperature in the city of Minsk for the period from 1966 to 2008. It is found that the largest magnitudes of trends in the annual variation correspond to mid-January as well as to the end of July–August, whereas in May and in November they are poorly

V. F. Loginov

2010-01-01

18

Global trends of measured surface air temperature  

NASA Astrophysics Data System (ADS)

We analyze surface air temperature data from available meteorological stations with principal focus on the period 1880-1985. The temperature changes at mid- and high latitude stations separated by less than 1000 km are shown to be highly correlated; at low latitudes the correlation falls off more rapidly with distance for nearby stations. We combine the station data in a way which is designed to provide accurate long-term variations. Error estimates are based in part on studies of how accurately the actual station distributions are able to reproduce temperature change in a global data set produced by a three-dimensional general circulation model with realistic variability. We find that meaningful global temperature change can be obtained for the past century, despite the fact that the meteorological stations are confined mainly to continental and island locations. The results indicate a global warming of about 0.5°-0.7°C in the past century, with warming of similar magnitude in both hemispheres; the northern hemisphere result is similar to that found by several other investigators. A strong warming trend between 1965 and 1980 raised the global mean temperature in 1980 and 1981 to the highest level in the period of instrumental records. The warm period in recent years differs qualitatively from the earlier warm period centered about 1940; the earlier warming was focused at high northern latitudes, while the recent warming is more global. We present selected graphs and maps of the temperature change in each of the eight latitude zones. A computer tape of the derived regional and global temperature changes is available from the authors.

Hansen, James; Lebedeff, Sergej

1987-11-01

19

A comparison of model-simulated trends in stratospheric temperatures  

Microsoft Academic Search

Estimates of annual-mean stratospheric temperature trends over the past twenty years, from a wide variety of models, are compared both with each other and with the observed cooling seen in trend analyses using radiosonde and satellite observations. The modelled temperature trends are driven by changes in ozone (either imposed from observations or calculated by the model), carbon dioxide and other

K. P. Shine; M. S. Bourqui; P. M. De F. Forster; S. H. E. Hare; U. Langematz; P. Braesicke; V. Grewe; M. Ponater; C. Schnadt; C. A. Smiths; J. D. Haighs; J. Austin; N. Butchart; D. T. Shindell; W. J. Randel; T. Nagashima; R. W. Portmann; S. Solomon; D. J. Seidel; J. Lanzante; S. Klein; V. Ramaswamy; M. D. Schwarzkopf

2003-01-01

20

Trends of daily extreme temperatures in the Iberian Peninsula  

NASA Astrophysics Data System (ADS)

Climatic extreme events may be changing their time patterns and intensity as consequence of the anthropogenic climate change. The development of policies to mitigate and adapt to the threat of climate change requires the accurate assessment of the potential impacts of climate change on societies and ecosystems at regional and local-scale and with fine time resolution. The EXPICA project (Spanish grant CGL2007-66546-C03/CLI) is focused on studying extreme events over the Iberian Peninsula. Under this umbrella, in this work a first approach of trends of extreme temperatures in a selected set of stations in the Iberian Peninsula since the 19th century is presented. These stations are located in the main climatic domains of the Iberian Peninsula, that is, northern cost, central and western area, and Mediterranean coast. Daily database SDATS was used in this study. For each month and location, percentiles 10 and 90 of daily maximum temperature (TX) and minimum temperature (TN), corresponding to the reference period 1971-2000, were chosen as threshold values to define extreme temperatures. Frequency of days with TX>TX90, TXTN90 was estimated for each month and station. Trends in these frequencies were calculated using the Mann-Kendall test and linear regression. Results corresponding to January and July are presented, and their relationships with dynamical conditions are discussed. Future challenges and developments are outlined.

Fernández-Montes, S.; Rodrigo, F. S.; Aguilar, E.; García-Borrés, I.; Rasilla, D.; Luna, Y.; Sigró, J.; Brunet, M.

2009-04-01

21

Estimating population trends with a linear model: technical comments  

USGS Publications Warehouse

Controversy has sometimes arisen over whether there is a need to accommodate the limitations of survey design in estimating population change from the count data collected in bird surveys. Analyses of surveys such as the North American Breeding Bird Survey (BBS) can be quite complex; it is natural to ask if the complexity is necessary, or whether the statisticians have run amok. Bart et al. (2003) propose a very simple analysis involving nothing more complicated than simple linear regression, and contrast their approach with model-based procedures. We review the assumptions implicit to their proposed method, and document that these assumptions are unlikely to be valid for surveys such as the BBS. One fundamental limitation of a purely design-based approach is the absence of controls for factors that influence detection of birds at survey sites. We show that failure to model observer effects in survey data leads to substantial bias in estimation of population trends from BBS data for the 20 species that Bart et al. (2003) used as the basis of their simulations. Finally, we note that the simulations presented in Bart et al. (2003) do not provide a useful evaluation of their proposed method, nor do they provide a valid comparison to the estimating- equations alternative they consider.

Sauer, J.R.; Link, W.A.; Royle, J.A.

2004-01-01

22

Simulation of mesospheric temperature trends at mid latitudes in summer  

NASA Astrophysics Data System (ADS)

The LIMA Leibniz-Institute Middle Atmosphere Model is used to study mesospheric temperature trends during the last 5 decades from 1961 until 2010. In order to account for realistic atmospheric conditions LIMA adapts several observational data sets, such as tropospheric and stratospheric temperatures and winds from ECMWF at heights 0-35 km, daily Lyman-alpha fluxes, and monthly carbon dioxide concentrations since 1961, and the monthly ozone profiles up to 0.6 hPa provided from SBUV/TOMS satellite instruments since 1979. This paper presents a comparison of simulated temperature trends with groundbased observations of temperature (lidar) and phase height trends (radiowave technique) at mid-latitudes (45-50N) and temperature trends derived from satellite data (SSU). Generally good agreement is found between model trends and trends derived from observations without any significant differences. As a major result the greenhouse warming in the lower troposphere reverses to a cooling trend in the mesosphere where the magnitude of the trend of 2-4 K/decade is about a factor of 10 larger than compared to trends in global mean surface temperature which are about 0.2 K/decade. The size of mesospheric temperature trend is not constant during the last 5 decades. Especially, the period from 1979 - 1997 shows a large mesospheric cooling trend of 4-5 K/decade which is mainly affected by an upper stratospheric ozone decrease over the same period.

Berger, U.; Luebken, F.

2011-12-01

23

Recent trends in temperature and precipitation over South Korea  

Microsoft Academic Search

Temperature and precipitation changes over South Korea have been studied since 1954, both in terms of means and extreme events, using observational station data. Recurrence intervals are defined to examine trends in extreme events at each station. Generally, it is possible to describe trends in temperature and precipitation over South Korea as follows. The annual mean temperature shows an upward

Hyun-Sook Jung; Youngeun Choi; Jai-Ho Oh; Gyu-Ho Lim

2002-01-01

24

Surface air temperature trends in Southern Brazil for 1960 2002  

Microsoft Academic Search

Trends in minimum and maximum air temperature and in the diurnal thermal range (DTR), and derived indices of extreme temperatures since the 1960's are assessed for southern Brazil. Most meteorological stations show steep increases in the night-time temperatures (depicted by the minimum temperature) as compared to slight increases in the daytime temperature (depicted by the maximum temperature), both year round

Jose A. Marengo; Claudia C. Camargo

2008-01-01

25

Watershed-wide trend analysis of temperature characteristics in Karun-Dez watershed, southwestern Iran  

NASA Astrophysics Data System (ADS)

Trend estimation of climatic characteristics for a watershed is required to determine developing compatible strategies related to design, development, and management of water resources. In this study, the trends of the annual maximum ( T max), minimum ( T min), and mean ( T mean) air temperature; temperature anomaly ( T anomaly); and diurnal temperature range (DTR) time series at 13 meteorological stations located in the Karun-Dez watershed were analyzed using the Mann-Kendall and linear regression trend tests. The pre-whitening method was used to eliminate the influence of serial correlation on the Mann-Kendall test. The result showed increasing trends in the T min, T mean, and T anomaly series at the majority of stations and decreasing trend in the T max and DTR series. A geographical analysis of the trends revealed a broad warming trend in most of the watershed, and the cooling trends were observed only in the southern parts. Furthermore, the geographical pattern of the trends in the T mean and T anomaly series was similar, and the T max data did not show any dominant trend for the whole watershed. This study provides temperature change scenarios that may be used for the design of future water resource projects in the watershed.

Marofi, Safar; Soleymani, Samere; Salarijazi, Meysam; Marofi, Hossein

2012-10-01

26

Temperature trends at the surface and in the troposphere  

Microsoft Academic Search

This paper incorporates the latest improvements in intersatellite calibration, along with a new statistical technique, to determine the diurnal and seasonal cycles and climatic trends of 1978–2004 tropospheric temperature using Microwave Sounding Unit measurements. We also compare the latitudinal distribution of temperature trends from the surface and troposphere with each other and with model simulations for the past 26 years.

Konstantin Y. Vinnikov; Norman C. Grody; Alan Robock; Ronald J. Stouffer; Philip D. Jones; Mitchell D. Goldberg

2006-01-01

27

Reevaluation of trends and changes in mean, maximum and minimum temperatures of Turkey for the period 1929-1999  

Microsoft Academic Search

Mean, maximum and minimum surface air temperatures recorded at 70 climatological stations in Turkey during the period from 1929 to 1999 were analysed to reveal spatial and temporal patterns of long-term trends, change points, significant warming (cooling) periods and linear trend rates per decade. Annual, winter and spring mean temperatures have tended to increase, particularly over the southern regions of

Murat Türke; Utku M. Sümer; Smal Demr

2002-01-01

28

Mesospheric temperature trends at mid-latitudes in summer  

NASA Astrophysics Data System (ADS)

The Leibniz-Institute Middle Atmosphere Model LIMA is used to study mesospheric temperature trends in summer during the last 5 decades (1961-2009). In order to account for realistic atmospheric conditions LIMA adapts several observational data sets, namely a) tropospheric and stratospheric temperatures and winds from ECMWF at heights 0-35 km, b) daily Lyman-? fluxes, c) monthly carbon dioxide concentrations since 1961, and d) annual total ozone from ground-based data for 1964-1978 and monthly ozone profiles up to 0.60 hPa from satellites since 1979. This paper presents a comparison of simulated temperature trends with a) ground-based observations of lidar temperatures at 44°N, b) phase height measurements at mid-latitudes (51°N), and c) temperature trends derived from satellite data. In general there is excellent agreement between trends from LIMA and observations. Cooling in the mesosphere is on the order of 2-4 K/decade. The magnitude of the mesospheric temperature trend varies during the last five decades. In particular, the period from 1979-1997 shows large mesospheric cooling of 3-5 K/decade. This large cooling is primarily caused by long-term changes of ozone in the upper stratosphere in combination with a CO2 increase. For the first time, modeling of mesospheric temperature trends confirm the extraordinarily large trends from observations.

Berger, U.; Lübken, F.-J.

2011-11-01

29

Nonlinear Trends, Long-Range Dependence and Climate Noise Properties of Surface Temperature  

NASA Astrophysics Data System (ADS)

My presentation will focus on the significance of trends of four exemplary temperature time series - Central England Temperature (CET), Stockholm (Sweden), Faraday-Vernadsky (Antarctica) and Alert (Canada). First the robustness and accuracy of various trend detection methods will be discussed: ordinary least squares, robust and generalized linear model regression, Ensemble Empirical Mode Decomposition (EEMD) and wavelets. Tests are carried out with surrogate data with nonlinear trends, superposed autocorrelated and non-Gaussian fluctuations. An analysis of the four temperature time series reveals evidence of long-range dependence (LRD) and nonlinear warming trends. The significance of these trends are tested against climate noise representing the background climate variability. Three different methods are used to generate climate noise: (i) a short-range dependent model AR(1), (ii) a LRD model and (iii) phase scrambling. I will discuss the ability of the trend detection methods to distinguish the observed warming trend from stochastic trends and the implications for general trend identification in the geosciences.

Franzke, C.

2012-04-01

30

Temperature and ice layer trends in the summer middle atmosphere  

NASA Astrophysics Data System (ADS)

We present results from our LIMA model (Leibniz Institute Middle Atmosphere Model) which nicely reproduces mean conditions of the summer mesopause region and also mean characteristics of ice layers known as noctilucent clouds. LIMA nudges to ECMWF data in the troposphere and lower stratosphere which influences the background conditions in the mesosphere. We study temperature trends in the mesosphere at middle and polar latitudes and compared with temperature trends from satellites, lidar, and phase height observations. For the first time large observed temperature trends in the summer mesosphere can be reproduced and explained by a model. As will be shown, stratospheric ozone has a major impact on temperature trends in the summer mesosphere. The temperature trend is not uniform in time: it is moderate from 1961 (the beginning of our record) until the beginning of the 1980s. Thereafter, temperatures decrease much stronger until the mid 1990s. Thereafter, temperatures are nearly constant or even increase with time. As will be shown, trends in ozone and carbon dioxide explain most of this behavior. Ice layers in the summer mesosphere are very sensitive to background conditions and are therefore considered to be appropriate tracers for long term variations in the middle atmosphere. We use LIMA background conditions to determine ice layer characteristics in the mesopause region. We compare our results with measurements, for example with albedos from the SBUV satellites, and show that we can nicely reproduce observed trends. It turns out that temperature trends are positive (negative) in the upper (lower) part of the ice layer regime. This complicates an interpretation of NLC long term variations in terms of temperature trends.

Lübken, F.-J.; Berger, U.

2012-04-01

31

ABUNDANCES OF STARS WITH PLANETS: TRENDS WITH CONDENSATION TEMPERATURE ,  

SciTech Connect

Precise abundances of 18 elements have been derived for 10 stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically {approx}< 0.05 dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (T{sub c}) of the elements in the sense of increasing abundances with increasing T{sub c}; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with T{sub c}, although slopes of linear least-square fits to the [m/H]-T{sub c} relations for all but two stars are smaller here than in previous studies. When considering the refractory elements (T{sub c} >900 K) only, which may be more sensitive to planet formation processes, the sample can be separated into a group with positive slopes (four stars) and a group with flat or negative slopes (six stars). The four stars with positive slopes have very close-in giant planets (three at 0.05 AU) and slopes that fall above the general Galactic chemical evolution trend. We suggest that these stars have accreted refractory-rich planet material but not to the extent that would increase significantly the overall stellar metallicity. The flat or negative slopes of the remaining six stars are consistent with recent suggestions of a planet formation signature, although we show that the trends may be the result of Galactic chemical evolution.

Schuler, Simon C.; Cunha, Katia; Smith, Verne V. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Flateau, Davin [Department of Physics, University of Cincinnati, Cincinnati, OH 45221 (United States); King, Jeremy R. [Department of Physics and Astronomy, Clemson University, 118 Kinard Laboratory, Clemson, SC 29634 (United States); Ghezzi, Luan, E-mail: sschuler@noao.edu, E-mail: kcunha@noao.edu, E-mail: vsmith@noao.edu, E-mail: flateadc@mail.uc.edu, E-mail: luan@on.br, E-mail: jking2@clemson.edu [Observatorio Nacional, Rua General Jose Cristino, 77, 20921-400 Sao Cristovao, Rio de Janeiro, RJ (Brazil)

2011-05-01

32

U.S. temperature and drought: Recent anomalies and trends  

NASA Astrophysics Data System (ADS)

The spring and summer (March through August) of 2011-2012 set many new climatological records across the contiguous United States, including the hottest month in the instrumental record: July 2012. Various measures of temperature extremes and drought severity serve to put this period into historical perspective (1895 to present) and to assess to what extent the recent anomalies are consistent with observed trends. During spring and summer, anomalously high temperatures can combine with unusually dry conditions to amplify temperature and drought feedbacks. Observational data from 2011 and 2012 are strongly suggestive of such an amplification and reveal a number of significant trends for various measures of high temperatures in the United States.

Karl, T. R.; Gleason, B. E.; Menne, M. J.; McMahon, J. R.; Heim, R. R., Jr.; Brewer, M. J.; Kunkel, K. E.; Arndt, D. S.; Privette, J. L.; Bates, J. J.; Groisman, P. Y.; Easterling, D. R.

2012-11-01

33

Spuriously induced temperature trends in the Southeast United States  

NASA Astrophysics Data System (ADS)

This study uses correlation and multiple regression techniques to document differences in annual temperature trends between the National Climatic Data Center (NCDC) Climate Division Database (CDD) and the United States Historical Climate Network (USHCN) for the Southeast United States. Results indicate that an increase (decrease) in elevation and a northward (southward) shift in mean station location in the CDD correspond with decreases (increases) in temperature. Although the movement of station locations in the CDD showed only modest impacts on trends, the effects of the movements are statistically significant, and explain some of the variances in the temperature trends. Results therefore suggest that climate divisions with more rugged terrain and greater shifts in elevation are more susceptible to spuriously generated trends.

Allard, J.; Keim, B. D.

2007-01-01

34

Temperature trends in Malta (central Mediterranean) from 1951 to 2010  

NASA Astrophysics Data System (ADS)

There is as yet scanty published information on climate trends at a local scale within the central Mediterranean region. This is the most updated study that focuses on detailed understanding of air temperature shifts based on standard observations gathered from the Maltese islands. This analysis leads to a number of conclusions, most significant being (1) that the rate of change in the mean temperature is +1.1 °C between 1951 and 2010, (2) a warming trend of +1.2 and +1.1 °C exists in the maximum and minimum temperature, respectively, over the same period, (3) that the strongest anomalous warming has occurred during the last 30 years, particularly during the months of June, August and October, and (4) the local temperature trend is in the same category of air temperature trends detected in the nearby Island of Sicily (Catania, Italy), Perpignan (France) and Dar el-Beida (Algeria). Local data also show differences in the temperature trends, especially pronounced between the two 30-year periods of 1951-1980 and 1981-2010. This study provides an understanding of temperature shifts at recommended small spatio-temporal scales.

Galdies, C.

2012-08-01

35

An I(2) Cointegration Model with Piecewise Linear Trends: Likelihood Analysis and Application  

Microsoft Academic Search

This paper presents likelihood analysis of the I(2) cointegrated vector autoregression with piecewise linear deterministic terms. Limiting behavior of the maximum likelihood estimators are derived, which is used to further derive the limiting distribution of the likelihood ratio statistic for the cointegration ranks, extending the result for I(2) models with a linear trend in Nielsen and Rahbek (2007) and for

Takamitsu Kurita; Heino Bohn Nielsen; Anders Rahbek

2009-01-01

36

Simulation of 20th century temperature trends  

Microsoft Academic Search

Results are reported from simulations with an atmospheric general circulation model (GCM) covering the 20th century. These results focus primarily on the continental surface air temperature (SAT) record, with some discussion of large spatial scale precipitation averages as well. These experiments were conducted using the Max Planck Institute for Meteorology ECHAM3 GCM configured at triangular-21 truncation, giving a spatial resolution

Nicholas E. Graham; Mary Tyree

1998-01-01

37

Radiative forcing and temperature trends from stratospheric ozone changes  

Microsoft Academic Search

Detailed shortwave and longwave radiative transfer models are used to calculate the radiative forcing and temperature trends due to stratospheric ozone depletion. These were calculated using the fixed dynamical heating approximation to adjust the stratospheric temperatures. Recent estimates of stratospheric ozone loss between 1979 and 1991 (from solar backscattered ultraviolet (SBUV) and stratospheric aerosol and gas experiment (SAGE) instruments) and

Piers M. de F. Forster; Keith P. Shine

1997-01-01

38

Temperature trends at high elevations: Patterns across the globe  

Microsoft Academic Search

Most climate models suggest amplification of global warming in high mountains, but observations are less clear. Using comprehensive, homogeneity-adjusted temperature records from over 1000 high elevation stations across the globe, we examine the causes of changing temperature trends with elevation, assessing the roles of free atmospheric change, topography (exposure and aspect), and cryospheric feedback. The data show that observed 20th

N. C. Pepin; J. D. Lundquist

2008-01-01

39

Abundances of Stars with Planets: Trends with Condensation Temperature  

NASA Astrophysics Data System (ADS)

Precise abundances of 18 elements have been derived for 10 stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically <~ 0.05 dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (T c) of the elements in the sense of increasing abundances with increasing T c; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with T c, although slopes of linear least-square fits to the [m/H]-T c relations for all but two stars are smaller here than in previous studies. When considering the refractory elements (T c >900 K) only, which may be more sensitive to planet formation processes, the sample can be separated into a group with positive slopes (four stars) and a group with flat or negative slopes (six stars). The four stars with positive slopes have very close-in giant planets (three at 0.05 AU) and slopes that fall above the general Galactic chemical evolution trend. We suggest that these stars have accreted refractory-rich planet material but not to the extent that would increase significantly the overall stellar metallicity. The flat or negative slopes of the remaining six stars are consistent with recent suggestions of a planet formation signature, although we show that the trends may be the result of Galactic chemical evolution. Based on observations with the High Resolution Spectrograph on the Hobby-Eberly Telescope, which is operated by McDonald Observatory on behalf of the University of Texas at Austin, Pennsylvania State University, Standford University, the Ludwig-Maximilians-Universität München, and the Georg-August-Universität, Göttingen. Based on observations made with the FEROS instrument on the MPG/ESO 2.2 m telescope at La Silla (Chile), under the agreement ESO-Observatório Nacional/MCT.

Schuler, Simon C.; Flateau, Davin; Cunha, Katia; King, Jeremy R.; Ghezzi, Luan; Smith, Verne V.

2011-05-01

40

Urban Bias in Area-averaged Surface Air Temperature Trends.  

NASA Astrophysics Data System (ADS)

A data set derived from the United States Historical Climate Network has been compared to two global land-based temperature data sets that have been commonly cited in connection with the detection of the greenhouse effect and in other studies of climate change. Results indicate that in the United States the two global land-based temperature data sets have an urban bias between +6.1°C and +0.4°C over the twentieth century (1901-84). This bias is as large or larger than the overall temperature trend in the United States during this time period, +0.16°C/84 yr. Temperature trends indicate an increasing temperature from the turn of the century to the 1930s but a decrease thereafter. By comparison, the global temperature trends during the same period are between +0.4°C/84 yr and +0.6°C/84 yr. At this time, we can only speculate on the magnitude of the urban bias in the global land-based data sets for other parts of the globe, but the magnitude of the bias in the United States compared to the overall temperature trend underscores the need for a thorough global study.

Karl, Thomas R.; Jones, Philip D.

1989-03-01

41

Linear Relationship between Air Pressure and Temperature Using TI Calculator  

Microsoft Academic Search

There are many relationships within Meteorology that can be interpreted through math. Specifically, the relationship between air temperature and evaporation is a linear relationship. As air temperature increases, then evaporation increases and there is more water vapor in the air.

Nate Ruder

2006-01-01

42

Temperature and Malaria Trends in Highland East Africa  

PubMed Central

There has been considerable debate on the existence of trends in climate in the highlands of East Africa and hypotheses about their potential effect on the trends in malaria in the region. We apply a new robust trend test to mean temperature time series data from three editions of the University of East Anglia's Climatic Research Unit database (CRU TS) for several relevant locations. We find significant trends in the data extracted from newer editions of the database but not in the older version for periods ending in 1996. The trends in the newer data are even more significant when post-1996 data are added to the samples. We also test for trends in the data from the Kericho meteorological station prepared by Omumbo et al. We find no significant trend in the 1979-1995 period but a highly significant trend in the full 1979-2009 sample. However, although the malaria cases observed at Kericho, Kenya rose during a period of resurgent epidemics (1994-2002) they have since returned to a low level. A large assembly of parasite rate surveys from the region, stratified by altitude, show that this decrease in malaria prevalence is not limited to Kericho.

Stern, David I.; Gething, Peter W.; Kabaria, Caroline W.; Temperley, William H.; Noor, Abdisalan M.; Okiro, Emelda A.; Shanks, G. Dennis; Snow, Robert W.; Hay, Simon I.

2011-01-01

43

Malaria resurgence in the East African highlands: Temperature trends revisited  

PubMed Central

The incidence of malaria in the East African highlands has increased since the end of the 1970s. The role of climate change in the exacerbation of the disease has been controversial, and the specific influence of rising temperature (warming) has been highly debated following a previous study reporting no evidence to support a trend in temperature. We revisit this result using the same temperature data, now updated to the present from 1950 to 2002 for four high-altitude sites in East Africa where malaria has become a serious public health problem. With both nonparametric and parametric statistical analyses, we find evidence for a significant warming trend at all sites. To assess the biological significance of this trend, we drive a dynamical model for the population dynamics of the mosquito vector with the temperature time series and the corresponding detrended versions. This approach suggests that the observed temperature changes would be significantly amplified by the mosquito population dynamics with a difference in the biological response at least 1 order of magnitude larger than that in the environmental variable. Our results emphasize the importance of considering not just the statistical significance of climate trends but also their biological implications with dynamical models.

Pascual, M.; Ahumada, J. A.; Chaves, L. F.; Rodo, X.; Bouma, M.

2006-01-01

44

Room Temperature Giant and Linear Magnetoresistance in Topological Insulator Bi2Te3 Nanosheets  

NASA Astrophysics Data System (ADS)

Topological insulators, a new class of condensed matter having bulk insulating states and gapless metallic surface states, have demonstrated fascinating quantum effects. However, the potential practical applications of the topological insulators are still under exploration worldwide. We demonstrate that nanosheets of a Bi2Te3 topological insulator several quintuple layers thick display giant and linear magnetoresistance. The giant and linear magnetoresistance achieved is as high as over 600% at room temperature, with a trend towards further increase at higher temperatures, as well as being weakly temperature-dependent and linear with the field, without any sign of saturation at measured fields up to 13 T. Furthermore, we observed a magnetic field induced gap below 10 K. The observation of giant and linear magnetoresistance paves the way for 3D topological insulators to be useful for practical applications in magnetoelectronic sensors such as disk reading heads, mechatronics, and other multifunctional electromagnetic applications.

Wang, Xiaolin; Du, Yi; Dou, Shixue; Zhang, Chao

2012-06-01

45

Room temperature giant and linear magnetoresistance in topological insulator Bi2Te3 nanosheets.  

PubMed

Topological insulators, a new class of condensed matter having bulk insulating states and gapless metallic surface states, have demonstrated fascinating quantum effects. However, the potential practical applications of the topological insulators are still under exploration worldwide. We demonstrate that nanosheets of a Bi(2)Te(3) topological insulator several quintuple layers thick display giant and linear magnetoresistance. The giant and linear magnetoresistance achieved is as high as over 600% at room temperature, with a trend towards further increase at higher temperatures, as well as being weakly temperature-dependent and linear with the field, without any sign of saturation at measured fields up to 13 T. Furthermore, we observed a magnetic field induced gap below 10 K. The observation of giant and linear magnetoresistance paves the way for 3D topological insulators to be useful for practical applications in magnetoelectronic sensors such as disk reading heads, mechatronics, and other multifunctional electromagnetic applications. PMID:23005006

Wang, Xiaolin; Du, Yi; Dou, Shixue; Zhang, Chao

2012-06-29

46

Tropospheric Temperature Trends on Decadal Scale from Measurements on Aqua  

NASA Astrophysics Data System (ADS)

We use the Atmospheric Infrared Sounder (AIRS) and Advance Microwave Sounding Unit (AMSU) measurements carried out on Aqua satellite in 2002-2011 to infer mid-tropospheric temperature variability on decadal time scale. Since AMSU soundings are independent on the CO2 its measurements track natural climate variability. However the AIRS sounding channels at AMSU comparable levels are sensitive to the changes in CO2. The difference between AIRS and AMSU removes the natural variability and reveals the variability of CO2. The trend in AIRS data is determined accurately. Thus its surface channels drift less than 5 mK/yr based on the validation with sea surface temperatures measured by ocean buys. The AMSU weighing functions do not localized near the sea surface. Comparison of trends in the difference record with the CO2 trends found from the ground stations and with the trends determined directly from the mid-tropospheric global CO2 retrieved from the same satellite data allows us to evaluate the long-term stability of the widely used AMSU measurements, and, once the stability is established, to use the AMSU-AIRS difference records for diagnostic of the atmospheric CO2 data. The analysis of AMSU-AIRS differences reveals different trends over oceans, over localized land regions, and zonally averaged regions, which we interpret as related to CO2 transport effects. This work was supported by the Jet Propulsion Laboratory of the California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Ruzmaikin, A.; Aumann, H. H.

2011-12-01

47

Spatial patterns of linear and nonparametric long-term trends in Baltic sea-level variability  

NASA Astrophysics Data System (ADS)

The study of long-term trends in tide gauge data is important for understanding the present and future risk of changes in sea-level variability for coastal zones, particularly with respect to the ongoing debate on climate change impacts. Traditionally, most corresponding analyses have exclusively focused on trends in mean sea-level. However, such studies are not able to provide sufficient information about changes in the full probability distribution (especially in the more extreme quantiles). As an alternative, we apply quantile regression (QR) for studying changes in arbitrary quantiles of sea-level variability. For this purpose, we chose two different QR approaches and discuss the advantages and disadvantages of different settings. In particular, traditional linear QR poses very restrictive assumptions that are often not met in reality. For monthly data from 47 tide gauges from along the Baltic Sea coast, the spatial patterns of quantile trends obtained in a linear and nonparametric (spline-based) framework display marked differences, which need to be understood in order to fully assess the impact of future changes in sea-level variability on coastal areas. In general, QR demonstrates that the general variability of Baltic sea-level has increased over the last decades. Linear quantile trends estimated for sliding windows in time reveal a wide-spread acceleration of trends in the median, but only localised changes in the rates of lower and upper quantiles.

Donner, R. V.; Ehrcke, R.; Barbosa, S. M.; Wagner, J.; Donges, J. F.; Kurths, J.

2012-04-01

48

Spatial patterns of linear and nonparametric long-term trends in Baltic sea-level variability  

NASA Astrophysics Data System (ADS)

The study of long-term trends in tide gauge data is important for understanding the present and future risk of changes in sea-level variability for coastal zones, particularly with respect to the ongoing debate on climate change impacts. Traditionally, most corresponding analyses have exclusively focused on trends in mean sea-level. However, such studies are not able to provide sufficient information about changes in the full probability distribution (especially in the more extreme quantiles). As an alternative, in this paper we apply quantile regression (QR) for studying changes in arbitrary quantiles of sea-level variability. For this purpose, we chose two different QR approaches and discuss the advantages and disadvantages of different settings. In particular, traditional linear QR poses very restrictive assumptions that are often not met in reality. For monthly data from 47 tide gauges from along the Baltic Sea coast, the spatial patterns of quantile trends obtained in linear and nonparametric (spline-based) frameworks display marked differences, which need to be understood in order to fully assess the impact of future changes in sea-level variability on coastal areas. In general, QR demonstrates that the general variability of Baltic sea-level has increased over the last decades. Linear quantile trends estimated for sliding windows in time reveal a wide-spread acceleration of trends in the median, but only localised changes in the rates of changes in the lower and upper quantiles.

Donner, R. V.; Ehrcke, R.; Barbosa, S. M.; Wagner, J.; Donges, J. F.; Kurths, J.

2012-02-01

49

A general and optimal approach for three inventory models with a linear trend in demand  

Microsoft Academic Search

This study provides a general and simple algorithm to obtain an optimal solution for three inventory models with a replenishment batching policy, production batching policy, and an integrated replenishment\\/production batching policy in a manufacturing system, under a finite time horizon and linear trend in demand. This study determines the replenishment or production schedule with one general equation for these three

Hsin Rau; Bing-Chang OuYang

2007-01-01

50

Trends in Snow Cover and Temperature in Alaska  

NSDL National Science Digital Library

This lesson is designed to help students gain knowledge in using the MY NASA DATA Live Access Server (LAS) to specify and download a microset of data, and then to use the data to compare NASA satellite data observations with surface measurements of snow cover and temperature. Students will obtain snow cover and surface temperature data for a locale in Alaska, plot the data, and then investigate seasonal trends in snow cover, and the relationship between snow cover and surface temperature at that locale. The lesson provides detailed procedure, related links and sample graphs, follow-up questions and extensions, and Teacher Notes.

2010-03-14

51

Accessing Recent Trend of Land Surface Temperature from Satellite Observations  

NASA Astrophysics Data System (ADS)

Land surface temperature (LST) is an important element to measure the state of the terrestrial ecosystems and to study the surface energy budgets. In support of the land cover/land use change related international program MAIRS (Monsoon Asia Integrated Regional Study), we have collected the global monthly LST measured by MODIS since the beginning of the missions. The MODIS LST time series have ~11 years of data from Terra since 2000 and ~9 years of data from Aqua since 2002, which makes possible to study the recent climate, such as trend and variability. In this study, monthly climatology from two satellite platforms are calculated and compared. The spatial patterns of LST trends are accessed, focusing on the Asian Monsoon region. Furthermore, the MODIS LST trends are compared with the skin temperature trend from the NASA's atmospheric assimilation model, MERRA (MODERN ERA RETROSPECTIVE-ANALYSIS FOR RESEARCH AND APPLICATIONS), which has longer data record since 1979. The calculated climatology and anomaly of MODIS LST will be integrated into the online visualization system, Giovanni, at NASA GES DISC for easy access and use by scientists and general public.

Shen, S.; Leptoukh, G. G.; Romanov, P.

2011-12-01

52

The Impact of Urbanization on Global Surface Temperature Trends  

NASA Astrophysics Data System (ADS)

Rapid urbanization over the past half century has contributed to a warming bias in some Global Historical Climatological Network (GHCN) temperature records. The extent to which this urban warming bias contributes to global temperature trends remains largely unquantified both in raw and homogenized datasets, and no clear consensus exists on the need for specific urbanization corrections in global temperature reconstructions. In order to determine the magnitude of urbanization bias in the dataset, and to quantify the extent to which the newly adopted GHCN homogenization procedures correct for it, we examine minimum, maximum, and mean temperature trends from stations classified using numerous proxies for urbanity including MODIS, urban boundaries (GRUMP), satellite nightlights, and impermeable surface area, each created from publicly available high-resolution GIS datasets. These urbanity proxies are used to segment stations into separate urban and rural sets, and temperature differences between the two are calculated using both spatial gridding and station pairing approaches. The analysis is performed on raw and homogenized monthly data derived from the Global Historical Climatology Network (GHCN) Daily dataset that includes approximately 24,000 temperature measurement stations during the period from 1960 to present. Homogenized data that have been further adjusted using NASA GISS's Satellite Nightlight urban correction are also evaluated. The magnitude of the urbanization bias in the raw data and the degree to which this bias is mitigated with homogenization is discussed.

Hausfather, Z.; Mosher, S.; Menne, M. J.; Williams, C. N.; Stokes, N.; Jones, D.

2011-12-01

53

Regional tropical temperature trends from radiosondes, reanalyses, and satellite observations  

NASA Astrophysics Data System (ADS)

We compare seasonal 20th century atmospheric temperature trends in the Tropics (30°S-30°N) from radiosonde observations (CHUAN, HadAT, IUK, RAOBCORE/RICH, RATPAC) and reanalyses (ERA-40, NCEP/NCAR (NNR), Twentieth Century reanalysis (20CR), CFSR, ERA-Interim, MERRA). Large differences are found between the magnitudes, vertical profiles of the temperature trends (even for time periods > 3 decades), and chronological sequences of bidecadal, regional warming and cooling periods in the reanalyses. Long term zonal mean vertical trend profiles from CHUAN and from the reanalyses reaching back to the time before the satellite era reveal an amplified upper tropospheric warming for all longest periods of dataset overlap (1901-99, 1901-57, 1948-99, 1957-99). ERA-40 and NNR show a second warming maximum in the lower troposphere which is missing in 20CR. The agreement of the vertical structure and temporal behaviour of regional, bidecadal trends in the long reanalyses for 4 regions in the Tropics with CHUAN is generally best for ERA-40, followed by a less good agreement with trends from NNR and 20CR. The performance of ERA-40 is best in the Americas sector, and less so in the Asian and Pacific sectors. The agreement of NNR with CHUAN is significantly worse than that of ERA-40 for all tropical regions, especially with respect to the vertical structure of the trends. The 20CR temporal behaviour and vertical structure of the tropical trends is often different from CHUAN, ERA-40 and NNR, especially around the tropopause, and in all sectors. For the more recent but shorter reanalyses, ERA-Interim is generally closer to ERA-40 than CFSR and MERRA. For the period of overlap (1951-99) CHUAN itself agrees reasonably well with HadAT, IUK, RAOBCORE/RICH and RATPAC on the general picture. However, some disagreement on the trend sign can be seen a) for the American sector during 1961-80 with RAOBCORE/RICH and RATPAC and during 1971-90 with RAOBCORE/RICH, b) for the Asian sector during 1961-80 with RAOBCORE/RICH.

Stickler, Alexander; Brönnimann, Stefan

2013-04-01

54

Spatially varying temperature trends in a Central California Estuary  

Microsoft Academic Search

We consider monthly temperature data collected over a period of 16 years at 24 stations in the estuarine wetlands of the Elkhorn\\u000a Slough watershed, located in the Monterey Bay area in Central California, USA. Our goal is to develop a statistical model\\u000a in order to separate the seasonal cycle, short-term fluctuations, and long-term trends, while accounting for the spatial variability

Ricardo T. Lemos; Bruno Sansó; Marc Los Huertos

2007-01-01

55

Temperature trends during the Present and Last interglacial periods - A multi-model-data comparison  

NASA Astrophysics Data System (ADS)

We present the first multi-model-data comparison of transient millennial-scale temperature changes through the Present and Last interglacial periods (PIG and LIG respectively). Though primarily driven by insolation changes associated with well-known variations in Earth's orbital parameters, the response of the climate system includes a diversity of feedbacks involving the atmosphere, ocean, sea ice, vegetation and land ice. A thorough multi-model-data comparison is essential to assess the ability of climate models to resolve interglacial climate trends and to help in understanding the recorded climatic signal and the underlying climate dynamics. During the last decade, substantial progress has been made by documenting past climate variability from new archives with improved chronologies for the PIG and LIG periods. In parallel, the increased computing capacities as well as the development of computationally efficient climate models have enabled transient multi-millennial climate simulations. This allows us to compare PIG and LIG multi-millennial temperature trends derived from transient climate experiments (9 different climate models) with alkenone-based temperature reconstructions (117 locations globally distributed; about 45% of them with the LIG interval) and ice-core-based temperature profiles from Greenland and Antarctica (12 sites; 6 include the LIG). Our analysis shows that in Greenland and Antarctica the multi-model-mean temperature trends for the warmest months compare well with ice-core based temperature reconstructions. Regarding reconstructed annual mean temperatures based on alkenone-data, models and data are in reasonable agreement with some exceptions at high-latitude areas. The next step in the analysis is to assess whether the simulated warmest month temperature trends of the PIG and LIG periods are linearly scaled to the orbital forcing. In the Northern Hemisphere the models consistently show a linear response to the trends in the insolation forcing for both interglacial periods. The exceptions are the Arctic region, where the simulated trend are relatively small compared to that of the insolation signal and the Sahel and Indian regions where a negative relation is observed. For the Southern Hemisphere climate models are consistent in the simulated warmest month temperature trends but the relation with the insolation trends is more complex. We find a positive relation over South America and Africa, and a positive though strongly dampened response over the low and mid-latitude oceans of the Southern Hemisphere. However, despite the positive trend in the warmest month insolation forcing, which is especially large in the LIG period, the simulations lack any substantial temperature changes for the Southern Ocean and the Antarctic region. This suggests that, regardless of the large differences in model-complexity, the climate models consistently show that the increase in summer insolation is balanced out by a considerable growth of the Southern Ocean sea-ice cover resulting from obliquity-related changes in the seasonal distribution of insolation.

Bakker, Pepijn; Masson-Delmotte, Valérie; Martrat, Belen; Charbit, Sylvie; Renssen, Hans

2013-04-01

56

A Study of Temperature Trends Using Rural Sites Identified from MODIS Classifications  

NASA Astrophysics Data System (ADS)

Does urban heating effect the estimates of global average land surface temperature? We study this possible source of bias by applying an urban-rural classification based on MODIS satellite data to the Berkeley Earth temperature dataset compilation of 39,028 sites from 10 different publicly available sources. We identify a a rural subset of 16,132 sites chosen to be distant from MODIS-identified urban areas. The distribution of linear temperature trends for this subset of sites is compared to the distribution for all sites. While the trend distributions are broad, with one-third of the stations in the US and worldwide having a negative trend, both distributions show significant warming. For our primary analysis, we estimate time series of the Earth's average land temperature using the Berkeley Earth methodology applied to the full dataset and the rural subset. We observe the opposite of an urban heating effect over the period 1950 to 2010, with a slope of -0.19 ± 0.19 °C / century (95% confidence), a comparably small effect as the estimates published by previous groups. Given the small size of the effect, and its negative sign, we conclude that urban warming does not substantially affect estimates of recent global warming -- confirming the key conclusion of the previous groups' work.

Wickham, C.; Curry, J. A.; Groom, D.; Jacobsen, B.; Muller, R. A.; Perlmutter, S.; Rohde, R. A.; Rosenfeld, A.; Wurtele, J.

2011-12-01

57

Multi-decadal surface temperature trends in East Antarctica inferred from borehole firn temperature measurements and geophysical inverse methods  

NASA Astrophysics Data System (ADS)

The climate trend of the Antarctic interior remains unclear relative to the rest of the globe because of a lack of long-term weather records. Recent studies by other authors utilizing sparse available records, satellite data, and models have estimated a significant warming trend in the near-surface air temperature in West Antarctica and weak and poorly constrained warming trend in East Antarctica for the past 50 years. In this dissertation, firn thermal profiling was used to detect multi-decadal surface temperature trends in the interior of East Antarctica where few previous records of any kind exist. The surface temperature inversion from firn temperature profiles provides a climate reconstruction independent of firn chemistry, sparse weather data, satellite data, or ice cores, and therefore may be used in conjunction with these data sources for corroboration of climate trends over the large ice sheets. During the Norwegian-U.S. IPY Scientific Traverse of East Antarctica, in the austral summers of 2007--08 and 2008--09, thermal-profiling telemetry units were installed at five locations. Each unit consists of 16 PRTs (Platinum Resistance Thermometers) distributed in a back-filled borehole of 80 to 90 m deep. The accuracy of the temperature measurement is 0.03 K. Geophysical inverse methods (linearized and Monte Carlo inversion) were applied to one full year of data collected from three units installed near the ice divide in the Dome Fuji/Pole of Inaccessibility region and one on Recovery Lake B, situated >500 km south to south-west of and >1000 m lower in altitude than sites near the ice divide. Three sites near the ice divide indicate that the mean surface temperatures have increased approximately 1 to 1.5 K within the past ˜50 years although the onset and the duration of this warming vary by site. On the other hand, slight cooling to no change was detected at the Recovery Lake B site. Although uncertainties remain due to limitations of the method, these results raise the possibility of an interesting recent climate pattern in East Antarctica; significant warming trend near the ice divide and cooling to no change off the divide.

Muto, Atsuhiro

58

Detection of temporal trends of ?- and ?-chlordane in Lake Erie fish communities using dynamic linear modeling.  

PubMed

Dynamic linear modeling (DLM) analysis was performed to identify the long-term temporal trends of two toxic components of the technical chlordane pesticide, ?- and ?-chlordane, in skinless-boneless muscle tissues of a number of sport fish species in Lake Erie. Our analysis considers the fish length as a covariate of the chlordane concentrations. The ?-chlordane models for the coho salmon, channel catfish, rainbow trout, and common carp showed continuously decreasing trends during the entire 30+ year survey period (1976-2007). The ?-chlordane models demonstrated similar trends for the coho salmon, channel catfish, and common carp. These fish species had higher levels of ?- and ?-chlordane in their muscle tissues. The ?- and ?-chlordane levels in freshwater drum, smallmouth bass, walleye, white bass, whitefish, and yellow perch decreased until the mid-1980s and hovered at levels around the detection limits for the remaining period. The pesticide biotransformation process, the reduction of contaminant emissions to the environment, the feeding habits of the different fish species, and the food-web alterations induced by the introduction of aquatic invasive species are some of the hypotheses proposed to explain the observed temporal trends in different fish species in Lake Erie. PMID:21536330

Ekram Azim, M; Letchumanan, Michelle; Abu Rayash, Azzam; Shimoda, Yuko; Bhavsar, Satyendra P; Arhonditsis, George B

2011-05-04

59

Trends of temperature extremes in China and their relationship with global temperature anomalies  

NASA Astrophysics Data System (ADS)

Changes of temperature extremes over China were evaluated using daily maximum and minimum temperature data from 591 stations for the period 1961-2002. A set of indices of warm extremes, cold extremes and daily temperature range (DTR) extremes was studied with a focus on trends. The results showed that the frequency of warm extremes (F_WE) increased obviously in most parts of China, and the intensity of warm extremes (I_WE) increased significantly in northern China. The opposite distribution was found in the frequency and intensity of cold extremes. The frequency of high DTR extremes was relatively uniform with that of intensity: an obvious increasing trend was located over western China and the east coast, while significant decreases occurred in central, southeastern and northeastern China; the opposite distribution was found for low DTR extreme days. Seasonal trends illustrated that both F_WE and I_WE showed significant increasing trends, especially over northeastern China and along the Yangtze Valley basin in spring and winter. A correlation technique was used to link extreme temperature anomalies over China with global temperature anomalies. Three key regions were identified, as follows: northeastern China and its coastal areas, the high-latitude regions above 40°N, and southwestern China and the equatorial eastern Pacific.

Huang, Danqing; Qian, Yongfu; Zhu, Jian

2010-07-01

60

Attribution of Global Mean Temperature Trends in the Middle Atmosphere: Model Diagnostics  

NASA Astrophysics Data System (ADS)

Global-mean temperature trends in the middle atmosphere can be explained by changes in the radiative energy budget forced by atmospheric composition changes. Here, we analyze past and future temperature trends and changes in radiative heating agents in model simulations performed with the Canadian Middle Atmosphere Model (CMAM). We identify two periods of near-linear changes: 1975-1995, during the period of ozone depletion, and 2010-2040, during the period of ozone recovery. Using a 1D radiative-convective model it is shown that the past and future temperature trends can be understood as a combination of effects from changes in CO2, O3 and H2O. The results confirm the generally accepted view that while enhanced CO2 acts to cool the middle atmosphere, temperature trends are modulated by long-term changes in ozone concentrations: Halogen-induced ozone depletion in the past has lead to enhanced cooling whereas ozone recovery in the future will reduce the CO2 effect. It is also shown that in the upper part of the model domain the effect of ozone heating is not local in the vertical, which has important implications for multiple regression analysis, which assumes local control. For example increase of ozone near the stratopause in the future leads to an overall warming effect from ozone in the mesosphere (due to IR transfer), even though the mesospheric ozone concentration is actually decreasing (due to H2O increase). The importance of changes in the 9.6 ?m O3 band cooling and in the mesospheric NIR CO2 heating is also analyzed.

Jonsson, A. I.; Fomichev, V. I.

2009-05-01

61

An alternative explanation for differential temperature trends at the surface and in the lower troposphere  

Microsoft Academic Search

This paper investigates surface and satellite temperature trends over the period from 1979 to 2008. Surface temperature data sets from the National Climate Data Center and the Hadley Center show larger trends over the 30-year period than the lower-tropospheric data from the University of Alabama in Huntsville and Remote Sensing Systems data sets. The differences between trends observed in the

Philip J. Klotzbach; Roger A. Pielke Sr; Roger A. Pielke Jr; John R. Christy; Richard T. McNider

2009-01-01

62

Influence of changes in sea ice concentration and cloud cover on recent Arctic surface temperature trends  

Microsoft Academic Search

The influence of trends in sea ice concentration (SIC) and cloud cover on trends in surface temperature over the Arctic Ocean from 1982 to 2004 is investigated analytically, and evaluated empirically with satellite products. The results demonstrate that changes in SIC and cloud cover played major roles in the magnitude of recent Arctic surface temperature trends. Significant surface warming associated

Yinghui Liu; Jeffrey R. Key; Xuanji Wang

2009-01-01

63

Amplification of surface temperature trends and variability in thetropical atmosphere  

SciTech Connect

The month-to-month variability of tropical temperatures is larger in the troposphere than at the Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations, and is consistent with basic theory. On multi-decadal timescales, tropospheric amplification of surface warming is a robust feature of model simulations, but occurs in only one observational dataset. Other observations show weak or even negative amplification. These results suggest that either different physical mechanisms control amplification processes on monthly and decadal timescales, and models fail to capture such behavior, or (more plausibly) that residual errors in several observational datasets used here affect their representation of long-term trends.

Santer, B.D.; Wigley, T.M.L.; Mears, C.; Wentz, F.J.; Klein,S.A.; Seidel, D.J.; Taylor, K.E.; Thorne, P.W.; Wehner, M.F.; Gleckler,P.J.; Boyle, J.S.; Collins, W.D.; Dixon, K.W.; Doutriaux, C.; Free, M.; Fu, Q.; Hansen, J.E.; Jones, G.S.; Ruedy, R.; Karl, T.R.; Lanzante, J.R.; Meehl, G.A.; Ramaswamy, V.; Russell, G.; Schmidt, G.A.

2005-08-11

64

A highly linear single p-n junction temperature sensor  

Microsoft Academic Search

A temperature sensor based on the use of two forward-biased p-n junctions is known to exhibit good linearity. An alternative sensor configuration, based on the same principle, but employing only one p-n junction is presented in this paper. The forward current through the p-n junction is switched alternately between two fixed values, and the difference between the corresponding voltages is

R. C. S. Freire; S. Daher; G. S. Deep

1994-01-01

65

CALL FOR PAPERS: Special issue on Current Trends in Integrability and Non Linear Phenomena Special issue on Current Trends in Integrability and Non Linear Phenomena  

NASA Astrophysics Data System (ADS)

This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to integrability and nonlinear phenomena. The motivation behind this special issue is to summarize in a single comprehensive publication, the main aspects (past and present), latest developments, different viewpoints and the directions being followed in this multidisciplinary field. We hope that such a special issue could become a particularly valuable reference for the broad scientific community working in integrability and nonlinear phenomena. Editorial policy The Editorial Board has invited D Gómez-Ullate, S Lombardo, M Mañas, M Mazzocco, F Nijhoff and M Sommacal to serve as Guest Editors for the special issue. Their criteria for the acceptance of contributions are as follows. The subject of the paper should relate to the following list of subjects: Integrable systems (including quantum and discrete) and applications Dynamical systems: Hamiltonian systems and dynamics in the complex domain Nonlinear waves, soliton equations and applications Nonlinear ODEs including Painlevé equations and isomonodromic deformations Symmetries and perturbative methods in the classification of integrable PDEs Infinite dimensional Lie algebras and integrable systems Orthogonal Polynomials, Random Matrix Theory All contributions will be refereed and processed according to the usual procedure of the journal. Papers should report original and significant research that has not already been published. Guidelines for preparation of contributions The DEADLINE for contributed papers will be 28 February 2010. This deadline will allow the special issue to appear in October 2010. There is a nominal page limit of 15 printed pages per contribution (invited review papers can be longer). For papers exceeding this limit, the Guest Editors reserve the right to request a reduction in length. Further advice on publishing your work in Journal of Physics A: Mathematical and Theoretical may be found at www.iop.org/Journals/jphysa. Contributions to the special issue should if possible be submitted electronically by web upload at www.iop.org/Journals/jphysa, or by email to jphysa@iop.org, quoting 'JPhysA Special Issue: Current Trends in Integrability and Non Linear Phenomena' Submissions should ideally be in standard LaTeX form. Please see the website for further information on electronic submissions. Authors unable to submit electronically may send hard-copy contributions to: Publishing Administrators, Journal of Physics A, IOP Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. Please quote 'JPhysA Special Issue—Current Trends in Integrability and Non Linear Phenomena'. All contributions should be accompanied by a read-me file or covering letter giving the postal and e-mail addresses for correspondence. The Publishing Office should be notified of any subsequent change of address. This special issue will be published in the paper and online version of the journal.

