Minimum Temperature Range Research Articles

Experiments in Late Archaic methods of heat-treating Ogallala Formation quartzarenite clasts along the Southern High Plains eastern escarpment of Texas

World-wide, flintknappers typically reduced clasts into smaller packages (e.g., bifaces, flake blanks, preforms) prior to heat-treatment. Research along the eastern escarpment of the Southern High Plains of Texas (USA) uncovered evidence of a Late Archaic (4500–2000 radiocarbon years B.P.) industry that heat-treated whole Ogallala Formation quartzarenite clasts rather than smaller lithic packages. A series of controlled and outdoor replicative experiments were conducted to ascertain the temperature range and time necessary to heat-treat quartzarenite clasts effectively, and the possible techniques used to heat-treat whole clasts without thermal shock. Roughness (Ra) and color change (R/L) were measured to quantify the results of heat-treatment.Results indicate that a minimum temperature range of 246–273°C (475–525°F) is necessary to heat-treat quartzarenite clasts. Successful heat-treatment requires placing the clasts directly on coals to achieve the necessary temperatures for heat-treatment. Avoidance of thermal shock requires that the temperature of the clasts be raised gradually. This procedure involves incrementally moving the clasts closer to the coals before directly placing the clasts on the coals. Heat-treatment results in a significant decrease in roughness (Ra) and moderate increase in cortical and interior redness. This study demonstrates that preparing smaller lithic packages for heat-treatment is not always necessary, and provides new insights into the process of heat-treatment.

The feasibility of vitrifying a sandstone enclosure in the British Iron Age

Iron Age structures with evidence for having been subjected to high temperatures have been identified throughout Europe. The thermal conditions that must have yielded such evidence of alteration remain enigmatic, especially for the case of high-silica, quartz-rich building materials such as sandstones. Here, we conduct an experimental investigation of thermal treatment using the Wincobank Iron Age hill fort site in Sheffield, South Yorkshire (U.K.) as a test case. We have selected samples of the unaltered protolithic sandstone from which the fort was constructed as starting material as well as material from the vitrified wall core. An experimental suite of thermally treated protolith samples has been analysed using a combined approach involving X-ray diffraction and thermal analysis (simultaneous differential scanning calorimetry with thermogravimetric analysis). Comparison between our experimental products and the variably vitrified samples found in the wall of the Wincobank hill fort helps to constrain firing temperatures and timescales. For mineralogical markers, we employ the high-temperature conversion of quartz to cristobalite and the melting of feldspar to compare the relative abundance of these phases before and after thermal treatment. We find that the Iron Age wall samples have mineralogical abundances most consistent with a minimum firing temperature range <1100–1250°C and a firing timescale of >10h. These first quantitative constraints for a fort constructed of sandstone are consistent with those found for forts constructed of granitic material. Finally, we explore the reasons for thermal disequilibrium during firing and invoke this mechanism to explain the differential vitrification found at some Iron Age stone-built enclosures.

A MODEL FOR PREDICTING DIAMETER OF 'RED SENSATION' PEARS

A MODEL FOR PREDICTING DIAMETER OF 'RED SENSATION' PEARS

Statistical analysis of long term spatial and temporal trends of temperature parameters over Sutlej river basin, India

The annual and seasonal trend analysis of different surface temperature parameters (average, maximum, minimum and diurnal temperature range) has been done for historical (1971–2005) and future periods (2011–2099) in the middle catchment of Sutlej river basin, India. The future time series of temperature data has been generated through statistical downscaling from large scale predictors of CGCM3 and HadCM3 models under A2 scenario. Modified Mann–Kendall test and Cumulative Sum (CUSUM) chart have been used for detecting trend and sequential shift in time series of temperature parameters. The results of annual trend analysis for period of 1971–2005 show increasing as well as decreasing trends in average (T Mean), maximum (T Max), minimum (T Min) temperature and increasing trends in Diurnal Temperature Range (DTR) at different stations. But the annual trend analysis of downscaled data has revealed statistically significant (95% confidence level) rising trends in T Mean, T Max, T Min and falling trend in DTR for the period 2011–2099. The decreasing trend in DTR is due to higher rate of increase in T Min compared to T Max.

