These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Description of Day-to-Day Variability in IRI  

NASA Astrophysics Data System (ADS)

The International Reference Ionosphere (IRI) describes the monthly average behavior of Earth's ionosphere based on most of the accessible and reliable ground and space observations of ionospheric parameters. IRI is doing an excellent job in accurately representing these average conditions as countless comparisons with additional data have shown and as acknowledged by the fact that international organizations (COSPAR, URSI, ISO, ECSS) have accepted IRI as their ionosphere standard. However, with our ever-increasing dependence on space technology it has become important to go beyond the monthly averages and to provide a description of the day-to-day variability of the ionosphere. We will review past and ongoing efforts to provide IRI users with a quantitative description of ionospheric variability depending on altitude, time of day, time of year, latitude and solar and magnetic activity. We will present new results from an analysis of ISIS and Alouette topside sounder data. The IRI team is also pursuing the development of an IRI Real-Time (IRI-RT) that uses assimilative algorithms or updating procedures to combine IRI with real-time data for a more accurate picture of current ionospheric conditions. We will review the status of these activities and report on latest results.

Bilitza, Dieter; Liu, Boding; Rodriguez, Joseph E.

2013-04-01

2

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008  

NASA Astrophysics Data System (ADS)

Ionospheric F2 peak electron densities (NmF2) measured at ten ionosonde stations have been analyzed to investigate ionospheric day-to-day variability around the Whole Heliosphere Interval (WHI) in 2008 (Day of Year (DOY) 50 - 140). The ionosonde data showed that there was significant global day-to-day variability in NmF2. This variability had 5-, 7-, 9-, 11-, 13.5-, and 16 - 21-day periodicities. At middle latitudes, the ionosphere appeared to respond directly to the solar-wind and interplanetary-magnetic-field (IMF) induced geomagnetic-activity forcing, with the day-to-day variability having the same periods as those in the solar-wind/IMF and geomagnetic activity. At the geomagnetic Equator, the ionosphere had a strong 7-day periodicity, corresponding to the same periodicity in the IMF B z component. In the equatorial anomaly region, the ionosphere showed more complicated day-to-day variability, dominated by the 9-day periodicity. In addition, there were also periodicities of 11 days and 16 - 21 days in the ionosonde data at some stations. The ionosonde data were compared with the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) simulations that were driven by the observed solar-wind and IMF data during the WHI. The CMIT simulations showed similar ionospheric daily variability seen in the data. They captured the positive and negative responses of the ionosphere at middle latitudes during the first corotating interaction region (CIR) event in the WHI. The response of the model to the second CIR event, however, was relatively weak.

Wang, Wenbin; Lei, Jiuhou; Burns, Alan G.; Qian, Liying; Solomon, Stanley C.; Wiltberger, Michael; Xu, Jiyao

2011-12-01

3

Day-to-day variability in cardiorespiratory responses to hypoxic cycle exercise.  

PubMed

Repeatedly performing exercise in hypoxia could elicit an independent training response and become an unintended co-intervention. The primary purposes of this study were to determine if hypoxic exercise responses changed across repeated testing and to assess the day-to-day variability of commonly used measures of cardiorespiratory and metabolic responses to hypoxic exercise. Healthy young males (aged 23 ± 2 years) with a maximal O2 consumption of 50.7 ± 4.7 mL·kg(-1)·min(-1) performed 5 trials (H1 to H5) over a 2-week period in hypoxia (fraction of inspired oxygen = 0.13). Participants completed 3-min stages at 20%, 40%, 60%, and 10% of individual peak power. With increasing cycle exercise intensity there were increases in minute ventilation, O2 consumption, CO2 production, respiratory exchange ratio, heart rate (HR), blood lactate concentration, and ratings of perceived exertion for legs and respiratory system along with a reduction in oxyhaemoglobin saturation (%SpO2) (all p < 0.001). There were no systematic changes from H1 to H5 (p > 0.05). Most measures were highly repeatable across testing sessions with the coefficient of variation (CV) averaging ?10% of the mean value in all variables except O2 consumption (17%), CO2 production (11%) and blood lactate concentration (17%). For HR and %SpO2 the CV was <5%. The exercise protocol did not elicit a training response when repeated 5 times during a 2-week period and the variability of exercise responses was low. We conclude that this protocol allows detection of small changes in cardiorespiratory responses to hypoxic exercise that might occur during exposure to hypoxia. PMID:25603431

MacNutt, Meaghan J; Peters, Carli M; Chan, Catherine; Moore, Jason; Shum, Serena; Sheel, A William

2015-02-01

4

Application of data assimilation in the Whole Atmosphere Community Climate Model to the study of day-to-day variability in the middle and upper atmosphere  

NASA Astrophysics Data System (ADS)

The Data Assimilation Research Testbed (DART) ensemble adjustment Kalman filter (EAKF) is employed to perform data assimilation in the Whole Atmosphere Community Climate Model (WACCM). To demonstrate the potential of the WACCM+DART for studying short-term variability in the mesosphere and lower thermosphere (MLT), results are presented based on the assimilation of synthetic observations that are sampled from a known model truth. We assimilate temperature and wind from radiosondes and aircraft, satellite drift winds, and COSMIC refractivity in the lower atmosphere, and SABER temperature observations in the middle/upper atmosphere. Relative to an unconstrained WACCM simulation, the assimilation of only lower atmosphere observations reduces the global root mean square error (RMSE) in zonal wind by up to 40% at MLT altitudes. Using data assimilation to constrain the lower atmosphere can therefore provide significant insight into MLT variability. The RMSE in the MLT is reduced by an additional 10-15% when SABER observations are also assimilated. The WACCM+DART is shown to be able to reproduce the large-scale features of the day-to-day variability in the zonal mean, migrating, and nonmigrating tides in the MLT. Though our simulation results are based on idealized conditions, they demonstrate that the WACCM+DART can reproduce the day-to-day variability in the MLT. Assimilation of real observations in the WACCM+DART will therefore enable significant insight into the real day-to-day dynamical variability from the surface to the lower thermosphere.

Pedatella, N. M.; Raeder, K.; Anderson, J. L.; Liu, H.-L.

2013-08-01

5

NPR: Day to Day  

NSDL National Science Digital Library

Hosted by award-winning National Public Radio (NPR) correspondent Alex Chadwick, Day to Day is a way for regular NPR listeners to listen to smart news coverage during the middle of the day or during their lunch-hour. Fortunately, Day to Day is available online, complete with an archive dating back to January 2003. Produced in the NPR West office in Los Angeles, and includes a number of NPR regulars and contributors from the online publication Slate. Day to Day also features the helpful daily reports from the Minnesota Public Radio show, Marketplace, which is "an informative conversation about business and economic news". Other regular features on Day to Day include commentaries on recent music releases from independent music critic Christian Bordal and curious and novel exposes and reports on the "odd underbelly" of the City of Angels, direct from Southern California.

6

Assessing Day-to Day Variability in the Vertical Distribution of Methane, Carbon Dioxide, and Ozone over Railroad Valley, NV  

NASA Astrophysics Data System (ADS)

In-situ observations of three trace gases over a remote desert site allow for an analysis of the variability of ozone (O3), methane (CH4), and carbon dioxide (CO2) in the free troposphere. Observations from June 2013 show almost no change from one day to the next in the boundary layer (BL) up to > 4 km (30% of the atmospheric column), while mixing ratios of methane and carbon dioxide show strong variability above this altitude. Ozone values also demonstrate variability above the boundary layer, and ozone day-to-day variability in the well-mixed BL is greater than that of CO2 or CH4. Results from week-long intensives in both June 2012 and June 2013, as well as monthly measurements over the period 2012-2013, will be compared to long-term vertical profile data sets at other locations (Trinidad Head, CA; Briggsdale, CO; and the Southern Great Plains site, OK). Variability above and in the boundary layer will be reported. To assess possible sources of variability, in situ data will be analyzed with a chemical trajectory model (GEOS-Chem v9-01-03). The North America nested-grid version of GEOS-Chem utilizes varying emission inventories and model parameterizations to simulate the emissions of greenhouse gases (CO2 and CH4, in this case) and ozone precursor gases. Tagged tracer simulations in GEOS-Chem allow for the geographical source apportionment of ozone, indicating whether the observed O3 was formed in the upper troposphere, middle troposphere, stratosphere, or any user-defined boundary layer location. For this study we will focus on ozone formed in the boundary layer over Asia, the Pacific Ocean, Mexico, Canada, and the United States. The importance of daily variability in the free tropospheric values of CO2, CH4, and O3 will be discussed in the context of column measurements collected from the surface or from space. Many data assimilation systems are designed to assume that changes to the total column average should be attributed primarily to changes within the boundary layer where large diurnal and seasonal cycles are presumed to dominate, but our data show that under some circumstances, this is not a valid presumption and can lead to a misinterpretation of the column measurement.

Iraci, L. T.; Johnson, M. S.; Yates, E. L.; Tanaka, T.; Sweeney, C.; Tadic, J.; Roby, M.; Andrews, A. E.; Lopez, J. P.

2013-12-01

7

Day to day with COPD  

MedlinePLUS

... but there are things you can do every day to keep COPD from getting worse, to protect ... COPD - day to day; Chronic obstructive airways disease - day to day; Chronic obstructive lung disease - day to day ; Chronic ...

8

On the day-to-day variation of the equatorial electrojet during quiet periods  

NASA Astrophysics Data System (ADS)

It has been known for a long time that the equatorial electrojet varies from day to day even when solar and geomagnetic activities are very low. The quiet time day-to-day variation is considered to be due to irregular variability of the neutral wind, but little is known about how variable winds drive the electrojet variability. We employ a numerical model introduced by Liu et al. (2013), which takes into account weather changes in the lower atmosphere and thus can reproduce ionospheric variability due to forcing from below. The simulation is run for May and June 2009. Constant solar and magnetospheric energy inputs are used so that day-to-day changes will arise only from lower atmospheric forcing. The simulated electrojet current shows day-to-day variability of ±25%, which produces day-to-day variations in ground level geomagnetic perturbations near the magnetic equator. The current system associated with the day-to-day variation of the equatorial electrojet is traced based on a covariance analysis. The current pattern reveals return flow at both sides of the electrojet, in agreement with those inferred from ground-based magnetometer data in previous studies. The day-to-day variation in the electrojet current is compared with those in the neutral wind at various altitudes, latitudes, and longitudes. It is found that the electrojet variability is dominated by the zonal wind at 100-120 km altitudes near the magnetic equator. These results suggest that the response of the zonal polarization electric field to variable zonal winds is the main source of the day-to-day variation of the equatorial electrojet during quiet periods.

Yamazaki, Y.; Richmond, A. D.; Maute, A.; Liu, H.-L.; Pedatella, N.; Sassi, F.

2014-08-01

9

Encapsulated radiophosphorescent standards for day-to-day photometer calibration.  

PubMed

Solid, unquenched, radiophosphorescent standards for use in the day-to-day calibration of bottom viewing photometers (luminometers) were prepared by encapsulating commercially-available phosphor powders that are excited to phosphoresce by the beta- decay of 63Ni (t0.5 = 96 yr) or 14C (t0.5 = 5730 yr). The radionuclides are physically adsorbed on the phosphors by precipitation either as a "basic nickel carbonate" or as barium carbonate. The radioactive phosphors are then deposited by centrifugation as a thin layer at the bottom of the vials or tubes that are normally used in the photometer. The phosphor layer is infiltrated with a plastic resin and embedded. A light absorbing layer is subsequently cast over the phosphor layer to prevent stray light excitation of phosphorescence. The encapsulated photometer standards have remained mechanically and photometrically stable since their fabrication, which in some cases is 3 years ago. An equivalent level of visible luminescence emitted from the standards of up to 2.3 x 10(10) photons.s-1 was achieved by using an appropriate amount of radioactivity and the proper phosphor. The phosphor used in the standards could be chosen such that the radiophosphorescence emission spectrum corresponded approximately to the chemiluminescence or bioluminescence spectrum under investigation. PMID:2089419

O'Kane, D J; Lee, J

1990-10-01

10

The day-to-day occurrence of equatorial plasma bubbles measured from Vanimo, Papua New Guinea  

NASA Astrophysics Data System (ADS)

An analysis of the occurrence of Equatorial Plasma Bubbles (EPBs) detected using a ground-based Global Positioning System (GPS) receiver located at Vanimo in South-east Asia will be presented. The 3-year (2000-2002) dataset employed shows that the EPB occurrence maximizes (minimizes) during the equinoxes (solstices), in good agreement with previous findings. The low-latitude ionosonde station at Vanimo is used in conjunction with the GPS receiver in an analysis of the day-to-day EPB occurrence variability during the equinox period. A superposed epoch analysis of the ionosonde data reveals that the height, and the change in height, of the F layer is 1 standard deviation (1?) larger on the days for which EPBs were detected, compared to non-EPB days. These results are interpreted using the generalized Rayleigh-Taylor (R-T) plasma instability growth rate, for which stronger upward drift of the lower-altitude F-layer plasma promotes faster growth of EPBs after sunset. These results are then compared to the results of the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM), which surprisingly show strong similarities to the observations, despite only using geomagnetic and solar activity inputs. The TIEGCM is also used to directly calculate the hourly flux-tube integrated R-T growth rate. A superposed epoch analysis reveals that the modeled R-T growth rate is a little less than 1? higher on average for EPB days compared to non-EPB days. The implication of this result is that the TIEGCM generates almost enough day-to-day variability in order to account for the day-to-day EPB occurrence observed during the equinox. This result isn't necessarily expected due to the model's limited altitude coverage of 100-700 km (depending on solar activity) and the lack of ionospheric observation inputs. It is thought that the remaining variability could originate from either lower altitudes (e.g. atmospheric gravity waves from the troposphere) or from higher altitudes (resulting from coupling with the magnetosphere and solar wind), or potentially both. It is concluded that the continuing advancement of numerical modeling of the thermosphere and ionosphere, coupled with altitudes above and below, is required to better understand the day-to-day EPB occurrence.

Carter, B. A.; Yizengaw, E.; Francis, M.; Terkildsen, M. B.; Marshall, R. A.; Norman, R.; Zhang, K.

2013-12-01

11

Exospheric temperature variability and the solar EUV control  

Microsoft Academic Search

Incoherent scatter radar experiments at Millstone Hill for a consecutive 30 days have been conducted in October 2002, enabling this study of the day-to-day thermospheric variability in exospheric temperature Tex. This day-to-day variability is seen as variations at fixed local times as well as those in the tidal decompositions. Solar EUV and magnetic activity influences as the main driving factors

S. Zhang; J. M. Holt; P. J. Erickson; T. N. Woods

2010-01-01

12

An Idiographic Examination of Day-to-Day Patterns of Substance Use Craving, Negative Affect, and Tobacco Use among Young Adults in Recovery  

ERIC Educational Resources Information Center

Psychological constructs, such as negative affect and substance use cravings that closely predict relapse, show substantial intraindividual day-to-day variability. This intraindividual variability of relevant psychological states combined with the "one day at a time" nature of sustained abstinence warrant a day-to-day investigation of substance…

Zheng, Yao; Wiebe, Richard P.; Cleveland, H. Harrington; Molenaar, Peter C. M.; Harris, Kitty S.

2013-01-01

13

Association Between Internalizing Disorders and Day-to-Day Activities of Low Energetic Expenditure.  

PubMed

The objective of this study is to compare energetic expenditure in day-to-day activities among subjects with internalizing disorders (depression and anxiety), externalizing disorders (attention deficit/hyperactivity disorder and oppositional defiant disorder) and healthy children and adolescents without any psychiatric diagnosis. One hundred and five (n = 105) students from a community sample were evaluated throughout a structured psychiatric interview and categorized into three groups: internalizing (n = 54), externalizing (n = 12) and typically developing controls (TDC, n = 39). Energetic expenditure was evaluated using 3-day physical activity record. Subjects with internalizing disorders performed activities with lower energetic expenditure as compared to those with externalizing disorders and TDC. Participants with externalizing disorders had more energetic expenditure variability. Our study suggests that internalizing disorders are associated with activities of low energetic expenditure in day-to-day activities, extending previous findings with physical exercise. These findings may further contribute to the understanding of the associated morbidity previously described in patients with internalizing disorders. PMID:24570170

Gosmann, Natan Pereira; Salum, Giovanni Abrahão; Schuch, Felipe; Silveira, Patrícia Pelufo; Bosa, Vera Lucia; Goldani, Marcelo Zubaran; Manfro, Gisele Gus

2015-02-01

14

Perception updating and day-to-day travel choice dynamics in trac networks with information provision  

E-print Network

Perception updating and day-to-day travel choice dynamics in trac networks with information is developed to capture the mechanism by which travelers update their travel time perceptions from one day, then selects an alternative based on the utility maximization princi- ple. The perception updating model

Peeta, Srinivas

15

The day-to-day monitoring of the 2011 severe drought in China  

NASA Astrophysics Data System (ADS)

Dry/wet condition has a large interannual variability. Decision-makers need to know the onset, duration, and intensity of drought, and require droughts be monitored at a daily to weekly scale. However, previous tools cannot monitor drought well at this short timescale. The Palmer Drought Severity Index has been found dissatisfactory in monitoring because of its complexity and numerous limitations. The Standardized Precipitation Index (SPI) always asks for a timescale, and precipitation is averaged over the period of the scale. Because of this, the SPI cannot be used for short scales, e.g., several days, and what it tells is the overall drought situation of the period. The weighted average of precipitation (WAP) developed by Lu (Geophys Res Lett 36:L12707, 2009) overcomes the deficiency of the SPI; it does not require a timescale, and can provide the drought (and flood) extent of each day. Therefore, the WAP can monitor drought at scales from daily to weekly, monthly, and any longer scale, and is really "flexible and versatile for all timescales". In this study, the standardized WAP (SWAP) is used to monitor the 2011 drought over China. Drought swept the country during the year from north to south and from east to west. In spring, a once-in-a-fifty-year drought occurred over the Yangtze River basin and the southern region, causing serious shortage of drinking water for people and livestock, as well as tremendous losses in agriculture and the shipping industry. Results show that the SWAP, with its monthly mean plots, can well reproduce the seasonal shift of the 2011 drought across the country. The animation of daily plots demonstrates that the SWAP would have been able to monitor the day-to-day variation of the spring drought around the Yangtze River basin. It can provide the details of the drought, such as when the drought emerged over the region, how long it maintained there (though drought area may move back and forth with extension and contraction of the area), and when the drought relieved over the basin.

Lu, Er; Cai, Wenyue; Jiang, Zhihong; Zhang, Qiang; Zhang, Cunjie; Higgins, R. Wayne; Halpert, Michael S.

2014-07-01

16

Curricular quality and day?to?day learning activities in pre?school  

Microsoft Academic Search

The purpose of this paper is to show how curricular quality is related to the day?to?day activities experienced by children and the pedagogical activities of staff, both coded through systematic target?child observations. Data were drawn from the Effective Provision of Pre?School Education (EPPE) and the Researching Effective Pedagogy in the Early Years (REPEY) studies. Curricular quality was measured by coding

Kathy Sylva; Brenda Taggart; Vasiliki Totsika; Rose Gilden; Daniel Bell

2007-01-01

17

Elite Kenyan Endurance Runners are Hydrated Day-To-Day with Ad Libitum Fluid Intake  

Microsoft Academic Search

FUDGE, B. W., C. EASTON, D. KINGSMORE, F. K. KIPLAMAI, V. O. ONYWERA, K. R. WESTERTERP, B. KAYSER, T. D. NOAKES, and Y. P. PITSILADIS. Elite Kenyan Endurance Runners are Hydrated Day-To-Day with Ad Libitum Fluid Intake. Med. Sci. Sports Exerc., Vol. 40, No. 6, pp. 000-000, 2008. Previous studies of elite Kenyan endurance runners reported that athletes did not

BARRY W. FUDGE; CHRIS EASTON; DAVID KINGSMORE; FESTUS K. KIPLAMAI; VINCENT O. ONYWERA; KLAAS R. WESTERTERP; BENGT KAYSER; TIMOTHY D. NOAKES; YANNIS P. PITSILADIS

2008-01-01

18

Day-to-day oversight of National Laboratory MC&A programs  

SciTech Connect

The US Department of Energy`s (DOE) orders require that its Los Alamos Area Office (LAAO) oversee the day-to-day activities of the Los Alamos National Laboratory (LANL). Making that oversight unobtrusive is important to keep it from creating additional burdens of reports and programs for the LANL. LAAO accomplishes day-to-day oversight of Material Control and Accountability (MC&A) at the LANL as an onsite observer of LANL`S in-house monitoring activities. Working guidelines established for the LAAO observer prevent us from hindering LANL`s program. A subset of MC&A activities that spans a wide range of MC&A programs with great sensitivity to functionality was selected for monitoring. Thus, timely ``finger on the pulse`` monitoring occurs without smothering the laboratory. LAAO and LANL Management negotiated implementation and observer guidance for the monitoring process. LAAO will apply the method used to other topical areas of the Safeguards and Security arena in the future.

Sedlacek, W.A. [Westinghouse Hanford Co., Richland, WA (United States); Flynn, A.B. [USDOE Los Alamos Area Office, NM (United States)

1995-06-01

19

Living from Day to Day – Qualitative Study on Borderline Personality Disorder in Adolescence  

PubMed Central

Objective: The purpose of this study was to assess how far identity and self-image disturbances are features of borderline personality disorder (BPD) in adolescence. Method: Face-to-face interviews were carried out with a total of 50 adolescents with BPD and 50 controls, with a median age of 16 (SD 1.1; range 13 to 18) years. Data was analysed using a qualitative methodology, interpretative phenomenological analysis (IPA). Thematic statements representative of adolescents’ lived experience were extracted from the interviews. Results: Four main themes representing the day-to-day experiences of adolescents with BPD were identified: emotional experiences characterised by the feelings of fear, sadness and pessimism; interpersonal relationships characterised by the feelings of solitude and hostility from others; a conformist self-image characterised by a feeling of normality and difficulty in projecting into time; and, a structuring of discourse characterised by discontinuity in the perception of experiences. Conclusion: This qualitative study suggests that the day-to-day experiences of adolescents with borderline personality disorder is centred on the experience of the present. Discontinuity in self-image, alongside marked dysphoric manifestations, leads to distress and hinders compliance with care. These issues are highly relevant in psychotherapy and could lead to more effective treatment of the disorder in adolescents. PMID:24223047

Spodenkiewicz, Michel; Speranza, Mario; Taïeb, Olivier; Pham-Scottez, Alexandra; Corcos, Maurice; Révah-Levy, Anne

2013-01-01

20

Day-to-day repeatability of the Pulse Time Index of Norm  

PubMed Central

The pulse wave velocity (PWV) threshold for hypertensive target organ damage is presently set at 10 meters per second. New 24-hour monitors (eg, BPLab® and Vasotens®) provide several PWV measurements over a period of 24–72 hours. A new parameter, ie, the Pulse Time Index of Norm (PTIN), can be calculated from these data. The PTIN is defined as the percentage of a 24-hour period during which the PWV does not exceed 10 meters per second. The aim of the present study was to test the new PTIN for clinical feasibility using day-to-day repeatability analysis. Oscillometrically generated waveform files (n=85), which were previously used for research studies, were reanalyzed using the new 2013 version software of the Vasotens technology program, which enables calculation of PTIN. The intraclass correlation coefficient was 0.98 and Cronbach’s alpha was 0.97, indicating that the PTIN has excellent day-to-day repeatability and internal consistency. The present results show adequate repeatability, and PTIN assessment using the Vasotens technology appears to be feasible. PMID:24600253

Posokhov, Igor N; Konradi, Aleksandra O; Shlyakhto, Eugeny V; Mamontov, Oleg V; Orlov, Artemy V; Rogoza, Anatoly N

2014-01-01

21

Day-to-day Variation of Equatorial Electrojet Controlled by Mid-latitude Sq Current System  

NASA Astrophysics Data System (ADS)

A dense network of geomagnetic field observations along the 210-degree magnetic meridian during 2000-2002 enabled us to determine daily values of (1) the total current intensity of the equivalent Sq current system Jtotal in kilo-amperes and (2) the distance between the northern and southern foci of the equivalent Sq current system dNS in degrees. It is found that the daily range of the north-south component of the geomagnetic field at Davao (a dip-equatorial station in Philippines) can be well described in this simple form: (Jtotal+76.379)(-0.007dNS+0.8217). The results suggest that day-to-day variation of equatorial electrojet is largely controlled by the intensity and shape of the mid-latitude Sq current system and local effects are often of secondary importance (under 20%).

Yamazaki, Y.; Yumoto, K.; Ikeda, A.; Abe, S.; Uozumi, T.; Magdas/Cpmn Group

2011-12-01

22

Day-to-Day Variation in Iron Status Indexes is Similar for Most Measures in Elderly Women With and Without Rheumatoid Arthritis  

Microsoft Academic Search

Objective To determine the day-to-day variation in biochemical measures of iron status in a group of elderly women with rheumatoid arthritis compared with a group of healthy elderly women.Design Venous blood samples were collected from each subject on 3 nonconsecutive days during a 2-week study period; subjects had fasted overnight. Variability in hemoglobin level, hematocrit value, serum iron concentration, total

CAROL J. LAMMI-KEEFE; ELAINE S. LICKTEIG; NAMANJEET AHLUWALIA; N. REBECCA HALEY

1996-01-01

23

Day to day treatment variations of accelerated partial breast brachytherapy using a multi-lumen balloon  

PubMed Central

Purpose To evaluate the variations of multi-lumen balloon (MLB)-based brachytherapy from simulation day to treatment day and their dosimetric impacts during accelerated partial breast irradiation (APBI). Material and methods A total of 42 CT images scanned from seven patients were evaluated with regards to daily variation due to of: 1) internal uncertainty: size and shape of balloon, seroma volume; 2) geometrical uncertainty-random: length of each catheter was measured for each fraction (total 70); 3) geometrical uncertainty-systematic: virtual systematic errors were tested by offsetting dwell positions. The original plans (as group A) had a mean value of 96.8% on V95 of the PTV_Eval. Plans were rerun (as group B) such that the mean value of the V95 was relaxed to 90.4%. By applying the reference plan to each daily CT image, variations of target coverage under different sources of error were evaluated. Results Shape and size of the balloon had means of < 1 mm decreased in diameter and < 0.4 cm3 decreased in volume; the mean seroma volume increased by 0.2 cm3. This internal variation has a mean of < 1% difference for both V90 and V95. The geometrical uncertainty made a mean deviation of 2.7 mm per root of sum of square. It caused the degradations of V90 and V95 by mean values of 1.0% and 1.2%, respectively. A systematic error of 3 mm and 4 mm would degrade both of V90 and V95 by 4% and 6%, respectively. The degradations on target coverage of the plans in group A were statistically the same as those in group B. Conclusions Overall, APBI treatments with MLB based brachytherapy are precise from day to day. However, minor variation due to daily treatment uncertainties can still degrade tumor bed coverage to an unacceptable coverage when V95 of the original plan is close to 90%. PMID:24790624

Mehta, Keyur J.; Hong, Linda; Yaparpalvi, Ravindra; Montgomery, Leslie L.; Bodner, William; Tomé, Wolfgang A.; Kalnicki, Shalom

2014-01-01

24

Evolution of the Variability of Surface Temperature and Vegetation Density in the Great Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

This study focuses on how the variability of land surface temperature and vegetation density at the SGP ARM-CART site changes over episodic (day to day) and seasonal time scales using AVHRR satellite data. Four drying periods throughout the year are analyzed. Land surface temperature had an errati...

25

INTRODUCTION Health care providers face many challenges in the day to day pursuit of  

E-print Network

with a complaint of fever, cough and shortness of breath. As you may know, she has a 30-pack year smoking history was a cold but by yesterday she had more chest congestion and a temperature of 101 Table 1: The One

Gilbert, Matthew

26

Day to Day  

ERIC Educational Resources Information Center

A clean, healthy and safe school provides students, faculty and staff with an environment conducive to learning and working. However, budget and staff reductions can lead to substandard cleaning practices and unsanitary conditions. Some school facility managers have been making the switch to a day-schedule to reduce security and energy costs, and…

Jurecki, Dennis

2006-01-01

27

Day-to-day variation in saliva cortisol--relation with sleep, stress and self-rated health.  

PubMed

The objective was to examine the day-to-day variation in cortisol among healthy individuals and its relation to the time of saliva sampling, work, stress and fatigue. During 4 consecutive weeks, 14 office workers provided saliva samples (at awakening, 15 min after awakening and at bedtime) and made diary ratings for each day. Results showed a variation in cortisol values between participants but also within individuals. After controlling for the individual differences, results showed that low cortisol levels in the morning were associated with sleepiness at awakening and anxiety, exhaustion, and poor health the day before. High evening levels of cortisol were associated with symptoms of stress and poor self-rated health. Further analysis of the cortisol awakening response (CAR) showed that all participants had a mixture of both a positive and negative responses. During mornings with a negative response participants stayed in bed for a longer time after the initial awakening, which might be a sign of snoozing, thus missing the awakening response. PMID:19596045

Dahlgren, Anna; Kecklund, Göran; Theorell, Töres; Akerstedt, Torbjörn

2009-10-01

28

Better or Worse: a Study of Day-to-Day Changes over Five Months of Rosen Method Bodywork Treatment for Chronic Low Back Pain  

PubMed Central

Background Fluctuations of good days and bad days—in physical symptoms and emotional states—are common for individuals with chronic illness. This pilot study examines these fluctuations during bodywork treatment. Purpose We analyzed changes in daily self-reports over a period of five months for five individuals who received weekly treatments of Rosen Method Bodywork (RMB), which uses touch and words to enhance body awareness of physical sensations and emotional states. Subjects and Design Five subjects (aged 31–56) who had chronic low back pain (CLBP) received 16 weekly treatments given by three experienced RMB practitioners. Measures Pre- and posttreatment assessments covered demographics, disability, and pain. Clients also completed daily bedtime assessments of pain, fatigue, emotional state, and sense of control during the entire treatment period. Results All clients reported reductions in pain and/or disability in post- compared to pretreatment. In spite of a high level of day-to-day variability in the daily assessments, there were significant reductions in pain and fatigue, and significant increases in positive emotional state and sense of control across the treatment period. In reaching this end, however, some clients had slow and steady improvements, some improved more rapidly, while others got worse before they got better. Conclusions The natural course of healing—with its inevitable fluctuations in symptoms—is part of a process leading to successful treatment outcomes. Rosen Method Bodywork may be especially helpful in developing and accepting both sensory and emotional body awareness changes that facilitate overall improvement. PMID:24000305

Fogel, Alan

2013-01-01

29

Day-to-Day Travel-Time Trends and Travel-Time Prediction from Loop-Detector Data  

Microsoft Academic Search

This paper presents an approach to estimate future travel times on a freeway using flow and occupancy data from single loop detectors and historical travel time information. The work uses linear regression with stepwise variable selection method and more advanced tree based methods. The analysis considers forecasts ranging from a few minutes into the future up to an hour ahead.

Jaimyoung Kwon; Benjamin Coifman; Peter Bickel

2000-01-01

30

Utilizing 3D-visualization to apply compulsory ALARA principles in nuclear power plant design and day-to-day operation  

SciTech Connect

The development of an advanced visualization and simulation tool to support both design as well as day-to-day operation is presented. This tool exploits cutting edge computer graphics, physics-based effects modeling, virtual reality, and gaming technologies to establish a system that can eventually be used for the administrative planning and training of plant operators and design engineers. (authors)

Sanders, R. L.; Lake, J. E. [Oak Ridge National Laboratory, Computational Sciences and Engineering Div., Mail Stop 6085, One Bethel Valley Road, Oak Ridge, TN 37831 (United States)

2006-07-01

31

Modelling day-to-day stem diameter variation and annual growth of balsam fir ( Abies balsamea (L.) Mill.) from daily climate  

Microsoft Academic Search

In the present context of global climate changes and the continuous development of forest management strategies based on the concept of sustainable use, it is important to develop a better understanding of the climatic factors controlling the growth of boreal forests. In this study, we report the results of a five-year field research within which day-to-day balsam fir (Abies balsamea

Louis Duchesne; Daniel Houle

2011-01-01

32

Vacuum Variable Medium Temperature Blackbody  

Microsoft Academic Search

This article describes the vacuum variable medium-temperature blackbody (VMTBB) constructed to serve as a highly stable reference\\u000a source with an aperture diameter of 20 mm in the temperature range from 150 °C to 430 °C under medium-vacuum conditions (10?3 Pa) and in a reduced background environment (liquid-nitrogen-cooled shroud). The VMTBB was realized for the calibration facility\\u000a at the PTB in the field of

S. P. Morozova; N. A. Parfentiev; B. E. Lisiansky; U. A. Melenevsky; B. Gutschwager; C. Monte; J. Hollandt

2010-01-01

33

Diagnostic Performance of Schistosoma Real-Time PCR in Urine Samples from Kenyan Children Infected with Schistosoma haematobium: Day-to-day Variation and Follow-up after Praziquantel Treatment  

PubMed Central

Background In an effort to enhance accuracy of diagnosis of Schistosoma haematobium, this study explores day-to-day variability and diagnostic performance of real-time PCR for detection and quantification of Schistosoma DNA compared to other diagnostic tools in an endemic area before and after treatment. Methodology Previously collected urine samples (N?=?390) from 114 preselected proven parasitological and/or clinical S. haematobium positive Kenyan schoolchildren were analyzed by a Schistosoma internal transcribed spacer-based real-time PCR after 14 years of storage. Pre-treatment day-to-day fluctuations of PCR and microscopy over three consecutive days were measured for 24 children using intra-class correlation coefficient. A combined ‘gold standard’ (PCR and/or microscopy positive) was used to measure sensitivity and negative predictive value (NPV) of several diagnostic tools at baseline, two and 18 months post-treatment with praziquantel. Principal Findings All 24 repeatedly tested children were PCR-positive over three days with little daily variation in median Ct-values, while 83.3% were found to be egg-positive for S. haematobium at day 1 and 75.0% at day 2 and 3 pre-treatment, signifying daily fluctuations in microscopy diagnosis. Of all 114 preselected schoolchildren, repeated microscopic measurements were required to detect 96.5% versus 100% of positive pre-treatment cases by single PCR. At two months post-treatment, microscopy and PCR detected 22.8% versus 69.3% positive children, respectively. Based on the ‘gold standard’, PCR showed high sensitivity (>92%) as compared to >31% sensitivity for microscopy, both pre- and post-treatment. Conclusions/Significance Detection and quantification of Schistosoma DNA in urine by real-time PCR was shown to be a powerful and specific diagnostic tool for detection of S. haematobium infections, with less day-to-day variation and higher sensitivity compared to microscopy. The superior performance of PCR before, and two and 18 months post-treatment provides a compelling argument for PCR as an accurate and reproducible tool for monitoring treatment efficacy. PMID:24743389

Vinkeles Melchers, Natalie V. S.; van Dam, Govert J.; Shaproski, David; Kahama, Anthony I.; Brienen, Eric A. T.; Vennervald, Birgitte J.; van Lieshout, Lisette

2014-01-01

34

Sea Surface Temperature Variability: Patterns  

E-print Network

Words ocean-atmosphere interaction, El Ni~no, Pacific Decadal Oscillation, Atlantic Multidecadal associated with the North Atlantic Oscillation, and a pan-Pacific mode known as the Pacific Decadal, patterns of SST variability may arise from intrinsic oceanic modes, notably the Atlantic Multidecadal

Hurrell, James

35

A Peltier-based variable temperature source  

NASA Astrophysics Data System (ADS)

In this paper we propose a simple and cost-effective variable temperature source based on the Peltier effect using a commercially purchased thermoelectric cooler. The proposed setup can be used to quickly establish relatively accurate dry temperature reference points, which are necessary for many temperature applications such as thermocouple calibration.

Molki, Arman; Roof Baba, Abdul

2014-11-01

36

Variable temperature semiconductor film deposition  

DOEpatents

A method of depositing a semiconductor material on a substrate is disclosed. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

Li, X.; Sheldon, P.

1998-01-27

37

Variable temperature semiconductor film deposition  

DOEpatents

A method of depositing a semiconductor material on a substrate. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

Li, Xiaonan (Golden, CO); Sheldon, Peter (Lakewood, CO)

1998-01-01

38

Variable temperature seat climate control system  

DOEpatents

A temperature climate control system comprises a variable temperature seat, at least one heat pump, at least one heat pump temperature sensor, and a controller. Each heat pump comprises a number of Peltier thermoelectric modules for temperature conditioning the air in a main heat exchanger and a main exchanger fan for passing the conditioned air from the main exchanger to the variable temperature seat. The Peltier modules and each main fan may be manually adjusted via a control switch or a control signal. Additionally, the temperature climate control system may comprise a number of additional temperature sensors to monitor the temperature of the ambient air surrounding the occupant as well as the temperature of the conditioned air directed to the occupant. The controller is configured to automatically regulate the operation of the Peltier modules and/or each main fan according to a temperature climate control logic designed both to maximize occupant comfort during normal operation, and minimize possible equipment damage, occupant discomfort, or occupant injury in the event of a heat pump malfunction.

Karunasiri, Tissa R. (Van Nuys, CA); Gallup, David F. (Pasadena, CA); Noles, David R. (Glendale, CA); Gregory, Christian T. (Alhambra, CA)

1997-05-06

39

Variability of the Martian thermospheric temperatures during the last 7 Martian Years  

NASA Astrophysics Data System (ADS)

The temperatures and densities in the Martian upper atmosphere have a significant influence over the different processes producing atmospheric escape. A good knowledge of the thermosphere and its variability is thus necessary in order to better understand and quantify the atmospheric loss to space and the evolution of the planet. Different global models have been used to study the seasonal and interannual variability of the Martian thermosphere, usually considering three solar scenarios (solar minimum, solar medium and solar maximum conditions) to take into account the solar cycle variability. However, the variability of the solar activity within the simulated period of time is not usually considered in these models. We have improved the description of the UV solar flux included on the General Circulation Model for Mars developed at the Laboratoire de Météorologie Dynamique (LMD-MGCM) in order to include its observed day-to-day variability. We have used the model to simulate the thermospheric variability during Martian Years 24 to 30, using realistic UV solar fluxes and dust opacities. The model predicts and interannual variability of the temperatures in the upper thermosphere that ranges from about 50 K during the aphelion to up to 150 K during perihelion. The seasonal variability of temperatures due to the eccentricity of the Martian orbit is modified by the variability of the solar flux within a given Martian year. The solar rotation cycle produces temperature oscillations of up to 30 K. We have also studied the response of the modeled thermosphere to the global dust storms in Martian Year 25 and Martian Year 28. The atmospheric dynamics are significantly modified by the global dust storms, which induces significant changes in the thermospheric temperatures. The response of the model to the presence of both global dust storms is in good agreement with previous modeling results (Medvedev et al., Journal of Geophysical Research, 2013). As expected, the simulated ionosphere is also sensitive to the variability of the solar activity. Acknowledgemnt: Francisco González-Galindo is funded by a CSIC JAE-Doc contract financed by the European Social Fund

Gonzalez-Galindo, Francisco; Lopez-Valverde, Miguel Angel; Millour, Ehouarn; Forget, François

2014-05-01

40

Sea surface temperature variability: patterns and mechanisms.  

PubMed

Patterns of sea surface temperature (SST) variability on interannual and longer timescales result from a combination of atmospheric and oceanic processes. These SST anomaly patterns may be due to intrinsic modes of atmospheric circulation variability that imprint themselves upon the SST field mainly via surface energy fluxes. Examples include SST fluctuations in the Southern Ocean associated with the Southern Annular Mode, a tripolar pattern of SST anomalies in the North Atlantic associated with the North Atlantic Oscillation, and a pan-Pacific mode known as the Pacific Decadal Oscillation (with additional contributions from oceanic processes). They may also result from coupled ocean-atmosphere interactions, such as the El Niño-Southern Oscillation phenomenon in the tropical Indo-Pacific, the tropical Atlantic Niño, and the cross-equatorial meridional modes in the tropical Pacific and Atlantic. Finally, patterns of SST variability may arise from intrinsic oceanic modes, notably the Atlantic Multidecadal Oscillation. PMID:21141660

Deser, Clara; Alexander, Michael A; Xie, Shang-Ping; Phillips, Adam S

2010-01-01

41

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

42

Contribution of solar radiation to decadal temperature variability over land  

PubMed Central

Global air temperature has become the primary metric for judging global climate change. The variability of global temperature on a decadal timescale is still poorly understood. This paper examines further one suggested hypothesis, that variations in solar radiation reaching the surface (Rs) have caused much of the observed decadal temperature variability. Because Rs only heats air during the day, its variability is plausibly related to the variability of diurnal temperature range (daily maximum temperature minus its minimum). We show that the variability of diurnal temperature range is consistent with the variability of Rs at timescales from monthly to decadal. This paper uses long comprehensive datasets for diurnal temperature range to establish what has been the contribution of Rs to decadal temperature variability. It shows that Rs over land globally peaked in the 1930s, substantially decreased from the 1940s to the 1970s, and changed little after that. Reduction of Rs caused a reduction of more than 0.2 °C in mean temperature during May to October from the 1940s through the 1970s, and a reduction of nearly 0.2 °C in mean air temperature during November to April from the 1960s through the 1970s. This cooling accounts in part for the near-constant temperature from the 1930s into the 1970s. Since then, neither the rapid increase in temperature from the 1970s through the 1990s nor the slowdown of warming in the early twenty-first century appear to be significantly related to changes of Rs. PMID:23980136

Wang, Kaicun; Dickinson, Robert E.

2013-01-01

43

Variable temperature electrochemical strain microscopy of Sm-doped ceria  

SciTech Connect

Variable temperature electrochemical strain microscopy has been used to study the electrochemical activity of Sm-doped ceria as a function of temperature and bias. The electrochemical strain microscopy hysteresis loops have been collected across the surface at different temperatures and the relative activity at different temperatures has been compared. The relaxation behavior of the signal at different temperatures has been also evaluated to relate kinetic process during bias induced electrochemical reactions with temperature and two different kinetic regimes have been identified. The strongly non-monotonic dependence of relaxation behavior on temperature is interpreted as evidence for water-mediated mechanisms.

Jesse, Stephen [ORNL; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Kalinin, Sergei V [ORNL; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Yang, Nan [ORNL; Doria, Sandra [ORNL; Tebano, Antonello [ORNL

2013-01-01

44

Interdiurnal temperature variability over the conterminous United States and Canada  

E-print Network

INTERDIURNAL TEMPERATURE VARIABILITY OVER THE CONTERMINOUS UNITED STATES AND CANADA A Thesis by PETER BRUCE RICE Submitted to the Office of Graduate Studies Texas ASM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1988 Major Subject: Meteorology INTERDIURNAL TEMPERATURE VARIABILITY OVER THE CONTERMINOUS UNITED STATES AND CANADA A Thesis by PETER BRUCE RICE Approved as to sty1e and content by: Dennis M. Drisco11 (Chair...

Rice, Peter Bruce

1988-01-01

45

On forced temperature changes, internal variability, and the AMO  

NASA Astrophysics Data System (ADS)

estimate the low-frequency internal variability of Northern Hemisphere (NH) mean temperature using observed temperature variations, which include both forced and internal variability components, and several alternative model simulations of the (natural + anthropogenic) forced component alone. We then generate an ensemble of alternative historical temperature histories based on the statistics of the estimated internal variability. Using this ensemble, we show, first, that recent NH mean temperatures fall within the range of expected multidecadal variability. Using the synthetic temperature histories, we also show that certain procedures used in past studies to estimate internal variability, and in particular, an internal multidecadal oscillation termed the "Atlantic Multidecadal Oscillation" or "AMO", fail to isolate the true internal variability when it is a priori known. Such procedures yield an AMO signal with an inflated amplitude and biased phase, attributing some of the recent NH mean temperature rise to the AMO. The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming. Claims of multidecadal "stadium wave" patterns of variation across multiple climate indices are also shown to likely be an artifact of this flawed procedure for isolating putative climate oscillations.

Mann, Michael E.; Steinman, Byron A.; Miller, Sonya K.

2014-05-01

46

Is obesity associated with lower body temperatures? Core temperature: a forgotten variable in energy balance  

E-print Network

Is obesity associated with lower body temperatures? Core temperature: a forgotten variable Northwestern University Comprehensive Center on Obesity, Chicago, IL 60611, USA Northwestern University in obesity, along with the associated adverse health consequences, has heightened interest in the fundamental

Linsenmeier, Robert

47

Variability of dayside electron temperature at Venus  

NASA Technical Reports Server (NTRS)

Langmuir probe measurements on Pioneer Venus Orbiter show that electron temperature (Te) profiles exhibit two distinct regions. The lower, but more extended region is in the main ionosphere where Te increases slowly with altitude. The other, less extended region is in the ionopause, where Te rise sharply with altitude. If horizontal magnetic fields and flux ropes in the ionosphere inhibit vertical thermal conductivity sufficiently, then the observed Te profile could be explained with EUV as the major heat source (Cravens et al., 1980). The rise in Te in the ionopause region has generally been attributed to solar wind heating (Brace and Kliore, 1991). We suggest that this sharp rise in Te is due primarily to the steep fall in electron density, Ne. If the heating rate is essentially unchanged and heat conduction is not of primary importance, then a steep rise in Te will maintain a constant electron cooling rate for a steeply falling Ne. We have observed large orbit to orbit variations in Te in the ionopause region which are found to be inversely related to changes in Ne. Variations in solar wind dynamic pressure do not seem to have a direct effect on Te, rather the effect is indirect coming through the sharp decrease in Ne.

Mahajan, K. K.; Ghosh, S.; Paul, R.; Hoegy, W. R.

1994-01-01

48

No increase in global temperature variability despite changing regional patterns.  

PubMed

Evidence from Greenland ice cores shows that year-to-year temperature variability was probably higher in some past cold periods, but there is considerable interest in determining whether global warming is increasing climate variability at present. This interest is motivated by an understanding that increased variability and resulting extreme weather conditions may be more difficult for society to adapt to than altered mean conditions. So far, however, in spite of suggestions of increased variability, there is considerable uncertainty as to whether it is occurring. Here we show that although fluctuations in annual temperature have indeed shown substantial geographical variation over the past few decades, the time-evolving standard deviation of globally averaged temperature anomalies has been stable. A feature of the changes has been a tendency for many regions of low variability to experience increases, which might contribute to the perception of increased climate volatility. The normalization of temperature anomalies creates the impression of larger relative overall increases, but our use of absolute values, which we argue is a more appropriate approach, reveals little change. Regionally, greater year-to-year changes recently occurred in much of North America and Europe. Many climate models predict that total variability will ultimately decrease under high greenhouse gas concentrations, possibly associated with reductions in sea-ice cover. Our findings contradict the view that a warming world will automatically be one of more overall climatic variation. PMID:23883935

Huntingford, Chris; Jones, Philip D; Livina, Valerie N; Lenton, Timothy M; Cox, Peter M

2013-08-15

49

Foliar respiration acclimation to temperature and temperature variable Q10 alter ecosystem carbon balance  

E-print Network

Foliar respiration acclimation to temperature and temperature variable Q10 alter ecosystem carbon Station, TX 77843-2135, USA Abstract The response of respiration to temperature in plants can described by a constant Q10 of respiration, and longer-term responses often include acclimation. Despite

Minnesota, University of

50

Causes of Greenland temperature variability over the past 4000 years  

NASA Astrophysics Data System (ADS)

A new Greenland temperature record reconstructed from argon and nitrogen isotopes in trapped air in GISP2 ice core provides high-resolution (< 20 years) and precise temperature estimates over the past 4000 years [Kobashi et al., 2011]. Owing to tight age-controls and abundant paleoclimatic information from the ice core, the record provides a rare opportunity to evaluate the late Holocene climate in a multi-decadal to millennial time scale. In our earlier study [Kobashi et al., Submitted], we found Greenland temperature deviated from North Hemispheric (NH) temperature trend negatively to solar variation over the past 800 years owing to changes in solar-induced atmospheric circulations such as North Atlantic Oscillation/Arctic Oscillation (NAO/AO) with an additional contribution from changes in Atlantic meridional overturning circulation (AMOC). To investigate causes of the Greenland temperature variability over the past 4000 years, we calculated high latitude (75°N) temperature change by a one-dimensional energy balance model with orbital, solar, volcanic, greenhouse gas forcings. The volcanic forcing was reconstructed from GISP2 sulphate record, which agreed sufficiently well with the volcanic forcing reconstruction for NH from multi ice cores [Gao et al., 2008] over the past 1500 years. The result exhibited a secular temperature decrease in northern high latitudes owing to decreasing annual mean insolation by 1.4% through orbital forcing. As the Greenland temperature deviates from North Hemispheric trend negatively by solar variation, we added negative solar signal on the calculated high latitude temperature to infer Greenland temperature, mimicking solar induced NAO/AO and AMOC change of the past 800 years. The calculated Greenland temperature agrees with the ice core derived Greenland temperature with a correlation coefficient of r = 0.3 in a 95 % confidence level, indicating that the past variability of solar activity, volcanic eruptions, greenhouse gasses, and orbital changes can explain at least 9% of multi-decadal to millennial Greenland temperature variability over the past 4000 years. Considering expected large internal variability of regional climate, it is rather remarkable. A millennial cooling around 500 B.C.E. to 0 C.E. observed in Greenland temperature reconstruction from borehole temperature profiles [Dahl-Jensen et al., 1998] were also found in the calculated temperatures, indicating the cooling was caused by several volcanic eruptions and negative responses of Greenland temperature to solar variability. Dahl-Jensen, D., K. Mosegaard, N. Gundestrup, G. D. Clow, S. J. Johnsen, A. W. Hansen, and N. Balling (1998), Past temperatures directly from the Greenland Ice Sheet, Science, 282(5387), 268-271. Gao, C., A. Robock, and C. Ammann (2008), Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models, J. Geophys. Res. - Atmos., 113, D23111. Kobashi, T., D. T. Shindell, K. Kodera, J. E. Box, T. Nakaegawa, and K. Kawamura (Submitted), On the origin of Greenland temperature anomalies over the past 800 years, J. Geophys. Res. Kobashi, T., K. Kawamura, J. P. Severinghaus, J.-M. Barnola, T. Nakaegawa, B. M. Vinther, S. J. Johnsen, and J. E. Box (2011), High variability of Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core, Geophys. Res. Lett., 38(L21501).

Kobashi, T.; Kawamura, K.; Azuma, K. G.; Box, J. E.; Gao, C.; Nakaegawa, T.

2012-12-01

51

Variability in Measured Space Temperatures in 60 Homes  

SciTech Connect

This report discusses the observed variability in indoor space temperature in a set of 60 homes located in Florida, New York, Oregon, and Washington. Temperature data were collected at 15-minute intervals for an entire year, including living room, master bedroom, and outdoor air temperature (Arena, et. al). The data were examined to establish the average living room temperature for the set of homes for the heating and cooling seasons, the variability of living room temperature depending on climate, and the variability of indoor space temperature within the homes. The accuracy of software-based energy analysis depends on the accuracy of input values. Thermostat set point is one of the most influential inputs for building energy simulation. Several industry standards exist that recommend differing default thermostat settings for heating and cooling seasons. These standards were compared to the values calculated for this analysis. The data examined for this report show that there is a definite difference between the climates and that the data do not agree well with any particular standard.

Roberts, D.; Lay, K.

2013-03-01

52

Variability in Temperature-Related Mortality Projections under Climate Change  

PubMed Central

Background: Most studies that have assessed impacts on mortality of future temperature increases have relied on a small number of simulations and have not addressed the variability and sources of uncertainty in their mortality projections. Objectives: We assessed the variability of temperature projections and dependent future mortality distributions, using a large panel of temperature simulations based on different climate models and emission scenarios. Methods: We used historical data from 1990 through 2007 for Montreal, Quebec, Canada, and Poisson regression models to estimate relative risks (RR) for daily nonaccidental mortality in association with three different daily temperature metrics (mean, minimum, and maximum temperature) during June through August. To estimate future numbers of deaths attributable to ambient temperatures and the uncertainty of the estimates, we used 32 different simulations of daily temperatures for June–August 2020–2037 derived from three global climate models (GCMs) and a Canadian regional climate model with three sets of RRs (one based on the observed historical data, and two on bootstrap samples that generated the 95% CI of the attributable number (AN) of deaths). We then used analysis of covariance to evaluate the influence of the simulation, the projected year, and the sets of RRs used to derive the attributable numbers of deaths. Results: We found that < 1% of the variability in the distributions of simulated temperature for June–August of 2020–2037 was explained by differences among the simulations. Estimated ANs for 2020–2037 ranged from 34 to 174 per summer (i.e., June–August). Most of the variability in mortality projections (38%) was related to the temperature–mortality RR used to estimate the ANs. Conclusions: The choice of the RR estimate for the association between temperature and mortality may be important to reduce uncertainty in mortality projections. Citation: Benmarhnia T, Sottile MF, Plante C, Brand A, Casati B, Fournier M, Smargiassi A. 2014. Variability in temperature-related mortality projections under climate change. Environ Health Perspect 122:1293–1298;?http://dx.doi.org/10.1289/ehp.1306954 PMID:25036003

Benmarhnia, Tarik; Sottile, Marie-France; Plante, Céline; Brand, Allan; Casati, Barbara; Fournier, Michel

2014-01-01

53

Joint variability of global runoff and global sea surface temperatures  

USGS Publications Warehouse

Global land surface runoff and sea surface temperatures (SST) are analyzed to identify the primary modes of variability of these hydroclimatic data for the period 1905-2002. A monthly water-balance model first is used with global monthly temperature and precipitation data to compute time series of annual gridded runoff for the analysis period. The annual runoff time series data are combined with gridded annual sea surface temperature data, and the combined dataset is subjected to a principal components analysis (PCA) to identify the primary modes of variability. The first three components from the PCA explain 29% of the total variability in the combined runoff/SST dataset. The first component explains 15% of the total variance and primarily represents long-term trends in the data. The long-term trends in SSTs are evident as warming in all of the oceans. The associated long-term trends in runoff suggest increasing flows for parts of North America, South America, Eurasia, and Australia; decreasing runoff is most notable in western Africa. The second principal component explains 9% of the total variance and reflects variability of the El Ni??o-Southern Oscillation (ENSO) and its associated influence on global annual runoff patterns. The third component explains 5% of the total variance and indicates a response of global annual runoff to variability in North Aflantic SSTs. The association between runoff and North Atlantic SSTs may explain an apparent steplike change in runoff that occurred around 1970 for a number of continental regions.

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

2008-01-01

54

Spatial and temporal variability of extreme Temperature in Northeastern Spain  

NASA Astrophysics Data System (ADS)

Climate impact studies are more profoundly associated with changes in intensity and frequency of extreme events rather than changes in mean values. Long-term changes and spatial variability of extreme temperature were investigated in Northeastern Spain based on a daily dataset of 128 quality controlled and homogenized series spanning the period from 1960 to 2006. Extreme temperature was defined in terms of 20 indices recommended by the World Meteorological Organization. These indices included, for example, cold nights (TN10), warm nights (TN90), cold days (TX10), total number of frost days, intra-annual extreme temperature range and Diurnal temperature range. The magnitude of the trends and their statistical significance were determined using the nonparametric Kendal? tau test at the 95% level of significance. A clear positive trend was exhibited across the region for summer days (SU25), warm days (TX90), and tropical nights (TR20). This closely matches the general observed warming trend of daily maximum temperature. Conversely, a negative trend was marked for ice days, cold days, cold nights and the Diurnal temperature range. Key words: temperature extremes, daily temperature, climate variability, trend analysis, Spain.