Gómez-Ullate, D.; Lombardo, S.; Mañas, M.; Mazzocco, M.; Nijhoff, F.; Sommacal, M.

2009-11-01

66

CALL FOR PAPERS: Special issue on Current Trends in Integrability and Non Linear Phenomena Special issue on Current Trends in Integrability and Non Linear Phenomena  

NASA Astrophysics Data System (ADS)

This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to integrability and nonlinear phenomena. The motivation behind this special issue is to summarize in a single comprehensive publication, the main aspects (past and present), latest developments, different viewpoints and the directions being followed in this multidisciplinary field. We hope that such a special issue could become a particularly valuable reference for the broad scientific community working in integrability and nonlinear phenomena. Editorial policy The Editorial Board has invited D Gómez-Ullate, S Lombardo, M Mañas, M Mazzocco, F Nijhoff and M Sommacal to serve as Guest Editors for the special issue. Their criteria for the acceptance of contributions are as follows. The subject of the paper should relate to the following list of subjects: Integrable systems (including quantum and discrete) and applications Dynamical systems: Hamiltonian systems and dynamics in the complex domain Nonlinear waves, soliton equations and applications Nonlinear ODEs including Painlevé equations and isomonodromic deformations Symmetries and perturbative methods in the classification of integrable PDEs Infinite dimensional Lie algebras and integrable systems Orthogonal Polynomials, Random Matrix Theory All contributions will be refereed and processed according to the usual procedure of the journal. Papers should report original and significant research that has not already been published. Guidelines for preparation of contributions The DEADLINE for contributed papers will be 28 February 2010. This deadline will allow the special issue to appear in October 2010. There is a nominal page limit of 15 printed pages per contribution (invited review papers can be longer). For papers exceeding this limit, the Guest Editors reserve the right to request a reduction in length. Further advice on publishing your work in Journal of Physics A: Mathematical and Theoretical may be found at www.iop.org/Journals/jphysa. Contributions to the special issue should if possible be submitted electronically by web upload at www.iop.org/Journals/jphysa, or by email to jphysa@iop.org, quoting 'JPhysA Special Issue: Current Trends in Integrability and Non Linear Phenomena' Submissions should ideally be in standard LaTeX form. Please see the website for further information on electronic submissions. Authors unable to submit electronically may send hard-copy contributions to: Publishing Administrators, Journal of Physics A, IOP Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. Please quote 'JPhysA Special Issue—Current Trends in Integrability and Non Linear Phenomena'. All contributions should be accompanied by a read-me file or covering letter giving the postal and e-mail addresses for correspondence. The Publishing Office should be notified of any subsequent change of address. This special issue will be published in the paper and online version of the journal.

Gómez-Ullate, D.; Lombardo, S.; Mañas, M.; Mazzocco, M.; Nijhoff, F.; Sommacal, M.

2009-12-01

67

Difficulties in Obtaining Reliable Temperature Trends: Reconciling the Surface and Satellite Microwave Sounding Unit Records.  

NASA Astrophysics Data System (ADS)

A chronic difficulty in obtaining reliable climate records from satellites has been changes in instruments, platforms, equator-crossing times, and algorithms. The microwave sounding unit (MSU) tropospheric temperature record has overcome some of these problems, but evidence is presented that it too contains unreliable trends over a 17-yr period (1979-95) because of transitions involving different satellites and complications arising from nonatmospheric signals associated with the surface. The two primary MSU measures of tropospheric temperature contain different error characteristics and trends. The MSU channel 2 record exhibits a slight warming trend since 1979. Its broad vertical weighting function means that the temperature signal originates from throughout the troposphere and part of the lower stratosphere; intersatellite comparisons reveal low noise levels. Off-nadir channel 2 data are combined to provide an adjusted weighting function (called MSU 2R) without the stratospheric signal, but at a cost of an increased influence of surface emissions. Land surface microwave emissions, which account for about 20% of the total signal, depend on ground temperature and soil moisture and are subject to large variations associated with the diurnal cycle. The result is that MSU 2R noise levels are a factor of 3 larger than for MSU 2 and are sufficient to corrupt trends when several satellite records are merged.After allowing for physical differences between the satellite and surface records, large differences remain in temperature trends over the Tropics where there is a strong and deterministic coupling with the surface. The authors use linear regression with observed sea surface temperatures (SSTs) and an atmospheric general circulation model to relate the tropical MSU and surface datasets. These and alternative analyses of the MSU data, radiosonde data, and comparisons between the MSU 2R and channel 2 records, with estimates of their noise, are used to show that the downward trend in tropical MSU 2R temperatures is very likely spurious. Tropical radiosonde records are of limited use in resolving the discrepancies because of artificial trends arising from changes in instruments or sensors;however, comparisons with Australian radiosondes show a spurious downward jump in MSU 2R in mid-1991, which is not evident in MSU 2. Evaluation of reanalyzed tropical temperatures from the National Centers for Environmental Prediction and the European Centre for Medium-Range Weather Forecasts shows that they contain very different and false trends, as the analyses are only as good as the input database.Statistical analysis of the MSU 2R record objectively identifies two stepwise downward discontinuities that coincide with satellite transitions. The first is in mid-1981, prior to which only one satellite was in operation for much of the time so the diurnal cycle was not well sampled. Tropical SST anomalies over these years were small, in agreement with the Southern Oscillation index, yet the MSU 2R values were anomalously warm by 0.25°C. The second transition from NOAA-10 to NOAA-12 in mid-1991 did not involve an overlap except with NOAA-11, which suffered from a large drift in its equator-crossing times. MSU 2R anomalies have remained anomalously cold since mid-1991 by 0.1°C. Adding the two stepwise discontinuities to the tropical MSU 2R record allows it to be completely reconciled with the SST record within expected noise levels. The statistical results also make physical sense as the tropical satellite anomalies are magnified relative to SST anomalies by a factor of 1.3, which is the amplification expected following the saturated adiabatic lapse rate to the level of the peak weighting function of MSU 2R.

Hurrell, James W.; Trenberth, Kevin E.

1998-05-01

68

Testing for deterministic trends in global sea surface temperature  

Microsoft Academic Search

The identification and estimation of trends is a frequent and fundamental task in the analysis of hydrometeorological records. The task is challenging because even time series generated by purely random processes can exhibit visually appealing trends that can be misleadingly taken as evidence of non-stationary behavior. Hydrometeorological time series exhibiting long range dependence can also exhibit trend-like features that can

Susana Barbosa

2010-01-01

69

A spatial entropy analysis of temperature trends in the United States  

NASA Astrophysics Data System (ADS)

The United States Historical Climatology Network (USHCN) temperature database shows a significant upward trend over the past half century. In this investigation, we calculate the spatial entropy (dissimilarity or disorder) associated with the temperature trends of 1,221 stations in the fully adjusted USHCN. We find that over the network, the spatial entropy levels are significantly and positively related to the observed temperature trends suggesting that stations most unlike their neighbors in terms of temperature change tend to have a higher temperature trend than their neighbors. These results suggest that the USHCN contains some questionable warming signals at some stations, despite the many attempts to quantitatively control for these contaminants.

Balling, Robert C.; Roy, Shouraseni Sen

2004-05-01

70

Trends in Low Temperature Water Gas Shift Reactivity on Transition Metals  

SciTech Connect

Low-temperature water–gas shift reactivity trends on transition metals were investigated with the use of a microkinetic model based on a redox mechanism. It is established that the adsorption energies for carbon monoxide and oxygen can describe to a large extent changes in the remaining activation and adsorption energies through linear correlations. In comparisons with experimental data it is found that the model predicts well the order of catalytic activities for transition metals, although it fails to quantitatively describe the experimental data. This discrepancy could be due to the assumption that the redox mechanism dominates and to the neglect of adsorbate interactions, which play an important role at high coverages. The model predicts that the activity of copper can be improved by increasing the strengths with which carbon monoxide and oxygen are bonded to the surface, thus suggesting possible directions for improving the catalyst for low-temperature WGSR.

Schumacher, N.; Boisen, A.; Dahl, S.; Gokhale, Amit A.; Kandoi, Shampa; Grabow, Lars C.; Dumesic, James A.; Mavrikakis, Manos; Chorkendorff, I.

2005-01-25

71

Homogenization of Chinese daily surface air temperatures and analysis of trends in the extreme temperature indices  

NASA Astrophysics Data System (ADS)

This study first homogenizes time series of daily maximum and minimum temperatures recorded at 825 stations in China over the period from 1951 to 2010, using both metadata and the penalized maximum t test with the first-order autocorrelation being accounted for to detect change points and using the quantile-matching algorithm to adjust the data time series to diminish discontinuities. Station relocation was found to be the main cause for discontinuities, followed by station automation. The effects of discontinuities on estimation of long-term trends in the annual mean and extreme indices of temperature are illustrated. The data homogenization is shown to have improved the spatial consistency of estimated trends. Using the homogenized daily minimum and daily maximum temperature data, this study also analyzes trends in extreme temperature indices. The results show that the vast majority (85%-90%) of the 825 sites have experienced significantly more warm nights and less cold nights since 1951. There have also been more warm days and less cold days since 1951, although these trends are less extensive. About 62% of the 825 sites were found to have experienced significantly more warm days and about 50% significantly less cold days. None of the 825 sites were found to have significantly more cold nights/days or less warm nights/days. These indicate that the warming is stronger in nighttime than in daytime and stronger in winter than in summer. Thus, the diurnal temperature range was found to have significantly decreased at 49% of the 825 sites, with significant increases being identified only at 3% of these sites.

Xu, Wenhui; Li, Qingxiang; Wang, Xiaolan L.; Yang, Su; Cao, Lijuan; Feng, Yang

2013-09-01

72

Estimation of the impact of land-surface forcings on temperature trends in eastern United States  

Microsoft Academic Search

We use the ``observation minus reanalysis'' difference (OMR) method to estimate the impact of land-use changes by computing the difference between the trends of the surface temperature observations (which reflect all the sources of climate forcing, including surface effects) and the NCEP-NCAR reanalysis surface temperatures (only influenced by the assimilated atmospheric temperature trends). This includes not only urbanization effects but

Eugenia Kalnay; Ming Cai; Hong Li; Jayakar Tobin

2006-01-01

73

Estimation of the impact of land-surface forcings on temperature trends in eastern United States  

Microsoft Academic Search

We use the “observation minus reanalysis” difference (OMR) method to estimate the impact of land-use changes by computing the difference between the trends of the surface temperature observations (which reflect all the sources of climate forcing, including surface effects) and the NCEP-NCAR reanalysis surface temperatures (only influenced by the assimilated atmospheric temperature trends). This includes not only urbanization effects but

Eugenia Kalnay; Ming Cai; Hong Li; Jayakar Tobin

2006-01-01

74

Analysis of the impacts of station exposure on the U.S. Historical Climatology Network temperatures and temperature trends  

NASA Astrophysics Data System (ADS)

The recently concluded Surface Stations Project surveyed 82.5% of the U.S. Historical Climatology Network (USHCN) stations and provided a classification based on exposure conditions of each surveyed station, using a rating system employed by the National Oceanic and Atmospheric Administration to develop the U.S. Climate Reference Network. The unique opportunity offered by this completed survey permits an examination of the relationship between USHCN station siting characteristics and temperature trends at national and regional scales and on differences between USHCN temperatures and North American Regional Reanalysis (NARR) temperatures. This initial study examines temperature differences among different levels of siting quality without controlling for other factors such as instrument type. Temperature trend estimates vary according to site classification, with poor siting leading to an overestimate of minimum temperature trends and an underestimate of maximum temperature trends, resulting in particular in a substantial difference in estimates of the diurnal temperature range trends. The opposite-signed differences of maximum and minimum temperature trends are similar in magnitude, so that the overall mean temperature trends are nearly identical across site classifications. Homogeneity adjustments tend to reduce trend differences, but statistically significant differences remain for all but average temperature trends. Comparison of observed temperatures with NARR shows that the most poorly sited stations are warmer compared to NARR than are other stations, and a major portion of this bias is associated with the siting classification rather than the geographical distribution of stations. According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.

Fall, Souleymane; Watts, Anthony; Nielsen-Gammon, John; Jones, Evan; Niyogi, Dev; Christy, John R.; Pielke, Roger A., Sr.

2011-07-01

75

Temporal PCB and mercury trends in Lake Erie fish communities: a dynamic linear modeling analysis.  

PubMed

We performed dynamic linear modeling analysis on fish contaminant data collected from the Ontario Ministry of the Environment and Environment Canada to examine long-term trends of total mercury (THg) and polychlorinated biphenyls (PCBs) in Lake Erie. Several sport fish species (walleye, smallmouth bass, rainbow trout) with differences in their diet habits, food competition strategies and foraging patterns are characterized by weakly increasing trends of their THg levels in Lake Erie after the mid- or late 1990s. Similarly, our analysis shows that the decline rates of the PCB body burdens in white bass, smallmouth bass, freshwater drum and whitefish have slowed down or have switched to weakly increasing rates over the last decade. Our analysis also provides evidence that the rainbow trout and coho salmon PCB concentrations have been decreasing steadily but the associated rates were fairly weak. The systematic shifts in energy trophodynamics along with the food web alterations induced from the introduction of non-native species, the new role of the sediments as a net contaminant source, and the potentially significant fluxes from the atmosphere stand out as some of the hypotheses proposed to explain the limited Lake Erie response in recent years to the various contamination mitigation strategies. PMID:21835464

Sadraddini, Somayeh; Ekram Azim, M; Shimoda, Yuko; Mahmood, Maryam; Bhavsar, Satyendra P; Backus, Sean M; Arhonditsis, George B

2011-08-10

76

Shift changes and monotonic trends in autocorrelated temperature series over Iran  

NASA Astrophysics Data System (ADS)

Temperature data from 29 synoptic stations in Iran for a period of 40 years (1966-2005) were analyzed to test for the existence of monotonic trends and shift changes in the annual, seasonal, and monthly mean air temperature series using the Mann-Kendall and Mann-Whitney tests. The influences of significant lag-1 serial correlation were eliminated from data by the trend-free pre-whitening method prior to the trend analysis. The magnitude of the temperature trends was derived from the Theil-Sen's slope estimator. It was found that annual mean air temperature increased at 25 out of the 29 stations, of which 17 stations showed significant monotonic trends. The magnitude of the annual mean air temperature trends averagely was (+)0.224°C per decade. Most of the stations with the significant positive monotonic trends had a significant upward shift change. The analysis indicated that the change point year of the significant upward shift changes was 1972 for the whole stations except the coastal ones. Moreover, the strongest monotonic increasing trends and upward shift changes were observed in summer especially in August and September. The spatial analysis of the mean air temperature trends revealed the highest numbers of significant monotonic trends in the big cities of Iran. These findings provide more insights for better understanding of regional temperature behavior in the study area.

Tabari, Hossein; Hosseinzadeh Talaee, P.; Ezani, Azadeh; Shifteh Some'E, B.

2011-12-01

77

Shift changes and monotonic trends in autocorrelated temperature series over Iran  

NASA Astrophysics Data System (ADS)

Temperature data from 29 synoptic stations in Iran for a period of 40 years (1966-2005) were analyzed to test for the existence of monotonic trends and shift changes in the annual, seasonal, and monthly mean air temperature series using the Mann-Kendall and Mann-Whitney tests. The influences of significant lag-1 serial correlation were eliminated from data by the trend-free pre-whitening method prior to the trend analysis. The magnitude of the temperature trends was derived from the Theil-Sen's slope estimator. It was found that annual mean air temperature increased at 25 out of the 29 stations, of which 17 stations showed significant monotonic trends. The magnitude of the annual mean air temperature trends averagely was (+)0.224°C per decade. Most of the stations with the significant positive monotonic trends had a significant upward shift change. The analysis indicated that the change point year of the significant upward shift changes was 1972 for the whole stations except the coastal ones. Moreover, the strongest monotonic increasing trends and upward shift changes were observed in summer especially in August and September. The spatial analysis of the mean air temperature trends revealed the highest numbers of significant monotonic trends in the big cities of Iran. These findings provide more insights for better understanding of regional temperature behavior in the study area.

Tabari, Hossein; Hosseinzadeh Talaee, P.; Ezani, Azadeh; Shifteh Some'e, B.

2012-07-01

78

Quantized linear ? model at finite temperature, and nucleon properties  

NASA Astrophysics Data System (ADS)

The nucleon properties due to the restoration of the chiral symmetry at nonzero temperature T are investigated within the framework of the linear ? model. The field equations are solved using the coherent-pair approximation. In this approach, the quantum fields are treated in a nonperturbative fashion. We minimize the expectation value of the chiral Hamiltonian using the ansatz of the coherent-pair ground-state configuration. The obtained results show that the nucleon mass and mean-square radius of the proton and the neutron increase monotonically with the temperature T and that the pion-nucleon coupling constant g?NN decreases with temperature values that are near the value of the critical temperature Tc. The nucleon mass and mean-square radius of the proton are examined in the (x,T) plane, showing a sensitive dependence on the coherence parameter x. This means that an increase of both the coherence parameter x and the temperature T leads to an increase in the values of the nucleon mass and the mean-square radius of the proton. This is evidence for the quark-gluon deconfinement phase transition.

Abu-Shady, M.; Mansour, H. M.

2012-05-01

79

Atlantic sea surface temperature trends and variability since 1552  

NASA Astrophysics Data System (ADS)

North Atlantic sea-surface temperature (SST) variability can have a near global impact on climate. Observed variability has been described as a natural multidecadal (65-100 year) oscillation superimposed upon a linearly-increasing, low frequency background warming. The multidecadal portion of this variability may be persistent, suggesting useful decadal climate predictions may soon be possible. However, our understanding of multidecadal Atlantic SST variability prior to the brief instrumental record relies almost exclusively on high latitude tree-ring proxies. No proxy SST reconstruction from the Atlantic itself has the resolution, dating accuracy and length needed to assess the behavior of multidecadal variability. We present the first absolutely dated and annually-resolved multi-centennial record of Atlantic sea surface temperature. Our 439- year coral-based reconstruction suggests western low-latitude Atlantic SSTs were nearly as warm as today from 1552-1570, cooled by more than 1 degree C from 1650-1730 and generally warmed to the present. Estimates of background variability suggest anthropogenic forcing can account for most of the warming since 1850. Multidecadal variations superimposed upon this background disappear prior to about 1730 in favor of interdecadal (15-20 year) variability. This suggests observed multidecadal variability is not persistent and may be difficult to predict.

Saenger, C.; Cohen, A. L.; Oppo, D. W.

2008-12-01

80

Effects of Temperature and Precipitation Variability on Snowpack Trends in the Western United States  

Microsoft Academic Search

Recent studies have shown substantial declines in snow water equivalent (SWE) over much of the western United States in the last half century, as well as trends toward earlier spring snowmelt and peak spring streamflows. These trends are influenced both by interannual and decadal-scale climate variability, and also by temperature trends at longer time scales that are generally consistent with

Alan F. Hamlet; Philip W. Mote; Martyn P. Clark; Dennis P. Lettenmaier

2005-01-01

81

Spatial differentiation of temperature extremes trends in Poland  

NASA Astrophysics Data System (ADS)

Extreme meteorological phenomena have been recently an important topic of discussion among both scientists and people in general. More and more often people are asking themselves what is going to happen in the nearest future and how the life is going to change due to the climate change and extreme weather phenomena that are taking place. The main objective of the research is to present the tendencies in air temperature extremes variability in Poland during the latest decades. Existing research on meteorological extremes occurrence proved that the country is characterized by the considerable spatial differentiation of extremes. Therefore the important scope of the study is also to analyze the spatial differentiation of tendencies in extreme values variability. The basic research material, maximum and minimum air temperature values, was based on the data from 54 meteorological stations relatively regular distributed all over the country. The data covers the period of 58 years from 1951 to 2008. Extremes evaluation required the source material to be thoroughly checked regarding homogeneity. Daily maximum and minimum temperature values were checked many times and in some cases data series were abandoned while the fully evaluation was not possible. The extremes were identified by the probability approach. To differentiate the extremes of the interest the following thresholds were applied: 10%, 5% and very rigorous criteria of 1% that is the 10th and 90th, 5th and 95th as well as 1st and 99th percentiles respectively. The data were analyzed regarding the long term variability of extreme values: minimum and maximum air temperature and the frequency of their occurrence within the period under examination. The analysis of particular extreme phenomena showed that they occurred at various moments from 1951 to 2008. Although many extremes were recorded in the latest two decades (since 1990), a considerable number of them have also been observed in the 1950s and 1960s. The obtained results show spatial differentiation of both extreme air temperature values and their long-term tendency. For "mild" extremes (distinguished with the mild criteria of 10th and 90th percentiles) winter minima showed the slight decreasing tendency over most of the area of Poland except for the North-East (approximately 1.2 day/10 years). Summer maxima demonstrated statistically significant positive trends in western Poland (the increase reaches about 1.5 day/10 years) whereas eastern part of the country is not characterized by any visible tendency in temperature extremes variability. In case of "sharp" extremes (p=1%) none statistically significant tendencies are observed. The analyses proved important local differences even in the scale of particular regions. It absolutely certifies that detailed and thorough data examination is necessary. The obtained results confirm also the local differentiation of climate conditions and subsequently the problem of representative character of the stations, especially those used in extreme meteorological phenomena research.

Ustrnul, Z.; Wypych, A.

2010-09-01

82

A Bivariate Time Series Approach to Anthropogenic Trend Detection in Hemispheric Mean Temperatures.  

NASA Astrophysics Data System (ADS)

A bivariate time series regression approach is used to model observed variations in hemispheric mean temperature over the period 1900-96. The regression equations include deterministic predictor variables and lagged values of the two predictands, and two different forms of this basic structure are employed. The deterministic predictors considered are simple linear trends, various climate model-generated time series based on different combinations of greenhouse gas, sulfate aerosol, and solar forcing, and the Southern Oscillation index (SOI). With linear trends as the only predictors, the best model is a fourth-order bivariate autoregressive model including lagged Southern Hemisphere (SH) to Northern Hemisphere (NH) dependence, as in previous work by Kaufmann and Stern. The estimated NH and SH trends are both +0.67°C century1, and both are highly statistically significant. If SOI is included as an additional predictor, however, a first-order time series model, with no SH to NH dependence, is an adequate fit to the data. This shows that SOI may be an important covariate in this kind of analysis. Further analysis uses climate model-generated forcing terms representing greenhouses gases, sulfate aerosols, and solar effects, as well as SOI. The statistical analysis makes extensive use of Bayes factors as a device for discriminating among a wide spectrum of possible models. The best fits to the data are obtained when all three forcing terms are included. Total sulfate aerosol forcing of 1.1 W m2 (with a corresponding climate sensitivity of T2× = 4.2°C) is preferred to 0.7 W m2 (with sensitivity of 2.3°C), but the Bayes factor discrimination between these cases is weak.

Smith, Richard L.; Wigley, Tom M. L.; Santer, Benjamin D.

2003-04-01

83

Interdecadal variability and linear trend of sea level along the Japanese coast  

NASA Astrophysics Data System (ADS)

Interdecadal variability and linear trend of sea level along the Japanese coast during the 20th century and their causes are investigated using tide gauge, altimeter, and ocean heat content data. We also examine those in the future climate projected by IPCC-AR4 CGCMs. Historical tide gauge data show that sea level along the Japanese coast has no significant trend during the 20th century. Rather, bidecadal variability and simultaneous variation along the Japanese coast are remarkable. In order to examine the causes of this sea level variability, OGCM experiments forced by the historical atmospheric reanalysis data have been conducted. The long-term variability of the sea level along the Japanese coast is mainly due to the baroclinic Rossby waves forced by changes in the large-scale wind stress fields in the North Pacific with a lag of several years. The bidecadal variability is caused primarily by the meridional shift of the boundary between the subtropical and subpolar gyres, which is forced by the shifting of the westerlies over the central North Pacific. Sea level along the Japanese coast has risen significantly since the mid-1980s. Although this is partly explained by the dynamical response to the wind stress fields, it can be considered that the global mean thermal expansion contributes considerably. On the sea level rise along the Japanese coast in the future climate, multi-model ensemble means indicate sea level change associated with the northward shift of the Kuroshio Extension. 18cm change in the east of Japan is comparable to global mean steric sea level rise. It remains large uncertainty in the atmospheric change over the midlatitude North Pacific associated with global warming. Therefore, it is important to reduce its uncertainty, in addition to evaluate other contributions such as ice sheet melting.

Yasuda, T.; Sueyoshi, M.

2010-12-01

84

Thick-Film Negative-Temperature-Coefficient Thermistors with a Linear Resistance-Temperature Relation  

NASA Astrophysics Data System (ADS)

The effect of the resistance R of Mn1.85Co0.3Ni0.85O4 (MCN) thick-film negative-temperature-coefficient (NTC) thermistors on temperature T is studied carefully. Interestingly, the R—T relation is found to be decided simultaneously by the characteristic of the MCN oxide and the electrode structure of the NTC thermistor. For plane end electrodes, the R—T relation is nonlinear. However, for plane fork electrodes, the R—T relation can be linear. To clarify the intrinsic mechanism of the linear R—T relation, the electric field distribution in the MCN thick film is simulated. The obtained results suggest that the non-uniform electric field distribution between the electrodes is responsible for the R—T relation linearization.

Ling, Zhi-Yuan; He, Lin

2013-10-01

85

Differences between near-surface equivalent temperature and temperature trends for the Eastern United States. Equivalent temperature as an alternative measure of heat content  

USGS Publications Warehouse

There is currently much attention being given to the observed increase in near-surface air temperatures during the last century. The proper investigation of heating trends, however, requires that we include surface heat content to monitor this aspect of the climate system. Changes in heat content of the Earth's climate are not fully described by temperature alone. Moist enthalpy or, alternatively, equivalent temperature, is more sensitive to surface vegetation properties than is air temperature and therefore more accurately depicts surface heating trends. The microclimates evident at many surface observation sites highlight the influence of land surface characteristics on local surface heating trends. Temperature and equivalent temperature trend differences from 1982-1997 are examined for surface sites in the Eastern U.S. Overall trend differences at the surface indicate equivalent temperature trends are relatively warmer than temperature trends in the Eastern U.S. Seasonally, equivalent temperature trends are relatively warmer than temperature trends in winter and are relatively cooler in the fall. These patterns, however, vary widely from site to site, so local microclimate is very important. ?? 2006 Elsevier B.V. All rights reserved.

Davey, C. A.; Pielke, Sr. , R. A.; Gallo, K. P.

2006-01-01

86

Incorporating Duplicate Genotype Data into Linear Trend Tests of Genetic Association: Methods and Cost-Effectiveness  

PubMed Central

The genome-wide association (GWA) study is an increasingly popular way to attempt to identify the causal variants in human disease. Duplicate genotyping (or re-genotyping) a portion of the samples in a GWA study is common, though it is typical for these data to be ignored in subsequent tests of genetic association. We demonstrate a method for including duplicate genotype data in linear trend tests of genetic association which yields increased power. We also consider the cost-effectiveness of collecting duplicate genotype data and find that when the relative cost of genotyping to phenotyping and sample acquisition costs is less than or equal to the genotyping error rate it is more powerful to duplicate genotype the entire sample instead of spending the same money to increase the sample size. Duplicate genotyping is particularly cost-effective when SNP minor allele frequencies are low. Practical advice for the implementation of duplicate genotyping is provided. Free software is provided to compute asymptotic and permutation based tests of association using duplicate genotype data as well as to aid in the duplicate genotyping design decision.

Borchers, Bryce; Brown, Marshall; McLellan, Brian; Bekmetjev, Airat; Tintle, Nathan L

2009-01-01

87

Climate reconstructions of the NH mean temperature: Can underestimation of trends and variability be avoided?  

NASA Astrophysics Data System (ADS)

Knowledge about the climate in the period before instrumental records are available is based on climate proxies obtained from tree-rings, sediments, ice-cores etc. Reconstructing the climate from such proxies is therefore necessary for studies of climate variability and for placing recent climate change into a longer term perspective. More than a decade ago pioneering attempts at using a multi-proxy dataset to reconstruct the Northern Hemisphere (NH) mean temperature resulted in the much published "hockey-stick"; a NH mean temperature that did not vary much before the rapid increase in the last century. Subsequent reconstructions show some differences but the overall "hockey-stick" structure seems to be a persistent feature However, there has been an increasing awareness of the fact that the applied reconstruction methods underestimate the low-frequency variability and trends. The recognition of the inadequacies of the reconstruction methods has to a large degree originated from pseudo-proxy studies, i.e., from long climate model experiments where artificial proxies have been generated and reconstructions based on these have been compared to the known model climate. It has also been found that reconstructions contain a large element of stochasticity which is revealed as broad distributions of skills. This means that it is very difficult to draw conclusions from a single or a few realizations. Climate reconstruction methods are based on variants of linear regression models relating temperatures and proxies. In this contribution we review some of the theory of linear regression and error-in-variables models to identify the sources of the underestimation of variability. Based on the gained insight we formulate a reconstruction method supposed to minimize this underestimation. The method is tested by applying it to an ensemble of surrogate temperature fields based on two climate simulations covering the last 500 and 1000 years. Compared to the RegEM TTLS method and a composite plus scale method - two methods recently used in the literature - the new method strongly improves the behavior regarding the low-frequency variability and trends. The potential importance in real world situations is demonstrated by implying the methods to a set of 14 decadal smoothed proxies. Here the new method shows much larger low-frequency variability and a much colder pre-industrial temperature level than the other reconstruction methods.

Christiansen, Bo

2010-05-01

88

An empirical technique for estimating near-surface air temperature trends in central Greenland from SSM/I brightness temperatures  

SciTech Connect

In central Greenland, near-surface air temperatures can be estimated from long-term satellite passive microwave brightness temperatures supported by limited air-temperature data from automatic weather stations. In this region, brightness temperature depends on snow emissivity, which varies slowly over time, and on snow temperature, which varies more rapidly and is controlled by air temperature. The air temperature and brightness temperature data define an emissivity trend which can be modeled as an annual sinusoid. An air temperature trend can then be derived from the brightness temperature and modeled emissivity information. The estimated air temperature values represent an integrated near-surface value that defines the overall temperature trend at the Greenland Summit. The modeled emissivity cycle allows daily-average air temperatures to be estimated across significant gaps in weather station records, as well as quality control of their temperature data. The technique also generates annual trends of emissivity which can be used to evaluate radiative transfer models of microwave emissivity from dry firn.

Shuman, C.A.; Alley, R.B.; Anandakrishnan, S. [Pennsylvania State Univ., University Park, PA (United States); Stearns, C.R. [Univ. of Wisconsin, Madison, WI (United States). Space Science and Engineering Center

1995-02-01

89

Trends of seasonal maximum and minimum temperatures and precipitation in Southern Brazil for the 1913-2006 period  

NASA Astrophysics Data System (ADS)

Long-term variations of monthly average maximum and minimum temperature (TMAX and TMIN) and precipitation records in southern Brazil are investigated for the 1913-2006 period. These variations are carefully analyzed for seasonal and annual indices, taken as regional averages. For this purpose, the serial correlation and trend of the indices are investigated using the run and Mann-Kendall tests. The significant trends are obtained from linear least-square fits. The annual and seasonal TMIN indices show significant warming trends with magnitudes (1.7°C per 100 years for annual index) comparable to those reported by the Intergovernmental Panel on Climate Change, but lower than those found for the southern Brazil in another previous work. Regarding the two other variables, the indices show significant trends only for summer, being a cooling trend of 0.6°C per 100 years for the TMAX and an increasing trend of 93 mm per 100 years over an average summer precipitation of 367 mm. Concerning the decadal analysis, the 1920s present the lowest annual, autumn, and spring TMIN and the 1990s, the highest ones. The 1970s is the decade with the lowest summer TMAX, and the 1940s the decade with the highest one. The driest decade is the 1940s and the wettest, the 1980s.

Sansigolo, Clóvis Angeli; Kayano, Mary Toshie

2010-07-01

90

Protists decrease in size linearly with temperature: ca. 2.5% degrees C(-1).  

PubMed

An inverse relationship between organism size and rearing temperature is widely observed in ectotherms ('the temperature-size rule', TSR). This has rarely been quantified for related taxa, and its applicability to protists also required testing. Here, we quantify the relationship between temperature and mean cell volume within the protists by a meta-analysis of published data covering marine, brackish water and freshwater autotrophs and heterotrophs. In each of 44 datasets, a linear relationship between temperature and size could not be rejected, and a negative trend was found in 32 cases (20 gave significant negative regressions, p < 0.05). By combining 65 datasets, we revealed, for each 1 degrees C increase, a cell-size reduction of 2.5% (95% CI of 1.7-3.3%) of the volume observed at 15 degrees C. The value did not differ across taxa (amoebae, ciliates, diatoms, dinoflagellates, flagellates), habitats, modes of nutrition or combinations of these. The data are consistent with two hypotheses that are capable of explaining the TSR in ectotherms generally: (i) resource, especially respiratory gas, limitation; and (ii) fitness gains from dividing earlier as population growth increases. Using the above relationship we show how changes in cell numbers with temperature can be estimated from changes in biomass and vice versa; ignoring this relationship would produce a systematic error. PMID:14728784

Atkinson, David; Ciotti, Benjamin J; Montagnes, David J S

2003-12-22

91

Protists decrease in size linearly with temperature: ca. 2.5% degrees C(-1).  

PubMed Central

An inverse relationship between organism size and rearing temperature is widely observed in ectotherms ('the temperature-size rule', TSR). This has rarely been quantified for related taxa, and its applicability to protists also required testing. Here, we quantify the relationship between temperature and mean cell volume within the protists by a meta-analysis of published data covering marine, brackish water and freshwater autotrophs and heterotrophs. In each of 44 datasets, a linear relationship between temperature and size could not be rejected, and a negative trend was found in 32 cases (20 gave significant negative regressions, p < 0.05). By combining 65 datasets, we revealed, for each 1 degrees C increase, a cell-size reduction of 2.5% (95% CI of 1.7-3.3%) of the volume observed at 15 degrees C. The value did not differ across taxa (amoebae, ciliates, diatoms, dinoflagellates, flagellates), habitats, modes of nutrition or combinations of these. The data are consistent with two hypotheses that are capable of explaining the TSR in ectotherms generally: (i) resource, especially respiratory gas, limitation; and (ii) fitness gains from dividing earlier as population growth increases. Using the above relationship we show how changes in cell numbers with temperature can be estimated from changes in biomass and vice versa; ignoring this relationship would produce a systematic error.

Atkinson, David; Ciotti, Benjamin J; Montagnes, David J S

2003-01-01

92

Highly linear very compact untrimmed on-chip temperature sensor with second and third order temperature compensation  

Microsoft Academic Search

This paper proposes a CMOS structure as a highly linear on-chip temperature sensor. As long as all transistors are in saturation, the output of the structure is a VDD independent voltage source that linearly expresses CMOS threshold voltage, and hence is approximately linear in temperature. A new sizing strategy is introduced following a combined analytical and numerical optimization approach, which

Jun He; Chen Zhao; Sheng-Huang Lee; Karl Peterson; Randall Geiger; Degang Chen

2010-01-01

93

Local and large-scale influences on Swiss temperature trends 1959-2008  

Microsoft Academic Search

Temperature is a key variable for monitoring global climate change. Here we perform a trend analysis of Swiss temperatures from 1959-2008, using a new 2x2 km gridded data set based on carefully homogenized ground observations from MeteoSwiss. The aim of this study is twofold: first, to discuss the spatial and altitudinal temperature trend characteristics in detail and second, to quantify

P. Ceppi; S. C. Scherrer; A. Fischer; C. Appenzeller

2010-01-01

94

Spatial and temporal patterns of trends and variability in diurnal temperature ranges of Turkey  

Microsoft Academic Search

Summary Spatial and temporal patterns of trends in the diurnal temperature ranges ( DTRs) of the 70 stations and the role of maximum and minimum temperatures on the year-to-year variability and the long-term trends of the DTRs in Turkey have been investigated for the period 1929–1999. The principal results of the study are as follows: (i) The daytime maximum temperatures

M. Türkes; U. M. Sümer

2004-01-01

95

Chemistry-climate model simulations of recent trends in lower stratospheric temperature and stratospheric residual circulation  

NASA Astrophysics Data System (ADS)

Observations of the lower stratospheric temperature over the last three decades show seasonal variations in tropical trends together with spatial patterns in southern high latitude trends in late winter-spring, with regions of cooling and warming of comparable magnitude. Neither aspect is reproduced in climate models used in the Intergovernmental Panel on Climate Change's Fourth Assessment Report (IPCC AR4). Here we show that stratosphere-resolving chemistry-climate models can produce these aspects of temperature trends. However, the seasonality of temperature trends can vary greatly among simulations of the same model, and even if one ensemble member reproduces the observed seasonality in trends there may be little agreement with observations for another member. The variability in trends among model ensemble members is related to differences in trends in wave activity propagating into the stratosphere. These results suggest that the seasonality of the observed temperature trends could be the result of natural variability as well as, or instead of, a response to external forcing, and that comparison with these trends may not be a robust test of climate models.

Wang, Lei; Waugh, Darryn W.

2012-05-01

96

Trend analysis of rainfall and temperature and its relationship over India  

NASA Astrophysics Data System (ADS)

This study investigated the trends in rainfall and temperature and the possibility of any rational relationship between the trends over the homogeneous regions over India. Annual maximum temperature shows an increasing trend in all the homogeneous temperature regions and corresponding annual rainfall also follow the same pattern in all the regions, except North East. As far as monthly analysis is concerned, no definite pattern has been observed between trends in maximum and minimum temperature and rainfall, except during October. Increasing trends of maximum and minimum temperature during October accelerate the water vapor demand and most of the lakes, rivers, ponds and other water bodies with no limitation of water availability during this time fulfills the water vapor demand and shows an increasing trend of rainfall activity. This study shows there exists no direct relationship between increasing rainfall and increasing maximum temperature when monthly or seasonal pattern is concerned over meteorological subdivisions of India, however we can make a conclusion that the relation between the trends of rainfall and temperature have large scale spatial and temporal dependence.

Subash, N.; Sikka, A. K.

2013-10-01

97

Global crop exposure to critical high temperatures in the reproductive period: historical trends and future projections  

NASA Astrophysics Data System (ADS)

Long-term warming trends across the globe have shifted the distribution of temperature variability, such that what was once classified as extreme heat relative to local mean conditions has become more common. This is also true for agricultural regions, where exposure to extreme heat, particularly during key growth phases such as the reproductive period, can severely damage crop production in ways that are not captured by most crop models. Here, we analyze exposure of crops to physiologically critical temperatures in the reproductive stage (Tcrit), across the global harvested areas of maize, rice, soybean and wheat. Trends for the 1980–2011 period show a relatively weak correspondence (r = 0.19) between mean growing season temperature and Tcrit exposure trends, emphasizing the importance of separate analyses for Tcrit. Increasing Tcrit exposure in the past few decades is apparent for wheat in Central and South Asia and South America, and for maize in many diverse locations across the globe. Maize had the highest percentage (15%) of global harvested area exposed to at least five reproductive days over Tcrit in the 2000s, although this value is somewhat sensitive to the exact temperature used for the threshold. While there was relatively little sustained exposure to reproductive days over Tcrit for the other crops in the past few decades, all show increases with future warming. Using projections from climate models we estimate that by the 2030s, 31, 16, and 11% respectively of maize, rice, and wheat global harvested area will be exposed to at least five reproductive days over Tcrit in a typical year, with soybean much less affected. Both maize and rice exhibit non-linear increases with time, with total area exposed for rice projected to grow from 8% in the 2000s to 27% by the 2050s, and maize from 15 to 44% over the same period. While faster development should lead to earlier flowering, which would reduce reproductive extreme heat exposure for wheat on a global basis, this would have little impact for the other crops. Therefore, regardless of the impact of other global change factors (such as increasing atmospheric CO2), reproductive extreme heat exposure will pose risks for global crop production without adaptive measures such as changes in sowing dates, crop and variety switching, expansion of irrigation, and agricultural expansion into cooler areas.

Gourdji, Sharon M.; Sibley, Adam M.; Lobell, David B.

2013-06-01

98

Seasonal variation of trend in temperature and ozone over the tropical stratosphere in the Northern Hemisphere  

NASA Astrophysics Data System (ADS)

Temperature and ozone trends in the stratosphere are investigated using Halogen Occultation Experiment (HALOE) aboard Upper Atmospheric Research Satellite (UARS) observations for the period 1992 2004, over the tropics of Northern Hemisphere (0 30°N). The regression analysis of temperature time series indicates a significant annual cooling trend of 1 3 K/decade in the free stratosphere. A cooling trend of ˜2±0.6 K/decade near 25 km which increases with altitude to reach a maximum around 35 km and then decreases to 1±1.1 K/decade near stratopause is computed. The observed maximum cooling trend near 35 km may be viewed with caution due to the change over of temperature from National Centre for Environmental Prediction (NCEP) reanalysis data to HALOE instrument. A statistically significant decreasing ozone trend in the lower stratosphere is also obtained which becomes negligible above 40 km. Attempt has been made to compute the seasonal trend components in both temperature and ozone. Seasonal distribution of temperature trends shows a maximum cooling during winter. The largest negative ozone trend is found during autumn with a peak (8 10% per decade) near 30 km.

Fadnavis, S.; Beig, G.

2006-12-01

99

Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends.  

PubMed

From 1979 to 2001, temperatures observed globally by the mid-tropospheric channel of the satellite-borne Microwave Sounding Unit (MSU channel 2), as well as the inferred temperatures in the lower troposphere, show only small warming trends of less than 0.1 K per decade (refs 1-3). Surface temperatures based on in situ observations however, exhibit a larger warming of approximately 0.17 K per decade (refs 4, 5), and global climate models forced by combined anthropogenic and natural factors project an increase in tropospheric temperatures that is somewhat larger than the surface temperature increase. Here we show that trends in MSU channel 2 temperatures are weak because the instrument partly records stratospheric temperatures whose large cooling trend offsets the contributions of tropospheric warming. We quantify the stratospheric contribution to MSU channel 2 temperatures using MSU channel 4, which records only stratospheric temperatures. The resulting trend of reconstructed tropospheric temperatures from satellite data is physically consistent with the observed surface temperature trend. For the tropics, the tropospheric warming is approximately 1.6 times the surface warming, as expected for a moist adiabatic lapse rate. PMID:15129277

Fu, Qiang; Johanson, Celeste M; Warren, Stephen G; Seidel, Dian J

2004-05-01

100

Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends  

NASA Astrophysics Data System (ADS)

From 1979 to 2001, temperatures observed globally by the mid-tropospheric channel of the satellite-borne Microwave Sounding Unit (MSU channel 2), as well as the inferred temperatures in the lower troposphere, show only small warming trends of less than 0.1K per decade (refs 1-3). Surface temperatures based on in situ observations however, exhibit a larger warming of ~0.17K per decade (refs 4, 5), and global climate models forced by combined anthropogenic and natural factors project an increase in tropospheric temperatures that is somewhat larger than the surface temperature increase. Here we show that trends in MSU channel 2 temperatures are weak because the instrument partly records stratospheric temperatures whose large cooling trend offsets the contributions of tropospheric warming. We quantify the stratospheric contribution to MSU channel 2 temperatures using MSU channel 4, which records only stratospheric temperatures. The resulting trend of reconstructed tropospheric temperatures from satellite data is physically consistent with the observed surface temperature trend. For the tropics, the tropospheric warming is ~1.6 times the surface warming, as expected for a moist adiabatic lapse rate.

Fu, Qiang; Johanson, Celeste M.; Warren, Stephen G.; Seidel, Dian J.

2004-05-01

101

Recent and future sea surface temperature trends in tropical pacific warm pool and cold tongue regions  

Microsoft Academic Search

Using coral data, sea surface temperature (SST) reanalysis data, and Climate Model Intercomparison Project III (CMIP3) data,\\u000a we analyze 20th-century and future warm pool and cold tongue SST trends. For the last 100 years, a broad La Nina-like SST\\u000a trend, in which the warming trend of the warm pool SST is greater than that of the cold tongue SST, has appeared

Soon-Il An; Ji-Won Kim; Seul-Hee Im; Beak-Min Kim; Jae-Heung Park

2011-01-01

102

Recent variability and trends of Antarctic near-surface temperature  

Microsoft Academic Search

A new monthly 1° × 1° Antarctic near-surface temperature reconstruction for 1960–2005 is presented. The use of numerical model fields to establish spatial relationships between fifteen continuous observational temperature records and the voids to which they are interpolated inherently accounts for the effects of the atmospheric circulation and topography on temperature variability. Employing a fixed observation network ensures that the

Andrew J. Monaghan; David H. Bromwich; William Chapman; Josefino C. Comiso

2008-01-01

103

Recent trends in mean maximum and minimum air temperatures over Spain (1961-2006)  

NASA Astrophysics Data System (ADS)

This study analyzes the mean maximum and minimum temperature trends on a monthly, seasonal, and annual timescale by applying various statistical tools to data from 476 Spanish weather stations during the period between 1961 and 2006. The magnitude of the trends was derived from the slopes of the regression lines using the least squares method, and the nonparametric Mann-Kendall test was used to determine the statistical significance of the trends. Temperature significantly increased in over 60% of the country in March, June, spring, and summer in the case of maximum temperatures and in March, May, June, August, spring, and summer for minimum temperatures. At the annual resolution, temperatures significantly increased in over 90% of Spain with a rise of around 0.3°C/decade. The maximum temperature increased at a higher rate than the minimum temperature from midsummer to early winter as well as in winter, spring, and summer and also on an annual basis.

del Río, S.; Cano-Ortiz, A.; Herrero, L.; Penas, A.

2012-08-01

104

Oceanic Climate Change: Contributions of Heat Content, Temperature, and Salinity Trends to Global Warming  

Microsoft Academic Search

The World Ocean is the largest component of the global climate system, and changes to its heat content, temperature, and salinity have an enormous impact on the current global warming trend. In this paper, these physical changes are discussed in detail, including potential sources of change and spatial and temporal variability, as the observed trends are influenced by location as

Christopher M. Mirabito

105

Critically Reassessing Tropospheric Temperature Trends from Radiosondes Using Realistic Validation Experiments  

Microsoft Academic Search

Biases and uncertainties in large-scale radiosonde temperature trends in the troposphere are critically reassessed. Realistic validation experiments are performed on an automatic radiosonde homogenization system by applying it to climate model data with four distinct sets of simulated breakpoint profiles. Knowl- edge of the ''truth'' permits a critical assessment of the ability of the system to recover the large-scale trends

Holly A. Titchner; P. W. Thorne; M. P. McCarthy; S. F. B. Tett; L. Haimberger; D. E. Parker

2009-01-01

106

On the estimation of external trends in minimum, maximum and mean temperature records over China  

NASA Astrophysics Data System (ADS)

We consider minimum, maximum, and mean temperature records at 112 station in China and use a recent scaling approach by [Lennartz and Bunde, 2011] to estimate the minimum external trend over the past 50 years, for confidence probabilities 0.95 and 0.99. We find that the minimum temperatures, in contrast to the maximum temperatures, show a significant trend for almost all considered stations. We also study the trend as a function of the population (in 2008) and of the population increase in the past 50 years. We find a significant increase in the trend of the minimum temperature at stations with a large population increase, which suggests that part of the recent warming may be due to urban heat islands.

Yuan, N.; Bunde, A.; Fu, Z.

2012-04-01

107

Global Trends in Lake Surface Temperatures Estimated from Multisensor Thermal Infrared Imagery  

Microsoft Academic Search

The temperatures of lakes and reservoirs worldwide are an excellent indicator of climatic change. Consistent, long-term in situ observations of lake surface temperature are very rare on a global scale, however the existing 30-year archive of thermal infrared imagery can be used to infer accurate and homogeneous time series of water surface temperature and associated trends for lakes and reservoirs

P. Schneider; S. J. Hook

2010-01-01

108

Long Term MSU Tropospheric and Ground Temperature Trends (1979-2008) Over Africa  

NASA Astrophysics Data System (ADS)

Africa, the second largest and second most populous continent, is marked by an arid desert zone in the north (10°-40°N), dense forest and tropical climate in the central region (10°S to 10°N), and a southern temperate zone (10°-40°S). The African landmass, which is symmetrically distributed across the equator, shows differential heating and cooling atmospheric (lower- and mid-tropospheric) temperature trends. The northern arid region, a main source of major dust storms and mineral dust aerosols, shows a larger warming trend compared to the central region characterized by dense forest and forest fires. The mean annual lower- and mid-tropospheric temperature trend (Microwave Sounding Units MSU, 1979-2008) is found be 0.023±0.006 °K/year and 0.018±0.003 °K/year respectively over northern Africa (Saharan region) as compared to 0.010±0.003 °K/year and 0.009±0.002 °K/year over the central equatorial, and mostly forest-covered region (Figure 1). The southern region shows a mean annual lower- and mid-tropospheric temperature trend of 0.015±0.004 °K/year and 0.011±0.003 °K/year, which is lower than the desert region. The dense tropical forest region near the equator shows the lowest tropospheric temperature trend (lower: 0.011±0.003 °K/year; mid: 0.007±0.002 °K/year) over the Africa (Figure 1). The warmest temperature trend was observed over the eastern Saharan region, covering parts of Egypt, Libya, and the northern parts of Sudan, Chad and Niger. We have also compared the MSU-derived atmospheric temperature trends to ground-based temperature trends available for Egypt and some surrounding regions. The mean annual MSU tropospheric trends over the Saharan region are relatively low compared to other major Asian deserts, such as the Taklamakan and the Gobi Desert in the northern mid-latitudes, which show a trend of 0.037±0.008 °K/year (lower) and 0.025±0.006 °K/year (mid). The seasonal and month-to-month variability of temperature trends over Africa and their comparison with other parts of the world will be discussed in detail. Figure 1. Long-term (30 years) mean annual MSU-derived tropospheric temperature trend (°K/year) over the African Continent.

Prasad, A. K.; El-Askary, H.; Kafatos, M.

