Home About us Contact
|
Home About us Contact | ||
|
|
||
Average Air Temperature (average + air_temperature)
Selected AbstractsInfluence of climate on the incidence of thiazide-induced hyponatraemiaINTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 3 2007K. M. Chow Summary The role of hot temperature has been implicated in thiazide-induced hyponatraemia; however, it has never been studied in a systematic manner. The aim of this retrospective study is to correlate the incidence of thiazide-induced hyponatraemia and climate factors in a university teaching hospital from June 1996 to February 2002. We evaluated a representative sample of 201 subjects with thiazide-induced hyponatraemia. Overall, 2.9 ± 2.2 (range 0,10, median 3) cases of thiazide-induced hyponatraemia were encountered each month during the study period. There was no seasonal variation in the rate of thiazide-induced hyponatraemia (overall ,2 test, p = 7.0). Thiazide-induced hyponatraemia was not more frequently reported in summer. There was no discernible correlation between the monthly number of cases and average air temperature (r = ,0.056, p = 0.65) and relative humidity (r = 0.103, p = 0.40). On the other hand, patients who presented with thiazide-induced hyponatraemia in July and August had significantly higher serum sodium concentration, 118 ± 7 mmol/l vs. 114 ± 8 mmol/l in other calendar months (p = 0.016). Temperature showed a statistically significant positive correlation with the level of serum sodium (r = 0.20, p = 0.004). These data demonstrate that there are no seasonal variations in thiazide-induced hyponatraemia disorders, at least in countries with subtropical climate. The question arises whether hypotonic sweat loss mitigates the risk of excessive water drinking in hot summer. [source] The influence of seasonal climatic parameters on the permafrost thermal regime, West Siberia, RussiaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2009Valeria V. Popova Abstract Statistical correlations between seasonal air temperatures and snow depths and active layer depths and permafrost temperatures were analysed for tundra (Marre-Salle) and northern taiga (Nadym) sites in Western Siberia. Interannual variations in active layer depth in the tundra zone correlated with the average air temperature of the current summer, and in peatland and humid tundra, also with summer temperatures of the preceding 1,2 years. In the northern taiga zone, the active layer depth related to current summer air temperature and to a lesser extent, to spring and/or winter air temperatures. Variations in summer permafrost temperatures at 5,10,m depth were correlated with spring air temperatures in the current and preceding 1,2 years. The weather regime during the preceding 1,2 years, therefore, reinforced or weakened ground temperature variations in a given year. Overall, the most important factors influencing the permafrost regime were spring and summer air temperatures, and in one case snow depth. However, statistical links between meteorological and permafrost parameters varied between the tundra and northern taiga zones and among landscape types within each zone, emphasising the importance of analyses at short temporal scales and for individual terrain units. Copyright © 2009 John Wiley & Sons, Ltd. [source] Thermal acclimation of photosynthesis: a comparison of boreal and temperate tree species along a latitudinal transectPLANT CELL & ENVIRONMENT, Issue 6 2010DYLAN N. DILLAWAY ABSTRACT Common gardens were established along a ,900 km latitudinal transect to examine factors limiting geographical distributions of boreal and temperate tree species in eastern North America. Boreal representatives were trembling aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh.), while temperate species were eastern cottonwood (Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum (Liquidambar styraciflua L.). The species were compared with respect to adjustments of leaf photosynthetic metabolism along the transect, with emphasis on temperature sensitivities of the maximum rate of ribulose bisphosphate (RuBP) carboxylation (EV) and regeneration (EJ). During leaf development, the average air temperature (Tgrowth) differed between the coolest and warmest gardens by 12 °C. Evidence of photosynthetic thermal acclimation (metabolic shifts compensating for differences in Tgrowth) was generally lacking in all species. Namely, neither EV nor EJ was positively related to Tgrowth. Correspondingly, the optimum temperature (Topt) of ambient photosynthesis (Asat) did not vary significantly with Tgrowth. Modest variation in Topt was explained by the combination of EV plus the slope and curvature of the parabolic temperature response of mesophyll conductance (gm). All in all, species differed