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

2010-09-01

55

Temperature Fluctuations as a Source of Brown Dwarf Variability  

E-print Network

A number of brown dwarfs are now known to be variable with observed amplitudes as large as 10-30% at some wavelengths. While spatial inhomogeneities in cloud coverage and thickness are likely responsible for much of the observed variability, it is possible that some of the variations arise from atmospheric temperature fluctuations instead of, or in addition to, clouds. To better understand the role that thermal variability might play we present a case study of brown dwarf variability using a newly-developed one-dimensional, time-stepping model of atmospheric thermal structure. We focus on the effects of thermal perturbations, intentionally simplifying the problem through omission of clouds and atmospheric circulation. Model results demonstrate that thermal perturbations occurring deep in the atmosphere (at pressures greater than 10 bar) of a model T-dwarf can be communicated to the upper atmosphere through radiative heating via the windows in near-infrared water opacity. The response time depends on where in ...

Robinson, Tyler D

2014-01-01

56

Variability of Battery Wear in Light Duty Plug-In Electric Vehicles Subject to Ambient Temperature, Battery Size, and Consumer Usage: Preprint  

SciTech Connect

Battery wear in plug-in electric vehicles (PEVs) is a complex function of ambient temperature, battery size, and disparate usage. Simulations capturing varying ambient temperature profiles, battery sizes, and driving patterns are of great value to battery and vehicle manufacturers. A predictive battery wear model developed by the National Renewable Energy Laboratory captures the effects of multiple cycling and storage conditions in a representative lithium chemistry. The sensitivity of battery wear rates to ambient conditions, maximum allowable depth-of-discharge, and vehicle miles travelled is explored for two midsize vehicles: a battery electric vehicle (BEV) with a nominal range of 75 mi (121 km) and a plug-in hybrid electric vehicle (PHEV) with a nominal charge-depleting range of 40 mi (64 km). Driving distance distributions represent the variability of vehicle use, both vehicle-to-vehicle and day-to-day. Battery wear over an 8-year period was dominated by ambient conditions for the BEV with capacity fade ranging from 19% to 32% while the PHEV was most sensitive to maximum allowable depth-of-discharge with capacity fade ranging from 16% to 24%. The BEV and PHEV were comparable in terms of petroleum displacement potential after 8 years of service, due to the BEV?s limited utility for accomplishing long trips.

Wood, E.; Neubauer, J.; Brooker, A. D.; Gonder, J.; Smith, K. A.

2012-08-01

57

Analysis and interpretation of variabilities in ozone and temperature fields  

NASA Technical Reports Server (NTRS)

The temporal and spatial variabilities were studied of short and long term fluctuations in stratospheric ozone and temperature at various pressure levels using several years of ozone, temperature, and solar flux data from Nimbus 4, Nimbus 7, and SME satellites. Some results are as follows: (1) the solar UV flux and various indices of solar activity indicate a strong period at about 5 months; (2) satellite total ozone observations were analyzed using 17 years of data from the Nimbus 4 BUV and the Nimbus 7 SBUV experiments, which show very similar seasonal variations and quasibiennial oscillation (QBO) with some indication of a 4 year component; and (3) the zonal characteristics of both the ozone and temperature trends were derived from ten years of total ozone and 50 mb temperature based on the Nimbus 7 TOMS measurements and the NMC analyses respectively.

Chandra, S.

1990-01-01

58

Monofractal nature of air temperature signals reveals their climate variability  

E-print Network

We use the discrete "wavelet transform microscope" to show that the surface air temperature signals of weather stations selected in Europe are monofractal. This study reveals that the information obtained in this way are richer than previous works studying long range correlations in meteorological stations. The approach presented here allows to bind the H\\"older exponents with the climate variability. We also establish that such a link does not exist with methods previously carried out.

Deliège, Adrien

2014-01-01

59

Variable-temperature electron spin resonance of turquoise  

Microsoft Academic Search

The ESR spectra of several turquoise specimens contained an anisotropic component which was due to Cu2+ and an isotropic component arising from Fes+ ions. The Fe\\/Cu concentra- tion ratio obtained from these measurements agreed with ratios obtained analytically. A variable-temperature study from 77 K to 560 K indicated that the cupric ions are para- magnetic while the ferric ions behave

O. Cr-eRr; A. FnnacH

60

Adapting to the Day to Day Growth of TMR  

PubMed Central

Data capacity requirements vary widely as user groups vary in their use of and dependence on a computerized medical record. The development of TMR has fortunately been able to satisfy growth demands by adapting either application programs or system programs to remove growth restrictions as they are identified. This paper describes that evolution.

Hammond, William E.; Stead, William W.; Straube, Mark J.; Hammond, William E.

1983-01-01

61

Historical Temperature Variability Affects Coral Response to Heat Stress  

PubMed Central

Coral bleaching is the breakdown of symbiosis between coral animal hosts and their dinoflagellate algae symbionts in response to environmental stress. On large spatial scales, heat stress is the most common factor causing bleaching, which is predicted to increase in frequency and severity as the climate warms. There is evidence that the temperature threshold at which bleaching occurs varies with local environmental conditions and background climate conditions. We investigated the influence of past temperature variability on coral susceptibility to bleaching, using the natural gradient in peak temperature variability in the Gilbert Islands, Republic of Kiribati. The spatial pattern in skeletal growth rates and partial mortality scars found in massive Porites sp. across the central and northern islands suggests that corals subject to larger year-to-year fluctuations in maximum ocean temperature were more resistant to a 2004 warm-water event. In addition, a subsequent 2009 warm event had a disproportionately larger impact on those corals from the island with lower historical heat stress, as indicated by lower concentrations of triacylglycerol, a lipid utilized for energy, as well as thinner tissue in those corals. This study indicates that coral reefs in locations with more frequent warm events may be more resilient to future warming, and protection measures may be more effective in these regions. PMID:22479626

Carilli, Jessica; Donner, Simon D.; Hartmann, Aaron C.

2012-01-01

62

Intraseasonal sea surface temperature variability in Indonesian seas  

NASA Astrophysics Data System (ADS)

The satellite-derived sea surface temperature (SST) data, 1998-mid 2012, are used to examine intraseasonal variability (ISV; 20-90 days) across the Indonesian seas. The most energetic ISV is observed in the Banda Sea and across the Indo-Australia basin with an The satellite-derived sea surface temperature (SST) data, 1998-mid 2012, are used to examine intraseasonal variability (ISV; 20-90 days) across the Indonesian seas. The most energetic ISV is observed in the Banda Sea and across the Indo-Australia basin with an average SST standard deviation (STD) between 0.4-0.5°C, with strongest signature during boreal winter. What physical processes force the SST ISV variability within the Indonesian seas? Ocean process, sea-air interaction, or both? To help identify the main forcing, the satellite derived outgoing longwave radiation (OLR) and wind stress data in the region are examined. The OLR shows robust intraseasonal variations and is significantly correlated with the SST, particularly for variability with periods of 30-60 days, with OLR accounting for ~60-70% of the SST variance. The OLR is also maximum during boreal winter. Conversely, the surface wind may play insignificant role in perturbing the SST at intraseasonal timescales as shown by weak correlation between wind stress and SST. We thus suspect that the surface solar flux (suggested by the OLR) is likely more dominant than the surface turbulent heat flux (indicated by the surface wind) as the main source for the ISV in the SST in Indonesian seas. Furthermore the maximum OLR phase, coupled with a period of minimum mixed layer depth, may explain the strong SST variation during boreal winter in Indonesian seas. The influence of the Madden-Julian Oscillation (MJO) on the OLR and SST variability is currently being evaluated.

Napitu, A. M.; Gordon, A. L.; Yuan, X.

2012-12-01

63

Trends and variability in East African rainfall and temperature observations  

NASA Astrophysics Data System (ADS)

The economy of East Africa is highly dependent on agriculture, leading to a strong vulnerability of local society to fluctuations in seasonal rainfall amounts, including extreme events. Hence, the knowledge about the evolution of seasonal rainfall under future climate conditions is crucial. Rainfall regimes over East Africa are influenced by multiple factors, including two monsoon systems, several convergence zones and the Rift Valley lakes. In addition, local conditions, like topography, modulate the large-scale rainfall pattern. East African rainfall variability is also influenced by various teleconnections like the Indian Ocean Zonal Mode and El Niño Southern Oscillation. Regarding future climate projections, regional and global climate models partly disagree on the increase or decrease of East African rainfall. The specific aim of the present study is the acquirement of historic data from weather stations in East Africa (Kenya, Tanzania, Ruanda and Uganda), the use of gridded satellite (rainfall) products (ARC2 and TRMM), and three-dimensional atmospheric reanalysis (e.g., ERA-Interim) to quantify climate variability in the recent past and to understand its causes. Climate variability and trends, including changes in extreme events, are evaluated using ETCCDI climate change and standardized precipitation indices. These climate indices are determined in order to investigate the variability of temperature and rainfall and their trends with the focus on most recent decades. In the follow-up, statistical and dynamical analyses are conducted to quantify the local impact of pertinent large-scale modes of climate variability (Indian Ocean Zonal Mode, El Niño Southern Oscillation, Sea Surface Temperature of the Indian Ocean).

Seregina, Larisa; Ermert, Volker; Fink, Andreas H.; Pinto, Joaquim G.

2014-05-01

64

Geoeffective solar variability influence on Northern Hemisphere surface temperature  

NASA Astrophysics Data System (ADS)

The complex interaction of the solar outputs such as electromagnetic radiation, solar wind and interplanetary magnetic field with terrestrial environment would affect the Earth's climate. Usually, the effect of solar variability on climate is taken into account only through changes in solar total and spectral irradiance. In this study, possible climatic effects related to geoeffective solar variability were investigated by means of long-term statistical correlations between surface air temperature and solar/geomagnetic indices. The data from NCEP/NCAR reanalysis database for the Northern Hemisphere have been processed. Spectral analysis indicates the occurrence of periodicities between 2 and 7 years, associated to atmospheric phenomena, and periodicities around 11 and 22 years, normally associated to solar variability. By applying simple filtering procedures we can get the 11 and 22-year signals in our temperature data. Various features of these signals will be discussed on different spatial scales of the Northern hemisphere. The differences between observed and reanalysed data will be also discussed.

Dobrica, Venera; Suteanu, Cristian; Stefan, Cristiana; Pirloaga, Razvan; Demetrescu, Crisan

2014-05-01

65

Global climate models’ bias in surface temperature trends and variability  

NASA Astrophysics Data System (ADS)

The Earth has warmed in the last century with the most rapid warming occurring near the surface in the Arctic. This Arctic amplification occurs partly because the extra heat is trapped in a thin layer of air near the surface due to the persistent stable-stratification found in this region. The amount of warming depends upon the extent of turbulent mixing in the atmosphere, which is described by the depth of the atmospheric boundary layer (ABL). Global climate models (GCMs) tend to over-estimate the depth of stably-stratified ABLs, and here we show that GCM biases in the ABL depth are strongly correlated with biases in the surface temperature variability. This highlights the need for a better description of the stably-stratified ABL in GCMs in order to constrain the current uncertainty in climate variability and projections of climate change in the surface layer.

Davy, Richard; Esau, Igor

2014-11-01

66

Variability of surface temperature in agricultural fields of central California  

NASA Technical Reports Server (NTRS)

In an attempt to evaluate the relationship between hand-held infrared thermometers and aircraft thermal scanners in near-level terrain and to quantify the variability of surface temperatures within individual fields, ground-based and aircraft thermal sensor measurements were made along a 50-km transect on 3 May 1979 and a 20-km transect on 7 August 1980. These comparisons were made on fields near Davis, California. Agreement was within 1 C for fields covered with vegetation and 3.6 C for bare, dry fields. The variability within fields was larger for bare, dry fields than for vegetatively covered fields. In 1980, with improvements in the collection of ground truth data, the agreement was within 1 C for a variety of fields.

Hatfield, J. L.; Millard, J. P.; Goettelman, R. C.

1982-01-01

67

Anisotropic high temperature superconductors as variable resistors and switches  

SciTech Connect

Several anisotropic high temperature superconductors show critical current densities which are strongly dependent on the direction of an applied external magnetic field. The resistance of a sample can change by several orders of magnitude by applying a magnetic field. The potential for using the field dependent variable resistor or switch for applications in power systems is evaluated. Test results with small samples are presented. The requirements for large scale applications are outlined. The magnetic field triggering requirement, the frequency response of the device, use in 60 Hz ac circuits and heat transfer consideration are investigated. Several application examples are discussed. Use of variable resistor as a fault current limiter, as a switching element in rectifier circuitry and as an improved dump resistor for a superconducting magnet is presented.

Boenig, H.J.; Daugherty, M.A.; Fleshler, S.; Maley, M.P.; Mueller, F.M.; Prenger, F.C.; Coulter, J.Y.

1994-12-01

68

Electrical measurements of AC losses in high temperature superconducting coils at variable temperatures  

NASA Astrophysics Data System (ADS)

Measurements of AC losses in high temperature superconducting (HTS) coils wound from two different types of YBa2Cu3O7 (YBCO) coated conductors are reported. AC loss measurements by different arrangements of voltage loops and pick-up coils were investigated to propose accurate and convenient techniques to measure the AC losses in HTS coils, especially for large coils with the measurement signals significantly higher than the input range of typical lock-in amplifiers. A new and simple sub-cooling technique with an open liquid nitrogen bath was developed to measure AC losses in the sample coils at variable temperatures between 65 and 77 K. The temperature dependence of the losses in these coils was qualitatively explained based on the data on transport and magnetization AC losses in isolated tapes at variable temperatures.

Nguyen, D. N.; Kim, C. H.; Kim, J. H.; Pamidi, S.; Ashworth, S. P.

2013-09-01

69

Variability of Winter Air Temperature in Mid-Latitude Europe  

NASA Technical Reports Server (NTRS)

The aim of this paper is to report extreme winter/early-spring air temperature (hereinafter temperature) anomalies in mid-latitude Europe, and to discuss the underlying forcing to these interannual fluctuations. Warm advection from the North Atlantic in late winter controls the surface-air temperature, as indicated by the substantial correlation between the speed of the surface southwesterlies over the eastern North Atlantic (quantified by a specific Index Ina) and the 2-meter level air temperatures (hereinafter Ts) over Europe, 45-60 deg N, in winter. In mid-March and subsequently, the correlation drops drastically (quite often it is negative). This change in the relationship between Ts and Ina marks a transition in the control of the surface-air temperature: absorption of insolation replaces the warm advection as the dominant control. This forcing by maritime-air advection in winter was demonstrated in a previous publication, and is re-examined here in conjunction with extreme fluctuations of temperatures in Europe. We analyze here the interannual variability at its extreme by comparing warm-winter/early-spring of 1989/90 with the opposite scenario in 1995/96. For these two December-to-March periods the differences in the monthly mean temperature in Warsaw and Torun, Poland, range above 10 C. Short-term (shorter than a month) fluctuations of the temperature are likewise very strong. We conduct pentad-by-pentad analysis of the surface-maximum air temperature (hereinafter Tmax), in a selected location, examining the dependence on Ina. The increased cloudiness and higher amounts of total precipitable water, corollary effects to the warm low-level advection. in the 1989/90 winter, enhance the positive temperature anomalies. The analysis of the ocean surface winds is based on the Special Sensor Microwave/Imager (SSM/I) dataset; ascent rates, and over land wind data are from the European Centre for Medium-Range Weather Forecasts (ECMWF); maps of 2-m temperature, cloud cover and precipitable water are from the National Centers for Environmental Prediction (NCEP) Reanalysis.

Otterman, J.; Ardizzone, J.; Atlas, R.; Bungato, D.; Cierniewski, J.; Jusem, J. C.; Przybylak, R.; Schubert, S.; Starr, D.; Walczewski, J.

2002-01-01

70

Complexation of Plutonium (IV) With Sulfate At Variable Temperatures  

SciTech Connect

The complexation of plutonium(IV) with sulfate at variable temperatures has been investigated by solvent extraction method. A NaBrO{sub 3} solution was used as holding oxidant to maintain the plutonium(IV) oxidation state throughout the experiments. The distribution ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of sulfate were increased. Stability constants of the 1:1 and 1:2 Pu(IV)-HSO{sub 4}{sup -} complexes, dominant in the aqueous phase, were calculated from the effect of [HSO{sub 4}{sup -}] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures using the Van't Hoff equation.

Y. Xia; J.I. Friese; D.A> Moore; P.P. Bachelor; L. Rao

2006-10-05

71

Linking global climate and temperature variability to widespread amphibian declines putatively caused  

E-print Network

Linking global climate and temperature variability to widespread amphibian declines putatively that the proposed link be- tween climate change and widespread amphibian declines, puta- tively caused widespread amphibian losses in genus Atelopus via increased regional temperature variability, which can

Rohr, Jason

72

Adaptation of malate dehydrogenase to environmental temperature variability in two populations of Potentilla glandulosa Lindl  

Microsoft Academic Search

The responses of the kinetic properties of malate dehydrogenase to environmental temperature variability were compared for two populations of Potentilla glandulosa (Rosaceae). The two populations are native to regions of contrasting climates, with the inland population experiencing a high level of temperature variability during growth and the coastal populaton a low level of temperature variability. The substrate binding ability, as

J. A. Terri; M. M. Peet

1978-01-01

73

Temperature variability and childhood pneumonia: an ecological study  

PubMed Central

Background Few data on the relationship between temperature variability and childhood pneumonia are available. This study attempted to fill this knowledge gap. Methods A quasi-Poisson generalized linear regression model combined with a distributed lag non-linear model was used to quantify the impacts of diurnal temperature range (DTR) and temperature change between two neighbouring days (TCN) on emergency department visits (EDVs) for childhood pneumonia in Brisbane, from 2001 to 2010, after controlling for possible confounders. Results An adverse impact of TCN on EDVs for childhood pneumonia was observed, and the magnitude of this impact increased from the first five years (2001–2005) to the second five years (2006–2010). Children aged 5–14 years, female children and Indigenous children were particularly vulnerable to TCN impact. However, there was no significant association between DTR and EDVs for childhood pneumonia. Conclusions As climate change progresses, the days with unstable weather pattern are likely to increase. Parents and caregivers of children should be aware of the high risk of pneumonia posed by big TCN and take precautionary measures to protect children, especially those with a history of respiratory diseases, from climate impacts. PMID:24916742

2014-01-01

74

Variable temperature thin film indentation with a flat punch  

NASA Astrophysics Data System (ADS)

We present modifications to conventional nanoindentation that realize variable temperature, flat punch indentation of ultrathin films. The technique provides generation of large strain, thin film extrusion of precise geometries that idealize the essential flows of nanoimprint lithography, and approximate constant area squeeze flow rheometry performed on thin, macroscopic soft matter samples. Punch radii as small as 185nm have been realized in ten-to-one confinement ratio testing of 36nm thick polymer films controllably squeezed in the melt state to a gap width of a few nanometers. Self-consistent, compressive stress versus strain measurements of a wide variety of mechanical testing conditions are provided by using a single die-sample system with temperatures ranging from 20to125°C and loading rates spanning two decades. Low roughness, well aligned flat punch dies with large contact areas provide precise detection of soft surfaces with standard nanoindenter stiffness sensitivity. Independent heating and thermometry with heaters and thermocouples attached to the die and sample allow introduction of a novel directional heat flux measurement method to ensure isothermal contact conditions. This is a crucial requirement for interpreting the mechanical response in temperature sensitive soft matter systems. Instrumented imprint is a new nanomechanics material testing platform that enables measurements of polymer and soft matter properties during large strains in confined, thin film geometries and extends materials testing capabilities of nanoindentation into low modulus, low strength glassy, and viscoelastic materials.

Cross, Graham L. W.; O; ²Connell, Barry S.; Pethica, John B.; Rowland, Harry; King, William P.

2008-01-01

75

High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Astrophysics Data System (ADS)

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140° C while the heat losses caused by the addition of the VCHP are 1.8 W.

Tarau, Calin; Walker, Kara L.; Anderson, William G.

2009-03-01

76

Soil Temperature Variability in Complex Terrain measured using Distributed a Fiber-Optic Distributed Temperature Sensing  

NASA Astrophysics Data System (ADS)

Soil temperature (Ts) exerts critical environmental controls on hydrologic and biogeochemical processes. Rates of carbon cycling, mineral weathering, infiltration and snow melt are all influenced by Ts. Although broadly reflective of the climate, Ts is sensitive to local variations in cover (vegetative, litter, snow), topography (slope, aspect, position), and soil properties (texture, water content), resulting in a spatially and temporally complex distribution of Ts across the landscape. Understanding and quantifying the processes controlled by Ts requires an understanding of that distribution. Relatively few spatially distributed field Ts data exist, partly because traditional Ts data are point measurements. A relatively new technology, fiber optic distributed temperature system (FO-DTS), has the potential to provide such data but has not been rigorously evaluated in the context of remote, long term field research. We installed FO-DTS in a small experimental watershed in the Reynolds Creek Experimental Watershed (RCEW) in the Owyhee Mountains of SW Idaho. The watershed is characterized by complex terrain and a seasonal snow cover. Our objectives are to: (i) evaluate the applicability of fiber optic DTS to remote field environments and (ii) to describe the spatial and temporal variability of soil temperature in complex terrain influenced by a variable snow cover. We installed fiber optic cable at a depth of 10 cm in contrasting snow accumulation and topographic environments and monitored temperature along 750 m with DTS. We found that the DTS can provide accurate Ts data (+/- .4°C) that resolves Ts changes of about 0.03°C at a spatial scale of 1 m with occasional calibration under conditions with an ambient temperature range of 50°C. We note that there are site-specific limitations related cable installation and destruction by local fauna. The FO-DTS provide unique insight into the spatial and temporal variability of Ts in a landscape. We found strong seasonal trends in Ts variability controlled by snow cover and solar radiation as modified by topography. During periods of spatially continuous snow cover Ts was practically homogeneous throughout. In the absence of snow cover, Ts is highly variable, with most of the variability attributable to different topographic units defined by slope and aspect. During transition periods when snow melts out, Ts is highly variable within the watershed and within topographic units. The importance of accounting for these relatively small scale effects is underscored by the fact that the overall range of Ts in study area 600 m long is similar to that of the much large RCEW with 900 m elevation gradient.

Seyfried, M. S.; Link, T. E.

2013-12-01

77

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

78

Forcing, feedback and internal variability in global temperature trends.  

PubMed

Most present-generation climate models simulate an increase in global-mean surface temperature (GMST) since 1998, whereas observations suggest a warming hiatus. It is unclear to what extent this mismatch is caused by incorrect model forcing, by incorrect model response to forcing or by random factors. Here we analyse simulations and observations of GMST from 1900 to 2012, and show that the distribution of simulated 15-year trends shows no systematic bias against the observations. Using a multiple regression approach that is physically motivated by surface energy balance, we isolate the impact of radiative forcing, climate feedback and ocean heat uptake on GMST--with the regression residual interpreted as internal variability--and assess all possible 15- and 62-year trends. The differences between simulated and observed trends are dominated by random internal variability over the shorter timescale and by variations in the radiative forcings used to drive models over the longer timescale. For either trend length, spread in simulated climate feedback leaves no traceable imprint on GMST trends or, consequently, on the difference between simulations and observations. The claim that climate models systematically overestimate the response to radiative forcing from increasing greenhouse gas concentrations therefore seems to be unfounded. PMID:25631444

Marotzke, Jochem; Forster, Piers M

2015-01-29

79

Sea surface temperature variability in Panamá and Galápagos: Extreme temperatures causing coral bleaching  

Microsoft Academic Search

We examined associations between warm sea surface temperature (SST) anomalies and coral bleaching in the Galfipagos Islands and the Gulf of Panamfi, in the tropical eastern Pacific Ocean. Interannual SST variability is dominated by the E1 Nifio-Southern Oscillation phenomenon at Galfipagos, whereas only strong events have an SST signature in Panamfi. We explored various SST-related metrics potentially associated with bleaching

Guillermo P. Podestfi; Peter W. Glynn

1997-01-01

80

Resonance and Variable Temperature Raman Studies of Chloroperoxidase and Methemoglobin.  

NASA Astrophysics Data System (ADS)

Raman spectra of the heme proteins chloroperoxidase and methemoglobin, chemically and temperature modified, are obtained for laser excitation near the Soret absorption band. Numerous biochemical and physical results are obtained. The following observations for chloroperoxidase have been made. The scattered intensity for resonance (406.7 nm) excitation is at least twenty times that for near resonance (457.9 nm) excitation. In resonance only totally symmetric modes are enhanced. The positions of marker band I ((TURN) 1370 cm(' -1)) for both the native and reduced enzymes are lower than expected for high-spin heme proteins indicating a strongly electron donating axial ligand. From shifts in spin-sensitive Raman peaks as the temperature is lowered, a high-spin to low-spin transition of the heme iron is inferred. Raman spectra of chloroperoxidase liganded with small ions indicate that there is a second anion binding site near the heme. Photo-dissociation of CO from reduced chloroperoxidase is observed. The position of marker band I in the CO complex indicates that electron density is transferred from the heme onto the CO. The resonance Raman spectra of chloroperoxidase and cytochrome P-450 are nearly identical and are very different from those of horseradish peroxidase and cytochrome c. These results, particularly for the reduced enzymes, indicate that the heme sites in chloroperoxidase and P -450 are essentially the same. Raman spectra of a number of methemoglobins complexed with various small ions are obtained as a function of temperature in the region of spin-sensitive marker band (II) ((TURN) 1500 cm('-1)) for laser excitation near the Soret absorption band. For certain ligands, H(,2)O, N(,3)('-), OCN('-), OH('-) and SCN('-), the iron spin state changes from high spin to low spin with decreasing temperature. The relative spin concentrations are monitored by measuring the Raman intensity ratio, I(,h)/I(,1), of the high-spin and low -spin versions of marker band (II) as a function of temperature. This is the first study where the marker band technique is used to measure quantitatively spin transitions. For hydroxide and cyanate methemoglobin, log(I(,h)/I(,1)) varies linearly with 1/T, indicating a high-spin/low-spin thermal equilibrium. The data are analyzed to extract enthalpic and entropic changes. (DELTA)H values from Raman and static magnetic susceptibility techniques show good agreement. (DELTA)S values for horse hydroxide methemoglobin also agree. However, for cyanate methemoglobin, Raman and susceptibility (DELTA)S values differ substantially. Other evidence (ESR, optical, etc.) supports the Raman result. The discrepancy is probably due to the effects of freezing on the protein solution. Other methemoglobins show a discontinuity in the Raman intensity ratio at the freezing transition indicating a non-equilibrium situation where the freezing process drives the spin transition. Effects of freezing the protein solution on the spin transition are discussed. Both the high-spin and low-spin Raman frequencies are observed to remain constant (within (+OR-) 2 cm('-1)) when the temperature is varied. This is discussed in terms of core expansion and heme deformation. Experimental (DELTA)S values are much larger than the spin-only value. This is discussed in terms of a linear temperature dependence on the energy gap between the ('2)T(,2) ground state and the ('6)A(,1) first excited state. Variable temperature Raman data for carp azide methemoglobin with and without IHP indicate that the free energy for the spin transition decreases by 0.6 (+OR-) 0.3 kcal/mole when hemoglobin quaternary structure changes from R to T. Lack of any frequency shift in either the high-spin or low-spin Raman band upon addition of IHP is consistent with other evidence indicating no iron movement upon conversion of R to T quaternary forms.

Remba, Ronald David

1980-12-01

81

Variable temperature system using vortex tube cooling and fiber optic temperature measurement for low temperature magic angle spinning NMR.  

PubMed

We describe the construction and operation of a variable temperature (VT) system for a high field fast magic angle spinning (MAS) probe. The probe is used in NMR investigations of biological macromolecules, where stable setting and continuous measurement of the temperature over periods of several days are required in order to prevent sample overheating and degradation. The VT system described is used at and below room temperature. A vortex tube is used to provide cooling in the temperature range of -20 to 20 degrees C, while a liquid nitrogen-cooled heat exchanger is used below -20 degrees C. Using this arrangement, the lowest temperature that is practically achievable is -140 degrees C. Measurement of the air temperature near the spinning rotor is accomplished using a fiber optic thermometer that utilizes the temperature dependence of the absorption edge of GaAs. The absorption edge of GaAs also has a magnetic field dependence that we have measured and corrected for. This dependence was calibrated at several field strengths using the well-known temperature dependence of the (1)H chemical shift difference of the protons in methanol. PMID:15140428

Martin, Rachel W; Zilm, Kurt W

2004-06-01

82

Recent variability and trends of Antarctic near-surface temperature Andrew J. Monaghan,1  

E-print Network

Recent variability and trends of Antarctic near-surface temperature Andrew J. Monaghan,1 David H to anthropogenic influences or multidecadal variability. Citation: Monaghan, A. J., D. H. Bromwich, W. Chapman

Howat, Ian M.

83

Stratospheric temperature trends: impact of ozone variability and the QBO  

NASA Astrophysics Data System (ADS)

In most climate simulations used by the Intergovernmental Panel on Climate Change 2007 fourth assessment report, stratospheric processes are only poorly represented. For example, climatological or simple specifications of time-varying ozone concentrations are imposed and the quasi-biennial oscillation (QBO) of equatorial stratospheric zonal wind is absent. Here we investigate the impact of an improved stratospheric representation using two sets of perturbed simulations with the Hadley Centre coupled ocean atmosphere model HadGEM1 with natural and anthropogenic forcings for the 1979-2003 period. In the first set of simulations, the usual zonal mean ozone climatology with superimposed trends is replaced with a time series of observed zonal mean ozone distributions that includes interannual variability associated with the solar cycle, QBO and volcanic eruptions. In addition to this, the second set of perturbed simulations includes a scheme in which the stratospheric zonal wind in the tropics is relaxed to appropriate zonal mean values obtained from the ERA-40 re-analysis, thus forcing a QBO. Both of these changes are applied strictly to the stratosphere only. The improved ozone field results in an improved simulation of the stepwise temperature transitions observed in the lower stratosphere in the aftermath of the two major recent volcanic eruptions. The contribution of the solar cycle signal in the ozone field to this improved representation of the stepwise cooling is discussed. The improved ozone field and also the QBO result in an improved simulation of observed trends, both globally and at tropical latitudes. The Eulerian upwelling in the lower stratosphere in the equatorial region is enhanced by the improved ozone field and is affected by the QBO relaxation, yet neither induces a significant change in the upwelling trend.

Dall'Amico, Mauro; Gray, Lesley J.; Rosenlof, Karen H.; Scaife, Adam A.; Shine, Keith P.; Stott, Peter A.

2010-02-01

84

High variability of Greenland surface temperature over the past 4000 years estimated from trapped air  

E-print Network

]. However, the Greenland temperature trend diverges from the global trend in the last 168 years, which., 2009]. A deviation of the Greenland temperature from the global average temperature trend is likelyHigh variability of Greenland surface temperature over the past 4000 years estimated from trapped

Severinghaus, Jeffrey P.

85

An ignored variable: solution preparation temperature in protein crystallization  

PubMed Central

Protein crystallization is affected by many parameters, among which certain parameters have not been well controlled. The temperature at which the protein and precipitant solutions are mixed (i.e., the ambient temperature during mixing) is such a parameter that is typically not well controlled and is often ignored. In this paper, we show that this temperature can influence protein crystallization. The experimental results showed that both higher and lower mixing temperatures can enhance the success of crystallization, which follows a parabolic curve with an increasing ambient temperature. This work illustrates that the crystallization solution preparation temperature is also an important parameter for protein crystallization. Uncontrolled or poorly controlled room temperature may yield poor reproducibility in protein crystallization. PMID:25597864

Chen, Rui-Qing; Lu, Qin-Qin; Cheng, Qing-Di; Ao, Liang-Bo; Zhang, Chen-Yan; Hou, Hai; Liu, Yong-Ming; Li, Da-Wei; Yin, Da-Chuan

2015-01-01

86

An ignored variable: solution preparation temperature in protein crystallization  

NASA Astrophysics Data System (ADS)

Protein crystallization is affected by many parameters, among which certain parameters have not been well controlled. The temperature at which the protein and precipitant solutions are mixed (i.e., the ambient temperature during mixing) is such a parameter that is typically not well controlled and is often ignored. In this paper, we show that this temperature can influence protein crystallization. The experimental results showed that both higher and lower mixing temperatures can enhance the success of crystallization, which follows a parabolic curve with an increasing ambient temperature. This work illustrates that the crystallization solution preparation temperature is also an important parameter for protein crystallization. Uncontrolled or poorly controlled room temperature may yield poor reproducibility in protein crystallization.

Chen, Rui-Qing; Lu, Qin-Qin; Cheng, Qing-Di; Ao, Liang-Bo; Zhang, Chen-Yan; Hou, Hai; Liu, Yong-Ming; Li, Da-Wei; Yin, Da-Chuan

2015-01-01

87

Interannual variability of temperature and salinity in shallow water: Long Island Sound, New York  

Microsoft Academic Search

Variabilities of temperature and salinity over Long Island Sound (LIS), New York, are examined using observations from 1991 to 2002. There is a strong seasonal variation in the temperature, and its interannual variability is characterized by a higher variance during winter than summer. The salinity exhibits regular seasonal patterns driven by freshwater input, but there is a long-term change throughout

Younjoo J. Lee; Kamazima Lwiza

2005-01-01

88

The role of increasing temperature variability in European summer heatwaves  

Microsoft Academic Search

Instrumental observations and reconstructions of global and hemispheric temperature evolution reveal a pronounced warming during the past ~150 years. One expression of this warming is the observed increase in the occurrence of heatwaves. Conceptually this increase is understood as a shift of the statistical distribution towards warmer temperatures, while changes in the width of the distribution are often considered small.

Christoph Schär; Pier Luigi Vidale; Daniel Lüthi; Christoph Frei; Christian Häberli; Mark A. Liniger; Christof Appenzeller

2004-01-01

89

SPATIAL VARIABILITY OF REMOTELY SENSED SURFACE TEMPERATURE AT FIELD SCALE  

EPA Science Inventory

Bare soil surface temperatures (BST) and crop canopy temperatures (CCT) were collected from a 1-ha field in central Arizona using an infrared thermometer to determine whether they were spatially correlated. The measurements were taken from a two-dimensional random sampling patter...

90

Mean seasonal and spatial variability in global surface air temperature  

Microsoft Academic Search

Using terrestrial observations of shelter-height air temperature and shipboard measurements, a global climatology of mean monthly surface air temperature has been compiled. Data were obtained from ten sources, screened for coding errors, and redundant station records were removed. The combined data base consists of 17 986 independent terrestrial station records and 6 955 oceanic grid-point records. These data were then

D. R. Legates; C. J. Willmott

1990-01-01

91

Variable pressure insulating jackets for high-temperature batteries  

NASA Astrophysics Data System (ADS)

A new method is proposed for controlling the temperature of high-temperature batteries namely, varying the hydrogen pressure inside of multifoil insulation by varying the temperature of a reversible hydrogen getter. Calculations showed that the rate of heat loss through 1.5 cm of multifoil insulation between a hot-side temperature of 425 C and a cold-side temperature of 25 C could be varied between 17.6 W/m(sup 2) and 7,000 W/m(sup 2). This change in heat transfer rate can be achieved by varying the hydrogen pressure between 1.0 Pa and 1,000 Pa, which can be done with an available hydrogen gettering alloy operating in the range of 50 C to 250 C. This approach to battery cooling requires cylindrical insulating jackets, which are best suited for bipolar batteries having round cells approximately 10 to 18 cm in diameter.

Nelson, P. A.; Chilenskas, A. A.; Malecha, R. F.

1992-12-01

92

Seasonal variability in Arctic temperatures during early Eocene time  

NASA Astrophysics Data System (ADS)

As a deep time analog for today's rapidly warming Arctic region, early Eocene (52-53 Ma) rock on Ellesmere Island in Canada's High Arctic (˜ 79°N.) preserves evidence of lush swamp forests inhabited by turtles, alligators, primates, tapirs, and hippo-like Coryphodon. Although the rich flora and fauna of the early Eocene Arctic imply warmer, wetter conditions than at present, the quantification of Eocene Arctic climate has been more elusive. By analyzing oxygen isotope ratios of biogenic phosphate from mammal, fish, and turtle fossils from a single locality on central Ellesmere Island, we infer early Eocene Arctic temperatures, including mean annual temperature (MAT) of ˜ 8 °C, mean annual range in temperature of ˜ 16.5-19 °C, warm month mean temperature of 19-20 °C, and cold month mean temperature of 0-3.5 °C. Our seasonal range in temperature is similar to the range in estimated MAT obtained using different proxies. In particular, relatively high estimates of early Eocene Arctic MAT and SST by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in terrestrial soil bacteria and isoprenoid tetraether lipids in marine Crenarchaeota fall close to our warm month temperature, suggesting a bias towards summer values. From a paleontologic perspective, our temperature estimates verify that alligators and tortoises, by way of nearest living relative-based climatic inference, are viable paleoclimate proxies for mild, above-freezing year-round temperatures. Although for both of these reptilian groups, past temperature tolerances probably were greater than in living descendants.

Eberle, Jaelyn J.; Fricke, Henry C.; Humphrey, John D.; Hackett, Logan; Newbrey, Michael G.; Hutchison, J. Howard

2010-08-01

93

The temperature variability and heat waves in Serbia  

NASA Astrophysics Data System (ADS)

Temperature extremes are an important aspect of any climate change because ecosystems and societal responses are most sensitive to them. During July and August 2007 record values of temperatures were observed in south-eastern Europe. Serbia, Bulgaria and Greece were the European countries most affected by the heat wave. Record values of the maximum temperatures were observed over almost the whole territory of Serbia and in Smederevska Palanka, a temperature of 44.9 °C in July was registered, which was the absolute maximum value ever recorded. The highest increase over the previous absolute maximum temperature, dating back to 1888, of 3.1 °C was registered in Belgrade. In Serbia, the mean summer temperature of 2007 exceeded the 1961 - 1990 mean by 3 °C, corresponding to an excess of up to 4 standard deviations. Also, the mean July temperature in 2007 exceeded the 1961 - 1990 mean by 3.3 °C, corresponding to an excess of up to 3 standard deviations. The Warm Spell Duration Indicator (WSDI), from which the duration and severity of the heat waves are estimated, was applied to the series of the daily maximum temperatures in Smederevska Palanka (SP). An extraordinary heat wave occurred in Serbia from July 14 to July 24 in 2007. An analysis of the daily maximum temperatures and heat waves during the summer of 2007 revealed significant changes in the trends of anomalies and extreme (90 %) quantiles. 1987, 2007 and 1998 were the three years with the longest heat waves from the beginning of measurements, having a duration of 13, 11 and 10 days, respectively. The longest heat wave observed in 1987 did not reach the severity of the heat wave in July 2007. The atmospheric circulation at 500-hPa resulted in the horizontal advection of warm air masses from northern Africa across central and eastern Mediterranean towards the Balkans. The 500-hPa geopotential anomalies (according to the reference period 1961 - 1990) of the summer and July 2007 exceeded 35 and 40 gpm over Serbia, respectively. The warm advection was manifested in temperature anomalies over Serbia, reaching up to 3.5 and 4.0 °C for the summer and July 2007, respectively.

Unkasevic, M.; Tosic, I.

2010-09-01

94

A thermo-mechanical fatigue damage model for variable temperature and loading amplitude conditions  

Microsoft Academic Search

A fatigue life prediction method for thermo-mechanical fatigue damage under variable temperature and loading amplitudes was proposed. In this approach, a rainflow cycle counting technique was used to extract cycle counts from the mechanical loading history. For each loading cycle, an equivalent damage temperature was determined. Once the equivalent temperature was used, the loop would be guaranteed closed. This approach

Hong Tae Kang; Yung-Li Lee; Jim Chen; David Fan

2007-01-01

95

Amplification and dampening of soil respiration by changes in temperature variability  

USGS Publications Warehouse

Accelerated release of carbon from soils is one of the most important feed backs related to anthropogenically induced climate change. Studies addressing the mechanisms for soil carbon release through organic matter decomposition have focused on the effect of changes in the average temperature, with little attention to changes in temperature vari-ability. Anthropogenic activities are likely to modify both the average state and the variability of the climatic system; therefore, the effects of future warming on decomposition should not only focus on trends in the average temperature, but also variability expressed as a change of the probability distribution of temperature.Using analytical and numerical analyses we tested common relationships between temperature and respiration and found that the variability of temperature plays an important role determining respiration rates of soil organic matter. Changes in temperature variability, without changes in the average temperature, can affect the amount of carbon released through respiration over the long term. Furthermore, simultaneous changes in the average and variance of temperature can either amplify or dampen there release of carbon through soil respiration as climate regimes change. The effects depend on the degree of convexity of the relationship between temperature and respiration and the magnitude of the change in temperature variance. A potential consequence of this effect of variability would be higher respiration in regions where both the mean and variance of temperature are expected to increase, such as in some low latitude regions; and lower amounts of respiration where the average temperature is expected to increase and the variance to decrease, such as in northern high latitudes.

Sierra, C.A.; Harmon, M.E.; Thomann, E.; Perakis, S.S.; Loescher, H.W.

2011-01-01

96

Variable-transparency wall regulates temperatures of structures  

NASA Technical Reports Server (NTRS)

An effective temperature regulating wall consists of one layer /e.g., one of the paraffins/ relatively opaque to thermal radiation in the solid state and transparent to it in the molten state and placed between two transparent layers. A mirror coating is applied to back layer.

Osullivan, W. J., Jr.

1964-01-01

97

Variable temperature effects on release rates of readily soluble nuclides  

SciTech Connect

In this paper we study the effect of temperature on the release rate of readily soluble nuclides, as affected by a time-temperature dependent diffusion coefficient. In this analysis ground water fills the voids in the waste package at t = 0 and one percent of the inventories of cesium and iodine are immediately dissolved into the void water. Mass transfer resistance of partly failed container and cladding is conservatively neglected. The nuclides move through the void space into the surrounding rock under a concentration gradient. We use an analytic solution to compute the nuclide concentration in the gap or void, and the mass flux rate into the porous rock. 8 refs., 4 figs.

Kim, C.-L.; Light, W.B.; Lee, W.W.-L.; Chambre, P.L.; Pigford, T.H. (Korea Advanced Energy Research Inst., Daeduk (Republic of Korea); Lawrence Berkeley Lab., CA (USA))

1988-09-01

98

Variable-Temperature-Gradient Device for Solidification Research  

NASA Technical Reports Server (NTRS)

Device for research in solidification and crystal growth allows crystallization of melt observed as occurs. Temperature gradient across melt specimen increased or decreased rapidly while solidification front proceeds at constant speed across sample. Device moves sample at same speed, thereby holding position of liquid/solid interface stationary within field of optical microscope. Device, variabletemperature-gradient microscope stage, used to study crystal growth at constant rate while thermal driving force is varied.

Kaukler, W. F.

1985-01-01

99

Free and forced tropical variability: role of the wind-evaporation-sea surface temperature (WES) feedback  

E-print Network

The Wind-Evaporation-Sea Surface Temperature (WES) feedback is believedto play an important role in the tropics, where climate variability is governed byatmosphere-ocean coupled interactions. This dissertation reports on studies to distinctlyisolate...

Mahajan, Salil

2009-05-15

100

Performance Optimization of an Irreversible Heat Pump with Variable-temperature Heat Reservoirs  

E-print Network

An irreversible cycle model of a heat pump operating between two variable-temperature heat reservoirs is established and used to analyze the performance of the heat pump affected by heat resistances, heat leakage and internal dissipation...

Huang, Y.; Sun, D.

2006-01-01

101

Climatology of the terdiurnal tides in the mesopause region: Results of airglow and temperature observations over Almaty (43.03ºN, 76.58ºE)  

NASA Astrophysics Data System (ADS)

Nightglow emission rate and rotational temperature observations of O2 (0-1) Atmospheric band by Mesopause Oxygen Rotational Temperature Imager (MORTI) have been carried out at Almaty observatory (43.03o N; 76.58o E). Day-to-day variability of the terdiurnal tides for the 1997 - 2000 and 2005-2006 has been analysed. Airglow and temperature observations in the mesopause from MORTI are shown clear seasonal variations of terdiurnal tides. Preliminary results of Spectral Airglow Temperature Imager (SATI-4) installed at Almaty observatory in 2007 are presented and discussed.

Aushev, Victor

102

Multisensor analysis of NDVI, surface temperature and biophysical variables at a mixed grassland site  

Microsoft Academic Search

A unique remotely sensed data set derived for a temperate mixed grassland in the central United States was used to test the comparability of a suite of satellite and aircraft sensors, and to characterize temporal variability in the normalized diÄ erence vegetation index (NDVI), retrieved surface radiant temperature (Ts), and surface biophysical variables. The temporal evolution of atmospherically corrected NDVI

S. J. GOETZ

1997-01-01

103

Interannual-to-multidecadal climate variability and its relationship to global sea surface temperatures  

E-print Network

) and the multi-decadal North Atlantic Oscillation (NAO). The variable of greatest interest is sea surfaceInterannual-to-multidecadal climate variability and its relationship to global sea surface temperatures David B. Enfield 1 and Alberto M. Mestas-Nuñez 2 1 NOAA Atlantic Oceanographic and Meteorological

104

ASSOCIATIONS OF DECADAL TO MULTIDECADAL SEA-SURFACE TEMPERATURE VARIABILITY WITH UPPER COLORADO RIVER FLOW1  

E-print Network

reflects variability associated with the Atlantic Multidecadal Oscillation and the second RPC (RPC2, with critical implications for UCRB water resource management. (KEY TERMS: Colorado River; Atlantic MultidecadalASSOCIATIONS OF DECADAL TO MULTIDECADAL SEA-SURFACE TEMPERATURE VARIABILITY WITH UPPER COLORADO

105

Temporal and spatial variability of surface temperature over Texas  

E-print Network

workstation crises and related dilly innias. Finally, I would like to extend thanks to Professor John F. Griffiths and Dr. . James P. McGuirk. both of the Meteorology Department. for their fruitful discussions with me about the finer points of EOF analysis... with water is considered to be the main factor in producing this contrast, known as the continentality effect. Prescott and Collins (1951) calculated the lag of suri'ace temperature behind solar radiation on a global basis and for thc United States using...

Moninski, Anthony David

2012-06-07

106

Temperature Responses to Spectral Solar Variability on Decadal Time Scales  

NASA Technical Reports Server (NTRS)

Two scenarios of spectral solar forcing, namely Spectral Irradiance Monitor (SIM)-based out-of-phase variations and conventional in-phase variations, are input to a time-dependent radiative-convective model (RCM), and to the GISS modelE. Both scenarios and models give maximum temperature responses in the upper stratosphere, decreasing to the surface. Upper stratospheric peak-to-peak responses to out-of-phase forcing are approx.0.6 K and approx.0.9 K in RCM and modelE, approx.5 times larger than responses to in-phase forcing. Stratospheric responses are in-phase with TSI and UV variations, and resemble HALOE observed 11-year temperature variations. For in-phase forcing, ocean mixed layer response lags surface air response by approx.2 years, and is approx.0.06 K compared to approx.0.14 K for atmosphere. For out-of-phase forcing, lags are similar, but surface responses are significantly smaller. For both scenarios, modelE surface responses are less than 0.1 K in the tropics, and display similar patterns over oceanic regions, but complex responses over land.

Cahalan, Robert F.; Wen, Guoyong; Harder, Jerald W.; Pilewskie, Peter

2010-01-01

107

Long-term variability in Arctic sea surface temperatures  

NASA Astrophysics Data System (ADS)

In this study, we used 30 years of an operational sea surface temperature (SST) product, the NOAA Optimum Interpolation (OI) SST Version 2 dataset, to examine variations in Arctic SSTs during the period December 1981-October 2011. We computed annual SST anomalies and interannual trends in SST variations for the period 1982-2010; during this period, marginal (though statistically significant) increases in SSTs were observed in oceanic regions poleward of 60°N. A warming trend is evident over most of the Arctic region, the Beaufort Sea, the Chuckchi Sea, Hudson Bay, the Labrador Sea, the Iceland Sea, the Norwegian Sea, Bering Strait, etc.; Labrador Sea experienced higher temperature anomalies than those observed in other regions. However, cooling trends were observed in the central Arctic, some parts of Baffin Bay, the Kara Sea (south of Novaya Zemlya), the Laptev Sea, the Siberian Sea, and Fram Strait. The central Arctic region experienced a cooling trend only during 1992-2001; warming trends were observed during 1982-1991 and 2002-2010. We also examined a 30-yr (1982-2011) record of summer season (June-July-August) SST variations and a 29-yr (1982-2010) record of September SST variations, the results of which are discussed.

Singh, Rajkumar Kamaljit; Maheshwari, Megha; Oza, Sandip R.; Kumar, Raj

2013-09-01

108

Note: A variable temperature cell for spectroscopy of thin films.  

PubMed

We report the design and construction of a cell that enables precisely controlled measurement of UV?Vis spectra of thin films on transparent substrates at temperatures up to 800 K. The dimensions of the setup are accommodated by a standard Varian Cary 5E spectrophotometer allowing for widespread use in standard laboratory settings. The cell also fits in a Bio-Rad IR-spectrometer. The cell is constructed with an outer water cooled heat shield of aluminum and an inner sample holder with heating element, thermo-resistor and windows, made from nickel coated copper. The cell can operate both in air, and with an inert gas filling. We illustrate the utility of the cell by characterization of three commercially available near infrared absorbers that are commonly used for laser welding of plastics and are known to possess high thermal stability. PMID:23635240

Brock-Nannestad, T; Nielsen, C B; Bak, H Ø; Pittelkow, M

2013-04-01

109

A Mass-Selective Variable-Temperature Drift Tube Ion Mobility-Mass Spectrometer for Temperature Dependent Ion Mobility Studies  

NASA Astrophysics Data System (ADS)

A hybrid ion mobility-mass spectrometer (IM-MS) incorporating a variable-temperature (80-400 K) drift tube is presented. The instrument utilizes an electron ionization (EI) source for fundamental small molecule studies. Ions are transferred to the IM-MS analyzer stages through a quadrupole, which can operate in either broad transmission or mass-selective mode. Ion beam modulation for the ion mobility experiment is accomplished by an electronic shutter gate. The variable-temperature ion mobility spectrometer consists of a 30.2 cm uniform field drift tube enclosed within a thermal envelope. Subambient temperatures down to 80 K are achievable through cryogenic cooling with liquid nitrogen, while elevated temperatures can be accessed through resistive heating of the envelope. Mobility separated ions are mass analyzed by an orthogonal time-of-flight (TOF) mass spectrometer. This report describes the technological considerations for operating the instrument at variable temperature, and preliminary results are presented for IM-MS analysis of several small mass ions. Specifically, mobility separations of benzene fragment ions generated by EI are used to illustrate significantly improved (greater than 50%) ion mobility resolution at low temperatures resulting from decreased diffusional broadening. Preliminary results on the separation of long-lived electronic states of Ti+ formed by EI of TiCl4 and hydration reactions of Ti+ with residual water are presented.

May, Jody C.; Russell, David H.

2011-07-01

110

EFFECT OF VARIABLE TEMPERATURE ON THE INFECTION FREQUENCY OF SPHAEROTHECA MACULARIS ON HUMULUS LUPULUS.  

Technology Transfer Automated Retrieval System (TEKTRAN)

The effect of variable temperature on the infection frequency of Sphaerotheca macularis (sym. S. humuli) on Humulus lupulus L. (Hops) was investigated. Potted 'Symphony' hop plants were inoculated and exposed to different supra-optimal temperature regimes for varying amounts of time. Infection...

111

Influence of Variable Interannual Summer Water Temperatures on Brook Trout Growth, Consumption, Reproduction, and  

E-print Network

Influence of Variable Interannual Summer Water Temperatures on Brook Trout Growth, Consumption population-level characteristics is rare. An 8-year field study of brook trout Salvelinus fontinalis temperatures strongly influenced brook trout population-level characteristics. We quantified chronic thermal

Kraft, Clifford E.

112

Interannual variability of temperature and salinity in shallow water: Long Island Sound, New York  

NASA Astrophysics Data System (ADS)

Variabilities of temperature and salinity over Long Island Sound (LIS), New York, are examined using observations from 1991 to 2002. There is a strong seasonal variation in the temperature, and its interannual variability is characterized by a higher variance during winter than summer. The salinity exhibits regular seasonal patterns driven by freshwater input, but there is a long-term change throughout LIS. Anomaly maps of temperature and salinity indicate strong longitudinal gradients increasing in the westward direction. Empirical orthogonal function analyses indicate that the first modes of temperature and salinity anomalies can explain 87% and 89% of the total variances, respectively. The first mode principle components of the temperature and salinity anomaly contain quasi-biennial periodicities. The salinity anomaly also contains an additional signal at a decadal timescale. Seasonal variations in the temperature and salinity are primarily associated with heat flux and freshwater discharge. However, the surface heat flux anomaly only accounts for 17% of the total variance of the time rate change of the temperature anomaly, and the freshwater discharge anomaly explains 25% of the variance of the salinity anomaly. Contrary to traditional paradigm about estuaries, this result shows that forcings other than local processes control the interannual variabilities of the temperature and salinity in LIS, most probably through horizontal exchanges. Also, the significant correlation between the salinity anomaly and the Gulf Stream (GS) position suggests that the interannual variability of salinity in LIS is possibly connected to shelf slope water properties associated with changes in the GS position.

Lee, Younjoo J.; Lwiza, Kamazima

2005-09-01

113

Does diurnal temperature variability affect growth in juvenile Atlantic salmon Salmo salar?  

PubMed

This study investigated the effects of diurnal temperature variability (>7° C) on the growth of 1+ year Atlantic salmon Salmo salar. Experimental manipulation of water temperature was used to simulate: (1) constant and (2) naturally varying thermal regimes with similar daily mean values. Data from two replicates of four treatments (two thermal and two feeding regimes) were collected over 6 months corresponding to the main spring to summer growth period. Fish growth was assessed at fortnightly intervals. Small but significant differences in mean fork length (L(F) ) and mass were observed between temperature treatments, with smaller, lighter fish under the variable temperature regime. The effects of temperature regime on growth were independent of food ration. At termination of the experiment, the median L(F) and mass of fish exposed to the variable temperature regime were estimated, respectively, to be 2· 6 and 8· 0% less than those under the constant regime. Given the relatively small differences in growth attributable to variable temperature regime in these experiments, it is suggested that mean daily temperatures are adequate to inform juvenile growth models for field-based studies. PMID:21284627

Imholt, C; Malcolm, I A; Bacon, P J; Gibbins, C N; Soulsby, C; Miles, M; Fryer, R J

2011-02-01

114

Variable-temperature independently driven four-tip scanning tunneling microscope  

E-print Network

temperature down to 7 K, combined with a scanning electron microscope SEM . Four STM tips are mechanically with cooling system and scanning electron microscope SEM that is indispensable to navigate the multitipsVariable-temperature independently driven four-tip scanning tunneling microscope Rei Hobara,a Naoka

Hasegawa, Shuji

115

Late Holocene variability of upper North Atlantic Deep Water temperature and salinity  

E-print Network

Late Holocene variability of upper North Atlantic Deep Water temperature and salinity Thomas M equation. Results suggest that the temperature of upper North Atlantic Deep Water (dominated by Labrador waters to intermediate depths. Our reconstructed late Holocene ranges in upper North Atlantic Deep Water

Born, Andreas

116

Tropical/extratropical forcing on wintertime variability of the extratropical temperature and circulation  

NASA Astrophysics Data System (ADS)

The secular trends and interannual variability of wintertime temperatures over northern extratropical lands and circulations over the northern hemisphere are examined using the NCEP/NCAR reanalysis from 1961 to 2010. A primitive equation dry atmospheric model, driven by time-averaged forcing in each winter diagnosed from the NCEP reanalysis, is then employed to investigate the influences of tropical and extratropical forcing on the temperature and circulation variability. The model has no topography and the forcing is thus model specific. The dynamic and thermodynamic maintenances of the circulation and temperature anomalies are also diagnosed. Distinct surface temperature trends over 1961-1990 and 1991-2010 are found over most of the extratropical lands. The trend is stronger in the last two decades than that before 1990, particularly over eastern Canadian Arctic, Greenland, and Asia. The exchange of midlatitude and polar air supports the temperature trends. Both the diagnosed extratropical and tropical forcings contribute to the temperature and circulation trends over 1961-1990, while the extratropical forcing dominates tropical forcing for the trends over 1991-2010. The contribution of the tropical forcing to the trends is sensitive to the period considered. The temperature and circulation responses to the diagnosed tropical and extratropical forcings are approximately additive and partially offsetting. Covariances between the interannual surface temperature and 500-hPa geopotential anomalies for the NCEP reanalysis from 1961 to 2010 are dominated by two leading modes associated with the North Atlantic Oscillation (NAO) and Pacific-North American (PNA) teleconnection patterns. The diagnosed extratropical forcing accounts for a significant part of the NAO and PNA associated variability, including the interannual variability of stationary wave anomalies, as well as dynamically and thermodynamically synoptic eddy feedbacks over the North Atlantic and North Pacific. The tropical forcing contributes to the PNA related temperature and circulation variability, but has a small contribution to the NAO associated variability. Additionally, relative contributions of tropical Indian and Pacific forcings are also assessed.