2009-12-01

109

Recent land surface air temperature trends assessed using the 20th Century Reanalysis  

Microsoft Academic Search

Land surface air temperature trends observed during 1979-2008 are compared with those simulated by the 20th Century Reanalysis that is driven only by observed sea surface temperatures and sea ice, atmospheric CO2 concentrations, solar and volcanic forcings, and surface pressure data. On a global annual average, the 20th Century Reanalysis simulates a little more than 80% of the observed trend,

David E. Parker

2011-01-01

110

Nanoscale CMOS at low temperature: design, reliability, and scaling trend  

Microsoft Academic Search

The semiconductor industry is not motivated to make practical use of cryogenic operation as long as IC performance could be improved at room temperature. However, as CMOS approaches the scaling limits, cooled chip operation becomes an attractive alternative. This paper explores the feasibility of IC temperature \\

Bin Yu; Haihong Wang; C. Riccobene; Hyeon-Seag Kim; Qi Xiang; Ming-Ren Lin; Leland Chang; Chenming Hu

2001-01-01

111

A spatiotemporal analysis of U.S. station temperature trends over the last century  

NASA Astrophysics Data System (ADS)

This study presents a nonlinear spatiotemporal analysis of 1167 station temperature records from the United States Historical Climatology Network covering the period from 1898 through 2008. We use the empirical mode decomposition method to extract the generally nonlinear trends of each station. The statistical significance of each trend is assessed against three null models of the background climate variability, represented by stochastic processes of increasing temporal correlation length. We find strong evidence that more than 50% of all stations experienced a significant trend over the last century with respect to all three null models. A spatiotemporal analysis reveals a significant cooling trend in the South-East and significant warming trends in the rest of the contiguous U.S. It also shows that the warming trend appears to have migrated equatorward. This shows the complex spatiotemporal evolution of climate change at local scales.

Capparelli, V.; Franzke, C.; Vecchio, A.; Freeman, M. P.; Watkins, N. W.; Carbone, V.

2013-07-01

112

On the temperature dependence of the linear optical response of bulk GaAs  

Microsoft Academic Search

Linear optical probes are widely used to monitor various physical properties of semiconductor surfaces and overlayers in chemically active environments such as MOVPE, MBE, etc., over a wide temperature range. However, the traditional optical calculations used to interpret the data are strictly valid only at zero temperature. We propose to take into account the temperature dependence of the linear optical

A. Shkrebtii; W. Richter; M. J. G. Lee; T. Zettler; T. Trepk

2004-01-01

113

Ground vs. surface air temperature trends: Implications for borehole surface temperature reconstructions  

NASA Astrophysics Data System (ADS)

We have analyzed the relationship between surface air temperature (SAT), ground surface temperature (GST), and snow cover (SNC) over the terrestrial Northern Hemisphere based on general circulation model (GCM) simulations using GISS modelE forced with the observed SST and radiative forcing changes from 1951-1998. While SAT is the dominant influence on GST during the warm-season, it explains only half of the variance in GST during the cold-season, with SNC and pre-conditioning by prior warm-season SAT also exhibiting a sizeable and, in places, dominant influence. During a period of coincident surface warming and cold-season snowcover decrease in the model (1971-1998), mean GST increases are 0.2°C less than those in SAT, a consequence of greater exposure of the ground surface to winter cold air outbreaks. Interpretations of past SAT trends from borehole-based GST reconstructions may therefore be substantially biased by seasonal influences and snow cover changes.

Mann, Michael E.; Schmidt, Gavin A.

2003-06-01

114

Probable causes of late twentieth century tropospheric temperature trends  

Microsoft Academic Search

We assess the most probable causes of late twentieth century (1960–1994) tropospheric temperature changes. Optimal detection techniques are used to compare observed spatio-temporal patterns of near-surface and tropospheric temperature change with results from experiments performed with two different versions of the Hadley Centre climate model. We detect anthropogenic forcings, particularly well-mixed greenhouse-gases, with a less certain sulfate aerosol cooling influence.

P. W. Thorne; P. D. Jones; S. F. B. Tett; M. R. Allen; D. E. Parker; P. A. Stott; G. S. Jones; T. J. Osborn; T. D. Davies

2003-01-01

115

Recent trends in daily temperature extremes over southern Montenegro (1951-2010)  

NASA Astrophysics Data System (ADS)

Montenegro so far has been poorly investigated in terms of climate extremes. The aim of this paper was to analyse the extreme ETCCD temperature indices in the Mediterranean region of Montenegro for the period of 1951-2010. Four stations in the coastal area of Montenegro have been analysed: Herceg Novi, Ulcinj, Budva and Bar. Two periods (before 1980 and after 1980) were separately investigated in this study due to a well known climate shift that occurred in the late 1970's. Seven indices of temperature extremes have been chosen. The trend was analysed using a Man-Kendall non parametric test while the slope was estimated using Sen's slope estimator. A negative trend has been calculated for cold nights and cold days at almost all stations. The most significant positive trends were obtained for warm conditions. Two separately investigated periods have shown contrasting temperature trends.

Buri?, D.; Lukovi?, J.; Duci?, V.; Dragojlovi?, J.; Doderovi?, M.

2013-10-01

116

Uncertainty of AMSU-A derived temperature trends in relationship with clouds and precipitation over ocean  

NASA Astrophysics Data System (ADS)

Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit-A (AMSU-A) observations from a series of National Oceanic and Atmospheric Administration satellites have been extensively utilized for estimating the atmospheric temperature trend. For a given atmospheric temperature condition, the emission and scattering of clouds and precipitation modulate MSU and AMSU-A brightness temperatures. In this study, the effects of the radiation from clouds and precipitation on AMSU-A derived atmospheric temperature trend are assessed using the information from AMSU-A window channels. It is shown that the global mean temperature in the low and middle troposphere has a larger warming rate (about 20-30 % higher) when the cloud-affected radiances are removed from AMSU-A data. It is also shown that the inclusion of cloud-affected radiances in the trend analysis can significantly offset the stratospheric cooling represented by AMSU-A channel 9 over the middle and high latitudes of Northern Hemisphere.

Weng, F.; Zou, X.; Qin, Z.

2013-10-01

117

Application of geometric algorithm of time-temperature superposition to linear viscoelasticity of rubber compounds  

NASA Astrophysics Data System (ADS)

We tested usefulness of a new algorithm of time-temperature superposition to linear viscoelasticity of three kinds of rubber compounds which are conventional in rubber industries. Different from viscoelastic fluids, linear viscoelasticity of rubber compounds are usually measured by temperature-sweep test at fixed frequencies. We converted the viscoelastic data as functions of temperature to those as functions of frequency. We also investigated effect of rubber structures on their linear viscoelasticity.

Bae, Jung-Eun; Cho, Kwang Soo; Seo, Kwan Ho; Kang, Dong-Gug

2011-06-01

118

Changing trends of daily temperature extremes with different intensities in China  

NASA Astrophysics Data System (ADS)

By comparing two sets of quality-controlled daily temperature observation data with and without the inhomogeneity test and adjustment from 654 stations in China during 1956-2004 and 1956-2010, impacts of inhomogeneity on changing trends of four percentile temperature extreme indices, including occurrences of cold days, cold nights, warm days, and warm nights with varying intensities, were discussed. It is found that the inhomogeneity affected the long-term trends averaged over extensive regions limitedly. In order to minimize the inhomogeneity impact, the 83 stations identified with obvious inhomogeneity impacts were removed, and an updated analysis of changing trends of the four temperature extreme indices with varying intensities during 1956-2010 was conducted. The results show that annual occurrences of both cold nights and cold days decreased greatly while those of warm nights and warm days increased significantly during the recent 20 years. The more extreme the event is, the greater the magnitude of changing trends for the temperature extreme index is. An obvious increasing trend was observed in annual occurrences of cold days and cold nights in the recent four years. The magnitude of changing trends of warm extreme indices was greater than that of cold extreme indices, and it was greater in northern China than in southern China. Trends for summer occurrence of cold days were not significant. Decreasing trends of occurrences of both cold nights and cold days were the greatest in December, January, and February (DJF) but the least in June, July, and August (JJA), while increasing trends of warm nights were the greatest in JJA. Cold nights significantly decreased from 1956 to 1990, and then the decreasing trend considerably weakened. The decreasing trend also showed an obvious slowdown in recent years for occurrence of cold days. However, increasing trends of warm nights and warm days both have been accelerated continuously since the recent decades. Further analysis presents that the evolution of the trends for occurrences of the four temperature extreme indices was dominated by the changes in northern China.

Wang, Zunya; Ding, Yihui; Zhang, Qiang; Song, Yafang

2012-08-01

119

Sea Surface Temperature Trends of the Gulf Stream  

NSDL National Science Digital Library

One of the most studied and important ocean currents of the world lies along the eastern coast of the United States and is called the Gulf Stream. It derives its name from its source region of warm water in the Gulf of Mexico. For the past two decades, scientists have been collecting sea surface temperature (SST) data from satellites, buoys and ships in the Gulf Stream and Atlantic Basin. In this three-part lesson, students will explore the Live Access Server (LAS) and produce plots of sea surface temperature. They then prepare a time series of data for particular location(s) on the Gulf Stream and use Excel to produce and analyze graphs of sea surface temperature. The lesson provides detailed procedure, related links, sample graphs, follow-up questions, extensions, and teacher notes.

2006-10-31

120

External Resource: Surface Air Temperature Trends of the Caribbean  

NSDL National Science Digital Library

This activity allows learners/students to use real satellite data to determine the changes in near-surface air temperature at different times of the year over the Caribbean Sea. Upon completion of the activity, learners should be able to state how Earth's

1900-01-01

121

Trends in high temperature alloys: selection and manufacture  

Microsoft Academic Search

Guidelines for making a wise choice when selecting high temperature alloys are provided. Four groups of alloys are discussed, along with helpful selection criteria. Substantial benefits accrue from contemporary alloy manufacturing techniques. Process databases and state-of-the-art forging equipment significantly impact product quality, consistency and cost effectiveness. Finally, the author suggests that the elimination of unnecessary test requirements offers potential for

Kurt P. Rohrbach

1998-01-01

122

Understanding the trend in the Curie temperatures of Co{sub 2}-based Heusler compounds: Ab initio calculations  

SciTech Connect

The Curie temperatures for the Heusler compounds Co{sub 2}TiAl, Co{sub 2}VGa, Co{sub 2}VSn, Co{sub 2}CrGa, Co{sub 2}CrAl, Co{sub 2}MnAl, Co{sub 2}MnSn, Co{sub 2}MnSi, and Co{sub 2}FeSi are determined ab initio from the electronic structure obtained with the local-density functional approximation and/or the generalized gradient approximation. Frozen spin spirals are used to model the excited states needed to evaluate the spherical approximation for the Curie temperature. The spherical approximation is found to describe the experimental Curie temperatures very well which, for the compounds selected, extend over the range from 95 to 1100 K; as a function of the valence electron count, they show an approximately linear trend which finds an explanation by our calculations.

Kuebler, J.; Fecher, G. H.; Felser, C. [Institut fuer Festkoerperphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Institut fuer Anorganische und Analytische Chemie, Johannes Gutenberg-Universitaet, D-55128 Mainz (Germany)

2007-07-01

123

Effect of data homogenization on estimate of temperature trend: a case of Huairou station in Beijing Municipality  

NASA Astrophysics Data System (ADS)

Daily minimum temperature (Tmin) and maximum temperature (Tmax) data of Huairou station in Beijing from 1960 to 2008 are examined and adjusted for inhomogeneities by applying the data of two nearby reference stations. Urban effects on the linear trends of the original and adjusted temperature series are estimated and compared. Results show that relocations of station cause obvious discontinuities in the data series, and one of the discontinuities for Tmin are highly significant when the station was moved from downtown to suburb in 1996. The daily Tmin and Tmax data are adjusted for the inhomogeneities. The mean annual Tmin and Tmax at Huairou station drop by 1.377°C and 0.271°C respectively after homogenization. The adjustments for Tmin are larger than those for Tmax, especially in winter, and the seasonal differences of the adjustments are generally more obvious for Tmin than for Tmax. Urban effects on annual mean Tmin and Tmax trends are -0.004°C/10 year and -0.035°C/10 year respectively for the original data, but they increase to 0.388°C/10 year and 0.096°C/10 year respectively for the adjusted data. The increase is more significant for the annual mean Tmin series. Urban contributions to the overall trends of annual mean Tmin and Tmax reach 100% and 28.8% respectively for the adjusted data. Our analysis shows that data homogenization for the stations moved from downtowns to suburbs can lead to a significant overestimate of rising trends of surface air temperature, and this necessitates a careful evaluation and adjustment for urban biases before the data are applied in analyses of local and regional climate change.

Zhang, Lei; Ren, Guo-Yu; Ren, Yu-Yu; Zhang, Ai-Ying; Chu, Zi-Ying; Zhou, Ya-Qing

2013-04-01

124

The paradox of cooling streams in a warming world: Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States  

NASA Astrophysics Data System (ADS)

Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream temperature. Here, we examined the evidence for this using long-term stream temperature data from minimally and highly human-impacted sites located across the Pacific continental United States. Based on hypothesized climate impacts, we predicted that we should find warming trends in the maximum, mean and minimum temperatures, as well as increasing variability over time. These predictions were not fully realized. Warming trends were most prevalent in a small subset of locations with longer time series beginning in the 1950s. More recent series of observations (1987-2009) exhibited fewer warming trends and more cooling trends in both minimally and highly human-influenced systems. Trends in variability were much less evident, regardless of the length of time series. Based on these findings, we conclude that our perspective of climate impacts on stream temperatures is clouded considerably by a lack of long-term data on minimally impacted streams, and biased spatio-temporal representation of existing time series. Overall our results highlight the need to develop more mechanistic, process-based understanding of linkages between climate change, other human impacts and stream temperature, and to deploy sensor networks that will provide better information on trends in stream temperatures in the future.

Arismendi, Ivan; Johnson, Sherri L.; Dunham, Jason B.; Haggerty, Roy; Hockman-Wert, David

2012-05-01

125

Spatial Variability of Temperature Trends in Urbanized and Urbanizing Areas of North Carolina  

Microsoft Academic Search

This paper investigates the differences in temperature trends during a 40-year period in urbanized and urbanizing areas in North Carolina. Urbanized sites are in the urban cores of the selected regions; urbanizing sites are in outlying suburban locations characterized by lower devel- opment intensities than their respective urban cores. We examined maximum and minimum temperatures for four seasons represented by

Jason Ortegren; Zhi-Jun Liu; G. J. Lennartson

126

Monitoring sea level and sea surface temperature trends from ERS satellites  

Microsoft Academic Search

Data from the two ESA satellites ERS-1 and ERS-2 are used in global and regional analysis of sea level and sea surface temperature trends over the last 7.8 years. The ERS satellites and in the future the ENVISAT satellite provide unique opportunity for monitoring both changes in sea level and sea surface temperature as these satellites are equipped with an

Ole B Andersen; Per Knudsen; Brian Beckley

2002-01-01

127

Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection  

Microsoft Academic Search

The tropical lower stratosphere is an important region of the atmosphere, where strong convective activity in the underlying troposphere affects both its chemical and dynamical properties. Temperatures near the tropopause influence the input of water vapor from the troposphere and act as an indicator of the dynamical properties of the region. This paper addresses long-term trends in the temperature of

Karen H. Rosenlof; George C. Reid

2008-01-01

128

Recent temperature trends at mountain stations on the southern slope of the central Himalayas  

NASA Astrophysics Data System (ADS)

Insufficient long-term in situ observations and complex topographic conditions pose major problems in quantifying the magnitude of climatic trends in mountainous regions such as Nepal. Presented here is three decades (1980-2009) of data on annual maximum, minimum and average temperature trends from 13 mountain stations on the southern slope of the central Himalayas. The stations are located at elevations between 1304 and 2566 m above sea level and with varied topography. Spatial analyses of the average temperature trend show warming in most of the stations. The magnitude of warming is higher for maximum temperatures, while minimum temperatures exhibit larger variability such as positive, negative or no change. These results are consistent with patterns reported in some parts of the Indian subcontinent and Upper Indus Basin, but different from conditions on the Tibetan Plateau (China), where the warming of minimum temperatures is more prominent than that of the maximum temperatures. From the temporal variations, a dramatic increase in temperature is observed in the latest decade, particularly in the average and maximum temperatures. The results from the cumulative sum chart analyses suggest that the thermal regime shifted in 1997. The dramatic enhancement of average temperature in the last decade is strongly consistent with the result of contemporary studies of the surrounding regions, where warming is attributed to an increase in anthropogenic greenhouse gases. However, as in the western Himalayas and the Upper Indus Basin, the mountain stations on the southern slope of the central Himalayas show variability in temperature trends, particularly for the minimum temperature. This inhomogeneous trend is likely ascribed to the differences in topography and microclimatic regime of the observed stations.

Kattel, Dambaru Ballab; Yao, Tandong

2013-02-01

129

Curie temperature trends in (III,Mn)V ferromagnetic semiconductors  

Microsoft Academic Search

We present a theoretical survey of ferromagnetic transition temperatures in cubic (III,Mn)V semiconductors based on a model with S=5\\/2 local moments exchange coupled to itinerant holes in the host semiconductor valence band. Starting from the simplest mean-field theory of this model, we estimate the Tc enhancement due to exchange and correlation in the itinerant-hole system and the Tc suppression due

T. Jungwirth; Jürgen König; Jairo Sinova; J. Kucera; A. H. MacDonald

2002-01-01

130

Pb Isotope Systematics in Oceanic Island Basalts: What do Linear Pb-Pb Trends Tell us About the Plume Source?  

NASA Astrophysics Data System (ADS)

Together with the triple-spike TIMS technique, the advent of MC-ICP-MS and the possibility of correcting Pb isotope fractionation by addition of Tl as an external standard now allow for Pb isotopic ratio (206Pb/204Pb, 207Pb/204Pb, ^{208}Pb/204Pb) precision in the 100-200 ppm range. In the case of oceanic island basalts, achieving such levels of reproducibility also requires thorough preliminary leaching of the basalts before chemical separation. New results on carefully selected samples of basalt from two major mantle plume systems, Hawaii in the Pacific Ocean and Kerguelen in the Indian Ocean, yield linear trends in Pb-Pb isotope diagrams. These trends imply the existence of a minimum of two (Hawaii) or three (Kerguelen) components in the sources of these basalts. Both Pb isotope MC-ICP-MS datasets are now statistically significant (n=325 in Hawaii and n=150 in Kerguelen), which allows for the application of PCA and for more quantitative use of the results. Comparison of the Pb systematics in these two oceanic islands indicates that the existence of these linear trends, resulting from the presence of heterogeneities in the plume sources, is likely a characteristic of the extent/depth of melting. In Hawaii, Pb isotope trends in tholeiitic basalts do not allow for the presence of a depleted component, contrary to what is observed in Kerguelen. There is a significant difference between Mauna Loa and Mauna Kea basalts, in addition to a bilateral asymmetry of the plume source reflected by distinctly higher ^{208}Pb/204Pb for a given 206Pb/204Pb value in the Loa basalts. Parallel linear Pb-Pb trends are systematically present in volcanoes from the Mauna Kea trend, but they are very rare in Mauna Loa basalts, except in young radial vents. This might indicate that the Mauna Loa plume source is more thoroughly mixed than the Mauna Kea source, or simply that the Mauna Kea source has retained more heterogeneities at the periphery of the plume. A larger magma capture zone or larger degrees of partial melting would obliterate the compositional effects of these heterogeneities. These observations are consistent with the positive correlation between He isotopes and ^{208}Pb^{*}/206Pb^{*}, as well as with the larger magma production rate of the Mauna Loa volcano.

Weis, D.; Rhodes, J. M.; Garcia, M. O.

2006-12-01

131

Temporal Homogenization of Monthly Radiosonde Temperature Data. Part II: Trends, Sensitivities, and MSU Comparison  

Microsoft Academic Search

Trends in radiosonde-based temperatures and lower-tropospheric lapse rates are presented for the time periods 1959-97 and 1979-97, including their vertical, horizontal, and seasonal variations. A novel aspect is that estimates are made globally of the effects of artificial (instrumental or procedural) changes on the derived trends using data homogenization procedures introduced in a companion paper (Part I). Credibility of the

John R. Lanzante; Stephen A. Klein; Dian J. Seidel

2003-01-01

132

Late 20th Century Temperature Trends in the NARCCAP Regional Model Simulations  

Microsoft Academic Search

In this study we will analyze simulations from the North American Regional Climate Change Assessment Program (NARCCAP) in terms of their ability to reproduce the 2-m temperature trends of the late 20th century over North America. Trends will be compared to the driving reanalysis (the NCEP-DOE global reanalysis II: R2) as well as multiple observation-based datasets for 1980-2004. Available global

M. S. Bukovsky; L. O. Mearns

2010-01-01

133

Reconciling disparate twentieth-century Indo-Pacific ocean temperature trends in the instrumental record  

NASA Astrophysics Data System (ADS)

Large discrepancies exist between twentieth-century tropical Indo-Pacific sea surface temperature trends determined from present reconstructions. These discrepancies prevent an unambiguous verification and validation of climate models used for projections of future climate change. Here we demonstrate that a more consistent and robust trend among all the reconstructions is found by filtering each data set to remove El Niño/Southern Oscillation (ENSO), which is represented not by a single-index time series but rather by an evolving dynamical process. That is, the discrepancies seem to be largely the result of different estimates of ENSO variability in each reconstruction. The robust ENSO-residual trend pattern represents a strengthening of the equatorial Pacific temperature gradient since 1900, owing to a systematic warming trend in the warm pool and weak cooling in the cold tongue. Similarly, the ENSO-residual trend in sea-level pressure represents no weakening of the equatorial Walker circulation over the same period. Additionally, none of the disparate estimates of post-1900 total eastern equatorial Pacific sea surface temperature trends are larger than can be generated by statistically stationary, stochastically forced empirical models that reproduce ENSO evolution in each reconstruction.

Solomon, Amy; Newman, Matthew

2012-09-01

134

Trends in the mesopause region temperature and our present understanding—an update  

NASA Astrophysics Data System (ADS)

A comprehensive review of the long-term changes and trends in the thermal structure of the mesosphere and lower thermosphere (MLT) region has been provided by Beig et al. [Beig, G., Keckhut, P., Lowe, R.P., Roble, R.G., Mlynczak, M.G., Scheer, J., Fomichev, V.I., Offermann, D., French, W.J.R., Shepherd, M.G., Semenov, A.I., Remsberg, E.E., She, C.Y., Lübken, F.J., Bremer, J., Clemesha, B.R., Stegman, J., Sigernes, F., Fadnavis, S., 2003. Review of mesospheric temperature trends. Rev. Geophys. 41 (4), 1015, doi: 10.1029/2002RG000121] in which results and analysis reported until about early 2002 were included. Since then not much new information on the temperature trends has been added. Nevertheless, some new results along with some modified results by revisiting the older data sets have been reported in recent time. Our understanding on the nature of temperature trends in the MLT region is relatively better understood now and model agreements with some of the specific observed feature are better reproduced in recent time. This paper briefly summarizes the progress made over the recent past in the field of mesopause region temperature trends and provide an update to Beig et al. (2003). Some new information is also added in recent time on the seasonal trend variability in temperature of the mesopause region which is also discussed in this article. Finally the new insight into the probable mechanisms to understand the observed trends along with future scope of the work in this field is outlined.

Beig, Gufran

135

Interpretation of interdecadal trends in northern hemisphere surface air temperature  

SciTech Connect

Monthly mean time series of (1) surface air temperature anomalies averaged over the Northern Hemisphere based on data from land stations, (2) sea surface temperature anomalies averaged over the Northern Hemisphere oceans, and (3) 1000-500-mb thickness anomalies averaged over the region poleward of 40{degrees}N are examined. The data are stratified in terms of warm (May - October) and cold (November - April) seasons. Time series (1) and (3) based on cold-season data exhibit much larger month to month variability and a richer spectrum of interannual variability than those based on warm-season data: the interdecadal to century scale variability stands out more clearly in the warm-season time series. Cold- and warm-season time series for (1) differ substantially, even when heavily smoothed. It is hypothesized that the richer spectrum of variability in the cold-season time series is dynamically induced. To test this hypothesis, departures of cold-season data for (1) and (3) from their respective smoothed warm-season time series are regressed upon the hemispheric 1000-500-mb thickness field. Anomalously warm cold-season months are shown to be characterized by circulation regimes conductive to positive thickness anomalies over the high-latitude continents. A simple index of this distinctive {open_quotes}cold ocean - warm land{close_quotes} (COWL) pattern accounts for 65% of the variance of (1) during the cold-season months and for most of the discrepancies between its 5-yr running mean cold- and warm-season time series. The anomalous warmth of the winters of the 1980s is consistent with the strong positive bias of the COWL pattern index during the cold seasons of that decade. 35 refs., 13 figs.

Wallace, J.M.; Zhang, Yuan; Bajuk, L. [Univ. of Washington, Seattle, WA (United States)

1996-02-01

136

Trends and temperature sensitivity of moisture conditions in the conterminous United States  

USGS Publications Warehouse

Observed (1895-1999) trends in climatic moisture conditions in the conterminous United States (US) characterized by (1) annual precipitation minus annual potential evapotranspiration (PMPE), (2) annual surplus (water that eventually becomes streamflow), and (3) annual deficit (the amount of water that must be supplied by irrigation to grow vegetation at an optimum rate) are examined. The sensitivity of moisture conditions across the conterminous US to increases in temperature also are examined. Results indicate that there have been statistically significant trends in PMPE, annual surplus, and annual deficit for some parts of the conterminous US. Most of the significant trends in PMPE have been increasing trends primarily in the eastern US. Annual surplus also has increased over the eastern US, whereas the magnitudes of annual deficit have decreased. For the conterminous US as a whole, there has been a statistically significant increase in PMPE and annual surplus; however, there is no significant trend in annual deficit. Results also indicate that PMPE and annual deficit in the warmest regions of the conterminous US are most sensitive to increase in temperature. The high sensitivity of PMPE and annual deficit in these regions to increases in temperature is related to the relation between temperature and the saturation vapor pressure of air. The increases in potential evapotranspiration for a given change in temperature are larger for high temperatures than for low temperatures. The regions with the highest sensitivity of annual surplus to increases in temperature are the humid regions of the country. In these regions, annual surplus is large and increased potential evapotranspiration, resulting from increased temperature, has a significant effect on reducing annual surplus. In the dry regions of the country, annual surplus is so low that increases in potential evapotranspiration only result in small decreases in annual surplus.

McCabe, G. J.; Wolock, D. M.

2002-01-01

137

Analysis of temperature trends, heat and cold waves in Central Italy (1952-2008)  

NASA Astrophysics Data System (ADS)

Most of the recent studies on climate change agree in assessing a positive global trend of the mean temperature. However, analysis of temperature data at basin scale appears to be quite complicated because of several factors affecting measures: location, slope exposition, distance from the sea, etc., resulting in a high meteorological variability also at short distances. In this study we present an analysis of minimum and maximum daily temperature data registered in Umbria Region (Tiber Basin, Central Italy) for the period 1952-2008 in order to estimate mean trends and possible increases in the "extreme events" such us "heat waves" and "cold waves". Among the about 80 stations available for the study period, only those ones with at least 45 years of data, even not consecutive, have been retained, resulting in a data set of only 5 stations. Data have been analyzed at annual and seasonal time scale, taking into account the spatial trend due to the elevation. The spatial correlation among stations appear to be quite high, but not related to the reciprocal distances. The time trend of each temperature time series has been studied by means of classical trend tests (Mann-Kendall and t-Student test). Results are comparable for the two tests but not unique for minimum and maximum temperature. Concerning Tmax, 3 out of 5 stations present a positive trend in the last 30 years, ranging from 0.02 to 0.09 °C/y, while the remaining two stations do not present any significant trend; however, the same stations show a negative trend over the period 1960-1990. This results in a positive trend over the whole period 1952-2008 ranging from 0.02 to 0.03 °C/y. Concerning Tmin, 3 out of 5 of the study stations do not present any statistically significant trend over the last 30 years, while one station shows a negative trend (- 0.05 °C/y) and one a positive trend (+ 0.07 °C/y); moreover, 3 out of 5 stations have a significant positive trend in the period 1952-2008 (the annual temperature gradient ranging from 0.02 to 0.04 °C/y), 1 station shows a significant negative trend (- 0.02 °C/y). The spatial dishomogeneity in the signal suggests that anthropic factors could influence very much the variations of temperatures in the last 60 years, preventing from using such data, like they are, as climatic indicators. The occurrence of "heat waves" has been analyzed considering the persistence of temperatures higher than the 90-th percentile for 5 consecutive days; analogously, the occurrence of "cold wave" has been found out considering the persistence of temperatures lower than the 10-th percentile for 5 consecutive days. Results indicate that in the last 20 years the number of heat waves has significantly increased with respect to the previous period, while an increasing of the cold waves has not been enhanced.

Romano, E.; Volpi, E.; Stefanucci, F.

2012-04-01

138

Trends in record-breaking temperatures for the conterminous United States  

NASA Astrophysics Data System (ADS)

In an unchanging climate, record-breaking temperatures are expected to decrease in frequency over time, as established records become increasingly more difficult to surpass. This inherent trend in the number of record-breaking events confounds the interpretation of actual trends in the presence of any underlying climate change. Here, a simple technique to remove the inherent trend is introduced so that any remaining trend can be examined separately for evidence of a climate change. As this technique does not use the standard definition of a broken record, our records* are differentiated by an asterisk. Results for the period 1961-2010 indicate that the number of record* low daily minimum temperatures has been significantly and steadily decreasing nearly everywhere across the United States while the number of record* high daily minimum temperatures has been predominantly increasing. Trends in record* low and record* high daily maximum temperatures are generally weaker and more spatially mixed in sign. These results are consistent with other studies examining changes expected in a warming climate.

Rowe, Clinton M.; Derry, Logan E.

2012-08-01

139

Analysis and assessment of time-variant linear trends in annual economic data series with an application to energy forecasting for the state of Ohio  

Microsoft Academic Search

The time paths of many annual data series pertaining to the provision or disposition of energy in the US or Ohio have followed distinctly different linear trends over successive subdomains in the period 1960 to 1981. Explanations of these trends on the basis of traditional methods have turned out to be seriously misleading. In this thesis a system theoretic framework

Feyzioglu

1983-01-01

140

Nonparametric bootstrap confidence intervals for deterministic trends in temperature time series data  

NASA Astrophysics Data System (ADS)

In this paper we extend the methodology of Bühlmann (1998) who proposes sieve bootstrap confidence intervals for constructing confidence intervals for deterministic trends in dependent time series in a nonparametric way. We demonstrate that instead of the sieve bootstrap one can also use the block bootstrap to allow for nonlinear dependencies in the underlying process. We also extend the framework to a panel data setup. One of the appealing features of the bootstrap in this setting is that it can easily deliver simultaneous confidence intervals over parts of the time span of the data, thereby allowing one to investigate whether significant increasing or decreasing trends exist without assuming a parametric form for the trend. We apply these methods to study the presence of significant increasing/decreasing trends in long temperature time series data series for various European cities over a period ranging from 1830 to 2006.

Palm, F. C.; Smeekes, S.; Urbain, J.-P.

2009-04-01

141

A SIMPLE ALGORITHM FOR PRODUCTION POLICIES WITH A LINEAR TREND IN DEMAND  

Microsoft Academic Search

Under a fixed time horizon and a finite production rate, Hill (4) was the first to study the optimal production policy for a linearly increasing demand, but his approach followed Donaldson's analytic approach (1) with a complicated computation using tabular and in- terpolation. In addition, Omar et al. (6) presented a dynamic programming approach for the same problem with a

Bing-Chang OuYang

142

Recent trends of temperature change under hot and cold desert climates: Comparing the Sahara (Libya) and Central Asia (Xinjiang, China)  

Microsoft Academic Search

According to trend computations at three stations each in Sahara desert (Libya), characterized by a “hot” desert type (“BWh”, according to the Koeppen climate classification), and in Central Asia (Xinjiang, China) identified as a “cold” desert type (“BWk”, after Koeppen), increasing annual temperatures were detected over the period 1955–2005 corresponding with global temperature warming. From 1955–1978, negative (decreasing) temperature trends

B. Mamtimin; A. M. M. Et-Tantawi; D. Schaefer; F. X. Meixner; M. Domroes

2011-01-01

143

Intercomparison of temperature trends in IPCC CMIP5 simulations with observations, reanalyses and CMIP3 models  

NASA Astrophysics Data System (ADS)

On the basis of the fifth Coupled Model Intercomparison Project (CMIP5) and the climate model simulations covering 1979 through 2005, the temperature trends and their uncertainties have been examined to note the similarities or differences compared to the radiosonde observations, reanalyses and the third Coupled Model Intercomparison Project (CMIP3) simulations. The results show noticeable discrepancies for the estimated temperature trends in the four data groups (radiosonde, reanalysis, CMIP3 and CMIP5), although similarities can be observed. Compared to the CMIP3 model simulations, the simulations in some of the CMIP5 models were improved. The CMIP5 models displayed a negative temperature trend in the stratosphere closer to the strong negative trend seen in the observations. However, the positive tropospheric trend in the tropics is overestimated by the CMIP5 models relative to CMIP3 models. While some of the models produce temperature trend patterns more highly correlated with the observed patterns in CMIP5, the other models (such as CCSM4 and IPSL_CM5A-LR) exhibit the reverse tendency. The CMIP5 temperature trend uncertainty was significantly reduced in most areas, especially in the Arctic and Antarctic stratosphere, compared to the CMIP3 simulations. Similar to the CMIP3, the CMIP5 simulations overestimated the tropospheric warming in the tropics and Southern Hemisphere and underestimated the stratospheric cooling. The crossover point where tropospheric warming changes into stratospheric cooling occurred near 100 hPa in the tropics, which is higher than in the radiosonde and reanalysis data. The result is likely related to the overestimation of convective activity over the tropical areas in both the CMIP3 and CMIP5 models. Generally, for the temperature trend estimates associated with the numerical models including the reanalyses and global climate models, the uncertainty in the stratosphere is much larger than that in the troposphere, and the uncertainty in the Antarctic is the largest. In addition, note that the reanalyses show the largest uncertainty in the lower tropical stratosphere, and the CMIP3 simulations show the largest uncertainty in both the south and north polar regions.

Xu, J.; Powell, A. M., Jr.; Zhao, L.

2013-10-01

144

A high-temperature double-mode piezoelectric ultrasonic linear motor  

NASA Astrophysics Data System (ADS)

A miniature piezoelectric ultrasonic linear motor (piezoelectric vibrator sizes: 4.7 × 13.5 × 2 mm3) has been studied for precise actuation at 200 °C high-temperature. This piezoelectric linear motor was made of (1-x)BiScO3-xPbTiO3 piezoelectric ceramic with a high curie temperature (428 °C) and it was operated in first longitudinal and the second bending double-mode. Our experimental results showed that the linear motor moves smoothly at the temperature as high as 200 °C with a driving force of 0.35 N and a speed up to 42 mm/s.

Li, Xiaotian; Chen, Jianguo; Chen, Zhijiang; Dong, Shuxiang

2012-08-01

145

Long-term temperature trends in the middle stratosphere of the Northern Hemisphere  

NASA Astrophysics Data System (ADS)

Analysis of Northern Hemisphere mid-latitude temperature data at the 30-mbar level over the last 20 years, based on daily hemispheric analyses of radiosonde data, suggests a long-term negative trend of about -0.6 K/decade (between 50 and 60 N), and a negative trend of about -0.24 K/decade when all observations between 10N and 90N are considered, until April 1980. This stratospheric cooling which has been tentatively attributed to the increase of the carbon dioxide amount in the stratosphere is in qualitative agreement at 30 mbar with model calculations of the historical evolution of temperature and chemical composition in the middle atmosphere. The temperature increase detected after April 1980 which is attributed to the increased aerosol load after the volcanic eruptions of Mount St.Helens and E1 Chichon is discussed briefly. A comparison with another trend analysis based on monthly mean values of selected stations is also discussed, and it is shown that this data set is incomplete before the year 1970, because of missing data over the USSR. In summary, the use of carefully analyzed radiosonde data for monitoring temperature trends in the middle stratosphere is strongly advocated.

Labitzke, K.; Naujokat, B.; Angell, J. K.

146

Recent and future sea surface temperature trends in tropical pacific warm pool and cold tongue regions  

NASA Astrophysics Data System (ADS)

Using coral data, sea surface temperature (SST) reanalysis data, and Climate Model Intercomparison Project III (CMIP3) data, we analyze 20th-century and future warm pool and cold tongue SST trends. For the last 100 years, a broad La Nina-like SST trend, in which the warming trend of the warm pool SST is greater than that of the cold tongue SST, has appeared in reanalysis SST data sets, 20C scenario experiments of the CMIP3 data and less significantly in coral records. However, most Coupled General Circulation Models subjected to scenarios of future high greenhouse gas concentrations produce larger SST warming trends in cold tongues than in warm pools, resembling El Nino-like SST patterns. In other words, warmer tropical climate conditions correspond to stronger El Nino-like response. Heat budget analyses further verify that warmer tropical climates diminish the role of the ocean's dynamic thermostat, which currently regulates cold tongue temperatures. Therefore, the thermodynamic thermostat, whose efficiency depends on the mean temperature, becomes the main regulator (particularly via evaporative cooling) of both warm pool and cold tongue temperatures in future warm climate conditions. Thus, the warming tendency of the cold tongue SST may lead that of the warm pool SST in near future.

An, Soon-Il; Kim, Ji-Won; Im, Seul-Hee; Kim, Beak-Min; Park, Jae-Heung

2012-09-01

147

Trends in temperature extremes in association with weather-intraseasonal fluctuations in eastern China  

Microsoft Academic Search

Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, warm nights and cold nights)\\u000a with respect to a modulated annual cycle (MAC), and those associated exclusively with weather-intraseasonal fluctuations (WIF)\\u000a in eastern China were investigated based on an updated homogenized daily maximum and minimum temperature dataset for 1960–2008.\\u000a The Ensemble Empirical Mode Decomposition (EEMD)

Cheng Qian; Zhongwei Yan; Zhaohua Wu; Congbin Fu; Kai Tu

2011-01-01

148

Air temperature trend and the impact on winter wheat phenology in Romania  

Microsoft Academic Search

Air temperature variability and trends in Romania were analysed using monthly, seasonal, and annual datasets. Temperature\\u000a data of winter wheat season were also analysed. The Mann-Kendall test, Sen’s slope estimate, the sequential version of the\\u000a Mann-Kendall test, the Pettitt test and spatial and temporal hierarchical cluster analyses were used. First, the datasets\\u000a were checked for changing points. The 106-year period

Adina-Eliza Croitoru; Iulian-Horia Holobaca; Catalin Lazar; Florin Moldovan; Alexandru Imbroane

2012-01-01

149

Recent trends in daily temperature extremes over northeastern Spain (1960-2006)  

NASA Astrophysics Data System (ADS)

Spatial and temporal characteristics of extreme temperature events in northeastern Spain have been investigated. The analysis is based on long-term, high-quality, and homogenous daily maximum and minimum temperature of 128 observatories spanning the period from 1960 to 2006. A total of 21 indices were used to assess changes in both the cold and hot tails of the daily temperature distributions. The presence of trends in temperature extremes was assessed by means of the Mann-Kendall test. However, the autocorrelation function (ACF) and a bootstrap methodology were used to account for the influence of serial correlation and cross-correlation on the trend assessment. In general, the observed changes are more prevalent in hot extremes than in cold extremes. This finding can largely be linked to the increase found in the mean maximum temperature during the last few decades. The results indicate a significant increase in the frequency and intensity of most of the hot temperature extremes. An increase in warm nights (TN90p: 3.3 days decade-1), warm days (TX90p: 2.7 days decade-1), tropical nights (TR20: 0.6 days decade-1) and the annual high maximum temperature (TXx: 0.27 °C decade-1) was detected in the 47-yr period. In contrast, most of the indices related to cold temperature extremes (e.g. cold days (TX10p), cold nights (TN10p), very cold days (TN1p), and frost days (FD0)) demonstrated a decreasing but statistically insignificant trend. Although there is no evidence of a long-term trend in cold extremes, significant interdecadal variations were noted. Almost no significant trends in temperature variability indices (e.g. diurnal temperature range (DTR) and growing season length (GSL)) are detected. Spatially, the coastal areas along the Mediterranean Sea and the Cantabrian Sea experienced stronger warming compared with mainland areas. Given that only few earlier studies analyzed observed changes in temperature extremes at fine spatial resolution across the Iberian Peninsula, the results of this work can improve our understanding of climatology of temperature extremes. Also, these findings can have different hydrological, ecological and agricultural implications (e.g. crop yields, energy consumption, land use planning and water resources management).

El Kenawy, A.; López-Moreno, J. I.; Vicente-Serrano, S. M.

2011-09-01

150

Evaluation of notched fatigue strength at elevated temperature by linear notch mechanics  

Microsoft Academic Search

The notched fatigue strength of nickel-base superalloy Inconel 718 has been investigated under rotating bending loading at room temperature and 500°C in air. The applicability of linear notch mechanics to the evaluation of notched fatigue strength at elevated temperature was assessed in terms of the fatigue limit for crack initiation and that for crack growth. The effect of temperature on

Qiang Chen; Norio Kawagoishi; Hironobu Nisitani

1999-01-01

151

Time trends in minimum mortality temperatures in Castile-La Mancha (Central Spain): 1975–2003  

Microsoft Academic Search

The relationship between air temperature and human mortality is described as non-linear, with mortality tending to rise in\\u000a response to increasingly hot or cold ambient temperatures from a given minimum mortality or optimal comfort temperature, which\\u000a varies from some areas to others according to their climatic and socio-demographic characteristics. Changes in these characteristics\\u000a within any specific region could modify this

Isidro J. Miron; Juan José Criado-Alvarez; Julio Diaz; Cristina Linares; Sheila Mayoral; Juan Carlos Montero

2008-01-01

152

Linear relation between TH (homogeneous ice nucleation temperature) and Tm (melting temperature) for aqueous solutions of sucrose, trehalose, and maltose  

NASA Astrophysics Data System (ADS)

Homogeneous ice nucleation temperatures ( THs) of aqueous sucrose, trehalose, and maltose solutions were measured together with melting temperatures ( Tms). It is shown that there is a linear relation between TH and Tm for these solutions. Almost identical supercooling behavior is observed for these aqueous disaccharide solutions.

Kanno, Hitoshi; Soga, Makoto; Kajiwara, Kazuhito

2007-08-01

153

Land use/land cover change effects on temperature trends at U.S. Climate Normals stations  

USGS Publications Warehouse

Alterations in land use/land cover (LULC) in areas near meteorological observation stations can influence the measurement of climatological variables such as temperature. Urbanization near climate stations has been the focus of considerable research attention, however conversions between non-urban LULC classes may also have an impact. In this study, trends of minimum, maximum, and average temperature at 366 U.S. Climate Normals stations are analyzed based on changes in LULC defined by the U.S. Land Cover Trends Project. Results indicate relatively few significant temperature trends before periods of greatest LULC change, and these are generally evenly divided between warming and cooling trends. In contrast, after the period of greatest LULC change was observed, 95% of the stations that exhibited significant trends (minimum, maximum, or mean temperature) displayed warming trends. Copyriht 2006 by the American Geophysical Union.

Hale, R. C.; Gallo, K. P.; Owen, T. W.; Loveland, T. R.

2006-01-01

154

Did the global temperature trend change at the end of the 1990s?  

NASA Astrophysics Data System (ADS)

The apparent leveling of the global temperature time series at the end of the 1990s may represent a break in the upward trend. A study of the time series measurements for temperature, carbon dioxide, humidity and methane shows changes coincident with phase changes of the Atlantic and Pacific Decadal Oscillations. There are changes in carbon dioxide, humidity and methane measurement series in 2000. If these changes mark a phase change of the Pacific Decadal Oscillation then it might explain the global temperature behavior.

Quirk, Tom

2012-11-01

155

Non-linear Dielectric Responses of a Model Glass Former under Oscillating Temperature  

NASA Astrophysics Data System (ADS)

Exploiting a simple model for glass formers, we investigate dielectric response under oscillating temperature. We find that three characteristic temperatures, Vogel--Fulcher, glass transition and cross-over temperatures, can be determined from the analysis of the non-linear dielectric response. We also find a new characteristic temperature T3 which signifies divergence of the third moment of the waiting time distribution and can be detected by additional peaks in the imaginary part of the second order susceptibility.

Odagaki, Takashi; Kuroda, Masatoshi; Saruyama, Yasuo

2012-10-01

156

The role of aerosol in producing non-linear trends in CMIP5 historical simulations  

NASA Astrophysics Data System (ADS)

Variations in aerosol emissions have been implicated in producing variability on decadal timescales in the global temperature record. In this study, we apply the technique of Ensemble Empirical Mode Decomposition (EEMD) to the historical simulations from the CMIP5 models. Those that include a representation of the indirect effect of aerosol more closely reproduce historical global-mean near-surface temperatures, particularly the cooling in the 1950s and 1960s, compared to models with only a representation of the direct effect. Analysis of the available single forcing runs shows that this cooling is the result of a combination of natural and anthropogenic aerosol forcing. Models with the indirect effect also show a more pronounced decrease in precipitation in this period. This demonstrates the importance of representing aerosol, and their indirect effects, in general circulation models. We also discuss issues raised by the diversity of aerosol load and interactions in the CMIP5 models.

Highwood, Ellie; Wilcox, Laura

2013-04-01

157

Trends in surface air temperature and temperature extremes in the Great Basin during the 20th century from ground-based observations  

NASA Astrophysics Data System (ADS)

We analyzed trends in surface air temperature and temperature extremes in the Great Basin during 1901-2010. We found that annual average daily minimum temperature increased significantly (0.9 ± 0.2°C) during the study period, with daily maximum temperature increasing only slightly. The asymmetric increase in daily minimum and maximum temperature resulted in daily diurnal temperature range (DTR) decreasing significantly from 1901 to 2010. Seasonally, increases in daily minimum temperature and decreases in DTR occurred in winter, summer, and autumn, but the rate of increase was faster in winter. In contrast, daily maximum temperature showed no significant trend in any season. These trends in temperature measures, however, were not monotonic with decadal periods that included either reversal or acceleration of century-scale trends. The trend magnitudes in temperatures were not significantly associated with elevations. Increases in daily minimum temperature resulted in a decrease in the number of frost days (-0.14 ± 0.04 day yr-1) and cool nights (-0.09 ± 0.04 night yr-1) from 1901 to 2010, while the number of warm days (0.11 ± 0.04 day yr-1) and warm nights (0.19 ± 0.03 night yr-1) increased significantly. Surprisingly, the number of cool days and the length of the growing season showed no significant trend during the study period. Thus, the results of this study suggest that continuation of the overall warming trend would lead to markedly warmer conditions in upcoming decades.

Tang, Guoping; Arnone, John A.

2013-05-01

158

Self-focusing and defocusing of Gaussian laser beams in plasmas with linear temperature ramp  

SciTech Connect

The propagation characteristics of the Gaussian laser beam in plasmas in the presence of a linear electron temperature ramp have been investigated by taking the electron temperature as an individual variable. The ponderomotive force and collision have been considered as the mechanisms of nonlinearity. The second order differential equation of the dimensionless beam-width parameter has been acquired and solved with several initial electron temperatures and plus-minus temperature ramp parameters. The propagation regimes of laser beam are found to be sensitive with the selection of electron temperature. The linear temperature ramp breaks the stationary propagating mode and enhances the self-focusing or defocusing propagation properties. Results indicate the feasibility of extended propagation of focused laser beam in plasmas by modifying the electron temperature.

Zhou Zhongxiang; Wang Ying; Yuan Chengxun; Du Yanwei [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China)

2011-07-15

159

Records and sequences of records from random variables with a linear trend  

NASA Astrophysics Data System (ADS)

We consider records and sequences of records drawn from discrete time series of the form Xn = Yn + cn, where the Yn are independent and identically distributed random variables and c is a constant drift. For very small and very large drift velocities, we investigate the asymptotic behavior of the probability pn(c) of a record occurring in the nth step and the probability PN(c) that all N entries are records, i.e. that X_1 \\lt X_2 \\lt \\cdots \\lt X_N . Our work is motivated by the analysis of temperature time series in climatology, and by the study of mutational pathways in evolutionary biology.

Franke, Jasper; Wergen, Gregor; Krug, Joachim

2010-10-01

160

A quantification of uncertainties in historical tropical tropospheric temperature trends from radiosondes  

NASA Astrophysics Data System (ADS)

The consistency of tropical tropospheric temperature trends with climate model expectations remains contentious. A key limitation is that the uncertainties in observations from radiosondes are both substantial and poorly constrained. We present a thorough uncertainty analysis of radiosonde-based temperature records. This uses an automated homogenization procedure and a previously developed set of complex error models where the answer is known a priori. We perform a number of homogenization experiments in which error models are used to provide uncertainty estimates of real-world trends. These estimates are relatively insensitive to a variety of processing choices. Over 1979-2003, the satellite-equivalent tropical lower tropospheric temperature trend has likely (5-95% confidence range) been between -0.01 K/decade and 0.19 K/decade (0.05-0.23 K/decade over 1958-2003) with a best estimate of 0.08 K/decade (0.14 K/decade). This range includes both available satellite data sets and estimates from models (based upon scaling their tropical amplification behavior by observed surface trends). On an individual pressure level basis, agreement between models, theory, and observations within the troposphere is uncertain over 1979 to 2003 and nonexistent above 300 hPa. Analysis of 1958-2003, however, shows consistent model-data agreement in tropical lapse rate trends at all levels up to the tropical tropopause, so the disagreement in the more recent period is not necessarily evidence of a general problem in simulating long-term global warming. Other possible reasons for the discrepancy since 1979 are: observational errors beyond those accounted for here, end-point effects, inadequate decadal variability in model lapse rates, or neglected climate forcings.

Thorne, Peter W.; Brohan, Philip; Titchner, Holly A.; McCarthy, Mark P.; Sherwood, Steve C.; Peterson, Thomas C.; Haimberger, Leopold; Parker, David E.; Tett, Simon F. B.; Santer, Benjamin D.; Fereday, David R.; Kennedy, John J.

2011-06-01

161

Trend analysis of air temperature and precipitation time series over Greece: 1955-2010  

NASA Astrophysics Data System (ADS)

In this study, a database of air temperature and precipitation time series from the network of Hellenic National Meteorological Service has been developed in the framework of the project GEOCLIMA, co-financed by the European Union and Greek national funds through the Operational Program "Competitiveness and Entrepreneurship" of the Research Funding Program COOPERATION 2009. Initially, a quality test was applied to the raw data and then missing observations have been imputed with a regularized, spatial-temporal expectation - maximization algorithm to complete the climatic record. Next, a quantile - matching algorithm was applied in order to verify the homogeneity of the data. The processed time series were used for the calculation of temporal annual and seasonal trends of air temperature and precipitation. Monthly maximum and minimum surface air temperature and precipitation means at all available stations in Greece were analyzed for temporal trends and spatial variation patterns for the longest common time period of homogenous data (1955 - 2010), applying the Mann-Kendall test. The majority of the examined stations showed a significant increase in the summer maximum and minimum temperatures; this could be possibly physically linked to the Etesian winds, because of the less frequent expansion of the low over the southeastern Mediterranean. Summer minimum temperatures have been increasing at a faster rate than that of summer maximum temperatures, reflecting an asymmetric change of extreme temperature distributions. Total annual precipitation has been significantly decreased at the stations located in western Greece, as well as in the southeast, while the remaining areas exhibit a non-significant negative trend. This reduction is very likely linked to the positive phase of the NAO that resulted in an increase in the frequency and persistence of anticyclones over the Mediterranean.