Variations in Climate Change Indicators and Implications on Forest Resources Management in Taraba State, Nigeria

This study was carried out to investigate the variation in climate change indicators of specific interest of rainfall and temperature) in Taraba State from 1991 to 2011. Secondary data were obtained on these climate change indicators from the Nigerian Meteorological Agency (NIMET), Jalingo, Taraba State, Nigeria. Data obtained on amount of rainfall, maximum and minimum temperature and temperature range were subjected to Analysis of Variance (ANOVA). The results showed no significant differences in all the variables considered (p ≤ 0.05). This shows that the much talked about climate change in Taraba State is speculative and not based on empirical data. However, to forestall the possible menace of climate change in the study area, it was recommended that policies and programmes supporting afforestation and proper environmental management should be put in place. Also, there is need for a widespread enlightenment of the citizens on climate change to enable them to change some of the human behaviours contributing to climate change.

Thermal sulfate reduction by ammonium ion (NH4 +): implications for inorganic origin of H2S and N2 in sedimentary basins

In this study, thermal reduction of MgSO4 by NH4Cl was operated in the presence of water at 350 °C for 168 h. It was found that NH4Cl reacted with MgSO4 to produce H2S, N2 and MgCl2 as the main products. Based on the experimental results and the assumption that the MgSO4–NH4Cl reaction could approach a state of chemical equilibrium in natural environments over geological time scales, thermochemical program HSC 6.0 was utilized to model this geochemical process occurring in sedimentary basins. The results indicate that NH4+ thermodynamically more easily participates in the reduction of SO42− than C1–C30 normal alkanes of oil and gas at reservoir temperatures. The heat liberated from the reaction of MgSO4–NH4Cl was estimated as 200.40–270.50 J/mol MgSO4 in typical oil and gas reservoirs (100–200 °C), which is much smaller than previous studies. In comparison with the minimum temperature range (100–140 °C) for conventional thermochemical sulfate reduction (TSR) using hydrocarbons, the inferred threshold temperature for initiating reduction of SO42−by NH4+ in geological settings is only about 50–60 °C. The present study shows NH4+ may play an additional role in TSR process by serving as an inorganic reductant, which has substantial implications for the formation of H2S and N2 in sedimentary basins.

Clay mineral occurrence and burial transformations: reservoir potential of the Permo‐Triassic sediments of the Iberian Range

AbstractThe diagenetic evolution of Permian (Autunian and Saxonian) and Triassic (Buntsandstein) sandstones and mudrocks have been studied over 1000 m sequence from the Sigüenza 44‐3 drill core in the Iberian Range, Spain. We compare and contrast the diagenetic processes in these different lithologies and the timing of clay mineral formation. Moreover, we establish the relationship between clay mineral diagenesis and reservoir potential. Both the Permian and Triassic successions are characterised by conglomerates, sandstones and interbedded mudstones of fluvial origin that change upwards into distal deposits of a fluvio‐deltaic system. The clay minerals are illite, illite‐smectite mixed layers, kaolinite and dickite. The illite content in all sequences is not related to diminished feldspars; it is owing to the initial detrital mineralogical composition of the Autunian sandstones. The effect of feldspar alteration to kaolin minerals has a strong influence on the lost of porosity‐permeability in the Saxonian facies. In contrast, illite and mixed layers illite‐smectite are the main clay rims preserving porosity in the Buntsandstein sandstones. However, fibrous illite is the dominant pore‐filling in the Permian Autunian facies, closing porosity and permeability. Kaolinite and dickite show opposite trends: dickite increases yet kaolinite decreases from Triassic to Permian sandstones. Dickite replaced kaolinite during burial‐thermal evolution of the succession. The δD and δ18O isotopic signatures from silt and clay fractions indicate a mixture of meteoric and marine waters, and suggest a minimum temperature range between 60 and 150 °C for diagenetic pore fluids. The Permian δD values (−24‰ to −44‰) are relatively similar to Buntsandstein values (−24‰ to −37‰). However, the Permian δ18O values (+7.6 and +15.3, average of +13.3‰) are generally higher by ca. 6.2‰ compared to the Buntsandstein data (4.8–10.1‰, average +7.1‰). Such a variation is interpreted as the result of mesodiagenetic pore fluid changes. The extensive dickitisation of kaolinite is attributed to increased hydrogen ions resulting from maturation of organic matter. The vitrinite reflectance of organic matter and the modelled thermal history suggest a maximum burial of 3400 m, accomplished 70 Ma ago. The Permo‐Triassic reached the gas window shortly before major uplift, at 65 Ma, when further maturation and hydrocarbon expulsion ceased.

