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Mean Air Temperature (mean + air_temperature)
Selected AbstractsEcophysiology of Antarctic vascular plantsPHYSIOLOGIA PLANTARUM, Issue 4 2002Miren Alberdi Most of the ice and snow-free land in the Antarctic summer is found along the Antarctic Peninsula and adjacent islands and coastal areas of the continent. This is the area where most of the Antarctic vegetation is found. Mean air temperature tends to be above zero during the summer in parts of the Maritime Antarctic. The most commonly found photosynthetic organisms in the Maritime Antarctic and continental edge are lichens (around 380 species) and bryophytes (130 species). Only two vascular plants, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl., have been able to colonize some of the coastal areas. This low species diversity, compared with the Arctic, may be due to permanent low temperature and isolation from continental sources of propagules. The existence of these plants in such a permanent harsh environment makes them of particular interest for the study of adaptations to cold environments and mechanisms of cold resistance in plants. Among these adaptations are high freezing resistance, high resistance to light stress and high photosynthetic capacity at low temperature. In this paper, the ecophysiology of the two vascular plants is reviewed, including habitat characteristics, photosynthetic properties, cold resistance, and biochemical adaptations to cold. [source] Accumulation of DNA damage in Antarctic mosses: correlations with ultraviolet-B radiation, temperature and turf water content vary among speciesGLOBAL CHANGE BIOLOGY, Issue 2 2009JOHANNA D. TURNBULL Abstract The susceptibility of three East Antarctic moss species to UV-B radiation was examined by measuring accumulation of cyclobutane pyrimidine dimers under natural sunlight during the austral summer season of 2002/03. The 2002/03 season was characterized by unusually low springtime ozone depletion and as such our results likely underestimate the DNA damage possible in a more typical UV-B radiation season. Despite this all three species accumulated significant DNA photoproducts. We also found a positive association between photoproduct accumulation and incident UV-B radiation in the two cosmopolitan species, Bryum pseudotriquetrum and Ceratodon purpureus, with more DNA damage in samples collected early in the season compared with later in the summer. For B. pseudotriquetrum, negative associations were also observed between photoproduct accumulation and both turf water content and the 10-day mean air temperature. Photoproduct accumulation in the endemic species Schistidium antarctici was similarly high across the season and no significant association with environmental variables was found. Our results are consistent with the two cosmopolitan species having somewhat higher UV-B-screening capabilities and possibly more efficient mechanisms for repairing DNA damage than the endemic S. antarctici. [source] Homogeneity analysis of Turkish meteorological data setHYDROLOGICAL PROCESSES, Issue 8 2010Sinan Sahin Abstract The missing value interpolation and homogeneity analysis were performed on the meteorological data of Turkey. The data set has the observations of six variables: the maximum air temperature, the minimum air temperature, the mean air temperature, the total precipitation, the relative humidity and the local pressure of 232 stations for the period 1974,2002. The missing values on the monthly data set were estimated using two methods: the linear regression (LR) and the expectation maximization (EM) algorithm. Because of higher correlations between test and reference series, EM algorithm results were preferred. The homogeneity analysis was performed on the annual data using a relative test and four absolute homogeneity tests were used for the stations where non-testable series were found due to the low correlation coefficients between the test and the reference series. A comparison was accomplished by the graphics where relative and absolute tests provided different outcomes. Absolute tests failed to detect the inhomogeneities in the precipitation series at the significance level 1%. Interestingly, most of the inhomogeneities detected on the temperature variables existed in the Aegean region of Turkey. It is considered that theseinhomogeneities were mostly caused by non-natural effects such as relocation. Because of changes at topography at short distance in this region intensify non-random characteristics of the temperature series when relocation occurs even in small distances. The marine effect, which