Marougianni, G.; Melas, D.; Kioutsioukis, I.; Feidas, H.; Zanis, P.; Anandranistakis, E.

2012-04-01

162

21st century trends in Antarctic temperature and polar stratospheric cloud (PSC) area in the GEOS chemistry-climate model  

NASA Astrophysics Data System (ADS)

This study examines trends in Antarctic temperature and APSC, a temperature proxy for the area of polar stratospheric clouds, in an ensemble of Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) simulations of the 21st century. A selection of greenhouse gas, ozone-depleting substance, and sea surface temperature scenarios is used to test the trend sensitivity to these parameters. One scenario is used to compare temperature trends in two versions of the GEOS CCM. An extended austral winter season is examined in detail. In May, June, and July, the expected future increase in CO2-related radiative cooling drives temperature trends in the Antarctic lower stratosphere. At 50 hPa, a 1-3 K cooling is expected between 2000 and 2100. Ozone levels increase, despite this robust cooling signal and the consequent increase in APSC, suggesting the enhancement of stratospheric transport in future. In the lower stratosphere, the choice of climate change scenarios does not affect the magnitude of the early winter cooling. Midwinter temperature trends are generally small. In October, APSC trends have the same sign as the prescribed halogen trends. That is, there are negative APSC trends in "realistic future" simulations, where halogen loading decreases in accordance with the Montreal Protocol and CO2 continues to increase. In these simulations, the speed of ozone recovery is not influenced by either the choice of sea surface temperature and greenhouse gas scenarios or by the model version.

Hurwitz, M. M.; Newman, P. A.

2010-10-01

163

Non-linear finite element model to predict temperature histories within reinforced concrete in fires  

Microsoft Academic Search

A non-linear finite element procedure is proposed to predict the temperature distribution history of cross-sections of structural members, such as beams composed of reinforced concrete, in fire conditions. In this model the effect of moisture in concrete has been taken into account, and the thermal properties of concrete have been considered as temperature and moisture dependent. In order to validate

Zhaohui Huang; Andrew Platten; John Roberts

1996-01-01

164

Retention in multistep programmed-temperature gas chromatography and flow control Linear head pressure programs  

Microsoft Academic Search

A comparative study of retention in different systems of flow control that provide linear dependence with the temperature of the column's head pressure is performed by numerical simulation considering multistep (or multiramp) PTGC (programmed-temperature gas chromatography) as the most general situation. Calculation algorithms for each flow control mode are developed on the basis of a general retention equation and the

F. R. Gonzalez; A. M. Nardillo

1997-01-01

165

Difficulties in Obtaining Reliable Temperature Trends: Reconciling the Surface and Satellite Microwave Sounding Unit Records  

Microsoft Academic Search

A chronic difficulty in obtaining reliable climate records from satellites has been changes in instruments, platforms, equator-crossing times, and algorithms. The microwave sounding unit (MSU) tropospheric temperature record has overcome some of these problems, but evidence is presented that it too contains unreliable trends over a 17-yr period (1979-95) because of transitions involving different satellites and complications arising from nonatmospheric

James W. Hurrell; Kevin E. Trenberth

1998-01-01

166

Temperature and precipitation trends in Bologna (Italy) from 1952 to 1999  

Microsoft Academic Search

An analysis was made of a historical set of meteorological data collected at the University of Bologna agrometeorological station (Cadriano, Bologna, Italy, 40°55?N, 11°4?E, 33 m a.s.l.), between 1952 and 1999.Increasing trends of approximately 0.7 °C in 48 years in the mean annual temperature were found, all the anomalies of the last 12 years being above the average. A decrease

F. Ventura; P. Rossi Pisa; E. Ardizzoni

2002-01-01

167

Trend detection in surface air temperature in Ontario and Quebec, Canada during 1967–2006 using the discrete wavelet transform  

NASA Astrophysics Data System (ADS)

The main purpose of this study is to detect trends in the mean surface air temperature over the southern parts of Ontario and Quebec, Canada, for the period of 1967–2006. This is accomplished by determining the most dominant periodic components that affect trends in different temperature data categories (monthly, seasonally-based, seasonal, and annual), which were obtained from a total of five stations. The discrete wavelet transform (DWT) technique, the Mann–Kendall (MK) trend test, and sequential Mann–Kendall analysis were used in this study — co-utilizing these techniques in temperature trend studies has not been explored extensively. The mother wavelet, number of decomposition levels, and boundary condition were determined using a newly proposed criterion based on the relative error of the MK Z-values between the original data and the approximation component of the last decomposition level. This study found that all stations experienced positive trends: significant trends were observed in all of the monthly, seasonally-based, and annual data. For the different seasons, although the trend values were all positive, not all stations experienced significant trends. It was found that high-frequency components ranging from 2 to 12 months were more prominent for trends in the higher resolution data (i.e. monthly and seasonally based). The positive trends observed for the annual data are thought to be mostly attributable to warming during winter and summer seasons, which are manifested in the form of multiyear to decadal events (mostly between 8 and 16 years).

Nalley, D.; Adamowski, J.; Khalil, B.; Ozga-Zielinski, B.

2013-10-01

168

Chemical Reaction Effects on MHD Flow Past a Linearly Accelerated Vertical Plate with Variable Temperature and Mass Diffusion in the Presence of Thermal Radiation  

NASA Astrophysics Data System (ADS)

An exact solution of first order chemical reaction effects on a radiative flow past a linearly accelerated infinite isothermal vertical plate with variable mass diffusion, under the action of a transversely applied magnetic field has been presented. The plate temperature is raised linearly with time and the concentration level near the plate is also raised to C'w linearly with time. The dimensionless governing equations are tackled using the Laplace-transform technique. The velocity, temperature and concentration fields are studied for different physical parameters such as the magnetic field parameter, radiation parameter, chemical reaction parameter, thermal Grashof number, mass Grashof number, Schmidt number, Prandtl number and time. It is observed that velocity increases with decreasing magnetic field parameter or radiation parameter. But the trend is just reversed with respect to the chemical reaction parameter

Muthucumaraswamy, R.; Geetha, E.

2013-08-01

169

Seasonal trends in precipitation and surface air temperature extremes in mainland Portugal, 1941-2007  

NASA Astrophysics Data System (ADS)

Several climate models predict, on a global scale, modifications in climate variables that are expected to have impact on society and the environment. The concern is on changes in the variability of processes, the mean and extreme events (maximum and minimum). To explore recent changes in precipitation and near surface air temperature extremes in mainland Portugal, we have inspected trends in time series of specific indices defined for daily data. These indices were recommended by the Commission for Climatology/Climate Variability and Predictability (CCl/CLIVAR) Working Group on Climate Change Detection, and include threshold indices, probability indices, duration indices and other indices. The precipitation and air temperature data used in this study are from, respectively, 57 and 23 measuring stations scattered across mainland Portugal, and cover the periods 1941-2007, for precipitation, and 1941-2006, for temperature. The study focuses on changes at the seasonal scale. Strong seasonality is one of the main features of climate in mainland Portugal. Intensification of the seasonality signal across the territory, particularly in the more sensitive regions, might contribute to endanger already fragile soil and water resources and ecosystems, and the local environmental and economic sustainability. Thus, the understanding of variations in the intensity, frequency and duration of extreme precipitation and air temperature events at the intra-annual scale is particularly important in this geographical area. Trend analyses were conducted over the full period of the records and for sub-periods, exploring patterns of change. Results show, on the one hand, regional differences in the tendency observed in the time series analysed; and, on the other hand, that although trends in annual indices are in general not statistically significant, there are sometimes significant changes over time in the data at the seasonal scale that point out to an increase in the already existing asymmetries in the climate in mainland Portugal, including changes in the extremes of precipitation and surface air temperature.

de Lima, M. I. P.; Santo, F. E.; Ramos, A. M.

2012-04-01

170

Impurity effects on linear and nonlinear ion-temperature-gradient-driven modes  

Microsoft Academic Search

Linear and nonlinear stages in the development of the ion-temperature-gradient-driven drift-wave instability are studied analytically in the presence of shear flows, magnetic shear, inhomogeneity, and curvature. In the linear regime, it is shown that the toroidal &eegr;i mode is destabilized by a small amount of impurities only if there exists an impurity buildup at the plasma edge. In the nonlinear

D. Jovanovic; W. Horton

1995-01-01

171

Test on opto couplers in the linear application considering temperature, radiation and Vce effects  

NASA Astrophysics Data System (ADS)

The test result for four different types of opto couplers (20 devices each) operating at very low current levels (lower than the test condition for logic operation) considering temperature, radiation and absolute value of forward voltage (Vce) effects are presented. A galvanically isolated precision linear interface using a pair of opto couplers is introduced, which could be of interest in the areas of monitoring, control, control loops and linear interfaces for future space applications.

Spruijt, H.; Burrows, K.; Andersen, J.; Marsden, S.; Tilmant, J.

1991-03-01

172

Seasonal Temperature Forecasts as Products of Antecedent Linear and Spatial Temperature Arrays  

Microsoft Academic Search

Our objective is to evaluate the potential for extracting the maximum information contained in antecedent temperature patterns that operationally could be used in formulating winter seasonal forecasts in the United States. In particular, examination of the predictability of winter temperatures given autumn temperatures is made using derived contingency tables, discriminant equations of antecedent principal components, and canonical correlation analysis.Contingency tables

Merlin P. Lawson; Randall S. Cerveny

1985-01-01

173

Long-term Temperature Trends in the Thermosphere Based on Incoherent Scatter Radar Data  

NASA Astrophysics Data System (ADS)

We have developed a series of empirical models of Earth's ionosphere and thermosphere based on data from most of the world's incoherent scatter radars (ISRs). These models depend on solar and geomagnetic activity, but until recently have not included any long-term trend independent of those due to differences in geophysical indices from solar cycle to solar cycle. Greenhouse gases such as CO2 and CH4 are well known to be increasing in the lower atmosphere. The effect of this on the upper atmosphere, in particular, the ionosphere, has become an active topic of research since the publication of a theoretical modeling study by Roble and Dickinson suggesting a major greenhouse cooling in the thermosphere in response to increases in CO2 and CH4 concentration at 60 km. This cooling effect leads to a global reduction in neutral densities including O, N2 and total neutral mass density as the neutral temperature Tn decreases. We have addressed this using almost three solar cycles of Millstone Hill measurements of the ion temperature Ti, which is closely coupled to Tn. There is a statistically highly-significant long-term Ti trend ranging from -4 K/year to -8 K/year depending on time-of-day and altitude. Using the ion energy equation we find a similar trend for Tn.

Holt, J. M.; Zhang, S.; Kurdzo, J. M.

2007-12-01

174

The role of winter precipitation and temperature on northern Eurasian streamflow trends  

NASA Astrophysics Data System (ADS)

Eurasian river discharge into the Arctic Ocean has steadily increased during the 20th century, and many studies have documented the spatial distribution of the trends and hypothesized the causes. There is a large variation in the scope of these studies, including the spatial scale of interest, and they often lack consistency in the time period analyzed. Studies have shown a connection between changes in the seasonal snowpack and discharge, but they have been constrained by the limitations of the snow observational network, which contains few long-term stations. This study overcomes these problems by using both in situ observations and a land surface model to evaluate the role snowpack changes have had on increases in runoff across northern Eurasia from 1936 through 1999. Our analysis shows consistent trends in both observations and model predictions. Increases in cold season precipitation propagate into increases in maximum snow water equivalent, which lead to increases in runoff. A series of model experiments demonstrate that the nonlinear interaction between winter precipitation and temperature has driven changes in the snowpack, which are manifested in the modeled runoff trends. Given that winter precipitation is expected to continue to increase and temperatures to warm during the 21st century in this region, these results point to the importance in understanding how the projected changes will influence the seasonal snowpack, which may have important consequences for streamflow in this region and freshwater export to the Arctic Ocean.

Troy, Tara J.; Sheffield, Justin; Wood, Eric F.

2012-03-01

175

Higher trends but larger uncertainty and geographic variability in 21st century temperature and heat waves.  

PubMed

Generating credible climate change and extremes projections remains a high-priority challenge, especially since recent observed emissions are above the worst-case scenario. Bias and uncertainty analyses of ensemble simulations from a global earth systems model show increased warming and more intense heat waves combined with greater uncertainty and large regional variability in the 21st century. Global warming trends are statistically validated across ensembles and investigated at regional scales. Observed heat wave intensities in the current decade are larger than worst-case projections. Model projections are relatively insensitive to initial conditions, while uncertainty bounds obtained by comparison with recent observations are wider than ensemble ranges. Increased trends in temperature and heat waves, concurrent with larger uncertainty and variability, suggest greater urgency and complexity of adaptation or mitigation decisions. PMID:19805213

Ganguly, Auroop R; Steinhaeuser, Karsten; Erickson, David J; Branstetter, Marcia; Parish, Esther S; Singh, Nagendra; Drake, John B; Buja, Lawrence

2009-09-08

176

The investigation of temperature trend in the Antarctic using GPS radio occultation technique  

NASA Astrophysics Data System (ADS)

The Antarctic plays a vital role in the global atmospheric and oceanic systems and circulations because of its unique geographical and meteorological features. In recent years, abnormal melting of Antarctica ice sheet has been considered as a strong evidence of global warming. The phenomenon itself has significant feedback to the weather and climate processes. Climate change in the Antarctic and its impacts on global climate have drawn more and more attention of climatologists. Some studies have presented general warming trend of near-surface temperature in the Antarctic but cooling trends in some regions and seasons. Turner (2006) reported warming trend in the upper troposphere and cooling trend in the lower stratosphere. Most studies on the Antarctic meteorology and climatology predominately relies on only 18 weather stations operated by different countries. All these stations (expect the Amundsen-Scott station) are distributed along the coastline. The number and locations of these stations is inappropriate for the whole Antarctic continent area. Moreover, the extreme weather environment result in observations poor in both quantity and quality. The recently available atmospheric profiles derived from the Global Positioning System (GPS) radio occultation (RO) technique have demonstrated a great potential for advancing weather and climate studies, especially for remote areas such as the ocean and polar regions. The CHAMP mission provides nearly eight years (2001 - 2008) atmospheric data by using the GPS RO technique. COSMIC generates about 2,500 atmospheric profiles daily since 2006. Due to the global coverage of the GPS RO observations, a great number of high quality atmospheric information can be obtained over the Antarctic area. This study is to investigate the potential of using the GPS RO technique for the Antarctic climate monitoring. Although only eight-year CHAMP data available, the result has shown the significance of the GPS RO technique for reliable and long-term atmospheric monitoring. The new GPS-based technique overcomes many limitations of the current mainstream atmospheric observing techniques. The first part of this study is to evaluate GPS RO retrievals ) using radiosonde data in Antarctica. The mean difference in temperature between radiosonde and CHAMP is 0.065 C degree with a standard deviation of 1.272 C degree, and the mean difference for COSMIC data is 0.021 C degree with a standard deviation of 1.293 C degree. In the second section, a analysis of temperature change over the Antarctic region using CHAMP RO data is presented. Temperature trends at ten standard pressure levels and their seasonal and spatial variations are analyzed and discussed. Two notable findings are 1) warming trend was found in the West Antarctic and Peninsula and cooling trend in East Antarctica, and 2) general warming trend was identified in Winter but cooling in Summer. These findings are in agreement with previous studies that used the radiosonde and other satellite data. With future Global Navigation Satellite Systems and more GPS RO missions available, it is promising that the GPS RO technique will enhance the Antarctic climatological studies significantly.

Fu, E.

2010-12-01

177

An explanation of discrepancy in mesospheric temperature trends derived from ground-based LF phase-height observations  

NASA Astrophysics Data System (ADS)

Bremer and Berger (J. Atmos. Solar Terr. Phys. 64 (2002) 805) applied a correction for trends in the NO concentration and ?eff in the interpretation of trends in the low frequency (LF) phase height measurements and obtained results less consistent with model simulations as well as the observed trends in mesospheric temperatures. The correction is shown to be too large most probably due to the application of inappropriate trends in ?eff of Chakrabarty (Adv. Space Res. 20 (1997) 2117), which yield a trend in electron density opposite to that which is observed. The discrepancy between the observational data and model-simulated trends of Bremer and Berger (J. Atoms. Solar. Terr. Phys. 64 (2002) 805) in the LF phase heights can be largely removed. Even more important, the trends in mesospheric temperatures inferred by Bremer and Berger (J. Atmos. Solar Terr. Phys. 64 (2002) 805) from trends in the LF phase heights without the inappropriate correction agree well with the results of analysis of a global set of results on trends in the mesospheric temperatures by Beig et al. (Rev. Geophys. 41 (2003) 1015).

Laštovi?ka, J.

2004-12-01

178

Global and regional sea surface temperature trends during Marine Isotope Stage 11  

NASA Astrophysics Data System (ADS)

The Marine Isotope Stage (MIS) 11 (424-374 ka) was characterized by a protracted deglaciation and an unusually long climatic optimum. It remains unclear to what degree the climate development during this interglacial reflects the unusually weak orbital forcing or greenhouse gas trends. Previously, arguments about the duration and timing of the MIS11 climatic optimum and about the pace of the deglacial warming were based on a small number of key records, which appear to show regional differences. In order to obtain a global signal of climate evolution during MIS11, we compiled a database of 78 sea surface temperature (SST) records from 57 sites spanning MIS11, aligned these individually on the basis of benthic (N = 28) or planktonic (N = 31) stable oxygen isotope curves to a common time frame and subjected 48 of them to an empirical orthogonal function (EOF) analysis. The analysis revealed a high commonality among all records, with the principal SST trend explaining almost 49% of the variability. This trend indicates that on the global scale, the surface ocean underwent rapid deglacial warming during Termination V, in pace with carbon dioxide rise, followed by a broad SST optimum centered at ~410 kyr. The second EOF, which explained ~18% of the variability, revealed the existence of a different SST trend, characterized by a delayed onset of the temperature optimum during MIS11 at ~398 kyr, followed by a prolonged warm period lasting beyond 380 kyr. This trend is most consistently manifested in the mid-latitude North Atlantic and Mediterranean Sea and is here attributed to the strength of the Atlantic meridional overturning circulation. A sensitivity analysis indicates that these results are robust to record selection and to age-model uncertainties of up to 3-6 kyr, but more sensitive to SST seasonal attribution and SST uncertainties >1 °C. In order to validate the CCSM3 (Community Climate System Model, version 3) predictive potential, the annual and seasonal SST anomalies recorded in a total of 74 proxy records were compared with runs for three time slices representing orbital configuration extremes during the peak interglacial of MIS11. The modeled SST anomalies are characterized by a significantly lower variance compared to the reconstructions. Nevertheless, significant correlations between proxy and model data are found in comparisons on the seasonal basis, indicating that the model captures part of the long-term variability induced by astronomical forcing, which appears to have left a detectable signature in SST trends.

Milker, Y.; Rachmayani, R.; Weinkauf, M. F. G.; Prange, M.; Raitzsch, M.; Schulz, M.; Ku?era, M.

2013-10-01

179

Historical trends in tank 241-SY-101 waste temperatures and levels  

SciTech Connect

The gas release and fluctuating level of the waste in tank 241-SY-101 have prompted more detailed interest in its historical behavior, in hopes of achieving a better understanding of its current status. To examine the historical behavior, essentially all of the tank waste temperature and level data record has been retrieved, examined, and plotted in various ways. To aid in interpreting the data, the depth of the non-convective waste layer was estimated by using a least-squares Chebyshev approximation to the temperatures. This report documents the retrieval critical examination, and graphic presentation of 241-SY-101 temperature and waste level histories. The graphic presentations clearly indicate a tank cooling trend that has become precipitous since late 1991. The plots also clearly show the decreasing frequency of waste gas release events, increasing height of the non-convective layer, and larger level drops per event.

Antoniak, Z.I.

1993-09-01

180

Testing hypotheses in an I ( 2 ) model with piecewise linear trends. An analysis of the persistent long swings in the Dmk\\/$ rate  

Microsoft Academic Search

This paper discusses the I(2) model with breaks in the deterministic component and illustrates the model with an analysis of German and US prices, exchange rates, and interest rates in the period 1975–1999. It provides new results on the likelihood ratio test of overidentifying restrictions on the cointegrating relations when they contain piecewise linear trends. One important aim of the

Søren Johansen; Katarina Juselius; Roman Frydman; Michael Goldberg

2010-01-01

181

Temperature variability and trends in the UT-LS over a subtropical site: Reunion (20.8° S, 55.5° E)  

NASA Astrophysics Data System (ADS)

This paper mainly focuses on the trends and variability of the UT-LS temperature using radiosonde observations carried out over 16 years (January 1993 to December 2008) from a southern subtropical site, Reunion (20.8° S, 55.5° E), using a linear-regression fitting model. Two kinds of tropopause definitions, namely, cold point tropopause (CPT) and lapse rate tropopause (LRT) are used. In order to characterize and quantify the relationship between regional oceanic forcing and temperature at UT-LS, we took into account the Indian Ocean Dipole (IOD) for the estimation of temperature trends. Results show that the main component is the Annual Cycle (AC), particularly at tropopause (CPT, LRT) and in the lower stratosphere (LS) where more than 26.0±2.4% of temperature variability can be explained by AC. The influence of IOD on the variability of the temperature is at highest ratio at CPT and LS, with respectively 12.3±7.3% and 13.1±5.9%. The correlations between IOD and temperature anomalies at UT-LS are barely significant, which are found to be in close agreement with the results obtained by Rosenlof et al. (2008) over the western tropical Pacific Ocean. The temperature trend in the LS reveals a cooling of about -0.90±0.40 K per decade. The cooling trend at LS is found to be in close agreement with the others studies. Trend estimates in the LS suggest that IOD forcing contributes to increasing cooling by about 0.16±0.05 K per decade. Past works have shown that the additional carbon dioxide increase has a minor effect in the LS, and suggested that other effects than ozone and carbon dioxide changes have to be considered, in order to explain the observed temperature changes in the LS. From this study, we can suggest that the SST changes can be considered also, in addition to effects due to ozone and carbon dioxide changes, in order to explain the observed temperature changes in the LS. As a consequence, our results support the assumption that the Indian Ocean may have a slight impact on temperature variability and on temperature change in the LS over Reunion.

Bègue, N.; Bencherif, H.; Sivakumar, V.; Kirgis, G.; Mze, N.; Leclair de Bellevue, J.

2010-09-01

182

The effects of ionizing radiation on the Honeywell HTMOS high temperature linear CMOS technology  

Microsoft Academic Search

The high dose-rate transient response and radiation hardness to total ionizing dose of Honeywell's HTMOS 10 V linear technology were evaluated. Although this technology was designed for high-temperature applications, all irradiation and measurements herein were performed at room temperature. Results show that the HT1104 Quad Operational Amplifier and HT1204 Quad Analog Switch survive 5×1011 rads(Si)\\/s, with recovery times ⩽10 ?s.

D. Larsen; P. Welling; W. Tsacoyeanes

1996-01-01

183

Total internal partition sums in the temperature range 70-3000 K: Atmospheric linear molecules  

NASA Astrophysics Data System (ADS)

A method for the rapid calculation of the total internal partition sums of atmospheric molecules is presented. Coefficients for a polynomial expansion of the partition function for 11 closed shell linear molecular species and their isotopic variants contained in HITRAN (L. S. Rothman et al., Appl. Opt. 26, 4058-4097 (1987)) are given for two temperature regimes: 70-400 and 400-2005 K. In addition, a logarithmic expansion is presented for extrapolation to higher temperatures.

Gamache, Robert R.; Hawkins, Robert L.; Rothman, Laurence S.

1990-08-01

184

Temperature dependence of linear electrooptic coefficients r 113 and r 333 in lithium niobate  

Microsoft Academic Search

A new method of determination of individual linear electrooptic coefficients is proposed. The technique is based on the dynamic\\u000a polarimetric measurements and takes into consideration the temperature dependences of ordinary and extraordinary refractive\\u000a indices. Results obtained for the electrooptic coefficients r113 and r333 in LiNbO3 are presented. The coefficients are found to increase significantly within the considered temperature range 25-200°C.

P. Górski; R. Ledzion; K. Bondarczuk; W. Kucharczyk

2008-01-01

185

Trends in temperature extremes in association with weather-intraseasonal fluctuations in eastern China  

NASA Astrophysics Data System (ADS)

Trends in the frequencies of four temperature extremes (the occurrence of warm days, cold days, warm nights and cold nights) with respect to a modulated annual cycle (MAC), and those associated exclusively with weather-intraseasonal fluctuations (WIF) in eastern China were investigated based on an updated homogenized daily maximum and minimum temperature dataset for 1960-2008. The Ensemble Empirical Mode Decomposition (EEMD) method was used to isolate the WIF, MAC, and longer-term components from the temperature series. The annual, winter and summer occurrences of warm (cold) nights were found to have increased (decreased) significantly almost everywhere, while those of warm (cold) days have increased (decreased) in northern China (north of 40°N). However, the four temperature extremes associated exclusively with WIF for winter have decreased almost everywhere, while those for summer have decreased in the north but increased in the south. These characteristics agree with changes in the amplitude of WIF. In particular, winter WIF of maximum temperature tended to weaken almost everywhere, especially in eastern coastal areas (by 10%-20%); summer WIF tended to intensify in southern China by 10%-20%. It is notable that in northern China, the occurrence of warm days has increased, even where that associated with WIF has decreased significantly. This suggests that the recent increasing frequency of warm extremes is due to a considerable rise in the mean temperature level, which surpasses the effect of the weakening weather fluctuations in northern China.

Qian, Cheng; Yan, Zhongwei; Wu, Zhaohua; Fu, Congbin; Tu, Kai

2011-03-01

186

Analysis of Linear and Nonlinear Inversion of Optical Data for a Micrometeorological Temperature Profile  

Microsoft Academic Search

The practical inversion of optical data for a micrometeorological temperature profile requires a non- linear inversion of a system of polynomial equations. A method of nonlinear least squares can produce a physically acceptable solution of this nonlinear inversion problem. Because this method, which is dem- onstrated with the inversion of simulated optical data, does not produce an unique solution, the

William H. Mach

1981-01-01

187

Multi-decadal surface temperature trends in the East Antarctica using borehole firn temperature measurements and geophysical inverse method  

NASA Astrophysics Data System (ADS)

The interior of East Antarctic Ice Sheet (EAIS) remains one of the least explored areas on earth and as a result, its climate is one of the least-understood as well. Recent studies with techniques utilizing sparse available records and models have estimated a weak warming trend in East Antarctica for the past 50 years. However, these are not without uncertainties and additional data sources are needed in order to gain a better assessment of the East Antarctic climate trend. The objective of this investigation is to detect multi-decadal surface temperature trends in the interior of East Antarctica. Surface temperature inversion from vertical firn temperature profile measurements at several locations provides a source of climate reconstruction independent of firn chemistry, sparse weather data, satellite data, or ice cores. During the Norwegian-U.S. IPY Scientific Traverse of East Antarctica, in austral summers of 2007-08 and 2008-09, thermal-profiling units were installed at five locations. Each unit consists of 16 PRTs (Platinum Resistance Thermometers) distributed between depths of 0.15 and approximately 90 m. Wired PRTs were lowered into the borehole after an ice core was drilled and before the hole was back-filled with granulated snow to prevent air circulation and provide thermal conduction between PRTs and firn. Near-hourly data are being transmitted through ARGOS satellite telemetry system. The overall uncertainty in firn temperature measurement is 0.03 °C. A geophysical inverse method using the generalized inverse and regularization method was applied to one full year of data collected from three units installed in 2007-08. Results indicate that the recent decade is approximately 0.5 to 0.8 °C warmer than ~100 years ago, given assumptions on physical characteristics of the ice sheet (accumulation rate, geothermal heat flux, vertical advection, density and thermal properties). However, the precise onset and rate of the warming are undetermined at this stage. We will also present the preliminary results from the two sites installed in 2008-09 season, as well as the use of Monte Carlo inverse method. Initial analysis suggests that the southern station supports the results of the earlier stations but the near-coastal station near Kohnen appears to indicate a more significant warming.

Muto, A.; Scambos, T.; Steffen, K.

2009-12-01

188

Relationship between air and soil temperature trends and periodicities in the permafrost regions of Russia  

NASA Astrophysics Data System (ADS)

Soil temperature is an important indicator of frozen ground status, driven at least partly by air temperature variability. In this study we apply singular spectrum analysis (SSA) to detect trends and oscillations in annual and seasonal time series of surface air temperature (SAT) and soil temperature (ST). We investigate soil temperatures at depths of 0.4, 1.6, and 3.2 m for five permafrost-occupied regions in Russia. We use SAT data for 1902-1995 and ST data for 1960-1990. The trends show an increase in annual SAT and ST from the end of the 1960s across all five regions, and this warming exceeds that of the preceding period in the Central Siberian Plateau and Transbaikalia. Oscillations in annual SAT and ST time series are coincident in the West Siberian Plain (7.7 year period) and in the western Central Siberian Plateau and Transbaikalia (2.7 year period). In general, on a seasonal basis, 2-3 year oscillations in ST and SAT are coincident during winter, spring, and autumn across the regions and are also evident in the annual ST time series in the Central Siberian Plateau and Transbaikalia. We also find a decadal oscillation (9.8 year period), which is coincident for winter SAT and ST, over the western Central Siberian Plateau only. Although summer SAT and ST oscillations (5-8 year periods) are coincident for all investigated territories (except to the east of the Lena River), in the annual ST time series they are identified only for the West Siberian Plain. We document the degree to which SAT controls ST in each region and explore the causative factors for some of the dominant periods. The maximum effect of SAT increases on permafrost may be observed in the Central Siberian Plateau and Transbaikalia, while elsewhere the observed ST increases do not threaten permafrost areas.

Chudinova, Svetlana M.; Frauenfeld, Oliver W.; Barry, Roger G.; Zhang, Tingjun; Sorokovikov, Victor A.

2006-06-01

189

Variations and Trends in Global and Arctic Surface Temperature and Forecasts of Global Temperature a Year Ahead, 2000-2010. (Invited)  

Microsoft Academic Search

We comment in some detail on the difficulties of correctly capturing recent Arctic warming accurately in global surface temperature data sets. We also discuss likely biases in modern sea surface temperature (SST) data worldwide and the effect these may have on assessed global temperatures The latter likely lead to a small underestimation of global warming trends in the last decade

C. K. Folland; J. Kennedy; A. Colman; J. Knight; P. Stott; D. Smith; D. E. Parker

2010-01-01

190

Temperature Trends of the U.S. Historical Climatology Network Based on Satellite-Designated Land Use/Land Cover.  

NASA Astrophysics Data System (ADS)

The 1221 weather observation stations that compose the U.S. Historical Climatology Network were designated as either urban, suburban, or rural based on data from the Defense Meteorological Satellite Program Operational Linescan System (OLS). The designations were based on local and regional samples of the OLS data around the stations (OLS method). Trends in monthly maximum and minimum temperature and the diurnal temperature range (DTR) were determined for the 1950-96 interval for each of three land use/land cover (LULC) designations. The temperature trends for the OLS-derived designations of LULC were compared to similarly designated LULC based on (i) map- (Operational Navigation Charts) and population-based estimates of LULC (ONCP method), and (ii) LULC designations that resulted from of a survey of the network station operators. Although differences were not statistically significant, the DTR trends (degrees Celsius per 100 years) did differ between the LULC classes defined by the OLS method, from 0.41 for the rural stations to 0.86 for the urban stations. Trends also differed, although not significantly, between the methods used to define an LULC class, such that the trends in rural DTR varied from 0.41 for the OLS defined stations to 0.67 for the ONCP defined stations. Although the trends between classes were not significantly different, they do present some contrasts that might confound the interpretation of temperature trends when the local and regional environments associated with the analyzed stations are not considered. The general (urban, suburban, or rural) LULC associated with surface observation stations appears to be one of the factors that can influence the trends observed in temperatures and thus should be considered in the analysis and interpretation of temperature trends.

Gallo, Kevin P.; Owen, Timothy W.; Easterling, David R.; Jamason, Paul F.

1999-05-01

191

Recent trends of temperature change under hot and cold desert climates: Comparing the Sahara (Libya) and Central Asia (Xinjiang, China)  

NASA Astrophysics Data System (ADS)

According to trend computations at three stations each in Sahara desert (Libya), characterized by a "hot" desert type ("BWh", according to the Koeppen climate classification), and in Central Asia (Xinjiang, China) identified as a "cold" desert type ("BWk", after Koeppen), increasing annual temperatures were detected over the period 1955-2005 corresponding with global temperature warming. From 1955-1978, negative (decreasing) temperature trends were, however, observed at all three hot desert stations and at two of the three cold desert stations. From 1979-2005, strikingly positive temperature trends were seen at all six stations. In seasonal respects, winter (December to February) and summer (June to August) show different temperature trends over the period 1955-2005: the hot desert experienced an increasing temperature trend at a greater extent in summer than in winter; vice-versa, in the cold desert positive trends were computed for winter and negative for summer. It can also be observed that mostly hot desert warming occurred in summer, opposite to cold desert warming in winter.

Mamtimin, B.; Et-Tantawi, A. M. M.; Schäfer, D.; Meixner, F. X.; Domroes, M.

2012-04-01

192

Causes of differing temperature trends in radiosonde upper air data sets  

NASA Astrophysics Data System (ADS)

Differences between trends in different radiosonde temperature products resulting from the varying choices made by the developers of the data sets create obstacles for use of those products in climate change detection and attribution. To clarify the causes of these differences, one must examine results using a common subset of locations to minimize spatial sampling effects. When this is done for the Lanzante-Klein-Seidel (LKS) and Hadley Center (HadRT) radiosonde data sets, differences are reduced by at least one third. Differing homogeneity adjustment methods and differences in the source data are both important factors contributing to the remaining discrepancies. In contrast, subsampling the microwave sounding unit (MSU) satellite data sets according to the radiosonde coverage does not generally bring the trends in the satellite data closer to those in the radiosonde data so that adjustments and other processing differences appear to be the predominant sources of satellite-radiosonde discrepancies. Experiments in which we subsample globally complete data sets provide additional insight into the role of sampling errors. In the troposphere, spatial sampling errors are frequently comparable to the trends for 1979-1997, while in the stratosphere the errors are generally small relative to the trends. Sampling effects estimated from National Centers for Environmental Prediction reanalysis and MSU satellite data for seven actual radiosonde networks show little consistent relation between sampling error and network size. These results may have significant implications for the design of future climate monitoring networks. However, estimates of sampling effects using the reanalysis and the satellite data sets differ noticeably from each other and from effects estimated from actual radiosonde data, suggesting that these globally complete data sets may not fully reproduce actual sampling effects.

Free, Melissa; Seidel, Dian J.

2005-04-01

193

Temperature dependence of linear electrooptic coefficients r 113 and r 333 in lithium niobate  

NASA Astrophysics Data System (ADS)

A new method of determination of individual linear electrooptic coefficients is proposed. The technique is based on the dynamic polarimetric measurements and takes into consideration the temperature dependences of ordinary and extraordinary refractive indices. Results obtained for the electrooptic coefficients r113 and r333 in LiNbO3 are presented. The coefficients are found to increase significantly within the considered temperature range 25-200°C. The temperature dependences of the intrinsic coefficients m113 and m333, defined in terms of the induced polarisation, are considered as well.

Górski, P.; Ledzion, R.; Bondarczuk, K.; Kucharczyk, W.

2008-03-01

194

Split Stirling linear cryogenic cooler for a new generation of high temperature infrared imagers  

NASA Astrophysics Data System (ADS)

Split linear cryocoolers find use in a variety of infrared equipment installed in airborne, heliborne, marine and vehicular platforms along with hand held and ground fixed applications. An upcoming generation of portable, high-definition night vision imagers will rely on the high-temperature infrared detectors, operating at elevated temperatures, ranging from 95K to 200K, while being able to show the performance indices comparable with these of their traditional 77K competitors. Recent technological advances in industrial development of such high-temperature detectors initialized attempts for developing compact split Stirling linear cryogenic coolers. Their known advantages, as compared to the rotary integral coolers, are superior flexibility in the system packaging, constant and relatively high driving frequency, lower wideband vibration export, unsurpassed reliability and aural stealth. Unfortunately, such off-the-shelf available linear cryogenic coolers still cannot compete with rotary integral rivals in terms of size, weight and power consumption. Ricor developed the smallest in the range, 1W@95K, linear split Stirling cryogenic cooler for demanding infrared applications, where power consumption, compactness, vibration, aural noise and ownership costs are of concern.

Veprik, A.; Zechtzer, S.; Pundak, N.

2010-04-01

195

Linearity, climate sensitivity and climate changes in the surface temperature field  

NASA Astrophysics Data System (ADS)

The relationship between equilibrium global mean temperature, Te, and applied radiative forcing, Rf, is commonly expressed by the linear equation (Gregory et al., Roe and Baker): ?Te = ? Rf where ? is a constant known as the feedback parameter. Here we address the question of whether the relationship between Te and Rf is, in fact, well quantified by such a linear equation. Our analysis is based on the output of a global climate model. If the relationship breaks down when moving from a single equation model to a complicated global circulation model it is unlikely to reassert itself in the real world with all its additional complexity. Thus nonlinearity in the model can be taken as a strong indication of nonlinearity in reality, while linearity in a model might only be taken as a weak indication of linearity in reality. Thanks to the support of the climateprediction.net team and participants, we were able to run large (>500 members) initial condition ensembles with a global climate model (HadSM3) at seven values of Rf. Results will be presented demonstrating the nonlinear nature of the Te, Rf relationship. The term "linear" is used with a number of different meanings, leading to confusion in discussions between the many disciplines involved in climate science research. Furthermore, in the high-dimensional space of climate model output, linearity with Rf can be achieved in a variety of ways: for instance, linearity in magnitude of change (as in the equation above), linearity in degree of rotation within the high-dimensional model state space, linear change in variance in each dimension. These will be illustrated. Analysis of the above ensembles will be used to show that not only is the model nonlinear in the scalar global mean temperature, but also in the pattern of change. These results imply key messages for ensemble design. Most crucial is consideration of larger initial condition ensembles than is typical in climate model experiments. Such ensembles allow the reduction of sampling errors to levels sufficient to identify nonlinear responses within the model. The ensembles used in this research can provide guidance on the minimum ensemble size necessary to answer a variety of policy relevant questions. This will be illustrated in terms of the minimum ensemble size necessary to identify the nonlinear response in equilibrium global mean temperature.

Stainforth, D. A.; Smith, L. A.

2012-04-01

196

A Linearization Time-Domain CMOS Smart Temperature Sensor Using a Curvature Compensation Oscillator.  

PubMed

This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a -40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT). Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm2 in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of -1.2 to 0.2 °C is achieved in an operation range of -40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s. PMID:23989825

Chen, Chun-Chi; Chen, Hao-Wen

2013-08-28

197

Power-law persistence and trends in the atmosphere: a detailed study of long temperature records.  

PubMed

We use several variants of the detrended fluctuation analysis to study the appearance of long-term persistence in temperature records, obtained at 95 stations all over the globe. Our results basically confirm earlier studies. We find that the persistence, characterized by the correlation C(s) of temperature variations separated by s days, decays for large s as a power law, C(s) approximately s(-gamma). For continental stations, including stations along the coastlines, we find that gamma is always close to 0.7. For stations on islands, we find that gamma ranges between 0.3 and 0.7, with a maximum at gamma=0.4. This is consistent with earlier studies of the persistence in sea surface temperature records where gamma is close to 0.4. In all cases, the exponent gamma does not depend on the distance of the stations to the continental coastlines. By varying the degree of detrending in the fluctuation analysis we obtain also information about trends in the temperature records. PMID:14683028

Eichner, J F; Koscielny-Bunde, E; Bunde, A; Havlin, S; Schellnhuber, H-J

2003-10-28

198

Surface-temperature trends and variability in the low-latitude North Atlantic since 1552  

NASA Astrophysics Data System (ADS)

Sea surface temperature variability in the North Atlantic Ocean recorded since about 1850 has been ascribed to a natural multidecadal oscillation superimposed on a background warming trend. It has been suggested that the multidecadal variability may be a persistent feature, raising the possibility that the associated climate impacts may be predictable. However, our understanding of the multidecadal ocean variability before the instrumental record is based on interpretations of high-latitude terrestrial proxy records. Here we present an absolutely dated and annually resolved record of sea surface temperature from the Bahamas, based on a 440-year time series of coral growth rates. The reconstruction indicates that temperatures were as warm as today from about 1552 to 1570, then cooled by about 1?C from 1650 to 1730 before warming until the present. Our estimates of background variability suggest that much of the warming since 1900 was driven by anthropogenic forcing. Interdecadal variability with a period of 15-25years is superimposed on most of the record, but multidecadal variability becomes significant only after 1730. We conclude that the multidecadal variability in sea surface temperatures in the low-latitude western Atlantic Ocean may not be persistent, potentially making accurate decadal climate forecasts more difficult to achieve.

Saenger, Casey; Cohen, Anne L.; Oppo, Delia W.; Halley, Robert B.; Carilli, Jessica E.

2009-07-01

199

Multi-decadal variability and trends in the temperature of the northwest European continental shelf: A model-data synthesis  

NASA Astrophysics Data System (ADS)

We examine the trends and variability in temperature of the northwest European shelf seas over the period 1960-2004 using four approaches: a regional model simulation (using the Proudman Oceanographic Laboratory Coastal Ocean Modelling System; POLCOMS), in situ multi-annual timeseries observations, satellite remote sensed (AVHRR) sea surface temperature (SST), and an analysis of data held in an international database at the International Council for the Exploration of the Sea (ICES). We focus on variability for the full period and trends from 1985 to 2004, being limited by the length of model simulation and the availability of satellite data. We find that all data sources give a consistent picture, with both trends and variability being intensified on-shelf and north of ˜48°N. The model and AVHRR SST show statistically significant warming trends in large areas of this region that are clearly distinguishable from both model/observation error and natural variability on these timescales. This 'signal to noise ratio' is substantially reduced when near bottom temperatures are considered in the model. The long timeseries at Port Erin (Isle of Man) shows that the variation in trend is well represented by the model and that the warming trend in the period 1985-2004 is substantially larger and of longer duration than previous peaks in 20-year trends since 1914.We find that the SST trends are greater in the model and satellite observations than the air temperature trends in the ERA40 re-analysis used for forcing; the net sea to air heat flux is ˜20% less in 1985-2004 than 1960-1984 (including shortwave, longwave, sensible and latent components). This is partly compensated by a ˜9% reduction in advective warming. The model shows the trends in seasonally stratified regions are greater at the surface than at depth, indicating an increase in this stratification. While this pattern is also seen in the annual trends from the ICES data analysis, the lack of seasonal resolution hampers a quantitative corroboration.The model is seen to have good skill in reproducing both the trends and variability, but tends to underestimate the trends. The modelled variability is overestimated in some coastal and open ocean regions and underestimated elsewhere, while the phase of this variability is generally well represented. Generally the model performance is better on-shelf than in the open ocean.

Holt, Jason; Hughes, Sarah; Hopkins, Joanne; Wakelin, Sarah L.; Penny Holliday, N.; Dye, Stephen; González-Pola, César; Hjøllo, Solfrid Sætre; Mork, Kjell Arne; Nolan, Glen; Proctor, Roger; Read, Jane; Shammon, Theresa; Sherwin, Toby; Smyth, Tim; Tattersall, Graham; Ward, Ben; Wiltshire, Karen Helen

2012-11-01

200

Temperature modulated differential scanning calorimetry: on system linearity and the effect of kinetic events on the observed sample specific heat  

Microsoft Academic Search

In this paper, the effect of system linearity and kinetic events on heat capacity measurement by temperature modulated differential scanning calorimetry (TMDSC) is analyzed based on the thermal conduction differential equations that have been linearized assuming small kinetic perturbations. Numerical simulation of a first order reaction is used to demonstrate the importance of system linearity and the selection of experimental

S. X Xu; Y Li; Y. P Feng

2000-01-01

201

High-dynamic-range VGA with temperature compensation and linear-in-dB gain control  

Microsoft Academic Search

This paper presents the design and measured performance of a novel intermediate-frequency variable-gain amplifier for wideband code-division multiple access transmitters. A compensation technique for parasitic coupling is proposed which allows a high dynamic range of 77 dB to be attained at 400 MHz while using a single variable-gain stage. Temperature compensation and decibel-linear characteristics are achieved by means of a

Francesco Carrara; Carmelo Santagati; Giuseppe Palmisano

2004-01-01

202

Statistical analysis of stratospheric temperature and ozone profile data for trends and model comparison. Final report, 1 July 1990-30 June 1992  

SciTech Connect

Work performed during the project period July 1, 1990 to June 30, 1992 on the statistical analysis of stratospheric temperature data, rawinsonde temperature data, and ozone profile data for the detection of trends is described. Our principal topics of research are trend analysis of NOAA stratospheric temperature data over the period 1978-1989; trend analysis of rawinsonde temperature data for the period 1964-1988; trend analysis of Umkehr ozone profile data for the period 1977-1991; and comparison of observed ozone and temperature trends in the lower stratosphere. Analysis of NOAA stratospheric temperature data indicates the existence of large negative trends at 0.4 mb level, with magnitudes increasing with latitudes away from the equator. Trend analysis of rawinsonde temperature data over 184 stations shows significant positive trends about 0.2 C per decade at surface to 500 mb range, decreasing to negative trends about -0.3 C at 100 to 50 mb range, and increasing slightly at 30 mb level. There is little evidence of seasonal variation in trends. Analysis of Umkehr ozone data for 12 northern hemispheric stations shows significant negative trends about -.5 percent per year in Umkehr layers 7-9 and layer 3, but somewhat less negative trends in layers 4-6. There is no pronounced seasonal variation in trends, especially in layers 4-9. A comparison was made of empirical temperature trends from rawinsonde data in the lower stratosphere with temperature changes determined from a one-dimensional radiative transfer calculation that prescribed a given ozone change over the altitude region, surface to 50 km, obtained from trend analysis of ozonsonde and Umkehr profile data. The empirical and calculated temperature trends are found in substantive agreement in profile shape and magnitude.

Tiao, G.C.

1992-11-01

203

Trends in the design of front-end systems for room temperature solid state detectors  

SciTech Connect

The paper discusses the present trends in the design of low-noise front-end systems for room temperature semiconductor detectors. The technological advancement provided by submicron CMOS and BiCMOS processes is examined from several points of view. The noise performances are a fundamental issue in most detector applications and suitable attention is devoted to them for the purpose of judging whether or not the present processes supersede the solutions featuring a field-effect transistor as a front-end element. However, other considerations are also important in judging how well a monolithic technology suits the front-end design. Among them, the way a technology lends itself to the realization of additional functions, for instance, the charge reset in a charge-sensitive loop or the time-variant filters featuring the special weighting functions that may be requested in some applications of CdTe or CZT detectors.

Manfredi, Pier F.; Re, Valerio

2003-10-07

204

Amplification of surface temperature trends and variability in the tropical atmosphere.  

PubMed

The month-to-month variability of tropical temperatures is larger in the troposphere than at Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations and is consistent with basic theory. On multidecadal time scales, tropospheric amplification of surface warming is a robust feature of model simulations, but it occurs in only one observational data set. Other observations show weak, or even negative, amplification. These results suggest either that different physical mechanisms control amplification processes on monthly and decadal time scales, and models fail to capture such behavior; or (more plausibly) that residual errors in several observational data sets used here affect their representation of long-term trends. PMID:16099951

Santer, B D; Wigley, T M L; Mears, C; Wentz, F J; Klein, S A; Seidel, D J; Taylor, K E; Thorne, P W; Wehner, M F; Gleckler, P J; Boyle, J S; Collins, W D; Dixon, K W; Doutriaux, C; Free, M; Fu, Q; Hansen, J E; Jones, G S; Ruedy, R; Karl, T R; Lanzante, J R; Meehl, G A; Ramaswamy, V; Russell, G; Schmidt, G A

2005-08-11

205

Amplification of Surface Temperature Trends and Variability in the Tropical Atmosphere  

NASA Astrophysics Data System (ADS)

The month-to-month variability of tropical temperatures is larger in the troposphere than at Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations and is consistent with basic theory. On multidecadal time scales, tropospheric amplification of surface warming is a robust feature of model simulations, but it occurs in only one observational data set. Other observations show weak, or even negative, amplification. These results suggest either that different physical mechanisms control amplification processes on monthly and decadal time scales, and models fail to capture such behavior; or (more plausibly) that residual errors in several observational data sets used here affect their representation of long-term trends.

Santer, B. D.; Wigley, T. M. L.; Mears, C.; Wentz, F. J.; Klein, S. A.; Seidel, D. J.; Taylor, K. E.; Thorne, P. W.; Wehner, M. F.; Gleckler, P. J.; Boyle, J. S.; Collins, W. D.; Dixon, K. W.; Doutriaux, C.; Free, M.; Fu, Q.; Hansen, J. E.; Jones, G. S.; Ruedy, R.; Karl, T. R.; Lanzante, J. R.; Meehl, G. A.; Ramaswamy, V.; Russell, G.; Schmidt, G. A.

2005-09-01

206

Flame temperature trends in reacting vanadium and tungsten ethoxide fluid sprays during CO2-laser pyrolysis  

NASA Astrophysics Data System (ADS)

We observe the "invisible-to-the-naked-eye" flames of tungsten and vanadium ethoxide aerosols when ignited at moderate laser excitation (0< P laser<70 W) by employing an IR thermo-graphic camera. No emission is seen in the visible range whether by the visible region cameras or by spectroscopy. The emissivity of the precursor solution measured was 0.80 and 0.75 for tungsten and vanadium ethoxide, respectively. The spectral emissivities of the tungsten and vanadium ethoxide flames measured using FTIR-spectrometer were used to calculate the pyrolysis flame temperature at various laser intensities and wavelengths. New energy balance equations have been derived—the transient temperature one extended from Haggerty-Cannon equation and the other based on standard resonance analysis. Fitting these models to experimental data reveals that only small amounts (1.33% and 4.32%, respectively) of the laser power are used in the pyrolysis of the precursor ethoxide aerosols into the desired oxide nanostructures. The low levels of specific heat capacity values obtained in these sprays suggest that these are electronic heat capacities rather than lattice heat capacities; enthalpies are also obtained. The experimental temperature-laser power trends observed were in agreement with previous findings from Tenegal et al. (Chem. Phys. Lett. 335:155, 2001). The damping coefficients, and hence the saturation intensities confirm that the vanadium containing precursor liquid is harder to dissociate into final products than the tungsten precursor as observed experimentally.

Mwakikunga, B. W.; Mudau, A. E.; Brink, N.; Willers, C. J.