Trends in seasonal temperatures over the Indian region

An investigation has been carried out to identify the trends in maximum, minimum and mean temperatures and temperature range over the Indian land mass during the winter (January, and February), pre-monsoon (March–May), southwest monsoon (June–September) and post-monsoon (October–December) seasons by using high resolution daily gridded data set prepared by India Meteorological Department for the period of 1969–2005. It has been observed that the maximum temperatures over the west coast of India show rising trend in winter, southwest monsoon and post-monsoon seasons but the maximum temperatures do not show any significant trend over the other parts of the country. Minimum temperatures show increasing trend over the North Indian states in all seasons and they show an increasing trend over the west coast of India in winter and southwest monsoon seasons. Mean temperature shows an increasing trend over the west coast of India during winter and southwest monsoon seasons. Decreasing trend is observed in the temperature range over North India in all seasons due to increasing trend in minimum temperature.

English

To show the role of sacred grove in rejuvenating the microclimate, a study was conducted at the temple forest of Nagdev area (Latitude 30° 8’ 30” N and Longitude 78° 46’ 25” East) of Pauri Garhwal in Uttarakhand Himalaya, India. Nagdev temple forest area was compared with a nearby (control) site, having relatively more biotic disturbances. Weather parameters viz. temperatures- maximum and minimum, wind velocity, rainfall, sunshine hours, etc. have been collected from both study sites, compiled for monthly and annual values and compared. Daily climatic variables showed significant differences in some of the parameters. There are marked variations in the range of daily observations of all the microclimatic parameters of both sites. Relative humidity values both at morning and evening hours have clear differences, similarly, maximum and minimum temperatures have also shown remarkable differences, particularly lower range of minimum temperature at control site was -7.1°C, whereas it was -2.8°C in the temple forest. There were more days (12 days) with minus temperatures at control site as compared to temple forest (4 days). Snowfall was also high in the control site as compared to temple forest; bright sun shine hours and wind speed values are more at control site than temple forest site. Vegetation of both sites was studied following standard nested quadrat method for trees, shrubs and herbs. Phytosociological parameters of the study sites reveal that tree, shrub and herb species were more in number at temple forest site than the control site. All phytosociological parameters of tree, shrub and herb species common at both sites also showed differences in these parameters at both sites. Surface soil of both sites were also analysed for physicochemical attributes of their replicate samples and compared. Average values of soil samples for their different attributes have also shown clear variations in their ranges at both sites. Key words: Nagdev temple forest, Pauri Garhwal Himalaya, Uttarakhand, vegetation, soil, microclimatic data.

Uncertainty analysis of downscaling methods in assessing the influence of climate change on hydrology

Five downscaling techniques, namely the statistical downscaling model, the automated statistical downscaling method, the change factor (CF) method, the advanced CF method, the Weather generator (LarsWG5) method, are applied to the upstream basin of the Huaihe River. Changes in regional climate scenarios and hydrology variables are compared in future periods to investigate the uncertainty associated with the downscaling techniques. Paired-sample T test is applied to evaluation the significant of the difference of the means between the observed data and the downscaled data in the future. The Xinanjiang rainfall–runoff model is employed to simulate the rainfall–runoff relation. The results demonstrate that the downscaling techniques utilized herein predict an increased tendency in the future. The increases range of maximum temperature (Tmax) is between 3.7 and 4.7 °C until the time period of 2070–2099 (2080s). While, the increases range of minimum temperature (Tmin) is between 2.8 and 4.9 °C until 2080s. The research presented herein determined that there is an increase predicted for the peaks over threshold (discussed in the paper) and a decrease predicted for the peaks below the threshold (discussed in the paper) in the future, which illustrates that the temperature would rise gradually in the future. Precipitation changes are not as obvious as temperatures changes and tend to be influence by the season. Most downscaling techniques predict increases, and others indict decreases. The annual mean precipitation range changes between 3.2 and 53.3 %, and moreover, these changes vary from season to season.

Blast-furnace smelting with the production of low-silicon hot metal

Blast-furnace smelting today is organized so as to produce low-silicon hot metal, with subsequent desulfurization. In that case, economical furnace operation is facilitated by the use of low-ash coke characterized by hot strength and low adhesion to the slag melt, as well as stable chemical composition, minimum softening temperature range, and increased melting point of the iron. The production of low-silicon hot metal with <0.5% Si at OAO NLMK is considered.

