Variables Minimum Temperature Research Articles

Millennial minimum temperature variations in the Qilian Mountains, China: evidence from tree rings

Abstract. A 1343-year tree-ring chronology was developed from Qilian junipers in the central Qilian Mountains of the northeastern Tibetan Plateau (TP), China. The climatic implications of this chronology were investigated using simple correlation, partial correlation and response function analyses. The chronology was significantly positively correlated with temperature variables prior to and during the growing season, especially with monthly minimum temperature. Minimum temperature anomalies from January to August since AD 670 were then reconstructed based on the tree-ring chronology. The reconstruction explained 58% of the variance in the instrumental temperature records during the calibration period (1960–2012) and captured the variation patterns in minimum temperature at the annual to centennial timescales over the past millennium. The most recent 50 years were the warmest period, while 1690–1880 was the coldest period since AD 670. Comparisons with other temperature series from neighbouring regions and for the Northern Hemisphere as a whole supported the validity of our reconstruction and suggested that it provided a good regional representation of temperature change in the northeastern Tibetan Plateau. The results of wavelet analysis showed the occurrence of significant quasi-periodic patterns at a number of recurring periods (2–4, 40–50, and 90–170 years), which were consistent with those associated with El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and solar activity. The comparison between the reconstructed temperature and the index of tropical volcanic radiative forcing indicated that some cold events recorded by tree rings may be due to the impact of tropical volcanic eruptions.

Coupled stochastic weather generation using spatial and generalized linear models

We introduce a stochastic weather generator for the variables of minimum temperature, maximum temperature and precipitation occurrence. Temperature variables are modeled in vector autoregressive framework, conditional on precipitation occurrence. Precipitation occurrence arises via a probit model, and both temperature and occurrence are spatially correlated using spatial Gaussian processes. Additionally, local climate is included by spatially varying model coefficients, allowing spatially evolving relationships between variables. The method is illustrated on a network of stations in the Pampas region of Argentina where nonstationary relationships and historical spatial correlation challenge existing approaches.

1979~2011년, 북극진동지수 측면에서의 겨울철 남한지역 신적설과 최저 온도 특성

A characteristic of snowfall and minimum temperature variability in South Korea with respect to the variability of Arctic Oscillation (AO) was investigated. The climatic snowfall regions of South Korea based on daily new fresh snowfall data of 59 Korea Meteorological Administration (KMA) stations data corresponding to the sign of AO index during December to February 1979~2011 were classified. Especially, the differences between snowfalls of eastern regions and that of western regions in South Korea were seen by each mean 1000hPa geopotential height fields, which is one of physical structure, for the selected cases over the East Asia including the Korean Peninsula. Daily minimum temperature variability of 59 KMA station data and daily AO index during the same period were investigated using Cyclo-stationary empirical orthogonal function (CSEOF) analysis. The first CSEOF of wintertime daily AO index and that of minimum temperature of 59 KMA stations explain 33% and 66% of total variability, respectively. Correlation between principal component time series corresponding to the first CSEOF of AO index and that of temperature at the period of 1990s is over about -0.7 when that of AO index leads about 40 days.