Yu, Bin; Lin, Hai

2013-03-01

117

Natural and forced air temperature variability in the Labrador region of Canada during the past century  

NASA Astrophysics Data System (ADS)

Evaluation of Labrador air temperatures over the past century (1881-2011) shows multi-scale climate variability and strong linkages with ocean-atmospheric modes of variability and external forcings. The Arctic Oscillation, Atlantic Multidecadal Oscillation, and El Nino Southern Oscillation are shown to be the dominant seasonal and interannual drivers of regional air temperature variability for most of the past century. Several global climate models show disagreement with observations on the rate of recent warming which suggests that models are currently unable to reproduce regional climate variability in Labrador air temperature. Using a combination of empirical statistical modeling and global climate models, we show that 33 % of the variability in annual Labrador air temperatures over the period 1881-2011 can be explained by natural factors alone; however, the inclusion of anthropogenic forcing increases the explained variance to 65 %. Rapid warming over the past 17 years is shown to be linked to both natural and anthropogenic factors with several anomalously warm years being primarily linked to recent anomalies in the Arctic Oscillation and North Atlantic sea surface temperatures. Evidence is also presented that both empirical statistical models and global climate models underestimate the regional air temperature response to ocean salinity anomalies and volcanic eruptions. These results provide important insight into the predictability of future regional climate impacts for the Labrador region.

Way, Robert G.; Viau, Andre E.

2014-08-01

118

Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes  

SciTech Connect

Complexation of neodymium(III) with nitrate was studied at variable temperatures (25, 40, 55 and 70 C) by spectrophotometry and microcalorimetry. The NdNO{sub 3}{sup 2+} complex is weak and becomes slightly stronger as the temperature is increased. The enthalpy of complexation at 25 C was determined by microcalorimetry to be small and positive, (1.5 {+-} 0.2) kJ {center_dot} mol{sup -1}, in good agreement with the trend of the stability constant at variable temperatures. Luminescence emission spectra and lifetime of Eu(III) in nitrate solutions suggest that inner-sphere and bidentate complexes form between trivalent lanthanides (Nd{sup 3+} and Eu{sup 3+}) and nitrate in aqueous solutions. Specific Ion Interaction approach (SIT) was used to obtain the stability constants of NdNO{sub 3}{sup 2+} at infinite dilution and variable temperatures.

Rao, Linfeng; Tian, Guoxin

2008-12-10

119

Controls of subsurface temperature variability in a western boundary upwelling system  

NASA Astrophysics Data System (ADS)

The mechanisms controlling subsurface temperature variability on the outer shelf in a western boundary upwelling system are quantified using observations from a mooring deployed off Cabo Frio, Brazil. Results from a multiple linear regression analysis reveal that, in addition to low-frequency variations associated with the seasonal evolution of temperature, the dominant mechanisms controlling temperature variability are wind stress curl-driven upwelling, cross-isobath transport, the proximity of the Brazil Current to the shelf break, and perhaps changes in the strength of tidal mixing associated with the spring-neap cycle. The influence of the proximity of the Brazil Current decreases strongly with depth, being restricted to the top 80 m. Regression coefficients indicate that the relative contributions from the different forcings are roughly similar and that no single process has a dominant role explaining temperature variability near the shelf break. These suggest that successful modeling efforts in the region must adequately represent each of those processes.

Belem, Andre L.; Castelao, Renato M.; Albuquerque, Ana Luiza

2013-04-01

120

Entropy-generation analysis for variable-viscosity channel flow with non-uniform wall temperature  

Microsoft Academic Search

This paper is an analytical study of inherent irreversibility in the flow of a variable-viscosity fluid through a channel with a non-uniform wall temperature. It is assumed that the channel is narrow and the fluid viscosity varies linearly with temperature. Analytical expressions for fluid velocity and temperature are derived and employed to obtain expressions for volumetric entropy-generation numbers, irreversibility distribution

O. D. Makinde

2008-01-01

121

A variable-temperature nanostencil compatible with a low-temperature scanning tunneling microscope/atomic force microscope  

SciTech Connect

We describe a nanostencil lithography tool capable of operating at variable temperatures down to 30 K. The setup is compatible with a combined low-temperature scanning tunneling microscope/atomic force microscope located within the same ultra-high-vacuum apparatus. The lateral movement capability of the mask allows the patterning of complex structures. To demonstrate operational functionality of the tool and estimate temperature drift and blurring, we fabricated LiF and NaCl nanostructures on Cu(111) at 77 K.

Steurer, Wolfram, E-mail: wst@zurich.ibm.com; Gross, Leo; Schlittler, Reto R.; Meyer, Gerhard [IBM Research-Zurich, 8803 Rüschlikon (Switzerland)] [IBM Research-Zurich, 8803 Rüschlikon (Switzerland)

2014-02-15

122

Ocean surface temperature variability: large model-data differences at decadal and longer periods.  

PubMed

The variability of sea surface temperatures (SSTs) at multidecadal and longer timescales is poorly constrained, primarily because instrumental records are short and proxy records are noisy. Through applying a new noise filtering technique to a global network of late Holocene SST proxies, we estimate SST variability between annual and millennial timescales. Filtered estimates of SST variability obtained from coral, foraminifer, and alkenone records are shown to be consistent with one another and with instrumental records in the frequency bands at which they overlap. General circulation models, however, simulate SST variability that is systematically smaller than instrumental and proxy-based estimates. Discrepancies in variability are largest at low latitudes and increase with timescale, reaching two orders of magnitude for tropical variability at millennial timescales. This result implies major deficiencies in observational estimates or model simulations, or both, and has implications for the attribution of past variations and prediction of future change. PMID:25385623

Laepple, Thomas; Huybers, Peter

2014-11-25

123

An interaction network perspective on the relation between patterns of sea surface temperature variability and global mean surface temperature  

NASA Astrophysics Data System (ADS)

On interannual- to multidecadal timescales variability in sea surface temperature appears to be organized in large-scale spatiotemporal patterns. In this paper, we investigate these patterns by studying the community structure of interaction networks constructed from sea surface temperature observations. Much of the community structure can be interpreted using known dominant patterns of variability, such as the El Niño/Southern Oscillation and the Atlantic Multidecadal Oscillation. The community detection method allows us to bypass some shortcomings of Empirical Orthogonal Function analysis or composite analysis and can provide additional information with respect to these classical analysis tools. In addition, the study of the relationship between the communities and indices of global surface temperature shows that, while El Niño-Southern Oscillation is most dominant on interannual timescales, the Indian West Pacific and North Atlantic may also play a key role on decadal timescales. Finally, we show that the comparison of the community structure from simulations and observations can help detect model biases.

Tantet, A.; Dijkstra, H. A.

2014-01-01

124

Recent Climate Variability in Antarctica from Satellite-derived Temperature Data  

NASA Technical Reports Server (NTRS)

Recent Antarctic climate variability on month-to-month to interannual time scales is assessed through joint analysis of surface temperatures from satellite thermal infrared observations (T(sub IR)) and passive microwave brightness temperatures (T(sub B)). Although Tw data are limited to clear-sky conditions and T(sub B) data are a product of the temperature and emissivity of the upper approx. 1m of snow, the two data sets share significant covariance. This covariance is largely explained by three empirical modes, which illustrate the spatial and temporal variability of Antarctic surface temperatures. T(sub B) variations are damped compared to TIR variations, as determined by the period of the temperature forcing and the microwave emission depth; however, microwave emissivity does not vary significantly in time. Comparison of the temperature modes with Southern Hemisphere (SH) 500-hPa geopotential height anomalies demonstrates that Antarctic temperature anomalies are predominantly controlled by the principal patterns of SH atmospheric circulation. The leading surface temperature mode strongly correlates with the Southern Annular Mode (SAM) in geopotential height. The second temperature mode reflects the combined influences of the zonal wavenumber-3 and Pacific South American (PSA) patterns in 500-hPa height on month-to-month timescales. ENSO variability projects onto this mode on interannual timescales, but is not by itself a good predictor of Antarctic temperature anomalies. The third temperature mode explains winter warming trends, which may be caused by blocking events, over a large region of the East Antarctic plateau. These results help to place recent climate changes in the context of Antarctica's background climate variability and will aid in the interpretation of ice core paleoclimate records.

Schneider, David P.; Steig, Eric J.; Comiso, Josefino C.

2004-01-01

125

Effects of outdoor temperature on changes in physiological variables before and after lunch in healthy women  

NASA Astrophysics Data System (ADS)

Previous studies of autonomic nervous system responses before and after eating when controlling patient conditions and room temperature have provided inconsistent results. We hypothesized that several physiological parameters reflecting autonomic activity are affected by outdoor temperature before and after a meal. We measured the following physiological variables before and after a fixed meal in 53 healthy Japanese women: skin temperature, systolic and diastolic blood pressure, salivary amylase, blood glucose, heart rate, and heart rate variability. We assessed satiety before and after lunch using a visual analog scale (100 mm). We recorded outdoor temperature, atmospheric pressure, and relative humidity. Skin temperature rose significantly 1 h after eating (greater in cold weather) (P = 0.008). Cold weather markedly influenced changes in diastolic blood pressure before (P = 0.017) and after lunch (P = 0.013). Fasting salivary amylase activity increased significantly in cold weather but fell significantly after lunch (significantly greater in cold weather) (P = 0.007). Salivary amylase was significantly associated with cold weather, low atmospheric pressure, and low relative humidity 30 min after lunch (P < 0.05). Cold weather significantly influenced heart rate variability (P = 0.001). The decreased low frequency (LF)/high frequency (HF) ratio, increased ? LF/HF ratio, and increased ? salivary amylase activity imply that cold outdoor temperature is associated with dominant parasympathetic activity after lunch. Our results clarify the relationship between environmental factors, food intake, and autonomic system and physiological variables, which helps our understanding of homeostasis and metabolism.

Okada, Masahiro; Kakehashi, Masayuki

2014-03-01

126

Linkages Between Multiscale Global Sea Surface Temperature Change and Precipitation Variabilities in the US  

NASA Technical Reports Server (NTRS)

A growing number of evidence indicates that there are coherent patterns of variability in sea surface temperature (SST) anomaly not only at interannual timescales, but also at decadal-to-inter-decadal timescale and beyond. The multi-scale variabilities of SST anomaly have shown great impacts on climate. In this work, we analyze multiple timescales contained in the globally averaged SST anomaly with and their possible relationship with the summer and winter rainfall in the United States over the past four decades.

Lau, K. M.; Weng, Heng-Yi

1999-01-01

127

Associations of multi-decadal sea-surface temperature variability with US drought  

Microsoft Academic Search

Recent research suggests a link between drought occurrence in the conterminous United States (US) and sea surface temperature (SST) variability in both the tropical Pacific and North Atlantic Oceans on decadal to multidecadal (D2M) time scales. Results show that the Atlantic Multidecadal Oscillation (AMO) is the most consistent indicator of D2M drought variability in the conterminous US during the 20th

Gregory J. McCabe; Julio L. Betancourt; Stephen T. Gray; Michael A. Palecki; Hugo G. Hidalgo

2008-01-01

128

Indian Ocean sea surface temperature variability and change since 1960s: forcing and process  

Microsoft Academic Search

Indian Ocean sea surface temperature (SST) variability and change since 1960s are investigated using global coupled models,the Community Climate System Model version 3 (CCSM3) and parallel climate model (PCM). Results from the CCSM3 and a series of PCM experiments are analyzed in order to understand the roles played by internal variability, human-induced warming, and external forcing in causing the SST

W. Han; G. A. Meehl; A. Hu

2005-01-01

129

The changing role of temperature, precipitation and elevation on snowpack variability in Switzerland  

NASA Astrophysics Data System (ADS)

Snowpack is a source of environmental and economic richness in the Swiss Alps. However, duration and depth of snowpack has suffered a reduction during the last three decades due to current climate warming. This is especially noticable at low-to-middle elevation sites, where temperature is the main constraint for snowpack variability. This work assesses the role of elevation on determining the relative contribution of temperature and precipitation as predictors of snowpack variability in Switzerland. Multiple regression models allowed us finding a linear relationship between the predictive skill of temperature (negative) and precipitation (positive) on snowpack variability, and the terrain elevation. We, moreover identifyed a threshold around the 1400m a.s.l. below which temperature is the main explanatory variable, and above which precipitation becomes a better predictor of snowpack variability. Results highlights as well that the elevation of this threshold has increased on time as climated warmed. This has important implications for the future viability of snow-dependent industries in Switzerland, where projections indicate a continuous warming during the course of the 21st century.

Morán Tejeda, Enrique; López Moreno, J. Ignacio; Beniston, Martin

2013-04-01

130

Sea surface temperature variability in the southwest tropical Pacific since AD 1649  

NASA Astrophysics Data System (ADS)

A prime focus of research is differentiating the contributions of natural climate variability from those that are anthropogenically forced, especially as it relates to climate prediction. The short length of instrumental records, particularly from the South Pacific, hampers this research, specifically for investigations of decadal to centennial scale variability. Here we present a sea surface temperature (SST) reconstruction derived from highly reproducible records of strontium-to-calcium ratios (Sr/Ca) in corals from New Caledonia to investigate natural SST variability in the southwest tropical Pacific from AD 1649-1999. Our results reveal periods of warmer and colder temperatures of the order of decades during the Little Ice Age that do not correspond to long-term variations in solar irradiance or the 11-year sunspot cycle. We suggest that solar variability does not explain decadal to centennial scale SST variability in reconstructions from the southwest tropical Pacific. Our SST reconstruction covaries with the Southern Hemisphere Pacific decadal oscillation and the South Pacific decadal oscillation, from which SST anomalies in the southwest Pacific are linked to precipitation anomalies in the western tropical Pacific. We find that decadal scale SST variability has changed in strength and periodicity after 1893, suggesting a shift in natural variability for this location.

Delong, Kristine L.; Quinn, Terrence M.; Taylor, Frederick W.; Lin, Ke; Shen, Chuan-Chou

2012-11-01

131

Modes of zonal mean temperature variability 20-100 km from the TIMED/SABER observations  

NASA Astrophysics Data System (ADS)

In this study we investigate the spatial variabilities of the zonal mean temperature (20-100 km) from the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics)/SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite using the empirical orthogonal functions (EOFs). After removing the climatological annual mean, the first three EOFs are able to explain 87.0% of temperature variabilities. The primary EOF represents 74.1% of total anomalies and is dominated by the north-south contrast. Patterns in the second and third EOFs are related to the semiannual oscillations (SAO) and mesospheric temperature inversions (MTI), respectively. The quasi-biennial oscillation (QBO) component is also decomposed into the seventh EOF with contributions of 1.2%. Last, we use the first three modes and annual mean temperature to reconstruct the data. The result shows small differences are in low latitude, which increase with latitude in the middle stratosphere and upper mesosphere.

Jiang, Y.; Sheng, Z.; Shi, H. Q.

2014-03-01

132

Separating the influence of temperature, drought, and fire on interannual variability in atmospheric CO2  

NASA Astrophysics Data System (ADS)

response of the carbon cycle in prognostic Earth system models (ESMs) contributes significant uncertainty to projections of global climate change. Quantifying contributions of known drivers of interannual variability in the growth rate of atmospheric carbon dioxide (CO2) is important for improving the representation of terrestrial ecosystem processes in these ESMs. Several recent studies have identified the temperature dependence of tropical net ecosystem exchange (NEE) as a primary driver of this variability by analyzing a single, globally averaged time series of CO2 anomalies. Here we examined how the temporal evolution of CO2 in different latitude bands may be used to separate contributions from temperature stress, drought stress, and fire emissions to CO2 variability. We developed atmospheric CO2 patterns from each of these mechanisms during 1997-2011 using an atmospheric transport model. NEE responses to temperature, NEE responses to drought, and fire emissions all contributed significantly to CO2 variability in each latitude band, suggesting that no single mechanism was the dominant driver. We found that the sum of drought and fire contributions to CO2 variability exceeded direct NEE responses to temperature in both the Northern and Southern Hemispheres. Additional sensitivity tests revealed that these contributions are masked by temporal and spatial smoothing of CO2 observations. Accounting for fires, the sensitivity of tropical NEE to temperature stress decreased by 25% to 2.9 ± 0.4 Pg C yr-1 K-1. These results underscore the need for accurate attribution of the drivers of CO2 variability prior to using contemporary observations to constrain long-term ESM responses.

Keppel-Aleks, Gretchen; Wolf, Aaron S.; Mu, Mingquan; Doney, Scott C.; Morton, Douglas C.; Kasibhatla, Prasad S.; Miller, John B.; Dlugokencky, Edward J.; Randerson, James T.

2014-11-01

133

Temporal variability of thermal refuges and water temperature patterns in an Atlantic salmon river  

NASA Astrophysics Data System (ADS)

River basins in northern latitudes are predicted to experience increased water temperatures under future climate change. This will have a negative impact on most salmonid populations which are highly intolerant of temperatures in excess of 23° C. In response to summer heat stress, salmonids thermoregulate in discrete units of cold water. Termed thermal refuges, these are of great significance to the ability of salmon and trout to survive increased water temperatures. Although previous research has documented links between the spatial patterns of thermal refuges and salmonid distribution and behaviour, the temporal variability of these cold water units has never been studied. In this investigation, airborne thermal infrared (TIR) imagery acquired six times between 2009 and 2011 was used to characterise temporal variability of thermal refuges and broader scale patterns of water temperature in the Rivière Ouelle, an Atlantic salmon river in Québec, Canada. Thermal refuges detected from TIR imagery were classified into a series of categories, revealing notable inter-survey variability between the absolute counts of each refuge type. Broader-scale longitudinal temperature profiles of river temperature were also extracted. Temporal variability in the absolute counts of lateral groundwater seeps (the most frequently observed thermal refuge class) was shown to correlate strongly with long duration hydrometeorological metrics such as seasonal mean discharge (R2 = 0.94, p < 0.01). Conversely, thermal refuges resulting from cold water tributaries were more temporally stable. Downstream temperature complexity was shown to correlate best with short duration metrics such as cumulative precipitation depth within a 5-day period prior to each survey (R2 = 0.90, p < 0.01). This study is the first of its kind to link thermal refuge dynamics and water temperature patterns to hydrometeorological conditions and may offer valuable insights into how changing hydrometeorological regimes could influence these important cold water units in the future.

Dugdale, S.; Bergeron, N.; St-Hilaire, A.

2013-12-01

134

Temperature control using variable conductance closed two-phase heat pipe  

Microsoft Academic Search

The concept of using variable conductance heat pipes (VCHP) for controlling the temperature of solar collectors is introduced. This closed system does not need any external force, is self-controllable and therefore ensures high reliability in thermal control. A copper\\/water heat pipe equipped with a cold reservoir and buffered with air as non-condensable gas (NCG) has been tested for temperatures from

Ioan Sauciuc; Aliakbar Akbarzadeh; Peter Johnson

1996-01-01

135

Interannual variability of wintertime temperature on the inner continental shelf of the Middle Atlantic Bight  

NASA Astrophysics Data System (ADS)

shallow depth of the inner continental shelf allows for rapid adjustment of the ocean to air-sea exchange of heat and momentum compared with offshore locations. Observations during 2001-2013 are used to evaluate the contributions of air-sea heat flux and oceanic advection to interannual variability of inner-shelf temperature in the Middle Atlantic Bight. Wintertime processes are important for interpreting regional interannual variability at nearshore locations since winter anomalies account for 69-77% of the variance of the annual anomalies and are correlated over broad along-shelf scales, from New England to North Carolina. At the Martha's Vineyard Coastal Observatory on the 12 m isobath, a heat budget is used to test the hypothesis that interannual differences in winter temperatures are due solely to air-sea heat flux. Bimonthly averages of air-sea heat flux are correlated with temporal changes in temperature, but overestimate the observed wintertime cooling. Velocity and satellite-derived temperature data show that interannual variability in wintertime surface cooling is partially compensated for by alongshore advection of warmer water from the west at this particular location. It is also shown that surface heat flux is a strong function of air-sea temperature difference. Because of this coupling between ocean and air temperatures in shallow water, along-shelf advection can significantly modify the surface heat flux at seasonal and interannual time scales. While along-shelf advection at relatively small (˜100 km) scales can be an important component of the heat budget over the inner shelf, interannual temperature variability is still largely determined by adjustment to large-scale air-temperature anomalies.

Connolly, Thomas P.; Lentz, Steven J.

2014-09-01

136

Investigation on multi-variable decoupled temperature control system for enamelling machine with heated air circulation  

SciTech Connect

A lots of problems may occur frequently when controlling the temperature of the enamelling machine oven in the real industrial process, such as multi-variable coupled problem. an experimental rig with triple inputs and triple outputs was devised and a simulation modeling was established accordingly in this study,. the temperature control system based on the feedforward compensation algorithm was proposed. Experimental results have shown that the system is of high efficiency, good stability and promising application.

Li, Yang; Qin, Le; Zou, Shipeng; Long, Shijun [School of Information Engineering, Guangdong University of Technology, Guangzhou, 510006 (China)

2014-04-11

137

2T/5T Two-Axis Cryogen Free Superconducting Vector Magnet With Variable Temperature Space  

NASA Astrophysics Data System (ADS)

A conduction cooled 2T / 5T superconducting vector magnetic system with a variable temperature space was developed and tested. The system is based on a commercial two-stage 4 K Gifford-McMahon cryocooler with the cooling power of 1.5 W at 4.2 K. The cool down time of the magnet from room temperature to 3.2 K is 17 hours. The system provides sample temperature range of 6.0-300 K. The clear diameter of variable temperature space is 39 mm. A 5 T solenoid generates magnetic field in the vertical axis and a 2 T split coil generates field in the horizontal axis. The magnets are made of niobium-titanium wire wound on a copper former. A PC controlled rotary drive is applied to rotate a sample holder around the vertical axis. Thus the measured sample can be exposed to the magnetic field in any desired direction. A helium gas gap heat switch is used as a controllable thermal link between the variable temperature space and the 2nd stage to avoid overheating of the magnet at high temperatures of the sample. The system design, manufacturing and test results are presented.

Demikhov, E. I.; Demikhov, T. E.; Kostrov, E. A.; Lysenko, V. V.; Piskunov, N. A.

2014-05-01

138

Sr/Ca as a Potential Proxy of Sub-surface Temperature Variability in C. secundum  

NASA Astrophysics Data System (ADS)

There is increasing interest in the development of proxy records of oceanographic variability from intermediate and deep-water environments using deep-sea corals. Recent work has focused on isotopic and elemental ratios as proxies for temperature with limited success. Here we explore the potential uses of Mg/Ca and Sr/Ca in the same Corallium secundum sample using LA-ICP-MS. C. secundum samples where collected from the Makapuu deep-sea coral off the coast of Hawaii at 400 m water depth. Both inter and intra sample reproducibility of several trace elements, including Mg, Sr, Cd, and Ba and any correlation to instrumental time series is explored. The most promising results are presented. Two ~70 year Sr/Ca time-series were developed using a laser ablation ICP-MS (LA-ICP-MS) system in continuous scanning mode with a 20x200 micron slit on C. secundum specimens collected at the same deep-sea coral bed. Both specimens have age models based on radiocarbon measurements. The time-series was compared to a ~35 year monthly averaged temperature record (WOD98 and GSTPP) from 400 meters. The LA-ICP-MS Sr/Ca data show a remarkable degree of correspondent variability over the most recent 35 years respectively to the sub surface temperature record at slightly greater than annual resolution. Water temperatures vary from 8.5 to 10°C while the Sr/Ca varies from 3.3 to 3.0 mmol/mol. Sub decadal variability of the temperature appears to match Sr/Ca variability reasonably well even when assuming a linear growth rate (170 µm/yr). Longer term (~25 year) cycles are evident in the 70 year LA-ICP-MS Sr/Ca time-series. These results suggest Sr/Ca measurements in C. secundum specimens may be a viable proxy of sub-surface temperature variability.

Roark, E.; Fallon, S. J.; Guilderson, T. P.; Dunbar, R. B.; McCulloch, M. T.

2009-12-01

139

A MERRA based analysis of the Climate Variability and Summer Temperature-Rainfall Relationships over India  

NASA Astrophysics Data System (ADS)

Using gridded monthly observation and reanalysis datasets (Modern Era Retrospective-analysis for Research and Applications - MERRA), we examine the variability, co-variability and lagged relationships between temperature and summer rainfall over India (1979 - 2005). The spatial and temporal patterns of temperature and rainfall anomalies are analyzed by computing the percentage of occurrences of positive anomalies for each gridpoint (spatial patterns of variability) and for all seasons throughout the study period (temporal patterns of variability). We found that a percentage of occurrences of positive temperature anomalies larger than 50% was observed for 63% of winters, but only 44% of summers. To investigate the relationships between the two variables, we use the Observations Minus Reanalysis (OMR) method to identify areas of interest (warming/cooling) and we look at rainfall patterns in such areas. We also analyze temperature patterns in areas where rainfall has increased (or decreased) over the study period. The results do not point to well defined rainfall patterns as a function of OMR, but show clearly the occurrence of the largest temperature increases (decreases) in areas where summer rainfall has decreased (increased). The lag correlations between summer rainfall and standardized temperature anomalies of previous months show that from January to April, negative correlations dominate: e.g. in January, up to -0.79 along the eastern coast; -0.75 in central India in March; up to -0.84 Rajasthan, Punjab and Madhya Pradesh. In May, positive correlations are predominant: up to 0.79 in northern and southern India. Strong relationships are limited, but provide guidance for local rainfall predictability.

Fall, S.; Niyogi, D.; Kishtawal, C. M.; Mishra, V.; Bosilovich, M. G.; Entin, J. K.

2010-12-01

140

Can local linear stochastic theory explain sea surface temperature and salinity variability?  

NASA Astrophysics Data System (ADS)

Sea surface temperature (SST) and salinity (SSS) time series from four ocean weather stations and data from an integration of the GFDL coupled ocean-atmosphere model are analyzed to test the applicability of local linear stochastic theory to the mixed-layer ocean. According to this theory, mixed-layer variability away from coasts and fronts can be explained as a `red noise' response to the `white noise' forcing by atmospheric disturbances. At one weather station, Papa (northeast Pacific), this stochastic theory can be applied to both salinity and temperature, explaining the relative redness of the SSS spectrum. Similar results hold for a model grid point adjacent to Papa, where the relationships between atmospheric energy and water fluxes and actual changes in SST and SSS are what is expected from local linear stochastic theory. At the other weather stations, this theory cannot adequately explain mixed-layer variability. Two oceanic processes must be taken into account: at Panulirus (near Bermuda), mososcale eddies enhance the observed variability at high frequencies. At Mike and India (North Atlantic), variations in SST and SSS advection, indicated by the coherence and equal persistence of SST and SSS anomalies, contribute to much of the low frequency variability in the model and observations. To achieve a global perspective, TOPEX altimeter data and model results are used to identify regions of the ocean where these mechanisms of variability are important. Where mesoscale eddies are as energetic as at Panulirus, indicated by the TOPEX global distribution of sea level variability, one would expect enhanced variability on short time scales. In regions exhibiting signatures of variability similar to Mike and India, variations in SST and SSS advection should dominate at low frequencies. According to the model, this mode of variability is found in the circumpolar ocean and the northern North Atlantic, where it is associated with the irregular oscillations of the model's thermohaline circulation.

Hall, A.; Manabe, S.

141

The variability of California summertime marine stratus: Impacts on surface air temperatures  

NASA Astrophysics Data System (ADS)

study investigates the variability of clouds, primarily marine stratus clouds, and how they are associated with surface temperature anomalies over California, especially along the coastal margin. We focus on the summer months of June to September when marine stratus are the dominant cloud type. Data used include satellite cloud reflectivity (cloud albedo) measurements, hourly surface observations of cloud cover and air temperature at coastal airports, and observed values of daily surface temperature at stations throughout California and Nevada. Much of the anomalous variability of summer clouds is organized over regional patterns that affect considerable portions of the coast, often extend hundreds of kilometers to the west and southwest over the North Pacific, and are bounded to the east by coastal mountains. The occurrence of marine stratus is positively correlated with both the strength and height of the thermal inversion that caps the marine boundary layer, with inversion base height being a key factor in determining their inland penetration. Cloud cover is strongly associated with surface temperature variations. In general, increased presence of cloud (higher cloud albedo) produces cooler daytime temperatures and warmer nighttime temperatures. Summer daytime temperature fluctuations associated with cloud cover variations typically exceed 1°C. The inversion-cloud albedo-temperature associations that occur at daily timescales are also found at seasonal timescales.

Iacobellis, Sam F.; Cayan, Daniel R.

2013-08-01

142

The variability of California summertime marine stratus: impacts on surface air temperatures  

USGS Publications Warehouse

This study investigates the variability of clouds, primarily marine stratus clouds, and how they are associated with surface temperature anomalies over California, especially along the coastal margin. We focus on the summer months of June to September when marine stratus are the dominant cloud type. Data used include satellite cloud reflectivity (cloud albedo) measurements, hourly surface observations of cloud cover and air temperature at coastal airports, and observed values of daily surface temperature at stations throughout California and Nevada. Much of the anomalous variability of summer clouds is organized over regional patterns that affect considerable portions of the coast, often extend hundreds of kilometers to the west and southwest over the North Pacific, and are bounded to the east by coastal mountains. The occurrence of marine stratus is positively correlated with both the strength and height of the thermal inversion that caps the marine boundary layer, with inversion base height being a key factor in determining their inland penetration. Cloud cover is strongly associated with surface temperature variations. In general, increased presence of cloud (higher cloud albedo) produces cooler daytime temperatures and warmer nighttime temperatures. Summer daytime temperature fluctuations associated with cloud cover variations typically exceed 1°C. The inversion-cloud albedo-temperature associations that occur at daily timescales are also found at seasonal timescales.

Iacobellis, Sam F.; Cayan, Daniel R.

2013-01-01

143

Solar flux variability of Mars' exosphere densities and temperatures Jeffrey M. Forbes,1  

E-print Network

Solar flux variability of Mars' exosphere densities and temperatures Jeffrey M. Forbes,1 Frank G, the response of Mars' exosphere to long-term solar change is established and compared to that of Earth conditions) change only 36­50% as much as those at Earth as solar activity increases from solar minimum

Forbes, Jeffrey

144

Multidecadal North Atlantic sea surface temperature and Atlantic meridional overturning circulation variability in CMIP5 historical  

E-print Network

variability of the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning CirculationMultidecadal North Atlantic sea surface temperature and Atlantic meridional overturning circulation and interact with each other. Citation: Zhang, L., and C. Wang (2013), Multidecadal North Atlantic sea surface

145

Long-term variability of air temperature in the Aral sea region  

NASA Astrophysics Data System (ADS)

The interannual and interdecadal variability of the air temperature in the Aral sea region at surface and at different isobaric levels is investigated using NCAR/NCEP reanalysis data, CARDS aerological data, data collected at the former USSR and the present Kazakhstan and Uzbekistan meteorological stations. Five groups of stations are identified in the study region using an objective classification algorithm. The reanalysis data for the Aral sea region are first validated against the observational data. The analysis reveals that during the pre-desiccation period, negative air temperature trends were dominant for all seasons except winter. In contrast, the desiccation period was mainly characterized by trends towards warming. The largest trend values corresponded to related winter, and the second largest with summer. The character of the long-term air temperature variability at different isobaric levels over the Aral sea region was essentially same as that of the larger spatial scale background variability. However, the southwestern part of the Aral sea region up to 700 mb exhibits statistically significant local anomalies possibly associated with the Aral sea desiccation. The wavelet analysis is used to investigate the frequency structure of the air temperature variability in the Aral sea region.

Khan, Valentina M.; Vilfand, Roman M.; Zavialov, Peter O.

2004-06-01

146

Associations of multi-decadal sea-surface temperature variability with US drought  

USGS Publications Warehouse

Recent research suggests a link between drought occurrence in the conterminous United States (US) and sea surface temperature (SST) variability in both the tropical Pacific and North Atlantic Oceans on decadal to multidecadal (D2M) time scales. Results show that the Atlantic Multidecadal Oscillation (AMO) is the most consistent indicator of D2M drought variability in the conterminous US during the 20th century, but during the 19th century the tropical Pacific is a more consistent indicator of D2 M drought. The interaction between El Nin??o-Southern Oscillation (ENSO) and the AMO explain a large part of the D2M drought variability in the conterminous US. More modeling studies are needed to reveal possible mechanisms linking low-frequency ENSO variability and the AMO with drought in the conterminous US. ?? 2007 Elsevier Ltd and INQUA.

McCabe, G.J.; Betancourt, J.L.; Gray, S.T.; Palecki, M.A.; Hidalgo, H.G.

2008-01-01

147

Connecting Atlantic temperature variability and biological cycling in two earth system models  

NASA Astrophysics Data System (ADS)

Connections between the interdecadal variability in North Atlantic temperatures and biological cycling have been widely hypothesized. However, it is unclear whether such connections are due to small changes in basin-averaged temperatures indicated by the Atlantic Multidecadal Oscillation (AMO) Index, or whether both biological cycling and the AMO index are causally linked to changes in the Atlantic Meridional Overturning Circulation (AMOC). We examine interdecadal variability in the annual and month-by-month diatom biomass in two Earth System Models with the same formulations of atmospheric, land, sea ice and ocean biogeochemical dynamics but different formulations of ocean physics and thus different AMOC structures and variability. In the isopycnal-layered ESM2G, strong interdecadal changes in surface salinity associated with changes in AMOC produce spatially heterogeneous variability in convection, nutrient supply and thus diatom biomass. These changes also produce changes in ice cover, shortwave absorption and temperature and hence the AMO Index. Off West Greenland, these changes are consistent with observed changes in fisheries and support climate as a causal driver. In the level-coordinate ESM2M, nutrient supply is much higher and interdecadal changes in diatom biomass are much smaller in amplitude and not strongly linked to the AMO index.

Gnanadesikan, Anand; Dunne, John P.; Msadek, Rym

2014-05-01

148

A 1400-Year Record of Sea-Surface Temperature Variability From the Northern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

A continuous, decadal-scale resolution sea-surface temperature (SST) record of the past 1400 years in the northern Gulf of Mexico (GOM) was constructed from a box core recovered from the Pigmy Basin. SST was calculated from Mg/Ca measurements on the white variety of the planktic foraminifer Globigerinoides ruber. Age control for box core PBBC-1 was based on seven AMS 14C dates, and extended to a zero-age core- top. Two multi-decadal intervals of sustained high Mg/Ca values indicate GOM SSTs were as warm or warmer than core-top SSTs between 1000 and 1400 yrs BP. Foraminiferal Mg/Ca values during the coolest interval of the Little Ice Age (ca. 250 yrs BP) indicate that SST was 2 - 2.5 °C below modern SST. The total amplitude of SST variability in the GOM over the past 1400 years is 2.5-3 °C. Four minima in the Mg/Ca record between 900 and 250 yrs BP correspond with the Maunder, Spörer, Wolf and Oort sunspot minima, suggesting a link between solar insolation and SST variability in the GOM. The amplitude of temperature variability observed in the Pigmy Basin record is consistent with other temperature proxy records from the western subtropical Atlantic, and the pattern of variability closely corresponds to the tree-ring based Northern Hemisphere reconstruction of Esper et al. (2002).

Richey, J. N.; Poore, R. Z.; Flower, B. P.; Quinn, T. M.

2006-12-01

149

Medieval Warm Period, Little Ice Age and 20th century temperature variability from Chesapeake Bay  

USGS Publications Warehouse

We present paleoclimate evidence for rapid (< 100 years) shifts of ??? 2-4??C in Chesapeake Bay (CB) temperature ???2100, 1600, 950, 650, 400 and 150 years before present (years BP) reconstructed from magnesium/calcium (Mg/Ca) paleothermometry. These include large temperature excursions during the Little Ice Age (???1400-1900 AD) and the Medieval Warm Period (???800-1300 AD) possibly related to changes in the strength of North Atlantic thermohaline circulation (THC). Evidence is presented for a long period of sustained regional and North Atlantic-wide warmth with low-amplitude temperature variability between ???450 and 1000 AD. In addition to centennial-scale temperature shifts, the existence of numerous temperature maxima between 2200 and 250 years BP (average ???70 years) suggests that multi-decadal processes typical of the North Atlantic Oscillation (NAO) are an inherent feature of late Holocene climate. However, late 19th and 20th century temperature extremes in Chesapeake Bay associated with NAO climate variability exceeded those of the prior 2000 years, including the interval 450-1000 AD, by 2-3??C, suggesting anomalous recent behavior of the climate system. ?? 2002 Elsevier Science B.V. All rights reserved.

Cronin, T. M.; Dwyer, G.S.; Kamiya, T.; Schwede, S.; Willard, D.A.

2003-01-01

150

Sensitivity of Soil Respiration to Variability in Soil Moisture and Temperature in a Humid Tropical Forest  

PubMed Central

Precipitation and temperature are important drivers of soil respiration. The role of moisture and temperature are generally explored at seasonal or inter-annual timescales; however, significant variability also occurs on hourly to daily time-scales. We used small (1.54 m2), throughfall exclusion shelters to evaluate the role soil moisture and temperature as temporal controls on soil CO2 efflux from a humid tropical forest in Puerto Rico. We measured hourly soil CO2 efflux, temperature and moisture in control and exclusion plots (n?=?6) for 6-months. The variance of each time series was analyzed using orthonormal wavelet transformation and Haar-wavelet coherence. We found strong negative coherence between soil moisture and soil respiration in control plots corresponding to a two-day periodicity. Across all plots, there was a significant parabolic relationship between soil moisture and soil CO2 efflux with peak soil respiration occurring at volumetric soil moisture of approximately 0.375 m3/m3. We additionally found a weak positive coherence between CO2 and temperature at longer time-scales and a significant positive relationship between soil temperature and CO2 efflux when the analysis was limited to the control plots. The coherence between CO2 and both temperature and soil moisture were reduced in exclusion plots. The reduced CO2 response to temperature in exclusion plots suggests that the positive effect of temperature on CO2 is constrained by soil moisture availability. PMID:24312508

Wood, Tana E.; Detto, Matteo; Silver, Whendee L.

2013-01-01

151

Interannual and interdecadal variability in 335 years of central England temperatures.  

PubMed

Understanding the natural variability of climate is important for predicting its near-term evolution. Models of the oceans' thermohaline and wind-driven circulation show low-frequency oscillations. Long instrumental records can help validate the oscillatory behavior of these models. Singular spectrum analysis applied to the 335-year-long central England temperature (CET) record has identified climate oscillations with interannual (7- to 8-year) and interdecadal (15- and 25-year) periods, probably related to the North Atlantic's wind-driven and thermohaline circulation, respectively. Statistical prediction of oscillatory variability shows CETs decreasing toward the end of this decade and rising again into the middle of the next. PMID:17832386

Plaut, G; Ghil, M; Vautard, R

1995-05-01

152

Stream temperature response to variable glacier coverage in coastal watersheds of northern southeast Alaska  

NASA Astrophysics Data System (ADS)

Glaciers in southeast Alaska are experiencing high rates of ice thinning and retreat. These ongoing changes in glacier volume are altering the proportion of streamflow derived from glacial runoff, which can be an important control on the thermal regime of streams in the region. We measured stream temperature continuously during the 2011 summer runoff season (May through October) in nine watersheds of southeast Alaska that provide spawning habitat for Pacific salmon. Six of the nine watersheds have glacier coverage ranging from 2 to 63%. Our goal was to determine how air temperature and watershed land cover, particularly glacier coverage, influence stream temperature across the seasonal hydrograph. Multiple linear regression identified mean watershed elevation, which is tied to glacier extent, and watershed lake coverage (%) as the strongest landscape controls on mean monthly stream temperature, with the weakest (May) and strongest (July) models explaining 86% and 97% of the temperature variability, respectively. Mean weekly stream temperature was significantly related to mean weekly air temperature in seven of the nine streams; however, the relationships were weak to non-significant in the streams dominated by glacial runoff. Peak summer stream temperatures occurred much earlier in the glacial streams (typically around late May) and glaciers also had a cooling effect on monthly mean stream temperature during the summer (July through September) equivalent to a decrease of 1.1°C for each 10% increase in glacier coverage. Streams with >30% glacier coverage demonstrated decreasing stream temperatures with rising summer air temperatures, while those with <30% glacier coverage exhibited summertime warming. The maximum weekly average temperature (MWAT, an index of thermal suitability for salmon species) in the six glacial streams was substantially below the lower threshold for optimum salmonid growth. This finding suggests that, while glaciers are important for moderating summer stream temperatures, future reductions in glacier runoff may actually improve the thermal suitability of some streams in northern southeast Alaska for salmon.

Hood, E. W.; Fellman, J. B.; Nagorski, S. A.; Vermilyea, A.; Pyare, S.; Scott, D.

2012-12-01

153

The role of temperature variability in stabilizing the mountain pine beetle-fungus mutualism.  

PubMed

As global climate patterns continue to change and extreme weather events become increasingly common, it is likely that many ecological interactions will be affected. One such interaction is the multipartite symbiosis that exists between the mountain pine beetle and two species of fungi, Grosmannia clavigera and Ophiostoma montium. In this mutualism, the fungi provide nutrition to the beetle, while the fungi benefit by being dispersed to new host trees. Multi-partite mutualisms are predicted to be unstable due to strong direct competition among symbionts or natural selection for superior over inferior mutualists. However, this mutualism has remained stable over long periods of evolutionary time. In this paper, we developed a temperature-based model for the spread of fungi within a tree and connected it to an existing model for mountain pine beetle development. Using this integrated model for fungal growth, we explored the possibility that temperature variability is a stabilizing mechanism for the mountain pine beetle-fungi mutualism. Of the three types of temperature variability we tested: intra-year, inter-year and variability due to transitioning between different thermal habitats (thermal migration), we found that thermal migration was the most robust stabilizing mechanism. Additionally, we found that the MPB attack density or spacing between fungal lesions also had a significant effect on the stability of the system. High attack densities or close lesion spacings also tended to stabilize the system, regardless of temperature. PMID:23791850

Addison, A L; Powell, J A; Six, D L; Moore, M; Bentz, B J

2013-10-21

154

Impact of the Dominant Large-scale Teleconnections on Winter Temperature Variability over East Asia  

NASA Technical Reports Server (NTRS)

Monthly mean geopotential height for the past 33 DJF seasons archived in Modern Era Retrospective analysis for Research and Applications reanalysis is decomposed into the large-scale teleconnection patterns to explain their impacts on winter temperature variability over East Asia. Following Arctic Oscillation (AO) that explains the largest variance, East Atlantic/West Russia (EA/WR), West Pacific (WP) and El Nino-Southern Oscillation (ENSO) are identified as the first four leading modes that significantly explain East Asian winter temperature variation. While the northern part of East Asia north of 50N is prevailed by AO and EA/WR impacts, temperature in the midlatitudes (30N-50N), which include Mongolia, northeastern China, Shandong area, Korea, and Japan, is influenced by combined effect of the four leading teleconnections. ENSO impact on average over 33 winters is relatively weaker than the impact of the other three teleconnections. WP impact, which has received less attention than ENSO in earlier studies, characterizes winter temperatures over Korea, Japan, and central to southern China region south of 30N mainly by advective process from the Pacific. Upper level wave activity fluxes reveal that, for the AO case, the height and circulation anomalies affecting midlatitude East Asian winter temperature is mainly located at higher latitudes north of East Asia. Distribution of the fluxes also explains that the stationary wave train associated with EA/WR propagates southeastward from the western Russia, affecting the East Asian winter temperature. Investigation on the impact of each teleconnection for the selected years reveals that the most dominant teleconnection over East Asia is not the same at all years, indicating a great deal of interannual variability. Comparison in temperature anomaly distributions between observation and temperature anomaly constructed using the combined effect of four leading teleconnections clearly show a reasonable consistency between them, demonstrating that the seasonal winter temperature distributions over East Asia are substantially explained by these four large-scale circulation impacts.

Lim, Young-Kwon; Kim, Hae-Dong

2013-01-01

155

On the design and implementation of a novel impedance chamber based variable temperature regulator at liquid helium temperatures.  

PubMed

A novel variable temperature regulator (VTR) based on the use of a fine impedance capillary to control the flow rate of cold helium gas into the VTR chamber is described. The capillary has a diameter of just 200 microm and the flow rate of cold helium gas through the capillary can be effectively controlled to the desired value by heating the capillary to a preset temperature and by controlling the pressure in the VTR chamber to a preset pressure using automated control circuits. Excellent temperature stability (about +/-1 mK at 10 K and +/-2 mK at 100 K) has been demonstrated in this setup with uniform rates of heating or cooling by an optimal choice of parameters. Compared to the more conventional VTR designs based on the use of mechanical long stem valves in the liquid helium reservoir to control the flow rate of liquid helium into the VTR chamber, and the use of a needle valve at the top of the cryostat to control the exchange gas pressure in the thermal isolation chamber, the present design enables temperature stability at any user desired temperature to be attained with uniform rates of cooling/heating with minimum consumption of liquid helium. The VTR has been successfully incorporated in the high field superconducting quantum interference device magnetometer setup developed in-house. It can also be incorporated in any low temperature physical property measurement system in which the temperature has to be varied in a controlled manner from 4.2 to 300 K and vice versa with uniform rates of heating and cooling. PMID:20441373

Nagendran, R; Thirumurugan, N; Chinnasamy, N; Janawadkar, M P; Sundar, C S

2010-04-01

156

Implications of solar irradiance variability upon long-term changes in the Earth's atmospheric temperatures  

NASA Technical Reports Server (NTRS)

From 1979 through 1987, it is believed that variability in the incoming solar energy played a significant role in changing the Earth's climate. Using high-precision spacecraft radiometric measurements, the incoming total solar irradiance (total amount of solar power per unit area) and the Earth's mean, global atmospheric temperatures were found to vary in phase with each other. The observed irradiance and temperature changes appeared to be correlated with the 11-year cycle of solar magnetic activity. During the period from 1979 through 1985, both the irradiance and temperature decreased. From 1985 to 1987, they increased. The irradiance changed approximately 0.1 percent, while the temperature varied as much as 0.6 C. During the 1979-1987 period, the temperatures were forecasted to rise linearly because of the anthropogenic build-up of carbon dioxide and the hypothesized 'global warming', 'greenhouse effect', scenarios. Contrary to these scenarios, the temperatures were found to vary in a periodic manner in phase with the solar irradiance changes. The observed correlations between irradiance and temperature variabilily suggest that the mean, global temperature of the Earth may decline between 1990 and 1997 as solar magnetic activity decreases.

Lee, Robert B., III

1992-01-01

157

Top-of-atmosphere radiative contribution to unforced decadal global temperature variability in climate models  

NASA Astrophysics Data System (ADS)

recent work has focused on unforced global mean surface air temperature (T) variability associated with the efficiency of heat transport into the deep ocean. Here the relationship between unforced variability in T and the Earth's top-of-atmosphere (TOA) energy balance is explored in preindustrial control runs of the Coupled Model Intercomparison Project Phase 5 multimodel ensemble. It is found that large decadal scale variations in T tend to be significantly enhanced by the net energy flux at the TOA. This indicates that unforced decadal variability in T is not only caused by a redistribution of heat within the climate system but can also be associated with unforced changes in the total amount of heat in the climate system. It is found that the net TOA radiation imbalances result mostly from changes in albedo associated with the Interdecadal Pacific Oscillation that temporarily counteracts the climate system's outgoing longwave (i.e., Stefan-Boltzmann) response to T change.

Brown, Patrick T.; Li, Wenhong; Li, Laifang; Ming, Yi

2014-07-01

158

The use of variable temperature and magic-angle sample spinning in studies of fulvic acids  

USGS Publications Warehouse

Intensity distortions and poor signal to noise in the cross-polarization magic-angle sample spinning NMR of fulvic acids were investigated and attributed to molecular mobility in these ostensibly "solid" materials. We have shown that inefficiencies in cross polarization can be overcome by lowering the sample temperature to about -60??C. These difficulties can be generalized to many other synthetic and natural products. The use of variable temperature and cross-polarization intensity as a function of contact time can yield valuable qualitative information which can aid in the characterization of many materials. ?? 1987.

Earl, W.L.; Wershaw, R.L.; Thorn, K.A.

1987-01-01

159

Sea Surface Temperature Variability along the Path of the Antarctic Circumpolar Current  

Microsoft Academic Search

The spatial and temporal distribution of sea surface temperature (SST) anomalies in the Antarctic Circumpolar Current (ACC) is investigated, using monthly data from the NCEP-NCAR Reanalysis for the period 1980-2004. Patterns of atmo- spheric forcing are identied in observations of sea level pressure and air-sea heat ux es. It is found that a signicant fraction of SST variability in the

Ariane Verdy; John Marshall; Arnaud Czaja

2006-01-01

160

Modality of semiannual to multidecadal oscillations in global sea surface temperature variability  

Microsoft Academic Search

Repeating the history of study on El Niño-Southern Oscillation (ENSO) in the 1980s, interdecadal oscillation (IDO) in climate variability is currently an area of active research and debate, following the recognition of its emerging significance in nature and science. In this work, a two-dimensional propagating modal extraction technique is applied to a reconstructed global monthly sea surface temperature (SST) data

Ge Chen; Baomin Shao; Yong Han; Jun Ma; Bertrand Chapron

2010-01-01

161

Comment on 'Variability of the far-infrared solar temperature minimum with the solar cycle'  

NASA Astrophysics Data System (ADS)

We compare the solar cycle variation of the full disk brightness temperature minimum in the far-infrared reported by Müller et al. (1980) to the variation found in the far-ultraviolet Tmin continuum. The far-ultraviolet observations suggest that the far-infrared variability should be nearer 9,-60 K than the value of 200 K reported by Müller et al. (1980), whose solar cycle variation is comparable to their measurement error.

Cook, J. W.; Brueckner, G. E.; Vanhoosier, M. E.

1980-12-01

162

Temperature variability in China in an ensemble simulation for the last 1,200 years  

Microsoft Academic Search

Regional temperature anomalies in China during 800–2005 ad in an ensemble simulation with the atmosphere–ocean general circulation model ECHAM5\\/MPIOM subject to anthropogenic and natural\\u000a forcings are compared to reconstructions. In a mutual assessment of three reconstructed data sets and two ensemble simulations\\u000a with different solar forcings, a reconstructed data set and a simulated ensemble for weak solar variability are selected

Dan Zhang; Richard Blender; Xiuhua Zhu; Klaus Fraedrich

2011-01-01

163

Can local linear stochastic theory explain sea surface temperature and salinity variability?  

Microsoft Academic Search

.  ?Sea surface temperature (SST) and salinity (SSS) time series from four ocean weather stations and data from an integration\\u000a of the GFDL coupled ocean-atmosphere model are analyzed to test the applicability of local linear stochastic theory to the\\u000a mixed-layer ocean. According to this theory, mixed-layer variability away from coasts and fronts can be explained as a ‘red\\u000a noise’ response to

A. Hall; S. Manabe

1997-01-01

164

Impact of atmospheric variability on validation of satellite-based temperature measurements  

NASA Astrophysics Data System (ADS)

Satellite validation is often based on straight forward comparison of satellite-based data with non-satellite based measurements. For functional reasons satellite and reference measurements do usually not correspond exactly in time and space. Dynamical effects in the atmosphere lead to temporal and spatial variability of atmospheric parameters (e.g. temperature). This causes considerable differences that do not necessarily hint to an incorrect satellite measurement, so called mistime and misdistance errors. In this paper, the natural variability of the atmosphere is studied on scales effecting validation measurements. The approach is applied to temperature data from the ERA-40 reanalysis as well as to radiosonde (SIGMA-1) and satellite-based (SABER) measurements. Mistime and misdistance errors are quantified in dependence of geographic position, altitude, season and the temporal and spatial mismatch. The results allow a quantitative estimation of the impact of natural variability on validation analyses. In general, values lie in the range of a few Kelvin (e.g. up to 5 K for 500 km misdistance or 6 h mistime in the stratosphere), which indicates considerable effects on validation results. The determined results also point out regions in the atmosphere where the impact of natural variability is in general relatively high (e.g. the winter stratosphere in mid-latitudes) or rather low (e.g. the lower summer stratosphere). Altitudes, which are characterized systematically by only small mismatch errors, are indicated at about 10 and 25 km, respectively. These quiet layers are of special interest for validation activities.

Wendt, Verena; Wüst, Sabine; Mlynczak, Martin G.; Russell, James M.; Yee, Jeng-Hwa; Bittner, Michael

2013-09-01

165

Elucidating the impact of temperature variability and extremes on cereal croplands through remote sensing.  

PubMed

Remote sensing-derived wheat crop yield-climate models were developed to highlight the impact of temperature variation during thermo-sensitive periods (anthesis and grain-filling; TSP) of wheat crop development. Specific questions addressed are: can the impact of temperature variation occurring during the TSP on wheat crop yield be detected using remote sensing data and what is the impact? Do crop critical temperature thresholds during TSP exist in real world cropping landscapes? These questions are tested in one of the world's major wheat breadbaskets of Punjab and Haryana, north-west India. Warming average minimum temperatures during the TSP had a greater negative impact on wheat crop yield than warming maximum temperatures. Warming minimum and maximum temperatures during the TSP explain a greater amount of variation in wheat crop yield than average growing season temperature. In complex real world cereal croplands there was a variable yield response to critical temperature threshold exceedance, specifically a more pronounced negative impact on wheat yield with increased warming events above 35 °C. The negative impact of warming increases with a later start-of-season suggesting earlier sowing can reduce wheat crop exposure harmful temperatures. However, even earlier sown wheat experienced temperature-induced yield losses, which, when viewed in the context of projected warming up to 2100 indicates adaptive responses should focus on increasing wheat tolerance to heat. This study shows it is possible to capture the impacts of temperature variation during the TSP on wheat crop yield in real world cropping landscapes using remote sensing data; this has important implications for monitoring the impact of climate change, variation and heat extremes on wheat croplands. PMID:24930864

Duncan, John M A; Dash, Jadunandan; Atkinson, Peter M

2014-06-13

166

Indian Ocean sea surface temperature variability and change since 1960s: forcing and process  

NASA Astrophysics Data System (ADS)

Indian Ocean sea surface temperature (SST) variability and change since 1960s are investigated using global coupled models,the Community Climate System Model version 3 (CCSM3) and parallel climate model (PCM). Results from the CCSM3 and a series of PCM experiments are analyzed in order to understand the roles played by internal variability, human-induced warming, and external forcing in causing the SST variations. To consolidate the model results, the simple Ocean model Data Assimilation (SODA) products are also analyzed. The results suggest that the SST in both the south and north Indian Ocean (IO) has an increasing trend. Overlying on this trend is decadal variability. Consistent with previous studies, the warming trend results mainly from the human-induced increased green house gases, which increase downward longwave fluxes. Interestingly, warming of the upper tropical and subtropical basins is accomanied by cooling in higher-latitudes in the Antarctic Circumpolar Current (ACC) region, which results from the reduced southward heat transports by weakened the subtropical cells (STCs). This colder, ACC water can enter the IO via deep layers in the south and then shoals upward to the thermocline layer in the tropical Indian Ocean, causing a distinct vertical structrure: with warming in the near surface and below the thermocline and cooling in the thermocline. The SST decadal variability, however, is caused primarily by external forcing, due to a combined effect of surface heat flux and lateral heat transport. Internal variability of the coupled system also plays a role.