2011-11-01

207

Linearization of the fundamental integral equation for the thermomicrowave imaging of temperature profiles of the atmosphere. Part II  

Microsoft Academic Search

Using the apparatus of functional derivatives, we linearize the basic integral equation which is used to find the altitude temperature profile of the atmosphere by thermomicrowave imaging from above (from an aircraft or from outer space). The obtained Hnearized equation differs from the existing (incorrect) linearized equation used for the radar imaging of temperature profiles by wavelengths in the oxygen

S. A. Zhevakin

1981-01-01

208

Coastal sea surface temperature warming trend along the continental part of the Atlantic Arc (1985–2005)  

Microsoft Academic Search

Coastal warming was analyzed by means of satellite-derived sea surface temperature (SST) along the continental part of the Atlantic Arc extending from 37°N to 48°N for the period 1985–2005. Interannual SST variability calculated from anomalies shows an inhomogeneous warming trend in coastal SST (?SST). Coastal warming trend ranges from 3.5°C 100 a?1 at latitudes close to 48°N to 1.2°C 100

Moncho Gómez-Gesteira; Maite deCastro; Inés Alvarez; José Luis Gómez-Gesteira

2008-01-01

209

30-Year Mid-Tropospheric Temperature Trends over the Polar Regions Using MSU/AMSU-A Data  

NASA Astrophysics Data System (ADS)

The Polar Regions play important roles in global climate change. The Arctic is experiencing the greatest rates of change during the past decades compared to other regions. The Microwave Sounding Unit (MSU) and Advanced Microwave Sounding Unit A (AMSU-A) onboard the National Oceanic and Atmospheric Administration (NOAA) and the European Meteorological Operational satellite programme (MetOp) satellites provide unique long-term measurements for monitoring atmospheric temperature trends. However, trends derived from MSU/AMSU-A observations are still under debate until today. Moreover, previous studies used limited data and few works focused on the Polar Regions. In this study, we investigated the mid-tropospheric temperature trends over the Polar Regions using 30-year MSU/AMSU-A observations (Nov. 1978 - Jun. 2009, NOAA-TIROS N through NOAA-18 and MetOp-A). Calibration error is a major source of uncertainty because the intersatellite biases between different sensors can be as large as 1 K in the NOAA operational calibrated L1B products. We used the NOAA/NESDIS/STAR reprocessed/recalibrated L1C datasets based on Simultaneous Nadir Overpass (SNO) intercalibration method (Zou et al., 2009, Zou et al., 2006). It reduces intersatellite biases by up to an order of magnitude compared to pre-launch calibration by using a more accurate estimation of the sensor nonlinearity. Mid-tropospheric temperature trends over the Arctic (60° N - 82.5° N) and Antarctic (60° S - 82.5° S) were analyzed using the well-merged time series for MSU channel 2 and AMSU-A channel 5. Our results indicated the Arctic has warmed by 0.31 K/Decade during the past 30 years, more than two times the rate of global warming trend. The Antarctic has cooled by -0.10 K/Decade. Fig. 1 (a) and (b) show the spatial patterns of mid-tropospheric temperature trends from Nov. 1978 to Jun. 2009. Warming trends prevail over the Arctic, contrasted by the general cooling trends over the Antarctic. Significant warming occurred over the Arctic from Jan. 1987 to Sep. 2006, with trends larger than 0.8 K/Decade over portions of the Greenland, Baffin Bay, and Baffin Island. The Antarctic Continent and western/southern Southern Ocean also show warming trends during this 10-year period. Fig. 1 Spatial patterns of MSU/AMSU-A mid-tropospheric temperature trends over the Polar Regions.

Wang, W.; Zou, C.

2009-12-01

210

Piezoresistive Sensitivity, Linearity and Resistance Time Drift of Polysilicon Nanofilms with Different Deposition Temperatures  

PubMed Central

Our previous research work indicated that highly boron doped polysilicon nanofilms (?100 nm in thickness) have higher gauge factor (the maximum is ?34 for 80 nm-thick films) and better temperature stability than common polysilicon films (? 200nm in thickness) at the same doping levels. Therefore, in order to further analyze the influence of deposition temperature on the film structure and piezoresistance performance, the piezoresistive sensitivity, piezoresistive linearity (PRL) and resistance time drift (RTD) of 80 nm-thick highly boron doped polysilicon nanofilms (PSNFs) with different deposition temperatures were studied here. The tunneling piezoresistive model was established to explain the relationship between the measured gauge factors (GFs) and deposition temperature. It was seen that the piezoresistance coefficient (PRC) of composite grain boundaries is higher than that of grains and the magnitude of GF is dependent on the resistivity of grain boundary (GB) barriers and the weight of the resistivity of composite GBs in the film resistivity. In the investigations on PRL and RTD, the interstitial-vacancy (IV) model was established to model GBs as the accumulation of IV pairs. And the recrystallization of metastable IV pairs caused by material deformation or current excitation is considered as the prime reason for piezoresistive nonlinearity (PRNL) and RTD. Finally, the optimal deposition temperature for the improvement of film performance and reliability is about 620 °C and the high temperature annealing is not very effective in improving the piezoresistive performance of PSNFs deposited at lower temperatures.

Shi, Changzhi; Liu, Xiaowei; Chuai, Rongyan

2009-01-01

211

Trends and variability of daily and extreme temperature and precipitation in the Caribbean region, 1961-2010  

NASA Astrophysics Data System (ADS)

A workshop was held at the University of the West Indies, Jamaica, in May 2012 to build capacity in climate data rescue and to enhance knowledge about climate change in the Caribbean region. Scientists brought their daily surface temperature and precipitation data for an assessment of quality and homogeneity and for the preparation of climate change indices helpful for studying climate change in their region. This study presents the trends in daily and extreme temperature and precipitation indices in the Caribbean region for records spanning the 1961-2010 and 1986-2010 intervals. Overall, the results show a warming of the surface air temperature at land stations. Region-wide, annual means of the daily minimum temperatures (+1.4°C) have increased more than the annual means of the daily maximum temperatures (+0.95°C) leading to significant decrease in the diurnal temperature range. The frequency of warm days and warm nights has increased by more than 15% while 7% fewer cool days and 10% fewer cool night were found over the 50-year interval. These frequency trends are further reflected in a rise of the annual extreme high and low temperatures by ~1°C. Changes in precipitation indices are less consistent and the trends are generally weak. Small positive trends were found in annual total precipitation, daily intensity, maximum number of consecutive dry days and heavy rainfall events particularly during the period 1986-2010. Finally, aside from the observed climate trends, correlations between these indices and the Atlantic Multidecadal Oscillation (AMO) annual index suggest a coupling between land temperature variability and, to a lesser extent, precipitation extremes on the one hand, and the AMO signal of the North Atlantic surface sea temperatures.

Stephenson, Tannecia; Vincent, Lucie; Allen, Theodore; Van Meerbeeck, Cedric; McLean, Natalie

2013-04-01

212

Temperature trends in the tropical upper troposphere and lower stratosphere: Connections with sea surface temperatures and implications for water vapor and ozone  

NASA Astrophysics Data System (ADS)

Satellite observations and chemistry-climate model experiments are used to understand the zonal structure of tropical lower stratospheric temperature, water vapor, and ozone trends. The warming in the tropical upper troposphere over the past 30 years is strongest near the Indo-Pacific warm pool, while the warming trend in the western and central Pacific is much weaker. In the lower stratosphere, these trends are reversed: the historical cooling trend is strongest over the Indo-Pacific warm pool and is weakest in the western and central Pacific. These zonal variations are stronger than the zonal-mean response in boreal winter. Targeted experiments with a chemistry-climate model are used to demonstrate that sea surface temperature (hereafter SST) trends are driving the zonal asymmetry in upper tropospheric and lower stratospheric tropical temperature trends. Warming SSTs in the Indian Ocean and in the warm pool region have led to enhanced moist heating in the upper troposphere, and in turn to a Gill-like response that extends into the lower stratosphere. The anomalous circulation has led to zonal structure in the ozone and water vapor trends near the tropopause, and subsequently to less water vapor entering the stratosphere. The radiative impact of these changes in trace gases is smaller than the direct impact of the moist heating. Projected future SSTs appear to drive a temperature and water vapor response whose zonal structure is similar to the historical response. In the lower stratosphere, the changes in water vapor and temperature due to projected future SSTs are of similar strength to, though slightly weaker than, that due directly to projected future CO2, ozone, and methane.

Garfinkel, C. I.; Waugh, D. W.; Oman, L. D.; Wang, L.; Hurwitz, M. M.

2013-09-01

213

Rapid Warming of the World's Lakes: A Global Assessment of Recent Lake Temperature Trends Using In Situ and Satellite-Based Records  

NASA Astrophysics Data System (ADS)

Recent studies have revealed significant warming of lakes throughout the world, and the observed rate of lake warming is - in many cases - more rapid than that of the ambient air temperature. These large changes in lake temperature have profound implications for lake hydrodynamics, productivity, and biotic communities. The scientific community is just beginning to understand the global extent, regional patterns, physical mechanisms, and ecological consequences of lake warming. Although many in situ lake temperature records are available, only a few encompass long time periods. Most datasets are collected by individual investigators, have varying sampling protocols, and do not have extensive geographic or temporal coverage. Remote sensing methods, on the other hand, have been increasingly used to characterize global trends in lake surface temperature, and they provide an invaluable counterpart to in situ measurements. However, the existing satellite records do not extend as far back in time as some of the longer in situ datasets, and remotely sensed measurements capture only surface temperature, rather than vertical profiles. In this study, we present initial results from an international collaborative effort to synthesize global records of lake temperature from in situ and satellite-based measurements. Surface water temperature data are analyzed from over 120 lakes distributed across 40 countries. Data from 20 of the lakes are based on in situ measurements, while the remaining 100+ lake temperature records are obtained from satellite-based methods. We focus primarily on mean summer water temperatures for the 25-year period 1985-2009, as this provides a common time period with the largest amount of available data. Linear regression analysis reveals that 65% of the lakes in the database are experiencing significant summertime warming (p < 0.1), with another 30% warming at a rate that is not statistically significant. Only 5% of the lakes in the database show cooling trends (none of which are significant). The in situ and satellite-based measurements show a very similar distribution of water temperature trends among lakes, with a mean value of approximately +0.5 °C/decade and standard deviation of +/-0.3 °C/decade (maximum = +1.0 °C/decade). We also examine a variety of external controlling factors (e.g., air temperature, solar radiation, latitude, and lake depth) to understand the physical mechanisms associated with the global and regional patterns of lake warming.

Lenters, J. D.; Adrian, R.; Allan, M.; de Eyto, E.; Hamilton, D. P.; Hook, S.; Izmestyeva, L.; Kraemer, B.; Kratz, T.; Livingstone, D.; Mcintyre, P.; Montz, P.; Noges, P.; Noges, T.; O'Reilly, C.; Read, J.; Sandilands, K.; Schindler, D.; Schneider, P.; Silow, E.; Straile, D.; Van Cleave, K.; Zhdanov, F.

2011-12-01

214

Split Stirling linear cryogenic cooler for high-temperature infrared sensors  

NASA Astrophysics Data System (ADS)

Infrared imagers play a vital role in the modern tactics of carrying out surveillance, reconnaissance, targeting and navigation operations. The cooled systems are known to be superior to their uncooled competitors in terms of working ranges, resolution and ability to distinguish/track fast moving objects in dynamic infrared scenes. These advantages are primarily due to maintaining the infrared focal plane arrays at cryogenic temperatures using mechanical closed cycle Stirling cryogenic coolers. Recent technological advances in industrial application of high-temperature (up to 200K) infrared detectors has spurred the development of linearly driven microminiature split Stirling cryogenic coolers having inherently longer life spans, lower vibration export and better aural stealth as compared to their rotary driven rivals. Moreover, recent progress in designing highly efficient "moving magnet" resonant linear actuators and dedicated smart electronics have enabled further improvements to the cooler size, weight, power consumption, cooldown time and ownership costs. The authors report on the development and project status of a novel microminiature split Stirling linear cryogenic cooler having a shortened to 19mm cold finger and a high driving frequency (90Hz). The cooler has been specifically designed for cooling 130K infrared sensors of future portable infrared imagers, where compactness, low steady-state power consumption and fast cool-down time are of primary concern.

Veprik, A.; Zehter, S.; Vilenchik, H.; Pundak, N.

2009-05-01

215

Trend and Variability of China Precipitation in Spring and Summer: Linkage to Sea Surface Temperatures.  

National Technical Information Service (NTIS)

Observational records in the past 50 years show an upward trend of boreal-summer precipitation over central eastern China and a downward trend over northern China. During boreal spring, the trend is upward over southeastern China and downward over central...

F. Yang K. M. Lau

2004-01-01

216

Temperature dependence and temporal trends of polychlorinated biphenyl congeners in the Great Lakes atmosphere  

SciTech Connect

As part of the Integrated Atmospheric Deposition Network (IADN), the authors have measured gas-phase polychlorinated biphenyl (PCB) concentrations in the atmosphere around the Great Lakes since November of 1990. In this paper, they use these data to explore the temperature and time dependencies of gas-phase PCB concentrations near Lakes Superior, Michigan, and Erie and in Chicago. Concentrations of individual PCB congeners were well correlated to temperature for the three remote sites using the Clausius-Clapeyron equation, but the calculated heats of surface-air exchange did not correlate (on a congener basis) with laboratory-measured heats of vaporization. On the other hand, the heats of surface-air exchange for PCB congeners measured in Chicago are well correlated with laboratory-measured heats of vaporization. The authors conclude that the gas-phase PCB concentrations measured at Chicago are controlled by short-range transport, but at the three remote sites, these concentrations are controlled by long-range transport. Gas-phase PCBs also exhibited decreasing concentrations over the period 1991--1997 near Lakes Michigan and Erie and in Chicago. Significant half-lives ranged from 0.5 to 7.5 years for individual congeners and 2.8 to 3.3 years for total PCBs. Gas-phase PCBs near Lake Superior showed no general trend in gas-phase concentration over this same time period.

Simcik, M.F.; Basu, I.; Hites, R.A. (Indiana Univ., Bloomington, IN (United States)); Sweet, C.W. (Illinois State Water Survey, Champaign, IL (United States))

1999-06-15

217

Circular and linear enhancement-mode 6H-SiC MOSFETs for high temperature applications  

NASA Astrophysics Data System (ADS)

Direct current measurements are performed up to 673K at circular and linear (shown in parenthesis) enhancement-mode metal oxide semiconductor field effect transistors (MOSFETs). These devices are fabricated on a p-type 6H-SiC epitaxial layer with a doping concentration NA ? 1 × 1016 cm-1. The n+ source/drain regions and the p+ regions for the channel stops are achieved by ion implantation of nitrogen and aluminum, respectively. Both MOSFET geometries show excellent output characteristics with a good saturation behavior even at elevated temperatures. The inversion layer mobility ?n extracted in the linear region is 38 cm2·V-1·s-1 (35 cm2·V-1·s-1) and reveals a weak dependence on temperature with a maximum of 46 cm2·V-1·s-1 (42 cm2·V-1·s-1) at about 473K. Regarding the transfer characteristics, the drain current ID can be well modulated by the gate-source voltage VGS resulting in an Ion/Loff-ratio of 108 (108) at 303K and 105 (106) at 673K. In the subthreshold regime, ID can be pinched off well below 10 pA with a subthreshold swing of 150 mV/decade (155 mV/decade) at room temperature. The threshold voltage VT as a function of temperature shows two linear sections with negative temperature coefficients of -6.8 mV·K-1 (-6.8 mV·K-1) from 303 to 423K and -2.5 mV·K-1 (-2.0 mV·K-1) from 423 to 673K. By measuring VT as a function of bulk-source voltage VBS at different temperatures, NA can be directly estimated at a transistor and gives 9.6 × 1015 cm-3 (9.8 × 1015 cm-3). The measured bulk Fermi potential ?f of the p-type epitaxial layer deviates less than 10% from the calculated value at a given temperature.

Schmid, U.; Sheppard, S. T.; Wondrak, W.

1999-03-01

218

Non-local gyrokinetic model of linear ion-temperature-gradient modes  

SciTech Connect

The non-local properties of anomalous transport in fusion plasmas are still an elusive topic. In this work, a theory of non-local linear ion-temperature-gradient (ITG) drift modes while retaining non-adiabatic electrons and finite temperature gradients is presented, extending the previous work [S. Moradi et al., Phys. Plasmas 18, 062106 (2011)]. A dispersion relation is derived to quantify the effects on the eigenvalues of the unstable ion temperature gradient modes and non-adiabatic electrons on the order of the fractional velocity operator in the Fokker-Planck equation. By solving this relation for a given eigenvalue, it is shown that as the linear eigenvalues of the modes increase, the order of the fractional velocity derivative deviates from two and the resulting equilibrium probability density distribution of the plasma, i.e., the solution of the Fokker-Planck equation, deviates from a Maxwellian and becomes Levy distributed. The relative effect of the real frequency of the ITG mode on the deviation of the plasma from Maxwellian is larger than from the growth rate. As was shown previously the resulting Levy distribution of the plasma may in turn significantly alter the transport as well.

Moradi, S.; Anderson, J. [Department of Applied Physics, Nuclear Engineering, Chalmers University of Technology and Euratom-VR Association, Goeteborg (Sweden)

2012-08-15

219

Linear and quadratic temperature dependence of electronic specific heat for cuprates  

NASA Astrophysics Data System (ADS)

We model cuprate superconductors as an infinite layered lattice structure which contains a fluid of paired and unpaired fermions (electrons or holes). Paired fermions, which are the superconducting carriers, are considered as noninteracting zero spin bosons (cuasi-particles) with a linear dispersion relation, which coexist with the unpaired fermions in a series of almost two dimensional slabs stacked in their perpendicular direction. The inter-slab penetrable planes are simulated by a Dirac comb potential in the direction in which the slabs are stacked, while paired and unpaired electrons (or holes) are free to move parallel to the planes. Paired fermions condense at a BEC critical temperature exhibiting a jump in their specific heat, which are taken as the experimental values of the superconducting critical temperature and the specific heat jump of YBaCuO7-x, to fix our model parameters: the plane impenetrability and the fraction of superconducting charge carrier. We straightforwardly obtain, near and under the superconducting temperature Tc, the linear (?eT) and the quadratic (?T^2) electronic specific heat terms, with ?e and ? in agreement with the latest experimental values reported.

Salas, P.; Sevilla, F. J.; Solis, M. A.

2013-03-01

220

Filter Radiometers as a Tool for Quality Assurance of Temperature Measurements with Linear Pyrometers  

NASA Astrophysics Data System (ADS)

Measurements made with a pyrometer are vulnerable to errors if the pyrometer is misaligned, inaccurately characterized, or malfunctioning. In this work, thermodynamic temperatures between 1,373 and 1,773 K were studied by measuring a variable-temperature blackbody with a linear pyrometer and four absolutely characterized filter radiometers. The filter radiometer measurements were done in the irradiance mode. In the first set of measurements, there was a 3-5 K difference between the pyrometer and the filter radiometer data. The cause was tracked to malfunctioning of the pyrometer, which was afterwards sent for repair on the basis of these results. In the second set of measurements, with the repaired pyrometer, the agreement of the temperature results was good, the mean difference being -0.41 K with a standard deviation of 0.52 K. The differences between the pyrometer and the filter radiometer temperature measurement results showed no temperature dependence. It was concluded that the filter radiometers used in the irradiance mode provided a straightforward method for the quality assurance of pyrometers.

Ojanen, M.; Ahtee, V.; Noorma, M.; Weckström, T.; Kärhä, P.; Ikonen, E.

2008-06-01

221

Seasonal and spatial heterogeneity of recent sea surface temperature trends in the Caribbean Sea and southeast Gulf of Mexico.  

PubMed

Recent changes in ocean temperature have impacted marine ecosystem function globally. Nevertheless, the responses have depended upon the rate of change of temperature and the season when the changes occur, which are spatially variable. A rigorous statistical analysis of sea surface temperature observations over 25 years was used to examine spatial variability in overall and seasonal temperature trends within the wider Caribbean. The basin has experienced high spatial variability in rates of change of temperature. Most of the warming has been due to increases in summer rather than winter temperatures. However, warming was faster in winter in the Loop Current area and the south-eastern Caribbean, where the annual temperature ranges have contracted. Waters off Florida, Cuba and the Bahamas had a tendency towards cooling in winter, increasing the amplitude of annual temperature ranges. These detailed patterns can be used to elucidate ecological responses to climatic change in the region. PMID:22406045

Chollett, Iliana; Müller-Karger, Frank E; Heron, Scott F; Skirving, William; Mumby, Peter J

2012-03-08

222

The effects of urbanization on temperature trends in different economic periods and geographical environments in northwestern China  

NASA Astrophysics Data System (ADS)

Using data collected from 22 urban and 65 rural meteorological stations in northwestern China between 1961 and 2009, this paper presents a study concerning the effects of urbanization on air temperature trends. To distinguish among the potential influences that stem from the economic development levels, population scales, and geographic environments of the cities in this region, the 49-year study period was divided into two periods: a period of less economic development, from 1961 to 1978, and a period of greater economic development, from 1979 to 2009. Each of the cities was classified as a megalopolis, large, or medium-small, depending on the population, and each was classified as a plateau, plain, or oasis city, depending on the surrounding geography. The differences in the air temperature trends between cities and the average of their rural counterparts were used to examine the warming effects of urbanization. The results of this study indicate that the magnitude of warming effects due to urbanization depends not only on a city's economic level, but also on the population scale and geographic environment of the city. The urbanization of most cities in northwestern China resulted in considerable negative warming effects during 1961-1978 but evidently positive effects during 1979-2009. The population scale of a city represents a significant factor: a city with a larger population has a stronger warming influence, regardless of whether the effect is negative or positive. Among the three geographic environments of the cities considered, plateaus and plains more significantly enhance warming effects than oases. The urban population trend has a very significant logarithm relationship with the urban temperature effect, but no clear relationships between urban temperature effects and city elevation were detected. The majority of the temperature trends, accounting for more than 60 % of the trends during 1961-2009, can be explained by natural factors, although urbanization has had some obvious effects on temperatures in northwestern China.

Fang, Feng; Guo, Junqin; Sun, Landong; Wang, Jing; Wang, Xinping

2013-06-01

223

Cluster solver for dynamical mean-field theory with linear scaling in inverse temperature.  

PubMed

Dynamical mean-field theory and its cluster extensions provide a very useful approach for examining phase transitions in model Hamiltonians and, in combination with electronic structure theory, constitute powerful methods to treat strongly correlated materials. The key advantage to the technique is that, unlike competing real-space methods, the sign problem is well controlled in the Hirsch-Fye (HF) quantum Monte Carlo used as an exact cluster solver. However, an important computational bottleneck remains; the HF method scales as the cube of the inverse temperature, ? . This often makes simulations at low temperatures extremely challenging. We present here a method based on determinant quantum Monte Carlo which scales linearly in ? , with a quadratic term that comes in to play for the number of time slices larger than hundred, and demonstrate that the sign problem is identical to HF. PMID:20866350

Khatami, E; Lee, C R; Bai, Z J; Scalettar, R T; Jarrell, M

2010-05-12

224

Competition of linearly polarized modes in fibers with Bragg gratings over a wide temperature range  

NASA Astrophysics Data System (ADS)

Fiber Bragg gratings (FBGs) embedded in conventional fibers may serve as temperature sensors over a wide temperature range and withstand temperatures around 1200 K. A variety of linearly polarized (LP) modes for the wavelengths between 400 and 700 nm may be sustained in fibers with and without FBGs. The composition of the LP modes and their competition is instrumental for understanding physics of thermo-optics and thermal expansion effects in silica-based fibers. The first objective of this work was to model mathematically the competition between LP modes and modal distribution using the solutions of Bessel equations for the fibers with and without the gratings. Computer generated modes were constructed and the cut-off V-numbers (and Eigen values W and U) were determined. Theoretical results then were compared with experimental observations of LP modes for two separate ranges of temperatures: 77- 300 K and 300-1200 K. To study the formation of LP modes over the first temperature range, liquid nitrogen was used to cool down the fiber and a thermocouple was used to monitor the temperature of the fiber. Real time recording of the modal structure was performed using digital imaging and data acquisition instrumentation. To study LP modes between 300- 1200 K, the fibers were inserted into a tube furnace with temperature control. The wavelength of the infrared radiation was reflected by a FBG and detected by an optical spectrum analyzer. Radiation at the visible wavelength propagated through the fibers, and transmitted visible light was collected, analyzed and recorded with a CCD camera to monitor distribution of the LP modes in the samples with and without the FBGs.

Lyuksyutov, Sergei; Adamovsky, Grigory; Mackey, Jeffrey R.; Floyd, Bertram; Abeywickrema, Ujitha; Fedin, Igor

2012-10-01

225

Implicit Integration by Linearization for High-Temperature Inelastic Constitutive Models  

NASA Astrophysics Data System (ADS)

In this study, a linearization method is used to develop an implicit integration scheme for a class of high-temperature inelastic constitutive models based on non-linear kinematic hardening. A non-unified model is first considered in which the inelastic strain rate is divided into transient and steady parts driven, respectively, by effective stress and applied stress. By discretizing the constitutive relations using the backward Euler method, and by linearizing the resulting discretized relations, a tensor equation is derived to iteratively achieve the implicit integration of constitutive variables. The implicit integration scheme developed is shown to be applicable to a unified constitutive model in which back stress evolves due to static and dynamic recoveries in addition to strain hardening. The integration scheme is then programmed for a subroutine in a finite element code and applied to a lead-free solder joint analysis. It is demonstrated that the integration scheme affords quadratic convergence in the iterations even for considerably large increments, and that the non-unified and unified models give almost the same results in the solder joint analysis.

Akamatsu, Masafumi; Nakane, Kazuhiko; Ohno, Nobutada

226

Trends in extreme daily rainfall and temperature in Southeast Asia and the South Pacific: 1961-1998  

Microsoft Academic Search

Trends in extreme daily temperature and rainfall have been analysed from 1961 to 1998 for Southeast Asia and the South Pacific. This 38-year period was chosen to optimize data availability across the region. Using high-quality data from 91 stations in 15 countries, significant increases were detected in the annual number of hot days and warm nights, with significant decreases in

M. J. Manton; P. M. della-Marta; M. R. Haylock; K. J. Hennessy; N. Nicholls; L. E. Chambers; D. A. Collins; G. Daw; A. Finet; D. Gunawan; K. Inape; H. Isobe; T. S. Kestin; P. Lefale; C. H. Leyu; T. Lwin; L. Maitrepierre; N. Ouprasitwong; C. M. Page; J. Pahalad; N. Plummer; M. J. Salinger; R. Suppiah; V. L. Tran; B. Trewin; I. Tibig; D. Yee

2001-01-01

227

Elevation dependency of recent and future minimum surface air temperature trends in the Tibetan Plateau and its surroundings  

Microsoft Academic Search

Elevation dependency of climate change signals has been found over major mountain ranges such as the European Alps and the Rockies, as well as over the Tibetan Plateau. In this study we examined the temporal trends in monthly mean minimum temperatures from 116 weather stations in the eastern Tibetan Plateau and its vicinity during 1961–2006. We also analyzed projected climate

Xiaodong Liu; Zhigang Cheng; Libin Yan; Zhi-Yong Yin

2009-01-01

228

Trends in Temperature, Secchi Depth, and Dissolved Oxygen Depletion Rates in the Central Basin of Lake Erie, 1983–2002  

Microsoft Academic Search

We examined temperature trends in a 20-year set of monitoring records collected at multiple deep-water stations in the central basin of Lake Erie. Data collected were statistically corrected (“deseasonalized”) to remove biases resulting from irregular sampling intervals within years. Depthintegrated summer temperature has increased by an average (±SE) of 0.037 ± 0.01°C per year. An observed reduction of Secchi depth

Noel M. Burns; David C. Rockwell; Paul E. Bertram; David M. Dolan; Jan J. H. Ciborowski

2005-01-01

229

Occurrence, temperature and seasonal trends of ?- and ?-HCH in air (Québec, Canada)  

NASA Astrophysics Data System (ADS)

Atmospheric concentrations of ?- and ?-hexachlorocyclohexane (HCH) were measured during 1993-1995 along the St. Lawrence River in Québec, Canada. Average ?- and ?-HCH concentrations (pg/m 3) were St. Anicet: 93-101; Villeroy: 92-42; Mingan: 96-20, respectively. ?-HCH mean concentrations were similar in all sites and appeared to be more influenced by long-range transport than local sources. ?-HCH mean levels in St. Anicet were 2 and 5 times higher than in Villeroy and Mingan, respectively. The time-series of ?-HCH air concentrations at St. Anicet and Villeroy were characterised by highly elevated springtime episodes, which are in agreement with the ?-HCH usage in Québec as corn seed dressing pesticide. No temporal trend was observed for the ?-HCH in air. Clausius-Clapeyron plots (log conc. vs. 1/ T) showed a stronger correlation between temperature and measured ?-HCH concentrations at St. Anicet and Villeroy than Mingan. On a regional scale, the influence of the local sources of ?-HCH implied a seasonal variability in air concentrations due to its short transport, while at the background site (Mingan), the observed ?- and ?-HCH concentrations in air were the result of its long-range transport and/or water/air gas exchanges.

Garmouma, Mourad; Poissant, Laurier

230

A coral-based reconstruction of Atlantic sea surface temperature trends and variability since 1552 (Invited)  

NASA Astrophysics Data System (ADS)

North Atlantic sea-surface temperature (SST) variability can have a near global impact on climate. Observed variability has been described as a natural multidecadal (65-100 year) oscillation superimposed upon a linearly- increasing, externally-forced background warming. The multidecadal portion of this variability may be persistent, suggesting useful decadal climate predictions may soon be possible. However, our understanding of multidecadal Atlantic SST variability prior to the brief instrumental record relies almost exclusively on high latitude tree-ring proxies. No proxy SST reconstruction from the Atlantic itself has the resolution, dating accuracy and length needed to assess the behavior of multidecadal variability. We present the first absolutely dated and annually-resolved multi-centennial record of Atlantic sea surface temperature. Our 439-year coral-based reconstruction suggests western low-latitude Atlantic SSTs were nearly as warm as today from ~1552-1570 A.D., cooled by more than 1°C from ~1650-1730 A.D. and generally warmed to the present. Estimates of externally-forced background variability suggest that anthropogenic forcing can account for most of the warming since 1850 A.D. Multidecadal variations superimposed upon this background disappear prior to ~1730 A.D. in favor of interdecadal (15-20 year) variability. This suggests observed multidecadal variability is not persistent and may be difficult to predict.

Saenger, C. P.; Cohen, A. L.; Oppo, D.; Carilli, J.; Halley, R. B.

2009-12-01

231

A coral-based reconstruction of Atlantic sea surface temperature trends and variability since 1552  

NASA Astrophysics Data System (ADS)

North Atlantic sea-surface temperature (SST) variability can have a near global impact on climate. Observed variability has been described as a natural multidecadal (65-100 year) oscillation superimposed upon a linearly-increasing, externally-forced background warming. The multidecadal portion of this variability may be persistent, suggesting useful decadal climate predictions may soon be possible. However, our understanding of multidecadal Atlantic SST variability prior to the brief instrumental record relies almost exclusively on high latitude tree-ring proxies. No proxy SST reconstruction from the Atlantic itself has the resolution, dating accuracy and length needed to assess the behavior of multidecadal variability. We present the first absolutely dated and annually-resolved multi-centennial record of Atlantic sea surface temperature. Our 439-year coral-based reconstruction suggests western low-latitude Atlantic SSTs were nearly as warm as today from ~1552-1570 A.D., cooled by more than 1°C from ~1650-1730 A.D. and generally warmed to the present. Estimates of externally-forced background variability suggest that anthropogenic forcing can account for most of the warming since 1850 A.D. Multidecadal variations superimposed upon this background disappear prior to ~1730 A.D. in favor of interdecadal (15-20 year) variability. This suggests observed multidecadal variability is not persistent and may be difficult to predict.

Saenger, C.; Cohen, A. L.; Oppo, D. W.; Carilli, J.

2009-04-01

232

A low-distortion CMOS IF VGA with linear-in-dB control and temperature compensation  

Microsoft Academic Search

A CMOS intermediate-frequency (IF) variable-gain amplifier (VGA) is presented in this paper. A transconductance linearization\\u000a scheme is proposed for the VGA core based on a signal-subtracting structure to achieve low distortion. Temperature-independent\\u000a decibel-linear gain control characteristic is achieved by an exponential voltage generator based on transfer characteristics\\u000a of differential pair. The whole VGA, including a highly-linear output stage, is fabricated

Ting-Hua Yun; Li Yin; Cheng Huang; Jian-Hui Wu; Long-Xing Shi

2007-01-01

233

Linear Long-term Trend of Aerosol Optical Thickness from Satellite Retrievals using BAER over Several Regions  

NASA Astrophysics Data System (ADS)

Aerosol has been investigated by many scientists due to its potential effects on climate system. However, Aerosol Optical Thickness (AOT) retrieval over land is difficult because of high variability of surface reflectance. BAER (Bremen AErosol Retrieval) among well-developed algorithms has retrieved AOT successfully over land with different satellite data in previous studies. In this study, the long-term and seasonal trends of AOT over several regions has been studied by using BAER with SeaWiFS (Sea-viewing Wide Field-of-view Sensor) L1b data from late 1997 to May 2008. The EU CityZen project requested investigations in specific regions of interest, as these are BeNeLux, Po Valley, Eastern Europe, Eastern Mediterranean in Europe, and Pearl River Delta in South China because they are densely populated and mostly influenced by terrestrial aerosol sources (e.g. mineral dust, industrial pollutant, and biomass burning). AERONET level 2.0 (cloud-screened and quality-assured) data in 443 and 555 nm were used for the validation process. Furthermore, long-term trend of retrieved AOT was verified at AERONET sites (Forth Crete, Ispra, and Venise) located within the regions of interest. In general, negative tendencies in AOT were observed in most of European regions influenced by industrial pollutants, and the magnitude is up to -0.0039 per year. However, the AOT trend in the Pearl River Delta shows positive tendency because it is a fast developing region. The magnitude is up to +0.0065 per year. For more reliable analysis of long-term trend of AOT, further studies are necessary with other satellites, ground-based measurements, and numerical models.

Yoon, Jongmin; von Hoyningen-Huene, Wolfgang; Vountas, Marco; Burrows, John P.

2010-05-01

234

NW-trending linear gravity and magnetic features: Plate tectonics implications for the western Gulf of Mexico  

SciTech Connect

Gravity and magnetic maps have been interpreted and integrated with geological observations to investigate the linkage between deep sub-salt basement and shallow structures imaged seismically in the Mesozoic-Cenozoic marine section of southeast Texas. Shallow structures could have been inherited from sub-salt basement; e.g. shallow anticlines imaged below a detachment which approximately corresponds with the top of the Wilcox Formation may occur above basement highs. The sub-detachment anticlines probably occur where salt thickness variations mimic the syn-rifting topography. These anticlines formed when autochthonous salt withdrew and the Mesozoic-Cenozoic marine section was draped over sub-salt basement horsts. Salt probably accumulated due to thermal subsidence after rifting, and may partly have infilled some rift basins. Balanced cross-sections indicate that salt withdraw persisted until the Late Oligocene. The interpretation is based on the identification of NW-trending lineaments or alignments of magnetic and gravity anomalies. Lineaments are interpreted as rift-related transfer zones in sub-salt basement because (i) refraction data shot perpendicular to the lineaments indicates that basement relief has a NW -trending alignment, (ii) lineaments parallel the San Marcos Arch, (iii) lineaments occur in the same location on both gravity and magnetic maps, and (iv) transfer zones of Mesozoic graben systems penetrated onshore are NW-trending. NW-trending lineaments do not fan and have a very long radius of curvature; this suggests that the pole of rotation for the early opening of the Gulf of Mexico is located many thousands of kilometers to the northeast or southwest.

Heyn, T.; Jones, S. (BP Exploration, Houston, TX (United States))

1993-02-01

235

Long-term temperature trends in the deep waters of the Weddell Sea  

Microsoft Academic Search

Warming of the deep water in the Weddell Sea has important implications for Antarctic bottom water formation, melting of pack ice, and the regional ocean–atmosphere heat transfer. In order to evaluate warming trends in the Weddell Sea, a historical data set encompassing CTD and bottle data from 1912 to 2000 was analyzed for temporal trends in the deep water masses:

Robin Robertson; Martin Visbeck; Arnold L. Gordon; E. Fahrbach

2002-01-01

236

Long-term Temperature Trends in the Deep Waters of the Weddell Sea  

Microsoft Academic Search

Abstract Warming of the deep water in the Weddell Sea has important implications for Antarctic bottom water formation, melting of pack ice, and the regional ocean–atmosphere heat transfer. In order to evaluate warming trends in the Weddell Sea, a historical data set encompassing CTD and bottle data from 1912 to 2000 was analyzed for temporal trends in the deep water

Robin Robertson; Martin Visbeck; Arnold L. Gordon; E. Fahrbach

2001-01-01

237

Binary homogeneous nucleation: Temperature and relative humidity fluctuations and non-linearity  

SciTech Connect

This report discusses binary homogeneous nucleation involving H{sub 2}SO{sub 4} and water vapor is thought to be the primary mechanism for new particle formation in the marine boundary layer. Temperature, relative humidity, and partial pressure of H{sub 2}SO{sub 4} vapor are the most important parameters in fixing the binary homogeneous nucleation rate in the H{sub 2}SO{sub 4}/H{sub 2}O system. The combination of thermodynamic calculations and laboratory experiments indicates that this rate varies roughly as the tenth power of the saturation ratio of H{sub 2}SO{sub 4} vapor. Furthermore, the vapor pressure of H{sub 2}SO{sub 4} is a function of temperature, and similar dependencies of the binary homogeneous nucleation rate on relative humidity can be noted as well. These factors thus introduce strong non-linearities into the system, and fluctuations of temperature, relative humidity, and H{sub 2}SO{sub 4} vapor concentrations about mean values may strongly influence the nucleation rate measured in the atmosphere.

Easter, R.C. [Pacific Northwest Lab., Richland, WA (United States); Peters, L.K. [Kentucky Univ., Lexington, KY (United States). Dept. of Chemical Engineering

1993-01-01

238

Binary homogeneous nucleation: Temperature and relative humidity fluctuations and non-linearity  

SciTech Connect

This report discusses binary homogeneous nucleation involving H[sub 2]SO[sub 4] and water vapor is thought to be the primary mechanism for new particle formation in the marine boundary layer. Temperature, relative humidity, and partial pressure of H[sub 2]SO[sub 4] vapor are the most important parameters in fixing the binary homogeneous nucleation rate in the H[sub 2]SO[sub 4]/H[sub 2]O system. The combination of thermodynamic calculations and laboratory experiments indicates that this rate varies roughly as the tenth power of the saturation ratio of H[sub 2]SO[sub 4] vapor. Furthermore, the vapor pressure of H[sub 2]SO[sub 4] is a function of temperature, and similar dependencies of the binary homogeneous nucleation rate on relative humidity can be noted as well. These factors thus introduce strong non-linearities into the system, and fluctuations of temperature, relative humidity, and H[sub 2]SO[sub 4] vapor concentrations about mean values may strongly influence the nucleation rate measured in the atmosphere.

Easter, R.C. (Pacific Northwest Lab., Richland, WA (United States)); Peters, L.K. (Kentucky Univ., Lexington, KY (United States). Dept. of Chemical Engineering)

1993-01-01

239

Trend and variability of surface air temperature in northeastern Spain (1920-2006): Linkage to atmospheric circulation  

NASA Astrophysics Data System (ADS)

An assessment of long-term change and variability of temperature over northeastern Spain (1920-2006) is provided using a dataset of 19 observatories. In addition, a more detailed analysis of the spatial and temporal variability of maximum, minimum, and mean temperatures, and the diurnal temperature range (DTR) has also been carried out employing 128 observatories spanning the period from 1960 to 2006. In general, maximum, minimum, and mean temperatures have increased significantly, mainly from 1960. Contrarily, the DTR showed less coherent variability with both positive and negative trends. On a seasonal scale, the analysis reveals that the weakest trends (mostly insignificant at the 5% level) were observed during autumn, while the strongest warming rates were found during summer and spring. Spatially, the observed warming was more robust in the coastal proportions compared with mainland observatories. The trends on the annual timescale are spatially consistent with those observed in warm seasons (summer and spring) rather than in cold seasons (winter and autumn). This study also explores the forcing mechanisms that can explain temperature variability on seasonal timescales. This variability can markedly be connected to variations in the large-scale atmospheric patterns. Notably, the Eastern Atlantic (EA), the Scandinavian (SCA), and the Western Mediterranean Oscillation (WeMO) patterns exert a significant influence on temperature variations in the study domain. Our results confirm that circulation patterns have spatially variable influences on temperature on both seasonal and annual timescales. Changes in patterns of atmospheric flows, as driven by increase in zonal circulation and anticyclonic conditions in recent decades, seem to play a noticeable role to explain spatio-temporal variability of temperatures in the study domain.

El Kenawy, Ahmed; López-Moreno, Juan I.; Vicente-Serrano, Sergio M.

2012-03-01

240

Experimental Verification of the Linear Theory for Stimulated Raman Scattering in High-Temperature Hohlraum Plasmas  

SciTech Connect

We show that the measured stimulated Raman scattering (SRS) in a large-scale high-temperature plasma scales strongly with the plasma density, increasing by an order of magnitude when the electron density is increased by 20%. This is consistent with linear theory in a uniform plasma and will set the limit on drive laser beam intensity for forthcoming ignition experiments at the National Ignition Facility. Control of SRS at laser intensities consistent with 285 eV ignition hohlraums are achieved by using polarization smoothing which increases the intensity threshold for the onset of SRS by 1.6 {+-} 0.2. These results were quantitatively predicted by full beam 3-dimensional numerical laser-plasma interaction simulations.

Froula, D H; Divol, L; London, R A; Berger, R L; Doppner, T; Meezan, N B; Ross, J S; Suter, L J; Sorce, C; Glenzer, S H

2009-04-22

241

Directly Determined Linear Radii and Effective Temperatures of Giants from Long-Baseline Optical Interferometry  

NASA Astrophysics Data System (ADS)

A review of fundamental stellar parameters for giants as directly determined using long-baseline optical interferometry (LBI) will be presented. Special attention will be paid to the progression of precision over the years of the observables of linear radius and effective temperature, with the current state-of-the-art measures approaching sub-percent levels for hundreds of stars (and being limited primarily by the ancillary data products of distance and bolometric flux, not measured angular size). Discussion will also be presented on the diminishing meaning of these gross parameterizations of stellar atmospheres, as higher-order surface details such as limb darkening and spotting are beginning to be imaged with LBI.

van Belle, Gerard

2013-07-01

242

Phase Diagram of the Linear Sigma Model wiht Quarks at Finite Temperature and Density  

NASA Astrophysics Data System (ADS)

The study of QCD at low energies is relevant in explaining the world around us but is extremely difficult due to the mathematical structure of the theory. The linear sigma model is a well known and simple effective model for low-energy QCD. We couple the O(4) linear sigma model to quark fields in order to study the effects of the quarks and mesons on the chiral phase transition as functions of the temperature T and the quark chemical potential ?q. As an effective model for QCD, we hope to reproduce some aspects of the QCD phase diagram, namely, the line of first order transitions that has a critical end-point at a second order transiton. We study how this line varies with changing pion mass. We use the self-consistent Cornwall-Jackiw-Tomboulis method in an extended Hartree approximation using a summation over all daisy diagrams. We study the mesonic and quark properties, including mean field, fluctuations and effective masses and how they relate to the transition structure.

Bowman, Edwin; Kapusta, Joseph; Kolomeitsev, Evgeni

2008-04-01

243

Ozone and Temperature Trends in the Upper Stratosphere at Five Stations of the Network for the Detection of Atmospheric Composition Change  

NASA Astrophysics Data System (ADS)

We use comprehensive records of upper stratospheric (35 to 45~km) ozone and temperature from several space- and ground-based data sets at five stations of the Network for the Detection of Atmospheric Composition Change (NDACC), from 45°S to 48°N, and starting in 1979. The space based ozone records come from the Solar Backscatter Ultra-Violet (SBUV), Stratospheric Aerosol and Gas Experiments (SAGE I and II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). The ground-based records come from lidars and microwave radiometers at the NDACC stations. For temperature, European Centre for Medium Range Weather Forecast reanalyses (ERA-40), National Centers for Environmental Prediction (NCEP) operational analyses, and HALOE and lidar measurements are used. All data sets show essentially the same long-term variations, attributable to QBO, 11-year solar-cycle, anthropogenic chlorine and other trends. Monthly mean anomalies from the different data-sets typically agree within 5% for ozone, and within 3~K for temperature. From 1979 until the late 1990s, due to increasing anthropogenic chlorine, all available data-sets show a clear decline of ozone near 40~km, by 10% to 15%. This decline has not continued in the last 10~years. At some sites, ozone at 40~km even appears to have increased since 2000, consistent with the beginning decline of stratospheric chlorine. Temperatures near 40~km altitude have been fluctuating around a constant level at all five NDACC stations since about 1985. This non-decline of upper stratospheric temperatures would be a new and significant change from the more or less linear cooling of the upper stratosphere seen before the 1990s, and reported in previous trend assessments. Chemistry-climate model (CCM) simulations track the historical ozone anomalies and reproduce the change in ozone tendency in the late 1990s. The phaseout of chlorofluorocarbons after the 1987 International Montreal Protocol now shows positive effects on ozone in the upper stratosphere. However, due to increasing CO2, the CCMs simulate a continuous linear cooling by 1~K per decade over the entire 1979 to 2010 period. This is not consistent with the near-constant temperatures observed since the late 1980s.

Steinbrecht, W.; Claude, H.; Schönenborn, F.; McDermid, S.; Leblanc, T.; Godin-Beekmann, S.; Keckhut, P.; Hauchecorne, A.; van Gijsel, J. A.; Swart, D. P.; Bodeker, G. E.; Parrish, A.; Boyd, I. S.; Kämpfer, N.; Hocke, K.; Stolarski, R. S.; Frith, S. M.; Thomason, L. W.; Remsberg, E. E.; von~Savigny, C.; Burrows, J. P.; Eyring, V.; Shepherd, T. G.

2008-12-01

244

Development of a High Temperature and Radiation Resistant Linear Motion Servo Actuator System for Nuclear Reactor Control Rod Application  

Microsoft Academic Search

This paper discusses major problem areas encountered in the design, construction, and development of a servo actuator system for positioning the control rods of a nuclear ramjet engine test reactor. The actuator discussed is 40 inch linear stroke, electropneumatic servo actuator capable of operating throughout the temperature range of 70°F to 1200°F part temperature, using air as the power supply,

J. S. Sulich; M. H. Cardon

1962-01-01

245

Iterated Application of a Linear Inverse Temperature Model to Lake Michigan SSTs Generated by CH3D  

Microsoft Academic Search

A methodology is presented describing the adjustment of a Lake Michigan hydrodynamic simulation through iterated application of a linear inverse temperature model. CH3D, a numerical model developed by the U.S. Army Corps of Engineers, is used to generate Lake Michigan surface temperatures for Mar 14, 2000. The simulation is initiated from Jan 1, 2000 under hourly windstress observations using a

J. A. Shore; Y. Guo; K. W. Bedford

2002-01-01

246

Investigation of the low-temperature performance of asphalt mixtures via fatigue and linear contraction and creep test  

Microsoft Academic Search

Three types of asphalt mixtures, including asphalt concrete (AC), stone mastic asphalt (SMA) and porous asphalt (PA) with a 13mm gradation, are chosen to study the fatigue behavior, linear contraction and creep performance of them. The analysis of the experimental results is summarized as follows. The asphalt mixture exhibits longer fatigue life at low temperature than that at high temperature.

Conghui Liu; Shaopeng Wu; Bo Li; Jingang Wang

2008-01-01

247

An intercomparison of temperature trends in the U.S. Historical Climatology Network and recent atmospheric reanalyses  

NASA Astrophysics Data System (ADS)

Temperature trends over 1979-2008 in the U.S. Historical Climatology Network (HCN) are compared with those in six recent atmospheric reanalyses. For the conterminous United States, the trend in the adjusted HCN (0.327 °C dec-1) is generally comparable to the ensemble mean of the reanalyses (0.342 °C dec-1). It is also well within the range of the reanalysis trend estimates (0.280 to 0.437 °C dec-1). The bias adjustments play a critical role, as the raw HCN dataset displays substantially less warming than all of the reanalyses. HCN has slightly lower maximum and minimum temperature trends than those reanalyses with hourly temporal resolution, suggesting the HCN adjustments may not fully compensate for recent non-climatic artifacts at some stations. Spatially, both the adjusted HCN and all of the reanalyses indicate widespread warming across the nation during the study period. Overall, the adjusted HCN is in broad agreement with the suite of reanalyses.

Vose, Russell S.; Applequist, Scott; Menne, Matthew J.; Williams, Claude N., Jr.; Thorne, Peter

2012-05-01

248

Trends in mean and extreme rainfall in South Florida and their correlations with sea surface temperature anomalies  

NASA Astrophysics Data System (ADS)

Historical time series of daily rainfall in South Florida over the last half century were used to extract trends in mean and extreme rainfall, specifically, the trends in moving means, moving standard deviations and moving return levels. The Generalized Pareto Distribution developed within extreme value theory was used to compute the return levels within each moving window. The influence of threshold choice and missing value filling methods on the return levels were studied. Extreme value theory was applied to the entire time series after removing seasonality, while both mean and extreme trends were calculated by using wet and dry season data separately. The relation of mean and extreme rainfall in South Florida with sea surface temperature anomalies were investigated by computing correlations of a variety of indices corresponding to the latter with the moving mean, standard deviation and return levels of rainfall. New insights were obtained about the mean and extreme rainfall trends as well as their correlations with Atlantic and Pacific surface temperature anomalies.

Lai, E.; Steinhaeuser, K.; Ganguly, A. R.

2008-12-01

249

Elevation-Dependent Temperature Trends in the Rocky Mountain Front Range: Changes over a 56- and 20-Year Record  

PubMed Central

Determining the magnitude of climate change patterns across elevational gradients is essential for an improved understanding of broader climate change patterns and for predicting hydrologic and ecosystem changes. We present temperature trends from five long-term weather stations along a 2077-meter elevational transect in the Rocky Mountain Front Range of Colorado, USA. These trends were measured over two time periods: a full 56-year record (1953–2008) and a shorter 20-year (1989–2008) record representing a period of widely reported accelerating change. The rate of change of biological indicators, season length and accumulated growing-degree days, were also measured over the 56 and 20-year records. Finally, we compared how well interpolated Parameter-elevation Regression on Independent Slopes Model (PRISM) datasets match the quality controlled and weather data from each station. Our results show that warming signals were strongest at mid-elevations over both temporal scales. Over the 56-year record, most sites show warming occurring largely through increases in maximum temperatures, while the 20-year record documents warming associated with increases in maximum temperatures at lower elevations and increases in minimum temperatures at higher elevations. Recent decades have also shown a shift from warming during springtime to warming in July and November. Warming along the gradient has contributed to increases in growing-degree days, although to differing degrees, over both temporal scales. However, the length of the growing season has remained unchanged. Finally, the actual and the PRISM interpolated yearly rates rarely showed strong correlations and suggest different warming and cooling trends at most sites. Interpretation of climate trends and their seasonal biases in the Rocky Mountain Front Range are dependent on both elevation and the temporal scale of analysis. Given mismatches between interpolated data and the directly measured station data, we caution against an over-reliance on interpolation methods for documenting local patterns of climatic change.