causes artifical cooling effect due to sea breezes has important impact on temperature series and the orograhpy allows this impact go through the inner parts in this region. Copyright © 2010 John Wiley & Sons, Ltd. [source] Temporal variations of physical and hydrochemical properties of springs in the Mid-Levels area, Hong Kong: results of a 1-year comprehensive monitoring programmeHYDROLOGICAL PROCESSES, Issue 8 2008Chi-Man Leung Abstract Springs and seeps occur in the spaces around Po Hing Fong Street in the Mid-Levels area, Hong Kong. Most of the springs occur through the drainage weepholes on retaining walls at the street. This paper first examines the geology and history of the springs. The paper then reports the findings from a 1-year comprehensive spring monitoring programme. The temporal variations of flow rate, physiochemical parameters and hydrochemistry of the springs are discussed. The average temperatures of the springs were close to the mean air temperature, although there was a systematic lag time of 40 to 50 days between the peak air temperature and highest water temperatures. Spring waters from two rows of weepholes in the retaining wall showed significantly different physical and hydrochemical responses to the changes in rainfall and temperature, though their vertical distance is only about 1 m. The results suggest that water from the upper row of weepholes may represent a recharge source that is shallow or close to the spring outlets, whereas that from the lower row of weepholes may represent a recharge source that is much deeper or further up the hill. Although the spring flows increased rapidly after rainstorms, analysis of the total dissolved solids showed a delayed response to rainstorm events. The concentration of individual ions in the spring water varied in a unique way in response to rainstorm events. It is clear that the presence of underground man-made drainage systems and the leakage from water mains in the study area may add complexity to the solute responses and transport mechanisms. Further studies are required to constrain the impacts of these man-made structures on the hydrogeology of the springs. Copyright © 2007 John Wiley & Sons, Ltd. [source] Snow disappearance in Eastern Siberia and its relationship to atmospheric influencesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2007Yoshihiro Iijima Abstract In the present study, we examine the climatological features and interannual variations in snow disappearance within the Lena River Basin, Eastern Siberia, during a recent 15-year period (1986,2000), and the relationship of snow disappearance to atmospheric conditions. According to the climatology of the day of the year on which snow disappears, the boundary of snow disappearance within the Lena River Basin migrates rapidly northward from mid-April until early June, with minimum interannual variation occurring in the middle part of the basin. In addition, the preceding snow disappearance is apparent in the central Lena River Basin. Melting of snow within the Lena River Basin commonly occurs within 30 days of complete snow disappearance under certain atmospheric conditions: daily mean air temperature in excess of , 10 °C, greater than 2 hPa of water vapor pressure, and, hence, more than 170 W m,2 of downward longwave radiation under clear sky conditions. Composite analysis using a reanalysis dataset demonstrates that the increase in air temperature and water vapor that accompanies snow melting is due to wet (and warm) air advection in conjunction with enhanced water vapor convergence over the central Lena River Basin during the 30-day period prior to snow disappearance. Copyright © 2006 Royal Meteorological Society. [source] Effects of elevated CO2, drought and temperature on the water relations and gas exchange of groundnut (Arachis hypogaea) stands grown in controlled environment glasshousesPHYSIOLOGIA PLANTARUM, Issue 1 2000Sean C. Clifford Stands of groundnut (Arachis hypogaea L. cv. Kadiri-3) were grown in controlled environment glasshouses at mean atmospheric CO2 concentrations of 375 or 700 ,mol mol,1 and daily mean air temperatures of 28 or 32°C on irrigated or drying soil profiles. Leaf water (,l) and solute potential (,s), relative water content (RWC), stomatal conductance (gl) and net photosynthesis (Pn) were measured at midday for the youngest mature leaf throughout the growing season. Elevated CO2 and temperature had no detectable effect on the water relations of irrigated plants, but higher values of RWC, ,l and ,s were maintained for longer under elevated CO2 during progressive drought. Turgor potential (,p) reached