Han, W.; Meehl, G. A.; Hu, A.

2005-12-01

167

Variability of maximum and mean average temperature across Libya (1945-2009)  

NASA Astrophysics Data System (ADS)

Spatial and temporal variability in daily maximum and mean average daily temperature, monthly maximum and mean average monthly temperature for nine coastal stations during the period 1956-2009 (54 years), and annual maximum and mean average temperature for coastal and inland stations for the period 1945-2009 (65 years) across Libya are analysed. During the period 1945-2009, significant increases in maximum temperature (0.017 °C/year) and mean average temperature (0.021 °C/year) are identified at most stations. Significantly, warming in annual maximum temperature (0.038 °C/year) and mean average annual temperatures (0.049 °C/year) are observed at almost all study stations during the last 32 years (1978-2009). The results show that Libya has witnessed a significant warming since the middle of the twentieth century, which will have a considerable impact on societies and the ecology of the North Africa region, if increases continue at current rates.

Ageena, I.; Macdonald, N.; Morse, A. P.

2014-08-01

168

Tree growth and inferred temperature variability at the North American Arctic treeline  

NASA Astrophysics Data System (ADS)

We present white spruce ( Picea glauca) tree-ring width and maximum latewood density chronologies for two latitudinal treeline sites in northern interior Canada: along the Coppermine River in the Northwest Territories (NWT); and in the Thelon River Sanctuary, Nunavut. These chronologies provide climate and tree growth information for these two remote locations, filling a sizeable gap in spatial coverage of proxy records used to reconstruct temperature variability for the Northern Hemisphere. They represent some of the longest high-resolution proxies available for northern North America, dating as far back as AD 1046 for Coppermine ring widths. These chronologies correlate significantly with hemispheric-scale annual temperature reconstructions for the past millennium. Density records from both sites show a positive relationship with warm-season temperature data since ˜ the mid-20th century, although this link is somewhat weaker in recent decades (since ˜ 1980). Both ring-width chronologies demonstrate even greater loss of temperature sensitivity, and in the Thelon ring-width series a sustained reduction in growth appears linked to increased drought stress in this recent period. Diminishing correlations with temperature are also found when the Thelon ring-width and climate data are prewhitened, indicating that any low frequency uncertainties in the instrumental or tree-ring data (e.g., artifacts from the standardization process) cannot entirely account for this result. Our findings therefore suggest a recent loss of temperature sensitivity at these northern treeline locations that varies with the parameter and site studied. These and other uncertainties in the tree-ring as well as instrumental data will need to be resolved in future efforts to relate northern tree-ring records to temperature variability on a range of spatial scales.

D'Arrigo, Rosanne; Jacoby, Gordon; Buckley, Brendan; Sakulich, John; Frank, David; Wilson, Rob; Curtis, Ashley; Anchukaitis, Kevin

2009-01-01

169

Surface ocean temperature variability in the southwest tropical Pacific since 1649 CE  

NASA Astrophysics Data System (ADS)

Understanding of natural climate variability in the tropical Pacific before the twentieth century is limited by a lack of high quality instrumental and paleoclimate records. We present 350 years of surface ocean temperature variability derived from highly reproducible strontium-to-calcium ratios (Sr/Ca) from coral colonies in the reef surrounding Amédée Island, New Caledonia (22°28.8'S, 166°27.9'E) for the interval from 1649 to 1999 CE. Our reconstruction includes two new multi-century coral Sr/Ca records coupled with previous records from this location in which we examine Sr/Ca variability between intracolony and intercolony records and assesses the errors associated with sampling, chronology, and temperature reconstruction. The reconstruction error for a monthly temperature record is greatest for a reconstruction based on a single core (0.95°C, 1?) and the least for a reconstruction with five intra- and intercolony cores (0.59°C, 1?). For interannual variability, the reconstruction error is reduced by ~33% by including an additional coral colony whereas the chronology error is reduced for reconstructions >250 years by including an additional core from the same colony. With respect to 1961-1990 CE, the interval between 1818-1889 CE is the coolest in the past 350 years (-0.48 ±0.05°C) and the interval from 1649-1697 CE is warmer (+0.18 ±0.06°C). Our reconstruction does not correspond to sunspot variations or Little Ice Age cooling observed in northern hemisphere reconstructions; however, we do find a 0.73°C warming trend from 1890 to 1999 CE (±0.0011°C year-1, 1?), which is similar to the warming trend that reported by the Intergovernmental Panel on Climate Change. Time-frequency analysis reveals decadal scale variations of 0.5 to 1.0°C from modulating interdecadal periodicities and persistent quasi-bidecadal periodicities before the 1900 CE, which are not coherent with previously recognized modes of Pacific decadal variability. Timing of the interdecadal variability corresponds to abnormally cold temperatures, some of which correspond to large explosive volcanic eruptions, whereas other cold events may be the result of localized upwelling induced by stronger trade winds related to shifts in the South Pacific gyre. Our results suggest different climate mode(s) are present in the southwest Pacific before the twentieth century.

DeLong, K. L.; Quinn, T. M.; Taylor, F. W.; Shen, C.; lin, K.

2011-12-01

170

Soil temperature and soil moisture induced spatio-temporal variability of soil respiration in winter wheat  

NASA Astrophysics Data System (ADS)

Soil respiration is the major transfer of CO2 from the soil to the atmosphere and is characterized by a high spatio-temporal variability depending, among others, on variations in soil temperature and soil moisture. We simultaneously measured soil respiration, soil temperature (3 cm depth) and soil moisture (0-5 cm depth) in winter wheat from April to September 2008 at a 50x50 m plot at a site near Jülich, Germany. The average soil respiration rate over the whole sampling period was 3.8 ±1.5 mol m-2 s-1. Spatial variations of soil respiration, represented by the coefficient of variation (CV), were in average more than 5 times higher than the spatial variations of soil temperature and soil moisture, respectively. Concerning soil respiration, considerably higher spatial variations were observed during the growth period of winter wheat. Semivariogram analysis revealed a strong spatial autocorrelation of soil temperature, whereas a moderate spatial autocorrelation of soil respiration and soil moisture was detected. However, the range of spatial autocorrelation was nearly similar for all three variables, on average 20 m. For the given temporal and spatial scale, a large proportion in temporal changing of the spatial structure of soil respiration could be explained by the spatial distribution of soil moisture.

Prolingheuer, N.; Herbst, M.; Graf, A.; Vanderborght, J.; Vereecken, H.

2009-04-01

171

Global-scale modes of surface temperature variability on interannual to century timescales  

NASA Technical Reports Server (NTRS)

Using 100 years of global temperature anomaly data, we have performed a singluar value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio-temporal modes of global climate variability. Statistical significance is determined from confidence limits obtained by Monte Carlo simulations. Secular variance is dominated by a globally coherent trend; with nearly all grid points warming in phase at varying amplitude. A smaller, but significant, share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude North Atlantic with a roughly centennial timescale. Spatial patterns associated with significant peaks in variance within a broad period range from 2.8 to 5.7 years exhibit characteristic El Nino-Southern Oscillation (ENSO) patterns. A recent transition to a regime of higher ENSO frequency is suggested by our analysis. An interdecadal mode in the 15-to-18 years period and a mode centered at 7-to-8 years period both exhibit predominantly a North Atlantic Oscillation (NAO) temperature pattern. A potentially significant decadal mode centered on 11-to-12 years period also exhibits an NAO temperature pattern and may be modulated by the century-scale North Atlantic variability.

Mann, Michael E.; Park, Jeffrey

1994-01-01

172

Temperature and acidification variability reduce physiological performance in the intertidal zone porcelain crab Petrolisthes cinctipes.  

PubMed

We show here that increased variability of temperature and pH synergistically negatively affects the energetics of intertidal zone crabs. Under future climate scenarios, coastal ecosystems are projected to have increased extremes of low tide-associated thermal stress and ocean acidification-associated low pH, the individual or interactive effects of which have yet to be determined. To characterize energetic consequences of exposure to increased variability of pH and temperature, we exposed porcelain crabs, Petrolisthes cinctipes, to conditions that simulated current and future intertidal zone thermal and pH environments. During the daily low tide, specimens were exposed to no, moderate or extreme heating, and during the daily high tide experienced no, moderate or extreme acidification. Respiration rate and cardiac thermal limits were assessed following 2.5 weeks of acclimation. Thermal variation had a larger overall effect than pH variation, though there was an interactive effect between the two environmental drivers. Under the most extreme temperature and pH combination, respiration rate decreased while heat tolerance increased, indicating a smaller overall aerobic energy budget (i.e. a reduced O2 consumption rate) of which a larger portion is devoted to basal maintenance (i.e. greater thermal tolerance indicating induction of the cellular stress response). These results suggest the potential for negative long-term ecological consequences for intertidal ectotherms exposed to increased extremes in pH and temperature due to reduced energy for behavior and reproduction. PMID:25392458

Paganini, Adam W; Miller, Nathan A; Stillman, Jonathon H

2014-11-15

173

Demonstration of a Variable Phase Turbine Power System for Low Temperature Geothermal Resources  

SciTech Connect

A variable phase turbine assembly will be designed and manufactured having a turbine, operable with transcritical, two-phase or vapor flow, and a generator – on the same shaft supported by process lubricated bearings. The assembly will be hermetically sealed and the generator cooled by the refrigerant. A compact plate-fin heat exchanger or tube and shell heat exchanger will be used to transfer heat from the geothermal fluid to the refrigerant. The demonstration turbine will be operated separately with two-phase flow and with vapor flow to demonstrate performance and applicability to the entire range of low temperature geothermal resources. The vapor leaving the turbine is condensed in a plate-fin refrigerant condenser. The heat exchanger, variable phase turbine assembly and condenser are all mounted on single skids to enable factory assembly and checkout and minimize installation costs. The system will be demonstrated using low temperature (237F) well flow from an existing large geothermal field. The net power generated, 1 megawatt, will be fed into the existing power system at the demonstration site. The system will demonstrate reliable generation of inexpensive power from low temperature resources. The system will be designed for mass manufacturing and factory assembly and should cost less than $1,200/kWe installed, when manufactured in large quantities. The estimated cost of power for 300F resources is predicted to be less than 5 cents/kWh. This should enable a substantial increase in power generated from low temperature geothermal resources.

Hays, Lance G

2014-07-07

174

Influence of cosmic-ray variability on the monsoon rainfall and temperature  

NASA Astrophysics Data System (ADS)

We study the role of galactic cosmic ray (GCR) variability in influencing the rainfall variability in Indian Summer Monsoon Rainfall (ISMR) season. We find that on an average during 'drought' (low ISMR) periods in India, GCR flux is decreasing, and during 'flood' (high ISMR) periods, GCR flux is increasing. The results of our analysis suggest for a possibility that the decreasing GCR flux during the summer monsoon season in India may suppress the rainfall. On the other hand, increasing GCR flux may enhance the rainfall. We suspect that in addition to real environmental conditions, significant levitation/dispersion of low clouds and hence reduced possibility of collision/coalescence to form raindrops suppresses the rainfall during decreasing GCR flux in monsoon season. On the other hand, enhanced collision/coalescence efficiency during increasing GCR flux due to electrical effects may contribute to enhancing the rainfall. Based on the observations, we put forward the idea that, under suitable environmental conditions, changing GCR flux may influence precipitation by suppressing/enhancing it, depending upon the decreasing/increasing nature of GCR flux variability during monsoon season in India, at least. We further note that the rainfall variability is inversely related to the temperature variation during ISMR season. We suggest an explanation, although speculative, how a decreasing/increasing GCR flux can influence the rainfall and the temperature. We speculate that the proposed hypothesis, based on the Indian climate data can be extended to whole tropical and sub-tropical belt, and that it may contribute to global temperature in a significant way. If correct, our hypothesis has important implication for the sun - climate link.

Badruddin; Aslam, O. P. M.

2015-01-01

175

Water transport in cement-in-polymer dispersions at variable temperature studied by magnetic resonance imaging  

SciTech Connect

The hydration of recently developed cement-in-polymer dispersions (c/p) containing 30% and 40% poly (vinyl acetate) [PVAc] and 30% poly(vinyl alcohol) [PVA] was monitored on-line at various temperatures using {sup 1}H Single Point Imaging (SPI). The physical changes undergone by the materials as well as the complex manner in which the absorption process takes place and the evolution of the spin density were characterized and were found to be strongly dependent on the nature and amount of polymer and on the temperature. Based on the results obtained we propose a simple mathematical model which can be used to characterize the behaviour of the c/p dispersions exposed to hydration at variable temperature.

Olaru, A.M., E-mail: aolaru@mc.rwth-aachen.de; Bluemich, B.; Adams, A., E-mail: aadams@mc.rwth-aachen.de

2013-02-15

176

Evidence for a weakening relationship between interannual temperature variability and northern vegetation activity  

NASA Astrophysics Data System (ADS)

Satellite-derived Normalized Difference Vegetation Index (NDVI), a proxy of vegetation productivity, is known to be correlated with temperature in northern ecosystems. This relationship, however, may change over time following alternations in other environmental factors. Here we show that above 30°N, the strength of the relationship between the interannual variability of growing season NDVI and temperature (partial correlation coefficient RNDVI-GT) declined substantially between 1982 and 2011. This decrease in RNDVI-GT is mainly observed in temperate and arctic ecosystems, and is also partly reproduced by process-based ecosystem model results. In the temperate ecosystem, the decrease in RNDVI-GT coincides with an increase in drought. In the arctic ecosystem, it may be related to a nonlinear response of photosynthesis to temperature, increase of hot extreme days and shrub expansion over grass-dominated tundra. Our results caution the use of results from interannual time scales to constrain the decadal response of plants to ongoing warming.

Piao, Shilong; Nan, Huijuan; Huntingford, Chris; Ciais, Philippe; Friedlingstein, Pierre; Sitch, Stephen; Peng, Shushi; Ahlström, Anders; Canadell, Josep G.; Cong, Nan; Levis, Sam; Levy, Peter E.; Liu, Lingli; Lomas, Mark R.; Mao, Jiafu; Myneni, Ranga B.; Peylin, Philippe; Poulter, Ben; Shi, Xiaoying; Yin, Guodong; Viovy, Nicolas; Wang, Tao; Wang, Xuhui; Zaehle, Soenke; Zeng, Ning; Zeng, Zhenzhong; Chen, Anping

2014-10-01

177

Variable-temperature cryogenic trap for the separation of gas mixtures  

NASA Technical Reports Server (NTRS)

The paper describes a continuous variable-temperature U-shaped cold trap which can both purify vacuum-line combustion products for subsequent stable isotopic analysis and isolate the methane and ethane constituents of natural gases. The canister containing the trap is submerged in liquid nitrogen, and, as the gas cools, the gas mixture components condense sequentially according to their relative vapor pressures. After the about 12 min required for the bottom of the trap to reach the liquid-nitrogen temperature, passage of electric current through the resistance wire wrapped around the tubing covering the U-trap permits distillation of successive gas components at optimal temperatures. Data on the separation achieved for two mixtures, the first being typical vacuum-line combustion products of geochemical samples such as rocks and the second being natural gas, are presented, and the thermal behavior and power consumption are reported.

Des Marais, D. J.

1978-01-01

178

Hydrologic and temperature variability at Lake Titicaca over the past 50,000 years  

NASA Astrophysics Data System (ADS)

The Bolivian Altiplano has been the focus of many paleoclimate studies due to the important role it plays in the South American climate system. Although the timing of climate shifts in this region is relatively well known, the magnitudes of hydrologic versus temperature changes remain poorly quantified. Here we apply hydrogen isotope analysis (?D) of terrestrial leaf waxes and the TEX86 temperature proxy in sediments from Lake Titicaca to reconstruct hydrologic and temperature variability over the past 50,000 years. Our record reveals that the Altiplano underwent a major climate shift during the last deglaciation, reflected in a ~70-80% enrichment in leaf wax ?D at the onset of the Holocene. Using the global isotope-temperature relationship for meteoric water, only 25-40% of this enrichment can be explained by the 4-5°C deglacial warming shown by the TEX86 proxy, indicating that precipitation was significantly reduced (and evaporation/evapotranspiration increased) during the Holocene. Further, the timing of these hydrologic and temperature changes was asynchronous during the transition from a cold and wet glacial state to a warm and dry Holocene. The major hydrologic shift recorded by leaf wax ?D occurred around ~11-12 ka, consistent with Northern Hemisphere deglacial patterns, whereas TEX86 data indicate that rapid warming began much earlier, more typical of a Southern Hemisphere deglacial pattern. Within the late glacial and Holocene mean climate states, however, there is evidence of synchronous hydrologic and temperature variability on millennial timescales. This study demonstrates that climate on the Altiplano was controlled by the interaction of local and remote forcing on a range of timescales.

Fornace, K.; Shanahan, T. M.; Sylva, S.; Ossolinski, J.; Baker, P. A.; Fritz, S. C.; Hughen, K. A.

2011-12-01

179

Testing of a Loop Heat Pipe Subjective to Variable Accelerations. Part 2; Temperature Stability  

NASA Technical Reports Server (NTRS)

The effect of accelerating forces on the performance of loop heat pipes (LHP) is of interest and importance to terrestrial and space applications. LHP's are being considered for cooling of military combat vehicles and for spinning spacecraft. In order to investigate the effect of an accelerating force on LHP operation, a miniature LHP was installed on a spin table. Variable accelerating forces were imposed on the LHP by spinning the table at different angular speeds. Several patterns of accelerating forces were applied, i.e. continuous spin at different speeds and periodic spin at different speeds and frequencies. The resulting accelerations ranged from 1.17 g's to 4.7 g's. This paper presents the second part of the experimental study, i.e. the effect of an accelerating force on the LHP operating temperature. It has been known that in stationary tests the LHP operating temperature is a function of the evaporator power and the condenser sink temperature when the compensation temperature is not actively controlled. Results of this test program indicate that any change in the accelerating force will result in a chance in the LHP operating temperature through its influence on the fluid distribution in the evaporator, condenser and compensation chamber. However, the effect is not universal, rather it is a function of other test conditions. A steady, constant acceleration may result in an increase or decrease of the operating temperature, while a periodic spin will lead to a quasi-steady operating temperature over a sufficient time interval. In addition, an accelerating force may lead to temperature hysteresis and changes in the temperature oscillation. In spite of all these effects, the LHP continued to operate without any problems in all tests.

Ku, Jentung; Ottenstein, Laura; Kaya, Taril; Rogers, Paul; Hoff, Craig

2000-01-01

180

Temperature and hydrologic variability of Lake Victoria, East Africa since the Late Pleistocene  

NASA Astrophysics Data System (ADS)

Recent organic geochemical advances have facilitated the comparison between continental temperature change and hydrologic variability. TEX86, a proxy based on the lipids of aquatic Crenarchaeota that show a positive correlation with growth temperature, was used to reconstruct surface water temperatures from Lake Victoria, East Africa during the latest Pleistocene-Holocene. Hydrologic conditions were interpreted using paleoecological implications of shifting pollen and diatom assemblages found in the lake (Kendall, 1969; Stager et al., 2003) and will be compared with future compound specific ?13C data from terrestrial biomarkers in order to determine the patterns of rainfall and aridity in this region. Initial comparisons of climatic changes seen in temperature and hydrologic records appear to show consistency between warm/wet intervals and cool/dry intervals that is often assumed, but more rarely shown, in tropical Africa. Lake Victoria temperatures show a steady warming beginning 16 cal ka, with a pause around the Younger Dryas, dominated by arid conditions and strong savannah grassland development during this interval. There is continued warming to a sustained thermal maximum for this portion of the record at ~10.5-8.5 ka, which generally coincides with the beginning of the Holocene Hypsithermal, an interval of elevated temperatures and precipitation throughout much of tropical Africa. This thermal maximum occurs during the most humid interval of this record (~9.5-8.3 ka), shown by an increase of humid forest pollen and high diatom abundance (due to increased water column mixing and nutrient runoff). Temperatures abruptly cool ~1.5°C in <800 years while precipitation becomes somewhat more seasonally restricted, coinciding with an abrupt drop in inferred P:E ratio and reduction in wind-driven mixing. The record then shows a general cooling, reaching a Holocene thermal minimum of ~18.4°C at ~4.5 ka, contrary to other East African continental and marine paleoclimate records that exhibit a Holocene thermal maximum ~5 ka. These coolest Holocene temperatures correspond to the driest interval in the surrounding region (~5.8-2.7 ka), with an increase in grassland abundance and decrease in humid forest pollen. Though a 5 ka thermal maximum is not seen in Lake Victoria, this portion of the record shows a temperature inflection and variable hydrologic signals, potentially marking a response to the end of the Holocene Hypsithermal, where temperatures begin to rise ~3°C over the remainder of the record.

Berke, M. A.; Johnson, T. C.; Werne, J. P.; Schouten, S.; Sinninghe Damste, J. S.

2010-12-01

181

Interannual variability of the Korea Strait Bottom Cold Water and its relationship with the upper water temperatures and atmospheric forcing in the Sea of Japan (East Sea)  

Microsoft Academic Search

A 35 yearlong temperature data set is analyzed to investigate the long-term temperature variability in the Korea Strait and its relationship with the temperature variability in the upper layer of the Sea of Japan (East Sea). The second cyclostationary empirical orthogonal function mode of the vertical temperature section in the Korea Strait describes the interannual variability of the Korea Strait

Hanna Na; Kwang-Yul Kim; Kyung-Il Chang; Kuh Kim; Jae-Yul Yun; Shoshiro Minobe

2010-01-01

182

Interannual and interdecadal variability in 335 years of central England temperatures  

SciTech Connect

Understanding the natural variability of climate is important for predicting its near-term evolution. Models of the oceans` thermohaline and wind-driven circulation show low-frequency oscillations. Long instrumental records can help validate the oscillatory behavior of these models. Singular spectrum analysis applied to the 335-year-long central England temperature (CET) record has identified climate oscillations with interannual (7- to 8-year) and interdecadal (15- and 25-year) periods, probably related to the North Atlantic`s wind-driven and thermohaline circulation, respectively. Statistical prediction of oscillatory variability shows CETs decreasing toward the end of this decade and rising again into the middle of the next. 42 refs., 4 figs.

Plaut, G. [Institut Non-Lineaire de Nice, Valbonne (France); Ghil, M. [Univ. of California, Los Angeles, CA (United States); Vautard, R. [Ecole Normale Superieure, Paris (France)

1995-05-05

183

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

SciTech Connect

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.

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

2009-01-01

184

An internal variable constitutive model for the large deformation of metals at high temperatures  

NASA Technical Reports Server (NTRS)

The advent of large deformation finite element methodologies is beginning to permit the numerical simulation of hot working processes whose design until recently has been based on prior industrial experience. Proper application of such finite element techniques requires realistic constitutive equations which more accurately model material behavior during hot working. A simple constitutive model for hot working is the single scalar internal variable model for isotropic thermal elastoplasticity proposed by Anand. The model is recalled and the specific scalar functions, for the equivalent plastic strain rate and the evolution equation for the internal variable, presented are slight modifications of those proposed by Anand. The modified functions are better able to represent high temperature material behavior. The monotonic constant true strain rate and strain rate jump compression experiments on a 2 percent silicon iron is briefly described. The model is implemented in the general purpose finite element program ABAQUS.

Brown, Stuart; Anand, Lallit

1988-01-01

185

North American west coast summer low cloudiness: Broadscale variability associated with sea surface temperature  

NASA Astrophysics Data System (ADS)

decades of observations at 20 coastal airports, from Alaska to southern California, reveal coherent interannual to interdecadal variation of coastal low cloudiness (CLC) from summer to summer over this broad region. The leading mode of CLC variability represents coherent variation, accounting for nearly 40% of the total CLC variance spanning 1950-2012. This leading mode and the majority of individual airports exhibit decreased low cloudiness from the earlier to the later part of the record. Exploring climatic controls on CLC, we identify North Pacific Sea Surface Temperature anomalies, largely in the form of the Pacific Decadal Oscillation (PDO) as well correlated with, and evidently helping to organize, the coherent patterns of summer coastal cloud variability. Links from the PDO to summer CLC appear a few months in advance of the summer. These associations hold up consistently in interannual and interdecadal frequencies.

Schwartz, Rachel E.; Gershunov, Alexander; Iacobellis, Sam F.; Cayan, Daniel R.

2014-05-01

186

A fast-scanning, low- and variable-temperature scanning tunneling microscope  

NASA Astrophysics Data System (ADS)

The design and performance of a fast-scanning, low- and variable-temperature, scanning tunneling microscope (STM) incorporated in an ultrahigh vacuum system is described. The sample temperature can be varied from 25 to 350 K by cooling the sample using a continuous flow He cryostat and counter heating by a W filament. The sample temperature can be changed tens of degrees on a time scale of minutes, and scanning is possible within minutes after a temperature change. By means of a software implemented active drift compensation the drift rate can be as low as 1 nm/day. The STM is rigid, very compact, and of low weight, and is attached firmly to the sample holder using a bayonet-type socket. Atomic resolution on clean metal surfaces can be achieved in the entire temperature range. The performance of the instrument is further demonstrated by images of adsorbed hexa-tert-butyl-decacyclene molecules on Cu(110), by STM movies, i.e., sequential STM images with a time resolution down to 1 s/image (100×100 Å2 with 256×256 pixels), of the mobility of these molecules, and finally by constant current images of standing waves in the electronic local density of states on Cu(110).

Petersen, L.; Schunack, M.; Schaefer, B.; Linderoth, T. R.; Rasmussen, P. B.; Sprunger, P. T.; Laegsgaard, E.; Stensgaard, I.; Besenbacher, F.

2001-02-01

187

Variable sensitivity of US maize yield to high temperatures across developmental stages  

NASA Astrophysics Data System (ADS)

The sensitivity of maize to high temperatures has been widely demonstrated. Furthermore, field work has indicated that reproductive development stages are particularly sensitive to stress, but this relationship has not been quantified across a wide geographic region. Here, the relationship between maize yield and temperature variations is examined as a function of developmental stage. US state-level data from the National Agriculture Statistics Service provide dates for six growing stages: planting, silking, doughing, dented, mature, and harvested. Temperatures that correspond to each developmental stage are then inferred from a network of weather station observations interpolated to the county level, and a multiple linear regression technique is employed to estimate the sensitivity of county yield outcomes to variations in growing-degree days and an analogous measure of high temperatures referred to as killing-degree days. Uncertainties in the transition times between county-level growth stages are accounted for. Results indicate that the silking and dented stages are generally the most sensitive to killing degree days, with silking the most sensitive stage in the US South and dented the most sensitive in the US North. These variable patterns of sensitivity aid in interpreting which weather events are of greatest significance to maize yields and provide some insight into how shifts in planting time or changes in developmental timing would influence the risks associated with exposure to high temperatures.

Butler, E. E.; Huybers, P. J.

2013-12-01

188

Past Temperature Variability Inferred from Tree-Ring Records for the Past Millennium  

NASA Astrophysics Data System (ADS)

Tree rings are an important proxy for inferring past temperature variability as they are precisely dated to the year and, especially for higher latitude and alpine treeline regions of the world, can be very sensitive to past changes in temperature on interannual to much lower frequency (centennial) time scales. Temperatures can be reconstructed from both ring widths and maximum latewood density time series, which are complementary parameters with different strengths and weaknesses. Hemispheric-scale temperature reconstructions based on such data are highly useful records for inferring temperature changes over the past millennium, as well as the past sensitivity of the Earth's climate system. One hundred years of tree-ring science have identified no real evidence that adverse climatic events can cause such severely cold conditions that no rings might form at any of the trees at a given site, resulting in misdating of the final chronology. Rather, based on both tree-ring observations and modeling analyses, there is clear evidence of precise dating and laying down of rings in at least some trees at each site even under extremely adverse cold conditions.

D'Arrigo, R.; Wilson, R.

2012-12-01

189

Using skin temperature variability to quantify surface and subsurface estuarine processes  

NASA Astrophysics Data System (ADS)

IR imagery is a unique tool to study nearshore processes. It not only provides a measure for surface skin temperature, but also permits the determination of surface currents. Variations in the skin temperature arise from disruption and renewal of the thermal boundary layer (TBL) as a result of wind forcing at the air-water interface, or due to turbulent eddies generated from below. The TBL plays a critical role in nearshore processes, in particular air-water heat and gas exchanges. It is essential to characterize the spatio-temporal scales of the disruption of the TBL and the extent to which it is renewed, as well as to understand how environmental factors relate to skin temperature variability. Furthermore, it is necessary to evaluate the ability not only to derive surface currents, but also to infer subsurface properties and processes from IR images. Estuarine and inlet environments such as the Hudson River are more complex, with multitude of additional processes at play, compared to the open ocean. For instance, the atmospheric boundary layer is complicated by the fact that that air is moving over both land and water, flow is fetch limited and there is orographic steering of winds. In addition, the subsurface turbulence is enhanced due to the bottom boundary layer. Here, high resolution IR imagery was collected from a ship stationed roughly 12 miles upstream of the New York Harbor in November 2010. On a nearby piling, several in situ instruments were mounted both above and below water, measuring environmental parameters such as wind speed, heat fluxes, air and water temperature, humidity as well as subsurface currents, turbulence, temperature and salinity. An IR imager installed on the cliff overlooking the river provided a complete view of the experiment area, with both the ship and the steel piling in its field of view. This study aims not only to characterize the skin temperature variability, but also to assess the validity of the various models for surface renewal found in the literature. Correlations between the measured skin temperature and environmental conditions (above and below surface) will give an insight on the physical processes governing surface temperatures. With the goal of determining subsurface flow characteristics from the surface flow statistics, three methods to derive surface velocity vectors are used. The results from the different techniques will be inter-compared and verified with in situ data in the aim to find the strengths and limitations of the various techniques. Further, relations between derived surface flow and measured subsurface flow will be investigated and the derived velocities will allow inferring turbulence statistics, in particular TKE dissipations rates.

Brumer, S. E.; Zappa, C. J.; Anderson, S. P.; Dugan, J. P.

2012-12-01

190

Solid-state variable-temperature NMR study of the phase separation of polybutadiene polyurethane zwitterionomers  

NASA Astrophysics Data System (ADS)

Polybutadiene polyurethane (PBDPU) zwitterionomers based on 4,4'-diphenylmethane diisocyanate (MDI), methyl-diethanolamine (MDEA), and hydroxy terminated polybutadiene are studied with variable-temperature (VT) wide-line 1H NMR. Spin—spin relaxation times ( T2) and spin—lattice relaxation times ( T1) are measured. It is found that phase separation of PBDPU does not change significantly upon ionization. The initial incorporation of ionization groups destroys the crystallinity of the hard segment while further ionization enhances physical crosslinks in the hard phase. The results are compared with a previous VT NMR study on polyether polyurethane zwitterionomers based on MDI, MDEA and 1000 Da molecular weight polytetramethylene oxide.

Yang, G.; Chen, Q.; Wang, Y.; Yang, C.; Wu, X.

1994-07-01

191

Effects of Variable Temperature on Mossbauer Data Acquisition: Laboratory-based and MER A Results  

NASA Technical Reports Server (NTRS)

Mossbauer spectrometers on the Spirit and Opportunity rovers have played a valuable role in identifying mineralogy at both the Gusev and Meridiani landing sites. Key to the application of Mossbauer results is the issue of how accurately the peak positions, on which the mineral identifications are based, can be determined. Remote Mossbauer spectroscopy has by necessity some unusual experimental constraints that may influence the confidence with which peak positions can be fit. We present here an analysis of the effects of variable temperature and short duration run times on spectral resolution.

Rothstein, Y.; Sklute, E. C.; Dyar, M. D.; Schaefer, M. W.

2005-01-01

192

Potential relation between equatorial sea surface temperatures and historic water level variability for Lake Turkana, Kenya  

NASA Astrophysics Data System (ADS)

Water level in Lake Turkana, Kenya in the past ca. 150 years is controlled primarily from the biannual passage of the East and West African Monsoon, with rainfall volume related partially to sea surface temperatures (SSTs) in the Western Indian and East Atlantic oceans. Empirical orthogonal function analyses show significant correlation between Eastern Atlantic or Western Indian SSTs and lake level anomalies, with the first mode accounting for 66% and 55% of the variability. The primary geographic loadings are consistent with a Gulf of Guinea moisture source and positive Indian Ocean Dipole (IOD) state. The second mode explains 10% of variability, and reflects the westward extension of an Indian Ocean cool pool, potentially indicative of a normal to a negative IOD state. There is significant spatial correlation between basin rainfall anomalies associated with Eastern Atlantic SSTs and a low in the continental divide between the Kenyan and the Ethiopian Highlands, which is a passage for moisture from the Congo Basin. Linear regression analysis with Bootstrap sampling and Monte Carlo simulations define numeric relations between Western Indian and Eastern Atlantic SSTs and lake level change for AD 1992-2013. The monthly and yearly lake level reconstructions based on this numeric analysis capture the decadal-scale variability and the 15 m drop in water level in the early 20th century. Meter-scale variability in lake level since ca. AD 1930 is associated with precipitation sourced from the Western Indian Ocean with IOD variability, whereas the 15 m drop in water level in the early 20th century may reflect a profound decrease in moisture from Atlantic/Congo Basin source. These numerical solutions are poised to reconstruct water level variations in the past ca. 300 years for Lake Turkana with new proxy records of SSTs from the Western Indian Ocean and the Gulf of Guinea.

Bloszies, Chris; Forman, Steven L.

2015-01-01

193

Conformational Analysis of (+)-Germacrene A by Variable Temperature NMR and NOE Spectroscopy  

PubMed Central

(+)-Germacrene A, an important intermediate in sesquiterpene biosynthesis, was isolated in pure form from a genetically engineered yeast and was characterized by chromatographic properties (TLC, GC), MS, optical rotation, UV, IR, 1H NMR and 13C NMR data. Variable-temperature 500 MHz 1H NMR spectra in CDCl3 showed that this flexible cyclodecadiene ring exists as three NMR-distinguishable conformational isomers in a ratio of about 5:3:2 at or below ordinary probe temperature (25° C). The conformer structures were assigned by 1H NMR data comparisons, NOE experiments, and vicinal couplings as follows: 1a (52%, UU), 1b (29% UD), and 1c (19%, DU). PMID:20617157

Faraldos, Juan A.; Wu, Shuiqin; Chappell, Joe

2009-01-01

194

Impact of Air Temperature and SST Variability on Cholera Incidence in Southeastern Africa, 1971-2006  

NASA Astrophysics Data System (ADS)

The most important climatic parameter related to cholera outbreaks is the temperature, especially of the water bodies and the aquatic environment. This factor governs the survival and growth of V. cholerae, since it has a direct influence on its abundance in the environment, or alternatively, through its indirect influence on other aquatic organisms to which the pathogen is found to attach. Thus, the potential for cholera outbreaks may rise, parallel to the increase in ocean surface temperature. Indeed, recent studies indicate that global warming might create a favorable environment for V. cholerae and increase its incidence in vulnerable areas. Africa is vulnerable to climate variability. According to the recent IPCC report on Africa, the air temperature has indicated a significant warming trend since the 1960s. In recent years, most of the research into disease vectors in Africa related to climate variability has focused on malaria. The IPCC indicated that the need exists to examine the vulnerabilities and impacts of climatic factors on cholera in Africa. In light of this, the study uses a Poisson Regression Model to analyze the possible association between the cholera rates in southeastern Africa and the annual variability of air temperature and sea surface temperature (SST) at regional and hemispheric scales, for the period 1971-2006. Data description is as follows: Number of cholera cases per year in Uganda, Kenya, Rwanda, Burundi, Tanzania, Malawi, Zambia and Mozambique. Source: WHO Global Health Atlas - cholera. Seasonal and annual temperature time series: Regional scale: a) Air temperature for southeastern Africa (30° E-36° E, 5° S-17° S), source: NOAA NCEP-NCAR; b) Sea surface temperature, for the western Indian Ocean (0-20° S, 40° E-45° E), source: NOAA, Kaplan SST dataset. Hemispheric scale (for the whole Southern Hemisphere): a) Air temperature anomaly; b) Sea surface temperature anomaly. Source: CRU, University of East Anglia. The following Poisson regression model is suggested: log{E(CHOLt)} = b0+b1×Xt+b2×Xt-1 where: CHOLt = the number of new cases of cholera in year t Xt / Xt-1 = the climate covariate measured in year t/t-1. (b0,b1) = the coefficients. A first order autocorrelation, AR1 = cor(Yt, Yt-1) is taken into account in the estimation using Generalized Estimating Equations. b1 and b2 quantify the association of CHOL and X, i.e. if Xt or Xt-1 increase by one unit, the mean of Yt is expected to increase in exp{b1} or exp{b2} times, respectively (multiplicative model). The results showed a significant exponential increase of cholera rates in humans during the study period, with an estimate of exp(b1)=1.08 (p-value = 0.02). Associations have been found between the annual increase of the air temperature in southeastern Africa and the cholera incidence in the same area. Linkages were found also for a wider scale, with the air temperature anomaly of the Southern Hemisphere, with an estimate of exp(b1)=1.18 (p-value = 0.04) and exp(b1)=1.26 (p-value = 0.006) for the previous year. Significant linkages were detected between the annual cholera rate and the annual western Indian Ocean' SST , with exp(b1) = 1.31 (p-value = 0.01) for the current year and exp(b1) = 1.23 (p-value = 0.05) for the previous year. Linkages were found also for the hemispheric scale, with the SST anomaly. The increase of global temperature may influence the temporal fluctuations of cholera, as well as potentially increasing the frequency and duration of its outbreaks. Despite future uncertainty, the climate variability has to be considered in predicting further cholera outbreaks in Africa. This may help to promote better, more efficient preparedness. For more details: Paz, S. 2010. Impact of Temperature Variability on Cholera Incidence in Southeastern Africa, 1971-2006. EcoHealth, in press.

Paz, Shlomit

2010-05-01

195

Response of tropical sea surface temperature, precipitation, and tropical cyclone-related variables to changes in global and local forcing  

E-print Network

A single-column model is used to estimate the equilibrium response of sea surface temperature (SST), precipitation, and several variables related to tropical cyclone (TC) activity to changes in both local and global forcing. ...

Sobel, Adam

196

Variability of mesopause temperature from the hydroxyl airglow observations over mid-latitudinal sites, Zvenigorod and Tory, Russia  

NASA Astrophysics Data System (ADS)

We obtained data on temperature in the mesopause vicinity from ground-based observations of the hydroxyl airglow at mid-latitudinal sites, Zvenigorod (56°N, 37°E), located near Moscow, over 2000-2012, and Tory (52°N, 103°E), Eastern Siberia, over 2008-2012. Seasonal behavior of the temperature and its monthly and nightly mean variances are presented. A comparison of the results obtained at two different regions of Russia shows higher values of the mesopause temperature variability in Eastern Siberia. We perform an analysis of the multi-year changes in the temperature variability characteristics based on the Zvenigorod observational data.

Perminov, V. I.; Semenov, A. I.; Medvedeva, I. V.; Zheleznov, Yu. A.

2014-12-01

197

Influence of Indian Ocean sea surface temperature variability on southwest Western Australian winter rainfall  

NASA Astrophysics Data System (ADS)

Southwest Western Australia (SWWA) has experienced a significant drop in winter rainfall during the past three decades, the cause of which is still subject to considerable speculation and debate. This prolonged drought has heavily impacted on water resources in the state, the predicted continuation of which is of major concern to the people of Western Australia. In this paper, the possible influence of sea surface temperature (SST) variability occurring over parts of the Indian Ocean on SWWA rainfall variability is explored. The results of our statistical analyses show that winter rainfall (May to October) in SWWA is lower in years when warm SSTs dominate the southern and tropical western Indian Ocean, compared to years when cool anomalies are present in the same region. In addition, a step change that can be detected in the SST anomalies in the southern and tropical western Indian Ocean occurring around 1970 happens to coincide with a similar sharp reduction in SWWA rainfall. It is suggested that the possible association between the Indian Ocean SST anomalies and observed variability of SWWA rainfall may be utilized, at a minimum, as possible diagnostic tools in the evaluation of global climate model outputs, in this way constraining the uncertainties in their predictions.

Samuel, Jos M.; Verdon, Danielle C.; Sivapalan, Murugesu; Franks, Stewart W.

2006-08-01

198

Joint spatiotemporal variability of global sea surface temperatures and global Palmer drought severity index values  

USGS Publications Warehouse

Dominant modes of individual and joint variability in global sea surface temperatures (SST) and global Palmer drought severity index (PDSI) values for the twentieth century are identified through a multivariate frequency domain singular value decomposition. This analysis indicates that a secular trend and variability related to the El Niño–Southern Oscillation (ENSO) are the dominant modes of variance shared among the global datasets. For the SST data the secular trend corresponds to a positive trend in Indian Ocean and South Atlantic SSTs, and a negative trend in North Pacific and North Atlantic SSTs. The ENSO reconstruction shows a strong signal in the tropical Pacific, North Pacific, and Indian Ocean regions. For the PDSI data, the secular trend reconstruction shows high amplitudes over central Africa including the Sahel, whereas the regions with strong ENSO amplitudes in PDSI are the southwestern and northwestern United States, South Africa, northeastern Brazil, central Africa, the Indian subcontinent, and Australia. An additional significant frequency, multidecadal variability, is identified for the Northern Hemisphere. This multidecadal frequency appears to be related to the Atlantic multidecadal oscillation (AMO). The multidecadal frequency is statistically significant in the Northern Hemisphere SST data, but is statistically nonsignificant in the PDSI data.

Apipattanavis, S.; McCabe, G.J.; Rajagopalan, B.; Gangopadhyay, S.

2009-01-01

199

Temperature Variability in the Stratosphere Obtained from 7 years of Vibrational-Raman- lidar Measurements  

NASA Astrophysics Data System (ADS)

The Purple Crow Lidar (PCL) is a large power-aperture product monostatic laser radar located at the Delaware Observatory (42° 52' N, 81° 23' W, 225 m elevation above sea level) near the campus of The University of Western Ontario. It is capable of measuring temperature and wave parameters from 10 to 110 km altitude, as well as water vapor in the troposphere and stratosphere. We use upper tropospheric and stratospheric vibrational Raman N2 backscatter-derived temperatures to form a climatology for the years 1999 to 2007 from 10 to 30 km altitude. The lidar temperatures are validated using coincident radiosondes measurements from Detroit and Buffalo. The measured temperatures show good agreement with the radiosonde soundings. An agreement of ±1 K is found during summer months and ±2.5 K during the winter months, validating the calibration of the lidar to within the geophysical variability of the measurements. Comparison between the PCL measurements and atmospheric models shows the PCL measurements are 5 K or less colder than CIRA-86 below 25 km and 2.5 K warmer above during the summer months. Below 16 km the PCL measurements are 5 K or less colder than the MSIS-90 model, while above this region, the PCL agrees to about ±3.5 K or less. The temperature differences between the PCL measurements and the models are consistent with the differences between the atmospheric models and the Detroit and Buffalo radiosonde measurements. The temperature differences compared to the models are consistent with previous comparisons between other radiosondes and satellite data sets, confirming that these differences with the models are real. We will highlight nights which show significant variations from the long-term averages, and when possible, the evolution of the variations.

Iserhienrhien, B.; Sica, R. J.; Argall, P. S.

2009-05-01

200

Assessing Low Frequency Variability in North Atlantic Ocean Sea Surface Temperatures in Global Climate Models  

NASA Astrophysics Data System (ADS)

The Atlantic Multidecadal Oscillation (AMO) is the leading mode of non-ENSO variability in the surface temperature of the Earth. The AMO mediates sea surface temperatures in the North Atlantic. Thus, its variability produces wavelike variations in the global surface temperature record and thereby alternately masks or amplifies the signal due to enhanced greenhouse gas or aerosol levels. Regionally, it affects the track and intensity of both extratropical cyclones throughout Europe and the Levant and severe tropical cyclones in the North Atlantic basin. See Enfield and Cid-Serrano [2009] for in-depth discussion. Therefore, even if there were no anthropogenic influence on the climate, understanding the dynamics of the AMO and being able to predict it would improve regional climate prediction throughout North America and Europe. In an era of anthropogenic climate change, it is vital that we understand the dynamics of the AMO: in part to predict the oscillations on the general positive trend in global surface temperature and in part because anthropogenic climate change could influence the dynamics and phenomenology of the AMO. Similar anthropogenic modification has been proposed for the El Nino-Southern Oscillation [e.g., Kim et al. 2009]. A small number of ocean and coupled atmosphere/ocean models simulate decadal or multidecadal variability in the North Atlantic, but the exact mechanisms involved vary from model to model. Therefore, characterizing North Atlantic variability on these timescales in a wide range of models opens a broad phase space to falsify mechanisms against a brief and sparse observational record. We have analyzed IPCC AR4 pre-industrial control runs from 23 global climate models (GCMs) in the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset, looking for global sea surface temperature (SST) drift (evidence of a disequilibrated ocean), and North Atlantic SST variability with a spatial pattern and periodicity consistent with instrumental and paleoclimatic records of the AMO. One GCM has been found to be both highly non-drifting and produce a multidecadal oscillation similar to the AMO. One drifting GCM also produces such an oscillation. We will present the full results of this analysis and preliminary results of more in-depth analysis of the “AMOs” simulated by these GCMs, focusing on the impact the processes that drive them could have on instrumental and paleoclimatic archives. D.B. Enfield and L. Cid-Serrano (2009), Secular and multidecadal warmings in the North Atlantic and their relationships with major hurricane activity, Int. J. Climatol., doi: 10.1002/joc.1881. H.-M. Kim, P.J. Webster, and J.A. Curry (2009), Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones, Science, 325, 77-80.

Heavens, N. G.; Liang, M.; Lin, L.; Li, K.; Tung, K. K.; Yung, Y. L.

2009-12-01

201

Modeling the day-to-day traffic evolution process after an unexpected network disruption  

E-print Network

after the collapse of I-35W Mississippi River Bridge in Minneapolis, Minnesota, we found that most and validated with the field data collected after the collapse of I-35W Bridge. This study bridges the gap of the I-35W Mississippi River Bridge in Minneapolis, Minnesota. From the traffic management's perspective

Levinson, David M.

202

Modeling Day-to-day Trip Choice Evolution under Network Disruption  

E-print Network

model using the data collected from the I-35W Bridge collapse in Minneapolis, Minnesota, and compare disruption scenarios. 1. Introduction The collapse of the Interstate 35W highway bridge over the Mississippi affected by the collapse in terms of fatalities, inju- ries, and loss of personal property, it is also

Levinson, David M.

203

Author's personal copy Modeling the day-to-day traffic evolution process after an unexpected  

E-print Network

the driving behavioral changes after the collapse of I-35W Mississippi River Bridge in Minneapolis, Minnesota model is calibrated and validated with the field data collected after the collapse of I-35W Bridge, such as the unexpected collapse of the I-35W Mississippi River Bridge in Minneapolis, Minnesota. From the traffic

Levinson, David M.

204

Accident prevention in day-to-day clinical radiation therapy practice.  

PubMed

Nearly 50-60% of cancer patients will undergo radiotherapy at some point in their treatment. Around 85% of the world's population live in developing countries served by approximately 30% of the world's radiotherapy facilities. It has been suggested that 1 megavoltage unit is required for every 500 new treatment courses per year, while others estimate that 1 megavoltage unit is needed for every 300 new treatments. However, these numbers do not necessarily take into account the development of new technologies and treatment modalities, which are more time- and resource-intensive. The International Commission on Radiological Protection has emphasised that 'purchasing new equipment without a concomitant effort on education and training and on a programme of quality assurance is dangerous', and 'the decision to implement a new technology for radiation therapy should be based on a thorough evaluation of the expected benefits, rather than being driven by the technology itself'. It is estimated that the rate of serious mistakes could be as high as 0.2%, which is several orders of magnitude higher than the rate reported for commercial aviation. So, how safe is safe? It can be stated that the development of a culture of safety is critical and requires efforts in education and training, which could prove difficult in overloaded departments. PMID:23089017

Baeza, M

2012-01-01

205

Retail redlining in New York City: racialized access to day-to-day retail resources.  

PubMed

Racial residential segregation is associated with health inequalities in the USA, and one of the primary mechanisms is through influencing features of the neighborhood physical environment. To better understand how Black residential segregation might contribute to health risk, we examined retail redlining; the inequitable distribution of retail resources across racially distinct areas. A combination of visual and analytic methods was used to investigate whether predominantly Black census block groups in New York City had poor access to retail stores important for health. After controlling for retail demand, median household income, population density, and subway ridership, percent Black was associated with longer travel distances to various retail industries. Our findings suggest that Black neighborhoods in New York City face retail redlining. Future research is needed to determine how retail redlining may perpetuate health disparities and socioeconomic disadvantage. PMID:22777683

Kwate, Naa Oyo A; Loh, Ji Meng; White, Kellee; Saldana, Nelson

2013-08-01

206

Loneliness and Cortisol: Momentary, Day-to-day, and Trait Associations  

PubMed Central

Summary In attempts to understand the social determinants of health, strong associations have been found between measures of loneliness, physiological stress processes, and physical and mental health outcomes. Feelings of loneliness are hypothesized to have implications for physiological stress processes, including activity of the hypothalamic-pituitary-adrenal (HPA) axis. In a community sample of young adults, multilevel modeling was used to examine whether trait and state feelings of loneliness were related to changes in levels of the stress-sensitive hormone cortisol, and whether the associations between loneliness and cortisol were mediated or moderated by the presence of concurrent depression or high levels of chronic life stress. Results indicated that trait loneliness was associated with a flattening of the diurnal cortisol rhythm. In addition, both daily and momentary state variations in loneliness were related to cortisol. Prior-day feelings of loneliness were associated with an increased cortisol awakening response the next morning and momentary experiences of loneliness during the day were associated with momentary increases in cortisol among youth who also had high chronic interpersonal stress. Results were significant after covarying current depression, both chronic and momentary reports of stress, and medical and lifestyle covariates. This study expanded on prior work by investigating and revealing three different time-courses of association between loneliness and HPA axis activity in young adults: trait, daily and momentary. PMID:19744794

Adam, Emma K.

2009-01-01

207

Spatio-Temporal Variability of the North Sea Cod Recruitment in Relation to Temperature and Zooplankton  

PubMed Central

The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability. PMID:24551103

Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

2014-01-01

208

Atmospheric controls on northeast Pacific temperature variability and change, 1900-2012.  

PubMed

Over the last century, northeast Pacific coastal sea surface temperatures (SSTs) and land-based surface air temperatures (SATs) display multidecadal variations associated with the Pacific Decadal Oscillation, in addition to a warming trend of ? 0.5-1 °C. Using independent records of sea-level pressure (SLP), SST, and SAT, this study investigates northeast (NE) Pacific coupled atmosphere-ocean variability from 1900 to 2012, with emphasis on the coastal areas around North America. We use a linear stochastic time series model to show that the SST evolution around the NE Pacific coast can be explained by a combination of regional atmospheric forcing and ocean persistence, accounting for 63% of nonseasonal monthly SST variance (r = 0.79) and 73% of variance in annual means (r = 0.86). We show that SLP reductions and related atmospheric forcing led to century-long warming around the NE Pacific margins, with the strongest trends observed from 1910-1920 to 1940. NE Pacific circulation changes are estimated to account for more than 80% of the 1900-2012 linear warming in coastal NE Pacific SST and US Pacific northwest (Washington, Oregon, and northern California) SAT. An ensemble of climate model simulations run under the same historical radiative forcings fails to reproduce the observed regional circulation trends. These results suggest that natural internally generated changes in atmospheric circulation were the primary cause of coastal NE Pacific warming from 1900 to 2012 and demonstrate more generally that regional mechanisms of interannual and multidecadal temperature variability can also extend to century time scales. PMID:25246555

Johnstone, James A; Mantua, Nathan J

2014-10-01

209

Variability of precipitation and temperature over the Greenland Ice Sheet and associated cyclone activity  

NASA Astrophysics Data System (ADS)

Greenland, with its steep coastal mountains and the big capacity of ice, plays an important role on the future climate. Particularly, the mass change of the Greenland Ice Sheet (GrIS) has potential contribution to the global sea level and to the thermohaline circulation. The GrIS is maintained by the mass balance between the accumulation from precipitation, ablation from evaporation/runoff, and dynamic thinning from ice discharge. This mass balance becomes a key to understand to what extent that the GrIS can impact the future climate. In our work, we'll mainly focus on the mechanism of leading to the changes of surface mass balance (balance between accumulation and ablation). Based on the daily and/or monthly in situ measurements of precipitation and air temperature from Danish Meteorological Institute (DMI) and downscaled model output from ECMWF (re)analysis, the variability of precipitation and temperature over the GrIS is investigated during the recent 50 years. Furthermore, based on the cyclones tracking technique, the number and intensity of the cyclones entered in Greenland area are addressed. It is found that cyclones are the main system to bring moisture and heat to the GrIS, and it has significant influence on precipitation and temperature in this area. In addition, this influence is depending on the temperature background. During the cooling period, cyclones have significant impact on the accumulation over the GrIS; during the warming period, cyclones are associated with changes of temperature over the GrIS.

Chen, L.; Johannessen, O. M.

2011-12-01

210

Assessment of the temperature variability at the snow-ground interface - concept and first results  

NASA Astrophysics Data System (ADS)

Bottom temperatures of the winter snow cover (BTS) represent the thermal conditions at the snow-ground interface and serve as a proxy for local permafrost ocurrence. The BTS method has been used in numerous studies to investigate local permafrost evidence and to validate larger scale permafrost distribution models. However, former studies have shown a relatively strong scattering between single measurements indicating that BTS values are sensitive to further factors. In order to identify the spatial and temporal variability and mentioned sources of irritation and to better understand their influence we applied repeated BTS measurements on a small scale test site situated below the Maurerkogel (2990 m) nearby the Kitzsteinhorn, Hohe Tauern Range, Austria. The site (c. 2000 m2) shows fairly homogenous surface conditions in terms of roughness and morphometry (bedrock with thin layer of fine-grained talus, slightly inclined to N). The measurement setup consists of a BTS grid with a minimum spacing of 5 m. Four campaigns with a total of 94 measurements were carried out from March 2012 to April 2013. Universal Temperature Logger (UTL), snow profiles and meteorological data from automatic weather stations are used to interpret the BTS values. The standard deviations of BTS values for each campaign range between 0.4 and 0.9 °C. The mean BTS value within the overall period is -3.1 °C. The near surface temperature logger shows a mean temperature of -3.7 °C in 10 cm depth covering four campaign days. Both, the correlation between near surface temperatures and BTS values as well as the low standard deviation between the BTS values demonstrate the applicability of the method under appropriate conditions.