The Impact of Temperature Variability on Years of Life Lost

To the Editor: The relationship between temperature and mortality is generally found to be bathtub shaped (rising at both extremes).1,2 However, there are limited data on the potential health effects of temperature variability3–5 and on temperature itself.6 We used a quasi-Poisson linear regression combined with a distributed lag nonlinear model to examine the relationship between temperature variability and years of life lost in Brisbane, Australia, from 1996 to 2004 (additional details in the eAppendix, https://links.lww.com/EDE/A764). Temperature variability refers to the standard deviation (SD) of minimum temperature within a given week. We found that years of life lost increased with a rise in the variability of weekly minimum temperature (Figure). Women (eFigure 2, https://links.lww.com/EDE/A764) and persons younger than 65 years (eFigure 3, https://links.lww.com/EDE/A764) were more sensitive to this variability. Years of life lost due to cardiovascular illnesses increased strongly with increases in variability of weekly minimum temperature, while years of life lost due to respiratory-related illnesses were not as sensitive to variations in minimum temperature (eFigure 4, https://links.lww.com/EDE/A764).FIGURE: The association between temperature variability (standard deviation of minimum temperature within 1 week) and years of life lost. (No reference value was set.)eTable 2 (https://links.lww.com/EDE/A764) shows the impact of a 1°C increase in weekly minimum temperature SD on years of life lost. Years of life lost increased by 8% (95% confidence interval = 1%–15%), with a 1°C increment of weekly minimum temperature SD. For each 1°C increase in the variability of weekly minimum temperature, annual health care costs were projected to increase by more than AUD$255 million. Increased temperature variability may stress the ability of the thermoregulation system to adapt to sudden and extreme temperature changes, especially when those changes happen frequently in a relatively short time period. Such adaptive ability may be reduced in the presence of other illness. Recently, Zanobetti et al5 found that summer temperature variability was associated with reduced long-term survival among people over 65 years with preexisting diseases. Bull7 has suggested that sudden changes in weather conditions may affect humoral or cellular immunity. Some researchers have reported sudden temperature changes associated with increases in blood cholesterol levels, blood pressure, and heart rate.8 In total, temperature variability should be considered as a factor in addition to temperature change when assessing possible health effects of climate change. ACKNOWLEDGMENTS We thank Adrian G. Barnett for his valuable comments on the manuscript revision. Zhiwei Xu Wenbiao Hu School of Public Health and Social Work Queensland University of Technology Brisbane, Australia Xiaoming Wang CSIRO Climate Adaptation Flagship and CSIRO Ecosystem Sciences Commonwealth, Scientific and Industrial Research Organisation Melbourne, Australia Cunrui Huang Centre for Environment and Population Health School of Environment Griffith University Brisbane, Australia Shilu Tong School of Public Health and Social Work Queensland University of Technology Brisbane, Australia Institute of Health and Biomedical Innovation Queensland University of Technology Brisbane, Australia [email protected]

Some specific features and consequences of the thermal response of rubber under cyclic mechanical loading

The present paper deals with the specificities of the thermal response of rubber under cyclic mechanical loading at constant ambient temperature. This question is important, since the stabilized thermal response is used in fatigue life criteria, especially for the fast evaluation of fatigue life. For this purpose, entropic coupling in a thermo-hyperelastic framework is first used to predict the variation in the heat source produced or absorbed by the material during cyclic loading. The heat diffusion equation is then used to deduce temperature variations under adiabatic and non-adiabatic conditions. The influence of several parameters on the stabilized thermal response is studied: signal shape, frequency, minimum and maximum stretch levels, multiaxiality of the mechanical state. The results show that, in the steady-state regime, the mean value between the maximum and minimum temperature variations over a mechanical cycle is different from zero. This is due to the specific variation in the heat source, which depends on both the stretch rate and the stretch level. This result has numerous consequences, in particular for fatigue. Indeed, the stabilized mean value between the maximum and minimum temperature variations during fatigue tests does not reflect only fatigue damage, since the entropic coupling also leads to a value different from zero. This is a major difference with respect to materials exhibiting only isentropic coupling, such as metallic materials.

NUMERICAL ANALYSIS OF TRAPEZOIDAL SHAPE DOUBLE LAYER MICROCHANNEL HEAT SINK

With increasing demand for higher computational speed and emerging micro-systems, thermal management poses serious challenge for efficient cooling. Among these liquid cooling using microchannels has gained significant attention and has been extended to its double layer configuration which eliminates the drawback of significant temperature variations in single layer system. The double layer configuration has been primarily analyzed for rectangular ducts. In this study the performance of trapezoidal shape double layer microchannel heat sink is investigated and compared to rectangular double layer heat sink of same flow area. Four different possible configurations are analyzed and comparative study among respective counter and parallel configuration is performed followed by comparison among each configuration. The performance is evaluated on the basis of maximum temperature attained at the heated surface as well as minimum temperature variations. Finally the best performing configuration is compared with double layer rectangular heat sink. Analysis shows that among various trapezoidal configurations, the one with larger side face to face is most suitable. Further comparative study with rectangular system shows that performance of trapezoidal double layer heat sink is superior in both aspects, i.e. minimum thermal resistance as well as minimum temperature variations.