Coberturas do solo sobre a amplitude térmica e a produtividade de pimentão

Com o objetivo de avaliar o efeito dos sistemas de plantio direto e convencional e estratégias de manejo de plantas daninhas na variação da temperatura do solo e na produtividade de pimentão, realizou-se, na Universidade Federal do Semiárido, em Mossoró-RN, um experimento no esquema de parcelas subdivididas, distribuídas no delineamento experimental em blocos casualizados com quatro repetições. Os sistemas de plantio direto e convencional do pimentão foram avaliados nas parcelas; nas subparcelas, avaliaram-se três estratégias de manejo de plantas daninhas (cobertura do solo com filme de polietileno preto, com capinas e sem capinas). Em cada subparcela foram instalados sensores tipo termopares, a 5 cm de profundidade, para medir a temperatura do solo. A partir dos dados obtidos, determinou-se a variação da temperatura ao longo do dia, no período de 20 a 30 dias após o plantio das mudas de pimentão, e a cada cinco dias, a média das temperaturas máxima e mínima e a amplitude térmica diária. Aos 60 e 147 dias após o transplante das mudas de pimentão, foram feitas avaliações da densidade e massa seca de plantas daninhas nos tratamentos sem capinas. Os tratamentos com filme de polietileno e capinado no sistema de plantio convencional apresentaram elevação na temperatura máxima diária do solo em 6,7 e 5,0 ºC, respectivamente, em relação ao sistema de plantio direto com capinas. A amplitude térmica no sistema de plantio convencional nos tratamentos com capinas regulares e com filme de polietileno foi de 11 ºC, ao passo que no sistema de plantio direto a amplitude foi de 6,3, 4,5 e 4,0 ºC nos tratamentos com capinas, sem capinas e com filme de polietileno, respectivamente. A interferência das plantas daninhas nos tratamentos sem capinas resultou em redução de 94,95 e 92,10% da produtividade comercial nos sistemas de plantio direto e convencional, respectivamente.

Influence of springtime North Atlantic Oscillation on crops yields in Northeast China

Forecasting grain production is of strategic importance in considerations of climate change and growing population. Here we show that the springtime North Atlantic Oscillation (NAO) is significantly correlated to the year-to-year increment of maize and rice yield in Northeast China (NEC). The physical mechanism for this relationship was investigated. Springtime NAO can induce sea surface temperature anomalies (SSTAs) in the North Atlantic, which display a tripole pattern and are similar to the empirical mode pattern in spring. The spring Atlantic SSTA pattern that could persists to summer, can trigger a high-level tropospheric Rossby wave response in the Eurasia continent, resulting in atmospheric circulation anomalies over the Siberia-Mongolia region, which is unfavorable (favorable) for cold surges that affect NEC. Weaker (stronger) cold surges can accordingly reduce (increase) cloud amount, resulting in an increase (a decrease) in daily maximum temperature and a decrease (an increase) in daily minimum temperature, thereby leading to an increase (a decrease) in diurnal temperature range. And summer-mean daily minimum temperature and diurnal temperature range are most significantly related to the NEC crop yields.

Physiological characterization of leaf senescence of Jatropha curcas L. populations

The objective of this paper was to assess and identify the causes of senescence in Jatropha curcas L. plants. Morphological, physiological and agricultural parameters in non-irrigated and daily irrigated plants by drip irrigation system were evaluated. The characteristics evaluated were soil humidity, the number of leafs, rate of branches growth, increase of branches diameter, relative water content, photosynthesis, transpiration, stomatal conductance, internal CO2 concentration/environment ratio, nitrogen content, specific leaf area, carotenoids, total chlorophyll, chlorophyll/carotenoids ratio, a/b chlorophyll ratio, total chlorophyll/nitrogen ratio, maximum and minimum air temperature, temperature range and nitrate reductase activity. We used four wild populations of 4-year old J. curcas. The evaluations were conducted every 10 days, between 7 a.m. and 11 a.m. The four populations assessed had the same behavior regarding the leaf senescence, acting uniformly regarding the reactions regulating their development. The photosynthetic activity, chlorophyll content, nitrate reductase activity, vegetative growth and nitrogen content were reduced during senescence. The little variation in day length, appropriate concentration of nitrogen in leaves and high soil water potential throughout the experiment suggest that these variables were not determining to trigger senescence. However, the reduced minimum temperature and the increased thermal range seemed to be determinant for the occurrence of leaf senescence.