little in photosynthetic responses to climate. Furthermore, the adaptive importance of photosynthetic thermal acclimation was overshadowed by gm's influence on Asat's temperature response. [source] Modelling carbon balances of coastal arctic tundra under changing climateGLOBAL CHANGE BIOLOGY, Issue 1 2003Robert F. Grant Abstract Rising air temperatures are believed to be hastening heterotrophic respiration (Rh) in arctic tundra ecosystems, which could lead to substantial losses of soil carbon (C). In order to improve confidence in predicting the likelihood of such loss, the comprehensive ecosystem model ecosys was first tested with carbon dioxide (CO2) fluxes measured over a tundra soil in a growth chamber under various temperatures and soil-water contents (,). The model was then tested with CO2 and energy fluxes measured over a coastal arctic tundra near Barrow, Alaska, under a range of weather conditions during 1998,1999. A rise in growth chamber temperature from 7 to 15 °C caused large, but commensurate, rises in respiration and CO2 fixation, and so no significant effect on net CO2 exchange was modelled or measured. An increase in growth chamber , from field capacity to saturation caused substantial reductions in respiration but not in CO2 fixation, and so an increase in net CO2 exchange was modelled and measured. Long daylengths over the coastal tundra at Barrow caused an almost continuous C sink to be modelled and measured during most of July (2,4 g C m,2 d,1), but shortening daylengths and declining air temperatures caused a C source to be modelled and measured by early September (,1 g C m,2 d,1). At an annual time scale, the coastal tundra was modelled to be a small C sink (4 g C m,2 y,1) during 1998 when average air temperatures were 4 °C above normal, and a larger C sink (16 g C m,2 y,1) during 1999 when air temperatures were close to long-term normals. During 100 years under rising atmospheric CO2 concentration (Ca), air temperature and precipitation driven by the IS92a emissions scenario, modelled Rh rose commensurately with net primary productivity (NPP) under both current and elevated rates of atmospheric nitrogen (N) deposition, so that changes in soil C remained small. However, methane (CH4) emissions were predicted to rise substantially in coastal tundra with IS92a-driven climate change (from ,20 to ,40 g C m,2 y,1), causing a substantial increase in the emission of CO2 equivalents. If the rate of temperature increase hypothesized in the IS92a emissions scenario had been raised by 50%, substantial losses of soil C (,1 kg C m,2) would have been modelled after 100 years, including additional emissions of CH4. [source] Crop planting dates: an analysis of global patternsGLOBAL ECOLOGY, Issue 5 2010William J. Sacks ABSTRACT Aim, To assemble a data set of global crop planting and harvesting dates for 19 major crops, explore spatial relationships between planting date and climate for two of them, and compare our analysis with a review of the literature on factors that drive decisions on planting dates. Location, Global. Methods, We digitized and georeferenced existing data on crop planting and harvesting dates from six sources. We then examined relationships between planting dates and temperature, precipitation and potential evapotranspiration using 30-year average climatologies from the Climatic Research Unit, University of East Anglia (CRU CL 2.0). Results, We present global planting date patterns for maize, spring wheat and winter wheat (our full, publicly available data set contains planting and harvesting dates for 19 major crops). Maize planting in the northern mid-latitudes generally occurs in April and May. Daily average air temperatures are usually c. 12,17 °C at the time of maize planting in these regions, although soil moisture often determines planting date more directly than does temperature. Maize planting dates vary more widely in tropical regions. Spring wheat is usually planted at cooler temperatures than maize, between c. 8 and 14 °C in temperate regions. Winter wheat is generally planted in September and October in the northern mid-latitudes. Main conclusions, In temperate regions, spatial patterns of maize and spring wheat planting dates can be predicted reasonably well by assuming a fixed temperature at planting. However, planting dates in lower latitudes and planting dates of winter wheat are more difficult to predict from climate alone. In part this is because planting dates may be chosen to ensure a favourable climate during a critical growth stage, such as flowering, rather than to ensure an optimal climate early in the crop's growth. The lack of predictability is also due to the pervasive influence of technological and socio-economic factors on planting dates. [source] | ||||||||||