Climate Change, Rice Crops and Violence. Evidence from Indonesia

This paper adopts an instrumental variable approach to uncover the impact of variations in minimum temperature on emergence and severity of actual violence through the effect on food availability, captured by rice crops per capita. The link between increase in minimum temperature and rice crops is suggested by natural science literature. We use Indonesia as a case study over the period 1990-2003. Results show that an increase of the minimum temperature during the core month of the ‘wet planting season’, i.e. December, determines an increase in violence fueled by the reduction in future rice production per capita.

Evaluation of the twenty-first century RCM simulations driven by multiple GCMs over the Eastern Mediterranean–Black Sea region

In this study, human-induced climate change over the Eastern Mediterranean–Black Sea region has been analyzed for the twenty-first century by performing regional climate model simulations forced with large-scale fields from three different global circulation models (GCMs). Climate projections have been produced with Special Report on Emissions Scenarios A2, A1FI and B1 scenarios, which provide greater diversity in climate information for future period. The gradual increases for temperature are widely apparent during the twenty-first century for each scenario simulation, but ECHAM5-driven simulation generally has a weaker signal for all seasons compared to CCSM3 simulations except for the Fertile Crescent. The contrast in future temperature change between the winter and summer seasons is very strong for CCSM3-A2-driven and HadCM3-A2-driven simulations over Carpathians and Balkans, 4–5 °C. In addition, winter runoff over mountainous region of Turkey, which feeds many river systems including the Euphrates and Tigris, increases in second half of the century since the snowmelt process accelerates where the elevation is higher than 1,500 m. Moreover, analysis of daily temperature outputs reveals that the gradual decrease in daily minimum temperature variability for January during the twenty-first century is apparent over Carpathians and Balkans. Analysis of daily precipitation extremes shows that positive trend is clear during the last two decades of the twenty-first century over Carpathians for both CCSM3-driven and ECHAM5-driven simulations. Multiple-GCM driven regional climate simulations contribute to the quantification of the range of climate change over a region by performing detailed comparisons between the simulations.

The Effect of Season and Temperature Variation on Hospital Admissions for Incident Stroke Events in Maputo, Mozambique

Identifying locale-specific patterns regarding the variation in stroke incidence throughout the year and with atmospheric temperature may be useful to the organization of stroke care, especially in low-resource settings. We aimed to describe the variation in the incidence of stroke hospitalizations across seasons and with short-term temperature variation, in Maputo, Mozambique. Between August 1, 2005, and July 31, 2006, we identified 651 stroke events in Maputo dwellers, according to the World Health Organization's STEPwise approach. The day of symptom onset was defined as the index date. We computed crude and adjusted (humidity, precipitation and temperature) incidence rate ratios (IRRs) and 95% confidence intervals (CIs) with Poisson regression. Stroke incidence did not vary significantly with season (dry versus wet: crude IRR = .98, 95% CI: .84-1.15), atmospheric temperature at the index date, or average atmospheric temperature in the preceding 2 weeks. The incidence rates of stroke were approximately 30% higher when in the previous 10 days there was a decline in the minimum temperature greater than or equal to 3 °C between any 2 consecutive days (variation in minimum temperature -5.1 to -3.0 versus -2.3 to -.4, adjusted IRR = 1.31, 95% CI: 1.09-1.57). No significant associations were observed according to the variation in maximum temperatures. Sudden declines in the minimum temperatures were associated with a higher incidence of stroke hospitalizations in Maputo. This provides important information for prediction of periods of higher hospital affluence because of stroke and to understand the mechanisms underlying the triggering of a stroke event.