McGuire, Chris R.; Nufio, Cesar R.; Bowers, M. Deane; Guralnick, Robert P.

2012-01-01

250

Linear thermal expansion, thermal ageing, relaxations and post-cure of thermoset polymer composites using modulated temperature thermomechanometry  

Microsoft Academic Search

The glass transition temperature (Tg) regions of polymers and composites were studied using static force thermomechanometry and modulated temperature thermomechanometry\\u000a (mT-TM). Modulated temperature allowed measurement of linear thermal expansion coefficient and glass transition as reversing\\u000a phenomena, independent of any residual cure and relaxations that are non-reversing in nature. The reversing dimension change\\u000a curves were well defined with continuous expansion that

Robert A. Shanks

251

An inverse analysis to estimate linearly temperature dependent thermal conductivity components and heat capacity of an orthotropic medium  

Microsoft Academic Search

An inverse analysis is used to estimate linearly temperature dependent thermal conductivity components kx(T), ky(T) and specific heat capacity C(T) per unit volume for an orthotropic solid. Simulated measured transient temperature data are generated by adding random errors to the exact temperatures computed from the solution of the two-dimensional, direct transient heat conduction problem. An iterative procedure, based on minimizing

Y. Jarny

1995-01-01

252

Uncertainty of the stratospheric/tropospheric temperature trends in 1979-2008: multiple satellite MSU, radiosonde, and reanalysis datasets  

NASA Astrophysics Data System (ADS)

The trends and spreads of tropospheric and stratospheric temperature are discussed in terms of three groups of datasets in 1979-2008. These datasets include (a) three satellite observations of Microwave Sounding Units (MSU) measurements, (b) five radiosonde observations and (c) five reanalysis products. The equivalent tropospheric and stratospheric temperature from radiosonde and reanalyses are calculated based on the vertical weighting function of the MSU channel 2 (CH2) and channel 4 (CH4) measurements, respectively. The results show that both cooling in the stratosphere and warming in troposphere significantly depends on the datasets and latitudes.

Xu, J.; Powell, A. M., Jr.

2011-10-01

253

Uncertainty of the stratospheric/tropospheric temperature trends in 1979-2008: Multiple Satellite MSU, radiosonde, and reanalysis datasets  

NASA Astrophysics Data System (ADS)

The trends and spreads of tropospheric and stratospheric temperature are discussed in terms of three groups of datasets in 1979-2008. These datasets include (a) three satellite observations of Microwave Sounding Units (MSU) measurements, (b) five radiosonde observations and (c) five reanalysis products. The equivalent tropospheric and stratospheric temperature from radiosonde and reanalyses are calculated based on the vertical weighting function of the MSU channel 2 (CH2) and channel 4 (CH4) measurements, respectively. The results show that both cooling in the stratosphere and warming in troposphere significantly depends on the datasets and latitudes.

Xu, J.; Powell, A. M., Jr.

2011-06-01

254

One-loop renormalization of the two-dimensional linear [sigma] model and Gross-Neveu model at finite temperature  

SciTech Connect

We study the one-loop renormalization of the two-dimensional linear [sigma] model and Gross-Neveu model at finite temperature. To do this, we use thermo field dynamics and regard the Gross-Neveu model as a [ital Z][sub 3]=[ital Z][sub 4]=0 limit of the linear [sigma] model. We also derive the renormalization group equations with respect to a dimensional parameter [ital M].

Kang, S.K.; Kim, J.K. (Department of Physics, Korea Advanced Institute of Science and Technology, 373-1, Kusung-dong, Yusung-ku, Taejon (Korea, Republic of))

1993-09-15

255

High-temperature linear kinetics of FeS formation and reduction in COS-CO-CO 2 gas mixtures  

Microsoft Academic Search

The linear kinetics of the monosulfide scale formation and reduction according to the overall reaction Fe(s) + COS(g) = FeS(s) + CO(g) in COS-CO-CO2 gas mixtures was studied in the temperature range 750–910† C by a thermogravimetric technique. The validity of the linear rate law is limited to short times of exposure and relatively low partial pressures of COS. A

Steinar Haugen; Aasmund Sterten

1971-01-01

256

Evolutionary trends in high temperature superconductivity. (Latest citations from the INSPEC database). Published Search  

SciTech Connect

The bibliography contains citations concerning experimental and theoretical studies of high temperature superconducting materials. Topics include critical temperatures, transition temperatures, superconducting niobium alloys and rare earth metals, superconducting structure stabilization, and magnetic superconductors. Fabrication and evaluation of high temperature superconducting devices and films are included. (Contains a minimum of 75 citations and includes a subject term index and title list.)

NONE

1995-01-01

257

Evolutionary trends in high temperature superconductivity. (Latest citations from the INSPEC database). Published Search  

SciTech Connect

The bibliography contains citations concerning experimental and theoretical studies of high temperature superconducting materials. Topics include critical temperatures, transition temperatures, superconducting niobium alloys and rare earth metals, superconducting structure stabilization, and magnetic superconductors. Fabrication and evaluation of high temperature superconducting devices and films are included. (Contains a minimum of 68 citations and includes a subject term index and title list.)

Not Available

1994-03-01

258

Climate Trend Detection using Sea-Surface Temperature Data-sets from the (A)ATSR and AVHRR Space Sensors.  

NASA Astrophysics Data System (ADS)

Sea-Surface Temperature (SST) is an important indicator of global change, designated by GCOS as an essential Climate Variable (ECV). The detection of trends in Global SST requires rigorous measurements that are not only global, but also highly accurate and consistent. Space instruments can provide the means to achieve these required attributes in SST data. This paper presents an analysis of 15 years of SST data from two independent data sets, generated from the (A)ATSR and AVHRR series of sensors respectively. The analyses reveal trends of increasing global temperature between 0.13°C to 0.18 °C, per decade, closely matching that expected from some current predictions. A high level of consistency in the results from the two independent observing systems is seen, which gives increased confidence in data from both systems and also enables comparative analyses of the accuracy and stability of both data sets to be carried out. The conclusion is that these satellite SST data-sets provide important means to quantify and explore the processes of climate change. An analysis based upon singular value decomposition, allowing the removal of gross transitory disturbances, notably the El Niño, in order to examine regional areas of change other than the tropical Pacific, is also presented. Interestingly, although El Niño events clearly affect SST globally, they are found to have a non- significant (within error) effect on the calculated trends, which changed by only 0.01 K/decade when the pattern of El Niño and the associated variations was removed from the SST record. Although similar global trends were calculated for these two independent data sets, larger regional differences are noted. Evidence of decreased temperatures after the eruption of Mount Pinatubo in 1991 was also observed. The methodology demonstrated here can be applied to other data-sets, which cover long time-series observations of geophysical observations in order to characterise long-term change.

Llewellyn-Jones, D. T.; Corlett, G. K.; Remedios, J. J.; Noyes, E. J.; Good, S. A.

2007-05-01

259

Temperature trends in the skin/surface, mid-troposphere and low stratosphere near Korea from satellite and ground measurements  

NASA Astrophysics Data System (ADS)

Various types of satellite (AIRS/AMSU, MODIS) and ground measurements are used to analyze temperature trends in the four vertical layers (skin/surface, mid-troposphere, and low stratosphere) around the Korean Peninsula (123-132°E, 33-44°N) during the period from September 2002 to August 2010. The ground-based observations include 72 Surface Meteorological Stations (SMSs), 6 radiosonde stations (RAOBs), 457 Automatic Weather Stations (AWSs) over the land, and 5 buoy stations over the ocean. A strong warming (0.052 K yr-1) at the surface, and a weak warming (0.004˜0.010 K yr-1) in the mid-troposphere and low stratosphere have been found from satellite data, leading to an unstable atmospheric layer. The AIRS/AMSU warming trend over the ocean surface around the Korean Peninsula is about 2.5 times greater than that over the land surface. The ground measurements from both SMS and AWS over the land surface of South Korea also show a warming of 0.043˜0.082 K yr-1, consistent with the satellite observations. The correlation average (r = 0.80) between MODIS skin temperature and ground measurement is significant. The correlations between AMSU and RAOB are very high (0.91˜0.95) in the anomaly time series, calculated from the spatial averages of monthly mean temperature values. However, the warming found in the AMSU data is stronger than that from the RAOB at the surface. The opposite feature is present above the mid-troposphere, indicating that there is a systematic difference. Warming phenomena (0.012˜0.078 K yr-1) are observed from all three data sets (SMS, AWS, MODIS), which have been corroborated by the coincident measurements at five ground stations. However, it should also be noted that the observed trends are subject to large uncertainty as the corresponding 95% confidence intervals tend to be larger than the observed signals due to large thermal variability and the relatively short periods of the satellitebased temperature records. The EOF analysis of monthly mean temperature anomalies indicates that the tropospheric temperature variability near Korea is primarily linked to the Arctic Oscillation (AO), and secondarily to ENSO (El Niño and Southern Oscillation). However, the low stratospheric temperature variability is mainly associated with Southern Oscillation and then additionally with Quasi-Biennial Oscillation (QBO). Uncertainties from the different spatial resolutions between satellite data are discussed in the trends.

Yoo, Jung-Moon; Won, Young-In; Cho, Young-Jun; Jeong, Myeong-Jae; Shin, Dong-Bin; Lee, Suk-Jo; Lee, Yu-Ri; Oh, Soo-Min; Ban, Soo-Jin

2011-11-01

260

Trends and variability in the sea surface height, sea surface temperature and wind stress curl in the South Atlantic ocean  

NASA Astrophysics Data System (ADS)

Altimetry sea level anomalies (SLA), sea surface temperatures anomalies (SSTA) and wind stress curl (WSC) were analyzed and had their trends calculated and their variability studied for the South Atlantic ocean using the last 19 years of SALTO/DUACS altimeter data, ERSST data and ERA-INTERIM data. All data had their temporal resolution adjusted to the one of altimeter data. The trends were calculated between January, 1st 1993 and December, 31th 2011. The stronger and positive SLA trends occurred in the region of the Zapiola Ridge (14 mm/year) and in some places in the Drake Passage (10 mm/year). Negative trends were observed in the Southern part of Argentinian basin (-4 mm/year), next to the Confluence Brazil Malvinas (-8 mm/year) and to the southwest of the African coast (-6 mm/year). The SST trends were positive North of 40°S, and negative south of 60°S. They were also negative along the Argentinean continental slope along the path of the Malvinas Current. The WSC trend was also negative along the Argentine continental slope. In the Southeast Atlantic, the WSC trend had a zonal distribution with alternate signs. To understand the processes responsible for the trend patterns in the South Atlantic ocean, the high and the low frequencies were obtained applying successively a 25 week band pass filter followed by a 37 week band pass filter. The percentage of explained variance by the high frequency, low frequency and seasonal signals (hf/lf/ss) were compared for SLA, SSTA and WSC. The variance of SLA in the Southwestern Atlantic was explained by the proportion of (80%, 15%,5%), except along the Argentinean continental slope (15%, 50%, 35%), the inner part of the ZR (10%,65%,25%). The central part of the South Atlantic showed dominant low frequency variance (proportions of 15%, 80% and 5% (hf/lf/ss), respectively). The SSTA variance was dominated by the high frequency in the Uruguayan coast, around ZR, in the Drake Passage and in the Agulhas Leakage (60-80%), low frequency variability responds to 55-75% of the total variability away from the continental borders. The seasonal frequency is important in the CBM region and in the inner of ZR (25%, 40%, 35%). The WSC variance was mostly explained by high frequencies (70%), low frequencies explained between 10% and 15%, at latitudes lower than 20°S, in the Argentinean continental slope and in the Agulhas Leakage. The EOF analysis were performed on the high and low frequencies components of each variable. The results will be presented in the poster.

Porto da Silveira, Isabel; Ponzi Pezzi, Luciano; Buss de Souza, Ronald; Sennéchael, Nathalie; Provost, Christine

2013-04-01

261

Snowmelt timing (onset and melt-refreeze) trends in the Yukon River basin determined from passive microwave brightness temperatures  

NASA Astrophysics Data System (ADS)

High latitude drainage basins are experiencing increases in temperature higher than the global average with snowmelt dominated basins most sensitive to effects in winter due to snowpack's integration of these changes over the season. This may influence the timing of snowmelt onset and the occurrence of any preceding (early) melt events, resulting in changes in spring runoff and associated flooding, often the most significant hydrologic events of the year. It is therefore critical to be able to understand and model these processes, especially for ungauged basins with little meteorological data. For such basins, passive microwave remote sensing can be utilized; an approach tested in the Yukon River Basin draining more than 850,000 km2 of Alaska and the Yukon Territory. Brightness temperature (Tb) data from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) 36.5 V-GHz frequency and the Special Sensor Microwave Imager (SSM/I) 37 V-GHz frequency together form a time series from 1988 to 2010, enabling us to detect trends in snowmelt onset timing and the end of melt-refreeze period. Tb encompasses both physical temperature and emissivity with wet snow easily detected by an abrupt increase in emissivity. Tb and diurnal amplitude variation (DAV) thresholds determine dates of melt onset and melt-freeze end (end of high DAV), defined as where thresholds are met for more than three of five consecutive days. Melt that is detected before melt onset and is not sustained for more than three out of five days is classified as an early melt event. Preliminary results of trends in snowmelt onset and occurrence of early melt events suggest sub-basin differences occur with varying landcover, permafrost, and elevation. Of the thirteen sub-basins that comprise the Yukon River basin, five have significant trends toward later melt onset dates, while the northernmost (the Chandalar and Porcupine) have earlier melt onset. The majority of basins with later onset show increasing trends of early melt events, while those with earlier onset have decreasing trends, suggesting winter melt dynamics may affect melt onset later in the year. Significant variability, however, requires further analysis to more definitively determine trends and relationships between the melt parameters.

Semmens, K. A.; Ramage, J. M.

2011-12-01

262

Summer Temperature Trend Over the Past Two Millennia Using Air Content in Himalayan Ice.  

National Technical Information Service (NTIS)

Two Himalayan ice cores display a factor-two decreasing trend of air content over the past two millennia, in contrast to the relatively stable values in Greenland and Antarctica ice cores over the same period. Because the air content can be related with t...

J. Chappellaz J. Jouzel P. C. Chu S. Hou V. Masson- Delmotte

2007-01-01

263

Consistency of modelled and observed temperature trends in the tropical troposphere  

Microsoft Academic Search

A recent report of the U.S. Climate Change Science Program (CCSP) identified a 'potentially serious inconsistency' between modelled and observed trends in tropical lapse rates (Karl et al., 2006). Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to

B. D. Santer; P. W. Thorne; L. Haimberger; K. E. Taylor; T. M. L. Wigley; J. R. Lanzante; S. Solomon; M. Free; P. J. Gleckler; P. D. Jones; S. A. Klein; C. Mears; D. Nychka; G. A. Schmidt; S. C. Sherwood; F. J. Wentz

2008-01-01

264

The Orthorhomic Structure of CaCo[subscript 3], SrCO[subscript 3], PbCO[subscript 3] and BaCO[subscript 3]: Linear Structural Trends  

SciTech Connect

The crystal structures of four isostructural orthorhombic carbonates, CaCO{sub 3} (aragonite), SrCO{sub 3} (strontianite), PbCO{sub 3} (cerussite), and BaCO{sub 3} (witherite), were obtained by Rietveld refinements using data acquired by synchrotron high-resolution powder X-ray diffraction (HRPXRD). For BaCO{sub 3}, powder neutron-diffraction data were obtained and refined by the Rietveld method. For aragonite, we also carried out a refinement of the structure by single-crystal X-ray diffraction. These carbonates belong to the space group Pmcn, with Z = 4. The CO{sub 3} group is slightly non-planar, and the two independent C-O distances are slightly different. The CO{sub 3} group becomes more symmetrical and less aplanar from CaCO{sub 3} to BaCO{sub 3} (M{sub radii}{sup 2+}: Ca < Sr < Pb < Ba). The CaCO{sub 3} structure is, therefore, the most distorted, whereas the BaCO{sub 3} structure is the least distorted. Several linear structural trends are observed in plots of selected parameters as a function of the unit-cell volume, V. These parameters are radii of the nine-coordinated M{sup 2+} cations, the unit-cell axes, the average and distances, average angle, and aplanarity. These linear trends are the result of the effective size of the divalent ionic radius of the M cations that are coordinated to nine oxygen atoms. The geometrical features of the CO{sub 3} group can be obtained reliably only by using neutron-diffraction data, especially in the presence of other heavy atoms.

Antao, Sytle M.; Hassan, Ishmael; (Calgary); (West Indies)

2010-11-12

265

Multi-decadal surface temperature trends near the Ice Divide of East Antarctica using borehole firn temperature measurements and inversion method  

NASA Astrophysics Data System (ADS)

The objective of this investigation is to detect multi-decadal surface temperature trends near the Ice Divide of East Antarctica. The interior of East Antarctic Ice Sheet (EAIS) remains as one of the least explored areas on earth. In recent years there have been several studies attempting to reconstruct the surface temperature history of Antarctica for the past 50 years using several approaches. However the lack of in situ data has hindered the science community in reaching a conclusive answer about Antarctic climate change, and in particular for the EAIS. In order to gain a better assessment of Antarctic climate change, additional data sources are needed to reduce the current uncertainty. Surface temperature inversion from firn temperature measurements will provide a source of climate reconstruction independent of firn chemistry, sparse weather data, satellite data or ice cores. During the Norwegian-U.S. IPY Scientific Traverse of East Antarctica, in austral summer of 2007-08, thermal-profiling units were installed at three locations (76.06 ° S, 22.46 ° E, Traverse site NUS07-2; 78.65 ° S, 35.64 ° E, NUS07-5, 126 km from Plateau Station; 82.07 ° S, 54.9 ° E, NUS07-7, 2 km from the Pole of Inaccessibility). Each unit consists of 16 PRTs (Platinum Resistance Thermometers) distributed between 0.2 and 90 m in depth. Wired PRTs were lowered into the borehole after an ice core was drilled and before the hole was back-filled with granulated snow to prevent air circulation and provide thermal conduction between PRTs and firn. Near-hourly data are being transmitted through ARGOS satellite telemetry system. The overall uncertainty in firn temperature measurement is between 0.02 and 0.03 ° C. Mean temperature gradients between -0.5 and -0.75 ° C were found between 16 and 90 m at three sites, with standard deviations less then 0.03 ° C. These gradients are larger than or about the same as previously published studies that modeled temperature profile under a steady-state climatic condition. Our results suggest a cooling to no significant trend near the Ice Divide of East Antarctica for the past several decades. Detailed analysis with the application of inversion method is ongoing to determine how the observed signals in the temperature profiles translate in to magnitudes and temporal scales of the surface temperature trends. A positive temperature gradient, suggesting recent warming, was identified for the top of the Greenland ice sheet (Summit station) and will be discussed in comparison.

Muto, A.; Scambos, T. A.; Steffen, K.

2008-12-01

266

The spin temperature of NH3 in Comet C/1999S4 (LINEAR).  

PubMed

A high-dispersion spectrum of Comet C/1999S4 (LINEAR) was obtained in the optical region with the high-dispersion spectrograph on the Subaru telescope when the comet was 0.863 astronomical units from the Sun before its disintegration. We obtained high signal-to-noise ratio emission lines of the cometary NH2 bands from which an ortho-to-para ratio (OPR) of 3.33 +/- 0.07 was derived on the basis of a fluorescence excitation model. Assuming that cometary NH2 mainly originates from ammonia through photodissociation, the derived OPR of NH2 molecules should reflect that of ammonia, which provides information on the environment of molecular formation or condensation and of the thermal history of cometary ices. Assuming that the OPR of ammonia in comets was unchanged in the nucleus, the derived spin temperature of ammonia (28 +/- 2 kelvin) suggests that a formation region of the cometary ammonia ice was between the orbit of Saturn and that of Uranus in the solar nebula. PMID:11691989

Kawakita, H; Watanabe, J; Ando, H; Aoki, W; Fuse, T; Honda, S; Izumiura, H; Kajino, T; Kambe, E; Kawanomoto, S; Noguchi, K; Okita, K; Sadakane, K; Sato, B; Takada-Hidai, M; Takeda, Y; Usuda, T; Watanabe, E; Yoshida, M

2001-11-01

267

Design of a platinum resistance thermometer temperature measuring transducer and improved accuracy of linearizing the output voltage  

SciTech Connect

An improved method is presented for designing a temperature measuring transducer, the electrical circuit of which comprises an unbalanced bridge, in one arm of which is a platinum resistance thermometer, and containing a differential amplifier with feedback. Values are given for the coefficients, the minimum linearization error is determined, and an example is also given of the practical design of the transducer, using the given coefficients. A determination is made of the limiting achievable accuracy in linearizing the output voltage of the measuring transducer, as a function of the range of measured temperature.

Malygin, V.M.

1995-06-01

268

Comparison of geographical trend patterns in sea level and sea surface temperature in the Pacific Ocean during 1993-2011  

NASA Astrophysics Data System (ADS)

It is now well established that geographical trend patterns in satellite altimetry-based sea level are mostly caused by non uniform steric trend patterns, the largest contribution being due to the thermosteric component. In the Pacific Ocean, the observed sea level trend pattern over 1993-2011 results from a superposition two types of signals: (1) a strong positive trend V-shaped anomaly located 120°E and 160° E in longitude and ~20°S-20°N in latitude and (2) another V-shaped anomaly of much broader scale -extending to mid-latitudes in the central Pacific-, quite similar to the dominant large-scale trend pattern observed in sea surface temperature (SST). Previous studies have shown that the type (1) signal is related to El Nino Southern Oscillation (ENSO). The type (2) signal reflects the Pacific Decadal Oscillation (PDO), the dominant component of large-scale SST variability in the Pacific. In this study, we analyze altimetry-based sea level, steric sea level and SST over the 1993-2011 time span to discriminate between the near surface and deeper thermosteric contributions to sea level. The sea level and SST data are based on the recently available products from the ESA Climate Change Initiative project and several other products like HadiSST, ERAINTERIM. Steric data are based on an updated version of the Ishii and Kimoto (2009) data. We compute the thermosteric contribution to sea level in different layers from the surface to the 700 m depth, and through correlation and Empirical Orthogonal Function analyses, explore the spatio-temporal coherence between the three variables (sea level, depth-dependent steric sea level and SST).

Palanisamy, Hindumathi; Cazenave, Anny; Delcroix, Thierry; Meyssignac, Benoit; Balmaseda, Magdalena; Merchant, Christopher

2013-04-01

269

Global trends in lake surface temperatures observed using multi-sensor thermal infrared imagery  

Microsoft Academic Search

Recent research has shown that the temperature of lakes and other inland water bodies does not only act as a good indicator of climate variability but under certain conditions can even increase more rapidly than the regional air temperature. Further investigation of this phenomenon in particular and of the interaction between lake temperature and climate variability in general requires extensive

Philipp Schneider; Simon J. Hook; Robert G. Radocinski; Gary K. Corlett; Glynn C. Hulley; S. Geoffrey Schladow; Todd E. Steissberg

2010-01-01

270

Research on temperature calibration of extended area blackbody based on two-point multi-section linear correction algorithm  

NASA Astrophysics Data System (ADS)

The spectral radiation of extended area blackbody source is widely used to provide a reference for absolute temperature in infrared test and calibration. Thus the temperature accuracy of extended area blackbody is a critical parameter to determine the performance of test and calibration system. The temperature of emissive surface is measured and controlled by Platinum resistance temperature sensor. A variety of techniques have been developed for improving the temperature accuracy of extended area blackbody. In order to overcome nonlinear error caused by the Platinum resistance temperature sensor, a calibration method based on two-point multi-section linear correction algorithm is proposed. The tests verify that the method enhances the calibration accuracy of temperature accuracy of extended area blackbody and satisfies the requirements of high precision tests on metrological quality.

Han, Shun-li; Hu, Wei-liang; Luo, Wen-jian; Wang, Rui-xia

2013-08-01

271

Twelve-month running trends from Earth Radiation Budget Satellite (ERBS) active-cavity radiometric measurements and global surface temperatures  

NASA Astrophysics Data System (ADS)

Four earth-viewing nonscanning active cavity radiometers of the ERBS (Earth Radiation Budget Satellite) have been measuring the radiation arising from the earth-atmosphere system since its" launch day, October 5, 1984. The ERBS spacecraft was placed in a non-sun-synchronous trajectory inclined at 57°. Two radiometers out of four, namely the wide field-of-view total (WFOV-T) radiometer which measures the radiation in the total spectral band of 0.2 - 100 ?m, and the wide-field-of-view shortwave (WFOV-SW) radiometer measures the Earth"s reflected radiation in the wavelength region of 0.2 - 5 ?m were used in this study. These sensors were calibrated continuously by observing the in-flight internal black bodies as well as the Sun every two weeks. The WFOV-T channel was found very stable within 0.1%. The monthly flux values of the ERBS nonscanning active cavity radiometers at satellite altitude and the corresponding NCDC (National Climatic Data Center) global surface temperature data for the period of fifteen years (1985-1999) were used in this paper. The effect of Mt. Pinatubo eruption is very clearly noticeable in the running trends of both WFOV-T and WFOV-SW radiometric measurements. Further the resulting twelve month running trends derived from the outgoing longwave radiation was found to follow the twelve month running trend determined from the global surface temperature data set. Both trends are real and increasing. The "global-cooling-like" event caused by the Mt. Pinatubo eruption was also found under both day and nighttime conditions.

Pandey, Dhirendra K.; Lee, Robert B., III; Paden, Jack; Bush, Kathryn A.; Snyder, Dianne; Wilson, Robert S.; Banks, Waldena; Al-Hajjah, Aiman; Thomas, Susan

2004-02-01

272

Identifying Western Montana Climate Trends using 50 years of Temperature and Precipitation records for applications in ecosystem process models such as Biome-BGC  

Microsoft Academic Search

It's increasingly clear that Global Climate change will affect regions of the earth in different ways. This study examines meteorological station records from the National Climatic Data Center for selected Western Montana Stations in order to identify yearly and seasonal temperature, precipitation, snow pack and hydrologic trends over the last 50 years. Once identified, these trends are used to make

S. L. Holbrook; F. Heinsch; S. W. Running

2007-01-01

273

Secular temperature trends for the southern Rocky Mountains over the last five centuries  

NASA Astrophysics Data System (ADS)

Pre-instrumental surface temperature variability in the Southwestern United States has traditionally been reconstructed using variations in the annual ring widths of high altitude trees that live near a growth-limiting isotherm. A number of studies have suggested that the response of some trees to temperature variations is non-stationary, warranting the development of alternative approaches towards reconstructing past regional temperature variability. Here we present a five-century temperature reconstruction for a high-altitude site in the Rocky Mountains derived from the oxygen isotopic composition of cellulose (?18Oc) from Bristlecone Pine trees. The record is independent of the co-located growth-based reconstruction while providing the same temporal resolution and absolute age constraints. The empirical correlation between ?18Oc and instrumental temperatures is used to produce a temperature transfer function. A forward-model for cellulose isotope variations, driven by meteorological data and output from an isotope-enabled General Circulation Model, is used to evaluate the processes that propagate the temperature signal to the proxy. The cellulose record documents persistent multidecadal variations in ?18Oc that are attributable to temperature shifts on the order of 1°C but no sustained monotonic rise in temperature or a step-like increase since the late 19th century. The isotope-based temperature history is consistent with both regional wood density-based temperature estimates and some sparse early instrumental records.

Berkelhammer, M.; Stott, L. D.

2012-09-01

274

Linear temperature dependence of conductivity in the apparent insulating regime of dilute two-dimensional holes in GaAs  

Microsoft Academic Search

The conductivity of extremely high mobility dilute two-dimensional holes in GaAs changes linearly with temperature in the insulating side of the metal-insulator transition. Hopping conduction, characterized by an exponentially decreasing conductivity with decreasing temperature, is not observed when the conductivity is smaller than e2\\/h. We suggest that strong interactions in a regime close to the Wigner crystallization must be playing

Hwayong Noh; M. P. Lilly; D. C. Tsui; J. A. Simmons; L. N. Pfeiffer; K. W. West

2003-01-01

275

The effect of linear thermal expansion on the temperature coefficient of resistance of double-layer thin metallic films  

Microsoft Academic Search

A general theoretical expression for the temperature coefficient of resistance of double-layer thin metallic films, based on the well known Fuchs-Sondheimer model, is derived. This expression includes the linear thermal expansion coefficients and Poisson's ratios of the double layers and the substrate, also the film dimensions and temperature coefficient of resistance of the double-layer thin film, with and without the

M. A. El Hiti; M. A. Ahmed

1990-01-01

276

Temperature Sensitivity Trends and Multi-Stimuli Sensitive Behavior in Amphiphilic Oligomers  

PubMed Central

A series of oligomers, containing oligo(ethylene glycol) (OEG) moieties, with the same composition of amphiphilic functionalities has been designed, synthesized, and characterized for their temperature sensitive behavior. The non-covalent amphiphilic aggregates, formed from these molecules, influence the temperature sensitivity of these molecules. Moreover, the covalent tethering of the amphiphilic units also has significant influence on their temperature sensitivity. The lower critical solution temperatures (LCST) of these oligomers show increasingly sharp transitions with increasing numbers of OEG functional groups, indicating enhanced cooperativity in dehydration of the OEG moieties when covalently tethered. These molecules were also engineered to be concurrently sensitive to enzymatic reaction and pH. This possibility was investigated using porcine liver esterase as the enzyme, where we show that enzymatic action on the pentamer lowers its temperature sensitivity. The product moiety from the enzymatic reaction renders the amphiphilic oligomer exhibit a pH-dependent temperature sensitivity.

Wang, Feng; Klaikherd, Akamol

2011-01-01

277

Long-term trends of temperature, salinity, density, and transient tracers in the central Greenland Sea  

Microsoft Academic Search

We present long-term observations of temperature, salinity, tritium\\/3He, chlorofluorocarbon-11 (CFC11), and chlorofluorocarbon-12 (CFC12) for the central Greenland Gyre. The time series span the periods between 1952 and 1994 (temperature), 1981 and 1994 (salinity), 1972 and 1994(tritium\\/3He,) and 1982 and 1994 (CFCs). The correlation between hydrographic and transient tracer data indicates that low temperatures in the deep water in the early

Gerhard Bönisch; Johan Blindheim; John L. Bullister; Peter Schlosser; Douglas W. R. Wallace

1997-01-01

278

Influence of Patterns of Climate Variability on the Difference between Satellite and Surface Temperature Trends  

Microsoft Academic Search

During the past 20 years, satellite measurements of tropospheric temperature have shown a slower rate of global temperature increase than surface air temperature, yielding an increase in the surface to lower-troposphere lapse rate of 0.12 K decade 21 from 1979 to August 2001. This increase in lapse rate was preceded by a decrease over the previous 15-yr interval. The influence

Gabriele C. Hegerl; John M. Wallace

2002-01-01

279

A new perspective on recent global warming: Asymmetric trends of daily maximum and minimum temperature  

SciTech Connect

In this work, it was concluded that monthly mean maximum and minimum temperatures for over 50% (10%) of the Northern (Southern) Hemisphere landmass, accounting for 37% of the global landmass, indicate that the rise of the minimum temperature has occurred at a rate three times that of the maximum temperature during the period 1951-90 (0.84[degrees]C versus 0.28[degrees]C). The decrease of the diurnal temperature range is approximately equal to the increase of mean temperature. The asymmetry is detectable in all seasons and in most of the regions studied. The decrease in the daily temperature range is partially related to increases in cloud cover. Furthermore, a large number of atmospheric and surface boundary conditions are shown to differentially affect the maximum and minimum temperature. Linkages of the observed changes in the diurnal temperature range to large-scale climate forcings, such as anthropogenic increases in sulfate aerosols, greenhouse gases, or biomass burning (smoke), remain tentative. Nonetheless, the observed decrease of the diurnal temperature range is clearly important, both scientifically and practically. 36 refs., 9 figs., 5 tabs.

Karl, T.R.; Knight, R.W.; Gallo, K.P.; Peterson, T.C. (National Climatic Data Center, Asheville, NC (United States)); Jones, P.D. (Univ. of East Anglia, Norwich, Norfolk (United Kingdom)); Kukla, G. (Columbia Univ., Palisades, NY (United States)); Plummer, N. (Bureau of Meterology, Melbourne (Australia)); Razuvayev, V. (Research Institute of Hydrometerological Information, Obninsk, Kalugu (Russian Federation)); Lindseay, J. (Univ. of Wirswatersrand (South Africa)); Charlson, R.J. (Univ. of Washington, Seattle (United States))

1993-06-01

280

Hemispheric surface air temperature variations: Recent trends and an uptate to 1987  

Microsoft Academic Search

The hemispheric mean land-surface air temperature series developed for both hemispheres by Jones et al. are updated through 1987. The global temperature estimate for 1987 is the third warmest on record, 1858--1987. Recent warming over the last 20 years (1967--86) is shown to be centered on middle latitude belts in both hemispheres.

P. D. Jones

1988-01-01

281

Consistency check for trends in surface temperature and upper-level circulation: 1950-1992  

Microsoft Academic Search

A time series of 43 years of observed monthly mean air temperature at 109 sites in the 48 contiguous US is compared to monthly mean air temperature specified from hemispheric gridded 700-mb heights. Because both upper-air and surface data have problems that may limit their use in climate change studies, this comparison could be considered a mutual consistency check. Cooling

Huug M. van den Dool; E. A. OLenic; William H. Klein

1993-01-01

282

European Seasonal and Annual Temperature Variability, Trends, and Extremes Since 1500  

Microsoft Academic Search

Multiproxy reconstructions of monthly and seasonal surface temperature fields for Europe back to 1500 show that the late 20th- and early 21st-century European climate is very likely (>95% confidence level) warmer than that of any time during the past 500 years. This agrees with findings for the entire Northern Hemisphere. European winter average temperatures during the period 1500 to 1900

Jürg Luterbacher; Daniel Dietrich; Elena Xoplaki; Martin Grosjean; Heinz Wanner

2004-01-01

283

Large room-temperature quantum linear magnetoresistance in multilayered epitaxial graphene: Evidence for two-dimensional magnetotransport  

NASA Astrophysics Data System (ADS)

We report magnetoresistance (MR) properties from room temperature (300 K) to 2 K in multilayered epitaxial graphene (EG) prepared on C-face of SiC substrate. A large (~50%) and linear MR is observed at 300 K, which is distinctively different from other carbon materials. This linear MR is attributed to the two-dimensional (2D) transport in the material as inferred from our angular dependence magnetotransport experiments. Furthermore, negative MR behaviour at a low field regime for temperatures <=20 K is recognised as a weak localization in EG. This study underlines the potential of exploiting multilayered EG on C-face SiC for room temperature magneto-electronic device applications.

Sevak Singh, Ram; Wang, Xiao; Chen, Wei; Ariando; Wee, Andrew T. S.

2012-10-01

284

Future trend of extreme value distributions of wintertime surface air temperatures over Korea and the associated physical changes  

NASA Astrophysics Data System (ADS)

Daily winter temperatures in Korea have been analyzed via CSEOF analysis. Then, each PC time series was detrended and was fitted to an AR (autoregressive) model. Based on the identified AR model, an artificial time series of arbitrary length can be generated by using an arbitrary white-noise time series. In this way, one hundred new sets of PC time series were generated over the period of 1973-2058. Then, the trend for each PC time series was added back to the artificial PC time series extending the trend until 2058. Ultimately, artificial daily winter temperatures in Korea have been constructed by using the artificial PC time series and the original loading vectors derived from the observational data. The 100 new data sets have been investigated in order to understand the winter temperature variability 50 years into the future. Regression analysis in CSEOF space shows that temperature increase in Korea is associated with increased 850-hPa air temperature over most of the Asian domain (97°-153°E × 22°-73°N) and increased 850-hPa geopotential height in the southern part of the domain. As a result, southerly and southeasterly wind anomalies develop carrying positive temperature anomalies northward and northwestward. Both the 200-hPa air temperature and geopotential height changes indicate that there will be fairly significant northward shift of the jet stream in future. The standard deviation of the 200-hPa potential vorticity increases implying that shortwave trough and henceforth baroclinic instability will increase in future. Finally, GEV (Generalized Extreme Value) distribution and GPD (Generalized Pareto distribution) distribution have been compared between the observational records and the future records of the same length. The extreme value distributions based on the synthetic datasets show that warm extreme events will be more extreme in future and cold extreme events, on the other hand, will be less extreme. This study provides an estimate of future temperatures based on the observational data and serves as an independent baseline solution for comparisons with numerical model solutions.

Kim, Kwang-Yul; Kim, Ji-Won; Kim, Maeng-Ki; Cho, Chun-Ho

2013-09-01

285

Trends and differences of the temperature effect on mismatch in different CMOS technology nodes  

Microsoft Academic Search

Statistical drain-current differences between pairs of supposedly identical transistors, usually known as matching, represent a crucial aspect of analog and mixed-signal circuits. Although matching has been a subject of study for more than two decades, how the temperature affects it is still scarcely discussed in the open literature [1,2]. In previous work, we discussed temperature effects on matching properties for

P. Andricciola; H. Tuinhout; N. Wils

2010-01-01

286

Variability and Trends of Air Temperature and Pressure in the Maritime Arctic, 1875-2000  

Microsoft Academic Search

Arctic atmospheric variability during the industrial era (1875-2000) is assessed using spatially averaged surface air temperature (SAT) and sea level pressure (SLP) records. Air temperature and pressure display strong multidecadal variability on timescales of 50-80 yr [termed low-frequency oscillation (LFO)]. Associated with this variability, the Arctic SAT record shows two maxima: in the 1930s-40s and in recent decades, with two

Igor V. Polyakov; Roman V. Bekryaev; Genrikh V. Alekseev; Uma S. Bhatt; Roger L. Colony; Mark A. Johnson; Alexander P. Maskshtas; David Walsh

2003-01-01

287

Instability-driven Limits on Helium Temperature Anisotropy in the Solar Wind: Observations and Linear Vlasov Analysis  

NASA Astrophysics Data System (ADS)

Kinetic microinstabilities in the solar wind arise when the plasma deviates too far from thermal equilibrium. Previously published work has provided strong evidence that the cyclotron, mirror, and parallel and oblique firehose instabilities limit proton (i.e., ionized hydrogen) temperature anisotropy. However, few studies have thoroughly explored whether a less-abundant ion species can also trigger these instabilities. This study considered the possibility of similar instability-driven limits on ?-particle (i.e., fully ionized helium) temperature anisotropy. Linear Vlasov analysis was used to derive the expected threshold conditions for instabilities driven by ?-particle temperature anisotropy. Measurements in situ of ?-particle temperature anisotropy from the Wind spacecraft's Faraday cups were found to be consistent with the limits imposed by these instability thresholds. This strongly suggests that ?-particles, which only constitute ~5% of ions in the solar wind, can drive an instability if their temperature anisotropy becomes sufficiently extreme.

Maruca, Bennett A.; Kasper, Justin C.; Gary, S. Peter

2012-04-01

288

Regional 20th Century Temperature Trends from Radiosondes and Reanalyses in the Arctic (60°N-90°N)  

NASA Astrophysics Data System (ADS)

We compare seasonal 20th century atmospheric temperature trends in the Arctic (60°N-90°N) from radiosonde observations (CHUAN, HadAT, IUK, RAOBCORE/RICH, RATPAC) and reanalyses (ERA-40, NCEP/NCAR (NNR), Twentieth Century reanalysis (20CR), CFSR, ERA-Interim, MERRA). Large differences are found between the magnitudes, vertical profiles of the temperature trends (even for time periods > 3 decades), and chronological sequences of bidecadal, regional warming and cooling periods in the reanalyses. Long term zonal mean vertical trend profiles from CHUAN and from the reanalyses reaching back to the time before the satellite era show an amplification of the tropospheric warming towards the surface in all seasons except in JJA for the periods 1901-99, 1948-99 and 1957-99. In 20CR, a very strong 20th century cooling trend compared to the other datasets is found between 150 and 200 hPa. The agreement of the vertical structure and temporal behaviour of regional, bidecadal trends in the long reanalyses for 11 regions in the Arctic with CHUAN is best on average for ERA-40, followed by a less good agreement with trends from NNR (especially vertical structure) and 20CR (vertical structure and temporal behaviour). ERA-40 performs best for the NE Atlantic, Karelia, the SE Canadian Arctic, Alaska, and Central Siberia, and less favourably in the NW Canadian Arctic, E Siberia, W Siberia, and Novaya Zemlya. NNR agreement with CHUAN is significantly worse than in ERA-40 for the NE Atlantic, SE Canadian Arctic, SW Central Siberia, and E Central Siberia. 20CR performance is generally worse than that of ERA-40 and NNR, particularly for Karelia, the SE Canadian Arctic, Novaya Zemlya, W Siberia, and Central Siberia. For the more recent but shorter reanalyses, the internal agreement is generally very high, and results are close to CHUAN, ERA-40 and NNR. A comparison of CHUAN with the other radiosonde datasets is only possible for Alaska, E Central Siberia, NE Atlantic and NE Central Siberia (only HadAT and IUK), E Siberia and Novaya Zemlya (only HadAT), and Karelia, SW Central Siberia and W Siberia (all except RATPAC). For the period of overlap (1951-99) the agreement is reasonable with respect to the general picture. However, some disagreement on the trend sign can be seen a) for Alaska during DJF 1961-80 with HadAT and IUK, b) for E Central Siberia during MAM 1971-90 and 1980-99 with HadAT and during DJF 1980-99, MAM 1971-99 and SON 1961-80 with IUK, c) for Karelia during MAM/JJA 1961-80 with RAOBCORE/RICH (JJA also with HadAT and IUK), d) for NE Central Siberia during DJF 1961-80 with HadAT, e) for Novaya Zemlya during DJF1961-80 with HadAT, f) for SW Central Siberia during SON 1980-99 with RAOBCORE/RICH, g) for W Siberia during DJF/MAM 1961-80 with RAOBCORE/RICH, HadAT and IUK.

Stickler, Alexander; Brönnimann, Stefan

2013-04-01

289

Midlatitude long-term temperature trend deduced from 17 years of Na lidar observations and its relationships to solar cycle effects and an observed episodic response  

NASA Astrophysics Data System (ADS)

The Colorado State University (CSU) sodium lidar, first light in August 1989, has conducted regular observations of nocturnal mesopause region temperature and Na density continuously for more than 18 years since May 1991. The long-term nocturnal temperature record (1990-2007) has been used to reveal an episodic response after Mt. Pinatubo eruption, 11-year (and 27-day) solar cycle effect and temperature trend. Though the observed cooling reported in the literature from different instruments at different geographic locations is inconclusive, ranging between 0 and 10 K per decade, when all 3 long-term effects are included, the CSU data deduced a temperature trend with maximum cooling of ~ 1.5 K/decade at 91 km and a profile in general agreement with recent model predictions. The effect of solar flux variations and observed episodic response on the deduced long-term temperature trend will be discussed.

She, C.; Krueger, D. A.

2009-12-01

290

A linear regression model for predicting PNW estuarine temperatures in a changing climate  

EPA Science Inventory

Pacific Northwest coastal regions, estuaries, and associated ecosystems are vulnerable to the potential effects of climate change, especially to changes in nearshore water temperature. While predictive climate models simulate future air temperatures, no such projections exist for...

291

The non-linear relationship between nerve conduction velocity and skin temperature  

Microsoft Academic Search

Median motor and sensory nerves were examined in 20 healthy subjects. Superficial stimulating and recording electrodes were used, and the nerves were examined at natural skin temperature, after cooling and after heating of the arm. The conduction velocity for the fastest and slow conducting sensory fibres (temperature range 17-37 degrees C), and for the fastest conducting motor fibres (temperature range

K Todnem; G Knudsen; T Riise; H Nyland; J A Aarli

1989-01-01

292

Galactic cosmic rays and long-term trend in the U.S. surface air temperatures  

NASA Astrophysics Data System (ADS)

A heuristic search is conducted to see whether there is a connection between the long-term U. S. surface air temperature changes, the ionization caused by the galactic cosmic rays (GCRs) in the upper atmosphere, and the interplanetary magnetic field intensity (B) at earth orbit, in the instrumental era (1937-2010) covering seven sunspot number cycles. We find that B and GCRs may have only a subsidiary role (undefined) in contributing to the long-term changes in U.S. surface air temperature; other factors (some unknown at present) must be considered to solve the complex riddle of the climate change in terms of long-term surface air temperature changes.

Ahluwalia, H. S.

2012-07-01

293

Mapping seasonal trends of electron temperature in the topside ionosphere based on DEMETER data  

NASA Astrophysics Data System (ADS)

The diurnal, seasonal and latitudinal variations of the electron temperature in the Earth's topside ionosphere during relatively low solar activity period of 2005 - 2008 are investigated. In order to examine seasonal variations and morphology of the topside ionospheric plasma temperature, CNES micro-satellite DEMETER ISL data are used. Presented study is oriented on the dataset gathered in 2005 and 2008. Within conducted analysis, global maps of electron temperature for months of equinoxes and solstices have been developed. Furthermore, simultaneous studies on two-dimensional time series based on DEMETER measurements and predictions obtained with the IRI-2012 model supply examination of the topside ionosphere during recent deep solar minimum. Comparison with the IRI-2012 model reveals discrepancies between data and prediction, that are especially prominent during the periods of very low solar activity.

Slominska, Ewa; Rothkaehl, Hanna

2013-07-01

294

Sea surface temperature anomalies, seasonal cycle and trend regimes in the eastern Pacific coast  

NASA Astrophysics Data System (ADS)

We used the extended reconstruction of sea surface temperature (ERSST) to analyze the variation of surface temperature and the seasonal cycle along the coast of the eastern Pacific (60° N-60° S, 61 pixels alongshore) from 1950 to 2010 (732 months). First we analyzed the monthly anomalies and looked for a relationship of such anomalies with total solar radiation (TSI) and then, the regime shift detector (RSD) was applied to detect possible temperature regimes in the series. Posterior to this, we calculated a yearly temperature range per pixel (amplitude of seasonal cycle) and through the subtraction of a latitudinal theoretical curve of temperature based on solar irradiance, the residuals of the seasonal cycle were obtained. The results showed an almost complete spatial synchrony and dominance of negative anomalies from 1950 to mid-late 1970's, with a switch to near-zero and positive anomalies in the late 1990's when a shift to negative values is detected. Such a shift lasted until the early 2000's when positive anomalies appear again but there is a change to negative anomalies in the late 2000's. These results were supported by the RSD. The TSI variability shows a clear relationship with that in sea surface temperature anomalies and with the regime changes. This would be due to a difference in the amount of energy received from the sun. Comparing two consecutive periods, 1952-1975 with 1977-1999, the second received 0.39 % more energy (approximately 3 × 108 J m-2) from the sun. Seasonal cycles show larger range at northern latitudes (>40° N), northern tropical-template transition zone (20°-26° N) and in the tropical-equatorial band (0°-30° S). The smaller ranges occur at 0°-16° N and 50°-60° S. The residuals (seasonal minus the theoretical curve) indicate a clear modulation due to advection by ocean currents.

Ramos-Rodríguez, A.; Lluch-Cota, D. B.; Lluch-Cota, S. E.; Trasviña-Castro, A.

2011-05-01

295

Sea surface temperature anomalies, seasonal cycle and trend regimes in the Eastern Pacific coast  

NASA Astrophysics Data System (ADS)

We used the extended reconstruction of sea surface temperature (ERSST) to analyze the variation of surface temperature and the seasonal cycle along the coast of the eastern Pacific (60° N-60° S, 61 pixels alongshore) from 1950 to 2010 (732 months). First, we analyzed the monthly anomalies and looked for a relationship of such anomalies with total solar irradiance (TSI) and then the Regime Shift Detector (RSD) was applied to detect possible temperature regimes in the series. Afterwards, we calculated a yearly temperature range per pixel (amplitude of seasonal cycle) and through the subtraction of a latitudinal theoretical curve of temperature based on solar irradiance, the residuals of the seasonal cycle were obtained. The results showed an almost complete spatial synchrony and dominance of negative anomalies from 1950 to mid-late 1970's, with a switch to near-zero and positive anomalies that lasted up to late 1990's when a new shift to negative values was detected. Such a shift lasted until the early 2000's when positive anomalies appeared again but there was a change to negative anomalies in the late 2000's. These results were supported by the RSD. The TSI variability shows a clear relationship with that of sea surface temperature anomalies and with the regime changes. This is probably due to a difference in the amount of energy received from the sun. Comparing the "cool regime" versus the "warm regime", the second one received 0.39% more energy (approximately 3 × 108 J m-2) from the sun. Seasonal cycles show larger ranges at northern latitudes (>40° N), northern tropical-temperate transition zone (20°-26° N) and in the tropical-equatorial band (0°-30° S). The smallest ranges occur at 0°-16° N and 50°-60° S. The residuals (seasonal minus the theoretical curve) indicated a clear modulation due to advection by ocean currents.

Ramos-Rodríguez, A.; Lluch-Cota, D. B.; Lluch-Cota, S. E.; Trasviña-Castro, A.

2012-02-01

296

The relation between atmospheric humidity and temperature trends for stratospheric water  

NASA Astrophysics Data System (ADS)

We analyze the relation between atmospheric temperature and water vapor—a fundamental component of the global climate system—for stratospheric water vapor (SWV). We compare measurements of SWV (and methane where available) over the period 1980-2011 from NOAA balloon-borne frostpoint hygrometer (NOAA-FPH), SAGE II, Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS)/Aura, and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) to model predictions based on troposphere-to-stratosphere transport from ERA-Interim, and temperatures from ERA-Interim, Modern Era Retrospective-Analysis (MERRA), Climate Forecast System Reanalysis (CFSR), Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC), HadAT2, and RICHv1.5. All model predictions are dry biased. The interannual anomalies of the model predictions show periods of fairly regular oscillations, alternating with more quiescent periods and a few large-amplitude oscillations. They all agree well (correlation coefficients 0.9 and larger) with observations for higher-frequency variations (periods up to 2-3 years). Differences between SWV observations, and temperature data, respectively, render analysis of the model minus observation residual difficult. However, we find fairly well-defined periods of drifts in the residuals. For the 1980s, model predictions differ most, and only the calculation with ERA-Interim temperatures is roughly within observational uncertainties. All model predictions show a drying relative to HALOE in the 1990s, followed by a moistening in the early 2000s. Drifts to NOAA-FPH are similar (but stronger), whereas no drift is present against SAGE II. As a result, the model calculations have a less pronounced drop in SWV in 2000 than HALOE. From the mid-2000s onward, models and observations agree reasonably, and some differences can be traced to problems in the temperature data. These results indicate that both SWV and temperature data may still suffer from artifacts that need to be resolved in order to answer the question whether the large-scale flow and temperature field is sufficient to explain water entering the stratosphere.

Fueglistaler, S.; Liu, Y. S.; Flannaghan, T. J.; Haynes, P. H.; Dee, D. P.; Read, W. J.; Remsberg, E. E.; Thomason, L. W.; Hurst, D. F.; Lanzante, J. R.; Bernath, P. F.