Trends in precipitation and temperature in Florida, USA

Summary Annual, seasonal, and monthly trends in precipitation, mean temperature, maximum temperature, minimum temperature, and temperature range were evaluated using stations from the United States Historical Climatology Network (USHCN) for the time periods 1895–2009 and 1970–2009 for the state of Florida. The significance and magnitude of station trends were determined using the non-parametric Mann–Kendall test and Sen’s slope, respectively. The collective, field significance of trends were evaluated using a Monte Carlo permutation procedure. Field significant trends in seasonal precipitation were found in only the June–August and March–May seasons for the 1895–2009 and 1970–2009 time periods, respectively. Significant decreasing trends in monthly precipitation were found in the months of October and May for the 1895–2009 and 1970–2009 time periods, respectively. Field significant trends were found for all temperature variables for both time periods, with the largest number of stations with significant trends occurring in the summer and autumn months. Trends in mean, maximum, and minimum temperature were generally positive with a higher proportion of positive trends in the 1970–2009 period. The spatial coherence of trends in temperature range was generally less compared to other temperature variables, with a larger proportion of stations showing negative trends in the summer and positive trends at other times of the year and more negative trends found in the 1970–2009 period. Significant differences in temperature trends based on the surrounding land use were found for minimum temperature and temperature range in the 1970–2009 period indicating that data homogenization of the USHCN temperature data did not fully remove this influence. The evaluation of trends based on station exposure ratings shows significant differences in temperature variables in both the 1895–2009 and 1970–2009 time periods. Systematic changes in trends can be seen in the 1980s, the period of widespread conversion from liquid-in-glass to electronic measurement, indicating that some of the differences found may be due to uncorrected inhomogeneities. Since notable differences were found between differently rated stations pre-1940, a time which the present-day rating should have little to no influence, attribution of differences based on station rating should be done with caution.

Analysis of rainfall and temperature trends in northeast India

AbstractThe northeast region (NER) of India covers an area of 0.26 million km2. This region is one of the highest rainfall‐receiving regions on the planet. Consequently, it has huge water and hydropower potential and analysis of rainfall and temperature trends would be of interest to water and energy planners. Trends in monthly, seasonal, and annual rainfall and temperature on the subdivision and regional scale for the NER were examined in this study. Trend analysis of rainfall data series for 1871–2008 did not show any clear trend for the region as a whole, although there are seasonal trends for some seasons and for some hydro‐meteorological subdivisions. Similar analysis for temperature data showed that all the four temperature variables (maximum, minimum, and mean temperatures and temperature range) had rising trend. Notably for the post‐monsoon season, the Sen's estimator of slope ( °C/year) was 0.019, 0.011, and 0.015 for the maximum, minimum, and mean temperature, respectively. Copyright © 2012 Royal Meteorological Society

On-Line Monitoring of Charge Unit by Using Fiber Bragg Grating Temperature Sensors

The charge unit supply power when the power is cut off. It has been the necessary components in every type of substations to ensure the continuous operations of electric relays, automatic devices and circuit breakers. By using contacting electrical insulating Fiber Bragg Grating temperature sensor, the monitored equipment can be measured and controlled under the safe temperature. The temperatures of three fans and environment have been surveyed since June 6, 2010, in the charge unit of Yanjin substation’s main control room. The real-time monitoring of 24-hours indicates that the temperature changes in the range of 1°C. At the long-term of 479 days, the average daily minimum temperature range of three fans is 12.48°C, and the maximum range is 23.07°C. The maximum temperature is 39.14°C on April 30, 2011, and the minimum temperature is 23.98°C on January 10, 2011. The daily average of ambient temperature range is 12.04 °C, the maximum temperature is 38.38 °C on July 16, 2010, and the minimum temperature is 26.34 °C on January 9, 2011. The maximum difference between the temperature of fan and the ambient temperature is 7.60 °C on October 23, 2010. According to the relevant standards and monitoring results, the maximum threshold of fan temperature is defined to 85°C, and the threshold of temperature rise is 20°C.