A Modified Thermal Time Model to Predict Germination Rate of Ryegrass and Tall Fescue at Constant Temperatures

The thermal time model is widely used to describe the relationship between germination and temperature. However, the model breaks the germination curve into two parts and ignores the possibility that germination rate is constant at optimal temperatures. The purposes of this study were to investigate the relationship between temperature and germination rate within the context that optimum temperature (To) may be better defined as a range rather than a single point and to test for variation in minimum temperature (Tb) and the thermal time constant of a given subpopulation g at suboptimal temperatures [θ1(g)] among subpopulations. Seeds of two ryegrass cultivars, perennial ryegrass (Lolium perenne L.) ‘Bronsyn’ and annual ryegrass (Lolium multiflorum Lam.) ‘Archie’, and two tall fescue cultivars (Festuca arundinacea Schreb.) ‘Flecha AR542’ and ‘Advance’ were germinated at constant temperatures ranging from 6 to 43°C at 3°C intervals and monitored for subpopulation variability from the 10th to 80th germination percentiles. Linear regression was used to estimate the parameters of the modified thermal time model at suboptimal, optimal, and supraoptimal temperatures. The tall fescue and ryegrass cultivars all exhibited an To range over which the germination rate was constant, although the magnitude of the To range depended on cultivar and/or species and subpopulations. Therefore, a modified thermal time model incorporating upper limit of optimum temperature range (Tou) and lower limit of optimum temperature range (Tol) was proposed. This modified thermal time model can better predict the germination rate and temperature relationship in some circumstances.

Pacific Climate Forcing of Multidecadal Springtime Minimum Temperature Variability in the Western United States

Trends toward an earlier spring season onset in the western United States have been increasingly documented and are of interest to many different users of climate information throughout the region. Studies, however, have not adequately quantified the variability of spring season temperatures on multidecadal time scales. This study examines the spatio-temporal variability of spring season minimum temperatures in the western United States as a function of multidecadal Pacific climate variability for the period from 1925 to 1994. Spatio-temporal variations in minimum temperature patterns, as determined by a principal-components-based regionalization analysis, indicate a significant statistical relationship between March and April minimum temperatures and multidecadal Pacific climate variability, measured diagnostically using an index of the Pacific Decadal Oscillation (PDO). Anomalous temperature patterns associated with cool phases of the PDO are evident in the Pacific Northwest region during March, whereas warm phases are evident in the Southern Coast region during April, suggesting a possible association with canonical interannual El Niño-Southern Oscillation (ENSO) impacts. These results, suggesting a strong and thus far uncharacterized relationship between spring temperature minima in the West and the PDO, have implications for an improved understanding of multidecadal climate dynamics, including the detection and attribution of recent temperature trends, as well as climate-driven environmental impacts such as growing season length and intensity.

Variability of minimum temperature across Libya (1945–2009)

AbstractDaily and monthly minimum temperature data from 15 meteorological stations were analysed during the period 1945–2009. The spatial and temporal variability in the daily and monthly temperatures were examined, with daily minimum temperature for eight coastal stations during the period 1956–2009 (only monthly data is available for the coastal station at Nalute) and the monthly minimum temperature for the period 1945–2009 from six inland stations. Five distinct 10 year interval blocks (with the exception of the last 9 years for the eight coastal stations and 7 years for inland stations) are analysed to examine temperature patterns across Libya. The annual minimum temperature over the last 27 years (1983–2009) for the majority of coastal stations identified significant warming in the minimum temperature. The mean annual minimum temperature at all study stations (1945–2009) identified significant increases in the minimum temperature, with significant changes in annual minimum temperature over the last 32 years (1978–2009) for the majority of the coastal and inland stations across Libya. Significant changes in minimum seasonal temperature for 33/32 year intervals (1945–1977 and 1978–2009) are identified in the summer (56%) and autumn (67%) at coastal stations (67%) and inland stations (50%). Copyright © 2012 Royal Meteorological Society

Variation in liana abundance and biomass along an elevational gradient in the tropical Atlantic Forest (Brazil)