Hiller, Clemens; Keuschnig, Markus; Hartmeyer, Ingo; Götz, Joachim

2014-05-01

211

Structural and vibrational dynamics of molecular solids under variable temperature and pressure  

NASA Astrophysics Data System (ADS)

An ultra-high resolution FTIR study (0.01cm-1) coupled with molecular simulations of para-terphenyl (PTP) under variable temperatures and pressures has been conducted in an effort to better understand the molecular dynamics (MD) of organic molecular crystals. PTP's use as an electrooptic material and as a host matrix for single molecular spectroscopy has created significant interest into the systems dynamics under variable conditions. Our high resolution study reveals many structure and dynamics changes in the PTP matrix as a result of changes in temperature and pressure. Further spectroscopic analysis using MD verifies these structural and dynamics alterations. Accurately modeled pressure and temperature phase transitions between the low-temperature low-pressure triclinic phase and the high-pressure high-temperature monoclinic phase of PTP was accomplished by a one-parameter optimization of the torsion potential component of the polymer consistent force field (PCFF) along with incorporation of COMPASS' (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) non-bond parameters. Initial MD simulations implementing the universal force field COMPASS could not adequately model the experimental crystal structure at 113K, nor could it reproduce the known transition temperature at ambient pressure or yield a well-defined transition pressure at low temperature. Therefore, we needed to create a new potential which was shown to reproduce the solid-solid phase transitions. The previously never simulated pressure induced solid-solid phase transition of PTP at low temperature (20K) and varying pressures (0-1GPa) was modeled. The symmetry based crystal/molecular rearrangement shows a compression and distortion of the unit cell and corresponding angles along with a flattening of the once twisted PTP molecules at high pressures (>0.5GPa). A fourth crystal phase (Phase IV) has been successfully identified through analysis of the individual molecule torsion angles, system energy deviations, and unit cell parameters. High-resolution IR spectroscopy (0.5cm-1) has been used to investigate the pressure-induced (0--11 kbar) polymorphic phase transition of PTP at low temperature (25 K). A number of doublet bands observed in low-pressure low temperature triclinic PTP were observed to coalesce in the high-pressure low temperature monoclinic phase. The band coalescing was attributed to changes in factor group (Davydov) splittings associated with the phase transition from a low-pressure triclinic phase to a high-pressure monoclinic phase. The vibrational spectra of (PTP) under extreme conditions (20K and 1,35GPa) has been characterized via molecular dynamics simulations. Both the high pressure low temperature pseudo monoclinic phase (HP-LT-PMP) and the low pressure high temperature monoclinic phase (LP-HT-MP) were used to investigate the vibrational spectra of PTP under high pressure and low temperature. It was shown that the LP-HT-MP was an excellent probe into the inter-molecular modes of the HP-LT-PMP and was quite suitable for the prediction of the HP-LT-PMP's intra-molecular modes. Further analysis of the vibrational spectra of PTP at low temperature as a function of pressure was completed showing that the frequency response as a function of pressure matched well with experiment for the phonon region. A detailed classification of all phonon and fundamental modes is also presented. Finally, an innovative experimental investigation into the homogeneous linewidths of PTP's fundamental modes under extreme pressures and temperatures is presented. Ultra high resolution FTIR (0.01 cm-1 resolution) was used to inspect PTP's intra-molecular vibrational relaxations under extreme temperatures (down to 27K) and pressures (up to 1.35GPa). We found that the low pressure phase's out-of-plane modes (<1000cm-1) relaxed faster at low temperatures (<150K) than those of the high pressure phase. Conversely, at high temperatures (>150K) the out-of-plane modes of the high pressure phase relaxed faster than those of the low

Schatschneider, Bohdan Hindulak

212

Evidence for a weakening relationship between interannual temperature variability and northern vegetation activity.  

PubMed

Satellite-derived Normalized Difference Vegetation Index (NDVI), a proxy of vegetation productivity, is known to be correlated with temperature in northern ecosystems. This relationship, however, may change over time following alternations in other environmental factors. Here we show that above 30°N, the strength of the relationship between the interannual variability of growing season NDVI and temperature (partial correlation coefficient RNDVI-GT) declined substantially between 1982 and 2011. This decrease in RNDVI-GT is mainly observed in temperate and arctic ecosystems, and is also partly reproduced by process-based ecosystem model results. In the temperate ecosystem, the decrease in RNDVI-GT coincides with an increase in drought. In the arctic ecosystem, it may be related to a nonlinear response of photosynthesis to temperature, increase of hot extreme days and shrub expansion over grass-dominated tundra. Our results caution the use of results from interannual time scales to constrain the decadal response of plants to ongoing warming. PMID:25318638

Piao, Shilong; Nan, Huijuan; Huntingford, Chris; Ciais, Philippe; Friedlingstein, Pierre; Sitch, Stephen; Peng, Shushi; Ahlström, Anders; Canadell, Josep G; Cong, Nan; Levis, Sam; Levy, Peter E; Liu, Lingli; Lomas, Mark R; Mao, Jiafu; Myneni, Ranga B; Peylin, Philippe; Poulter, Ben; Shi, Xiaoying; Yin, Guodong; Viovy, Nicolas; Wang, Tao; Wang, Xuhui; Zaehle, Soenke; Zeng, Ning; Zeng, Zhenzhong; Chen, Anping

2014-01-01

213

A versatile variable-temperature scanning tunneling microscope for molecular growth.  

PubMed

We describe and discuss the design of a variable-temperature scanning tunneling microscope (STM) system for the study of molecules at temperatures between 18 and 300 K in ultrahigh vacuum. The STM head is a refinement of a very rigid design developed and successfully operated in Hamburg. In the current version, the head is connected to a liquid helium flow cryostat, thereby reaching a base temperature of 18 K. To minimize the heat load on the STM head, a helium back flow cooled radiation shield is installed. The dimensions and the choice of materials are based on simulations of the heat dissipation. The STM is galvanically isolated from the vacuum chamber to minimize electronic noise and mechanically decoupled by means of springs and an eddy current damping stage. Additionally, the design of the STM head allows the deposition of several molecular materials onto the same cold sample surface. The operation of the STM in imaging mode is demonstrated for TPP/Cu(111) and FePCNaClCu(111). Spectroscopic capabilities of the system are shown for electronic states on NaClCu(111) and TPP/Cu(111). PMID:19044360

Kuck, Stefan; Wienhausen, Jan; Hoffmann, Germar; Wiesendanger, Roland

2008-08-01

214

Improved VAS regression soundings of mesoscale temperature structure observed during the 1982 atmospheric variability experiment  

NASA Technical Reports Server (NTRS)

An Atmospheric Variability Experiment (AVE) was conducted over the central U.S. in the spring of 1982, collecting radiosonde date to verify mesoscale soundings from the VISSR Atmospheric Sounder (VAS) on the GOES satellite. Previously published VAS/AVE comparisons for the 6 March 1982 case found that the satellite retrievals scarcely detected a low level temperature inversion or a mid-tropospheric cold pool over a special mesoscale radiosonde verification network in north central Texas. The previously published regression and physical retrieval algorithms did not fully utilize VAS' sensitivity to important subsynoptic thermal features. Therefore, the 6 March 1982 case was reprocessed adding two enhancements to the VAS regression retrieval algorithm: (1) the regression matrix was determined using AVE profile data obtained in the region at asynoptic times, and (2) more optimistic signal-to-noise statistical conditioning factors were applied to the VAS temperature sounding channels. The new VAS soundings resolve more of the low level temperature inversion and mid-level cold pool. Most of the improvements stems from the utilization of asynoptic radiosonde observations at NWS sites. This case suggests that VAS regression soundings may require a ground-based asynoptic profiler network to bridge the gap between the synoptic radiosonde network and the high resolution geosynchronous satellite observations during the day.

Chesters, Dennis; Keyser, Dennis A.; Larko, David E.; Uccellini, Louis W.

1987-01-01

215

Application of variable-metric chaos optimization neural network in predicting slab surface temperature of the continuous casting  

Microsoft Academic Search

A slab surface temperature prediction model of the continuous casting based on the variable-metric chaos optimization neural network is presented to solve the problem which the slab surface temperatures can not be measured continuously directly for plentiful inhalator, water film and ferric oxide on the slab surface in the secondary cooling zone. The model is shown to fit the actual

Fengxiang Gao; Changsong Wang; Yubao Zhang; Xiao Chen

2009-01-01

216

Using temperature modeling to investigate the temporal variability of riverbed hydraulic conductivity during storm events  

NASA Astrophysics Data System (ADS)

SummaryUnderstanding the impact of storm events on riverbed hydraulic conductivity is crucial in assessing the efficacy of riverbank filtration as a water-treatment option. In this study, the variability of riverbed hydraulic conductivity and its correlation to river stage during storm events was investigated. Water levels and temperatures were continuously monitored in the river using creek piezometers screened beneath the riverbed, and monitoring wells located on the river bank. The range of values for water levels during the study period was from 161.3 to 163.7 m AMSL while temperatures ranged from 3.75 °C to 24 °C. During the duration of the study the Great Miami River was losing water to the underlying aquifer due to pumping in the adjacent municipal well field. Flow and heat transport were simulated in a groundwater heat and flow program VSH2D to determine the hydraulic conductivity of the riverbed. Hydraulic conductivity was estimated by using it as a calibration parameter to match simulated temperatures to observed temperatures in a monitoring well. Hydraulic heads in the aquifer responded to storm events at the same times but with dampened amplitudes compared to the river stage. The relative responses resulted in increased head gradients during the rising limb of the stage-hydrograph. Heat-flow modeling during five storm events demonstrated that a rise in head gradient alone was not sufficient to produce the temperature changes observed in the wells. Simulated temperatures were fitted to the observed data by varying both river stage (as measured in the field) and riverbed hydraulic conductivity. To produce the best fit temperatures, riverbed hydraulic conductivity consistently needed to be increased during the rising and peak stages of the storm events. The increased conductivity probably corresponds to a loss of fine sediments due to scour during high river stage. Hydraulic conductivity increases during storm events varied from a factor of two (0.0951-0.2195 m/d) to almost one order of magnitude (0.0007-0.00658 m/d). Despite these predicted changes the highest model-predicted hydraulic conductivity value was 0.66 m/d, which is still much lower than the infiltration rate used in sand filtration systems (3.59 m/d). These low values suggest that storm events do not pose a significant risk to the water quality at this well field. There was a direct correlation between the duration of rising limb, rate of change of stage and maximum river stage and the magnitude of change of riverbed hydraulic conductivity.

Mutiti, Samuel; Levy, Jonathan

2010-07-01

217

NOM degradation during river infiltration: effects of the climate variables temperature and discharge.  

PubMed

Most peri-alpine shallow aquifers fed by rivers are oxic and the drinking water derived by riverbank filtration is generally of excellent quality. However, observations during past heat waves suggest that water quality may be affected by climate change due to effects on redox processes such as aerobic respiration, denitrification, reductive dissolution of manganese(III/IV)- and iron(III)(hydr)oxides that occur during river infiltration. To assess the dependence of these redox processes on the climate-related variables temperature and discharge, we performed periodic and targeted (summer and winter) field sampling campaigns at the Thur River, Switzerland, and laboratory column experiments simulating the field conditions. Typical summer and winter field conditions could be successfully simulated by the column experiments. Dissolved organic matter (DOM) was found not to be a major electron donor for aerobic respiration in summer and the DOM consumption did not reveal a significant correlation with temperature and discharge. It is hypothesized that under summer conditions, organic matter associated with the aquifer material (particulate organic matter, POM) is responsible for most of the consumption of dissolved oxygen (DO), which was the most important electron acceptor in both the field and the column system. For typical summer conditions at temperatures >20 °C, complete depletion of DO was observed in the column system and in a piezometer located only a few metres from the river. Both in the field system and the column experiments, nitrate acted as a redox buffer preventing the release of manganese(II) and iron(II). For periodic field observations over five years, DO consumption showed a pronounced temperature dependence (correlation coefficient r = 0.74) and therefore a seasonal pattern, which seemed to be mostly explained by the temperature dependence of the calculated POM consumption (r = 0.7). The river discharge was found to be highly and positively correlated with DO consumption (r = 0.85), suggesting an enhanced POM input during flood events. This high correlation could only be observed for the low-temperature range (T < 15 °C). For temperatures >15 °C, DO consumption was already high (almost complete) and the impact of discharge could not be resolved. Based on our results, we estimate the risk for similar river-infiltration systems to release manganese(II) and iron(II) to be low during future average summer conditions. However, long-lasting heat waves might lead to a consumption of the nitrate buffer, inducing a mobilization of manganese and iron. PMID:24064550

Diem, Samuel; Rudolf von Rohr, Matthias; Hering, Janet G; Kohler, Hans-Peter E; Schirmer, Mario; von Gunten, Urs

2013-11-01

218

Variable interval time/temperature (VITT) defrost-control-system evaluation  

SciTech Connect

Two variable-interval-time/temperature (VITT) heat pump defrost control systems are analyzed to determine if systems manufactured by Honeywell and Ranco qualify for credit for heat pumps with demand defrost control. The operation of the systems is described. VITT controls are not demand defrost control systems but utilize demand defrost control as backup systems in most Ranco models and all Honeywell models. The evaluations and results, intended to provide DOE information in making its determinations regarding credits for the control systems are discussed. The evaluation methodology utilizes a modified version of the Heat Pump Seasonal Performance Model (HPSPM) and the important modifications are discussed in Appendix A. Appendix B contains a detailed listing and discussion of the HPSPM output. (MCW)

None

1980-08-12

219

Ozone measurements from the NOAA-9 and the Nimbus-7 satellites: Implications of short and long term variabilities  

NASA Technical Reports Server (NTRS)

An overview is given of the measurements of total ozne and ozone profiles by the SBUV/2 instrument on the NOAA-9 spacecraft relative to similar measurements from the SBUV and TOMS instruments on Nimbus-7. It is shown that during the three year period from March 14, 1985, to February 28, 1988, when these data sets overlap, there have been significant changes in the calibrations of the three instruments which may be attributed to the drift of the NOSS-9 orbit to later equator crossing times (for SBUV/2). These changes in instrument characteristics have affected the absolute values of the trends derived from the three instruments, but their geophysical characteristics and response to short term variations are accurate and correlate well among the three instruments. For example, the total column ozone measured by the three instruments shows excellent agreement with respect to its day to day, seasonal, and latitudinal variabilities. At high latitudes, the day to day fluctuations in total ozone show a strong positive correlation with temperature in the lower stratosphere, as one might expect from the dynamical coupling of the two parameters at these latitudes.

Chandra, S.; Mcpeters, Richard D.; Hudson, R. D.; Planet, Walter G.

1990-01-01

220

Sea-surface Temperature Variability In The Eastern Vs Western Nordic Seas During The Past Millennium  

NASA Astrophysics Data System (ADS)

Sea-surface temperatures (SST) at decadal resolution have been reconstructed from core MD 95-2011 and core MD 99-2269 based on diatom transfer functions. The cores were collected during the IMAGES cruises of the R. V. Marion Dufresne. Core MD 95-2011 is located on the Vöring Plateau (66°58.18N; 07°38.36E, 1050 m water depth) along the main axis of the northward flowing warm Atlantic water. It is, therefore, in an ideal position to monitor changes in the northward heat flux to northwestern Europe. Core MD 99-2269 is located in the deep Hunafloi trough, off N Iceland (66°37.53N; 20°51.16W, 365 m water depth). Today the core lies under the influence of the Irminger current, but it also may be influenced by the cold East Greenland current as the Polar front migrates eastward. Core MD 95-2011 is dated by AMS C-14 and Pb 210 isotope profiles, and core MD 99-2269 by AMS C-14. Core MD 95-2011 has been studied at about 10-20 years resolution through the last 1000 years. Sea surface temperature variations are estimated by means of 3 different diatom transfer function methods. The records show SST variability of 1-2 degrees on timescales less than 100 years. There is clear evidence for late Holocene climatic events such as the «Little Ice Age» and the «Medieval Warm Period». The LIA starts in core MD 95-2011 with a SST fall of 1.5°C within a decade around 1400 AD and lasts until about 1750 AD. Core MD 99-2269 has been studied at about 4 years resolution. The record show SST variability of 3-4 degrees on timescales less than 100 years. Timing of late Holocene climatic events at the eastern versus western Nordic Seas will be discussed.

Koç, N.; Andersen, C.; Andrews, J.; Jennings, A.

221

Response of El Niño sea surface temperature variability to greenhouse warming  

NASA Astrophysics Data System (ADS)

The destructive environmental and socio-economic impacts of the El Niño/Southern Oscillation (ENSO) demand an improved understanding of how ENSO will change under future greenhouse warming. Robust projected changes in certain aspects of ENSO have been recently established. However, there is as yet no consensus on the change in the magnitude of the associated sea surface temperature (SST) variability, commonly used to represent ENSO amplitude, despite its strong effects on marine ecosystems and rainfall worldwide. Here we show that the response of ENSO SST amplitude is time-varying, with an increasing trend in ENSO amplitude before 2040, followed by a decreasing trend thereafter. We attribute the previous lack of consensus to an expectation that the trend in ENSO amplitude over the entire twenty-first century is unidirectional, and to unrealistic model dynamics of tropical Pacific SST variability. We examine these complex processes across 22 models in the Coupled Model Intercomparison Project phase 5 (CMIP5) database, forced under historical and greenhouse warming conditions. The nine most realistic models identified show a strong consensus on the time-varying response and reveal that the non-unidirectional behaviour is linked to a longitudinal difference in the surface warming rate across the Indo-Pacific basin. Our results carry important implications for climate projections and climate adaptation pathways.

Kim, Seon Tae; Cai, Wenju; Jin, Fei-Fei; Santoso, Agus; Wu, Lixin; Guilyardi, Eric; An, Soon-Il

2014-09-01

222

Orbital-scale summer precipitation and temperature variability in central China reconstructed with leaf wax hydrogen isotopes and branched GDGTs  

NASA Astrophysics Data System (ADS)

Reconstructions of monsoon variability on orbital time scales inform how the monsoon responds to large variations in forcing mechanisms (e.g., insolation, ice volume, greenhouse gases). The timing, or phase, of proxy response relative to forcing mechanisms (e.g., maximum insolation, maximum ice volume) can provide insights into which mechanisms control monsoon variability. Furthermore, obtaining summer monsoon records from different regions of Asia provides information about the spatial expression of monsoon variability. Deciphering which mechanisms control orbital-scale summer monsoon variability, however, requires reconstructions using proxies that respond mainly to summer monsoon variability. We present a 300-kyr-long, millennial-resolution record of Pleistocene summer monsoon precipitation variability on the Chinese Loess Plateau, generated using leaf wax hydrogen isotopes. The loess plateau receives ca. 50% of total annual precipitation during the summer monsoon, and plants produce leaf waxes during the warm, wet summer months. Thus, leaf wax hydrogen isotopes reflect summer precipitation isotopes. Precipitation isotopes change in response to changes in transport history (e.g. source water isotope ratios, transport path, etc.), which is influenced by changes in monsoon strength. Precipitation isotopes are also affected by local condensation temperature, which we account for using an independent temperature proxy, branched glycerol dialkyl glycerol tetraethers. We present these independent monsoon and temperature records and examine implications for mechanisms controlling monsoon variability in central China.

Thomas, E. K.; Clemens, S. C.; Prell, W. L.; Sun, Y.; Huang, Y.

2013-12-01

223

Spatial and temporal variability of soil temperature, moisture and surface soil properties  

NASA Technical Reports Server (NTRS)

The overall objectives of this research were to: (l) Relate in-situ measured soil-water content and temperature profiles to remotely sensed surface soil-water and temperature conditions; to model simultaneous heat and water movement for spatially and temporally changing soil conditions; (2) Determine the spatial and temporal variability of surface soil properties affecting emissivity, reflectance, and material and energy flux across the soil surface. This will include physical, chemical, and mineralogical characteristics of primary soil components and aggregate systems; and (3) Develop surface soil classes of naturally occurring and distributed soil property assemblages and group classes to be tested with respect to water content, emissivity and reflectivity. This document is a report of studies conducted during the period funded by NASA grants. The project was designed to be conducted over a five year period. Since funding was discontinued after three years, some of the research started was not completed. Additional publications are planned whenever funding can be obtained to finalize data analysis for both the arid and humid locations.

Hajek, B. F.; Dane, J. H.

1993-01-01

224

Ground and surface temperature variability for remote sensing of soil moisture in a heterogeneous landscape  

USGS Publications Warehouse

At the Little River Watershed (LRW) heterogeneous landscape near Tifton Georgia US an in situ network of stations operated by the US Department of Agriculture-Agriculture Research Service-Southeast Watershed Research Lab (USDA-ARS-SEWRL) was established in 2003 for the long term study of climatic and soil biophysical processes. To develop an accurate interpolation of the in situ readings that can be used to produce distributed representations of soil moisture (SM) and energy balances at the landscape scale for remote sensing studies, we studied (1) the temporal and spatial variations of ground temperature (GT) and infra red temperature (IRT) within 30 by 30 m plots around selected network stations; (2) the relationship between the readings from the eight 30 by 30 m plots and the point reading of the network stations for the variables SM, GT and IRT; and (3) the spatial and temporal variation of GT and IRT within agriculture landuses: grass, orchard, peanuts, cotton and bare soil in the surrounding landscape. The results showed high correlations between the station readings and the adjacent 30 by 30 m plot average value for SM; high seasonal independent variation in the GT and IRT behavior among the eight 30 by 30 m plots; and site specific, in-field homogeneity in each 30 by 30 m plot. We found statistical differences in the GT and IRT between the different landuses as well as high correlations between GT and IRT regardless of the landuse. Greater standard deviations for IRT than for GT (in the range of 2-4) were found within the 30 by 30 m, suggesting that when a single point reading for this variable is selected for the validation of either remote sensing data or water-energy models, errors may occur. The results confirmed that in this landscape homogeneous 30 by 30 m plots can be used as landscape spatial units for soil moisture and ground temperature studies. Under this landscape conditions small plots can account for local expressions of environmental processes, decreasing the errors and uncertainties in remote sensing estimates caused by landscape heterogeneity.

Giraldo, M.A.; Bosch, D.; Madden, M.; Usery, L.; Finn, M.

2009-01-01

225

Apparatus and Method for Measuring Air Temperature Ahead of an Aircraft for Controlling a Variable Inlet/Engine Assembly  

NASA Technical Reports Server (NTRS)

The apparatus and method employ remote sensing to measure the air temperature a sufficient distance ahead of the aircraft to allow time for a variable inlet/engine assembly to be reconfigured in response to the measured temperature, to avoid inlet unstart and/or engine compressor stall. In one embodiment, the apparatus of the invention has a remote sensor for measuring at least one air temperature ahead of the vehicle and an inlet control system for varying the inlet. The remote sensor determines a change in temperature value using at least one temperature measurement and prior temperature measurements corresponding to the location of the aircraft. The control system uses the change in air temperature value to vary the inlet configuration to maintain the position of the shock wave during the arrival of the measured air in the inlet. In one embodiment, the method of the invention includes measuring at least one air temperature ahead of the vehicle, determining an air temperature at the vehicle from prior air temperature measurements, determining a change in temperature value using the air temperature at the vehicle and the at least one air temperature measurement ahead of the vehicle, and using the change in temperature value to-reposition the airflow inlet, to cause the shock wave to maintain substantially the same position within the inlet as the airflow temperature changes within the inlet.

Gary, Bruce L. (Inventor)

2001-01-01

226

Variability of Sea Surface Temperature Response to Tropical Cyclones along the NEC Bifurcation Latitude  

NASA Astrophysics Data System (ADS)

The east of the Philippines serves as an entry point to an annual average of 20 tropical cyclones. The ocean is dynamic where the North Equatorial Current (NEC) bifurcates into the Kurushio Current to the north and Mindanao Current to the south. The displacement and intensity of NEC bifurcation in the region varies seasonally and interannually driven by local monsoons and ENSO. The variability of the NEC bifurcation latitude may alter the origins of the Kuroshio and modify the sea surface temperature field, which can alter the strength of the typhoons and upper ocean response. This paper aims to characterize the variability of Sea Surface Temperature (SST) Response to Tropical Cyclones along with the NEC Bifurcation latitude using daily merged product of the TRMM Microwave Imager (TMI) and Advanced Microwave Scanning Radiometer (AMSR-E), Sea Surface Height (SSH) and SSH Anomaly (SSHA) from AVISO and background climatological D26 (depth of 26 °C) and T100 (depth integrated temperature up to 100 meters) from ARGO profiles and CTD data from WOA09 from 2003 to 2012. SSH measurements from this period were used as a proxy for determining the bifurcation latitude (YB). Characteristics of the meridional distribution from 0° to 30°N of D26 is homogenous along 10-15°N. Monthly mean D26 along 10-15°N, 125-145°E shows high correlation with YB . Variations of the D26 and T100 showed deepening and warming along with YB. Two regions were derived from meridional distribution of T100 namely BSouth (<15°N) where background climatological condition is warm all throughout the year with deep D26 and BNorth (>15°N), where background climatological condition is shallow (D26) and varies seasonally. These regions where used to compare variability with respect to SST recovery time and the SST maximum change (?SSTmax) along with other factors such as TCs translation speed (TS) and intensity based on the Saffir-Simpson Hurricane Scale. Results showed that in both regions SST Recovery time is described as fast (<= 5day) when ?SSTmax is less than 1°C. Also, slow-moving TCs (TS < 4 m/s) is associated with maximum change in temperature and most often with longer Recovery time (>5days). Difference between both regions can be described with respect to the ?SSTmax. Higher ?SSTmax of up to 7°C was observed on BNorth which can be attributed to colder water (Temp < 26) brought up to surface given a shallow D26 layer. Moreover, the presence of cold-core eddies (SSHA <0) contributes to higher maximum cooling on the region. On the other hand, ?SSTmax is up to 4°C in BSouth associated with deeper D26 of >= 100m allowing only warm water (Temp>26) to be brought to the surface.

Fernandez, I.; Villanoy, C. L.

2013-12-01

227

Variability in precipitation, temperature and river runoff in W Central Asia during the past ~ 2000 yrs  

NASA Astrophysics Data System (ADS)

The tributary rivers Amu Darya and Syr Darya contribute major amounts of water to the hydrological budget of the endorheic Aral Sea. Processes controlling the flow of water into rivers in the headwater systems in Tien Shan (Kyrgyzstan) and Pamir (Tajikistan) are therefore most relevant. Lake water mineralization is strongly dependent on river discharge and has been inferred from spectrometrically determined gypsum and other salt contents. Comparison of high-resolution mineralization data with tree ring data, other proxies for tracing temperature and snow cover in NW China, and accumulation rates in the Guliya Ice Core indicate that mineralization over the past ~ 2000 yrs in the Aral Sea reflects snow cover variability and glacier extent in Tien Shan and Pamir (at the NW and W edges of the Tibetan Plateau). Snow cover in W Central Asia is preferentially a winter expression controlled by temperature patterns that impact the moisture-loading capacity over N Europe and NW Asia (Clark et al., 1999). We observed that the runoff, resulting from warmer winter temperatures in W Central Asia and resulting in a reduction of snow cover, decreased between AD 100-300, AD 1150-1250, AD 1380-1450, AD 1580-1680 and during several low frequency events after AD 1800. Furthermore, we observed a negative relationship between the amount of mineralization in the Aral Sea and SW summer monsoon intensity starting with the Little Ice Age. Based on these observations, we conclude that the lake level changes during the past ~ 2000 yrs were mostly climatically controlled. Around AD 200, AD 1400 and during the late 20th century AD, human activities (namely irrigation) may also have synergistically influenced discharge dynamics in the lower river courses.

Oberhänsli, Hedi; Novotná, Kate?ina; Píšková, Anna; Chabrillat, Sabine; Nourgaliev, Danis K.; Kurbaniyazov, Abilgazy K.; Matys Grygar, Tomáš

2011-03-01

228

Observed and SST-forced multidecadal variability in global land surface air temperature  

NASA Astrophysics Data System (ADS)

The characteristics of multidecadal variability (MDV) in global land surface air temperature (SAT) are analyzed based on observations. The role of sea surface temperature (SST) variations in generating MDV in land SAT is assessed using atmospheric general circulation model simulations forced by observed SST. MDV in land SAT exhibits regional differences, with amplitude larger than 0.3 °C mainly over North America, East Asia, Northern Eurasia, Northern Africa and Greenland for the study period of 1902-2004. MDV can account for more than 30 % of long-term temperature variation during the last century in most regions, especially more than 50 % in parts of the above-mentioned regions. The SST-forced simulations reproduce the observed feature of zonal mean MDV in land SAT, though with weaker amplitude especially at the northern high-latitudes. Two types of MDV in land SAT, one of 60-year-timescale, mainly observed in the northern mid-high-latitude lands, and another of 20-30-year-timescale, mainly observed in the low-latitude lands, are also well reproduced. The SST-forced MDV accounts for more than 40 % amplitude of observed MDV in most regions. Except for some sporadically distributed regions in central Eurasia, South America and Western Australia, the SST-forced multidecadal variations are well in-phase with observations. The Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation signals are found dominant in MDV of both the observed and SST-forced land SAT, suggesting important roles of these oceanic oscillations in generating MDV in global land SAT.

Gao, L. H.; Yan, Z. W.; Quan, X. W.

2014-03-01

229

Observed and SST-forced multidecadal variability in global land surface air temperature  

NASA Astrophysics Data System (ADS)

The characteristics of multidecadal variability (MDV) in global land surface air temperature (SAT) are analyzed based on observations. The role of sea surface temperature (SST) variations in generating MDV in land SAT is assessed using atmospheric general circulation model simulations forced by observed SST. MDV in land SAT exhibits regional differences, with amplitude larger than 0.3 °C mainly over North America, East Asia, Northern Eurasia, Northern Africa and Greenland for the study period of 1902-2004. MDV can account for more than 30 % of long-term temperature variation during the last century in most regions, especially more than 50 % in parts of the above-mentioned regions. The SST-forced simulations reproduce the observed feature of zonal mean MDV in land SAT, though with weaker amplitude especially at the northern high-latitudes. Two types of MDV in land SAT, one of 60-year-timescale, mainly observed in the northern mid-high-latitude lands, and another of 20-30-year-timescale, mainly observed in the low-latitude lands, are also well reproduced. The SST-forced MDV accounts for more than 40 % amplitude of observed MDV in most regions. Except for some sporadically distributed regions in central Eurasia, South America and Western Australia, the SST-forced multidecadal variations are well in-phase with observations. The Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation signals are found dominant in MDV of both the observed and SST-forced land SAT, suggesting important roles of these oceanic oscillations in generating MDV in global land SAT.

Gao, L. H.; Yan, Z. W.; Quan, X. W.

2015-01-01

230

Field study and simulation of diurnal temperature effects on infiltration and variably saturated flow beneath an ephemeral stream  

USGS Publications Warehouse

Two experiments were performed to investigate flow beneath an ephemeral stream and to estimate streambed infiltration rates. Discharge and stream-area measurements were used to determine infiltration rates. Stream and subsurface temperatures were used to interpret subsurface flow through variably saturated sediments beneath the stream. Spatial variations in subsurface temperatures suggest that flow beneath the streambed is dependent on the orientation of the stream in the canyon and the layering of the sediments. Streamflow and infiltration rates vary diurnally: Stream flow is lowest in late afternoon when stream temperature is greatest and highest in early morning when stream temperature is least. The lower afternoon streamflow is attributed to increased infiltration rates; evapotranspiration is insufficient to account for the decreased streamflow. The increased infiltration rates are attributed to viscosity effects on hydraulic conductivity from increased stream temperatures. The first set of field data was used to calibrate a two-dimensional variably saturated flow model that includes heat transport. The model was calibrated to (1) temperature fluctuations in the subsurface and (2) infiltration rates determined from measured stream flow losses. The second set of field data was to evaluate the ability to predict infiltration rates on the basis of temperature measurements alone. Results indicate that the variably saturated subsurface flow depends on downcanyon layering of the sediments. They also support the field observations in indicating that diurnal changes in infiltration can be explained by temperature dependence of hydraulic conductivity. Over the range of temperatures and flows monitored, diurnal stream temperature changes can be used to estimate streambed infiltration rates. It is often impractical to maintain equipment for determining infiltration rates by traditional means; however, once a model is calibrated using both infiltration and temperature data, only relatively inexpensive temperature monitoring can later yield infiltration rates that are within the correct order of magnitude.

Ronan, A.D.; Prudic, D.E.; Thodal, C.E.; Constantz, J.

1998-01-01

231

Variability of sea surface temperatures and sea ice in Baffin Bay during the last two millennia  

NASA Astrophysics Data System (ADS)

The Arctic region has undergone very rapid changes in the past 50 years. Climate models predict accelerating rates of change in the Arctic and long-term perspectives on natural climate variability are therefore needed to understand these changes and their further effects. We used marine fossil diatom assemblages from Baffin Bay to investigate August sea surface temperatures (aSSTs) and sea ice variability during the last two millennia. The Baffin Bay area is sensitive to changes in the climate system due to its location, where it is influenced by Atlantic and Arctic water masses. The top most 77 cm of a 600 cm long marine sediment core (GeoTü SL-170) was used for a high resolution study of quantitative SST and sea ice reconstructions based on fossil marine planktonic diatoms. A calibration dataset consisting of 155 surface samples from the North Atlantic and a new set of 24 surface samples from Baffin Bay with 52 diatom species was utilized to convert diatom counts to aSSTs using the weighted averaging partial least squares (WA-PLS) transfer function method. The sea ice reconstruction was based on a qualitative method for specific diatom assemblages and quantitative sea ice reconstructions for the May sea ice cover based on the Maximum likelihood (ML) transfer function method. The age model for the core is based on the 14C method. Our data shows a slight warming trend of the surface waters in Baffin Bay for the last ca. 2 kyr. The most dominating diatom species is Thalassiosira gravida spores, which represents typical "Baffin Current assemblage". The highest aSSTs occurred during the Medieval Warm Period (MWP), presumably due to the increased advection of warm Atlantic water from the West Greenland Current into Baffin Bay. After the MWP, the sediment was poor in diatoms during the Little Ice Age (LIA) suggesting that the study area was covered by sea ice also in the summertime.

Oksman, Mimmi; Miettinen, Arto; Kucera, Michal

2013-04-01

232

Satellite Observed Variability in Antarctic and Arctic Surface Temperatures and Their Correlation to Open Water Areas  

NASA Technical Reports Server (NTRS)

Recent studies using meterological station data have indicated that global surface air temperature has been increasing at a rate of 0.05 K/decade. Using the same set of data but for stations in the Antarctic and Arctic regions (>50 N) only, the increases in temperature were 0.08, and 0.22 K/decade, when record lengths of 100 and 50 years, respectively, were used. To gain insights into the increasing rate of warming, satellite infrared and passive microwave observations over the Arctic region during the last 20 years were processed and analyzed. The results show that during this period, the ice extent in the Antarctic has been increasing at the rate of 1.2% per decade while the surface temperature has been decreasing at about 0.08 K per decade. Conversely, in the Northern Hemisphere, the ice extent has been decreasing at a rate of 2.8% per decade, while the surface temperatures have been increasing at the rate of 0.38 K per decade. In the Antarctic, it is surprising that there is a short term trend of cooling during a global period of warming. Very large anomalies in open water areas in the Arctic were observed especially in the western region, that includes the Beaufort Sea, where the observed open water area was about 1x10(exp 6) sq km, about twice the average for the region, during the summer of 1998. In the eastern region, that includes the Laptev Sea, the area of open water was also abnormally large in the summer of 1995. Note that globally, the warmest and second warmest years in this century, were 1998 and 1995, respectively. The data, however, show large spatial variability with the open water area distribution showing a cyclic periodicity of about ten years, which is akin to the North Atlantic and Arctic Oscillations. This was observed in both western and eastern regions but with the phase of one lagging the other by about two years. This makes it difficult to interpret what the trends really mean. But although the record length of satellite data is still relatively short and the climate trend difficult to establish, the immediate impact of a continued warming trend may be very profound.

Comiso, Josefino C.; Zukor, Dorothy (Technical Monitor)

2000-01-01

233

Climate Variability in the Stratosphere during the 20th Century  

NASA Astrophysics Data System (ADS)

The stratosphere exhibits chemical and dynamical variability on different time scales, ranging from day-to-day variability to interdecadal variability and trends. Volcanic eruptions, solar variability, ozone depletion, or El Niño Southern Oscillation (ENSO), affect both troposphere and stratosphere, and it is an open question to what extent the climate effect proceeds via the stratosphere. The current data records as well as model simulations addressing stratospheric chemical climate variability mostly cover the past few decades only, which often is not sufficient to address interannual-to-decadal variability. Here we present results of transient simulations with the chemistry-climate model (CCM) SOCOL, spanning the whole 20th century. SOCOL is a combination of the middle atmosphere version of ECHAM4 (MPI, Hamburg) and the chemistry-transport model MEZON (PMOD/WRC, Davos). The simulations are carried out in ensemble-mode (9 members) prescribing sea surface temperature, sea ice distribution, volcanic aerosols, solar variability, greenhouse gases, ozone depleting substances, land surface changes, and quasi-biennial oscillation. The model's performance in reproducing key dynamical and chemical characteristics is validated against various observational and (prior to 1957) reconstructed upper air datasets. It is shown that the amount of internal variability can be a dominating source of year-to-year variations. A multiple linear regression model was applied to zonally averaged fields in order to extract the contributions of different boundary conditions to the modeled variability. The ENSO signal in the northern hemispheric winter shows a deceleration of the zonal flow at high latitudes accompanied by an increase of vertically propagating planetary waves. In the presentation this signal is further compared to idealized model experiments simulating extreme phases of ENSO.

Fischer, A.; Brönnimann, S.; Rozanov, E.; Schraner, M.

2009-09-01

234

Variable temperature film and contact resistance measurements on operating n-channel organic thin film transistors  

NASA Astrophysics Data System (ADS)

We report structural and electrical properties in thin films of an n-channel organic semiconductor, N,N'-dipentyl-3,4,9,10-perylene tetracarboxylic dimide (PTCDI-C5). The structure of polycrystalline thin films of PTCDI-C5 was studied using x-ray diffraction and atomic force microscopy. Films order with single crystal-like packing, and the direction of ?-? overlap is in the substrate plane. Organic thin film transistors (OTFTs) based on PTCDI-C5 were fabricated on hydrophobic and hydrophilic substrates. OTFTs showed effective mobility as high as 0.1 cm2/V s. Contact resistance of operating OTFTs was studied using resistance versus length plots and a four-probe method for three different contact metals (Au, Ag, Ca). Typical OTFTs had a specific contact resistance of 8×104 ? cm at high gate voltage. There was no dependence of contact resistance with contact metal. Variable temperature measurements revealed that film resistance in the OTFT was activated in the temperature range 100-300 K, with typical activation energies of 60-80 meV. Contact resistance showed similar activated behavior, implying that the Schottky barrier at the contact is not the limiting resistance for the contact. Film resistance data showed a Meyer-Neldel relationship with characteristic energy EMN=20-25 meV, for various samples. The common TFT instability of threshold voltage shift (TVS) was observed in PTCDI-C5 OTFTs. A model is proposed to explain positive TVS in gate bias stress and oxygen exposure experiments. The model is based on the formation of a metastable complex between PTCDI-C5 and oxygen, which creates a deep acceptor-like trap state.

Chesterfield, Reid J.; McKeen, John C.; Newman, Christopher R.; Frisbie, C. Daniel; Ewbank, Paul C.; Mann, Kent R.; Miller, Larry L.

2004-06-01

235

The variability of winter high temperature extremes in Romania and its relationship with large-scale atmospheric circulation  

NASA Astrophysics Data System (ADS)

The frequency variability of extreme high winter temperature as recorded at 85 meteorological stations from Romania during 1962-2010 period and its relationship with large-scale atmospheric circulation was investigated. An Empirical Orthogonal Function analysis reveals that large part of the extreme temperature frequency variability is common to all stations suggesting a strong influence of large-scale circulation anomalies. The North Atlantic Oscillation, West Pacific, East Atlantic, and Scandinavian patterns are related with extreme temperature frequency variability. We show that the East Atlantic Oscillation controls a significant part of interannual extreme high temperature variability over Romania via advection of warm air from the west. In addition, a strong relationship between blocking activity and frequency of extreme high temperature events in Romania was found. High blocking activity in the (20°W-70°E) sector is related with relatively strong advection of cold air over the country during winter. On the other hand, low blocking activity in the same sector is related with weak advection of relatively cold air in the region. Moreover, the blocking frequency in this sector is modulated mainly by the East Atlantic Oscillation.

Rimbu, N.; Stefan, S.; Necula, C.

2014-07-01

236

7. Atomic Force Microscopy Studies of Semicrystalline Polymers at Variable Temperature  

NASA Astrophysics Data System (ADS)

The capabilities of Atomic Force Microscopy, AFM, in studies of polymer phase transitions and, more generally, the semicrystalline polymer morphology are described. It is shown how variable temperature AFM can provide unique information on the organization of semicrystalline polymers at the nanometer scale and its evolution in the course of crystallization. The practical examples selected for this work illustrate applications of AFM to structural studies of homopolymers and polymer blends crystallized in the bulk, in thin films and in solutions. The investigated systems include solution grown single crystals of polyethylene, cold-crystallized poly(ether ether ketone), as well as melt-crystallized poly(ethylene terephthalate), poly(trimethylene terephthalate), syndiotactic polystyrene, poly(varepsilon -caprolactone), isotactic and syndiotactic polypropylene. The issues related to AFM image analysis and its quantitative comparison with the results of complementary techniques such as small-angle X-ray scattering (SAXS) are addressed. More specifically, it is shown how AFM can provide statistically meaningful parameters for the semicrystalline structure and an accurate choice of a structural model for the interpretation of SAXS data.

Ivanov, D. A.; Magonov, S. N.

237

Time Variability of the Global Temperature Distribution of Mimas and Janus  

NASA Astrophysics Data System (ADS)

Strong surface interaction of the inner Saturnian moon, Mimas, with energetic ions and MeV electrons has led to space weathering effect illustrated by albedo/color asymmetry and variation of the thermal inertia (I) between the leading and trailing hemisphere. The I value in a localized region of the leading hemisphere is about 67×30 J m^(-2) K^(-1) s^(1/2), while the corresponding value in the neighboring area is I<16 J m^(-2) K^(-1) s^(1/2) (Howett et al.,2011)[1]. We simulate the diurnal and seasonal variability of Mimas' global temperature distribution and examine the resultant effect on the possible formation of a surface bounded exosphere. Similar consideration is given to Janus which is the innermost icy of Saturn by taking into account its three-dimensional shape configuration. [1] Howett, C.J.A., J.R. Spencer, P. Schenk, R.E. Johnson, C. Paranicas, T.A. Hurford, A. Verbiscer, and M. Segura (2011), A high-amplitude thermal inertia anomaly of probable magnetospheric origin on Saturn's moon Mimas. Icarus, Volume 216, Issue 1, Pages 221-226.

Tu, L.; Ip, W.

2013-12-01

238

The bi-variate frequency distribution of two concurrent climatic variables: a study of temperature and dew point  

E-print Network

of the requirements for the degree of MASTER OF SCIENCE December 1991 Major Subject: Meteorology THE BI-VARIATE FREQUENCY DISTRIBUTION OF TWO CONCURRENT CLIMATIC VARIABLES: A STUDY OF TEMPERATURE AND DEW POINT A Thesis by JON WILLIAM ZEITLER Approved... Study of Temperature and Dew Point (December 1991). Jon William Zeitler, B. S. , iowa State University Chair of Advisory Comminee; Prof. John F. Griffiths The bi-variate normal distribution was fitted for the mid-season months of January, April, July...

Zeitler, Jon William

1991-01-01

239

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. PMID:22833269

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

240

Multidecadal North Atlantic Sea Surface Temperature and Atlantic Meridional2 Overturning Circulation Variability in CMIP5 Historical Simulations3  

E-print Network

26 #12;1 Abstract27 28 In this paper, simulated variability of the Atlantic Multidecadal Oscillation1 Multidecadal North Atlantic Sea Surface Temperature and Atlantic Meridional2 Overturning the delayed36 advective oscillation proposed for the AMOC on multidecadal timescales. A speed up (slow37 down

241

Multidecadal Ocean Temperature and Salinity Variability in the Tropical North Atlantic: Linking with the AMO, AMOC, and Subtropical Cell  

E-print Network

received 1 October 2012, in final form 14 February 2013) ABSTRACT The Atlantic multidecadal oscillation multidecadal oscillation (AMO), which is a basinwide mode in the entire North Atlantic and is definedMultidecadal Ocean Temperature and Salinity Variability in the Tropical North Atlantic: Linking

Wang, Chunzai

242

Paleoclimate proxy perspective on Caribbean climate since the year 1751: Evidence of cooler temperatures and multidecadal variability  

E-print Network

Atlantic Variabil- ity (TAV), and the North Atlantic Oscillation (NAO)/Arctic Oscillation system [Marshall temperatures and multidecadal variability K. H. Kilbourne,1 T. M. Quinn,2,3 R. Webb,4 T. Guilderson,5,6 J at centennial time scales. A strong multidecadal salinity signal in the oxygen isotope data correlates

South Florida, University of

243

Using Variable Temperature Powder X-Ray Diffraction to Determine the Thermal Expansion Coefficient of Solid MgO  

ERIC Educational Resources Information Center

A laboratory exercise was developed by using variable temperature powder X-ray diffraction (XRD) to determine [alpha] for MgO (periclase)and was tested in the Applied Physical Chemistry and Materials Characterization Laboratories at James Madison University. The experiment which was originally designed to provide undergraduate students with a…

Corsepius, Nicholas C.; DeVore, Thomas C.; Reisner, Barbara A.; Warnaar, Deborah L.

2007-01-01

244

Variable-temperature 13C solid-state NMR study of the molecular structure of honeybee wax and silk.  

PubMed

To elucidate the native-state crystal structure of beeswax from the Japanese bee, Apis cerana japonica, we determined the relationship between temperature and the 13C solid-state nuclear magnetic resonance (NMR) chemical shift of methylene carbon of beeswax, with comparison to n-alkanes and polyethylene in the orthorhombic, monoclinic, or triclinic crystal form. Variable-temperature 13C solid-state NMR observations of n-alkanes and polyethylene revealed that the chemical shifts of methylene carbon in the orthorhombic crystal form increased linearly with increasing temperature, that of the triclinic form decreased, and that of the monoclinic form was unaltered. These relations were compared with results of variable-temperature 13C solid-state NMR observation of beeswax. Results clarified that the two crystal forms comprising the beeswax in the native state are orthorhombic and monoclinic. The variable-temperature 13C solid-state NMR observations were also applied to interpret the differential scanning calorimetry (DSC) curve of beeswax. They were used to clarify the structural changes of beeswax for widely various temperatures. For beeswax secreted by the Japanese bee, the transition from the orthorhombic form to the rotator phase occurred at 36 degrees C, that is from the crystalline to the intermediate state at 45 degrees C. Moreover, the variable-temperature 13C solid-state NMR spectrum of honeybee silk in the native state was observed. Results demonstrated that the secondary structures of honeybee silk proteins in the native state comprised coexisting alpha-helix and beta-sheet conformations and that the amount of alpha-helices was greater. The alpha-helix content of honeybee silk was compared with that of hornet silk produced by Vespa larvae. PMID:19007807

Kameda, Tsunenori; Tamada, Yasushi

2009-01-01

245

Patterns in Temporal Variability of Temperature, Oxygen and pH along an Environmental Gradient in a Coral Reef  

PubMed Central

Spatial and temporal environmental variability are important drivers of ecological processes at all scales. As new tools allow the in situ exploration of individual responses to fluctuations, ecologically meaningful ways of characterizing environmental variability at organism scales are needed. We investigated the fine-scale spatial heterogeneity of high-frequency temporal variability in temperature, dissolved oxygen concentration, and pH experienced by benthic organisms in a shallow coastal coral reef. We used a spatio-temporal sampling design, consisting of 21 short-term time-series located along a reef flat-to-reef slope transect, coupled to a long-term station monitoring water column changes. Spectral analyses revealed sharp gradients in variance decomposed by frequency, as well as differences between physically-driven and biologically-reactive parameters. These results highlight the importance of environmental variance at organismal scales and present a new sampling scheme for exploring this variability in situ. PMID:24416364

Guadayol, Òscar; Silbiger, Nyssa J.; Donahue, Megan J.; Thomas, Florence I. M.

2014-01-01

246

Intraseasonal variability of the sea surface temperature in the Tropical Atlantic  

NASA Astrophysics Data System (ADS)

The sea surface temperature (SST) intraseasonal variability (ISV) and its interaction with the local surface wind in the tropical Atlantic Ocean are investigated using atmospheric observations and reanalyses of the 2000-2009 decade. Largest SST ISV centers are located in frontal areas of the three main tropical upwelling systems: the Eastern equatorial upwelling (east of 20°W), and the Senegal-Mauritania and Angola-Namibia coastal upwellings. The equatorial SST ISV is dominated by tropical instability waves (TIWs) west of 10°W, and a quasi-biweekly oscillation (QBO) further east, from May to August. Along the West-African coast, two adjacent regions of strong SST ISV are found north and south of 15°N. The southern one is most active during November-May and is dominated by 30-90 days periodicity, with SST anomalies mainly generated by stronger-than-normal Trade winds and Azores anticyclone. The northern one corresponds to a SST ISV maximal in June-September, and a dominant periodicity between 3 and 15 days, with SST anomalies driven by coastal surface wind modulations coming from African Easterly Waves. Off the Angola-Namibia coast, the SST ISV is also maximal at two locations: around 11°S all over the year, and near 21°S in November-March, with a dominant periodicity between 20 and 90 days in both regions. The SST anomalies are created by a jet of coastal southeasterlies mainly controlled by the large-scale St Helena anticyclone. The equatorial upwelling appears to be the region with the clearest signal of surface wind adjusting to SST anomalies, while it is more modest in the other two regions of coastal upwelling.

Diakhate, Moussa; Lazar, Alban; de Coetlogon, Gaëlle; Gaye, Amadou; Eymard, Laurence

2014-05-01

247

A temperature-based variable for monitoring outdoor coil airflow in an air-source heat pump during frost-forming conditions  

SciTech Connect

Frost-buildup tests were conducted on a 3-ton (10.6kW) nominal cooling capacity air-source heat pump with an orifice expansion device. This study was conducted to determine if a simple temperature-based control variable could be used to determine the amount of degradation in the outdoor airflow (and heating capacity) of the unit. Refrigerant pressures and temperatures were monitored through-out the system in addition to power requirements and airflow rates. A temperature-based variable was developed that could be used to predict airflow degradation across the outdoor heat exchanger. This variable was defined using the difference between ambient air temperature and a measured refrigerant temperature. Eight refrigerant temperatures in the system were recorded and evaluated. Plots of airflow as a function of this temperature variable, along with plots of the absolute value percent changes of this temperature variable and airflow, were evaluated to determine which refrigerant temperatures could best be used in the variable to predict degradation in airflow. The best fit between the temperature-based variable and airflow degradation occurred with the inclusion of the refrigerant temperature at the outlet from the evaporator. Calculations of percent changes based on values sampled after a defrost showed a polynomial or linear relationship between airflow and the temperature-based variable. Data from two previously tested heat pumps were also used to compare changes in the outdoor airflow to changes in the temperature-based variable. The base-case heat pump and another heat pump both used an orifice as the expansion device in the heating mode. A third heat pump, which used a thermostatic expansion valve (TXV) as the expansion device in the heating mode, failed to show the same goodness of fit between airflow and the temperature-based variable.

Payne, W.V. II; O`Neal, D.L. [Texas A and M Univ., College Station, TX (United States). Energy Systems Lab.

1994-12-31

248

Spectrophotometric and Calorimetric Studies of Np(V) Complexation with Acetate at Variable Temperatures (T = 283 - 343 K)  

SciTech Connect

Spectrophotometric titrations were performed to identify the Np(V)/acetate complex and determine the equilibrium constants at variable temperatures (T = 283 - 343 K) and at the ionic strength of 1.05 mol {center_dot} kg{sup -1}. The enthalpy of complexation at corresponding temperatures was determined by microcalorimetric titrations. Results show that the complexation of Np(V) with acetate is weak but strengthened as the temperature is increased. The complexation is endothermic and is entropy-driven. The enhancement of the complexation at elevated temperatures is primarily due to the increasingly larger entropy gain when the solvent molecules are released from the highly-ordered solvation spheres of NpO{sub 2}{sup +} and acetate to the bulk solvent where the degree of disorder is higher at higher temperatures.

Rao, Linfeng; Tian, Guoxin; Srinivasan, Thandankorai G.; Zanonato, PierLuigi; Di Bernardo, Plinio

2009-12-21

249

Variability of the Structure Parameters of Temperature and Humidity Observed in the Atmospheric Surface Layer Under Unstable Conditions  

NASA Astrophysics Data System (ADS)

The structure parameters of temperature and humidity are important in scintillometry as they determine the structure parameter of the refractive index of air, the primary atmospheric variable obtained with scintillometers. In this study, we investigate the variability of the logarithm of the Monin-Obukhov-scaled structure parameters (denoted as ) of temperature and humidity. We use observations from eddy-covariance systems operated at three heights (2.5, 50, and 90 m) within the atmospheric surface layer under unstable conditions. The variability of depends on instability and on the size of the averaging window over which is calculated. If instability increases, differences in between upward motions (large ) and downward motions (small ) increase. The differences are, however, not sufficiently large to result in a bimodal probability density function. If the averaging window size increases, the variances of decrease. A linear regression of the variances of versus the averaging window size for various stability classes shows an increase of both the offset and slope (in absolute sense) with increasing instability. For temperature, data from the three heights show comparable results. For humidity, in contrast, the offset and slope are larger at 50 and 90 m than at 2.5 m. In the end we discuss how these findings could be used to assess whether observed differences in along a scintillometer path or aircraft flight leg are just within the range of local variability in or could be attributed to surface heterogeneity. This is important for the interpretation of data measured above a heterogeneous surface.

Braam, Miranda; Moene, Arnold F.; Beyrich, Frank

2014-03-01

250

Joint Variability of Global Runoff and Global Sea Surface Temperatures GREGORY J. MCCABE  

E-print Network

with the Atlantic multidecadal oscillation (AMO). Corresponding author address: Gregory J. McCabe, U.S. Geo- logical% of the total variance and reflects variability of the El Nin~o­ Southern Oscillation (ENSO) and its associated and indicates a response of global annual runoff to variability in North Atlantic SSTs. The association between

251

Geographical pattern in first bloom variability and its relation to temperature sensitivity in the USA and China.  

PubMed

Advance in spring plant phenology over the last several decades has been found in all continents of the Northern Hemisphere. Compared to the studies detecting phenological trends, the studies investigating the geographical pattern of phenological variability (including mean date and magnitude of variability) are rather limited. In this study, we analyzed spatial pattern of mean date and standard deviation (SD) of first bloom date (FBD) time series (?15 years) for black locust (Robinia pseudoacacia) at 22 stations in China, common lilac (Syringa vulgaris) at 79 stations in the Western US and Chinese lilac (Syringa chinensis) at 45 stations in the Eastern US. Subsequently, the impact of geographical factors (latitude, longitude, and altitude) on the mean date and SD was quantified by using the multiple regression analysis method. Meanwhile, the relationship between FBD variability and temperature sensitivity of FBD was examined. Results showed that the mean FBD highly depended on geographical factors for all the three species. Compared to the mean date, the dependence of SD of FBD time series on geographical factors was weaker. The geographical factors could only explain 13 to 31 % of spatial variance in SD of FBD. The negative regression coefficients of latitude (P?variable at lower latitude. At most of stations, significant and negative correlations between FBD and preseason temperature on interannual scale were found, but the temperature sensitivity varied among different stations. The magnitude of temperature sensitivity decreased with increasing latitude. In general, the locations at lower latitude had earlier and more variable spring phenophase and showed stronger phenological response to climate change than the locations at higher latitude. PMID:25312515

Wang, Huanjiong; Ge, Quansheng; Dai, Junhu; Tao, Zexing

2014-10-14

252

Temperature and precipitation in Northeast China during the last 150 years: relationship to large-scale climatic variability  

NASA Astrophysics Data System (ADS)

The analysis of two historical time series of temperature and precipitation in Northeast China, spanning, respectively, 1870-2004 and 1841-2004, performed by continuous wavelet transform and other classical and advanced spectral methods, is presented here. Both variables show a particular trend and oscillations of about 85, 60, 35 and 20 years that are highly significant, with a phase opposition at the centennial scale and at the 20-year scale. The analysis of the four temperature series relative to single seasons shows that the 20-year cycle is typical of the summer monsoon season, while the 35-year cycle is most evident in winter. The cycles of ~ 60 years and longer are present in all seasons. The centennial variation of temperature and precipitation describes well the 1970-1980 transition between a period of relatively strong East Asian Summer Monsoon (EASM), corresponding to high precipitation and relatively cool temperatures in Northeast China, and a conditions of weak EASM (low precipitation and warm temperatures). The connection of the detected local variations with large-scale climatic variability is deduced from the comparison with different climatic records (Northern Hemisphere temperature, Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation indexes).