Spatial variability of night temperatures at a fine scale over the Stellenbosch wine district, South Africa

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: To improve knowledge of spatial climatic variability in viticultural region at fine scale&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Night temperatures recorded at 40 data loggers that were located in the vineyards of the Stellenbosch Wine of Origin District were monitored during different weather conditions during the 2009 grape ripening period (January-March). The daily maximum difference in minimum temperature between the coolest and warmest sites was, on average, 3.2 °C for the three-month period while it reached a difference of 14 °C under radiative conditions (a difference of 1 °C to 2 °C per km and 3 °C per 100 m elevation approximately). Numerical simulations of night temperatures, using a mesoscale atmospheric model, were performed for two weather events over this period. Night temperature fields at 200m resolution were generated, taking large scale weather conditions into account. Data from 16 automatic weather stations were used for validation. Temperature data from the data loggers that were located in the vineyards were used to produce maps of spatial distribution of the daily minimum temperature at a 90m scale by means of multicriteria statistical modelling, which concomitantly took environmental factors into account. Locations with optimum thermal conditions for color and flavor development and maintenance were identified based on average values for the three-month period and for specific weather conditions.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: The range of minimum temperatures varied as a function of geographical factors and synoptic weather conditions, which resulted in significant differences in night-time thermal conditions over the wine district, with possible implications for grape metabolism. The great spatial variability within short distances emphasized the difficulty of validating outputs of atmospheric modelling with accuracy. The study showed the importance and relevance of increasing resolution to refine studies on climate spatial variability and to perform climate modelling based on distinguished weather types.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: In the context of climate change, it is crucial to improve knowledge of current climatic conditions at fine scale during periods of grapevine growth and berry ripening in order to have a baseline from which to work when discussing and considering future local adaptations to accommodate to a warmer environnement.&lt;/p&gt;

Variations in diurnal temperature range over India: Under global warming scenario

Annual, seasonal, and monthly trends in surface air temperature were examined over India during the period 1901–2003. Besides this, annual and seasonal trends were also scrutinized in view of global warming concerns during the 2 non‐global (1901–1909 and 1946–1975) and global (1910–1945 and 1976–2003) warming periods as defined by Intergovernmental Panel on Climate Change. A significant increasing trend of 0.743, 0.224, 0.484, and 0.52°C (100 yr)−1 has been observed in maximum (Tmax), minimum (Tmin), mean (Tmean) temperatures, and diurnal temperature range (DTR; Tmax − Tmin), respectively during the period 1901–2003. The annual temperatures (Tmean, Tmin, and Tmax) show a cooling (warming) tendency during the non‐global (global) warming periods, apart from the second non‐global warming period ofTmax. The seasonal trends in Tmin and Tmean also show similar behavior; whereas, Tmaxshows warming in all sub‐periods, excluding the first non‐global warming period of the pre‐monsoon and monsoon. Seasonal analysis depicts that, both post‐monsoon and winter seasons are getting warmer with regard toTmax and Tmin. During the analysis as well as in non‐global and global warming periods, annualDTR has increased. DTRincreases in all seasons, with the largest increase in winter and the smallest in post‐monsoon; whereas monthly analysis reveals that all the months, except March, October, and November are contributing significantly to the annual increase ofDTR. The partial correlation analysis reveals that the total cloud cover along with the secondary factors like precipitation and soil‐moisture are responsible for increase inDTR over India during the period 1948–2003.

Cold tolerance of the Australian spur-throated locust, Austracris guttulosa

The cold tolerance of overwintering adult Spur-throated locusts, Austracris guttulosa, was examined using measures of supercooling point relative to gender, environmental acclimation and feeding state as well as mortality for a range of sub-zero temperature exposure treatments. Freezing was lethal and supercooling points ranged from −6 to −12.8°C, but were statistically independent of fresh mass, body water content, acclimation, and/or gut content in fed and starved individuals. A significant interaction effect of gender and feeding status showed that the larger bodied females had decreased supercooling capacity with increased food material in the digestive tract. Post-freezing dissections revealed differences in the amount of freshly consumed and retained food material in the digestive tract between fed and starved individuals of each gender, which could explain this effect based on inoculation of ice crystallisation by food particles. Above supercooling temperatures, neither gender nor the rate of cooling had a significant effect on mortality. When cooled from 25°C at 0.1 or 0.5°Cmin−1 to a range of experimental minimum temperatures held for 3h, survival was ⩾74% to −7°C, but declined sharply to ⩽37% when cooled to −8°C or lower. Although the laboratory experiments reported here suggest that A. guttulosa is not freeze tolerant and unable to rapidly cold harden, exposure to typical cold and frosty nights that very rarely reach below −8°C as a night minimum in the field would be unlikely to cause mortality in the vast majority of overwintering aggregations.