AbstractLianas play a key role in forest structure, species diversity, as well as functional aspects of tropical forests. Although the study of lianas in the tropics has increased dramatically in recent years, basic information on liana communities for the Brazilian Atlantic Forest is still scarce. To understand general patterns of liana abundance and biomass along an elevational gradient (0–1,100 m asl) of coastal Atlantic Forest, we carried out a standard census for lianas ≥1 cm in five 1‐ha plots distributed across different forest sites. On average, we found a twofold variation in liana abundance and biomass between lowland and other forest types. Large lianas (≥10 cm) accounted for 26–35% of total liana biomass at lower elevations, but they were not recorded in montane forests. Although the abundance of lianas displayed strong spatial structure at short distances, the present local forest structure played a minor role structuring liana communities at the scale of 0.01 ha. Compared to similar moist and wet Neotropical forests, lianas are slightly less abundant in the Atlantic Forest, but the total biomass is similar. Our study highlights two important points: (1) despite some studies have shown the importance of small‐scale canopy disturbance and support availability, the spatial scale of the relationships between lianas and forest structure can vary greatly among tropical forests; (2) our results add to the evidence that past canopy disturbance levels and minimum temperature variation exert influence on the structure of liana communities in tropical moist forests, particularly along short and steep elevational gradients.

Summer mean temperature variation from 1710–2005 inferred from tree-ring data of the Baimang Snow Mountains, northwestern Yunnan, China

The tree-ring chronologies of Abies georgei Orr were developed for 3 sites at different elevations: the southern (2750 m), middle (3050 m), and northern (3400 m) parts of the Baimang Snow Mountains in northwestern Yunnan Province, China. The climate-growth response analysis indi- cated that trees at different elevations respond differently to environmental changes. The radial growth of trees found at the middle and high elevation sites was determined by temperature vari- ables (mean, maximum, and minimum temperatures), particularly during the summer season (June to August), while moisture availability (precipitation and relative humidity) during spring (in March) was the crucial climate factor for tree growth at the low elevation site. The linear climate-growth model derived from the composite chronology of the 2 high elevation sites was verified with indepen- dent data from 1958 to 2005, and accounted for 33.4% of the mean temperature variation during sum- mer (June to August). Based on this model, summer minimum temperature variations were recon- structed for the past 296 yr. The reconstruction revealed that cool climates mainly occurred in 1732-1743, 1758-1780, 1791-1824, 1836-1847, 1853-1862, 1908-1929, 1964-1976, and 1979-1993, while warm climates prevailed in 1718-1731, 1744-1756, 1781-1790, 1825-1835, 1883-1907, 1930-1963, and 1995 to present. Spectral analysis of the reconstruction using the multi-taper method (MTM) indicated the existence of some multidecadal (about 70 yr) and bidecadal (about 20 yr) cycles, which might correspond to the related cycles of solar activity, and significant peaks at about 2 to 8 yr, in agreement with the spectral mode of El Nino Southern Oscillation (ENSO)-type variability.

Homogeneous Climate Divisions for Peninsular Malaysia

Classification of Peninsular Malaysia was delineated by integrating in-situ temperature elements data and Geographical Information System (GIS) raster data. The principal component (PC) analysis was applied to long-term mean monthly temperature elements data for monsoon seasons. The first three principal components were chosen to be statistically significant, accounted for 96.5% of the variability in the 27 variables. These three components are related to the mean monthly variation in minimum temperature during monsoon season (first PC), the mean monthly variation in maximum and the mean temperature in southwest monsoon (second PC), and the mean monthly variation in maximum temperature during northeast monsoon (third PC). Cluster analyses were applied to create clusters of meteorological stations, of which six classes were formed. To determine cluster boundaries, interpolation analysis was applied to generate GIS raster data of factor scores. The supervised classification analysis was then performed to the generated GIS factor data. The result of a maximum likelihood classification produced three clusters when summarized by districts. Final classification results of climate divisions show rational climate regionalization that reveals control on temperature. The use of factor score GIS raster data effectively assists the generation of meteorological station clusters, grouped using only in-situ data. © 2011 Lavoisier SAS. All rights reserved

Contribution of land‐atmosphere coupling to summer climate variability over the contiguous United States