Alessio, S.; Taricco, C.; Rubinetti, S.; Vivaldo, G.; Mancuso, S.

2014-07-01

253

Early Holocene Centennial-Scale Sea Surface Temperature and Salinity Variability in the Florida Straits  

NASA Astrophysics Data System (ADS)

Paleoproxy data and modeling studies suggest that Early Holocene (10.5 - 7 kyr BP) climate in the western tropical North Atlantic (TNA) was warmer and wetter than today. Perihelion occurred during boreal summer, resulting in an amplified Early Holocene seasonal cycle and a reorganization of the tropical climate system (Oppo et al., 2007). Trace metal records from the Cariaco Basin (Haug et al., 2001) and ostracod ?18O records from Haiti (Hodell, 1991) suggest a northward shift in the Intertropical Convergence Zone (ITCZ) resulted in decreased evaporation-precipitation values in the western TNA. In addition, the final drainage of large pro-glacial lakes into the North Atlantic at 8.2 kyr BP is thought to have resulted in a meltwater-induced reduction in Atlantic meridional overturning circulation that caused widespread cooling in the circum-Atlantic region (Barber et al., 1999; Clarke et al., 2004; Ellison et al., 2006). In order to reconstruct centennial-scale records of Early Holocene sea surface temperature (SST) and salinity (SSS) variability in the Florida Straits, we will measure ?18O values as well as Mg/Ca and Ba/Ca ratios in the planktonic foraminifera Globigerinoides ruber from two sediment cores recovered from the Florida Straits: KNR166-2 JPC-51 (24°24.70’N, 83°13.14’W, 198 m; ~60-100 cm/kyr sedimentation rate) and KNR166-2 GGC-7 (24°21.50’N, 83°20.90’N, 535 m; ~55 cm/kyr sedimentation rate). SSTs are calculated from Mg/Ca ratios based on a published sediment trap calibration (Anand et al., 2003). Initial measurements of Mg/Ca ratios suggest centennial-scale SST oscillations during the Early Holocene. Calculated SSTs vary from 26.3 to 29.8°C and are within the range of modern seasonal variability for our core locations (25-30°C). Calculated Mg/Ca-SSTs will be combined with G. ruber ?18O values to calculate past ?18Oseawater values (a proxy for SSS) using a laboratory calibrated relationship (Bemis et al., 1998). In addition, Ba/Ca ratios in foraminifera can be used as a qualitative proxy for salinity change resulting riverine input (Weldeab et al., 2007). Laboratory experiments show that Ba+2 incorporation into living planktonic foraminifera shells is linear, dependent primarily on the [Ba+2] of the water in which the shell grows (Lea and Spero, 1994). Riverine water contains much higher concentrations of [Ba+2] relative to seawater. Furthermore, dissolved barium concentrations exhibit a conservative mixing with seawater, resulting in a linear inverse correlation between salinity and [Ba+2] (Coffey et al., 1997; Edmond et al., 1978; Hanor and Chan, 1977). The resulting Ba/Ca can then be used to identify periods of intensified riverine input into the Gulf of Mexico. Finally, we will compare our Florida Straits ?18Oseawater and Ba/Ca-SSS reconstructions with the previously published centennial-scale record of Early Holocene hydrologic change from the northern Gulf of Mexico’s Orca Basin (LoDico et al., 2006).

Weinlein, W. A.; Schmidt, M. W.; Lynch-Stieglitz, J. M.

2009-12-01

254

A comparison of surface air temperature variability in three 1000-Yr. coupled ocean-atmosphere model integrations  

SciTech Connect

This study compares the variability of surface air temperature in three long coupled ocean-atmosphere general circulation model integrations. It is shown that the annual mean climatology of the surface air temperatures (SAT) in all three models is realistic and the linear trends over the 1,000-yr integrations are small over most areas of the globe. Second, although there are notable differences among the models, the models' SAT variability is fairly realistic on annual to decadal timescales, both in terms of the geographical distribution and of the global mean values. A notable exception is the poor simulation of observed tropical Pacific variability. In the HadCM2 model, the tropical variability is overestimated, while in the GFDL and HAM3L models, it is underestimated. Also, the ENSO-related spectral peak in the globally averaged observed SAT differs from that in any of the models. The relatively low resolution required to integrate models for long time periods inhibits the successful simulation of the variability in this region. On timescales longer than a few decades, the largest variance in the models is generally located near sea ice margins in high latitudes, which are also regions of deep oceanic convection and variability related to variations in the thermohaline circulation. However, the exact geographical location of these maxima varies from model to model. The preferred patterns of interdecadal variability that are common to all three coupled models can be isolated by computing empirical orthogonal functions (EOFs) of all model data simultaneously using the common EOF technique. A comparison of the variance each model associated with these common EOF patterns shows that the models generally agree on the most prominent patterns of variability. However, the amplitudes of the dominant models of variability differ to some extent between the models and between the models and observations. For example, two of the models have a mode with relatively large values of the same sign over most of the Northern Hemisphere midlatitudes. This mode has been shown to be relevant for the separation of the temperature response pattern due to sulfate aerosol forcing from the response to greenhouse gas forcing.

Stouffer, R.J.; Hegerl, G.; Tett, S.

2000-02-01

255

Increased winter soil temperature variability enhances nitrogen cycling and soil biotic activity in temperate heathland and grassland mesocosms  

NASA Astrophysics Data System (ADS)

Winter air temperatures are projected to increase in the temperate zone, whereas snow cover is projected to decrease, leading to increased soil temperature variability, and potentially to changes in nutrient cycling. Here, we experimentally evaluated the effects of increased winter soil temperature variability on selected aspects of the N-cycle in mesocosms containing different plant community compositions. The experiment was replicated at two sites, a colder mountainous upland site with high snow accumulation and a warmer and drier lowland site. Increased soil temperature variability enhanced soil biotic activity for both sites during winter, as indicated by 35% higher nitrogen (N) availability in the soil solution, 40% higher belowground decomposition and a 25% increase in the potential activity of the enzyme cellobiohydrolase. The mobilization of N differed between sites, and the 15N signal in leaves was reduced by 31% in response to winter warming pulses, but only at the cold site, with significant reductions occurring for three of four tested plant species at this site. Furthermore, there was a trend of increased N leaching in response to the recurrent winter warming pulses. Overall, projected winter climate change in the temperate zone, with less snow and more variable soil temperatures, appears important for shifts in ecosystem functioning (i.e. nutrient cycling). While the effects of warming pulses on plant N mobilization did not differ among sites, reduced plant 15N incorporation at the colder temperate site suggests that frost damage may reduce plant N uptake in a warmer world, with important implications for nitrogen cycling and nitrogen losses from ecosystems.

Schuerings, J.; Jentsch, A.; Hammerl, V.; Lenz, K.; Henry, H. A. L.; Malyshev, A. V.; Kreyling, J.

2014-12-01

256

Large-scale spatial variability of riverbed temperature gradients in Snake River fall Chinook salmon spawning areas  

SciTech Connect

In the Snake River basin of the Pacific northwestern United States, hydroelectric dam operations are often based on the predicted emergence timing of salmon fry from the riverbed. The spatial variability and complexity of surface water and riverbed temperature gradients results in emergence timing predictions that are likely to have large errors. The objectives of this study were to quantify the thermal heterogeneity between the river and riverbed in fall Chinook salmon spawning areas and to determine the effects of thermal heterogeneity on fall Chinook salmon emergence timing. This study quantified river and riverbed temperatures at 15 fall Chinook salmon spawning sites distributed in two reaches throughout 160 km of the Snake River in Hells Canyon, Idaho, USA, during three different water years. Temperatures were measured during the fall Chinook salmon incubation period with self-contained data loggers placed in the river and at three different depths below the riverbed surface. At all sites temperature increased with depth into the riverbed, including significant differences (p<0.05) in mean water temperature of up to 3.8°C between the river and the riverbed among all the sites. During each of the three water years studied, river and riverbed temperatures varied significantly among all the study sites, among the study sites within each reach, and between sites located in the two reaches. Considerable variability in riverbed temperatures among the sites resulted in fall Chinook salmon emergence timing estimates that varied by as much as 55 days, depending on the source of temperature data used for the estimate. Monitoring of riverbed temperature gradients at a range of spatial scales throughout the Snake River would provide better information for managing hydroelectric dam operations, and would aid in the design and interpretation of future empirical research into the ecological significance of physical riverine processes.

Hanrahan, Timothy P.

2007-02-01

257

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

NASA Technical Reports Server (NTRS)

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 eastern China. This study explores the forcing mechanism of these trends in association with the global sea-surface temperature (SST) variations on the interannual and inter-decadal timescales. Results based on Singular Value Decomposition analyses (SVD) show that the interannual variability of China precipitation in boreal spring and summer can be well defined by two centers of actions for each season, which are co-varying with two interannual modes of SSTs. The first SVD modes of precipitation in spring and summer, which are centered in southeastern China and northern China, respectively, are linked to an ENSO-like mode of SSTs. The second SVD modes of precipitation in both seasons are confined to central eastern China, and are primarily linked to SST variations over the warm pool and Indian Ocean. Features of the anomalous 850-hPa winds and 700-Wa geopotential height corresponding to these modes support a physical mechanism that explains the causal links between the modal variations of precipitation and SSTs. On the decadal and longer timescale, similar causal links are found between the same modes of precipitation and SSTs, except for the case of springtime precipitation over central eastern China. For this case, while the interannual mode of precipitation is positively correlated with the interannual variations of SSTs over the warm pool and Indian Ocean; the inter-decadal mode is negatively correlated with a different SST mode, the North Pacific mode. The later is responsible for the observed downward trend of springtime precipitation over central eastern China. For all other cases, both the interannual and inter-decadal variations of precipitation can be explained by the same mode of SSTs. The upward trend of springtime precipitation over southeastern China and downward trend of summertime precipitation over northern China are attributable to the warming trend of the ENSO-like mode. The recent frequent summertime floods over central eastern China are linked to the warming trend of SSTs over the warm pool and Indian Ocean.

Yang, Fanglin; Lau, K.-M.

2004-01-01

258

Variable Temperatures Improves Survival of the Alfalfa Leafcutting Bee During Cold Storage  

Technology Transfer Automated Retrieval System (TEKTRAN)

Megachile rotundata are commonly held at low-temperatures for overwintering the prepupae or interrupting the spring incubation to synchronize the adult emergence with the peak alfalfa bloom. However, low-temperature exposure can be stressful depending on the temperature, duration of exposure, and th...

259

Diffusion-Broadened Velocity Spectra of Convection in Variable-Temperature BP-LED Experiments  

Microsoft Academic Search

When NMR diffusion experiments are performed at temperatures different from ambient temperature, temperature gradients due to probe design can cause thermal convection and therefore significantly affect the signal amplitude. Fourier transformation of the signal amplitude gives rise to a diffusion-broadened velocity spectrum, which contains information about the convection velocity. It is shown that when the diffusion broadening factor is smaller

Xi-An Mao; Olaf Kohlmann

2001-01-01

260

Decadal variability of the Tropical Atlantic Ocean Surface Temperature in shipboard measurements and in a Global Ocean-Atmosphere model  

NASA Technical Reports Server (NTRS)

Sea surface temperature (SST) variability was investigated in a 200-yr integration of a global model of the coupled oceanic and atmospheric general circulations developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The second 100 yr of SST in the coupled model's tropical Atlantic region were analyzed with a variety of techniques. Analyses of SST time series, averaged over approximately the same subregions as the Global Ocean Surface Temperature Atlas (GOSTA) time series, showed that the GFDL SST anomalies also undergo pronounced quasi-oscillatory decadal and multidecadal variability but at somewhat shorter timescales than the GOSTA SST anomalies. Further analyses of the horizontal structures of the decadal timescale variability in the GFDL coupled model showed the existence of two types of variability in general agreement with results of the GOSTA SST time series analyses. One type, characterized by timescales between 8 and 11 yr, has high spatial coherence within each hemisphere but not between the two hemispheres of the tropical Atlantic. A second type, characterized by timescales between 12 and 20 yr, has high spatial coherence between the two hemispheres. The second type of variability is considerably weaker than the first. As in the GOSTA time series, the multidecadal variability in the GFDL SST time series has approximately opposite phases between the tropical North and South Atlantic Oceans. Empirical orthogonal function analyses of the tropical Atlantic SST anomalies revealed a north-south bipolar pattern as the dominant pattern of decadal variability. It is suggested that the bipolar pattern can be interpreted as decadal variability of the interhemispheric gradient of SST anomalies. The decadal and multidecadal timescale variability of the tropical Atlantic SST, both in the actual and in the GFDL model, stands out significantly above the background 'red noise' and is coherent within each of the time series, suggesting that specific sets of processes may be responsible for the choice of the decadal and multidecadal timescales. Finally, it must be emphasized that the GFDL coupled ocean-atmosphere model generates the decadal and multidecadal timescale variability without any externally applied force, solar or lunar, at those timescales.

Mehta, Vikram M.; Delworth, Thomas

1995-01-01

261

Long-term trend and multi-annual variability of water temperature in the pristine Bela River basin (Slovakia)  

NASA Astrophysics Data System (ADS)

SummaryBiological processes in surface waters appreciably depend on temperature of water. This paper summarizes our investigations of water temperature in the Bela River. The Bela River is a mountainous stream not influenced by direct human activities, draining the headwaters of the Vah River basin in the Tatra National Park (TANAP), Slovakia. Our primary aim was to identify the long-term trends and multi-annual variability of the annual water temperature at the Podbanske gauging station, using temperature readings taken at 7.00 am for the period of 50 years (1959-2008). Long-term mean of the annual water temperature of the Bela River at the Podbanske gauging station (922 m a.s.l.) was 4.2 °C, the air temperature at Podbanske meteorological station (972 m a.s.l.) was 5.0 °C. Both, air and water temperature, show an increasing trend. While the air temperature within 50-years increased significantly by 1.5 °C, in the case of water temperature this increase was merely by 0.12 °C. On November 19, 2004, a wind-throw brushed the investigated area with an aftermath of 15.4% destroyed forest in the Bela basin, mainly along the area adjacent to the river. Therefore, in the second part of the study, the impact of the riparian vegetation growing along the river banks was evaluated for two distinctive periods, i.e. the period prior and after the wind-throw. We statistically analysed the changes in water temperature on 6-year time series of daily water temperature (November 2001 through November 2007). The results presented herein may be useful for defining boundary values for surface water temperature, as required by the EC Water Framework Directive.

Pekárová, Pavla; Miklánek, Pavol; Halmová, Dana; Onderka, Milan; Pekár, Ján; Ku?árová, Katarína; Liová, So?a; Škoda, Peter

2011-04-01

262

Exact solutions of laminar-boundary-layer equations with constant property values for porous wall with variable temperature  

NASA Technical Reports Server (NTRS)

Exact solution of the laminar-boundary-layer equations for wedge-type flow with constant property values are presented for transpiration-cooled surfaces with variable wall temperatures. The difference between wall and stream temperature is assumed proportional to a power of the distance from the leading edge. Solutions are given for a Prandtl number of 0.7 and ranges of pressure-gradient, cooling-air-flow, and wall-temperature-gradient parameters. Boundary-layer profiles, dimensionless boundary-layer thicknesses, and convective heat-transfer coefficients are given in both tabular and graphical form. Corresponding results for constant wall temperature and for impermeable surfaces are included for comparison purposes.

Donoughe, Patrick L; Livingood, John N B

1955-01-01

263

Determining the temporal variability in atmospheric temperature profiles measured using radiosondes and assessment of correction factors for different launch schedules  

NASA Astrophysics Data System (ADS)

Radiosondes provide one of the primary sources of upper atmosphere temperature data for numerical weather prediction, the assessment of long-term trends in atmospheric temperature, the study atmospheric processes and provide a source of intercomparison data for other temperature sensors e.g. satellites. When intercomparing different temperature profiles it is important to include the effect of temporal mis-match between the measurements. To help quantify this uncertainty the atmospheric temperature variation through the day needs to be assessed, so that a correction and uncertainty for time difference can be calculated. Temperature data from an intensive radiosonde campaign were analysed to calculate the hourly rate of change in temperature at different altitudes and provide recommendations and correction factors for different launch schedules. Using these results, three additional longer term data sets were analysed to assess the diurnal variability temperature as a function of altitude, time of day and season of the year. This provides data on the appropriate correction factors to use for a given temporal separation and the uncertainty associated with them. A general observation was that 10 or more repeat measurements would be required to get a standard uncertainty of less than 0.1 K h-1 of temporal mis-match.

Butterfield, D.; Gardiner, T.

2014-08-01

264

Temperature and salinity variability in the south-eastern corner of the Bay of Biscay (NE Atlantic)  

NASA Astrophysics Data System (ADS)

Temperature- and salinity-balance equations together with a one-dimensional model are used in this work to investigate the governing processes of the surface temperature and salinity variability at low and high frequencies in the southern Bay of Biscay. We found that the temporal evolution of mixed layer temperature is dominated by its seasonal cycle, mostly explained through a vertical balance (80-90%) that is mostly driven by air-sea heat exchange and contributed by entrainment, while horizontal advection plays a secondary role (? 12%). A substantial imbalance can be noticed in spring, which surprisingly strongly diminishes from 2003 onward, coinciding with apparent shifts in surface heat flow. The uncertainties of the air-sea heat fluxes and the advective and entrainment terms seem to be responsible for the imbalance of the temperature budget. On the contrary, the interannual variability dominates over the seasonal cycle of mixed layer salinity, and advection accounts for more than 70% of the budget terms, with the sum of vertical processes playing a secondary role. The different contributions of air-sea exchanges on temperature and salinity (heat vs. freshwater) are the ultimate cause of the different patterns observed for both of the parameters.

Somavilla, R.; González-Pola, C.; Lavín, A.; Rodriguez, C.

2013-01-01

265

Variable-wavelength solar-blind Raman lidar for remote measurement of atmospheric water-vapor concentration and temperature.  

PubMed

System definition and performance calculations are presented for a variable-wavelength solar-blind Raman lidar capable of remotely measuring profiles of atmospheric water-vapor concentration and temperature. A figure of merit is defined which is related to the wavelength dependent SNR. It is shown that the figure of merit for a particular output wavelength depends critically on the instantaneous total ozone overburden as well as the ozone content from the earth's surface up to a maximum measurement altitude. Figures of merit for water-vapor and temperature profile measurements are presented. Best performance output wavelengths are given, and total output energies required to yield prespecified accuracies are computed. PMID:20389833

Petri, K; Salik, A; Cooney, J

1982-04-01

266

The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability  

NASA Astrophysics Data System (ADS)

Earth's climate exhibits internal modes of variability on various timescales. Here we investigate multi-decadal variability of the Atlantic meridional overturning circulation (AMOC), Northern Hemisphere sea-ice extent and global mean temperature (GMT) in an ensemble of CMIP5 models under control conditions. We report an inter-annual GMT variability of about ±0.1° C originating solely from natural variability in the model ensemble. By decomposing the GMT variance into contributions of the AMOC and Northern Hemisphere sea-ice extent using a graph-theoretical statistical approach, we find the AMOC to contribute 8% to GMT variability in the ensemble mean. Our results highlight the importance of AMOC sea-ice feedbacks that explain 5% of the GMT variance, while the contribution solely related to the AMOC is found to be about 3%. As a consequence of multi-decadal AMOC variability, we report substantial variations in North Atlantic deep-ocean heat content with trends of up to 0.7 × 1022 J decade-1 that are of the order of observed changes over the last decade and consistent with the reduced GMT warming trend over this period. Although these temperature anomalies are largely density-compensated by salinity changes, we find a robust negative correlation between the AMOC and North Atlantic deep-ocean density with density lagging the AMOC by 5 to 11 yr in most models. While this would in principle allow for a self-sustained oscillatory behavior of the coupled AMOC-deep-ocean system, our results are inconclusive about the role of this feedback in the model ensemble.

Schleussner, C. F.; Runge, J.; Lehmann, J.; Levermann, A.

2014-02-01

267

Variable-temperature solid-state NMR studies of iron(II) and iron(III) complexes  

E-print Network

of nondia- magnetic solid materials using variable-temperature C cross-polarization/magic-angle spinning NMR spectroscopy. Solid Fe(II)/Zn(11) solutions (alloys) are used to simulate various high-spin/low-spin compositions of the spin crossover complex... coupled system, (OEPFe)20, in the solid state. Comparisons to a similar solution-state NMR study of the same complex provide evidence for significant structural differences in the two phases. DEDICATION This thesis is dedicated to my wonderful husband...

Shepard, Patricia Arlene

2012-06-07

268

Variable-Temperature Rate Coefficients of Proton-Transfer Equilibrium Reaction C2H4 + H3O+  

E-print Network

Variable-Temperature Rate Coefficients of Proton-Transfer Equilibrium Reaction C2H4 + H3O+ C2H5: The rate coefficients for the forward and reverse proton-transfer reactions C2H4 + H3O+ C2H5 + + H2O and S = (-15.0 ± 0.9) J·mol-1 ·K-1 , respectively. INTRODUCTION Proton-transfer reactions of simple molecules

Sanov, Andrei

269

Immediate Effects of Reiki on Heart Rate Variability, Cortisol Levels, and Body Temperature in Health Care Professionals With Burnout  

Microsoft Academic Search

Burnout is a work-related mental health impairment comprising three dimensions: emotional exhaustion, depersonalization, and reduced personal accomplishment. Reiki aims to help replenish and rebalance the body’s energetic system, thus stimulating the healing process. The objective of this placebo-controlled, repeated measures, crossover, single-blind, randomized trial was to analyze the immediate effects of Reiki on heart rate variability (HRV), body temperature, and

Lourdes Díaz-Rodríguez; Manuel Arroyo-Morales; Cesar Fernández-de-las-Peñas; Francisca García-Lafuente; Carmen García-Royo; Inmaculada Tomás-Rojas

2011-01-01

270

Temperature dependence of an estuarine harmful algal bloom: Resolving interannual variability in bloom dynamics using a degree day approach  

PubMed Central

Observations of harmful algal blooms (HABs) of the dinoflagellate Alexandrium fundyense in an estuary over multiple years were used to assess drivers of their spatial and temporal variability. Nauset Estuary on Cape Cod, Massachusetts has a recurrent, self-seeding A. fundyense population that produces paralytic shellfish poisoning toxins and leads to nearly annual closure to shellfishing. Weekly surveys of the entire estuary were made in 3 of 4 consecutive years, with surveys of a subembayment during the intervening year. Major A. fundyense blooms were observed all 4 years, with maximum concentrations >106 cells L?1. Concentrations were greatest in three salt ponds at the distal edges of the estuary. The bloom timing varied among the salt ponds and among years, although the blooms had similar durations and maximum cell concentrations. Nutrient concentrations did not correlate with the growth of the bloom, but differences in water temperature among years and ponds were significant. Net growth rates inferred from the surveys were similar to those from laboratory experiments, and increased linearly with temperature. A growing degree day calculation was used to account for effects of interannual variability and spatial gradients in water temperature on population development. The approach collapsed variability in the timing of bloom onset, development, and termination across years and among ponds, suggesting that this relatively simple metric could be used as an early-warning indicator for HABs in Nauset and similar areas with localized, self-seeding blooms. PMID:25419003

Ralston, David K.; Keafer, Bruce A.; Brosnahan, Michael L.; Anderson, Donald M.

2014-01-01

271

Performance of a Herriott Cell, Designed for Variable Temperatures between 296 and 20 K  

NASA Technical Reports Server (NTRS)

We designed, fabricated and tested a multipath Herriott cell (or off-axis spherical mirror interferometer) to achieve low temperature absorption measurements. The cell is fabricated entirely from copper and the 15 cm radius of curvature copper mirrors have gold coated reflective surfaces. The cell was tested at temperatures between 296 and 30 K with a folded absorption path length of 5.37 m utilizing a lead salt tunable diode laser. Short term temperature stability (1 h) of the Herriott cell is better than 0.005 K under normal operating conditions with a temperature uniformity better than 0.01 K (not measurable). The cell was tested by performing collisional cooling experiments on 13C16O2 in helium at temperatures between 70 and 20 K and by performing more traditional pressure broadening and shift measurements on molecular infrared absorption lines at temperatures between 300 and about 80 K on 13C16O2 methane.

Mondelain, Didier; Camy-Peyret, Claude; Mantz, Arlan W.; Tang, Emma; Valentin, Alain

2007-01-01

272

A Variable Temperature Walters Spiral Probe for the Critical Current Measurement of Superconducting Strands  

Microsoft Academic Search

We have developed a probe for the critical current measurements of low temperature superconducting strands at various field, temperature and strain. A 30 cm-long strand sample is soldered on a Walters spiral made of beryllium copper alloy and compressive or tensile axial strain can be applied up to 0.7%. Temperature control ability was tested using a MgB2 wire up to

Sangjun Oh; Chulhee Lee; Heekyung Choi; Kyungmo Moon; Keeman Kim; Jiman Kim; Pyeong-Yeol Park

2008-01-01

273

Interannual Variability of Temperature at a Depth of 125 Meters in the North Atlantic Ocean  

Microsoft Academic Search

Analyses of historical ocean temperature data at a depth of 125 meters in the North Atlantic Ocean indicate that from 1950 to 1990 the subtropical and subarctic gyres exhibited linear trends that were opposite in phase. In addition, multivariate analyses of yearly mean temperature anomaly fields between 20^circN and 70^circN in the North Atlantic show a characteristic space-time temperature oscillation

Sydney Levitus; John I. Antonov; Timothy P. Boyer

1994-01-01

274

Investigating variability in catch rates of halibut ( Hippoglossus stenolepis) in the Pribilof Islands: Is temperature important?  

NASA Astrophysics Data System (ADS)

From 2002 to 2004, a study was conducted to test the hypothesis that commercial catch per unit effort (CPUE) of Pacific halibut ( Hippoglossus stenolepis) in the Pribilof Islands local fishery varies on intra-annual (weeks-months) and inter-annual (among fishing seasons) time scales due to (a) variation in seasonal migration timing, (b) temperature-dependent habitat preference, or (c) average local abundance governed by late spring hydrographic conditions. Changes in CPUE over the progression of three fishing seasons were examined for evidence of seasonal migration signals. Relationships between catch and water temperature were examined by deploying temperature recorders from local commercial vessels and correlating the observations with vessel-standardized CPUE intra- and inter-annually. Temperature data were obtained from 735-longline sets; simultaneous depth data were collected from a subset of 412 of those deployments. Annual temperature data clearly demonstrated seasonal warming trends, and temperature was negatively correlated with depth. Warmest conditions were observed in 2003: maximum temperatures of ˜6 °C were observed in early June and increased to ˜10 °C in early September. Conditions in 2002 and 2004 were similar to one another and on average about 1 °C cooler than in 2003, warming from ˜5 °C in June to ˜9.5 °C in September. No intra-annual trend in CPUE was apparent. A relationship was not detected between temperature and vessel-standardized CPUE within years, whether CPUE was compared to absolute temperature or the difference between observed temperature and daily-predicted maximum. These results suggest that halibut do not respond strongly to temperatures within the observed range, nor was there evidence that the fishery was influenced by seasonal movement patterns. These conclusions are supported by concurrent archival tagging that suggests the Pribilof fishery may be too short to capture seasonal migration periods; summer local abundance is likely established prior to commencement of the fishery. Temperatures observed by the fleet were also within the known thermal tolerances of Pacific halibut. Inter-annually, cumulative fleet-wide CPUE and total catch were associated with coolest annual mean temperature. A relationship might exist between annual CPUE and mean temperature, but the available time series is too short to draw conclusions in this regard. While there was no trend in CPUE from June through August or across temperatures ranging from 5 to 10 °C, the results may be valuable in refining hypotheses and focusing future effort. Additional research should seek to examine catch trends earlier and later in the year, as well as at higher and lower temperatures, perhaps at the edges of the species's geographic range or during years characterized by anomalous hydrographic conditions.

Loher, Timothy

2008-08-01

275

The Schaake shuffle: A method for reconstructing space-time variability in forecasted precipitation and temperature fields  

USGS Publications Warehouse

A number of statistical methods that are used to provide local-scale ensemble forecasts of precipitation and temperature do not contain realistic spatial covariability between neighboring stations or realistic temporal persistence for subsequent forecast lead times. To demonstrate this point, output from a global-scale numerical weather prediction model is used in a stepwise multiple linear regression approach to downscale precipitation and temperature to individual stations located in and around four study basins in the United States. Output from the forecast model is downscaled for lead times up to 14 days. Residuals in the regression equation are modeled stochastically to provide 100 ensemble forecasts. The precipitation and temperature ensembles from this approach have a poor representation of the spatial variability and temporal persistence. The spatial correlations for downscaled output are considerably lower than observed spatial correlations at short forecast lead times (e.g., less than 5 days) when there is high accuracy in the forecasts. At longer forecast lead times, the downscaled spatial correlations are close to zero. Similarly, the observed temporal persistence is only partly present at short forecast lead times. A method is presented for reordering the ensemble output in order to recover the space-time variability in precipitation and temperature fields. In this approach, the ensemble members for a given forecast day are ranked and matched with the rank of precipitation and temperature data from days randomly selected from similar dates in the historical record. The ensembles are then reordered to correspond to the original order of the selection of historical data. Using this approach, the observed intersite correlations, intervariable correlations, and the observed temporal persistence are almost entirely recovered. This reordering methodology also has applications for recovering the space-time variability in modeled streamflow. ?? 2004 American Meteorological Society.

Clark, M.; Gangopadhyay, S.; Hay, L.; Rajagopalan, B.; Wilby, R.

2004-01-01

276

Simulations of Atmospheric Variability Induced by Sea Surface Temperatures and Implications for Global Warming  

Microsoft Academic Search

An atmospheric general circulation model was forced with observed interannual changes in the global sea surface temperatures (SSTs) for the period 1982 to 1993. The simulated seasonal surface air temperature patterns over land areas closely resemble the observed. Over most of the globe, the patterns also resemble those associated with El Nino events and are also reproduced in simulations with

Arun Kumar; Ants Leetmaa; Ming Ji

1994-01-01

277

Temperature variability in the tropical mesosphere during the northern hemisphere winter  

Microsoft Academic Search

Temperature observations at 20 90 km height and 5°N 15°N during the period of December 1992 March 1993 from the WINDII and MLS experiments on the UARS satellite are analysed together with MF radar winds and UKMO assimilated fields of temperature and zonal and meridional winds. The correlation between the different datasets at the tropics and zonal mean wind data

M. G. Shepherd; D. L. Wu; I. N. Fedulina; S. Gurubaran

2008-01-01

278

Sensitivity of summer stream temperatures to climate variability in the Pacific Northwest  

NASA Astrophysics Data System (ADS)

the thermal response of streams to a warming climate is important for prioritizing native fish conservation efforts. While there are plentiful estimates of air temperature responses to climate change, the sensitivity of streams, particularly small headwater streams, to warming temperatures is less well understood. A substantial body of literature correlates subannual scale temperature variations in air and stream temperatures driven by annual cycles in solar angle; however, these may be a low-precision proxy for climate change driven changes in the stream energy balance. We analyzed summer stream temperature records from forested streams in the Pacific Northwest for interannual correlations to air temperature and standardized annual streamflow departures. A significant pattern emerged where cold streams always had lower sensitivities to air temperature variation, while warm streams could be insensitive or sensitive depending on geological or vegetation context. A pattern where cold streams are less sensitive to direct temperature increases is important for conservation planning, although substantial questions may yet remain for secondary effects related to flow or vegetation changes induced by climate change.

Luce, Charles; Staab, Brian; Kramer, Marc; Wenger, Seth; Isaak, Dan; McConnell, Callie

2014-04-01

279

Hydrogeologic responses to three-dimensional temperature variability, Costa Rica subduction margin  

Microsoft Academic Search

Seaward of the subduction zone off Nicoya Peninsula, Costa Rica, differences in the thermal state of the ocean crust occur across a transition between crust generated at the Cocos-Nazca Spreading Center and crust formed at the East Pacific Rise. This change in the thermal state of the subducting plate results in along-strike differences in subduction zone temperature. These temperature variations

Glenn A. Spinelli; Demian M. Saffer; Michael B. Underwood

2006-01-01

280

A new variable temperature solution-solid interface scanning tunneling microscope  

NASA Astrophysics Data System (ADS)

We present a new solution-solid (SS) interface scanning tunneling microscope design that enables imaging at high temperatures with low thermal drift and with volatile solvents. In this new design, distinct from the conventional designs, the entire microscope is surrounded in a controlled-temperature and controlled-atmosphere chamber. This allows users to take measurements at high temperatures while minimizing thermal drift. By incorporating an open solution reservoir in the chamber, solvent evaporation from the sample is minimized; allowing users to use volatile solvents for temperature dependent studies at high temperatures. The new design enables the user to image at the SS interface with some volatile solvents for long periods of time (>24 h). An increase in the nonlinearity of the piezoelectric scanner in the lateral direction as a function of temperature is addressed. A temperature dependent study of cobalt(II) octaethylporphyrin (CoOEP) at the toluene/Au(111) interface has been performed with this instrument. It is demonstrated that the lattice parameters remain constant within experimental error from 24 °C to 75 °C. Similar quality images were obtained over the entire temperature range. We report the unit cell of CoOEP at the toluene/Au(111) interface (based on two molecules per unit cell) to be A = (1.36 ± 0.04) nm, B = (2.51 ± 0.04) nm, and ? = 97° ± 2°.

Jahanbekam, Abdolreza; Mazur, Ursula; Hipps, K. W.

2014-10-01

281

Identifying spatial variability of groundwater discharge in a wetland stream using a distributed temperature sensor  

USGS Publications Warehouse

Discrete zones of groundwater discharge in a stream within a peat-dominated wetland were identified on the basis of variations in streambed temperature using a distributed temperature sensor (DTS). The DTS gives measurements of the spatial (??1 m) and temporal (15 min) variation of streambed temperature over a much larger reach of stream (>800 m) than previous methods. Isolated temperature anomalies observed along the stream correspond to focused groundwater discharge zones likely caused by soil pipes within the peat. The DTS also recorded variations in the number of temperature anomalies, where higher numbers correlated well with a gaining reach identified by stream gauging. Focused zones of groundwater discharge showed essentially no change in position over successive measurement periods. Results suggest DTS measurements will complement other techniques (e.g., seepage meters and stream gauging) and help further improve our understanding of groundwater-surface water dynamics in wetland streams. Copyright 2007 by the American Geophysical Union.

Lowry, C.S.; Walker, J.F.; Hunt, R.J.; Anderson, M.P.

2007-01-01

282

Empirical temperature-based estimates of variability in the oceanic uptake of CO2 over the past 2 decades  

NASA Astrophysics Data System (ADS)

We infer the year-to-year variability of net global air-sea CO2 fluxes from observed interannual changes in wind speed and estimated differences in CO2 partial pressure between surface seawater (pCO2SW) and the overlying atmosphere. Changes in pCO2SW are estimated from changes in sea surface temperature via seasonal algorithms that relate pCO2SW to sea surface temperature. Our diagnostic model yields an interannual variability of ±0.18 petagrams (1?, Pg = 1015 grams) of carbon per year for the period 1982-2001. El Niño Southern Oscillation-induced changes in the equatorial efflux contribute approximately 70% of the diagnostic modeled global variability. Regional flux anomalies for areas outside the equatorial Pacific are found to neither systematically reinforce nor counteract each other during times of transition from El Niño years to normal years. The interannual variability of ±0.18 Pg C yr-1 obtained in the present work is at the low end of previous estimates that falls in the range of ±0.2 to ±0.5 Pg C yr-1. Of the previous estimates, lower values are generally estimated from global ocean circulation-biogeochemical models, while higher values are derived from atmospheric inversion models constrained by atmospheric CO2 observations. Comparisons of our modeled results with two time series data sets and equatorial Pacific data suggest that our diagnostic model is not able to capture the full range of pCO2SW variations; this is probably due to the inability of the empirical model to fully account for changes in surface pCO2SW related to ocean biological and physical processes. The small interannual variability in our modeled fluxes suggests that observed year-to-year variations in the rate of atmospheric CO2 increase are primarily caused by changes in the rate of CO2 uptake by the land biosphere.

Park, Geun-Ha; Lee, Kitack; Wanninkhof, Rik; Feely, Richard A.

2006-07-01

283

CANOPY TEMPERATURE VARIABILITY AS AN INDICATOR OF CROP WATER STRESS SEVERITY 1731  

Technology Transfer Automated Retrieval System (TEKTRAN)

Irrigation scheduling requires an operational means to quantify plant water stress. Remote sensing may offer quick measurements with regional coverage that cannot be achieved by current ground-based sampling techniques. This study explored the relation between variability in fine-resolution measurem...

284

Linking Global Climate and Temperature Variability to Widespread Amphibian Declines Putatively Caused by Disease  

Microsoft Academic Search

The role of global climate change in the decline of biodiversity and the emergence of infectious diseases remains controversial, and the effect of climatic variability, in particular, has largely been ignored. For instance, it was recently revealed that the proposed link between climate change and widespread amphibian declines, putatively caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), was tenuous because

Jason R. Rohr; Thomas R. Raffel

2010-01-01

285

Long-term measurement of temperature variabilities off Mindanao Island by the ocean acoustic tomography  

Microsoft Academic Search

Oceanic variabilities off Mindanao Island, Philippines where the North Equatorial Current branches into the Kuroshio and the Mindanao Current were measurerd for a period from 14 Feb.–1 Jun. 1992 by the oceean acoustic tomography (OAT). From the beginning of April, the travel time of acoustic rays propagating over a horizontal distance of about 250km, through the depth range of 80–4700

Gang Yuan; Iwao Nakao; Hidetoshi Fujimori; Arata Kaneko

1995-01-01

286

In Situ Acoustic Temperature Measurement During Variable-Frequency Microwave Curing  

Microsoft Academic Search

Variable-frequency microwave (VFM) curing can perform the same processing steps as conventional thermal processing in minutes, without compromising intrinsic material properties. With increasing demand for novel dielectrics, there is a corresponding demand for new processing techniques that lead to comparable or better properties than conventional methods. VFM processing can be a viable alternative to conventional thermal techniques. However, current limitations

Cleon E. Davis; Anthony J. Dickherber; William D. Hunt; Gary S. May

2008-01-01

287

An optics-based variable-temperature assay system for characterizing thermodynamics of biomolecular reactions on solid support  

NASA Astrophysics Data System (ADS)

A biological state is equilibrium of multiple concurrent biomolecular reactions. The relative importance of these reactions depends on physiological temperature typically between 10 °C and 50 °C. Experimentally the temperature dependence of binding reaction constants reveals thermodynamics and thus details of these biomolecular processes. We developed a variable-temperature opto-fluidic system for real-time measurement of multiple (400-10 000) biomolecular binding reactions on solid supports from 10 °C to 60 °C within ±0.1 °C. We illustrate the performance of this system with investigation of binding reactions of plant lectins (carbohydrate-binding proteins) with 24 synthetic glycans (i.e., carbohydrates). We found that the lectin-glycan reactions in general can be enthalpy-driven, entropy-driven, or both, and water molecules play critical roles in the thermodynamics of these reactions.

Fei, Yiyan; Landry, James P.; Li, Yanhong; Yu, Hai; Lau, Kam; Huang, Shengshu; Chokhawala, Harshal A.; Chen, Xi; Zhu, X. D.

2013-11-01

288

An optics-based variable-temperature assay system for characterizing thermodynamics of biomolecular reactions on solid support  

SciTech Connect

A biological state is equilibrium of multiple concurrent biomolecular reactions. The relative importance of these reactions depends on physiological temperature typically between 10?°C and 50?°C. Experimentally the temperature dependence of binding reaction constants reveals thermodynamics and thus details of these biomolecular processes. We developed a variable-temperature opto-fluidic system for real-time measurement of multiple (400–10?000) biomolecular binding reactions on solid supports from 10?°C to 60?°C within ±0.1?°C. We illustrate the performance of this system with investigation of binding reactions of plant lectins (carbohydrate-binding proteins) with 24 synthetic glycans (i.e., carbohydrates). We found that the lectin-glycan reactions in general can be enthalpy-driven, entropy-driven, or both, and water molecules play critical roles in the thermodynamics of these reactions.

Fei, Yiyan; Landry, James P.; Zhu, X. D., E-mail: xdzhu@physics.ucdavis.edu [Department of Physics, University of California, One Shields Avenue, Davis, California 95616 (United States); Li, Yanhong; Yu, Hai; Lau, Kam; Huang, Shengshu; Chokhawala, Harshal A.; Chen, Xi [Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616 (United States)] [Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616 (United States)

2013-11-15

289

Temperature compensation analysis of liquid lens for variable-focus control  

NASA Astrophysics Data System (ADS)

In this work, a fabrication and temperature compensation analysis and electrowetting for the liquid lenses is proposed. The unique capability of controlling the lens profile during the electrowetting fabrication processes is successfully demonstrated for different ambient temperature environment. For a lens fabricated on a hydrophobic Teflon layer, it is found that when the applied voltage is increased, the focal length increases, and the curvature decreases. One challenge for the liquid lens is operating temperature range. Due to the environment temperature change, the ability of controlling the lens profile is analyzed and measured. The description of change in contact angle corresponding to the variation of ambient temperature is derived. Based on this description, we firstly derive the control of voltage vs. temperature for a fixed dioptric power. The control of lens during a focusing action was studied by observation of the image formed by the light through the transparent bottom of ITO glass. Under several conditions of ambient temperature change, capability of controlling the lens profile for a fixed focus is successfully demonstrated by experiments.

Chen, Shu-Jung; Tai, Tsai-Lin; Shen, Chih-Hsiung

2006-01-01

290

Estuarine intertidal sediment temperature variability in Zoster marina and Z. japonica habitats in Yaquina Bay, Oregon  

EPA Science Inventory

Physical characterization of intertidal estuarine plant habitats over time may reveal distribution-limiting thresholds. Temperature data from loggers embedded in sediment in transects crossing Zostera marina and Z. japonica habitats in lower Yaquina Bay, Oregon display signific...

291

Temperature variability in the tropical mesosphere during the northern hemisphere winter  

Microsoft Academic Search

Temperature observations at 20–90km height and 5°N–15°N during the period of December 1992–March 1993 from the WINDII and MLS experiments on the UARS satellite are analysed together with MF radar winds and UKMO assimilated fields of temperature and zonal and meridional winds. The correlation between the different datasets at the tropics and zonal mean wind data at mid latitudes is

M. G. Shepherd; D. L. Wu; I. N. Fedulina; S. Gurubaran

2008-01-01

292

Sensitivity of frost occurrence to temperature variability in the European Alps  

NASA Astrophysics Data System (ADS)

In this study, we set out to investigate the linkage of frost frequency to monthly mean temperature and its sensitivity to temperature changes. According to other related studies, the linkage between frost frequency and monthly mean temperature is approximated month per month via hyperbolic tangent functions. These models are validated using three validation experiments including split sample tests and temporal cross-validation. As there are quality-checked station data in Austria, whose temporal resolution and length allow for such a validation procedure, the validation experiments are conducted there.After the performance of the empirical models is evaluated and found adequate, the hyperbolic tangent approach is applied to about 500 stations within the so called Greater Alpine region (GAR), which extends from about 4 °E to 18 °E and from 44 °N to 49 °N. Using these models, it is possible to derive the sensitivity of frost frequency for any location for which the annual temperature cycle is known. This strategy is explicitly demonstrated for the Po Plain, where vertical temperature profiles on a monthly base are on hand as well as in Austria, where spatially high resolved maps of monthly mean temperature are available. Moreover, at stations for which long-term homogenised series of monthly mean temperature are available, reconstructions of frost frequency via the empirical models are done, returning to historical periods where no measurements of minimum temperature exist.On the basis of these findings, the impact of a possible future warming can be assessed, which is essential with regard to glaciers, permafrost and avalanches. Reduction in frost might bring positive economic aspects for agriculture, but negative consequences for low level skiing areas. Copyright

Auer, Ingeborg; Matulla, Christoph; Böhm, Reinhard; Ungersböck, Markus; Maugeri, Maurizio; Nanni, Teresa; Pastorelli, Rossella

2005-11-01

293

Solar variability and climate change: Geomagnetic aa index and global surface temperature  

Microsoft Academic Search

During the past ~120 years, Earth's surface temperature is correlated with both decadal averages and solar cycle minimum values of the geomagnetic aa index. The correlation with aa minimum values suggests the existence of a long-term (low-frequency) component of solar irradiance that underlies the 11-year cyclic component. Extrapolating the aa-temperature correlations to Maunder Minimum geomagnetic conditions implies that solar forcing

E. W. Cliver; V. Boriakoff; J. Feynman

1998-01-01

294

Climatic change by cloudiness linked to the spatial variability of sea surface temperatures  

NASA Technical Reports Server (NTRS)

An active role in modifying the earth's climate is suggested for low cloudiness over the circumarctic oceans. Such cloudiness, linked to the spatial differences in ocean surface temperatures, was studied. The temporal variations from year to year of ocean temperature patterns can be pronounced and therefore, the low cloudiness over this region should also show strong temporal variations, affecting the albedo of the earth and therefore the climate. Photographs are included.

Otterman, J.

1975-01-01

295

Influence of topographic and environmental variability on model uncertainty: a case study on snow and ground temperatures in mountain regions  

NASA Astrophysics Data System (ADS)

A variety of physically based models to predict and understand the spatio-temporal behaviour of snow and ground temperatures have been developed in recent years. Model evaluation including the analysis of model uncertainty and validation is widely accepted as fundamental in enhancing trust in decisions that are based on model simulations. Due to constraints on resources or lack of distributed validation data, model evaluation is often restricted to one or few locations only, even if the model is applied to make predictions for large spatial areas and time periods. Thus, conclusions about model behaviour entail the tacit assumption that validation at one point can inform decisions about model performance in different environmental conditions. The effect of this assumption on model application and development when modeling phenomena in highly variable terrain or over large distances has rarely been studied. This study is focused on a sensitivity and uncertainty analysis of an energy and mass balance model that simulates snow and ground temperatures. It serves as a case study examining the role of topography and soil on parametric model uncertainty and sensitivity. A sensitivity analysis on individual parameters and a Monte Carlo based uncertainty study are performed at a variety of locations covering the range of topographic and environmental variability typically found in mountain regions. The results indicate that model uncertainties and sensitivities vary strongly under differing environmental conditions. This demonstrates that model evaluation (validation, sensitivity and uncertainty analyses) benefits strongly from the consideration of differing variables and, especially, the environmental variation of their behaviour.

Gubler, S.; Gruber, S.; Purves, R.; Endrizzi, S.

2012-12-01

296

Effect of design variables, temperature gradients and speed of life and reliability of a rotating disk  

NASA Technical Reports Server (NTRS)

A generalized methodology to predict the fatigue life and reliability of a rotating disk such as used for aircraft engine turbines and compressors is advanced. The approach incorporates the computed life of elemental stress volumes to predict system life and reliability. Disk speed and thermal gradients as well as design variables such as disk diameter and thickness and bolt hole size, number and location are considered.

Zaretsky, E. V.; Smith, T. E.; August, R.

1986-01-01

297

The effect of two-temperature post-shock accretion flow on the linear polarization pulse in magnetic cataclysmic variables  

E-print Network

The temperatures of electrons and ions in the post-shock accretion region of a magnetic cataclysmic variable (mCV) will be equal at sufficiently high mass flow rates or for sufficiently weak magnetic fields. At lower mass flow rates or in stronger magnetic fields, efficient cyclotron cooling will cool the electrons faster than the electrons can cool the ions and a two-temperature flow will result. Here we investigate the differences in polarized radiation expected from mCV post-shock accretion columns modeled with one- and two-temperature hydrodynamics. In an mCV model with one accretion region, a magnetic field >~30 MG and a specific mass flow rate of ~0.5 g/cm/cm/s, along with a relatively generic geometric orientation of the system, we find that in the ultraviolet either a single linear polarization pulse per binary orbit or two pulses per binary orbit can be expected, depending on the accretion column hydrodynamic structure (one- or two-temperature) modeled. Under conditions where the physical flow is two-temperature, one pulse per orbit is predicted from a single accretion region where a one-temperature model predicts two pulses. The intensity light curves show similar pulse behavior but there is very little difference between the circular polarization predictions of one- and two-temperature models. Such discrepancies indicate that it is important to model some aspect of two-temperature flow in indirect imaging procedures, like Stokes imaging, especially at the edges of extended accretion regions, were the specific mass flow is low, and especially for ultraviolet data.

Gordon E. Sarty; Curtis J. Saxton; Kinwah Wu

2008-08-05

298

Northern Hemisphere sea level pressure synchronization and its effect on Northern Hemisphere temperature variability  

NASA Astrophysics Data System (ADS)

We consider monthly anomalies of zonally averaged sea level pressure (SLP) in the Northern Hemisphere (NH) from two reanalysis products. A measure of synchronization utilizing correlation coefficient in a five-year sliding window across all latitude pairs is computed over this data. It is found that there have been two NH SLP synchronization episodes since the 1890s, which are significant to approximately three standard deviations. Similar statistically significant synchronization events are seen in simulations of 42 global climate models (GCM) with the dominant synchronization pattern in GCMs proving dynamically consistent with observations. Furthermore, a GCM-based NH temperature anomaly composite shows a flattening of temperature time series in a decade prior to the synchronization episodes, a brief warming trend just after episodes, and a cooling trend thereafter, all of which agrees with the temperature structure around the observed synchronization episode seen in the 1890s. NH sea ice concentration anomalies are also composited from global climate models and show a decrease in ice concentration approximately one to two years after the maximum increase in temperature and an increase in ice concentration one to two years after the maximum decrease in temperature. These results have substantial implications for climate prediction up to a decade in advance.

Verbeten, Joshua D.

299

Latitude and Altitude Dependence of the Interannual Variability and Trends of Atmospheric Temperatures  

NASA Astrophysics Data System (ADS)

The 4-season (12-month) running means of temperatures at five atmospheric levels (surface, 850-300 mb, 300-100 mb, 100-50 mb, 100-30 mb) and seven climatic zones (60°N-90°N, 30°N-60°N, 10°N-30°N, 10°N-10°S, 10°S-30°S, 30°S-60°S, 60°S-90°S) showed QBO (Quasi-biennial Oscillation), QTO (Quasi-triennial Oscillation) and larger periodicities. For stratosphere and tropopause, the temperature variations near the equator and North Pole somewhat resembled the 50mb low latitude zonal winds, mainly due to prominent QBO. For troposphere and surface, the temperature variations, especially those near the equator, resemble those of eastern equatorial Pacific sea-surface temperatures, mainly due to prominent QTO. In general, the temperature trends in the last 35 years show stratospheric cooling and tropospheric warming. But the trends are not monotonic. For example, the surface trends were downward during 1960-70, upward during 1970-82, downward during 1982-85 and upward thereafter. Models of green-house warming should take these non-uniformities into account.

Kane, R. P.; Buriti, R. A.

1997-08-01

300

Variability of sea surface temperature in the Japan Sea and its relationship to the wind-curl field  

NASA Astrophysics Data System (ADS)

The variability of sea surface temperature (SST) in the Japan Sea is investigated using the complex EOF analysis of daily data produced at Tohoku University, Japan (New Generation SST; 2002-2006). The relationship with the wind field is investigated from the daily NCEP/NCAR reanalysis data with a 1° spatial resolution. Anomalies in the SST (SSTAs) are calculated by subtracting the basin-average annual variation estimated as a leading mode of temperature. The leading mode of an SSTA represents a adjustment to the annual mean variation, most significant in December in the zone of subtropical waters entering the sea through the Korean Strait and in the northwestern sea, over which a cyclonic wind curl develops in the cold period. The semiannual variability mode is identified, which is characterized by the largest temperature increase (decrease) in the western branch of the subarctic front (in the Tatar Strait), which lags by two months behind the semiannual changes in wind curl over the sea. An episodic SSTA movement is detected in the northern part of the sea, which moves from east to west along the western branch of the Tsushima Warm Current with a speed corresponding in magnitude to an advective scale.

Trusenkova, O. O.; Lobanov, V. B.; Kaplunenko, D. D.

2008-08-01

301

Sample mounting and transfer for coupling an ultrahigh vacuum variable temperature beetle scanning tunneling microscope with conventional surface probes  

SciTech Connect

We present a new ultrahigh vacuum (UHV) chamber for surface analysis and microscopy at controlled, variable temperatures. The new instrument allows surface analysis with Auger electron spectroscopy, low energy electron diffraction, quadrupole mass spectrometer, argon ion sputtering gun, and a variable temperature scanning tunneling microscope (VT-STM). In this system, we introduce a novel procedure for transferring a sample off a conventional UHV manipulator and onto a scanning tunneling microscope in the conventional ''beetle'' geometry, without disconnecting the heating or thermocouple wires. The microscope, a modified version of the Besocke beetle microscope, is mounted on a 2.75 in. outer diameter UHV flange and is directly attached to the base of the chamber. The sample is attached to a tripod sample holder that is held by the main manipulator. Under UHV conditions the tripod sample holder can be removed from the main manipulator and placed onto the STM. The VT-STM has the capability of acquiring images between the temperature range of 180--500 K. The performance of the chamber is demonstrated here by producing an ordered array of island vacancy defects on a Pt(111) surface and obtaining STM images of these defects.

Nafisi, Kourosh; Ranau, Werner; Hemminger, John C.

2001-01-01

302

Precipitation and temperature space-time variability and extremes in the Mediterranean region: evaluation of dynamical and statistical downscaling methods  

NASA Astrophysics Data System (ADS)

This study evaluates how statistical and dynamical downscaling models as well as combined approach perform in retrieving the space-time variability of near-surface temperature and rainfall, as well as their extremes, over the whole Mediterranean region. The dynamical downscaling model used in this study is the Weather Research and Forecasting (WRF) model with varying land-surface models and resolutions (20 and 50 km) and the statistical tool is the Cumulative Distribution Function-transform (CDF-t). To achieve a spatially resolved downscaling over the Mediterranean basin, the European Climate Assessment and Dataset (ECA&D) gridded dataset is used for calibration and evaluation of the downscaling models. In the frame of HyMeX and MED-CORDEX international programs, the downscaling is performed on ERA-I reanalysis over the 1989-2008 period. The results show that despite local calibration, CDF-t produces more accurate spatial variability of near-surface temperature and rainfall with respect to ECA&D than WRF which solves the three-dimensional equation of conservation. This first suggests that at 20-50 km resolutions, these three-dimensional processes only weakly contribute to the local value of temperature and precipitation with respect to local one-dimensional processes. Calibration of CDF-t at each individual grid point is thus sufficient to reproduce accurately the spatial pattern. A second explanation is the use of gridded data such as ECA&D which smoothes in part the horizontal variability after data interpolation and damps the added value of dynamical downscaling. This explains partly the absence of added-value of the 2-stage downscaling approach which combines statistical and dynamical downscaling models. The temporal variability of statistically downscaled temperature and rainfall is finally strongly driven by the temporal variability of its forcing (here ERA-Interim or WRF simulations). CDF-t is thus efficient as a bias correction tool but does not show any added-value regarding the time variability of the downscaled field. Finally, the quality of the reference observation dataset is a key issue. Comparison of CDF-t calibrated with ECA&D dataset and WRF simulations to local measurements from weather stations not assimilated in ECA&D, shows that the temporal variability of the downscaled data with respect to the local observations is closer to the local measurements than to ECA&D data. This highlights the strong added-value of dynamical downscaling which improves the temporal variability of the atmospheric dynamics with regard to the driving model. This article highlights the benefits and inconveniences emerging from the use of both downscaling techniques for climate research. Our goal is to contribute to the discussion on the use of downscaling tools to assess the impact of climate change on regional scales.