zero when ,l declined to ,1.6 to ,1.8 MPa in all treatments; turgor was lost sooner when droughted plants were grown under ambient CO2. A 4°C increase in mean air temperature had no effect on ,s in droughted plants, but elicited a small increase in ,l; midday gl values were lower under elevated than under ambient CO2, and ,l and gl declined below ,1.5 MPa and 0.25 cm s,1, respectively, as the soil dried. Despite the low gl values recorded for droughted plants late in the season, Pn was maintained under elevated CO2, but declined to zero 3 weeks before final harvest under ambient CO2. Concurrent reductions in gl and increases in water use efficiency under elevated CO2 prolonged photosynthetic activity during drought and increased pod yields relative to plants grown under ambient CO2. The implications of future increases in atmospheric CO2 for the productivity of indeterminate C3 crops grown in rainfed subsistence agricultural systems in the semi-arid tropics are discussed. [source] Climate warming and reproduction in Chinese alligatorsANIMAL CONSERVATION, Issue 2 2009F. Zhang Abstract The Chinese alligator Alligator sinensis is a critically endangered species endemic to China, and one of the most endangered crocodilian species in the world. Like many other reptiles, important aspects of alligator biology such as foraging, timing of hibernation, breeding and the sex ratio of offspring are all affected by temperature variation. We examined the effects of long-term temperature change on oviposition dates and clutch sizes of the Chinese alligator in a semi-natural facility in southern China. Our study focused on two captive generations including an old breeding generation captured from the wild and a generation composed of their F1 offspring. Median oviposition date shifted to earlier in the year and mean clutch size was larger for both generations as the monthly mean air temperature in April increased over the 19 years of data collection. We observed a mean advance in oviposition date of 10 days for the old breeding generation from 1987 to 2005 and 8 days for both generations from 1991 to 2005. Correspondingly, clutch sizes for the two generations also increased during this period. There were no differences in median oviposition dates and clutch sizes between the two generations from 1991 to 2005. Our results suggest that Chinese alligators have responded to increasing global temperatures. Our findings also suggest that recent increasing global temperatures have the potential to have a substantial effect on Chinese alligator populations in the wild, thus prompting an urgent need for field monitoring of the effects of global warming on this endangered alligator species. [source] Effects of elevated CO2, drought and temperature on the water relations and gas exchange of groundnut (Arachis hypogaea) stands grown in controlled environment glasshousesPHYSIOLOGIA PLANTARUM, Issue 1 2000Sean C. Clifford Stands of groundnut (Arachis hypogaea L. cv. Kadiri-3) were grown in controlled environment glasshouses at mean atmospheric CO2 concentrations of 375 or 700 ,mol mol,1 and daily mean air temperatures of 28 or 32°C on irrigated or drying soil profiles. Leaf water (,l) and solute potential (,s), relative water content (RWC), stomatal conductance (gl) and net photosynthesis (Pn) were measured at midday for the youngest mature leaf throughout the growing season. Elevated CO2 and temperature had no detectable effect on the water relations of irrigated plants, but higher values of RWC, ,l and ,s were maintained for longer under elevated CO2 during progressive drought. Turgor potential (,p) reached zero when ,l declined to ,1.6 to ,1.8 MPa in all treatments; turgor was lost sooner when droughted plants were grown under ambient CO2. A 4°C increase in mean air temperature had no effect on ,s in droughted plants, but elicited a small increase in ,l; midday gl values were lower under elevated than under ambient CO2, and ,l and gl declined below ,1.5 MPa and 0.25 cm s,1, respectively, as the soil dried. Despite the low gl values recorded for droughted plants late in the season, Pn was maintained under elevated CO2, but declined to zero 3 weeks before final harvest under ambient CO2. Concurrent reductions in gl and increases in water use efficiency under elevated CO2 prolonged photosynthetic activity during drought and increased pod yields relative to plants grown under ambient CO2. The implications of future increases in atmospheric CO2 for the productivity of indeterminate C3 crops grown in rainfed subsistence agricultural systems in the semi-arid tropics are discussed. [source] | ||||||||||