The Weather Research and Forecasting (WRF) model has been used to study the role of land‐atmosphere coupling in influencing interannual summer climate variability over the contiguous United States. Two long‐term climate simulations are performed: a control experiment (CTL) allows soil moisture to interact freely with the atmosphere, and an additional experiment uncouples the land surface from the atmosphere by replacing summer soil moisture at each time step with the climatology of CTL. The CTL simulation reproduces well the observed summer temperature and precipitation variability, despite some discrepancies in daily mean and maximum temperature variability in the midwest/Ohio Valley region and the adjacent areas, and precipitation variability in the Great Plains and some other areas. Strong coupling of soil moisture with daily mean temperature appears mainly over the zone from the southwest to the northern Great Plains to the southeast, contributing up to about 30–60% of the total interannual variance of temperature. There is a significantly different influence on daily maximum and minimum temperatures. Soil moisture plays a leading role in explaining the variability of maximum temperature over this zone whereas minimum temperature variability is highly constrained by external factors including atmospheric circulation and sea surface temperature almost everywhere over land. Soil moisture, mainly through its effects on convection, makes a dominant contribution to precipitation variability over about half of the northern United States. This result does not support the Global Land‐Atmosphere Coupling Experiment (GLACE) hot spot hypothesis over the central United States, at least on the interannual timescale. The model's behavior agrees to a large extent with land‐atmosphere relationships diagnosed using the observations.

Impacts of maximum or minimum temperature on yield and yield components of single-season Indica rice in Yangtze-Huaihe area

Under the background of climate warming, characteristics of maximum and minimum temperature variation may markedly affect yield and yield components of rice. Maximum or minimum temperatures in the stage of yield formation during recent 50 years in the Yangtze-Huaihe area were analyzed. The result showed that the temperature-rising rate of minimum temperature has been higher than that of maximum temperature, with a decreasing diurnal temperature range (DTR), and an increasing intensity and frequency of extremely hot weather since 1991. The dynamic analysis of daily maximum or minimum temperature in different step-lengths with rice yield and yield components were made, using experimental data of Anhui Academy of Agricultural Sciences during 2000～2004. The result indicates that there are two negative effect stages of temperature on rice and rice yield before tasseling and after tasseling. And the temperature effect is most obvious on seed-setting rate, secondly on 1000-grain weight and thirdly on yield. The effect of minimum temperature on rice is greater than that of maximum temperature. With the increase of moving step-length in temperature, the increase of negative effect on maximum temperature occurs before tasseling, while the negative impacts of minimum temperature appear throughout yield formation process.

Effective heat conduction in a configuration with nonoverlapped magnetic islands

The effective radial heat conduction κeff in a plasma configuration with nonoverlapped magnetic island chains is assessed by applying an “optimal path” method. This approach implies that heat is transported predominantly along paths rendering the minimum temperature variation and is related to the principle of minimum entropy production. Paths combined of up to three radial sections and two segments aligned along magnetic field lines are considered. It is demonstrated that the enhancement of κeff over the level of perpendicular heat conduction κ⊥ arising due to flows along magnetic field lines is controlled only by the Chirikov parameter and by the value 4br2κ∥∕κ⊥, where br is the relative amplitude of the radial field resonant harmonic and κ∥ is the parallel heat conduction.

Asymmetric variability between maximum and minimum temperatures in Northeastern Tibetan Plateau: Evidence from tree rings

Ecological systems in the headwaters of the Yellow River, characterized by hash natural environmental conditions, are very vulnerable to climatic change. In the most recent decades, this area greatly attracted the public’s attention for its more and more deteriorating environmental conditions. Based on tree-ring samples from the Xiqing Mountain and A’nyemagen Mountains at the headwaters of the Yellow River in the Northeastern Tibetan Plateau, we reconstructed the minimum temperatures in the winter half year over the last 425 years and the maximum temperatures in the summer half year over the past 700 years in this region. The variation of minimum temperature in the winter half year during the time span of 1578–1940 was a relatively stable trend, which was followed by an abrupt warming trend since 1941. However, there is no significant warming trend for the maximum temperature in the summer half year over the 20th century. The asymmetric variation patterns between the minimum and maximum temperatures were observed in this study over the past 425 years. During the past 425 years, there are similar variation patterns between the minimum and maximum temperatures; however, the minimum temperatures vary about 25 years earlier compared to the maximum temperatures. If such a trend of variation patterns between the minimum and maximum temperatures over the past 425 years continues in the future 30 years, the maximum temperature in this region will increase significantly.

Minimum temperature variation at Dapoli in Konkan region of Maharahstra

Minimum temperature variation at Dapoli in Konkan region of Maharahstra