2013-01-01

297

One Hundred Years of New York City's "Urban Heat Island": Temperature Trends and Public Health Impacts  

NASA Astrophysics Data System (ADS)

In this paper, we examine the relationship between the historical development of New York City and its effect on the urban climate. Urban "heat islands" (UHI) are created principally by man-made surfaces, including concrete, dark roofs, asphalt lots and roads, which absorb most of the sunlight falling on them and reradiate that energy as heat. Many urban streets have fewer trees and other vegetation to shade buildings, block solar radiation and cool the air by evapotranspiration. The historical development of the NYC heat island effect was assessed in terms of average temperature differences of the city center relative to its surrounding 31-county metropolitan region, comprised of parts of New York State, New Jersey, and Connecticut. Monthly maximum and minimum temperatures for 1900-1997 were obtained from NOAA's National Climatic Data Center, the NASA-Goddard Institute for Space Studies, and the Lamont-Doherty Earth Observatory of Columbia University for 24 weather stations within the region that are part of the U.S. Historical Climatology Network. Analysis of annual mean temperatures shows an increasing difference between NYC (Central Park weather station) and its surrounding region over the twentieth century. Analysis of the temperature differences over time between NY Central Park (NYCP) station and 23 regional weather stations classified according to distance and level of urbanization show a heat island effect existing in NYC, with mean temperatures in the NYCP Station generally higher than the surrounding stations, ranging from 1.20\\deg C to 3.02\\deg C. A difference of at least 1\\deg C already existed at the beginning of the 20th century between the mean temperature in NYC and its surrounding rural areas, and this difference increased over the twentieth century. There was a significant decrease in the monthly and seasonal variability of the UHI effect over the century. Temperature extremes and summertime heat can create heat stress and other health consequences for urban residents. Public health impacts are assessed as the proportion of heat-related regional mortality estimated to be attributable to New York City's heat island effect during an average 1990's summer. Concentration-response functions describing the temperature-mortality relationship in NYC derived from the epidemiological literature are used to estimate numbers of deaths in a typical 1990s summer and those attributable to the city's heat island effect. The techniques and potential public health benefits of a pilot project to mitigate the heat island effect in NYC will be discussed.

Rosenthal, J. E.; Knowlton, K. M.; Rosenzweig, C.; Goldberg, R.; Kinney, P. L.

2003-12-01

298

Variability in solar radiation and temperature explains observed patterns and trends in tree growth rates across four tropical forests  

PubMed Central

The response of tropical forests to global climate variability and change remains poorly understood. Results from long-term studies of permanent forest plots have reported different, and in some cases opposing trends in tropical forest dynamics. In this study, we examined changes in tree growth rates at four long-term permanent tropical forest research plots in relation to variation in solar radiation, temperature and precipitation. Temporal variation in the stand-level growth rates measured at five-year intervals was found to be positively correlated with variation in incoming solar radiation and negatively related to temporal variation in night-time temperatures. Taken alone, neither solar radiation variability nor the effects of night-time temperatures can account for the observed temporal variation in tree growth rates across sites, but when considered together, these two climate variables account for most of the observed temporal variability in tree growth rates. Further analysis indicates that the stand-level response is primarily driven by the responses of smaller-sized trees (less than 20 cm in diameter). The combined temperature and radiation responses identified in this study provide a potential explanation for the conflicting patterns in tree growth rates found in previous studies.

Dong, Shirley Xiaobi; Davies, Stuart J.; Ashton, Peter S.; Bunyavejchewin, Sarayudh; Supardi, M. N. Nur; Kassim, Abd Rahman; Tan, Sylvester; Moorcroft, Paul R.

2012-01-01

299

Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions  

NASA Astrophysics Data System (ADS)

Gaseous elemental mercury (GEM) measurements at Alert, Canada, from 1995 to 2007 were analyzed for statistical time trends and for correlations with meteorological and climate data. A significant decreasing trend in annual GEM concentration is reported at Alert, with an estimated slope of -0.0086 ng m-3 yr-1 (-0.6% yr-1) over this 13-year period. It is shown that there has been a shift in the month of minimum mean GEM concentration from May to April due to a change in the timing of springtime atmospheric mercury depletion events (AMDEs). These AMDEs are found to decrease with increasing local temperature within each month, both at Alert and at Amderma, Russia. These results support the temperature dependence suggested by previous experimental results and theoretical kinetic calculations on both bromine generation and mercury oxidation and highlight the potential for changes in Arctic mercury chemistry with climate. A correlation between total monthly AMDEs at Alert and the Polar/Eurasian Teleconnection Index was observed only in March, perhaps due to higher GEM inputs in early spring in those years with a weak polar vortex. A correlation of AMDEs at Alert with wind direction supports the origin of mercury depletion events over the Arctic Ocean, in agreement with a previous trajectory study of ozone depletion events. Interannual variability in total monthly depletion event frequency at Alert does not appear to correlate significantly with total or first-year northern hemispheric sea ice area or with other major teleconnection patterns. Nor do AMDEs at either Alert or Amderma correlate with local wind speed, as might be expected if depletion events are sustained by stable, low-turbulence atmospheric conditions. The data presented here - both the change in timing of depletion events and their relationship with temperature - can be used as additional constraints to improve the ability of models to predict the cycling and deposition of mercury in the Arctic.

Cole, A. S.; Steffen, A.

2010-05-01

300

Comparing variability and trends in observed and modelled global-mean surface temperature  

Microsoft Academic Search

The observed evolution of the global-mean surface temperature over the twentieth century reflects the combined influences of natural variations and anthropogenic forcing, and it is a primary goal of climate models to represent both. In this study we isolate, compare, and remove the following natural signals in observations and in climate models: dynamically induced atmospheric variability, the El Niño-Southern Oscillation,

John C. Fyfe; Nathan P. Gillett; David W. J. Thompson

2010-01-01

301

Detecting seasonal signals in Holocene sea surface temperature trends by satellite-model-proxy integration  

Microsoft Academic Search

Past sea surface temperatures (SSTs) are routinely estimated from organic and inorganic remains of fossil phytoplankton or zooplankton organisms, recovered from sea floor sediments. These paleo proxies are usually interpreted to represent annual mean climate conditions, although potential seasonal biases have often been acknowledged, for example when systematic deviations among different types of proxies occur. However, such discrepancies are unresolvable

Birgit Schneider; Guillaume Leduc

2010-01-01

302

Accounting for the effects of volcanoes and ENSO in comparisons of modeled and observed temperature trends  

Microsoft Academic Search

Several previous studies have attempted to remove the effects of explosive volcanic eruptions and El Niño-Southern Oscillation (ENSO) variability from time series of globally averaged surface and tropospheric temperatures. Such work has largely ignored the nonzero correlation between volcanic signals and ENSO. Here we account for this collinearity using an iterative procedure. We remove estimated volcano and ENSO signals from

B. D. Santer; T. M. L. Wigley; C. Doutriaux; J. S. Boyle; J. E. Hansen; P. D. Jones; G. A. Meehl; E. Roeckner; S. Sengupta; K. E. Taylor

2001-01-01

303

Long-Term Temperature Trends and Tree Growth in the Taymir Region of Northern Siberia  

Microsoft Academic Search

The northernmost conifers in the world are located well above the Arctic Circle in the Taymir region of northern Siberia and have been recording the thermal environment for centuries to millennia. The trees respond to temperatures beyond the narrow season of actual cambial cell division by means of root growth, photosynthesis, lignification of cell walls, and other biochemical processes. Data

Gordon C. Jacoby; Nikolai V. Lovelius; Oleg I. Shumilov; Oleg M. Raspopov; Juri M. Karbainov; David C. Frank

2000-01-01

304

Trends, spectral characteristics, and rainfall relationships of low-latitude sea surface temperatures at different longitudes  

Microsoft Academic Search

The sea surface temperature (SST) data for low latitudes in the Pacific, Atlantic, and Indian Oceans for 1950-1996 (47 years) showed different seasonal variation patterns at different longitudes. When the seasonal patterns were subtracted from the monthly values, the deseasoned residuals showed considerable anomalies (interannual variability). In the Pacific the main features were the El Niño events. In the Atlantic,

R. P. Kane

2000-01-01

305

High-dynamic-range decibel-linear IF variable-gain amplifier with temperature compensation for WCDMA applications  

Microsoft Academic Search

This paper presents the design and simulated performance of a novel intermediate-frequency variable-gain amplifier for Wideband Code-Division Multiple Access transmitters. A compensation technique for parasitic coupling is proposed which allows the very high dynamic range of 85 dB to be attained using a single variable-gain stage. Temperature compensation and decibel-linear control are achieved by means of a proper bias network

Francesco Carrara; Pietro Filoramo; Giovanni Palmisano

2003-01-01

306

Iterated Application of a Linear Inverse Temperature Model to Lake Michigan SSTs Generated by CH3D  

NASA Astrophysics Data System (ADS)

A methodology is presented describing the adjustment of a Lake Michigan hydrodynamic simulation through iterated application of a linear inverse temperature model. CH3D, a numerical model developed by the U.S. Army Corps of Engineers, is used to generate Lake Michigan surface temperatures for Mar 14, 2000. The simulation is initiated from Jan 1, 2000 under hourly windstress observations using a spatially uniform eddy diffusivity field. An inverse model is derived from the 2-d linear temperature diffusion equation which solves for eddy diffusivity given a surface temperature field. Observational SSTs are blended with model predicted temperatures and the inverse model is applied resulting in an adjustment to a spatially non-uniform eddy diffusivity field. The lake simulation is then re-initialized for the same time period with the refined diffusivity field. The process is repeated until the diffusivity field converges. The technique is tested using Great Lakes Forecasting System SST model output as a substitute for observational data, but the method is suitable for NOAA satellite SST data. This work was supported by the National Science Foundation.

Shore, J. A.; Guo, Y.; Bedford, K. W.

2002-12-01

307

The Interaction Between Trends and Periodical Components in Air and Soil Temperature Time-Series Over the Asian Territory of Russia  

Microsoft Academic Search

We used Singular Spectrum Analysis (SSA) to detect trend and periodic components (rhythms) in annual and seasonal time series of surface air temperature (SAT) and of soil temperature (ST) at depths of 40, 160, and 320 cm, for the northern (to the north of the 60th latitude) and southern (to the south of the 60th latitude) parts of Western Siberian

S. M. Chudinova; T. Zhang; R. G. Barry; V. Sorokovikov; D. Gilichinsky

2004-01-01

308

Removal of linear alkylbenzene sulfonates and their degradation intermediates at low temperatures during activated sludge treatment  

Microsoft Academic Search

The degradation of linear alkylbenzene sulfonates and their degradation intermediates (sulfophenylcarboxylic acids) has been characterized at 9°C in an activated sludge pilot plant. After an adequate adaptation period (20 days), LAS primary degradation exceeds 99% and takes place preferentially for long alkyl chain homologues and external isomers. LAS homologues in the reactor are preferentially sorbed onto particulate matter, while sulfophenylcarboxylic

V. M. León; C. López; P. A. Lara-Martín; D. Prats; P. Varó; E. González-Mazo

2006-01-01

309

Temperature distribution in a uniform medium heated by linear absorption of a Gaussian light beam  

Microsoft Academic Search

The linear-diffusion equation is considered for a positive half-space with heat sources represented by Gaussian functions in the transverse plane and by exponential decay along the longitudinal axis. The exact solution is presented as a single quadrature of the complementary error function (erfc). The approximate solution is suggested in the form of the product of two Gaussian functions and the

Pablo Loza; Roberto Ortega; Dmitri Kouznetsov

1994-01-01

310

Identifying Western Montana Climate Trends using 50 years of Temperature and Precipitation records for applications in ecosystem process models such as Biome-BGC.  

NASA Astrophysics Data System (ADS)

It's increasingly clear that Global Climate change will affect regions of the earth in different ways. This study examines meteorological station records from the National Climatic Data Center for selected Western Montana Stations in order to identify yearly and seasonal temperature, precipitation, snow pack and hydrologic trends over the last 50 years. Once identified, these trends are used to make projections for the next 50 years which can be used to drive regionally applicable ecosystem process models such as Biome-BGC.

Holbrook, S. L.; Heinsch, F.; Running, S. W.

2007-05-01

311

Extreme climatic events drive mammal irruptions: regression analysis of 100-year trends in desert rainfall and temperature.  

PubMed

Extreme climatic events, such as flooding rains, extended decadal droughts and heat waves have been identified increasingly as important regulators of natural populations. Climate models predict that global warming will drive changes in rainfall and increase the frequency and severity of extreme events. Consequently, to anticipate how organisms will respond we need to document how changes in extremes of temperature and rainfall compare to trends in the mean values of these variables and over what spatial scales the patterns are consistent. Using the longest historical weather records available for central Australia - 100 years - and quantile regression methods, we investigate if extreme climate events have changed at similar rates to median events, if annual rainfall has increased in variability, and if the frequency of large rainfall events has increased over this period. Specifically, we compared local (individual weather stations) and regional (Simpson Desert) spatial scales, and quantified trends in median (50th quantile) and extreme weather values (5th, 10th, 90th, and 95th quantiles). We found that median and extreme annual minimum and maximum temperatures have increased at both spatial scales over the past century. Rainfall changes have been inconsistent across the Simpson Desert; individual weather stations showed increases in annual rainfall, increased frequency of large rainfall events or more prolonged droughts, depending on the location. In contrast to our prediction, we found no evidence that intra-annual rainfall had become more variable over time. Using long-term live-trapping records (22 years) of desert small mammals as a case study, we demonstrate that irruptive events are driven by extreme rainfalls (>95th quantile) and that increases in the magnitude and frequency of extreme rainfall events are likely to drive changes in the populations of these species through direct and indirect changes in predation pressure and wildfires. PMID:23170202

Greenville, Aaron C; Wardle, Glenda M; Dickman, Chris R

2012-09-21

312

Design, simulation, fabrication, and testing of medium temperature, linear Fresnel reflector collectors  

NASA Astrophysics Data System (ADS)

Linear Fresnel reflectors were investigated with respect to performance in a solar collection system for the production of process heat or for use with absorption chillers. Computer models were developed for both north-south and east-west tracking linear concentrators composed of from 6 to 16 segments. The results were used to select parameters for two experimental arrays and to develop design criteria. Good correlation between the model and the experimental arrays is demonstrated over a limited range of tests. The model is used to make comparisons of north-south and east-west arrays for a range of parameters including array length, tilt angle, and the segment width/spacing ratio for periods up to one year. Arrays were designed and built with common materials, common sizes, and low cost technology. System economics were evaluated.

McCalla, H. N.

1981-11-01

313

Instability-Driven Limits on Ion Temperature Anisotropy in the Solar Wind: Observations and Linear Vlasov Theory  

NASA Astrophysics Data System (ADS)

Kinetic microinstabilities in the solar wind arise when its non-thermal properties become too extreme. This thesis project focused specifically on the four instabilities associated with ion temperature anisotropy: the cyclotron, mirror, and parallel and oblique firehose instabilities. Numerous studies have provided evidence that proton temperature anisotropy in the solar wind is limited by the actions of these instabilities. For this project, a fully revised analysis of data from the Wind spacecraft's Faraday cups and calculations from linear Vlasov theory were used to extend these findings in two respects. First, theoretical thresholds were derived for the alpha-particle temperature anisotropy instabilities, which were then found to be consistent with a statistical analysis of Wind alpha-particle data. This suggests that alpha-particles, which constitute only about 5% of ions in the solar wind, are nevertheless able to drive temperature anisotropy instabilities. Second, a statistical analysis of Wind proton data found that proton temperature was significantly enhanced in plasma unstable due to proton temperature anisotropy. This implies that extreme proton temperature anisotropies in solar wind at 1 AU arise from ongoing anisotropic heating (versus cooling from, e.g., CGL double adiabatic expansion). Together, these results provide further insight into the complex evolution of the solar wind's non-fluid properties.

Maruca, Bennett Andrew

314

Linear theory of electron temperature anisotropy instabilities: Whistler, mirror, and Weibel  

Microsoft Academic Search

A collisionless, homogeneous plasma in which the electron velocity distribution is a bi-Maxwellian with T$\\\\perp$e > T$\\\\parallel$e, where the directional subscripts refer to directions relative to the background magnetic field Bo, can support the growth of two distinct instabilities. Linear dispersion theory predicts that the whistler anisotropy instability is excited with maximum growth rate gammam at k × Bo =

S. Peter Gary; Homa Karimabadi

2006-01-01

315

High efficiency linear compressor driven pulse tube cryocooler operating in liquid nitrogen temperature  

Microsoft Academic Search

The inertance tube is one of the key components of a pulse tube cryocooler. It has great influence not only on the efficiency\\u000a of the pulse tube cryocooler, but also on the efficiency of the linear compressor. Meanwhile, it is very difficult to predict\\u000a the impedance of an inertance tube because of the turbulent flow. In this paper, using a

JianYing Hu; XiaoTao Wang; Wei Dai; ErCang Luo; Yu Huang

2009-01-01

316

Application of a novel linear regression analysis to phase-space representations of air and soil temperature relationships  

NASA Astrophysics Data System (ADS)

Thermal orbits are phase-space representations of air and soil temperature relationships that are generated by plotting daily or monthly subsurface temperatures against corresponding air temperatures. The resulting illustrations are analogous to Lisajous figures, common in electronic circuit analysis, and have become useful descriptive tools that illustrate perturbations to air and soil temperature relationships in the presence of land- surface processes such as snow cover and ground freezing. The utility of thermal orbits has been limited, however, by the lack of quantitative metrics that describe changes in orbits across different environments or in time. Here this shortcoming is overcome by the development of a linear regression analysis that allows changes in thermal-orbit characteristics to be tracked in time, space and as a function of depth within the soil. We derive theoretical thermal-orbit regression equations by drawing from analyses of bivariate populations and solving for thermal-orbit regression slopes using the calculus of parameterized curves. Our resulting equations describe the expected evolution of thermal orbits with depth in a conductive soil regime. Deviations from conductive behavior can be measured with the thermal-orbit linear regression analysis and appear very responsive to changes in land-surface coupling conditions, allowing a means of measuring such changes with a single sensitive metric.

Smerdon, J.; Beltrami, H.; Gonzalez-Rouco, J.

2008-12-01

317

Midlatitude long-term temperature trend deduced from 17 years of Na lidar observations and its relationships to solar cycle effects and an observed episodic response  

Microsoft Academic Search

The Colorado State University (CSU) sodium lidar, first light in August 1989, has conducted regular observations of nocturnal mesopause region temperature and Na density continuously for more than 18 years since May 1991. The long-term nocturnal temperature record (1990-2007) has been used to reveal an episodic response after Mt. Pinatubo eruption, 11-year (and 27-day) solar cycle effect and temperature trend.

C. She; D. A. Krueger

2009-01-01

318

Test on Opto Couplers in the Linear Application Considering Temperature, Radiation and Vce Effects.  

National Technical Information Service (NTIS)

The test result for four different types of opto couplers (20 devices each) operating at very low current levels (lower than the test condition for logic operation) considering temperature, radiation and absolute value of forward voltage (Vce) effects are...

H. Spruijt K. Burrows J. Andersen S. Marsden J. Tilmant

1991-01-01

319

Detection of linear trends in multisensor time series in the presence of autocorrelated noise: Application to the chlorophyll-a SeaWiFS and MERIS data sets and extrapolation to the incoming Sentinel 3-OLCI mission  

NASA Astrophysics Data System (ADS)

The detection of long-term trends in geophysical time series is a key issue in climate change studies. This detection is affected by many factors: the size of the trend to be detected, the length of the available data sets, and the noise properties. Although the noise autocorrelation observed in geophysical time series does not bias the trend estimate, it affects the estimation of its uncertainty and consequently the ability to detect, or not, a significant trend. Ignoring the noise autocorrelation level typically leads to an overdetection of significant trends. Due to satellite lifetime, usually between 5 and 10 years, sea surface time series do not cover the same period and are acquired by different sensors with different characteristics. These differences lead to unknown level shifts (biases) between the data sets, which affect the trend detection. In this work, we develop a generic framework to detect and evaluate linear trends and level shifts in multisensor time series of satellite chlorophyll-a concentrations, as provided by the Medium Resolution Imaging Spectrometer instrument (MERIS) and sea-viewing wide field-of-view sensor (SeaWiFS) ocean-color missions. We also discuss the optimization of the observation networks, in terms of needed time overlap between successive time series to reduce the uncertainty on the detection of long-term trends. For the incoming Sentinel 3-Ocean and Land Color Instrument (3-OLCI) mission that should be launched at the end of 2014, we propose a global map of the number of months of observations to enhance the trend detection performed with the joint SeaWiFS-MERIS analysis.

Saulquin, Bertrand; Fablet, Ronan; Mangin, Antoine; Mercier, Grégoire; Antoine, David; Fanton d'Andon, Odile

2013-08-01

320

Monitoring MODIS thermal emissive band stability through brightness temperature trending of a ground target  

NASA Astrophysics Data System (ADS)

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites have been operating since 2000 and 2002, respectively. To date both instruments have demonstrated good calibration stability for the Thermal Emissive Bands (TEB). Maintaining calibration accuracy is an important issue, as the instrument age, for continued production of high quality science data. In this paper a strategy to track the stability of MODIS TEB measurements from launch to present using a cold ground target is discussed. The land surface in the area surrounding Dome Concordia, Antarctica (75.1 S, 123.4 E) is well characterized and stable in terms of surface temperature and emissivity. A research station at Dome Concordia provides a record of climate variables and the opportunities for satellite validation field campaigns. Both MODIS instruments overpass the site 7-10 times per day, including a near-nadir overpass once every 2-3 days. The long-term data record of near-nadir Dome Concordia MODIS TEB measurements is analyzed relative to the measurements of ground-based (Automated Weather Station) and other satellite (e.g. Atmospheric Infrared Sounder (AIRS)) sensors. This approach allows for the detection of any long-term calibration drift and the calibration consistency between Aqua and Terra MODIS. Additionally, a method to correct the observed cold scene bias for Aqua MODIS versus AIRS is discussed.

Wenny, Brian N.; Xiong, Xiaoxiong

2007-10-01

321

Hourly predictive Levenberg-Marquardt ANN and multi linear regression models for predicting of dew point temperature  

NASA Astrophysics Data System (ADS)

In this study, the ability of two models of multi linear regression (MLR) and Levenberg-Marquardt (LM) feed-forward neural network was examined to estimate the hourly dew point temperature. Dew point temperature is the temperature at which water vapor in the air condenses into liquid. This temperature can be useful in estimating meteorological variables such as fog, rain, snow, dew, and evapotranspiration and in investigating agronomical issues as stomatal closure in plants. The availability of hourly records of climatic data (air temperature, relative humidity and pressure) which could be used to predict dew point temperature initiated the practice of modeling. Additionally, the wind vector (wind speed magnitude and direction) and conceptual input of weather condition were employed as other input variables. The three quantitative standard statistical performance evaluation measures, i.e. the root mean squared error, mean absolute error, and absolute logarithmic Nash-Sutcliffe efficiency coefficient ( {| {{{Log}}({{NS}})} |} ) were employed to evaluate the performances of the developed models. The results showed that applying wind vector and weather condition as input vectors along with meteorological variables could slightly increase the ANN and MLR predictive accuracy. The results also revealed that LM-NN was superior to MLR model and the best performance was obtained by considering all potential input variables in terms of different evaluation criteria.

Zounemat-Kermani, Mohammad

2012-08-01

322

Variations and Trends in Global and Arctic Surface Temperature and Forecasts of Global Temperature a Year Ahead, 2000-2010. (Invited)  

NASA Astrophysics Data System (ADS)

We comment in some detail on the difficulties of correctly capturing recent Arctic warming accurately in global surface temperature data sets. We also discuss likely biases in modern sea surface temperature (SST) data worldwide and the effect these may have on assessed global temperatures The latter likely lead to a small underestimation of global warming trends in the last decade or so, and their effects may be comparable to uncertainties in or underestimations of Arctic temperatures. In this context, we present a multiple regression model of the main factors affecting global annual mean surface temperature (land and ocean combined) using the HadCRUT3, NCDC and GISS data sets for 1891-2009. The significant factors are net greenhouse gas forcing offset by anthropogenic aerosols, ENSO effects lagged by 3-5 months as measured by Nino 3.4 SSTs, solar and volcanic forcings and a small contribution from the Atlantic Multidecadal Oscillation. The regression equation verifies well when cross validated. This also allows the contributions of individual factors to be identified with more accuracy. We call this the simulation model. When restricted to 1891-1998, the simulation model reproduces the observed interannual variations of global temperature over 1999-2010 well. It therefore well reproduces the recent slowing of global warming whose magnitude, however, depend a little on assessments of recent Arctic temperature change which differ between HadCRUT3 and GISS especially. Slowing of the warming over 2001-2009 is likely partly to the 11 year solar cycle and recently published work elsewhere on a reduction of lower stratospheric water vapour. Nevertheless, we show that decadal temperature change from 1999-2008, as measured by HadCRUT3, is still consistent with future projections of global warming to 2100 under strong enhanced greenhouse forcing. The method we use includes a set of perturbed HadCM3 coupled climate model simulations. The statistical model has been adapted to forecast global surface temperature for the year ahead using data available in the previous November or December. A variation on this uses forecasts of Nino 3.4 SST from the Met Office’s Glosea3 or Glosea4 coupled seasonal forecast models. Using cross validation, the forecast models have been tested for their true forecast skill. Since 2008, initialised dynamical predictions from the DePreSys coupled decadal forecast model have been included and we briefly discuss these predictions. We assess the skill of the 11 real-time global surface temperature forecasts one year ahead issued in Press Releases over 2000-2010. Although the 2010 value is preliminary, we compare observations to date with our forecast of a record warm year. The two statistical models have evolved since this the first real time forecast in 2000, and were calibrated against earlier versions of Met Office global surface temperature data sets, so we verify against the contemporary data. Although there is a small warm bias when assessed against HadCRUT3 which may partly relate to underestimation of recent Arctic temperatures, the correlation coefficient between the 11 observed and forecast temperatures exceeds 0.70.

Folland, C. K.; Kennedy, J.; Colman, A.; Knight, J.; Stott, P.; Smith, D.; Parker, D. E.

2010-12-01

323

Weather Type classification over Chile; patterns, trends, and impact in precipitation and temperature  

NASA Astrophysics Data System (ADS)

The Andes Cordillera induces considerable disturbances on the structure and evolution of the pressure systems that influences South America. Different weather types for southern South America are derived from the daily maps of geopotential height at 850hPa corresponding to a 42 year period, spanning from 1958 to 2000. Here we have used the ECWMF ERA-40 reanalysis dataset to construct an automated version of the Lamb Weather type (WTs) classification scheme (Jones et al., 1993) developed for the UK. We have identified 8 basic WTs (Cyclonic, Anticyclonic and 6 main directional types) following a similar methodology to that previously adopted by Trigo and DaCamara, 2000 (for Iberia). This classification was applied to two regions of study (CLnorth and CLsouth) which differ 20° in latitude, so that the vast Chile territory could be covered. Then were assessed the impact of the occurrence of this weather types in precipitation in Chile, as well as in the distribution of precipitation and temperature fields (reanalysis data) in southern half of South America. The results allow to conclude that the precipitation in central region of Chile is largely linked with the class occurrence (concerning CLnorth) of cyclonic circulation and of West quadrant (SW, W and NW), despite of it's relatively low frequency. In CLsouth, for its part, it is verified that the most frequent circulation is from the west quadrant, although the associated amount of rainfall is lower than in CLnorth. There was also a general decrease of precipitation at local weather stations chosen in the considered period of study, particularly in austral winter.

Frias, T.; Trigo, R. M.; Garreaud, R.

2009-04-01

324

Recent summer precipitation trends in the Greater Horn of Africa and the emerging role of Indian Ocean sea surface temperature  

NASA Astrophysics Data System (ADS)

We utilize a variety of climate datasets to examine impacts of two mechanisms on precipitation in the Greater Horn of Africa (GHA) during northern-hemisphere summer. First, surface-pressure gradients draw moist air toward the GHA from the tropical Atlantic Ocean and Congo Basin. Variability of the strength of these gradients strongly influences GHA precipitation totals and accounts for important phenomena such as the 1960s-1980s rainfall decline and devastating 1984 drought. Following the 1980s, precipitation variability became increasingly influenced by the southern tropical Indian Ocean (STIO) region. Within this region, increases in sea-surface temperature, evaporation, and precipitation are linked with increased exports of dry mid-tropospheric air from the STIO region toward the GHA. Convergence of dry air above the GHA reduces local convection and precipitation. It also produces a clockwise circulation response near the ground that reduces moisture transports from the Congo Basin. Because precipitation originating in the Congo Basin has a unique isotopic signature, records of moisture transports from the Congo Basin may be preserved in the isotopic composition of annual tree rings in the Ethiopian Highlands. A negative trend in tree-ring oxygen-18 during the past half century suggests a decline in the proportion of precipitation originating from the Congo Basin. This trend may not be part of a natural cycle that will soon rebound because climate models characterize Indian Ocean warming as a principal signature of greenhouse-gas induced climate change. We therefore expect surface warming in the STIO region to continue to negatively impact GHA precipitation during northern-hemisphere summer.

Williams, A. Park; Funk, Chris; Michaelsen, Joel; Rauscher, Sara A.; Robertson, Iain; Wils, Tommy H. G.; Koprowski, Marcin; Eshetu, Zewdu; Loader, Neil J.

2012-11-01

325

Optimal Temperature Tracking Control of a Polymerization Batch Reactor by Adaptive Input-Output Linearization  

Microsoft Academic Search

The tracking of a reference temperature trajectory in a polymerization batch reactor is a common problem and has critical importance because the quality control of a batch reactor is usually achieved by implementing the trajectory precisely. In this study, only energy balances around a reactor are considered as a design model for control synthesis, and material balances describing con- centration

Kap Kyun Noh; Dongil Shin; Hyun Ku Rhee

2002-01-01

326

Temperature Dependent Non-Linear Response of a Wood Plastic Composite.  

National Technical Information Service (NTIS)

The present work investigates the effect of temperature on the viscoelastic strain response of a wood-plastic composite. A power law model and a Prony Series model for the viscoelastic strain response were investigated to describe the time dependent behav...

D. J. Pooler

2001-01-01

327

Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars  

Microsoft Academic Search

We present interferometric angular sizes for 12 stars with known planetary companions, for comparison with 28 additional main-sequence stars not known to host planets. For all objects we estimate bolometric fluxes and reddenings through spectral-energy distribution (SED) fits, and in conjunction with the angular sizes, measurements of effective temperature. The angular sizes of these stars are sufficiently small that the

Gerard T. van Belle; Kaspar von Braun

2009-01-01

328

Analyzing projected changes and trends of temperature and precipitation in the southern USA from 16 downscaled global climate models  

NASA Astrophysics Data System (ADS)

This study aims to examine how future climate, temperature and precipitation specifically, are expected to change under the A2, A1B, and B1 emission scenarios over the six states that make up the Southern Climate Impacts Planning Program (SCIPP): Oklahoma, Texas, Arkansas, Louisiana, Tennessee, and Mississippi. SCIPP is a member of the National Oceanic and Atmospheric Administration-funded Regional Integrated Sciences and Assessments network, a program which aims to better connect climate-related scientific research with in-the-field decision-making processes. The results of the study found that the average temperature over the study area is anticipated to increase by 1.7°C to 2.4°C in the twenty-first century based on the different emission scenarios with a rate of change that is more pronounced during the second half of the century. Summer and fall seasons are projected to have more significant temperature increases, while the northwestern portions of the region are projected to experience more significant increases than the Gulf coast region. Precipitation projections, conversely, do not exhibit a discernible upward or downward trend. Late twenty-first century exhibits slightly more precipitation than the early century, based on the A1B and B1 scenario, and fall and winter are projected to become wetter than the late twentieth century as a whole. Climate changes on the city level show that greater warming will happened in inland cities such as Oklahoma City and El Paso, and heavier precipitation in Nashville. These changes have profound implications for local water resources management as well as broader regional decision making. These results represent an initial phase of a broader study that is being undertaken to assist SCIPP regional and local water planning efforts in an effort to more closely link climate modeling to longer-term water resources management and to continue assessing climate change impacts on regional hazards management in the South.

Liu, Lu; Hong, Yang; Hocker, James E.; Shafer, Mark A.; Carter, Lynne M.; Gourley, Jonathan J.; Bednarczyk, Christopher N.; Yong, Bin; Adhikari, Pradeep

2012-08-01

329

Combined coherent anti-Stokes Raman spectroscopy and linear Raman spectroscopy for simultaneous temperature and multiple species measurements.  

PubMed

The simultaneous application of pure rotational coherent anti-Stokes Raman spectroscopy (CARS) and vibrational linear Raman spectroscopy (LRS) for the measurement of temperature and species concentrations in combustion systems is demonstrated. In addition to the standard rotational CARS experimental setup, only one detection system (spectrometer and intensified CCD camera) for the collection of the LRS signals was applied. The emission of the broadband dye laser used for CARS was shifted to the deep red to avoid interferences with the LRS signals located in the visible region. First experimental results from a vaporizing propane spray using an engine injection system are shown. PMID:16729111

Weikl, Markus C; Beyrau, Frank; Kiefer, Johannes; Seeger, Thomas; Leipertz, Alfred

2006-06-15

330

The integrated effects of temperature and stress on the formation of carbon linear atomic chains from graphene nanoribbons  

NASA Astrophysics Data System (ADS)

In situ experiments for graphene nanoribbons (GNRs) under electron beam irradiation show their thinning process. In particular, carbon linear atomic chains (LACs) were observed with high resolution transmission electron microscopy. In order to further understand the structural evolution and breaking mechanisms under stress and a wide range of temperatures that are yet to be fully explored by experiments, we use a molecular dynamics (MD) method to simulate the mechanical properties of GNRs. At high temperatures, our simulations produce non-hexagons and long LACs, whose main features are similar to the experimental results. We show how defects lead to the formation of definitely stable LACs, while at low temperatures, tensile deformation modes become brittle due to localized defects, which are attributed to insufficient thermal energy. In the simulation of zigzag GNRs at high temperatures, we unexpectedly obtained a fracture of the armchair-zigzag bridge connected by non-hexagons. These results offer insights for nanoelectronic device fabrication through a stress-temperature-controlled procedure on GNRs.

Zhu, Jianwei; Shi, Daning

2011-11-01

331

Impacts of land surface properties on temperature trends over the United States: Assessment using the US historical climate network and North American regional reanalysis datasets  

NASA Astrophysics Data System (ADS)

Temperature trends result from natural and anthropogenic factors. The latter was first seen as the result of radiative forcings, mainly the increasing concentrations of greenhouse gases. However, the increasing evidence that some non-radiative forcings such as land use/land cover (LULC) change may also be major factors contributing to climate change has prompted the National Research Council (NRC, 2005) to recommend the broadening of the climate change issue to include LULC processes as an important climate forcing. In addition, at the station level, increasing attention has been given to non-climatic biases that affect temperature records due to changes of the local environment at the vicinity of the station, changes in instrumentation and/or observations practices. This study (i) uses comparisons between in-situ observations and reanalysis datasets as an independent method to estimate temperature trends and variability and evaluate adjustments made to temperature records to correct non-climatic biases, (ii) uses the Observation Minus Reanalysis (OMR) method to investigate the impacts of sensitivity of surface temperature trends to LULC change over the conterminous United States and (iii) compares temperature and equivalent temperature (which is a variable that combines both temperature and moisture) and analyzes their respective correlation to vegetation properties. The comparison between the reanalysis and in-situ temperature observations shows that the reanalysis faithfully captures the intraseasonal and interannual variability of the station observations and also provides valuable information about the effects of individual station location (well or poorly sited) on temperature observations. Moreover, the comparison between surface observations and the North American Regional Reanalysis (NARR) using the Mean Square Difference (MSD) method is efficient in detecting LULC changes that took place at the vicinity of stations or changes related to observation practices, and in evaluating the impacts of adjustments performed on raw observations. OMR trends were found to be sensitive to land cover types and results indicate that land use conversion often results in more warming than cooling. Overall, our results confirm the robustness of the OMR method for capturing patterns of LULC changes at local and regional scales. The comparison between temperature and equivalent temperature demonstrates that atmospheric heat content may help to quantify the differences between surface and tropospheric trends, and hence the impact of land cover types on the surface temperature changes. Moreover, equivalent temperature is more correlated to biomass increase, vegetation transpiration and other surface moisture characteristics. Overall, this study suggests that in addition to considering the greenhouse gases-driven radiative forcings, multi-decadal and longer climate models simulations must further include LULC changes.

Fall, Souleymane

332

Recent Climatology, Variability, and Trends in Global Surface Humidity  

Microsoft Academic Search

In situ observations of surface air and dewpoint temperatures and air pressure from over 15 000 weather stations and from ships are used to calculate surface specific (q) and relative (RH) humidity over the globe (60°S-75°N) from December 1975 to spring 2005. Seasonal and interannual variations and linear trends are analyzed in relation to observed surface temperature (T) changes and

Aiguo Dai

2006-01-01

333

Linear stability of a compressible coaxial jet with continuous velocity and temperature profiles  

NASA Astrophysics Data System (ADS)

This paper describes an investigation of the stability of a jet with velocity and temperature profiles characteristic of the exit region for a turbofan engine. Because the bypass stream mixes with both the exhaust and the ambient air, these profiles contain thin layers in which the velocity and temperature may vary rapidly. As a consequence, multiple instability modes are possible. In accordance with Rayleigh's theorem for axisymmetric incompressible shear flows, it turns out that there are three possible modes, only two of which are unstable. We consider the effect on spatial growth rates of varying the diameter and velocity ratios, compressibility, and azimuthal wavenumber. Radiating modes, that are possible when the primary jet is heated, are also studied.

Perrault-Joncas, Dominique; Maslowe, Sherwin A.

2008-07-01

334

Complex energy relaxation at very low temperature in linear chain conductors with CDW's or SDW's  

NASA Astrophysics Data System (ADS)

We present four distinct features of the energy relaxation after switching off a small heat perturbation at very low temperatures in charge density wave- and spin density wave systems which demonstrate the glassy nature of their ground state. The nonexponential decay shows the evolving ``aging effect'' with a crossover between a non-equilibrium and a thermodynamical equilibrium. This relaxation is thermally activated with the activation energy of ~1-2 K, depending also on the duration of the perturbation.

Biljakovi?, K.; Starešini?, D.; Slijep?evi?, S.; Lasjaunias, J. C.; Monceau, P.

1993-12-01

335

Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars  

Microsoft Academic Search

We present interferometric angular sizes for 12 stars with known planetary\\u000acompanions, for comparison with 28 additional main-sequence stars not known to\\u000ahost planets. For all objects we estimate bolometric fluxes and reddenings\\u000athrough spectral energy distribution fits, and in conjunction with the angular\\u000asizes, measurements of effective temperature. The angular sizes of these stars\\u000aare sufficiently small that the

Gerard T. van Belle; Kaspar von Braun

2009-01-01

336

Design of High Temperature Ultrasonic Linear Arrays for Under-Sodium Viewing  

SciTech Connect

This paper summarizes the design process for high temperature ultrasonic phased array transducers for imaging in liquid sodium at temperatures up to 260C. The project is funded by the USDOE Generation IV Reactor Program and includes collaboration with the Japanese Atomic Energy Agency. The transducer system is being designed to be able to provide images inside a sodium cooled fast reactor, to support operation and maintenance activities including potentially location of looseor damaged parts during service outages. The prototype transducer array is being designed for 8 to 16, 3MHz rectangular lead niobate (K-81) or bismuth titanate (K-15) piezoelectric elements spaced at ?/2 (wavelength in sodium). A nickel or nickel alloy faceplate serves as the sodium wetting surface. Scan angle of the focused ultrasonic beam is ±30 degrees. Imaging spatial resolution is ? 1mm. The array is designed to be operated using a commercial phased array control system and it is planned that array testing will be performed in room temperature water, hot oil (260C), and molten sodium (260C).

Griffin, Jeffrey W.; Bond, Leonard J.; Jones, Anthony M.; Peters, Timothy J.

2010-11-07

337

Stratospheric and tropospheric SSU/MSU temperature trends and compared to reanalyses and IPCC CMIP5 simulations in 1979-2005  

NASA Astrophysics Data System (ADS)

Using the satellite temperature measurements from the Stratospheric Sounding Units (SSU) and Microwave Sounding Units (MSU including the advanced microwave sounding unit, AMSU) since 1979, the trends and uncertainties in the fifth Coupled Model Intercomparison Project (CMIP5) model simulations from the middle troposphere to the upper stratosphere (5-50 km) have been explored. The temperature trend discrepancies between the new generation reanalyses are investigated. Both the temporal character of the global mean temperature and the regional spatial pattern of the temperature trends are discussed. The results show that the CMIP5 model simulations reproduced common stratospheric cooling and tropospheric warming features although a significant discrepancy among the selected models was observed. For the temporal variation of the global mean temperature, the CMIP5 simulations reproduce the volcanic signal and were highly consistent with the SSU measurements in the upper stratosphere. In contrast, the CFSR and MERRA reanalyses (excluding ERA-I) exhibit a different result from the CMIP5 simulations. For the spatial variation of the temperature trends, the CMIP5 simulations displayed a different latitudinal-longitudinal pattern from SSU/MSU measurements in all six layers from the middle troposphere to the upper stratosphere. The CFSR reanalysis shows a good spatial correlation with satellite observations in the troposphere but poor spatial correlation in the stratosphere. The ERA-I and MERRA reanalyses have good spatial correlation in the upper stratosphere and an even better spatial correlation in the troposphere. Generally, the CMIP5 simulations significantly underestimated the stratospheric cooling in the tropics and substantially overestimated the cooling over the Antarctic in the MSU observations. The largest trend spread among the seven CMIP5 simulations is seen in both the south- and north-polar regions in the stratosphere and troposphere. The tropospheric spread values are generally smaller than the stratospheric spread values.

Powell, A. M., Jr.; Xu, J.; Zou, C.-Z.; Zhao, L.

2013-02-01

338

Direct evidence for continuous linear kinetics in the low-temperature degradation of Y-TZP.  

PubMed

The kinetics of the tetragonal to monoclinic (t-m) transformation of zirconia in a hydrous environment at 134°C and 3 bar pressure was studied. As surface X-ray diffraction, which is conventionally used to explore the progress, has a very limited depth of information, it distorts the quantitative results in a layer-on-layer situation and by itself is ill suited for this reason. Analyzing cross sections is more suitable; therefore, focused ion beam techniques were used to prepare artifact-free cuts. The material was subsequently investigated by scanning electron microscopy, electron backscatter diffraction and Raman spectroscopy. Only the combination of methods makes it possible to resolve the quantifiable details of the process. The transformation starts in the near-surface areas, forms a layer, and the growth of this layer proceeds into the bulk material following a simple linear time law (0.0624 ?m h(-1) for material in the chosen condition), without apparent retardation or limit. The progress yields a gradientless layer with a fixed amount of residual tetragonal zirconia (~27% for 3Y-TZP in the present conditions) separated from unaffected material by a boundary, which has a roughness only in the grain size range. The kinetics indicates a reaction rate control, where the hydration reaction is the key factor, but is modified by the stepwise access of water to the reaction front opened by the autocatalytic transformation of zirconia with a critical hydration level. PMID:22925608

Keuper, M; Eder, K; Berthold, C; Nickel, K G

2012-08-24

339

Linear Stability of a Compressible Coaxial Jet with Continuous Velocity and Temperature Profiles  

NASA Astrophysics Data System (ADS)

The stability of compressible coaxial jets is pertinent to the jet noise problem for turbofan engines. Because the bypass stream mixes with both the exhaust and the ambient air, multiple inflection points occur in the velocity and temperature profiles. In accordance with known theorems for the 2D incompressible case, it turns out that there are four unstable modes. We have computed the properties of all modes when the exhaust flow is at Mach one with profiles corresponding to the experiments reported by Papamoschou (AIAA-2003-1059). The variation with the diameter ratio and other parameters will be shown.

Maslowe, Sherwin; Perrault-Joncas, Dominique

2004-11-01

340

Recent climate trends and multisecular climate variability: temperature and precipitation during the cold season (October-March) in the Ebro Basin (NE of Spain) betrween 1500 and 2008  

Microsoft Academic Search

One of the goals of Paleoclimatology is to assess the importance and the exceptional nature of recent climate trends related to the anthropogenic climate change. Instrumental data enable the analysis of last century's climate, but do not give any information on previous periods' precipitation and temperature, during which there was no anthropic intervention on the climate system. Dendroclimatology is one

M.-A. Saz-Sanchez; J.-M. Cuadrat-Prats

2009-01-01

341

High-Temperature Ethanol Fermentation and Transformation with Linear DNA in the Thermotolerant Yeast Kluyveromyces marxianus DMKU3-1042?  

PubMed Central

We demonstrate herein the ability of Kluyveromyces marxianus to be an efficient ethanol producer and host for expressing heterologous proteins as an alternative to Saccharomyces cerevisiae. Growth and ethanol production by strains of K. marxianus and S. cerevisiae were compared under the same conditions. K. marxianus DMKU3-1042 was found to be the most suitable strain for high-temperature growth and ethanol production at 45°C. This strain, but not S. cerevisiae, utilized cellobiose, xylose, xylitol, arabinose, glycerol, and lactose. To develop a K. marxianus DMKU3-1042 derivative strain suitable for genetic engineering, a uracil auxotroph was isolated and transformed with a linear DNA of the S. cerevisiae ScURA3 gene. Surprisingly, Ura+ transformants were easily obtained. By Southern blot hybridization, the linear ScURA3 DNA was found to have inserted randomly into the K. marxianus genome. Sequencing of one Lys? transformant confirmed the disruption of the KmLYS1 gene by the ScURA3 insertion. A PCR-amplified linear DNA lacking K. marxianus sequences but containing an Aspergillus ?-amylase gene under the control of the ScTDH3 promoter together with an ScURA3 marker was subsequently used to transform K. marxianus DMKU3-1042 in order to obtain transformants expressing Aspergillus ?-amylase. Our results demonstrate that K. marxianus DMKU3-1042 can be an alternative cost-effective bioethanol producer and a host for transformation with linear DNA by use of S. cerevisiae-based molecular genetic tools.

Nonklang, Sanom; Abdel-Banat, Babiker M. A.; Cha-aim, Kamonchai; Moonjai, Nareerat; Hoshida, Hisashi; Limtong, Savitree; Yamada, Mamoru; Akada, Rinji

2008-01-01

342

High-temperature inert gas plasma magnetohydrodynamic energy conversion by using linear-shaped Faraday-type channel  

NASA Astrophysics Data System (ADS)

We describe high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a compact linear-shaped Faraday-type MHD electrical power generator is used. Short-time-duration single-pulse shock-tunnel-based experiments demonstrate the MHD energy conversion with varying total inflow temperature up to 9000 K and applied magnetic-flux density up to 4.0 T. The high-temperature plasma is transformed from the thermal-equilibrium state at the entrance to the weak-nonequilibrium state in the supersonic MHD channel. The discharge structure is reasonably homogeneous without suffering from serious streamer development. The power generation performance is monotonically improved by increasing total inflow temperature and strength of magnetic field. The enthalpy extraction efficiency of 13.1% and overall power density of 0.16 GW/m3 are attained. The local power density at the middle of the channel reaches 0.24 GW/m3.

Murakami, Tomoyuki; Zhuang, Yunqin; Okuno, Yoshihiro

2013-02-01

343

Variability and trend of diurnal temperature range in China and their relationship to total cloud cover and sunshine duration  

NASA Astrophysics Data System (ADS)

This study aims to investigate the effect of total cloud cover (TCC) and sunshine duration (SSD) in the variation of diurnal temperature range (DTR) in China during 1954-2009. As expected, the inter-annual variation of DTR was mainly determined by TCC. Analysis of trends of 30-year moving windows of DTR and TCC time series showed that TCC changes could account for that of DTR in some cases. However, TCC decreased during 1954-2009, which did not support DTR reduction across China. DTRs under sky conditions such as clear, cloudy and overcast showed nearly the same decreasing rate that completely accounted for the overall DTR reduction. Nevertheless, correlation between SSD and DTR was weak and not significant under clear sky conditions in which aerosol direct radiative effect should be dominant. Furthermore, 30-60% of DTR reduction was associated with DTR decrease under overcast conditions in south China. This implies that aerosol direct radiative effect appears not to be one of the main factors determining long-term changes in DTR in China.

Xia, X.

2013-05-01

344

Trends in Daily and Extreme Temperature and Precipitation Indices for the Countries of the Western Indian Ocean, 1975-2008  

NASA Astrophysics Data System (ADS)

In the framework of the project "Renforcement des Capacités des Pays de la COI dans le Domaine de l'Adaptation au Changement Climatique (ACCLIMATE)" (Comission de l'Ocean Indien, COI), a workshop on homogenization of climate data and climate change indices analysis was held in Mauritius in October 2009, using the successful format prepared by the CCl/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices. Scientists from the five countries in Western Indian Ocean brought daily climatological data from their region for a meticulous assessment of the data quality and homogeneity, and for the preparation of climate change indices which can be used for analyses of changes in climate extremes. Although the period of analysis is very short, it represents a seminal step for the compilation of longer data set and allows us to examine the evolution of climate extremes in the area during the time period identified as the decades where anthropogenic warming es larger than natural forcings. This study first presents some results of the homogeneity assessment using the software package RHtestV3 (Wang and Feng 2009) which has been developed for the detection of changepoints in climatological datasets. Indices based on homogenized daily temperatures and precipitations were also prepared for the analysis of trends at more than 50 stations across the region. The results show an increase in the percentage of warm days and warm nights over 1975-2008 while changes in extreme precipitations are not as consistent.

Aguilar, Enric; Vincent, Lucie A.

2010-05-01

345

Linear Stability of a Compressible Coaxial Jet with Continuous Velocity and Temperature Profiles  

NASA Astrophysics Data System (ADS)

The stability of compressible coaxial jets is pertinent to the jet noise problem for turbofan engines. Because the bypass stream mixes with both the exhaust and the ambient air, multiple inflection points occur in the velocity and temperature profiles. In accordance with Rayleigh's theorem for axisymmetric incompressible shear flows, it turns out that there are three possible modes, only two of which are unstable. We have computed the properties of these modes when the exhaust flow is at Mach one with profiles corresponding to the experiments reported by Papamoschou (AIAA-2003-1059). The variation with the diameter ratio and other parameters will be shown. An integration contour indented in the complex plane was required to deal with wavenumbers for which modes are slightly amplified or neutral. It was found that the less amplified mode is important in that there is instability for a much greater range of axial wavenumber.