Flaounas, Emmanouil; Drobinski, Philippe; Vrac, Mathieu; Bastin, Sophie; Lebeaupin-Brossier, Cindy; Stéfanon, Marc; Borga, Marco; Calvet, Jean-Christophe

2013-06-01

303

Temperature-dependent daily variability of precipitable water in special sensor microwave/imager observations  

NASA Technical Reports Server (NTRS)

We use retrievals of atmospheric precipitable water from satellite microwave observations and analyses of near-surface temperature to examine the relationship between these two fields on daily and longer time scales. The retrieval technique producing the data used here is most effective over the open ocean, so the analysis focuses on the southern hemisphere's extratropics, which have an extensive ocean surface. For both the total and the eddy precipitable water fields, there is a close correspondence between local variations in the precipitable water and near-surface temperature. The correspondence appears particularly strong for synoptic and planetary scale transient eddies. More specifically, the results support a typical modeling assumption that transient eddy moisture fields are proportional to transient eddy temperature fields under the assumption f constant relative humidity.

Gutowski, William J.; Lindemulder, Elizabeth A.; Jovaag, Kari

1995-01-01

304

Transport critical current measurement apparatus using liquid nitrogen cooled high-T(c) superconducting magnet with variable temperature insert.  

PubMed

We have developed an apparatus to investigate transport critical current (I(c)) as a function of magnetic field and temperature using only liquid nitrogen. The apparatus consists of a (Bi,Pb)(2)Sr(2)Ca(2)Cu(3)O(10) (Bi-2223) superconducting magnet, an outer dewar, and a variable temperature insert (VTI). The magnet, which is operated in depressurized liquid nitrogen, generates magnetic field up to 1.26 T. The sample is also immersed in liquid nitrogen. The pressure in the VTI is controlled from 0.02 to 0.3 MPa, which corresponds to temperature ranging from 66 to 88 K. We have confirmed the long-term stable operation of the Bi-2223 magnet at 1 T. The temperature stability of the sample at high transport current was also demonstrated. The apparatus provides easy-operating I(c) measurement environment for a high-T(c) superconductor up to 500 A in magnetic fields up to 1 T and in temperatures ranging from 66 to 88 K. PMID:23387701

Nishijima, G; Kitaguchi, H; Tshuchiya, Y; Nishimura, T; Kato, T

2013-01-01

305

Transport critical current measurement apparatus using liquid nitrogen cooled high-Tc superconducting magnet with variable temperature insert  

NASA Astrophysics Data System (ADS)

We have developed an apparatus to investigate transport critical current (Ic) as a function of magnetic field and temperature using only liquid nitrogen. The apparatus consists of a (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) superconducting magnet, an outer dewar, and a variable temperature insert (VTI). The magnet, which is operated in depressurized liquid nitrogen, generates magnetic field up to 1.26 T. The sample is also immersed in liquid nitrogen. The pressure in the VTI is controlled from 0.02 to 0.3 MPa, which corresponds to temperature ranging from 66 to 88 K. We have confirmed the long-term stable operation of the Bi-2223 magnet at 1 T. The temperature stability of the sample at high transport current was also demonstrated. The apparatus provides easy-operating Ic measurement environment for a high-Tc superconductor up to 500 A in magnetic fields up to 1 T and in temperatures ranging from 66 to 88 K.

Nishijima, G.; Kitaguchi, H.; Tshuchiya, Y.; Nishimura, T.; Kato, T.

2013-01-01

306

Latitude and Altitude Dependence of the Interannual Variability and Trends of Atmospheric Temperatures  

Microsoft Academic Search

--The 4-season (12-month) running means of temperatures at five atmospheric levels (surface, 850-300 mb, 300-100 mb, 100-50 mb, 100-30 mb) and seven climatic zones (60°N-90°N, 30°N-60°N, 10°N-30°N, 10°N-10°S, 10°S-30°S, 30°S-60°S, 60°S-90°S) showed QBO (Quasi-biennial Oscillation), QTO (Quasi-triennial Oscillation) and larger periodicities. For stratosphere and tropopause, the temperature variations near the equator and North Pole somewhat resembled the 50mb low latitude

R. P. Kane; R. A. Buriti

1997-01-01

307

Latitude and Altitude Dependence of the Interannual Variability and Trends of Atmospheric Temperatures  

Microsoft Academic Search

The 4-season (12-month) running means of temperatures at five atmospheric levels (surface, 850-300 mb, 300-100 mb, 100-50 mb, 100-30 mb) and seven climatic zones (60°N-90°N, 30°N-60°N, 10°N-30°N, 10°N-10°S, 10°S-30°S, 30°S-60°S, 60°S-90°S) showed QBO (Quasi-biennial Oscillation), QTO (Quasi-triennial Oscillation) and larger periodicities. For stratosphere and tropopause, the temperature variations near the equator and North Pole somewhat resembled the 50mb low latitude

R. P. Kane; R. A. Buriti

1997-01-01

308

Studies of hot photoluminescence in plasmonically coupled silicon via variable energy excitation and temperature-dependent spectroscopy.  

PubMed

By integrating silicon nanowires (?150 nm diameter, 20 ?m length) with an ?-shaped plasmonic nanocavity, we are able to generate broadband visible luminescence, which is induced by high order hybrid nanocavity-surface plasmon modes. The nature of this super bandgap emission is explored via photoluminescence spectroscopy studies performed with variable laser excitation energies (1.959 to 2.708 eV) and finite difference time domain simulations. Furthermore, temperature-dependent photoluminescence spectroscopy shows that the observed emission corresponds to radiative recombination of unthermalized (hot) carriers as opposed to a resonant Raman process. PMID:25120156

Aspetti, Carlos O; Cho, Chang-Hee; Agarwal, Rahul; Agarwal, Ritesh

2014-09-10

309

A YBCO RF-squid variable temperature susceptometer and its applications  

NASA Technical Reports Server (NTRS)

The Superconducting QUantum Interference Device (SQUID) susceptibility using a high-temperature radio-frequency (rf) SQUID and a normal metal pick-up coil is employed in testing weak magnetization of the sample. The magnetic moment resolution of the device is 1 x 10(exp -6) emu, and that of the susceptibility is 5 x 10(exp -6) emu/cu cm.

Zhou, Luwei; Qiu, Jinwu; Zhang, Xianfeng; Tang, Zhimin; Cai, Yimin; Qian, Yongjia

1991-01-01

310

Decadal Variability and Temperature Trends in the Middle Atmosphere From Historical Rocketsonde Data  

NASA Technical Reports Server (NTRS)

Observational studies were performed using historical rocketsonde data to investigate long-term temperature trends, solar-cycle variations, and interactions between tropical and extratropical latitudes in the middle atmosphere. Evidence from tropical, subtropical, and midlatitude North American rocketsonde stations indicated a consistent downward trend over 25 years, with a solar cycle component superposed. The trend is about -1.4 to -2.0 K per decade and the amplitude of the decadal oscillation is about 1.1 K. Prior to trend derivation it was necessary for us to correct temperatures for aerodynamic heating in the early years. The empirically derived correction profile agrees well with a theoretical profile of Krumins and Lyons. A study was also performed of the correlation between equatorial winds and north polar temperatures in winter, showing that the entire stratospheric wind profile near the equator -- including the quasi-biennial oscillation (QBO) and stratopause semiannual oscillation (SAO) -- is important to the extratropical flow, not merely the QBO component as previously thought. A strong correlation was discovered between winter polar temperatures and equatorial winds in the upper stratosphere during the preceding September, suggesting a role for the second cycle of the SAO.

Dunkerton, Timothy J.

2000-01-01

311

Water temperature as an indicator of environmental variability on a coral reef  

Microsoft Academic Search

The magnitude and spatial extent of variation in water temperatures commonly experienced by corals were examined on several temporal scales to evaluate the association between environmental stability and habitat favorability. Shallow reef-top sites were exposed to surface waters modified by prevailing weather conditions; the deeper outer slopes lay permanently within a well buffered, relatively oceanic water mass. Thermal stability and

D. C. POTTS; P. K. SWART

1984-01-01

312

Higher temperature variability increases the impact of Batrachochytrium dendrobatidis and shifts interspecific interactions in tadpole mesocosms  

PubMed Central

The emergence of amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd) has led to the decline and extinction of numerous amphibian species. Multiple studies have observed links between climatic factors and amphibian declines apparently caused by Bd. Using outdoor experimental mesocosms, we tested the response of red-legged frog (Rana aurora) tadpoles to increased variation in temperature, a component of climate linked to amphibian declines, and Bd exposure. We included tadpoles of a sympatric competitor species, Pacific chorus frog (Pseudacris regilla), in a fully factorial design to test the effects of Bd and temperature on interspecific interactions. We found that higher variation in temperature had numerous effects in mesocosms, including interacting with Bd presence to decrease the condition of R. aurora, shifting the relative performance of competing P. regilla and R. aurora, and accelerating the development of P. regilla relative to R. aurora. Our results demonstrate that increased variation in temperature can affect amphibians in multiple ways that will be contingent on ecological context, including the presence of Bd and competing species. PMID:23145331

Hamilton, Phineas T; Richardson, Jean ML; Govindarajulu, Purnima; Anholt, Bradley R

2012-01-01

313

Room Temperature Control During Season Switchover with Single Duct Variable Air Volume System Without Reheat  

E-print Network

of VAV boxes to maintain room temperature at their setpoints. The thermostat action is switched from direct acting (DA) to reverse acting (RA) when the season changes from fall to winter and vice versa from winter to spring, based on the out side air...

Liu, C.; Deng, S.; Claridge, D. E.; Turner, W. D.; Bruner, H.

2003-01-01

314

A variable temperature spectroscopic study on Paracoccuspantotrophus pseudoazurin: protein constraints on the blue Cu site.  

PubMed

The blue or Type 1 (T1) copper site of Paracoccuspantotrophus pseudoazurin exhibits significant absorption intensity in both the 450 and 600 nm regions. These are sigma and pi S(Cys) to Cu(2+) charge transfer (CT) transitions. The temperature dependent absorption, EPR, and resonance Raman (rR) vibrations enhanced by these bands indicate that a single species is present at all temperatures. This contrasts the temperature dependent behavior of the T1 center in nitrite reductase [S. Ghosh, X. Xie, A. Dey, Y. Sun, C. Scholes, E. Solomon, Proc. Natl. Acad. Sci. 106 (2009) 4969-4974] which has a thioether ligand that is unconstrained by the protein. The lack of temperature dependence in the T1 site in pseudoazurin indicates the presence of a protein constraint similar to the blue Cu site in plastocyanin where the thioether ligand is constrained at 2.8 A. However, plastocyanin exhibits only pi CT. This spectral difference between pseudoazurin and plastocyanin reflects a coupled distortion of the site where the axial thioether in pseudoazurin is also constrained, but at a shorter Cu-S(Met) bond length. This leads to an increase in the Cu(2+)-S(Cys) bond length, and the site undergoes a partial tetragonal distortion in pseudoazurin. Thus, its ground state wavefunction has both sigma and pi character in the Cu(2+)-S(Cys) bond. PMID:19481814

Xie, Xiangjin; Hadt, Ryan G; Pauleta, Sofia R; González, Pablo J; Un, Sun; Moura, Isabel; Solomon, Edward I

2009-10-01

315

Higher temperature variability increases the impact of Batrachochytrium dendrobatidis and shifts interspecific interactions in tadpole mesocosms.  

PubMed

The emergence of amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd) has led to the decline and extinction of numerous amphibian species. Multiple studies have observed links between climatic factors and amphibian declines apparently caused by Bd. Using outdoor experimental mesocosms, we tested the response of red-legged frog (Rana aurora) tadpoles to increased variation in temperature, a component of climate linked to amphibian declines, and Bd exposure. We included tadpoles of a sympatric competitor species, Pacific chorus frog (Pseudacris regilla), in a fully factorial design to test the effects of Bd and temperature on interspecific interactions. We found that higher variation in temperature had numerous effects in mesocosms, including interacting with Bd presence to decrease the condition of R. aurora, shifting the relative performance of competing P. regilla and R. aurora, and accelerating the development of P. regilla relative to R. aurora. Our results demonstrate that increased variation in temperature can affect amphibians in multiple ways that will be contingent on ecological context, including the presence of Bd and competing species. PMID:23145331

Hamilton, Phineas T; Richardson, Jean Ml; Govindarajulu, Purnima; Anholt, Bradley R

2012-10-01

316

Intra- to Multi-Decadal Temperature Variability over the Continental United States: 1896-2012  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o...

317

A CLIMATOLOGY OF TEMPERATURE AND PRECIPITATION VARIABILITY IN THE UNITED STATES  

EPA Science Inventory

This paper examines the seasonal and variance and standardized range for temperature and the seasonal end annual coefficient of variation and normalized standardized range for precipitation, on a climatic division level for the contiguous United States for the period 1895 to 1985...

318

Late Holocene variability of upper North Atlantic Deep Water temperature and salinity  

Microsoft Academic Search

Magnesium\\/calcium ratios in benthic foraminifera (Cibicidoides pachyderma) from a sediment core on the Laurentian Slope (1854 m) exhibit strong millennial-scale fluctuations during the past 4000 years. We convert these data to seawater paleotemperatures using a new monospecific linear equation. Results suggest that the temperature of upper North Atlantic Deep Water (dominated by Labrador Seawater today) has varied by at least

Thomas M. Marchitto; Peter B. deMenocal

2003-01-01

319

Late Holocene variability of upper North Atlantic Deep Water temperature and salinity  

Microsoft Academic Search

(1) Magnesium\\/calcium ratios in benthic foraminifera (Cibicidoides pachyderma) from a sediment core on the Laurentian Slope (1854 m) exhibit strong millennial-scale fluctuations during the past 4000 years. We convert these data to seawater paleotemperatures using a new monospecific linear equation. Results suggest that the temperature of upper North Atlantic Deep Water (dominated by Labrador Seawater today) has varied by at

Thomas M. Marchitto

2003-01-01

320

Reconstruction of seasonal temperature variability in the tropical Pacific Ocean from the shell of the scallop, Comptopallium radula  

NASA Astrophysics Data System (ADS)

We investigated the oxygen isotope composition (? 18O) of shell striae from juvenile Comptopallium radula (Mollusca; Pectinidae) specimens collected live in New Caledonia. Bottom-water temperature and salinity were monitored in-situ throughout the study period. External shell striae form with a 2-day periodicity in this scallop, making it possible to estimate the date of precipitation for each calcite sample collected along a growth transect. The oxygen isotope composition of shell calcite (? 18O shell calcite) measured at almost weekly resolution on calcite accreted between August 2002 and July 2003 accurately tracks bottom-water temperatures. A new empirical paleotemperature equation for this scallop species relates temperature and ? 18O shell calcite: t(°C)=20.00(±0.61)-3.66(±0.39)×(?18O-?18O) The mean absolute accuracy of temperature estimated using this equation is 1.0 °C at temperatures between 20 and 30 °C. Uncertainties regarding the precise timing of CaCO 3 deposition and the actual variations in ? 18O water at our study sites probably contribute to this error. Comparison with a previously published empirical paleotemperature equation indicates that C. radula calcite is enriched in 18O by ˜0.7‰ relative to equilibrium. Given the direction of this offset and the lack of correlation between shell growth rate and ? 18O shell calcite, this disequilibrium is unlikely to be related to kinetic isotope effects. We suggest that this enrichment reflects (1) a relatively low pH in the scallop's marginal extrapallial fluid (EPF), (2) an isotopic signature of the EPF different from that of seawater, or (3) Rayleigh fractionation during the biocalcification process. Relative changes in ? 18O shell calcite reflect seawater temperature variability at this location and we suggest that the shell of C. radula may be useful as an archive of past seawater temperatures.

Thébault, Julien; Chauvaud, Laurent; Clavier, Jacques; Guarini, Jennifer; Dunbar, Robert B.; Fichez, Renaud; Mucciarone, David A.; Morize, Eric

2007-02-01

321

Spatial and temporal variability of urban tree canopy temperature during summer 2010 in Berlin, Germany  

NASA Astrophysics Data System (ADS)

Trees form a significant part of the urban vegetation. Their meteorological and climatological effects at all scales in urban environments make them a flexible tool for creating a landscape oriented to the needs of an urban dweller. This study aims at quantifying the spatio-temporal patterns of canopy temperature ( T C) and canopy-to-air temperature difference (? T C) in relation to meteorological conditions and tree-specific (physiological) and urban site-specific characteristics. We observed T C and ? T C of 67 urban trees (18 species) using a high-resolution thermal-infrared (TIR) camera and meteorological measurements in the city of Berlin, Germany. TIR images were recorded at 1-min intervals over a period of 2 months from 1st July to 31st August 2010. The results showed that ? T C depends on tree species, leaf size and fraction of impervious surfaces. Average canopy temperature was nearly equal to air temperature. Species-specific maximum ?T C varied between 1.9 ± 0.3 K ( Populus nigra), 2.9 ± 0.3 K ( Quercus robur), 3.2 ± 0.5 K ( Fagus sylvatica), 3.9 ± 1.0 K ( Platanus acerifolia), 4.6 ± 0.2 K ( Acer pseudoplatanus), 5.0 ± 0.5 K ( A. platanoides) and 5.6 ± 1.1 K ( A. campestre). We analysed ? T C for a hot and dry period (A) and a warm and wet period (B). The range of species-specific ?T C at noon was nearly equal, i.e. 4.4 K for period A and 4.2 K for period B. Trees surrounded by high fraction of impervious surfaces showed consistently higher ? T C. Knowledge of species-specific canopy temperature and the impacts of urban structures are essential in order to optimise the benefits from trees in cities. However, comprehensive evaluation and optimisation should take the full range of climatological effects into account.

Meier, Fred; Scherer, Dieter

2012-12-01

322

Northern PMC brightness zonal variability and its correlation with temperature and water vapor  

NASA Astrophysics Data System (ADS)

mesospheric clouds (PMCs) measured by the Cloud Imaging and Particle Size instrument on the AIM satellite show strong zonal asymmetries, with prominent planetary-scale variations. The correlations between zonal variations of cloud brightness and temperature or water vapor (H2O) are determined in different stages of the PMC season. Aura Microwave Limb Sounder measured temperature and water vapor are used in the analysis. A zero-dimensional (0-D) PMC model was used to interpret the observation. Analyses of all days of the five northern seasons from 2007 to 2011 indicate that temperature and albedo daily zonal variations are anticorrelated in the season start and end, whereas in the core of the season the correlation is relatively poor. The albedo and H2O correlation in the zonal direction is poor throughout the season. Zero-dimensional model physics indicates that when clouds are weaker, or the environment is warmer and drier, temperature plays an increasingly important role in determining the cloud ice mass variation, which explains the stronger correlation of temperature and albedo at the start and end of the season. Water vapor takes a strong role in determining the ice mass variation in the core of the season when the clouds are stronger and the environment is colder and wetter. However, on a daily basis the H2O depletion associated with the ice production will lead to significant shift of the ice maxima and "post-ice" H2O maxima in the zonal direction, which leads to the poor correlation between the observed H2O and albedo.

Rong, P. P.; Russell, J. M.; Randall, C. E.; Bailey, S. M.; Lambert, A.

2014-03-01

323

Modeling the Temperature Responses to Spectral Solar Variability on Decadal and Centennial Time Scales  

NASA Astrophysics Data System (ADS)

Atmospheric temperature responses to decadal solar variations are computed for two scenarios of solar spectral irradiance (SSI), SIM-based out-of-phase and proxy-based in-phase variations, using a time-dependent radiative-convective model (RCM), and also GISS modelE (GCM.) For both scenarios and both models, maximum responses occur in upper stratosphere, decreasing downward to the surface. Upper stratospheric temperature peak-to-peak responses to out-of-phase forcing are ~0.6 K in RCM and ~0.9 K over tropics in GCM, ~5x as large as responses to in-phase forcing. Stratospheric responses are in-phase with TSI (Total Solar Irradiance). Modeled upper stratospheric temperature responses to SIM-based forcing are similar to 11-year temperature variations observed with HALOE (Halogen Occultation Experiment). For both RCM and GCM, surface responses to the two scenarios are significantly smaller than stratospheric responses. On centennial timescales, SSI variations are poorly known. However, two scenarios of reconstructed TSI, one based on 11-year cycle with background [Lean 2000] and the other on flux transport with much less background [Wang, Lean, and Sheeley, 2005], provide a potential range of TSI variations. We apply phase relations among different SSI bands both from SIM observations and proxy reconstructions to the two scenarios of historical TSI to derive associated historical SSI, which then drives the RCM. The updated atmosphere and ocean mixed coupled RCM including diffusion to deep-ocean provide a first order estimate of temperature responses to SSI variations on centennial time scales. We discuss potential mechanisms for atmosphere-ocean and stratosphere-troposphere couplings responsible for the climate responses to spectral solar variations.

Cahalan, R. F.; Wen, G.; Pilewskie, P.; Harder, J. W.

2010-12-01

324

Interannual variability of the Korea Strait Bottom Cold Water and its relationship with the upper water temperatures and atmospheric forcing in the Sea of Japan (East Sea)  

NASA Astrophysics Data System (ADS)

A 35 yearlong temperature data set is analyzed to investigate the long-term temperature variability in the Korea Strait and its relationship with the temperature variability in the upper layer of the Sea of Japan (East Sea). The second cyclostationary empirical orthogonal function mode of the vertical temperature section in the Korea Strait describes the interannual variability of the Korea Strait Bottom Cold Water (KSBCW). According to the corresponding principal component time series, the strength of the KSBCW fluctuates yearly with a major spectral peak around 3 years. Multiple regression analysis shows that the interannual KSBCW variability is closely linked with the temperature variability in the southwestern region of the Sea of Japan (East Sea) at about 50-100 m depth. Along 40°N, the source of the KSBCW is traced at about 50 m, extending eastward from the east coast of Korea to about 135°E. At 37°N, the source is traced at a deeper level (about 50-100 m), confined more toward the east coast of Korea with a hint of double core characteristics. The interannual KSBCW variability is also related to the southward wind stress along the east coast of Korea. It appears that strong cooling/warming of upper water temperature induced by the basin-scale wind stress results in the interannual KSBCW variability. This connection is verified by showing a reasonable interannual covariability between the KSBCW and the basin-scale wind stress.

Na, Hanna; Kim, Kwang-Yul; Chang, Kyung-Il; Kim, Kuh; Yun, Jae-Yul; Minobe, Shoshiro

2010-09-01

325

Intraseasonal Variability of the Equatorial Indian Ocean Observed from Sea Surface Height, Wind, and Temperature Data  

NASA Technical Reports Server (NTRS)

The forcing of the equatorial Indian Ocean by the highly periodic monsoon wind cycle creates many interesting intraseasonal variabilities. The frequency spectrum of the wind stress observations from the European Remote Sensing Satellite scatterometers reveals peaks at the seasonal cycle and its higher harmonics at 180, 120, 90, and 75 days. The observations of sea surface height (SSH) from the Jason and Ocean Topography Experiment (TOPEX)/Poseidon radar altimeters are analyzed to study the ocean's response. The focus of the study is on the intraseasonal periods shorter than the annual period. The semiannual SSH variability is characterized by a basin mode involving Rossby waves and Kelvin waves traveling back and forth in the equatorial Indian Ocean between 10(deg)S and 10(deg)N. However, the interference of these waves with each other masks the appearance of individual Kelvin and Rossby waves, leading to a nodal point (amphidrome) of phase propagation on the equator at the center of the basin. The characteristics of the mode correspond to a resonance of the basin according to theoretical models. The theory also calls for similar modes at 90 and 60 days.

Fu, Lee-Lueng

2007-01-01

326

An experimental UHV AFM-STM device for characterizing surface nanostructures under stress/strain at variable temperature.  

PubMed

A compression setup fully integrated in an ultra high vacuum chamber is presented. The system has been designed to combine in situ mechanical test together with near field microscopy at variable temperature, from 90 to 600 K. Compressive stress can be applied on the samples up to 500 MPa at different strain rates ranging from 10(-6) s(-1) to 10(-2) s(-1). The setup performances are highlighted through investigations on Au and Ni3(Al,Ta) single crystals. In particular, it is demonstrated that the high mechanical stability of the original apparatus allows us to follow in situ the evolution of the same area of interest over a large range of temperature and to keep the high spatial resolution offered by near field microscopy, even at high strain levels. PMID:24182173

Nahas, Y; Berneau, F; Bonneville, J; Coupeau, C; Drouet, M; Lamongie, B; Marteau, M; Michel, J; Tanguy, P; Tromas, C

2013-10-01

327

An experimental UHV AFM-STM device for characterizing surface nanostructures under stress/strain at variable temperature  

NASA Astrophysics Data System (ADS)

A compression setup fully integrated in an ultra high vacuum chamber is presented. The system has been designed to combine in situ mechanical test together with near field microscopy at variable temperature, from 90 to 600 K. Compressive stress can be applied on the samples up to 500 MPa at different strain rates ranging from 10-6 s-1 to 10-2 s-1. The setup performances are highlighted through investigations on Au and Ni3(Al,Ta) single crystals. In particular, it is demonstrated that the high mechanical stability of the original apparatus allows us to follow in situ the evolution of the same area of interest over a large range of temperature and to keep the high spatial resolution offered by near field microscopy, even at high strain levels.

Nahas, Y.; Berneau, F.; Bonneville, J.; Coupeau, C.; Drouet, M.; Lamongie, B.; Marteau, M.; Michel, J.; Tanguy, P.; Tromas, C.

2013-10-01

328

Variability and trends in dynamical forcing of tropical lower stratospheric temperatures  

NASA Astrophysics Data System (ADS)

The contribution of dynamical forcing to variations and trends in tropical lower stratospheric 70 hPa temperature for the period 1980-2011 is estimated based on ERA-Interim and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data. The dynamical forcing is estimated from the tropical mean residual upwelling calculated with the momentum balance equation, and with a simple proxy based on eddy heat fluxes averaged between 25° and 75° in both hemispheres. The thermodynamic energy equation with Newtonian cooling is used to relate the dynamical forcing to temperature. The deseasonalised, monthly mean time series of all four calculations are highly correlated (~ 0.85) with temperature for the period 1995-2011 when variations in radiatively active tracers are small. All four calculations provide additional support to previously noted prominent aspects of the temperature evolution 1980-2011: an anomalously strong dynamical cooling (~ -1 to -2 K) following the Pinatubo eruption that partially offsets the warming from enhanced aerosol, and a few years of enhanced dynamical cooling (~ -0.4 K) after October 2000 that contributes to the prominent drop in water entering the stratosphere at that time. The time series of dynamically forced temperature calculated with the same method are more highly correlated and have more similar trends than those from the same reanalysis but with different methods. For 1980-2011 (without volcanic periods), the eddy heat flux calculations give a dynamical cooling of ~ -0.1 to ~ -0.25 K decade-1 (magnitude sensitive to latitude belt considered and reanalysis), largely due to increasing high latitude eddy heat flux trends in September and December-January. The eddy heat flux trends also explain the seasonality of temperature trends very well, with maximum cooling in January-February. Trends derived from momentum balance calculations show near-zero annual mean dynamical cooling, with weaker seasonal trends especially in December-January. These contradictory results arising from uncertainties in data and methods are discussed and put in context to previous analyses.

Fueglistaler, S.; Abalos, M.; Flannaghan, T. J.; Lin, P.; Randel, W. J.

2014-12-01

329

Spatiotemporal variability of increasing temperature impacts on grassland vegetation along an elevation transect in the Alps  

NASA Astrophysics Data System (ADS)

Different manipulative approaches have been developed to study and quantify impacts of temperature increase on grassland ecosystems. Many of them share the problem of unwanted effects on the surrounding microclimatic conditions. Transplantation of grassland mesocosms along elevation gradients can be a realistic alternative, although with some restrictions. Here we present 3 years of data from a double-transplant-experiment, were 70*70*20cm grassland turves were transplanted at two elevations from 2000m to 1500m a.s.l. and from 1500m to 1000m a.s.l. respectively, along an inner-alpine elevation gradient in the Vinschgau Valley (South Tyrol, I). All donor and receiving sites are comparable regarding land use (meadows), soil conditions or exposition and are located within a few km's distance ensuring comparable weather conditions apart from the intended air temperature (0.54°K/100m) and annual precipitation (20mm/100m) lapse rate. Phytodiversity and above ground net primary production (ANPP) of the transplanted mesocosms were assessed and compared with locally transplanted monoliths of the respective donor site. Furthermore, growth dynamics was continuously observed throughout the vegetation season with a non-destructive method based on measurement of light (photosynthetic active radiation) extinction within the canopy. After 3 years no significant changes in absolute species numbers has been detected at all, whereas slight variations have been observed regarding species composition. Those shifts could be differentiated both to transplantation artifacts and effects of the elevated temperature. Total aboveground phytomass, unsurprisingly, showed higher values on transplanted (lower) mesocosms, however: data from single cuts and growth rate analysis reveal differing effects between the two transplantation steps as well as over the course of the vegetation period. Transplanted plots from 2000m to 1500m showed continuously higher productivity from spring to autumn, whereas on the lower transplants (from 1500m to 1000m) during summer months the temperature benefit gets balanced by higher evapotranspiration rates, resulting in more frequent drought stress. Summarizing, gained experiences confirm well-designed transplant approach to be an interesting alternative for mid- to longterm simulations of future climate conditions in grassland ecosystems. Furthermore, results indicate that the impact of increasing temperatures in the studied grassland highly depends on elevation and acts rather by a prolongation of the vegetation period than by elevated summer temperatures.

Niedrist, Georg; Obojes, Nikolaus; Bertoldi, Giacomo; Della Chiesa, Stefano; Tasser, Erich; Tappeiner, Ulrike

2013-04-01

330

Large-scale sea surface temperature variability from satellite and shipboard measurements  

NASA Technical Reports Server (NTRS)

A series of satellite sea surface temperature intercomparison workshops were conducted under NASA sponsorship at the Jet Propulsion Laboratory. Three different satellite data sets were compared with each other, with routinely collected ship data, and with climatology, for the months of November 1979, December 1981, March 1982, and July 1982. The satellite and ship data were differenced against an accepted climatology to produce anomalies, which in turn were spatially and temporally averaged into two-degree latitude-longitude, one-month bins. Monthly statistics on the satellite and ship bin average temperatures yielded rms differences ranging from 0.58 to 1.37 C, and mean differences ranging from -0.48 to 0.72 C, varying substantially from month to month, and sensor to sensor.

Bernstein, R. L.; Chelton, D. B.

1985-01-01

331

Structure of temperature variability in the high latitudes of the Northern Hemisphere  

Microsoft Academic Search

The spatial structure of surface air temperature (SAT) anomalies in the extratropical latitudes of the Northern Hemisphere\\u000a (NH) during the 20th century is studied from the data obtained over the period 1892–1999. The expansion of the mean (over\\u000a the winter and summer periods) SAT anomalies into empirical orthogonal functions (EOFs) is used for analysis. It is shown\\u000a that variations in

V. A. Semenov

2007-01-01

332

Variable temperature sensitivity of soil organic carbon in North American forests  

Microsoft Academic Search

We investigated mean residence time (MRT) for soil organic carbon (SOC) sampled from paired hardwood and pine forests located along a 221C mean annual temperature (MAT) gradient in North America. We used acid hydrolysis fractionation, radiocarbon analyses, long-term laboratory incubations (525-d), and a three-pool model to describe the size and kinetics of the acid insoluble C (AIC), active and slow

CINZIA F ISSORE; C HRISTIAN; C HRISTOPHER; GARY M. K ING; R ANDALL K. K OLKA

2009-01-01

333

Sexual reproduction of the scyphomedusa Aurelia aurita in relation to temperature and variable food supply  

Microsoft Academic Search

The effects of food availability and temperature on sexual maturation and female reproductive output of the scyphomedusa\\u000a Aurelia aurita was examined in two populations from the contrasting environments of Southampton Water and Horsea Lake, England. Trends in\\u000a oogenesis and subsequent reproductive output differed markedly between the two populations. In Southampton Water, the onset\\u000a of sexual maturation occurred earliest in the

C. H. Lucas; S. Lawes

1998-01-01

334

Aircraft observations of sea surface temperature variability in the tropical Pacific  

Microsoft Academic Search

During the southern summer of 1992-1993, a series of aircraft observations of sea surface temperature (SST) were obtained over the tropical western Pacific ocean as part of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Down-looking thermal infrared (10-11 mum) observations of the sea surface, coincident with uplooking infrared observations (9-11 mum) and meteorological measurements from the

Denise Hagan; David Rogers; Carl Friehe; Robert Weller; Edward Walsh

1997-01-01

335

Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp  

Microsoft Academic Search

The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane.

LYLE G. WHYTE; JALAL HAWARI; EDWARD ZHOU; LUC BOURBONNIERE; C. W. Greer; W. E. Inniss

1998-01-01

336

Ocean rises are products of variable mantle composition, temperature and focused melting  

NASA Astrophysics Data System (ADS)

Ocean ridges, where Earth's tectonic plates are pulled apart, range from more than 5-km depth in the Arctic to 750 m above sea level in Iceland. This huge relief is generally attributed to mantle plumes underlying mantle hotspots--areas of voluminous volcanism marked by ocean islands. The plumes are thought to feed the mantle beneath adjacent ocean ridges. This process results in thickened crust and ridge elevation to form ocean rises. The composition of mid-ocean ridge basalt, a direct function of mantle composition and temperature, varies systematically along ocean rises, but in a unique way for each different rise. Here we use thermodynamic calculations of melt-evolution pathways to show that variations in both mantle temperature and source composition are required to explain the chemical make-up of rise basalts. Thus, lateral gradients in mantle temperature cannot be uniquely determined from basalt chemistry, and ocean rises can be supported by chemically buoyant mantle or by robust mantle plumes. Our calculations also indicate that melt is conserved and focused by percolative flow towards the overlying ridge, progressively interacting with the mantle to shallow depth. We conclude that most mantle melting occurs by an overlooked mechanism, focused melting, whereas fractional melting is a secondary process that is important largely at shallow depth.

Dick, Henry J. B.; Zhou, Huaiyang

2015-01-01

337

Holocene sea-surface temperature variability in the Chilean fjord region  

NASA Astrophysics Data System (ADS)

Here we provide three new Holocene (11-0 cal ka BP) alkenone-derived sea surface temperature (SST) records from the southernmost Chilean fjord region (50-53°S). SST estimates may be biased towards summer temperature in this region, as revealed by a large set of surface sediments. The Holocene records show consistently warmer than present-day SSTs except for the past ~ 0.6 cal ka BP. However, they do not exhibit an early Holocene temperature optimum as registered further north off Chile and in Antarctica. This may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea-level stands, enhanced advection of colder and fresher inner fjord waters, and stronger westerly winds. During the mid-Holocene, pronounced short-term variations of up to 2.5°C and a cooling centered at ~ 5 cal ka BP, which coincides with the first Neoglacial glacier advance in the Southern Andes, are recorded. The latest Holocene is characterized by two pronounced cold events centered at ~ 0.6 and 0.25 cal ka BP, i.e., during the Little Ice Age. These cold events have lower amplitudes in the offshore records, suggesting an amplification of the SST signal in the inner fjords.

Caniupán, Magaly; Lamy, Frank; Lange, Carina B.; Kaiser, Jérôme; Kilian, Rolf; Arz, Helge W.; León, Tania; Mollenhauer, Gesine; Sandoval, Susana; De Pol-Holz, Ricardo; Pantoja, Silvio; Wellner, Julia; Tiedemann, Ralf

2014-09-01

338

Trap density of states in n-channel organic transistors: variable temperature characteristics and band transport  

SciTech Connect

We have investigated trap density of states (trap DOS) in n-channel organic field-effect transistors based on N,N?’-bis(cyclohexyl)naphthalene diimide (Cy-NDI) and dimethyldicyanoquinonediimine (DMDCNQI). A new method is proposed to extract trap DOS from the Arrhenius plot of the temperature-dependent transconductance. Double exponential trap DOS are observed, in which Cy-NDI has considerable deep states, by contrast, DMDCNQI has substantial tail states. In addition, numerical simulation of the transistor characteristics has been conducted by assuming an exponential trap distribution and the interface approximation. Temperature dependence of transfer characteristics are well reproduced only using several parameters, and the trap DOS obtained from the simulated characteristics are in good agreement with the assumed trap DOS, indicating that our analysis is self-consistent. Although the experimentally obtained Meyer-Neldel temperature is related to the trap distribution width, the simulation satisfies the Meyer-Neldel rule only very phenomenologically. The simulation also reveals that the subthreshold swing is not always a good indicator of the total trap amount, because it also largely depends on the trap distribution width. Finally, band transport is explored from the simulation having a small number of traps. A crossing point of the transfer curves and negative activation energy above a certain gate voltage are observed in the simulated characteristics, where the critical V{sub G} above which band transport is realized is determined by the sum of the trapped and free charge states below the conduction band edge.

Cho, Joung-min, E-mail: cho.j.ad@m.titech.ac.jp; Akiyama, Yuto; Kakinuma, Tomoyuki [Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Tokyo 152-8552 (Japan)] [Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Tokyo 152-8552 (Japan); Mori, Takehiko [Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Tokyo 152-8552 (Japan) [Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Tokyo 152-8552 (Japan); ACT-C, JST, Honcho, Kawaguchi, Saitama 332-0012 (Japan)

2013-10-15

339

Variability and trends in dynamical forcing of tropical lower stratospheric temperatures  

NASA Astrophysics Data System (ADS)

We analyse the relation between tropical lower stratospheric temperatures and dynamical forcing over the period 1980-2011 using NCEP, MERRA and ERA-Interim reanalyses. The tropical mean thermodynamic energy equation with Newtonian cooling for radiation is forced with two dynamical predictors: (i) the average eddy heat flux of both hemispheres; and (ii) tropical upwelling estimated from momentum balance following Randel et al. (2002). The correlation (1995-2011) for deseasonalised tropical average temperatures at 70 hPa with the eddy heat flux based predictor is 0.84 for ERA-Interim (0.77 for the momentum balance calculation), and 0.87 for MERRA. The eddy heat flux based predictor indicates a dynamically forced cooling of the tropics of ∼-0.1 K decade-1 (∼-0.2 K decade-1 excluding volcanic periods) for the period 1980-2011 in MERRA and ERA-Interim. ERA-Interim eddy heat fluxes drift slightly relative to MERRA in the 2000's, possibly due to onset of GPS temperature data assimilation. While NCEP gives a small warming trend, all 3 reanalyses show a similar seasonality, with strongest cooling in January/February (∼-0.4 K decade-1, from northern hemispheric forcing) and October (∼-0.3 K decade-1, from southern hemispheric forcing). Months preceding and following the peaks in cooling trends show pronounced smaller, or even warming, trends. Consequently, the seasonality in the trends arises in part due to a temporal shift in eddy activity. Over all months, the Southern Hemisphere contributes more to the tropical cooling in both MERRA and ERA-Interim. The residual time series (observed minus estimate of dynamically forced temperature) are well correlated between ERA-Interim and MERRA, with differences largely due to temperature differences. The residual time series is dominated by the modification of the radiative balance by volcanic aerosol following the eruption of El Chichon (maximum warming of ∼3 K at 70 hPa) and Pinatubo (maximum warming of ∼4 K at 70 hPa), with a strong dynamical response during Pinatubo partially masking the aerosol heating.

Fueglistaler, S.; Abalos, M.; Flannaghan, T. J.; Lin, P.; Randel, W. J.

2014-05-01

340

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition.  

PubMed

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO(2)), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO(2) that is based on the ratio of Fe and FeO [called "?IW (ratio)" hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO(2) + O(2) = Fe(2)SiO(4) to calculate absolute fO(2) and relative to the iron-wüstite (IW) buffer at pressure and temperature [?IW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ?IW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ?IW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100?°C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO(2) in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO(2) may evolve from high to low fO(2) during Earth (and other differentiated bodies) accretion. Any modeling of core formation and metal-silicate equilibrium should take these effects into account. PMID:22778438

Righter, K; Ghiorso, M S

2012-07-24

341

Horizontal Temperature Variability in the Stratosphere: Global Variations Inferred from CRISTA Data  

NASA Technical Reports Server (NTRS)

In two separate orbital campaigns (November, 1994 and August, 1997), the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument acquired global stratospheric data of high accuracy and high spatial resolution. The standard limb-scanned CRISTA measurements resolved atmospheric spatial structures with vertical dimensions greater than or equal to 1.5 - 2 km and horizontal dimensions is greater than or equal to 100 - 200 km. A fluctuation analysis of horizontal temperature distributions derived from these data is presented. This method is somewhat complementary to conventional power-spectral analysis techniques.

Eidmann, G.; Offermann, D.; Jarisch, M.; Preusse, P.; Eckermann, S. D.; Schmidlin, F. J.

2001-01-01

342

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition  

PubMed Central

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO2), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO2 that is based on the ratio of Fe and FeO [called “?IW (ratio)” hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO2 + O2 = Fe2SiO4 to calculate absolute fO2 and relative to the iron-wüstite (IW) buffer at pressure and temperature [?IW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ?IW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ?IW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100?°C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO2 in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO2 may evolve from high to low fO2 during Earth (and other differentiated bodies) accretion. Any modeling of core formation and metal-silicate equilibrium should take these effects into account. PMID:22778438

Righter, K.; Ghiorso, M. S.

2012-01-01

343

X-Ray Spectroscopy of II Pegasi: Coronal Temperature Structure, Abundances, and Variability  

E-print Network

We have obtained high resolution X-ray spectra of the coronally active binary, II Pegasi (HD 224085), covering the wavelength range of 1.5-25 Angstroms. For the first half of our 44 ksec observation, the source was in a quiescent state with constant X-ray flux, after which it flared, reaching twice the quiescent flux in 12 ksec, then decreasing. We analyze the emission-line spectrum and continuum during quiescent and flaring states. The differential emission measure derived from lines fluxes shows a hot corona with a continuous distribution in temperature. During the non-flare state, the distribution peaks near log T = 7.2, and when flaring, near 7.6. High-temperature lines are enhanced slightly during the flare, but most of the change occurs in the continuum. Coronal abundance anomalies are apparent, with iron very deficient relative to oxygen and significantly weaker than expected from photospheric measurements, while neon is enhanced relative to oxygen. We find no evidence of appreciable resonant scattering optical depth in line ratios of iron and oxygen. The flare light curve is consistent with Solar two-ribbon flare models, but with a very long reconnection time-constant of about 65 ks. We infer loop lengths of about 0.05 stellar radii, to about 0.25 in the flare, if the flare emission originated from a single, low-density loop.

David P. Huenemoerder; Claude R. Canizares; Norbert S. Schulz

2001-06-01

344

Land use change exacerbates tropical South American drought by sea surface temperature variability  

NASA Astrophysics Data System (ADS)

Observations of tropical South American precipitation over the last three decades indicate an increasing rainfall trend to the north and a decreasing trend to the south. Given that tropical South America has experienced significant land use change over the same period, it is of interest to assess the extent to which changing land use may have contributed to the precipitation trends. Simulations of the National Center for Atmospheric Research Community Atmosphere Model (NCAR CAM3) analyzed here suggest a non-negligible impact of land use on this precipitation behavior. While forcing the model by imposed historical sea surface temperatures (SSTs) alone produces a plausible north-south precipitation dipole over South America, NCAR CAM substantially underestimates the magnitude of the observed southern decrease in rainfall unless forcing associated with human-induced land use change is included. The impact of land use change on simulated precipitation occurs primarily during the local dry season and in regions of relatively low annual-mean rainfall, as the incidence of very low monthly-mean accumulations (<10 mm/month) increases significantly when land use change is imposed. Land use change also contributes to the simulated temperature increase by shifting the surface turbulent flux partitioning to favor sensible over latent heating. Moving forward, continuing pressure from deforestation in tropical South America will likely increase the occurrence of significant drought beyond what would be expected by anthropogenic warming alone and in turn compound biodiversity decline from habitat loss and fragmentation.

Lee, Jung-Eun; Lintner, Benjamin R.; Boyce, C. Kevin; Lawrence, Peter J.

2011-10-01

345

Processes of 30-90 days sea surface temperature variability in the northern Indian Ocean during boreal summer  

NASA Astrophysics Data System (ADS)

During summer, the northern Indian Ocean exhibits significant atmospheric intraseasonal variability associated with active and break phases of the monsoon in the 30-90 days band. In this paper, we investigate mechanisms of the Sea Surface Temperature (SST) signature of this atmospheric variability, using a combination of observational datasets and Ocean General Circulation Model sensitivity experiments. In addition to the previously-reported intraseasonal SST signature in the Bay of Bengal, observations show clear SST signals in the Arabian Sea related to the active/break cycle of the monsoon. As the atmospheric intraseasonal oscillation moves northward, SST variations appear first at the southern tip of India (day 0), then in the Somali upwelling region (day 10), northern Bay of Bengal (day 19) and finally in the Oman upwelling region (day 23). The Bay of Bengal and Oman signals are most clearly associated with the monsoon active/break index, whereas the relationship with signals near Somali upwelling and the southern tip of India is weaker. In agreement with previous studies, we find that heat flux variations drive most of the intraseasonal SST variability in the Bay of Bengal, both in our model (regression coefficient, 0.9, against ~0.25 for wind stress) and in observations (0.8 regression coefficient); ~60% of the heat flux variation is due do shortwave radiation and ~40% due to latent heat flux. On the other hand, both observations and model results indicate a prominent role of dynamical oceanic processes in the Arabian Sea. Wind-stress variations force about 70-100% of SST intraseasonal variations in the Arabian Sea, through modulation of oceanic processes (entrainment, mixing, Ekman pumping, lateral advection). Our ~100 km resolution model suggests that internal oceanic variability (i.e. eddies) contributes substantially to intraseasonal variability at small-scale in the Somali upwelling region, but does not contribute to large-scale intraseasonal SST variability due to its small spatial scale and random phase relation to the active-break monsoon cycle. The effect of oceanic eddies; however, remains to be explored at a higher spatial resolution.

Vialard, J.; Jayakumar, A.; Gnanaseelan, C.; Lengaigne, M.; Sengupta, D.; Goswami, B. N.

2012-05-01

346

Orbital and suborbital variability in North Atlantic bottom water temperature obtained from deep-sea ostracod Mg/Ca ratios  

USGS Publications Warehouse

Magnesium/calcium (Mg/Ca) ratios were measured in the deep-sea ostracod (Crustacea) genus Krithe from Chain core 82-24-4PC from the western mid-Atlantic Ridge (3427 m) in order to estimate ocean circulation and bottom water temperature (BWT) variability over the past 200,000 years. Mg/Ca ratios have been used as a paleothermometer because the ratios are controlled primarily by ambient water temperatures at the time the organism secretes its adult carapace. Over the past two glacial-interglacial cycles, Mg/Ca values oscillated between about 7 mmol/mol and 12 mmol/mol, equivalent to a BWT range of 0 to > 3.5??C. The lowest values were obtained on specimens from glacial marine isotope stages (MISs) 2, 4 and 6; the highest values were obtained from specimens from the early part of the Holocene interglacial (MIS 1), and also from MISs 5 and 7. These trends suggest that BWTs in the North Atlantic Ocean fluctuate over orbital time scales. Suborbital variability in Mg/Ca ratios and BWT was also observed for the past 100,000 years. Ratios rose from ~8 mmol/mol to ~10 mmol/mol (implying a BWT increase of ~1 to 3??C) during 14 Mg/Ca excursions. The highest ratios were found in Krithe dated at approximately 32, 36-38, 43, 48, 73, 85 and 93 ka. Although the age model for the Chain 82-24-4PC and temporal resolution do not allow precise correlation, some of these deep-sea bottom temperature excursions appear to correspond to Heinrich events recorded in other regions of the North Atlantic and perhaps Dansgaard-Oeschger interstadial events recorded in Greenland ice cores. If confirmed, this would support the hypothesis that millennial-scale oscillations of climate in the North Atlantic are capable of affecting global climate via thermohaline circulation changes. (C) 2000 Elsevier Science B.V.

Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; DeMartino, D.M.

2000-01-01

347

Seasonality of sporadic physical processes driving temperature and nutrient high-frequency variability in the coastal ocean off southeast Australia  

NASA Astrophysics Data System (ADS)

Physical processes forced by alongshore winds and currents are known to strongly influence the biogeochemistry of coastal waters. Combining in situ observations (moored platforms, hydrographic surveys) and satellite data (sea surface wind and sea surface height), we investigate the transient occurrence of wind-driven upwelling/downwelling and current-driven upwelling events off southeast Australia. Remote-sensed indices are developed and calibrated with multiannual time series of in situ temperature and current measurements at two shelf locations. Based on archives up to 10 years long, climatological analyses of these indices reveal various latitudinal regimes with respect to seasonality, magnitude, duration of events, and their driving mechanisms (wind or current). Generally, downwelling-favorable winds prevail in this region; however, we demonstrate that up to 10 wind-driven upwelling days per month occur during spring/summer at 28-33.5°S and up to 5 days in summer further south. Current-driven upwelling upstream of the East Australian Current separation zone (˜32°S) occurs twice as often as downstream. Using independent in situ data sets, we show that the response of the coastal ocean is consistent with our climatology of shelf processes: upwelling leads to a large range of temperatures and elevated nutrient concentrations on the shelf, maximized in the wind-driven case, while downwelling results in destratified nutrient-poor waters. The combination of these sporadic wind- and current-driven processes may drive an important part of the high-frequency variability of coastal temperature and nutrient content. Our results suggest that localized nutrient enrichment events of variable magnitude are favored at specific latitudes and seasons, potentially impacting coastal ecosystems.

Rossi, Vincent; Schaeffer, Amandine; Wood, Julie; Galibert, Guillaume; Morris, Brad; Sudre, Joel; Roughan, Moninya; Waite, Anya M.

2014-01-01

348

The variability time-scales and brightness temperatures of radio flares from stars to supermassive black holes  

NASA Astrophysics Data System (ADS)

In this paper we compile the analysis of ˜200 synchrotron flare events from ˜90 distinct objects/events for which the distance is well established, and hence the peak luminosity can be accurately estimated. For each event we measure this peak and compare it to the rise and decay time-scales, as fit by exponential functions, which allows us in turn to estimate a minimum brightness temperature for all the events. The astrophysical objects from which the flares originate vary from flare stars to supermassive black holes in active galactic nuclei, and include both repeating phenomena and single cataclysmic events (such as supernovae and gamma-ray burst afterglows). The measured time-scales vary from minutes to longer than years, and the peak radio luminosities range over 22 orders of magnitude. Despite very different underlying phenomena, including relativistic and non-relativistic regimes, and highly collimated versus isotropic phenomena, we find a broad correlation between peak radio luminosity and rise/decay time-scales, approximately of the form L ? ?5. This rather unexpectedly demonstrates that the estimated minimum brightness temperature, when based upon variability time-scales, and with no attempt to correct for relativistic boosting, is a strongly rising function of source luminosity. It furthermore demonstrates that variability time-scales could be used as an early diagnostic of source class in future radio transient surveys. As an illustration of radio transients parameter space, we compare the synchrotron events with coherent bursts at higher brightness temperatures to illustrate which regions of radio transient parameter space have been explored.

Pietka, M.; Fender, R. P.; Keane, E. F.

2015-02-01

349

Analysis of the variability of temperature gradient in the ocean frontal zones based on satellite data  

NASA Astrophysics Data System (ADS)

AVHRR MCSST data for the periods 1982-2000 (mean weekly data) were used to calculate mean gradient fields in the ocean for different periods of time. Three-month averaged sea surface temperature gradients (SSTG) and their mean seasonal variations have been studied for 25 points in the large-scale oceanic fronts zones. Major oceanic fronts in the Atlantic and Pacific have been identified and compared in literature. In the North Atlantic and Pacific, the areas under study were the North Polar Front and Subpolar Fronts. In the South Atlantic and Pacific we studied the region of the Antarctic Circumpolar Current (ACC) and the fronts formed by this current, known as the South Polar Front, and the Subantarctic Front. SSTG were also calculated for El Niño (Southeast Pacific) and Benguela Current (Southeast Atlantic). In warm periods seasonal SSTG in the North Atlantic markedly increased and exhibit some interannual cycles. The correlation between the North Atlantic Oscillation index and seasonal SSTG for a single point in the Gulf Stream zone can be the key point for evaluation of heat transfer by the currents to the coast of East Europe. In the Southern Atlantic, the SSTG values are low during the cold period (summer in the southern hemisphere) in the ACC zone and increase in the warm season (winter in the southern hemisphere). It also exhibits interannual cycles. In the Northwest Pacific for some points in the Subpolar Front the SSTG values are high in the cold period (winter). Here at seven points in the spring of 1993 and 2000 the calculations disclosed significant increase of the gradient. In these years, the anomalous SSTG in Subpolar Front and South Polar Front were found to vary synchronously in both hemispheres, with maximum intensity in spring (North Pacific) and in summer (South Pacific). Mean annual SSTG in the El Niño zone and south oscillation index have been found to exhibit some correlation. Major jet currents periodically form high-gradient temperature fields and from the temperature satellite data we can derive information about variation in the large-scale fronts in the Global Ocean.

Kartushinsky, A. V.; Sidorenko, A. Y.

2013-10-01

350

Efficient method for predicting crystal structures at finite temperature: variable box shape simulations.  

PubMed

We present an efficient and robust method based on Monte Carlo simulations for predicting crystal structures at finite temperature. We apply this method, which is surprisingly easy to implement, to a variety of systems, demonstrating its effectiveness for hard, attractive, and anisotropic interactions, binary mixtures, semi-long-range soft interactions, and truly long-range interactions where the truly long-range interactions are treated using Ewald sums. In the case of binary hard-sphere mixtures, star polymers, and binary Lennard-Jones mixtures, the crystal structures predicted by this algorithm are consistent with literature, providing confidence in the method. Finally, we predict new crystal structures for hard asymmetric dumbbell particles, bowl-like particles and hard oblate cylinders and present the phase diagram for the oblate cylinders based on full free energy calculations. PMID:19905838

Filion, Laura; Marechal, Matthieu; van Oorschot, Bas; Pelt, Daniël; Smallenburg, Frank; Dijkstra, Marjolein

2009-10-30

351

Caspian Sea surface circulation variability inferred from satellite altimeter and sea surface temperature  

NASA Astrophysics Data System (ADS)

(1993-2007) satellite-derived Sea Level Anomaly (SLA), Sea Surface Temperature (SST), and model-derived mean dynamic topography were used together to analyze climatological and interannual variations of the Caspian Sea surface circulation. Constructed geostrophic currents are in good agreement with the known circulation features of the Caspian Sea, obtained from models and verified by some drifter observations. It is shown that the climatological surface circulation of the Middle Caspian Sea (MCS) is dominated by a basin-wide cyclonic circulation in winter, switching to an anticyclonic circulation in summer. A dipole pattern (an anticyclonic eddy near 39.5°N and a cyclonic one near 38°N) exist in the Southern Caspian Sea (SCS) (stronger from September to January). Evaluation of the multiyear geostrophic velocities shows that the Caspian Sea surface circulation exhibits strong interannual variations, with the location and intensity of the circulation patterns changing from one year to another.