Perrault-Joncas, Dominique

2005-11-01

346

Linear Theory of Weakly Amplified, Parallel Propagating, Transverse Temperature-anisotropy Instabilities in Magnetized Thermal Plasmas  

NASA Astrophysics Data System (ADS)

A rigorous analytical study of the dispersion relations of weakly amplified transverse fluctuations with wavevectors (\\vec{k}? \\vec{B}) parallel to the uniform background magnetic field \\vec{B} in an anisotropic bi-Maxwellian magnetized electron-proton plasma is presented. A general analytical instability condition is derived that holds for different values of the electron (Ae ) and proton (Ap ) temperature anisotropies. We determine the conditions for which the weakly amplified left-handed (LH) polarized Alfvén proton cyclotron and right-handed (RH) polarized Alfvén Whistler electron cyclotron branches can be excited. For different regimes of the electron plasma frequency phase speed w = ? p,e /(kc) these branches reduce to the RH- and LH-polarized Alfvén waves, RH-polarized high and low phase speed Whistler, RH-polarized proton, and LH-polarized electron cyclotron modes. Analytic instability threshold conditions are derived in terms of the combined temperature anisotropy A = T bottom/T par, the parallel plasma beta ?par = 8 ? nekBT par/B 2 and the electron plasma frequency phase speed w = ? p,e /(kc) for each mode. The results of our instability study are applied to the observed solar wind magnetic turbulence at values of 90 <= w <= 330. According to the existence conditions of the different instabilities, only the LH- and RH-polarized Alfvén wave instabilities can operate here. Besides the electron-proton mass ratio ? = 1836, the Alfvénic instability threshold conditions are controlled by the single observed plasma parameter w. The Alfvénic instability diagram explains well the observed confinement limits at small parallel plasma beta values in the solar wind.

Schlickeiser, R.; Skoda, T.

2010-06-01

347

LINEAR THEORY OF WEAKLY AMPLIFIED, PARALLEL PROPAGATING, TRANSVERSE TEMPERATURE-ANISOTROPY INSTABILITIES IN MAGNETIZED THERMAL PLASMAS  

SciTech Connect

A rigorous analytical study of the dispersion relations of weakly amplified transverse fluctuations with wavevectors ( k-vector {parallel} B-vector ) parallel to the uniform background magnetic field B-vector in an anisotropic bi-Maxwellian magnetized electron-proton plasma is presented. A general analytical instability condition is derived that holds for different values of the electron (A{sub e}) and proton (A{sub p}) temperature anisotropies. We determine the conditions for which the weakly amplified left-handed (LH) polarized Alfven proton cyclotron and right-handed (RH) polarized Alfven Whistler electron cyclotron branches can be excited. For different regimes of the electron plasma frequency phase speed w = {omega}{sub p,e}/(kc) these branches reduce to the RH- and LH-polarized Alfven waves, RH-polarized high and low phase speed Whistler, RH-polarized proton, and LH-polarized electron cyclotron modes. Analytic instability threshold conditions are derived in terms of the combined temperature anisotropy A = T{sub perpendicular}/T{sub {parallel}}, the parallel plasma beta {beta}{sub {parallel}} = 8 {pi} n{sub e}k{sub B}T{sub {parallel}}/B {sup 2} and the electron plasma frequency phase speed w = {omega}{sub p,e}/(kc) for each mode. The results of our instability study are applied to the observed solar wind magnetic turbulence at values of 90 {<=} w {<=} 330. According to the existence conditions of the different instabilities, only the LH- and RH-polarized Alfven wave instabilities can operate here. Besides the electron-proton mass ratio {mu} = 1836, the Alfvenic instability threshold conditions are controlled by the single observed plasma parameter w. The Alfvenic instability diagram explains well the observed confinement limits at small parallel plasma beta values in the solar wind.

Schlickeiser, R.; Skoda, T., E-mail: rsch@tp4.rub.d, E-mail: ts@tp4.rub.d [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2010-06-20

348

Comparison of kinetic and extended magnetohydrodynamics computational models for the linear ion temperature gradient instability in slab geometry  

NASA Astrophysics Data System (ADS)

We perform linear stability studies of the ion temperature gradient (ITG) instability in unsheared slab geometry using kinetic and extended magnetohydrodynamics (MHD) models, in the regime k?/k?<<1. The ITG is a parallel (to B) sound wave that may be destabilized by finite ion Larmor radius (FLR) effects in the presence of a gradient in the equilibrium ion temperature. The ITG is stable in both ideal and resistive MHD; for a given temperature scale length LTi0, instability requires that either k??i or ?i/LTi0 be sufficiently large. Kinetic models capture FLR effects to all orders in either parameter. In the extended MHD model, these effects are captured only to lowest order by means of the Braginskii ion gyro-viscous stress tensor and the ion diamagnetic heat flux. We present the linear electrostatic dispersion relations for the ITG for both kinetic Vlasov and extended MHD (two-fluid) models in the local approximation. In the low frequency fluid regime, these reduce to the same cubic equation for the complex eigenvalue ?=?r+i?. An explicit solution is derived for the growth rate and real frequency in this regime. These are found to depend on a single non-dimensional parameter. We also compute the eigenvalues and the eigenfunctions with the extended MHD code NIMROD, and a hybrid kinetic ?f code that assumes six-dimensional Vlasov ions and isothermal fluid electrons, as functions of k??i and ?i/LTi0 using a spatially dependent equilibrium. These solutions are compared with each other, and with the predictions of the local kinetic and fluid dispersion relations. Kinetic and fluid calculations agree well at and near the marginal stability point, but diverge as k??i or ?i/LTi0 increases. There is good qualitative agreement between the models for the shape of the unstable global eigenfunction for LTi0/?i=30 and 20. The results quantify how far fluid calculations can be extended accurately into the kinetic regime. We conclude that for the linear ITG problem in slab geometry with unsheared magnetic field when k?/k?<<1, the extended MHD model may be a reliable physical model for this problem when ?i/LTi0<10-2 and k??i<0.2.

Schnack, D. D.; Cheng, J.; Barnes, D. C.; Parker, S. E.

2013-06-01

349

Theory of coupled whistler-electron temperature gradient mode in high beta plasma: Application to linear plasma device  

SciTech Connect

This paper presents a theory of coupled whistler (W) and electron temperature gradient (ETG) mode using two-fluid model in high beta plasma. Non-adiabatic ion response, parallel magnetic field perturbation ({delta}B{sub z}), perpendicular magnetic flutter ({delta}B{sub perpendicular}), and electron collisions are included in the treatment of theory. A linear dispersion relation for whistler-electron temperature gradient (W-ETG) mode is derived. The numerical results obtained from this relation are compared with the experimental results observed in large volume plasma device (LVPD) [Awasthi et al., Phys. Plasma 17, 42109 (2010)]. The theory predicts that the instability grows only where the temperature gradient is finite and the density gradient flat. For the parameters of the experiment, theoretically estimated frequency and wave number of W-ETG mode match with the values corresponding to the peak in the power spectrum observed in LVPD. By using simple mixing length argument, estimated level of fluctuations of W-ETG mode is in the range of fluctuation level observed in LVPD.

Singh, S. K.; Awasthi, L. M.; Singh, R.; Kaw, P. K.; Jha, R.; Mattoo, S. K. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India)

2011-10-15

350

Theory of coupled whistler-electron temperature gradient mode in high beta plasma: Application to linear plasma device  

NASA Astrophysics Data System (ADS)

This paper presents a theory of coupled whistler (W) and electron temperature gradient (ETG) mode using two-fluid model in high beta plasma. Non-adiabatic ion response, parallel magnetic field perturbation (?Bz), perpendicular magnetic flutter (?B?), and electron collisions are included in the treatment of theory. A linear dispersion relation for whistler-electron temperature gradient (W-ETG) mode is derived. The numerical results obtained from this relation are compared with the experimental results observed in large volume plasma device (LVPD) [Awasthi et al., Phys. Plasma 17, 42109 (2010)]. The theory predicts that the instability grows only where the temperature gradient is finite and the density gradient flat. For the parameters of the experiment, theoretically estimated frequency and wave number of W-ETG mode match with the values corresponding to the peak in the power spectrum observed in LVPD. By using simple mixing length argument, estimated level of fluctuations of W-ETG mode is in the range of fluctuation level observed in LVPD.

Singh, S. K.; Awasthi, L. M.; Singh, R.; Kaw, P. K.; Jha, R.; Mattoo, S. K.

2011-10-01

351

Recent climate trends in Southern Africa  

NASA Astrophysics Data System (ADS)

The aim of this study is to describe and explain climate variability from 1901 to 2003 in southern hemisphere Africa. The monthly mean data used in this study are global grids for temperature and precipitation (0.5° x 0.5° spatial resolution) sea level pressure (SLP, 5° x 5°) and sea surface temperature (SST, 1° x 1°). The analyses of climate trends, based on linear regressions, were performed for several 30-year periods (1901-1930, 1931-1960, 1961-1990, 1974-2003) as well as for the whole 103-year period. Different monthly trend patterns could be pointed out on a regional scale. Maximum warming could be identified for central southern Africa during the MAM season and a slight cooling trend in Madagascar (in SON). Significant (95% level) precipitation trends were hardly found for the whole period due to the high precipitation variability. But during the shorter 30-year sub-periods, particular regions with significant trends could be pointed out. Negative precipitation trends during recent decades, however, seem to be weaker than previously reported. Highly significant long-term SST-trends reach highest values in mid- to higher southern latitudes. Concerning the SLP-data, trend analyses provide remarkable positive trends in the southern realm of the subtropical high-pressure systems. This can be interpreted as enforced trade winds. Monthly t-mode Principal Component Analyses for all available data sets have been applied in order to investigate the atmospheric dynamics which cause these climate trend patterns. The results of these t-mode PCAs confirm an intensified circulation in the subtropical regions, which is reflected by enforced subtropical high pressure-systems. The PC-time coefficients of these patterns depict strong positive trends.

Rathmann, J.; Jacobeit, J.

2009-04-01

352

Two Americas. Comparisons of U.S. Child Poverty in Rural, Inner City and Suburban Areas. A Linear Trend Analysis to the Year 2010.  

ERIC Educational Resources Information Center

|This analysis, part of a series on child poverty in America, contains an overview of child poverty trends over the period from 1959 to 1992 and projections of child poverty rates and levels by area of residence to the year 2010. Analyses, based on data from the Census Bureau, show a marked increase in the overall rate of child poverty since the…

Cook, John T.; Brown, J. Larry

353

Two Americas: Racial Differences in Child Poverty in the U.S. A Linear Trend Analysis to the Year 2010. Research in Progress Working Paper.  

ERIC Educational Resources Information Center

|This analysis is the third in the Center's series on child poverty in America. The first part of this study is a historical view of trends in child poverty by race and Hispanic origin for children in families below the age of 18 years. The second part presents projections of child poverty rates and levels for the three largest racial groups to…

Cook, John T.; Brown, J. Larry

354

COSMIC MICROWAVE BACKGROUND POLARIZATION AND TEMPERATURE POWER SPECTRA ESTIMATION USING LINEAR COMBINATION OF WMAP 5 YEAR MAPS  

SciTech Connect

We estimate cosmic microwave background (CMB) polarization and temperature power spectra using Wilkinson Microwave Anisotropy Probe (WMAP) 5 year foreground contaminated maps. The power spectrum is estimated by using a model-independent method, which does not utilize directly the diffuse foreground templates nor the detector noise model. The method essentially consists of two steps: (1) removal of diffuse foregrounds contamination by making linear combination of individual maps in harmonic space and (2) cross-correlation of foreground cleaned maps to minimize detector noise bias. For the temperature power spectrum we also estimate and subtract residual unresolved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our TT, TE, and EE power spectra are in good agreement with the published results of the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We find that the bias is small in almost all cases. A negative bias at low l in TT power spectrum has been pointed out in an earlier publication. We find that the bias-corrected quadrupole power (l(l + 1)C{sub l} /2{pi}) is 532 {mu}K{sup 2}, approximately 2.5 times the estimate (213.4 {mu}K{sup 2}) made by the WMAP team.

Samal, Pramoda Kumar; Jain, Pankaj [Department of Physics, Indian Institute of Technology, Kanpur (India); Saha, Rajib [Jet Propulsion Laboratory, M/S 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Delabrouille, Jacques [CNRS, Laboratoire APC, 10, rue Alice Domon et Leonie Duquet, 75205 Paris (France); Prunet, Simon [Institut d'Astrophysique de Paris, 98 bis Boulevard Arago, F-75014 Paris (France); Souradeep, Tarun [Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007 (India)

2010-05-01

355

Trend analysis of mean monthly maximum and minimum surface temperatures of the 1951–1990 period in Friuli-Venezia Giulia  

Microsoft Academic Search

Summary  The behaviour of seasonal and yearly average of the monthly means of maximum and minimum daily surface temperature, covering\\u000a the period 1951–90, in some stations of the Italian Hydrographic Service spread over the region of Friuli-Venezia Giulia has\\u000a been analysed by the Spearm test with the aim of determining a possible trend. A a variety of situations resulted, which are

M. Ceschia; A. Linussio; S. Micheletti

1994-01-01

356

Trend analysis of air temperature time series in Greece and their relationship with circulation using surface and satellite data: 1955–2001  

Microsoft Academic Search

Summary In this study, trends of annual and seasonal surface air temperature time series were examined for 20 stations in Greece for the period 1955–2001, and satellite data for the period 1980–2001. Two statistical tests based on the least square method and one based on the Mann-Kendall test, which is also capable of detecting the starting year of possible climatic

H. Feidas; T. Makrogiannis; E. Bora-Senta

2004-01-01

357

Impact of Temperature Trends on Short-Term Energy Demand, The (Released in the STEO September 1999)  

EIA Publications

The past few years have witnessed unusually warm weather, as evidenced by both mild winters and hot summers. The analysis shows that the 30-year norms--the basis of weather-related energy demand projections--donot reflect the warming trend or its regional and seasonal patterns.

Information Center

1999-09-01

358

Observed variability and trends in extreme temperature indices and rice-wheat productivity over two districts of Bihar, India—a case study  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to analyze the trends and variability in extreme temperature indices and its impact on rice-wheat productivity over two districts of Bihar, India, which is part of the middle Indo-Gangetic Basin. Mann-Kendall non-parametric test was employed for detection of trend and Sen slope was determined to quantify the magnitude of such trends. We have analyzed 10 extreme temperature indices for monthly and seasonally. The influence of extreme temperature indices on rice-wheat productivity was determined using correlation analysis. As far as Patna is concerned, if the number of cool days during September ?10, the rice productivity will increase due to the availability of sufficient duration to fill up the grain. However, higher warm days during all the months except June will affect the productivity. A significant negative correlation was noticed between maximum value of minimum temperature during September and rice productivity. Highly significant positive correlation was noticed between number of cool days during September with rice productivity while it was highly significant negative correlation in the case of number of warm days during the same month. As far as Samastipur is concerned, a negative correlation was noticed between wheat productivity and maximum value of maximum temperature (TXx) during February, but not statistically significant. The higher temperature may affect the kernel weight and thereby yield. It is seen that a critical value of TXx ?29.2 °C will be harmful to wheat crop during February. A significant positive correlation of number of cool nights with wheat productivity also supports the above relationship. The critical values of extreme temperature indices during rice and wheat growing months provide an indicator to assess the vulnerability of rice-wheat productivity to temperature for Patna and Samastipur districts and there is a need to prepare an adaptive strategy and also develop thermo-insensitive rice-wheat high yielding varieties suitable for this region to sustain rice-wheat productivity under projected climate change situation.

Subash, N.; Singh, S. S.; Priya, Neha

2013-01-01

359

The linear matching method applied to the high temperature life integrity of structures. Part 2. Assessments beyond shakedown involving changing residual stress fields  

Microsoft Academic Search

In an accompanying paper, the application of the linear matching method to the high temperature life assessment of structures was discussed and compared with assessment procedures, typical of those used in R5, for a range of cyclic problems within shakedown. These included shakedown and limit analyses, creep rupture analysis and the evaluation of rapid cycle creep deformation. In this paper,

H. F. Chen; A. R. S. Ponter; R. A. Ainsworth

2006-01-01

360

The linear matching method applied to the high temperature life integrity of structures. Part 1. Assessments involving constant residual stress fields  

Microsoft Academic Search

Design and life assessment procedures for high temperatures are based on ‘expert knowledge’ in structural mechanics and materials science, combined with simplified methods of structural analysis. Of these, R5 is one of the most widely used life assessment methods internationally with procedures based on reference stress techniques and shakedown calculations using linear elastic solutions. These have been augmented by full

H. F. Chen; A. R. S. Ponter; R. A. Ainsworth

2006-01-01

361

Chokoon'yo zairyo no hyomen kaishitsu himaku no tokusei hyoka ni kansuru kenkyu doko chosa. (Survey reports on technological trends in characterization and performance evaluation of protective coatings for use in ultrahigh temperature environments).  

National Technical Information Service (NTIS)

In order to learn the research trends in characteristics evaluation on surface reforming films made from ultra-high temperature materials, investigations and discussions were given on data and materials available inside and outside the country. Device ope...

1995-01-01

362

Temperature-Controlled Symmetry of Linear Polarization of Photoluminescence from InGaAs-Buried InAs/GaAs Quantum Dots  

NASA Astrophysics Data System (ADS)

We have succeeded in adjusting the symmetry of the linear polarization of exciton emission from self-assembled InAs/GaAs quantum dots by controlling the combination of temperature and composition of the InGaAs burying layer. The anisotropic shape of the Stranski--Krastanow-type quantum dot is a drawback to the generation of a polarization-entangled photon pair. We found that the polarization symmetry of the intensity and wavelength of photon emission depends on the sample temperature and the composition of the burying layer. The ground-state emission peaks in two linear polarization directions were tuned to overlap by lowering the temperature and using a high indium composition of the burying layer. Our results will aid in the development of an entangled-photon generator using the emission of exciton molecule in self-assembled quantum dots.

Mukai, Kohki; Kikushima, Kousuke; Tanaka, Tomoya; Nakashima, Seisuke

2013-06-01

363

Application of a novel linear regression analysis to phase-space representations of air and soil temperature relationships  

Microsoft Academic Search

Thermal orbits are phase-space representations of air and soil temperature relationships that are generated by plotting daily or monthly subsurface temperatures against corresponding air temperatures. The resulting illustrations are analogous to Lisajous figures, common in electronic circuit analysis, and have become useful descriptive tools that illustrate perturbations to air and soil temperature relationships in the presence of land- surface processes

J. Smerdon; H. Beltrami; J. Gonzalez-Rouco

2008-01-01

364

Natural selection and climate change: temperature-linked spatial and temporal trends in gene frequency in Fagus sylvatica  

Microsoft Academic Search

Rapid increases in global temperature are likely to impose strong directional selection on many plant populations, which must therefore adapt if they are to survive. Within populations, microgeographic genetic differentiation of individuals with respect to climate suggests that some populations may adapt to changing temperatures in the short-term through rapid changes in gene frequency. We used a genome scan to

ALISTAIR S. J UMP; JENNY M. H UNT; JOSÉ A. M ARTÍNEZ-IZQUIER; JOSEP PEÑUELAS

2006-01-01

365

Pacific sea surface temperatures in the twentieth century: Variability, trend, and connections to long-term hydroclimate variations over the Great Plains  

NASA Astrophysics Data System (ADS)

Pacific sea surface temperatures (SSTs) exhibit variability on interannual to centennial time scales. This dissertation addresses the challenge to separate SST natural variability from the nonstationary (largely anthropogenic) warming trend; and, based on the clarified variability/trend patterns, evaluate SST forcing of long-term hydroclimate variations over the Great Plains. First, a consistent analysis of natural variability and secular trend in the twentieth century Pacific SSTs is presented. By focusing on spatial and temporal recurrence, but without imposition of periodicity constraints, this single analysis discriminates between biennial, ENSO and decadal variabilities, leading to refined evolutionary descriptions; and between these natural variability modes and secular trend. Specifically, canonical ENSO variability is encapsulated in two modes that depict the growth and decay phases. Another interannual mode, energetic in recent decades, is shown linked to the west-to-east SST development seen in post--climate shift ENSOs: the non-canonical ESNO mode. Pacific decadal variability (PDV) is characterized by two modes: the Pan-Pacific mode has a horse-shoe structure with the closed end skirting the North American coast, and a quiescent eastern equatorial Pacific. The second decadal mode---the North Pacific mode---captures the 1976/77 climate shift and is closer to Mantua's Pacific Decadal Oscillation. Implicit accommodation of natural variability leads to a nonstationary SST trend, including midcentury cooling. These Pacific---and residual Atlantic---SST modes are then investigated for their connections to long-term hydroclimate variations over the Great Plains. During the Dust Bowl, dry anomalies in summer are found primarily linked to cool SSTs in the central tropical Pacific associated with non-canonical ENSO, as well as warm SSTs in the eastern tropical Atlantic associated with Atlantic Nino; in spring, however, dry anomalies are overwhelmed by connections to extratropical basins, when the cool phase of the SST trend coincided with a warm phase of the Atlantic Multidecadal Oscillation (AMO). Dry (wet) anomalies during the 1950s (1980s) are shown linked to the warm (cool) phase of the North Pacific decadal mode, as well as a warm (cool) AMO. The analysis suggests comparable importance of the Pacific and Atlantic Oceans in drought forcing, and highlights the role of the extratropical basins.

Guan, Bin

366

Trends in 1970-2010 summertime coastal California air temperatures:how HCN-corrections to COOP-data eliminated coastal-cooling  

NASA Astrophysics Data System (ADS)

The analysis of California COOP-site monthly-averaged summer Tmax-trends (1970-2005) by Lebassi et al. (2009, in J. of Climate) has been extended by: (a) lengthening the period to 2010, (b) trend-comparisons with newly released HCN data, and (c) calculation of trends in annual Tmax-values. HCN data sets are NCDC-homogenized subsets of the "most trusted" COOP sites; they include 12 (of the 52 COOP sites) in the San Francisco Bay Area and four (of 28) in the Southern California Air Basin (SoCAB). COOP data used as HCN1 data were adjusted by NCDC for the following biases: (a) time-of-observations, (b) spatial inhomogeneity, (c) missing values, (d) changes in thermometer type, and (e) urban warming, while HCN2 data do not include the last two corrections. Comparison of the 35- and 40-year COOP monthly-averaged Tmax-trends at the 16 HCN sites showed a high correlation (0.96). It also showed, however, that as the six inland warming-sites (COOP sites also HCN sites) of Lebassi et al. are now generally warming a slightly lower rate than five years ago, the seven comparable coastal-cooling sites are thus now generally cooling at a slightly lower rate. Coastal-cooling was shown by Lebassi et al. as a "reverse-reaction" to regional warming in inland areas, which triggers coastal sea breezes, and which thus increased cooling onshore flows. Comparison of HCN1 and COOP 35-year Tmax-trends shows little correlation (0.15), as the HCN1-corrections changed six of the seven COOP cooling-sites into HCN1 warming-sites. Only the site with largest original COOP cooling also showed HCN1 cooling. Similar comparisons between the COOP and HCN2 sites showed that HCN2-corrections changed fewer (only four) cooling-sites to warming (and with lower warming-rates); a low correlation (0.44) thus existed between trend-values. As many climate-change impacts (e.g., brown outs, heat stress, ozone peaks) depend on extreme Tmax-values, and not just averaged-monthly Tmax-values, the SoCAB distribution of the highest COOP Tmax-values anytime (at each of its 28 sites) during the period from 1970-2010 shows three sub-areas, with a boundary-temperature of 340C (and with the following ranges): (a) cool coastal (27-340C), (b) cool mountain-tops (28-340C), and (c) in-between hot-area (34-400C). The spatial distribution of the trends in these extreme Tmax-values show decreases up to -0.80C/dec in the coastal cooling areas and increases up to 0.60C/dec in the inland and mountain warming areas. Note that these trends are larger than the monthly-averaged Tmax-trends (about ±0.30C/dec) in Lebassi et al.

Bornstein, R. D.; Ghebreegziabher, A. T.; Lebassi, B.; González, J. E.

2011-12-01

367

Predictive data mining on Average Global Temperature using variants of ARIMA models  

Microsoft Academic Search

This paper analyzes and predicts the Average Global Temperature time series data. Three different variants of ARIMA models: Basic ARIMA, Trend based ARIMA and Wavelet based ARIMA have been used to predict the average global temperature. Out of all the three linear models, it has been observed that Trend based ARIMA method outperforms basic ARIMA method and Wavelet based ARIMA

C. Narendra Babu; B. Eswara Reddy

2012-01-01

368

The Interaction Between Trends and Periodical Components in Air and Soil Temperature Time-Series Over the Asian Territory of Russia  

NASA Astrophysics Data System (ADS)

We used Singular Spectrum Analysis (SSA) to detect trend and periodic components (rhythms) in annual and seasonal time series of surface air temperature (SAT) and of soil temperature (ST) at depths of 40, 160, and 320 cm, for the northern (to the north of the 60th latitude) and southern (to the south of the 60th latitude) parts of Western Siberian Plain, western and eastern parts of Central Siberian Plateau, Transbaikalia, and the territory located to the east of Lena River. We analyzed SAT data from 1902 to 1995 and ST data from 1960 to 1990. SSA-detected trends in the annual ST time series generally track trends detected in the annual SAT time series. They show a statistically significant increase in annual ST down to 320 cm for the Central Siberian Plateau, Transbaikalia, and south of Western Siberian Plain. The least soil warming between 1960 and 1990 is observed for the territory east of the Lena River. SSA-detected rhythms in the annual SAT and ST time series are coincident for the north of West Siberia Plain (7.7 years) and the western Central Siberian Plateau and Transbaikalia (2.7 years), and they are close but not coincident for eastern Central Siberian Plateau (4.7 and 4.3 years for SAT and ST, respectively). No coincident rhythms were found for the south of West Siberia Plain and territory located to the east of Lena River.For the majority of the study regions, winter, spring, and autumn ST tracked the 2- to 3-year periodic components of the corresponding SAT time series. Although summer ST over the Central Siberian Plateau and Transbaikalia coincides with the 5- to 7-year rhythms in the corresponding SAT, rhythms reconstructed in the annual ST time series are mainly coincident with those in the winter ST time series. Only winter ST over the western Central Siberian Plateau tracked the 9.8-year rhythms in the corresponding SAT time series. Trend and periodic components in the summer ST time series manifested themselves in annual ST time series only for the West Siberian Plain. This work was support by the North Atlantic Treaty Organization under a Grant awarded in 2003 (DGE-0312143), as well as NSF grants OPP-0229766 and OPP-0352910

Chudinova, S. M.; Zhang, T.; Barry, R. G.; Sorokovikov, V.; Gilichinsky, D.

2004-12-01

369

Recent Temperature Variations in Southern South America  

Microsoft Academic Search

Results from a critical appraisal of surface mean air temperature in Chile and Argentina and extreme air temperature in Chile during the present century are presented. Observations were homogenized to produce a set of time series as reliable as possible. Linear trends computed for the period 1933-1992 resulted in warming rates from 1 3t o 2 0 C 100 years

Benjamín Rosenblüth; Humberto A. Fuenzalida; Patricio Aceituno

1997-01-01

370

Precision and radiosonde validation of satellite gridpoint temperature anomalies. Part II: A tropospheric retrieval and trends during 1979-1990  

Microsoft Academic Search

TIROS-N satellite Microwave Sounding Unit (MSU) channel 2 data from different view angles across the MSU scan swath are combined to remove the influence of the lower stratosphere and much of the Upper troposphere on the measured brightness temperatures. The retrieval provides a sharper averaging kernel than the raw channel 2 weighting function, with a peak lowered from 50 kPa

Roy W. Spencer; John R. Christy

1992-01-01

371

Precision and Radiosonde Validation of Satellite Gridpoint Temperature Anomalies. Part II: A Tropospheric Retrieval and Trends during 1979-90  

Microsoft Academic Search

TIROS-N satellite Microwave Sounding Unit (MSU) channel 2 data from different view angles across the MSU man swath are combined to remove the influence of the lower stratosphere and much of the upper troposphere on the measured brightness temperatures. The retrieval provides a sharper averaging kernel than the raw channel 2 weighting function, with a peak lowered from 50 kPa

Roy W. Spencer; John R. Christy

1992-01-01

372

On the consistency of trends in radiation and temperature records and implications for the global hydrological cycle  

Microsoft Academic Search

Several studies indicate that incident shortwave radiation at land surfaces has significantly decreased between 1960 and 1990. Despite this, land temperature has increased by 0.4°C over the same period. From a surface energy balance perspective, this counterintuitive behaviour can be resolved either 1) through an increase in the downward longwave radiation which outweighs the decreased insolation or 2) through a

Martin Wild; Atsumu Ohmura; Hans Gilgen; Daniel Rosenfeld

2004-01-01

373

In situ monitoring of the acetylene decomposition and gas temperature at reaction conditions for the deposition of carbon nanotubes using linear Raman scattering.  

PubMed

To understand the reaction mechanisms taking place by growing carbon nanotubes via the catalytic chemical vapor deposition process, a strategy to monitor in situ the gas phase at reaction conditions was developed applying linear Raman spectroscopy. The simultaneous determination of the gas temperature and composition was possible by a new strategy of the evaluation of the Raman spectra. In agreement to the well-known exothermic decomposition of acetylene, a gas temperature increase was quantified when acetylene was added to the incident flow. Information about exhaust gas recirculation and location of the maximal acetylene conversion was derived from the composition measurements. PMID:20721212

Reinhold-López, Karla; Braeuer, Andreas; Popovska, Nadejda; Leipertz, Alfred

2010-08-16

374

A Non-Linear, Non-Stationary Look at Oceanic-Land-Atmospheric Surface Temperature Variations over the Past 150 and 350 Years  

NASA Astrophysics Data System (ADS)

A study of the Global Surface Temperature Anomaly (GSTA) and separate records constituted by oceanic, atmospheric, land, global temperature records, reveals several things: 1)while the reported rise in global surface temperatures over the latter part of the 19th Century, though the 20th Century and into the 21st Century, has been viewed largely as an atmospheric phenomena, our study shows that the Global Ocean is the key player in regulating the Earth's temperature; 2)there is a rich multi-mode, multi-decade variability of planetary temperatures over the past 160 years, and in one individual record, back 350 years; 3)in the 350 year record, we find periods of both cooling and warming; and 4)over the past 150 years the temperature trend displays an overall warming. However our computed rate of warming is significantly different than that declared by the IPCC 2007 Report. Moreover, this analysis reveals that the foundational definitions of weather and climate should be revisited.

Pietrafesa, L. J.

2010-12-01

375

Measurement of the temperature distribution within monodisperse combusting droplets in linear streams using two-color laser-induced fluorescence  

Microsoft Academic Search

Two-color laser-induced fluorescence can be use to perform space-averaged flying droplet temperature measurements. In this paper, the possibility to extend this technique to the measurement of the temperature distribution within a moving combusting droplet is considered and demonstrated. This technique may provide new experimental data related to the heat diffusion in liquid fuel droplets injected in high-temperature gas streams, for

G. Castanet; P. Lavieille; M. Lebouché; F. Lemoine

2003-01-01

376

Structure and mechanical properties of austenitic steel with low-temperature deformation under linear and plane-stress conditions  

Microsoft Academic Search

Conclusions 1.For metastable austenitic steel, plastically deformed at -160°C under conditions of linear and plane stress states, we obtained an analytical expression for stress-strain curves describing the strain hardening of the austenite and the resistance of the developed martensite to deformation. It was shown that, due to the effect of the type of stress state on the structure of the

S. B. Nizhnik; B. I. Koval'chuk; É. S. Istomina; E. A. Dmitrieva

1978-01-01

377

Evaluation of temperature gradients within combusting droplets in linear stream using two colors laser-induced fluorescence  

Microsoft Academic Search

The scope of this paper concerns the heating process of fuel droplets injected in a hot gaseous environment. The two colors laser-induced fluorescence technique allows measuring the temperature distribution within a droplet by scanning the droplet volume by a sufficiently small probe volume compared to the droplet volume itself. The temperature field is reconstructed using two approaches which have been

Guillaume Castanet; Alain Delconte; Fabrice Lemoine; Loïc Mees; Gèrard Gréhan

2005-01-01

378

Mechanical properties, glass transition temperature, and bond enthalpy trends of high metalloid Fe-based bulk metallic glasses  

NASA Astrophysics Data System (ADS)

Mechanical properties and glass transition temperatures (Tg) of Fe-Cr-Mo-P-C-B bulk metallic glasses containing up to 27 at. % metalloids have been studied. The shear modulus (G) is found to decrease with increasing metalloid content and a maximum plastic strain of ~3% is obtained, despite the increase in the number of strong metal-metalloid bonds. Also, Tg increases with the decrease in G, in contrast to usual behavior. By employing first-principles calculations, the results are discussed in light of atomic bonding and connectivity in the amorphous network. The findings are relevant to understanding ductility and glass transition of metallic glasses.

Gu, X. J.; Poon, S. Joseph; Shiflet, Gary J.; Widom, Michael

2008-04-01

379

Effect of the nonmonotonic temperature dependence of water density on free convection from a linear heat source  

Microsoft Academic Search

This paper presents the results of experimental studies of free convection from a heated wire in water for the two cases where\\u000a the water temperature is higher or lower than the temperature at which water has maximum density. It is shown that, in the\\u000a first case, the convective plume formed by heating rises, reaching the free surface. In the second

V. I. Bukreev; N. V. Gavrilov; A. V. Chebotnikov

2011-01-01

380

On the linearity of the high-temperature emission from 7LiF:Mg,Ti (TLD700)  

Microsoft Academic Search

It is known since the early 1970s [e.g., Jähnert, B., 1972. The response of TLD-700 thermoluminescent dosemeters to protons and alpha particles. Health Phys. 23, 112–114.] that the high-temperature emission (HTE) from LiF:Mg,Ti thermoluminescence (TL) phosphors shows a distinctly different LET dependence than the dominant glow peak 5. This behaviour of the high-temperature structure can be attributed to the earlier

T. Berger; M. Hajek

2008-01-01

381

Contribution to linearly programmed temperature gas chromatography. Further application of the Van den Dool-Kratz equation, and a new utilization of the Sadtler retention index library.  

PubMed

Programmed temperature retention indices (PTRIs) calculated according to the equations of Van den Dool and Kratz, Golovnya and Uraletz, and Erdey et al. (also referred to as Antoine's integrated equation) are used in this work. Precalculation of isotherm retention indices from the results of a linearly programmed temperature GC is also presented. Deviations between experimental and calculated isothermal retention indices are below 2 retention index units. A relative "volatility" retention index is defined, as a function of the "volatilities"of the solute and the bracket reference n-alkanes. The comparison of the "volatility" retention indices with the PTRIs obtained with the other above equations shows absolute deviations of up to 4 retention index units. Based on an earlier "equivalent" temperature concept and on Tekler's proviso, a novel way for the utilization of Sadtler's retention index database, which takes advantage of the 3 data supplied by the library, is proposed. PMID:18201710

Santiuste, José M; Tarján, Géza; Ullrich, Ede; Takács, József M

2008-01-16

382

Seasonal trend of photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature  

SciTech Connect

OAK-B135 Understanding seasonal changes in photosynthetic parameters and stomatal conductance is crucial for modeling long-term carbon uptake and energy fluxes of ecosystems. Gas exchange measurements of CO{sub 2} and light response curves on blue oak leaves (Quercus douglasii H. & A.) were conducted weekly throughout the growing season to study the seasonality of photosynthetic capacity (V{sub cmax}) and Ball-Berry slope (m) under prolonged summer drought and high temperature. A leaf photosynthetic model was used to determine V{sub cmax}. There was a pronounced seasonal pattern in V{sub cmax}. The maximum value of V{sub cmax}, 127 {micro}molm{sup -2} s{sup -1},was reached shortly after leaf expansion in early summer, when air temperature was moderate and soil water availability was high. Thereafter, V{sub cmax} declined as the soil water profile became depleted and the trees experienced extreme air temperatures, exceeding 40 C. The decline in V{sub cmax} was gradual in midsummer, however, despite extremely low predawn leaf water potentials ({Psi}{sub pd}, {approx} -4.0 MPa). Overall, temporal changes in V{sub cmax} were well correlated with changes in leaf nitrogen content. During spring leaf development, high rates of leaf dark respiration (R{sub d}, 5-6 {micro}mol m{sup -2} s{sup -1}) were observed. Once a leaf reached maturity, R{sub d} remained low, around 0.5 {micro}mol m{sup -2} s{sup -1}. In contrast to the strong seasonality of V{sub cmax}, m and marginal water cost per unit carbon gain ({partial_derivative}E/{partial_derivative}A) were relatively constant over the season, even when leaf {Psi}{sub pd} dropped to -6.8 MPa. The constancy of {partial_derivative}E/{partial_derivative}A suggests that stomata behaved optimally under severe water-stress conditions. We discuss the implications of our findings in the context of modeling carbon and water vapor exchange between ecosystems and the atmosphere.

Xu, L; Baldocchi, DD

2003-09-01

383

Mechanical properties, glass transition temperature, and bond enthalpy trends of high metalloid Fe-based bulk metallic glasses  

SciTech Connect

Mechanical properties and glass transition temperatures (T{sub g}) of Fe-Cr-Mo-P-C-B bulk metallic glasses containing up to 27 at. % metalloids have been studied. The shear modulus (G) is found to decrease with increasing metalloid content and a maximum plastic strain of {approx}3% is obtained, despite the increase in the number of strong metal-metalloid bonds. Also, T{sub g} increases with the decrease in G, in contrast to usual behavior. By employing first-principles calculations, the results are discussed in light of atomic bonding and connectivity in the amorphous network. The findings are relevant to understanding ductility and glass transition of metallic glasses.

Gu, X. J.; Poon, S. Joseph [Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714 (United States); Shiflet, Gary J. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904-4745 (United States); Widom, Michael [Department of Physics, Carnegie Mellon University, Pittsburgh, Philadelphia, Pennsylvania 15213 (United States)

2008-04-21

384

Trends in Sea Ice Cover, Sea Surface Temperature, and Chlorophyll Biomass Across a Marine Distributed Biological Observatory in the Pacific Arctic Region  

NASA Astrophysics Data System (ADS)

The northern Bering and Chukchi Seas in the Pacific Arctic Region (PAR) are among the most productive marine ecosystems in the world and act as important carbon sinks, particularly during May and June when seasonal sea ice-associated phytoplankton blooms occur throughout the region. Recent dramatic shifts in seasonal sea ice cover across the PAR should have profound consequences for this seasonal phytoplankton production as well as the intimately linked higher trophic levels. In order to investigate ecosystem responses to these observed recent shifts in sea ice cover, the development of a prototype Distributed Biological Observatory (DBO) is now underway in the PAR. The DBO is being developed as an internationally-coordinated change detection array that allows for consistent sampling and monitoring at five spatially explicit biologically productive locations across a latitudinal gradient: (1) DBO-SLP (south of St. Lawrence Island (SLI)), (2) DBO-NBS (north of SLI), (3) DBO-SCS (southern Chukchi Sea), (4) DBO-CCS (central Chukchi Sea), and (5) DBO-BCA (Barrow Canyon Arc). Standardized measurements at many of the DBO sites were made by multiple research cruises during the 2010 and 2011 pilot years, and will be expanded with the development of the DBO in coming years. In order to provide longer-term context for the changes occurring across the PAR, we utilize multi-sensor satellite data to investigate recent trends in sea ice cover, chlorophyll biomass, and sea surface temperatures for each of the five DBO sites, as well as a sixth long-term observational site in the Bering Strait. Satellite observations show that over the past three decades, trends in sea ice cover in the PAR have been heterogeneous, with significant declines in the Chukchi Sea, slight declines in the Bering Strait region, but increases in the northern Bering Sea south of SLI. Declines in the persistence of seasonal sea ice cover in the Chukchi Sea and Bering Strait region are due to both earlier sea ice breakup and later sea ice formation. Sea surface temperatures have also shown warming, where sites show significant warming particularly during August, September, and October. Satellite-derived chlorophyll-a concentrations over the past decade have shown trends seemingly in direct response to changing sea ice conditions, with increasing trends in chlorophyll-a concentrations when sea ice declines (and vice versa). In some cases, however, satellite-derived chlorophyll-a concentrations do not show expected changes with sea ice variability, indicating that limitations on biological productivity in this region are complex and spatially heterogeneous. An understanding of these spatial and temporal complexities impacting biological productivity is needed for the accurate prediction of how overall ecosystems may be altered with further expected warming sea surface temperatures and declines in sea ice cover.

Frey, K. E.; Grebmeier, J. M.; Cooper, L. W.; Wood, C.; Panday, P. K.

2011-12-01

385

Explaining long-term trends in groundwater hydrographs  

Microsoft Academic Search

An ability to understand and interpret changes in groundwater levels is essential for sound management of groundwater resources. Various statistical methods have been developed to explain hydrograph trends. Most of these operate on the assumption that groundwater trends are linear or best represented by short linear segments. However there is clear evidence that many hydrograph trends are non- linear. For

R. Ferdowsian; D. J. Pannell

386

Long-term trends in sea surface temperature in coastal water in relation to large-scale climate change: A case study in Omura Bay, Japan  

NASA Astrophysics Data System (ADS)

Long-term trends in sea surface temperature (SST) in Omura Bay were investigated using heat balance estimates based on a daily data set obtained for 40 years (1955–1995) by the National Pearl Research Laboratory. SST during the heating period (from March to August) tended to decrease, whereas that during most of the cooling period (from September to February) increased during these 40 years. The maximum rates of SST decrease and increase were found to be 0.020 °C year?1 in August and 0.028 °C year?1 in January, respectively. The sea surface heat balance analysis revealed that shortwave radiation flux decreased in the heating period due to decrease in solar radiation, resulting in a decrease in SST. In the cooling period, the increase in SST was attributed to the decrease in latent and sensible heat fluxes due to increased air temperature and decreased wind speed. These climatic changes affecting SST in Omura Bay showed a close linkage with global dimming and the East Asian monsoon circulation.

Takeshige, Aigo; Takahashi, Tetsuya; Nakata, Hideaki; Kimura, Shingo

2013-09-01

387

Linear variable differential transformer (LVDT)-based elongation measurements in Advanced Test Reactor high temperature irradiation testing  

Microsoft Academic Search

New materials are being considered for fuel, cladding and structures in next generation and existing nuclear reactors. These materials can undergo significant dimensional and physical changes during high temperature irradiations. Currently, such changes are determined by repeatedly irradiating a specimen for a specified period of time in the Advanced Test Reactor (ATR) and then removing it from the reactor for

D. L. Knudson; J. L. Rempe

2012-01-01

388

Non-linear temperature oscillations in the plasma centre on Tore Supra and their interplay with MHD  

Microsoft Academic Search

Regular oscillations of the central electron temperature have been observed by means of ECE and SXR diagnostics during non-inductively driven discharges on Tore Supra. These oscillations are sustained by LHCD, do not have a helical structure and, therefore, cannot be ascribed as MHD phenomena. The most probable explanation of this oscillating regime (O-regime) is the assumption that the plasma current

V. S. Udintsev; G. Giruzzi; F. Imbeaux; J.-F. Artaud; X. Garbet; G. Huysmans; P. Maget; J.-L. Segui; A. Becoulet; G. T. Hoang; E. Joffrin; X. Litaudon; B. Saoutic

2004-01-01

389

Exploring linear data  

NSDL National Science Digital Library

This lesson connects statistics and linear functions. Students construct scatterplots, examine trends, and consider a line of best fit as they graph real-world data. They also investigate the concept of slope as they model linear data in a variety of settings that range from car repair costs to sports to medicine. Handouts for four activities, spread out over three class periods, are provided.

Mathematics, National C.

2008-02-25

390

Communication: Identical temperature dependence of the time scales of several linear-response functions of two glass-forming liquids  

NASA Astrophysics Data System (ADS)

The frequency-dependent dielectric constant, shear and adiabatic bulk moduli, longitudinal thermal expansion coefficient, and longitudinal specific heat have been measured for two van der Waals glass-forming liquids, tetramethyl-tetraphenyl-trisiloxane (DC704) and 5-polyphenyl-4-ether. Within the experimental uncertainties the loss-peak frequencies of the measured response functions have identical temperature dependence over a range of temperatures, for which the Maxwell relaxation time varies more than nine orders of magnitude. The time scales are ordered from fastest to slowest as follows: Shear modulus, adiabatic bulk modulus, dielectric constant, longitudinal thermal expansion coefficient, and longitudinal specific heat. The ordering is discussed in light of the recent conjecture that van der Waals liquids are strongly correlating, i.e., approximate single-parameter liquids.

Jakobsen, Bo; Hecksher, Tina; Christensen, Tage; Olsen, Niels Boye; Dyre, Jeppe C.; Niss, Kristine

2012-02-01

391

Two-dimensional temperature determination in the exhaust region of a laminar flat-flame burner with linear Raman scattering.  

PubMed

For planar temperature measurements in combusting flows, the well-established laser Raman technique has been further developed to provide two-dimensional local resolution. After excitation with a frequency-doubled Nd:YAG laser, the anti-Stokes and the Stokes Raman signals of the vibrational Q branch of molecular N(2) were detected at 473.3 and 607.3 nm, respectively. From the ratio of the two images, two-dimensional temperature distributions have been obtained by application of an analytical function, which was determined from theoretically calculated Raman spectra. Time-averaged measurements have been performed in the exhaust region of an atmospheric-pressure laminar CH(4)/air flat-flame burner for different equivalence ratios. The accuracy and precision of the results are discussed in combination with the prospects for time-resolved single-pulse measurements. PMID:18259572

Rabenstein, F; Leipertz, A

1997-09-20

392

Northern Hemisphere Meridional and Zonal Temperature Gradients and their Relation to Hydrologic Extremes at Mid-latitudes: Trends, Variability and Link to Climate Modes in Observations and Simulations  

NASA Astrophysics Data System (ADS)

The mid-latitude storm track, which depends on how the jet stream dynamics (mean flow and transient eddies coupled to it) are modulated by large scale ocean-land boundary conditions, is a factor in determining moisture and heat transport associated with extreme hydrologic events, such as floods and droughts. These boundary conditions depend in turn on both the state of evolution of the known interannual and multi-decadal natural variability (e.g., the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO)) and on changes in meridional and zonal surface temperature gradients (Equator-to-Pole and Ocean-Land contrast, respectively) due to anthropogenic forcing. We examine the historical trends of the seasonal NH Equator-to-Pole temperature Gradient (EPG) and the Ocean-Land temperature Contrast (OLC), their probability structure, and their potential relation to anthropogenic warming. We investigate how different combinations of EPG and OLC are associated with precipitation anomalies at mid-latitudes, with a focus in the US and European region. Figure 1 shows an example of how the combination of high OLC- low EPG is associated with positive precipitation anomalies in the aforementioned regions (upper panel), while the combination of low EPG-high OLC is linked to average conditions or negative precipitation anomalies (lower panel), data from Eischeid et al. (1991). We also explore their relation to modes of variability, such as ENSO, as exhibited in observational data and GCM simulations, and utilize GCM projections to estimate potential changes in the frequency and persistence of certain combinations of EPG and OLC associated with precipitation anomalies under climate change scenarios. Winter (DJF) precipitation anomalies for two cases of combinations of EPG and OLC. (a) High OLC and low EPG corresponds to positive anomalies. (b) Low OLC and high EPG corresponds to near zero or negative anomalies for most regions. Data from Eischeid et al (1991).

Karamperidou, C.; Lall, U.; Cioffi, F.

2010-12-01

393

Influence of Chemical Cross-Linking on the Over Voltage Positive Temperature Coefficient of Linear Low Density Polyethylene/carbon Black/aluminum Hydroxide Nano Composites  

NASA Astrophysics Data System (ADS)

The effect of cross-linking of blends on the stability of positive temperature coefficient (PTC) and the elimination of negative temperature coefficient (NTC) were investigated. Linear low density polyethylene (LLDPE) was chemically cross-linking with various amounts of dicumyl peroxide (DCP). The resulting of cross-linking structure of composites was analyzed by gel content, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). By the effect of DCP, not only a high PTC intensity appeared, but also was the NTC effect of the composite eliminated. The PTC intensity reached six orders of magnitude for the LLDPE/DCP(0.10 wt%)/CB/Al(OH)3 composite, and successfully passed the test of over-voltage resistance.

Huang, C. Y.; Tsai, C. S.; Tsao, K. Y.

2008-08-01

394

Linear variable differential transformer (LVDT)-based elongation measurements in Advanced Test Reactor high temperature irradiation testing  

NASA Astrophysics Data System (ADS)

New materials are being considered for fuel, cladding and structures in next generation and existing nuclear reactors. These materials can undergo significant dimensional and physical changes during high temperature irradiations. Currently, such changes are determined by repeatedly irradiating a specimen for a specified period of time in the Advanced Test Reactor (ATR) and then removing it from the reactor for evaluation. The labor and time to remove, examine and return irradiated samples for each measurement make this approach very expensive. In addition, such techniques provide limited data and may disturb the phenomena of interest. To resolve these issues, an instrumented creep testing capability is being developed for specimens irradiated under pressurized water reactor coolant conditions in the ATR at the Idaho National Laboratory (INL). This paper reports the status of INL efforts to develop this testing capability. In addition to providing an overview of in-pile creep test capabilities available at other test reactors, this paper focuses on efforts to design and evaluate a prototype test rig in an autoclave at INL's High Temperature Test Laboratory.

Knudson, D. L.; Rempe, J. L.

2012-02-01

395

Linear variable differential transformer (LVDT)-based elongation measurements in Advanced Test Reactor high temperature irradiation testing  

SciTech Connect

New materials are being considered for fuel, cladding, and structures in next generation and existing nuclear reactors. These materials can undergo significant dimensional and physical changes during high temperature irradiations. Currently, such changes are determined by repeatedly irradiating a specimen for a specified period of time in the Advanced Test Reactor (ATR) and then removing it from the reactor for evaluation. The labor and time to remove, examine, and return irradiated samples for each measurement makes this approach very expensive. In addition, such techniques provide limited data and may disturb the phenomena of interest. To resolve these issues, an instrumented creep testing capability is being developed for specimens irradiated in pressurized water reactor (PWR) coolant conditions in the ATR at the Idaho National Laboratory (INL). This paper reports the status of INL efforts to develop this testing capability. In addition to providing an overview of in-pile creep test capabilities available at other test reactors, this paper focuses on efforts to design and evaluate a prototype test rig in an autoclave at INL's High Temperature Test Laboratory (HTTL).

D. L. Knudson; J. L. Rempe

2012-02-01

396

Temperature, pressure, and concentration jumps for a binary mixture of vapors on a plane condensed phase: Numerical analysis of the linearized Boltzmann equation  

NASA Astrophysics Data System (ADS)

The half-space problem of the temperature, pressure, and concentration jumps for a binary mixture of vapors is investigated on the basis of the linearized Boltzmann equation for hard-sphere molecules with the complete condensation condition. First, the problem is shown to be reduced to three elemental ones: the problem of the jumps caused by the net evaporation or condensation, that caused by the gradient of temperature, and that caused by the gradient of concentration. Then, the latter two are investigated numerically in the present contribution because the first problem has already been studied [Yasuda, Takata, and Aoki, Phys. Fluids 17, 047105 (2005)]. The numerical method is a finite-difference one, in which the complicated collision integrals are computed by the extension of the method proposed by Sone, Ohwada, and Aoki [Phys. Fluids A 1, 363 (1989)] to the case of a gas mixture. As a result, the behavior of the mixture is clarified not only at the level of the macroscopic quantities but also at the level of the velocity distribution function. In addition, accurate formulas of the temperature, pressure, and concentration jumps are constructed for arbitrary values of the concentration of the background reference state by the use of the Chebyshev polynomial approximation. The solution of the corresponding problem of a vapor-gas mixture and that of the temperature-jump problem on a simple solid wall are also obtained as special cases of the present problem.

Takata, Shigeru; Aoki, Kazuo; Yasuda, Shugo; Kosuge, Shingo

2006-06-01