Gunduz, Murat

2014-02-01

352

Jovian temperature and cloud variability during the 2009-2010 fade of the South Equatorial Belt  

NASA Astrophysics Data System (ADS)

Mid-infrared 7-20 ?m imaging of Jupiter from ESO's Very Large Telescope (VLT/VISIR) demonstrate that the increased albedo of Jupiter's South Equatorial Belt (SEB) during the 'fade' (whitening) event of 2009-2010 was correlated with changes to atmospheric temperature and aerosol opacity. The opacity of the tropospheric condensation cloud deck at pressures less than 800 mbar increased by 80% between May 2008 and July 2010, making the SEB (7-17°S) as opaque in the thermal infrared as the adjacent equatorial zone. After the cessation of discrete convective activity within the SEB in May 2009, a cool band of high aerosol opacity (the SEB zone at 11-15°S) was observed separating the cloud-free northern and southern SEB components. The cooling of the SEBZ (with peak-to-peak contrasts of 1.0 ± 0.5 K), as well as the increased aerosol opacity at 4.8 and 8.6 ?m, preceded the visible whitening of the belt by several months. A chain of five warm, cloud-free 'brown barges' (subsiding airmasses) were observed regularly in the SEB between June 2009 and June 2010, by which time they too had been obscured by the enhanced aerosol opacity of the SEB, although the underlying warm circulation was still present in July 2010. Upper tropospheric temperatures (150-300 mbar) remained largely unchanged during the fade, but the cool SEBZ formation was detected at deeper levels ( p > 300 mbar) within the convectively-unstable region of the troposphere. The SEBZ formation caused the meridional temperature gradient of the SEB to decrease between 2008 and 2010, reducing the vertical thermal windshear on the zonal jets bounding the SEB. The southern SEB had fully faded by July 2010 and was characterised by short-wave undulations at 19-20°S. The northern SEB persisted as a narrow grey lane of cloud-free conditions throughout the fade process. The cool temperatures and enhanced aerosol opacity of the SEBZ after July 2009 are consistent with an upward flux of volatiles (e.g., ammonia-laden air) and enhanced condensation, obscuring the blue-absorbing chromophore and whitening the SEB by April 2010. These changes occurred within cloud decks in the convective troposphere, and not in the radiatively-controlled upper troposphere. NH 3 ice coatings on aerosols at p < 800 mbar are plausible sources of the suppressed 4.8 and 8.6-?m emission, although differences in the spatial distribution of opacity at these two wavelengths suggest that enhanced attenuation by a deeper cloud ( p > 800 mbar) also occurred during the fade. Revival of the dark SEB coloration in the coming months will ultimately require sublimation of these ices by subsidence and warming of volatile-depleted air.

Fletcher, Leigh N.; Orton, G. S.; Rogers, J. H.; Simon-Miller, A. A.; de Pater, I.; Wong, M. H.; Mousis, O.; Irwin, P. G. J.; Jacquesson, M.; Yanamandra-Fisher, P. A.

2011-06-01

353

Temperature variability analysis using wavelets and multiscale entropy in patients with systemic inflammatory response syndrome, sepsis, and septic shock  

PubMed Central

Background Even though temperature is a continuous quantitative variable, its measurement has been considered a snapshot of a process, indicating whether a patient is febrile or afebrile. Recently, other diagnostic techniques have been proposed for the association between different properties of the temperature curve with severity of illness in the Intensive Care Unit (ICU), based on complexity analysis of continuously monitored body temperature. In this study, we tried to assess temperature complexity in patients with systemic inflammation during a suspected ICU-acquired infection, by using wavelets transformation and multiscale entropy of temperature signals, in a cohort of mixed critically ill patients. Methods Twenty-two patients were enrolled in the study. In five, systemic inflammatory response syndrome (SIRS, group 1) developed, 10 had sepsis (group 2), and seven had septic shock (group 3). All temperature curves were studied during the first 24 hours of an inflammatory state. A wavelet transformation was applied, decomposing the signal in different frequency components (scales) that have been found to reflect neurogenic and metabolic inputs on temperature oscillations. Wavelet energy and entropy per different scales associated with complexity in specific frequency bands and multiscale entropy of the whole signal were calculated. Moreover, a clustering technique and a linear discriminant analysis (LDA) were applied for permitting pattern recognition in data sets and assessing diagnostic accuracy of different wavelet features among the three classes of patients. Results Statistically significant differences were found in wavelet entropy between patients with SIRS and groups 2 and 3, and in specific ultradian bands between SIRS and group 3, with decreased entropy in sepsis. Cluster analysis using wavelet features in specific bands revealed concrete clusters closely related with the groups in focus. LDA after wrapper-based feature selection was able to classify with an accuracy of more than 80% SIRS from the two sepsis groups, based on multiparametric patterns of entropy values in the very low frequencies and indicating reduced metabolic inputs on local thermoregulation, probably associated with extensive vasodilatation. Conclusions We suggest that complexity analysis of temperature signals can assess inherent thermoregulatory dynamics during systemic inflammation and has increased discriminating value in patients with infectious versus noninfectious conditions, probably associated with severity of illness. PMID:22424316

2012-01-01

354

Late Quaternary Temperature Variability in the Benguela Current System Derived from Alkenones  

NASA Astrophysics Data System (ADS)

Three sediment cores on a transect across the continental slope off Namibia at about 23°S were investigated for alkenone-derived past sea-surface temperature (SST) and total organic carbon (TOC) content. These records are used to reconstruct variations of surface circulation, coastal upwelling, and paleoproductivity in the northern Benguela Current System for the last 150,000 yr. The SST record most distant from the coast resembles a SST pattern typical of the pelagic ocean, with the lowest SST at full-glacial periods and the highest SST during the Eemian and the Holocene. In contrast to the modern conditions where annual mean SST decreases toward the coast, the shelf-edge SST record has the most prominent warm anomalies of about 2°C during isotope stages 2 and 6 compared with the open ocean. The glacial SST minimum in the record close to the shelf is observed between 50,000 and 35,000 yr B.P., while the record midway along the transect shows intermediate temperature conditions between the offshore and nearshore records. The causal process for the warm anomalies under full ice-age conditions close to the coast may be similar to that of recent "Benguela Niño events" that originate from perturbations in the tradewind system over the western tropical Atlantic. During these events the Angola-Benguela Front, located at about 16°S, weakens and intensive southward protrusions of tropical water masses extend into the nearshore upwelling area as far as 25°S. Thus, the two nearshore records primarily responded to variations in the time-integrated balance between upwelling intensity and southward protrusions of anomalously warm and nutrient-poor Angolan surface waters, as indicated by the good anticorrelation of SST and TOC content. Accordingly, surface water cooling off Namibia over the last 150,000 yr was most intense during stage 3 due to strong winds that worked in favor of upwelling and a decrease of Angolan warm water influence.

Kirst, Georg J.; Schneider, Ralph R.; Müller, Peter J.; von Storch, Isabel; Wefer, Gerold

1999-07-01

355

Millennial-scale variabilities of subsurface temperature and thermocline depth in the Sea of Okhotsk during the late Quaternary  

NASA Astrophysics Data System (ADS)

The Sea of Okhotsk is characterized by an extended seasonal sea-ice cover and is considered as a possible source area of the North Pacific Intermediate Water (NPIW). Therefore, the reconstruction of past sea surface temperature (SST) and subsurface structures in the Sea of Okhotsk is indispensable for the study of the past variations in the NPIW formation and of the detailed climate changes in the Northwest Pacific. We measured the concentration of alkenones in the Sea of Okhotsk surface sediments to understand the distribution of the marine biomarkers. We also produced the detailed oxygen isotopes of planktonic and benthic foraminifers and alkenone SSTs for a core XP98-PC1 (51°00'N, 152°00'E, 1107m water depth) with high sedimentation rate (~10 cm/kyr), which was collected from the slope off Kamchatka Peninsula in the Sea of Okhotsk. Alkenones are detected in the entire Okhotsk Sea including the northwestern continental shelf. The concentrations of alkenones are not shown a systematic distribution pattern in the Sea of Okhotsk. Calculated alkenone SSTs in the Sea of Okhotsk represent summer to autumn SST in the 0-20 m interval, based on the comparison of the modern SST profiles at the each site. The alkenone records indicated that the SSTs were almost constant throughout the Holocene at approximately 8.5°C at the site of core XP98-PC1. Alkenone SSTs are also lowered by 2°C at the early deglaciation and a similar warm SST were detected in the glacial periods in the Okhotsk Sea. Oxygen isotopes of planktonic foraminifera (Grobigerina bulloides and Neogloboquadrina pachyderma), however, showed the short-term fluctuations during the last 70 kyrs. Because the average depth habitat of N. pachyderma was estimated for ~100 m in the southern Okhotsk Sea (Bauch et al., 2002), the planktonic oxygen isotope variabilities were mainly caused by a rapid change in subsurface temperatures due to thermocline depth oscillation. During the Holocene, the subsurface temperature variability may correspond to the Polar Circulation Index (PCI) in the Greenland ice core (GISP2) (Mayewski et al., 1997) and the regional sea level changes (Razjigaeva et al., 2004). Warmer subsurface temperature in the Sea of Okhotsk may correspond to the warmer climate signals of PCI and high sea level stand. Therefore the millennial scale oscillations of subsurface temperature and thermocline depth were periodically occurred in the Sea of Okhotsk.

Ikehara, M.; Oba, T.; Kawamura, K.

2004-12-01

356

An experimental test of equilibration of temperature-like variables in jammed granular materials  

NASA Astrophysics Data System (ADS)

Although jammed granular systems are athermal, a number of thermodynamic-like descriptions have been proposed which make predictions about the distributions of volume and stress fluctuations. We perform experiments with an apparatus designed to generate a large number of jammed two-dimensional configurations, which consists of a single layer of photoelastic disks supported by a layer of air driven through a microporous membrane. New configurations are automatically generated by alternately dilating the system (permitting large-scale rearrangements) and compressing it biaxially until a desired volume or pressure is reached. Within each configuration, a bath of 10^3 particles surrounds a smaller subsystem of particles with either the same or a different inter-particle friction coefficient than the bath.The use of photoelastic particles permits us to find all particle positions, and to numerically solve for the vector forces at each inter-particle contact. By comparing temperature-like quantities between subsystems, we test whether equilibration is observed under several proposed volume and stress ensembles.

Puckett, James; Tighe, Brian; Daniels, Karen E.

2012-02-01

357

Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales  

PubMed Central

The majority of numerical models in climatology and geomagnetism rely on deterministic finite-difference techniques and attempt to include as many empirical constraints on the many processes and boundary conditions applicable to their very complex systems. Despite their sophistication, many of these models are unable to reproduce basic aspects of climatic or geomagnetic dynamics. We show that a simple stochastic model, which treats the flux of heat energy in the atmosphere by convective instabilities with random advection and diffusive mixing, does a remarkable job at matching the observed power spectrum of historical and proxy records for atmospheric temperatures from time scales of one day to one million years (Myr). With this approach distinct changes in the power-spectral form can be associated with characteristic time scales of ocean mixing and radiative damping. Similarly, a simple model of the diffusion of magnetic intensity in Earth's core coupled with amplification and destruction of the local intensity can reproduce the observed 1/f noise behavior of Earth's geomagnetic intensity from time scales of 1 (Myr) to 100 yr. In addition, the statistics of the fluctuations in the polarity reversal rate from time scales of 1 Myr to 100 Myr are consistent with the hypothesis that reversals are the result of variations in 1/f noise geomagnetic intensity above a certain threshold, suggesting that reversals may be associated with internal fluctuations rather than changes in mantle thermal or magnetic boundary conditions. PMID:11875208

Pelletier, Jon D.

2002-01-01

358

Processes of interannual mixed layer temperature variability in the thermocline ridge of the Indian Ocean  

NASA Astrophysics Data System (ADS)

Sea-surface temperature interannual anomalies (SSTAs) in the thermocline ridge of the southwestern tropical Indian Ocean (TRIO) have several well-documented climate impacts. In this paper, we explore the physical processes responsible for SSTA evolution in the TRIO region using a combination of observational estimates and model-derived surface layer heat budget analyses. Vertical oceanic processes contribute most to SSTA variance from December to June, while lateral advection dominates from July to November. Atmospheric fluxes generally damp SSTA generation in the TRIO region. As a result of the phase opposition between the seasonal cycle of vertical processes and lateral advection, there is no obvious peak in SSTA amplitude in boreal winter, as previously noted for heat content anomalies. Positive Indian Ocean Dipole (IOD) events and the remote influence of El Niño induce comparable warming over the TRIO region, though IOD signals peak earlier (November-December) than those associated with El Niño (around March-May). Mechanisms controlling the SSTA growth in the TRIO region induced by these two climate modes differ strongly. While SSTA growth for the IOD mostly results from southward advection of warmer water, increased surface shortwave flux dominates the El Niño SSTA growth. In both cases, vertical oceanic processes do not contribute strongly to the initial SSTA growth, but rather maintain the SSTA by opposing the effect of atmospheric negative feedbacks during the decaying phase.

Praveen Kumar, B.; Vialard, J.; Lengaigne, M.; Murty, V. S. N.; Foltz, G. R.; McPhaden, M. J.; Pous, S.; de Boyer Montégut, C.

2014-11-01

359

Diurnal variability of Sea Surface Temperature: Implications for the Fusion of Satellite and in situ Observationss for the Fusion of Satellite and in situ Observations  

Microsoft Academic Search

In the context of merging satellite infrared and microwave sea surface temperature (SST) data with in situ SST observations, SST must be specified exactly because the upper ocean (~10 m) has a complex and variable vertical temperature structure. This is related to ocean turbulence and the air-sea fluxes of heat, moisture and momentum. In particular, there is a significant diurnal

C. Donlon; C. Gentemann; W. Eifler; G. Wick

2003-01-01

360

Interdecadal variability of summer climate over East Asia and its association with 500 hPa height and global sea surface temperature  

Microsoft Academic Search

Interdecadal variability of summer climate (rainfall and temperature) in East Asia (China and Japan) and its association with the anomalies of geopotential heights at 500 hPa over the Northern Hemisphere (NH), global sea surface temperature (SSTA), and outgoing longwave radiation (OLR) were examined. An abrupt change was found in the middle and by the end of the 1970s in the

Zeng-Zhen Hu

1997-01-01

361

Variable pressure-temperature neutron diffraction of wstite ,,Fe1-xO...: Absence of long-range magnetic order to 20 GPa  

E-print Network

Variable pressure-temperature neutron diffraction of wüstite ,,Fe1-xO...: Absence of long in the high-pressure rhombohedral phase of the material. This investigation is crucial for understanding the nature of high-pressure phase transitions in Fe1-xO. Low temperature ambient pressure neutron diffraction

Downs, Robert T.

362

Interannual and interdecadal variability of ocean temperature along the equatorial Pacific in conjunction with ENSO  

NASA Astrophysics Data System (ADS)

In this paper, the leading modes of ocean temperature anomalies (OTA) along the equatorial Pacific Ocean are analyzed and their connection with El Niño-Southern Oscillation (ENSO) and interdecadal variation is investigated. The first two leading modes of OTA are connected with the different phases of the canonical ENSO and display asymmetric features of ENSO evolution. The third leading mode depicts a tripole pattern with opposite variation of OTA above the thermocline in the central Pacific to that along the thermocline in the eastern and western Pacific. This mode is found to be associated with so-called ENSO-Modoki. Insignificant correlations of this mode with the first two leading modes suggest that ENSO-Modoki may be a mode that is independent to the canonical ENSO and also has longer time scales compared with the canonical ENSO. The fourth mode reflects a warming (cooling) tendency above (below) the thermocline since 2000. Both the first and second modes have a large contribution to the interdecadal change in thermocline during 1979-2012. Also, the analysis also documents that both ENSO and OTA shifted into higher frequency since 2000 compared with that during 1979-1999. Interestingly, the ENSO-Modoki related OTA mode does not have any trend or significant interdecadal shift during 1979-2012. In addition, it is shown that first four EOF modes seem robust before and after 1999/2000, suggesting that the interdecadal shift of the climate system in the tropical Pacific is mainly a frequency shift and the changes in spatial pattern are relatively small, although the mean states over two periods experienced some significant changes.

Kumar, Arun; Hu, Zeng-Zhen

2014-03-01

363

The Atlantic Multidecadal Variability in surface and deep ocean temperature and salinity fields from unperturbed climate simulations  

NASA Astrophysics Data System (ADS)

Large multidecadal fluctuations in basin-average sea-surface temperature (SST) are a known feature of observed, reconstructed and simulated variability in the North Atlantic Ocean. This phenomenon is often referred to as Multidecadal Atlantic Variability or AMV. Historical AMV fluctuations are associated with analog basin-scale changes in sea-surface salinity, so that warming corresponds to salinification and cooling to freshening [Polyakov et al., 2005]. The surface imprint of the AMV further corresponds to same-sign fluctuations in the shallow ocean and with opposite-sign fluctuations in the deep ocean for both temperature and salinity [Polyakov et al., 2005]. This out-of-phase behavior reflects the thermohaline overturning circulation shaping North Atlantic's low-frequency variability. Several processes contribute to the AMV, involving both ocean-atmosphere coupled processes and deep ocean circulation [e.g., Grossmann and Klotzbach, 2009]. In particular, recirculation in the North Atlantic subpolar gyre region of salinity anomalies from Arctic freshwater export may trigger multidecadal variability in the Atlantic meridional overturning circulation, and therefore may be part of the AMV [Jungclaus et al., 2005; Dima and Lohmann, 2007]. With this contribution, we aim to improve the physical interpretation of the AMV by investigating spatial and temporal patterns of temperature and salinity fields in the shallow and deep ocean. We focus on two unperturbed millennial-scale simulations performed with the Max Planck Institute Earth system model in its paleo (MPI-ESM-P) and low-resolution (MPI-ESM-LR) configurations, which provide reference control climates for assessments of pre-industrial and historical climate simulations. The two model configurations only differ for the presence, in MPI-ESM-LR, of an active module for dynamical vegetation. We use spatial-average indices and empirical orthogonal functions/principal components to track the horizontal and vertical propagation of temperature and salinity anomalies related to the AMV. In particular, we discuss the potential predictability of multidecadal fluctuations in North Atlantic SSTs based on indices derived from the sea-surface salinity field. We show how the two simulations provide AMV realizations with some distinguishable characteristics, e.g., the typical fluctuations' frequencies and the linkage with the North Atlantic meridional overturning and gyre circulations. We further show how information gained by investigating different definitions of the AMV [Zanchettin et al., 2013] helps designing numerical sensitivity studies for understanding the mechanism(s) behind this phenomenon, concerning both its origin and global impacts. References Dima, M., and G. Lohmann [2007], J. Clim., 20, 2706-2719, doi:10.1175/JCLI4174.1 Jungclaus, J.H., et al. [2005], J. Clim., 18, 4013- 4031, doi:10.1175/JCLI3462.1 Polyakov, I. V., et al. [2005], J. Clim., 18:4562-4581 Grossmann, I., and P. J. Klotzbach [2009], J. Geophys. Res., 114, D24107, doi:10.1029/2009JD012728 Zanchettin D., et al. [2013], Clim. Dyn., doi:10.1007/s00382-013-1669-0

Zanchettin, D.; Jungclaus, J. H.

2013-12-01

364

Coupled Modes of Variability between Pacific and Atlantic Sea Surface Temperatures and Monthly Precipitation in Southwest Florida  

NASA Astrophysics Data System (ADS)

Water supply managers in Florida are increasingly turning to alternative sources in order to minimize the environmental impact of groundwater withdrawals. Tampa Bay Water, the largest wholesale water supplier in Southwest Florida, makes decisions regarding how to meet its customers" demands by rotating and apportioning among existing sources (groundwater, surface water, the regional reservoir, and desalination) to minimize cost and environmental impacts while maximizing reliability. As part of a study to improve source allocation decision making by Tampa Bay Water an evaluation of Pacific and Atlantic Ocean sea surface temperatures (SSTs) and monthly precipitation was performed to identify coupled modes of SST and precipitation variability. The monthly patterns of precipitation were analyzed in relation to SST in the Atlantic and Pacific Oceans using singular value decomposition analysis (SVD). Time-lagged analysis of SSTs and precipitation were investigated in order to identify SST regions that show forecast potential for use in a suite of hydrologic forecast models used by Tampa Bay Water.

Martinez, C. J.; Newman, M. A.; Jones, J. W.; Graham, W. D.

2007-12-01

365

The most problematic variable in the course of human-biometeorological comfort assessment — the mean radiant temperature  

NASA Astrophysics Data System (ADS)

This paper gives a review on the topic of the mean radiant temperature T mrt , the most important parameter influencing outdoor thermal comfort during sunny conditions. T mrt summarizes all short wave and long wave radiation fluxes reaching the human body, which can be very complex (variable in spatial and also in temporal manner) in urban settings. Thermal comfort researchers and urban planners need easy and sound methodological approaches to assess T mrt . After the basics of the T mrt calculation some of the methods suitable for obtaining T mrt also in urban environments will be presented.. Two of the discussed methods are based on instruments which measure the radiation fluxes integral (globe thermometer, pyranometer-pyrgeometer combination), and three of the methods are based on modelling the radiation environment with PC software (RayMan, ENVI-met and SOLWEIG).

Kántor, Noémi; Unger, János

2011-03-01

366

Comet Halley - Spatial and temporal variability of the silicate emission feature  

NASA Astrophysics Data System (ADS)

Narrow- and broadband photometry of Comet Halley covering the wavelength range 2-20 microns was obtained at the NASA Infrared Telescope Facility (IRTF) both preperihelion (UT 1986 January 17 and 18) and postperihelion (UT 1986 March 3-5). Strong features at 10 and 20 microns, indicative of silicate emission, were evident in the data. In addition to day-to-day variations in brightness at all wavelengths, changes were observed in the strength of the silicate emission feature on timescales as short as 3 hr. While the strength of the 10-micron feature varied with location in the coma, no such variability was observed in the shape of this emission feature, in agreement with higher spectral resolution observations (Campins and Ryan, 1989). Calculated color temperatures indicate that brightness and temperature do not correlate directly, i.e., brighter did not necessarily imply hotter dust grains. These observations are used to refine a relation between the color temperature of the dust and the heliocentric distance derived by Tokunaga et al. (1988).

Ryan, E. V.; Campins, H.

1991-02-01

367

Madagascar corals track sea surface temperature variability in the Agulhas Current core region over the past 334 years  

PubMed Central

The Agulhas Current (AC) is the strongest western boundary current in the Southern Hemisphere and is key for weather and climate patterns, both regionally and globally. Its heat transfer into both the midlatitude South Indian Ocean and South Atlantic is of global significance. A new composite coral record (Ifaty and Tulear massive Porites corals), is linked to historical AC sea surface temperature (SST) instrumental data, showing robust correlations. The composite coral SST data start in 1660 and comprise 200 years more than the AC instrumental record. Numerical modelling exhibits that this new coral derived SST record is representative for the wider core region of the AC. AC SSTs variabilities show distinct cooling through the Little Ice Age and warming during the late 18th, 19th and 20th century, with significant decadal variability superimposed. Furthermore, the AC SSTs are teleconnected with the broad southern Indian and Atlantic Oceans, showing that the AC system is pivotal for inter-ocean heat exchange south of Africa. PMID:24637665

Zinke, J.; Loveday, B. R.; Reason, C. J. C.; Dullo, W.-C.; Kroon, D.

2014-01-01

368

Low-frequency variability and zonal contrast in Sahel rainfall and Atlantic sea surface temperature teleconnections during the last century  

NASA Astrophysics Data System (ADS)

This study systematically examines teleconnections between Atlantic sea surface temperature (SST) and the west-east distribution of Sahel rainfall throughout the twentieth century, taking nonstationarity into account. Sahel rainfall variability of six selected rain gauges displays three dominant time scales: multi-decadal (>20 years), quasi-decadal (8-18 years) and interannual (2-8 years). Regarding their patterns of low-frequency scales, three coherent Sahelian subregions can be identified: the Atlantic Coast (Dakar), western-central Sahel (Nioro and Mopti) and eastern Sahel (Niamey, Maradi, Maine-Soroa). Cross-analyses combining spectral and multivariate analyses of 20 station-based data and West-African gridded rainfall data statistically confirm dissimilarities between the western and eastern Sahel. Western and eastern Sahel rainfall data are correlated with SSTs from different regions of the Atlantic Ocean, especially in the North and tropical South Atlantic. As determined by wavelet coherence and phase, in-phase relationship with North Atlantic SSTs only occurs in wet periods and at the multi- and quasi-decadal scales. This teleconnection depends on the time period and the time scale, displaying a NW-SE pattern, which suggests nonuniform modulations of meridional displacements of the Intertropical Convergence Zone (ITCZ). Tropical South Atlantic SST variability is often related to opposite patterns between the Gulf of Guinean Coast (in phase) and Sahel region (out of phase).

Dieppois, B.; Durand, A.; Fournier, M.; Diedhiou, A.; Fontaine, B.; Massei, N.; Nouaceur, Z.; Sebag, D.

2014-07-01

369

Growing season temperature and precipitation variability and extremes in the U.S. Corn Belt from 1981 to 2012  

NASA Astrophysics Data System (ADS)

Climate warming and changes in rainfall patterns and increases in extreme events are resulting in higher risks of crop failures. A greater sense of urgency has been induced to understand the impacts of past climate on crop production in the U.S. As one of the most predominant sources of feed grains, corn is also the main source of U.S. ethanol. In the U.S. Corn Belt, region-scale evaluation on temperature and precipitation variability and extremes during the growing season is not well-documented yet. This study is part of the USDA-funded project 'Useful to Usable: Transforming climate variability and change information for cereal crop producers'. The overall goal of our work is to study the characteristics of average growing season conditions and changes in growing season temperature- and precipitation-based indices that are closely correlated with corn grain yield in the U.S. Corn Belt. The research area is the twelve major Corn Belt states, including IL, IN, IA, KS, MI, MN, MO, NE, OH, SD, ND, and WI. Climate data during 1981-2010 from 132 meteorological stations (elevation ranges from 122 m to 1,202 m) are used in this study, including daily minimum, maximum, and mean temperature, and daily precipitation. From 1981 to 2012, beginning date (BD), ending date (ED), and growing season length (GSL) in the climatological corn growing season are studied. Especially, during the agronomic corn growing season, from Apr to Oct, temperature- and precipitation-based indices are analyzed. The temperature-based indices include: number of days with daily mean temperature below 10°C, number of days with daily mean temperature above 30°C, the sum of growing degree days (GDD) between 10°C to 30°C (GDD10,30, growth range for corn), the sum of growing degree days above 30°C (GDD30+, exposure to harmful warming for corn), the sum of growing degree days between 0°C and 44°C (GDD0,44, survival range limits for corn), the sum of growing degree days between 5°C and 35°C (GDD5,35, growth range limits for corn), and the sum of growing degree days between 20°C and 22°C (GDD20,22, optimal growth range for corn). And the precipitation-based indices include: cumulative precipitation, consecutive dry days, and number of extreme precipitation events in June. As to the decadal trend analysis in climatic factors, Sen's Nonparametric Estimator of Slope and the nonparametric Mann-Kendall test are used. In the U.S. Corn Belt, annual mean Tavg ranges from 5.7°C to 14.7°C, and annual cumulative precipitation ranges from 396 mm to 1,203 mm. According to the decadal trend of annual mean Tavg and annual cumulative precipitation, 30 stations (45%) demonstrate a warm and dry trend, and 28 stations demonstrate a warm and wet trend. In monthly scale, Jun mean Tmin presents the most significantly increasing trend, and no significant decreasing or zero trend is detected from 1981 to 2012. During the climatological corn growing season, BD ranges from 76 to 128 DOY, ED ranges from 276 to 316 DOY, and GSL ranges from 150 to 242 days. From 1981 to 2012, BD is significantly advanced at the rate of 1 to 8 DOY per decade, ED is significantly delayed at the rate of 1 to 5 per decade, and GSL is significantly prolonged at the rate of 1 to 11 days per decade.

Dai, S.; Shulski, M.

2013-12-01

370

Enhanced future variability during India's rainy season  

NASA Astrophysics Data System (ADS)

The Indian summer monsoon shapes the livelihood of a large share of the world's population. About 80% of annual precipitation over India occurs during the monsoon season from June through September. Next to its seasonal mean rainfall, the day-to-day variability is crucial for the risk of flooding, national water supply, and agricultural productivity. Here we show that the latest ensemble of climate model simulations, prepared for the AR-5 of the Intergovernmental Panel on Climate Change, consistently projects significant increases in day-to-day rainfall variability under unmitigated climate change. The relative increase by the period 2071-2100 with respect to the control period 1871-1900 ranges from 13% to 50% under the strongest scenario (Representative Concentration Pathways, RCP-8.5), in the 10 models with the most realistic monsoon climatology; and 13% to 85% when all the 20 models are considered. The spread across models reduces when variability increase per degree of global warming is considered, which is independent of the scenario in most models, and is 8% ± 4%/K on average. This consistent projection across 20 comprehensive climate models provides confidence in the results and suggests the necessity of profound adaptation measures in the case of unmitigated climate change.

Menon, Arathy; Levermann, Anders; Schewe, Jacob

2013-06-01

371

Exploring day-to-day dynamics of daily stressor appraisals, physical symptoms and the cortisol awakening response.  

PubMed

Stress is associated with the secretion of cortisol throughout the day, but less is known about the dynamic effects of stress on the cortisol awakening response (CAR). More widely, knowledge of the causal factors and functions of the CAR are also not fully understood. This study explored: (1) the effects of daily stressors on the next day CAR and; (2) the effects of the CAR on same day physical and affective outcomes. Sixty-four participants completed a daily diary, reporting on the occurrence of daily stressors and stress appraisals, physical symptoms, and affect. Cortisol was measured at 0, 15, 30, and 45min after awakening to provide measures of the CAR on 3 consecutive work days. Stress appraisal was found to negatively predict the CAR, such that where stressors were appraised as more stressful (where perceived demands exceeded resources), the CAR increased less the following morning. Furthermore, the CAR significantly predicted same-day physical symptoms such that a lower CAR was associated with more physical symptoms. This study provides evidence for a pathway through which daily stressors may influence physical wellbeing, and highlights the importance of appraisals for future stress-based cortisol research. PMID:25217853

Gartland, Nicola; O'Connor, Daryl B; Lawton, Rebecca; Bristow, Matt

2014-12-01

372

A day-to-day comparison study of Seasat scatterometer winds with winds observed from islands in the tropical Pacific  

NASA Technical Reports Server (NTRS)

The winds derived from the Seasat-A Satellite Scatterometer (SASS) measurements have been the subject of great interest since the 1978 mission, because of the promise of radically improved wind observations over the world ocean. Due to the early end of the mission, only a few of the planned ground truth validation experiments could be made, and the subsequent lack of sufficient high quality independent wind data for comparison has limited the ability to resolve critical issues regarding the scatterometer's performance and the correct interpretation of its signal. Operational weather observations were made of ocean winds independent of Seasat mission plans during the Seasat mission period; the results are reported of a comparison study using such observations. Previous verification with in situ winds has been primarily in middle latitudes (GOASEX, JASIN, and NDBO buoys); winds observed from nine tropical Pacific islands are compared with nearly contemporaneous measurements taken by SASS during overpasses of the islands.

Davison, Jerry; Harrison, D. E.

1989-01-01

373

report all activities on a day-to-day basis during the survey period, at home or elsewhere (2).  

E-print Network

, and only around 3,700 households were surveyed for African- American people. Consequently, any aggregate is to increase the sample size and at the same time to reduce the unit cost, innovative data manipulation methods

Illinois at Chicago, University of

374

Associations of diurnal temperature range change with the leading climate variability modes during the Northern Hemisphere wintertime and their implication on the detection of regional climate trends  

Microsoft Academic Search

This study examines associations of diurnal temperature range (DTR) changes in observations at the global, hemispheric, subcontinental, and grid box scales with five leading climate variability modes, including the Arctic Oscillation (AO), hemispheric Pacific–North America (PNA)–like mode, Pacific Decadal Oscillation, El Niño Southern Oscillation (ENSO), and Antarctic Oscillation (AAO) during the Northern Hemisphere winter season (Jan–Mar). Winter DTR variability in

Qigang Wu

2010-01-01

375

Evidence of multidecadal climate variability and the Atlantic Multidecadal Oscillation from a Gulf of Mexico sea-surface temperature-proxy record  

Microsoft Academic Search

A comparison of a Mg\\/Ca-based sea-surface temperature (SST)-anomaly record from the northern Gulf of Mexico, a calculated\\u000a index of variability in observed North Atlantic SST known as the Atlantic Multidecadal Oscillation (AMO), and a tree-ring\\u000a reconstruction of the AMO contain similar patterns of variation over the last 110 years. Thus, the multidecadal variability\\u000a observed in the instrumental record is present

Richard Z. Poore; Kristine L. DeLong; Julie N. Richey; Terrence M. Quinn

2009-01-01

376

Evidence of multidecadal climate variability and the Atlantic Multidecadal Oscillation from a Gulf of Mexico sea-surface temperature-proxy record  

Microsoft Academic Search

A comparison of a Mg\\/Ca-based sea-surface temperature (SST)-anomaly record from the northern Gulf of Mexico, a calculated index of variability in observed North Atlantic SST known as the Atlantic Multidecadal Oscillation (AMO), and a tree-ring reconstruction of the AMO contain similar patterns of variation over the last 110 years. Thus, the multidecadal variability observed in the instrumental record is present

Richard Z. Poore; Kristine L. Delong; Julie N. Richey; Terrence M. Quinn

2009-01-01

377

Twenty Years of High-Resolution Sea Surface Temperature Imagery around Australia: Inter-Annual and Annual Variability  

PubMed Central

The physical climate defines a significant portion of the habitats in which biological communities and species reside. It is important to quantify these environmental conditions, and how they have changed, as this will inform future efforts to study many natural systems. In this article, we present the results of a statistical summary of the variability in sea surface temperature (SST) time-series data for the waters surrounding Australia, from 1993 to 2013. We partition variation in the SST series into annual trends, inter-annual trends, and a number of components of random variation. We utilise satellite data and validate the statistical summary from these data to summaries of data from long-term monitoring stations and from the global drifter program. The spatially dense results, available as maps from the Australian Oceanographic Data Network's data portal (http://www.cmar.csiro.au/geonetwork/srv/en/metadata.show?id=51805), show clear trends that associate with oceanographic features. Noteworthy oceanographic features include: average warming was greatest off southern West Australia and off eastern Tasmania, where the warming was around 0.6°C per decade for a twenty year study period, and insubstantial warming in areas dominated by the East Australian Current, but this area did exhibit high levels of inter-annual variability (long-term trend increases and decreases but does not increase on average). The results of the analyses can be directly incorporated into (biogeographic) models that explain variation in biological data where both biological and environmental data are on a fine scale. PMID:24988444

Foster, Scott D.; Griffin, David A.; Dunstan, Piers K.

2014-01-01

378

Decadal rainfall variability modes in observed rainfall records over East Africa and their relations to historical sea surface temperature changes  

NASA Astrophysics Data System (ADS)

SummaryDetailed knowledge about the long-term interface of climate and rainfall variability is essential for managing agricultural activities in Eastern African countries. To this end, the space-time patterns of decadal rainfall variability modes over East Africa and their predictability potentials using Sea Surface Temperature (SST) are investigated. The analysis includes observed rainfall data from 1920 to 2004 and global SSTs for the period 1950-2004. Simple correlation, trend and cyclical analyses, Principal Component Analysis (PCA) with VARIMAX rotation and Canonical Correlation Analysis (CCA) are employed. The results show decadal signals in filtered observed rainfall record with 10 years period during March-May (MAM) and October-December (OND) seasons. During June-August (JJA), however, cycles with 20 years period are common. Too much/little rainfall received in one or two years determines the general trend of the decadal mean rainfall. CCA results for MAM showed significant positive correlations between the VARIMAX-PCA of SST and the canonical component time series over the central equatorial Indian Ocean. Positive loadings were spread over the coastal and Lake Victoria regions while negative loading over the rest of the region with significant canonical correlation skills. For the JJA seasons, Atlantic SSTs had negative loadings centred on the tropical western Atlantic Ocean associated with the wet/dry regimes over western/eastern sectors. The highest canonical correlation skill between OND rainfall and the Pacific SSTs showed that El Niño/La Niña phases are associated with wet/dry decades over the region.

Omondi, P.; Awange, J. L.; Ogallo, L. A.; Okoola, R. A.; Forootan, E.

2012-09-01

379

Spatial and Temporal Variability of Temperature and Salinity in the Deep and Abyssal Layers of the Subpolar North Atlantic  

NASA Astrophysics Data System (ADS)

The dense water overflows crossing the Denmark Strait and Faroe-Shetland Channel form the Denmark Strait Overflow Water (DSOW) and Northeast Atlantic Deep Water, respectively. Collectively with the convectively-formed Labrador Sea Water (LSW), these water masses form the deep limb of the Atlantic Meridional Overturning Circulation and hence are important components of the global climate system. Recent variability in the properties of the intermediate and deep water masses will be described by using hydrographic, moored, profiling float, altimeter and tracer data from several programs. We will show that the variability of intermediate-depth water is strongly influenced by the strength and duration of winter convection in the Labrador Sea on the western side, and the advection of warmer more saline intermediate waters from the lower latitudes on the eastern side. Four variations of LSW produced in different years were identified in the 2010 annual survey of the Labrador Sea. While gradually transforming in time, these waters have been preserved in different ranges of density and depth because of gradual weakening of winter convection since 2008, and are still distinguishable by their unique signatures in temperature, salinity and chemical tracers. The fate of each individual LSW class can now be followed by combining profiles from Argo floats and hydrographic data from several institutes. We will show how an international array of hydrographic and tracer sections supported by moored, profiling float and satellite measurements has resolved the downstream propagation of some interesting events formed in the subpolar or Arctic seas. In particular, we document strong fresh and cold anomalies in DSOW, first observed in the Irminger Sea in 1999, 2004 and 2009, and then with a year delay in the abyssal Labrador Sea.

Yashayaev, I.; Bacon, S.; de Jong, F.; Dye, S.; Fischer, J.; Holliday, N. P.; Kieke, D.; Quadfasel, D. R.; Rhein, M.; Sarafanov, A.; Valdimarsson, H.; van Aken, H. M.

2010-12-01

380

Late Holocene primary productivity and sea surface temperature variations in the northeastern Arabian Sea: Implications for winter monsoon variability  

NASA Astrophysics Data System (ADS)

in the oceanic environment of the Arabian Sea region is strongly influenced by the seasonal monsoon cycle of alternating wind directions. Prominent and well studied is the summer monsoon, but much less is known about late Holocene changes in winter monsoon strength with winds from the northeast that drive convective mixing and high surface ocean productivity in the northeastern Arabian Sea. To establish a high-resolution record of winter monsoon variability for the late Holocene, we analyzed alkenone-derived sea surface temperature (SST) variations and proxies of primary productivity (organic carbon and ?15N) in a well-laminated sediment core from the Pakistan continental margin. Weak winter monsoon intensities off Pakistan are indicated from 400 B.C. to 250 A.D. by reduced productivity and relatively high SST. At about 250 A.D., the intensity of the winter monsoon increased off Pakistan as indicated by a trend to lower SST. We infer that monsoon conditions were relatively unstable from ~500 to 1300 A.D., because primary production and SST were highly variable. Declining SST and elevated biological production from 1400 to 1900 A.D. suggest invigorated convective winter mixing by strengthening winter monsoon circulation, most likely a regional expression of colder climate conditions during the Little Ice Age on the Northern Hemisphere. The comparison of winter monsoon intensity with records of summer monsoon intensity suggests that an inverse relationship between summer and winter monsoon strength exists in the Asian monsoon system during the late Holocene, effected by shifts in the Intertropical Convergence Zone.

Böll, Anna; Lückge, Andreas; Munz, Philipp; Forke, Sven; Schulz, Hartmut; Ramaswamy, V.; Rixen, Tim; Gaye, Birgit; Emeis, Kay-Christian

2014-08-01

381

Detection and variability of the Congo River plume from satellite derived sea surface temperature, salinity, ocean colour and sea level  

NASA Astrophysics Data System (ADS)

The Congo River in Africa has the world's second highest annual mean daily freshwater discharge and is the second largest exporter of terrestrial organic carbon into the oceans. It annually discharges an average of 1,250 × 109 m3 of freshwater into the southeast Atlantic producing a vast fresh water plume, whose signature can be traced hundreds of kilometres from the river mouth. Large river plumes such as this play important roles in the ocean carbon cycle, often functioning as carbon sinks. An understanding of their extent and seasonality is therefore essential if they are to be realistically accounted for in global assessments of the carbon cycle. Despite its size, the variability and dynamics of the Congo plume are minimally documented. In this paper we analyse satellite derived sea surface temperature, salinity, ocean colour and sea level anomaly to describe and quantify the extent, strength and variability of the far-field plume and to explain its behaviour in relation to winds, ocean currents and fresh water discharge. Empirical Orthogonal Function analysis reveals strong seasonal and coastal upwelling signals, potential bimodal seasonality of the Angola Current and responses to fresh water discharge peaks in all data sets. The strongest plume-like signatures however were found in the salinity and ocean colour where the dominant sources of variability come from the Congo River itself, rather than from the wider atmosphere and ocean. These two data sets are then analysed using a statistically based water mass detection technique to isolate the behaviour of the plume. The Congo's close proximity to the equator means that the influence of the earth's rotation on the fresh water inflow is relatively small and the plume tends not to form a distinct coastal current. Instead, its behaviour is determined by wind and surface circulation patterns. The main axis of the plume between November and February, following peak river discharge, is oriented northwest, driven by the wind and Ekman surface currents and possibly a northern branch of the Benguela Coastal Current. From February through to May the main axis swings towards the southwest, extending 750 km from the mouth, coinciding with a westerly shift in the wind direction and an increase in its speed. From June through to August, when discharge is at a minimum and the plumes salinity is highest, the main axis of the plume extends up to 850 km westward, but retreats to 440 km throughout the autumn. Following the end of the coastal upwelling period and an increase in river discharge the plumes salinity starts to rise again and the equatorward fresh water tongue re-establishes itself.

Hopkins, Jo; Lucas, Marc; Dufau, Claire; Sutton, Marion; Lauret, Olivier

2013-04-01

382

Solar forcing and secular variability of the surface temperature during the last millennium in the IPSLCM4_v2 climate model  

NASA Astrophysics Data System (ADS)

Studying the climate of the last millennium gives the possibility to assess a pre-industrial period of several centuries more and more documented through surface temperature reconstructions. The Northern Hemisphere temperature reconstructions show common secular pattern reflecting the so-called Medieval Climate Anomaly and the Little Ice Age and understanding the causes of such events is a key issue in understanding natural climate variability. Many modelling have concluded that the climate during the preindustrial part of the last 1000 years was mainly affected by the variations of Total Solar Irradiance (TSI) and volcanic aerosols of the major eruptions. We present two millennium-long numerical simulations performed with the IPSLCM4_v2 fully coupled climate model, designed to focus on the impact of TSI variability during the last millennium: a 1000 yr control run with constant preindustrial boundary conditions and a simulation forced with three reconstructions of secular forcings, comprising a widely used reconstruction of TSI variability [Crowley, 2000], variations of CO2 concentration and orbital parameters. We discuss the Northern Hemisphere surface temperature variability of the forced simulation through a comparison with four Northern Hemisphere temperature reconstructions [Ammann and Wahl, 2007; Crowley and Lowery, 2000; Mann et al., 2008; Moberg et al., 2005]. This discussion is held by the evaluation of the contribution of solar, CO2 and orbital forcings to the temperature variability in the simulation through a statistical decomposition of the NH temperature signal. We then assess the amplitude of forced versus internal variability as a function of the spatial scale considered. The diagnostic aims at evaluating the spatial scale at which the variance of the forced simulation is significantly different from the internal variability represented by the control simulation, involving the detectability of the forcings. References Ammann, C., and E. Wahl (2007), The importance of the geophysical context in statistical evaluations of climate reconstruction procedures, CLIMATIC CHANGE, 85(1-2), 71-88, doi: 10.1007/s10584-007-9276-x Crowley, T., and T. Lowery (2000), How warm was the medieval warm period?, AMBIO, 29(1), 51-54. Crowley, T. J. (2000), Causes of climate change over the past 1000 years, Science, 289(5477), 270-277. Mann, M. E., et al. (2008), Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia, Proceedings of the National Academy of Sciences of the United States of America, 105(36), 13252-13257, doi: 10.1073/pnas.0805721105. Moberg, A., et al. (2005), Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data, Nature, 433(7026), 613-617, doi: 10.1038/nature03265

Servonnat, Jerome; Yiou, Pascal; Khodri, Myriam; Swingedouw, Didier; Denvil, Sébastien

2010-05-01

383

Landscape heterogeneity controls growth variability of alder, willow, and birch shrubs in response to observed increases in temperature and snow  

NASA Astrophysics Data System (ADS)

Over the last decade, evidence has emerged for a circumarctic trend of increasing shrub cover in tundra regions. On the Alaskan tundra, repeat photography has shown spatial differences in shrub patch dynamics: since 1950, most patches expanded while some remained stable. In this study we explore the underpinnings of this landscape heterogeneity by sampling the three dominant shrubs of the Alaskan tundra--alder, willow and birch--and creating shrub ring width chronologies to determine the influence of climate variability on shrub growth. Shrubs of expanding patches of all three species grew at higher rates than shrubs of stable patches. Alder and willow shrubs in expanding patches exhibited mainly positive growth trends, while their counterparts in stable patches exhibited mainly negative growth trends. Birch shrub growth declined in expanding and stable patches. Alder and willow shrub growth rates and responses to climate were controlled more by soil characteristics than by their genus; expanding alder and willow shrubs showed significant positive correlations with spring and summer temperatures, whereas alder and willow shrubs of stable patches were negatively influenced by winter precipitation. The widely-scattered stable shrub patches sampled here are considered ';moist tussock tundra,' which covers 13.4% of the low arctic landscape. In moist tussock tundra, and presumably also wet tussock tundra, the negative influence of deeper snow on shrubs outweighed the positive influence of deeper snow on ground temperature and nutrient stocks articulated by the snow-shrub-microbe hypothesis. Thus, while shrubs of expanding patches have generally profited from warmer summers, shrubs of stable patches have suffered from increased soil moisture resulting from increased snowmelt water. These results underscore the spatial and temporal complexity in shrub-climate dynamics, which will require considerable finesse to appropriately integrate into modeling efforts.

Tape, K. D.; Hallinger, M.; Buras, A.; Wilmking, M.

2013-12-01

384

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  

USGS Publications Warehouse

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-termdata 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; Dunham, Jason; Haggerty, Roy; Hockman-Wert, David

2012-01-01

385

Tidal and atmospheric forcing of the upper ocean in the Gulf of California. 1. Sea surface temperature variability  

NASA Astrophysics Data System (ADS)

Two years of satellite infrared imagery (1984-1986) are used to examine the sea surface temperature (SST) variability in the northern Gulf of California. Empirical orthogonal functions (EOFs) of the temporal and spatial SST variance for 20 monthly mean images show that the dominant SST patterns are generated by spatially varying tidal mixing in the presence of seasonal heating and cooling. These patterns are modified in the fall and winter when shelf temperatures south of Tiburon Island cool in response to upwelling-favorable winds. These same winds bring cold, dry air from off the continental United States, causing local cooling of the shallow northern shelf. During the rest of the year, the broad, shallow shelves are warmer than offshore. The seasonally reversing temperature patterns are consistent with recent hydrographic observations which show a cyclonic surface circulation in the summer and a weaker anticyclonic circulation during the rest of the year. Atmospheric forcing of the northern gulf appears to occur over large spatial scales. Area-averaged SSTs for the Guaymas Basin, island region, and northern basin show significant fluctuations which are highly correlated. These fluctuations in SST correspond to similar fluctuations in the air temperature which are related to synoptic weather events over the gulf. During periods of particularly low wind speeds, the air temperature over the gulf increases dramatically. By afternoon, intense heating of the sea surface results in the appearance of warm SST anomalies in the satellite data. These SSTs are approximately 2°C warmer than surrounding SSTs and most likely occur as a result of a spatially varying wind field. A regression analysis of the SST relative to the fortnightly tidal range shows that tidal mixing occurs over the sills in the island region as well as on the shallow norther shelf. Mixing over the sills, however, occurs as a result of large breaking internal waves or internal hydraulic jumps which mix water over the upper 300-500 m. This mixing pumps heat away from the surface, deep into the water column, there by maintaining the cool SSTs. Since mixing occurs over greater depths in the island region, the temperatures there are much colder than those generated by tidal mixing on the shallow shelves, resulting in the persistent pool of cool water evident in the satellite data. This cooler water is mixed horizontally by the basin-scale circulation, lowering the SSTs over much of the northern gulf. These reduced SSTs have a large impact on the surface heat flux by lowering the saturation vapor pressure of the air. As a result, the amount of heat lost to the atmosphere through the latent or evaporative heat flux is reduced. This may explain why the Gulf of California gains heat on an annual average rather than losing heat as occurs in the Mediterranean and Red seas where tidal mixing is not significant.

Paden, Cynthia A.; Abbott, Mark R.; Winant, Clinton D.

1991-10-01

386

Wettability of poultry litter biochars at variable pyrolysis temperatures and their impact on soil wettability and water retention relationships  

NASA Astrophysics Data System (ADS)

To reduce the impact of poultry farming on greenhouse gas emissions, poultry farming waste - poultry litter - can be converted to biofuel and biochar through slow-pyrolysis, with the biochar added to agricultural soil for nutrient enrichment and carbon sequestration. While biochars from source materials other than poultry litter have been shown to sequester carbon and increase soil fertility, there is considerable variability in biochar behavior - even with biochars created from the same source material. This situation is exacerbated by our limited understanding of how biochars alter physical, chemical, and biological processes in agricultural soils. The focus of this work is to develop a mechanistic understanding of how poultry litter (PL) biochars affect the hydrology, microbial communities, N2O emissions, and nitrogen cycling in agricultural soils. The initial focus is on the impact of PL biochar on soil hydrology. PL from Perdue AgriRecycle, LLC (Seaford, Delaware) was used to produce biochars at pyrolysis temperatures from 300°C to 600°C. To explore the impact of these biochars on soil wettability, the PL biochars were mixed with a 30/40 Accusand in mass fractions from 0% to 100%. The water contact angle was then measured using a goniometer on these sand/biochar mixtures using the sessile drop method and a single layer of sample particles. The PL biochars produced at temperatures between 300°C to 400°C were hydrophobic, while those pyrolized at > 400°C were hydrophilic. Water contact angles for samples with 100% biochar varied systematically with pyrolysis temperature, decreasing from 101.12° to 20.57° as the pyrolysis temperature increased from 300 to 600°C. Even for small amounts of hydrophobic biochar added to the hydrophilic sand, the contact angle of the mixture was altered: for sand/biochar mixtures containing only 2% hydrophobic PL biochar by weight, the contact angle of the mixture increased from ~ 8° (0% biochar) to 20° (2% biochar). For higher mass fractions, the impact of hydrophobic PL biochar on the sand/mixture contact angle was more dramatic: for a sand/biochar mixture with 15% PL biochar, the contact angle was 40.12°. Water drop penetration tests were also performed on these samples, and results were consistent with contact angles measured with the sessile drop method. To further explore the cause of the varying contact angle with pyrolysis temperature, the PL biochars were vigorously rinsed with deionized water or heated for 24 hours at 105°C, and the contact angle measurements repeated. Both rinsing and heating samples rendered hydrophobic PL biochar hydrophilic. Rinsate samples were analyzed for total organic carbon and with GC-MS. These data suggest that bio-oils produced during slow-pyrolysis at temperatures < 400°C condensed on biochar and caused hydrophobicity. These bio-oils could be removed through vigorous washing with deionized water or heating to 105°C. The implication of these changes in water contact angle from PL biochar addition on water retention relationships for soil and on water distribution within pores will be discussed.

Yi, S. C.; Witt, B.; Guo, M.; Chiu, P.; Imhoff, P. T.

2012-12-01

387

Development of a novel variable temperature scanning tunneling microscope and discovery of spectral weight shift between two bands across Tc in underdoped Bi2212  

Microsoft Academic Search

We investigated the quasiparticle interference as a function of temperature for underdoped Bi2212 with Tc=42K, using the newly developed variable temperature STM. Due to increased S\\/N and resolution, we could observe for the first time the dispersing octet peaks well above Tc. With novel high momentum resolution analysis we also found that each octet peak actually consists of two bands

Jhinhwan Lee; K. Fujita; C. K. Kim; A. Schmidt; H. Eisaki; S. Uchida; J. C. Davis

2009-01-01

388

Variable-Temperature Emission Studies of Solvation Dynamics: Evidence for Coupling of Solvation to Chromophore Structural Dynamics in the Evolution of Charge-Transfer  

E-print Network

Variable-Temperature Emission Studies of Solvation Dynamics: Evidence for Coupling of Solvation to Chromophore Structural Dynamics in the Evolution of Charge-Transfer Excited States Niels H. Damrauer and James of the spectral evolution qualitatively correlating with changes in the steric demands of the system. The most

McCusker, James K.

389

Tidal perturbations and variability in the mesopause region over Fort Collins, CO (41N, 105W): Continuous multi-day temperature and wind  

E-print Network

Tidal perturbations and variability in the mesopause region over Fort Collins, CO (41N, 105W): Continuous multi-day temperature and wind lidar observations C. Y. She, Tao Li, Richard L. Collins,1 Tao Yuan Department, Colorado State University, Fort Collins, Colorado, USA Han-Li Liu and Maura E. Hagan High

390

Investigation of the rate-controlling mechanism(s) for high temperature creep and the relationship between creep and melting by use of high pressure as a variable  

SciTech Connect

Using high pressure as a variable, the rate-controlling mechanism for high temperature creep and the relationship between creep and melting is investigated for silicon and nickel. An apparatus is used in which the samples are heated to melting point and subjected to 1 to 3 GigaPascal pressure. The stress behavior of the materials are then studied.

Not Available

1991-01-01

391

Multidecadal Ocean Temperature and Salinity Variability in the Tropical North Atlantic:2 Linking with the AMO, AMOC and Subtropical Cell3  

E-print Network

;1 Abstract1 The Atlantic multidecadal oscillation (AMO) is characterized by the sea surface warming2 (cooling1 Multidecadal Ocean Temperature and Salinity Variability in the Tropical North Atlantic:2 Linking. Introduction1 One of the most important climate variations in the Atlantic is the Atlantic multidecadal2

Wang, Chunzai

392

Thermal tolerance, oxygen consumption and haemato-biochemical variables of Tor putitora juveniles acclimated to five temperatures.  

PubMed

A 30-day acclimation trial was conducted using Tor putitora to elucidate its thermal tolerance, oxygen consumption, haemato-biochemical variables and selected enzymatic activities at five acclimation temperatures (AT). Juveniles of T. putitora were randomly distributed among five treatment groups (20, 23, 26, 29 and 32 ± 0.5 °C). There was a significant curvilinear increase in critical thermal maxima (CT(max)) (y = -0.0693x² + 1.7927x + 34.628, R² = 0.996) and lethal thermal maxima (LT(max)) (y = -0.1493x² + 2.3407x + 35.092, R² = 0.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q?? values were 1.16 between 20 and 23 °C, 3.09 between 23 and 26 °C, 1.31 between 26 and 29 °(C) and 1.76 between 29 and 32 °C of AT. The acclimation response ratios were ranged between 0.37 and 0.59. Catalase, superoxide dismutase and ATPase activities were increased linearly in liver, gill and kidney, while brain acetylcholine esterase activity decreased linearly with increasing AT. Blood glucose remained unchanged up to AT of 26 °C and increased significantly at AT of 29 and 32 °C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20 °C, and no significant changes found till AT of 26 °C and significantly decreased at 32 °C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20 °C and remained consistent till 26 °C, then decreased significantly. There was no significant change in A/G ratio through the AT 20-29 °C and increased significantly at 32 °C. The increase in CT(max), LT(max) and oxygen consumption rate with increasing AT may suggest that the thermal tolerance of T. putitora is dependent on its prior thermal exposure history, and it could adapt to higher AT by altering its haemato-biochemical variables. PMID:23532303

Akhtar, M S; Pal, A K; Sahu, N P; Ciji, A; Mahanta, P C

2013-12-01

393

Model performance of a biomass-fueled power station with variable furnace exit gas temperature to control fouling deposition  

NASA Astrophysics Data System (ADS)

A major problem associated with the utilization of any biomass fuel in direct-combustion energy production is fouling (ash deposition on boiler surfaces) and the related issue of slagging, resulting from transformations among the inorganic constituents of the fuel. These deposits reduce heat transfer from the fire- to water-side