136 research outputs found

    Variability of total and solid precipitation in the Canadian Arctic from 1950 to 1995

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    Trends in solid and total precipitation, as well as in the ratio of solid to total precipitation (hereinafter S/T ratio), in the Canadian Arctic in recent decades have been investigated. In addition, the influence of air temperature and circulation factors (atmospheric and oceanic) on the above-mentioned precipitation characteristics have been examined. Recently updated and adjusted data by the Canadian Climate Centre from 16 stations located in the Canadian Arctic and two stations from the sub-Arctic were used for the investigation. The southern boundary of the study area was taken after Atlas Arktiki (Tresjinkov, A. 1985. Glavnoye Upravlenye Geodeziy i Kartografiy: Moscow; 204 pp). The majority of the data cover the period from 1950 to 1995. A statistically significant increase in all kinds of areally averaged seasonal and annual precipitation for the Canadian Arctic over the period 1950–95 has been found. On the other hand, the S/T ratio did not change significantly, except for summer values, and its behaviour was also in accord with small variations noted in air temperature. An increase in air temperature in the Canadian Arctic most often led to a rise in all kinds of annual precipitation sums, but only when the warmest and coldest years were chosen based on individual stations. The pattern of the relationship is significantly more complicated, and can even be opposite to that presented above, when the sets of the warmest and coldest years are chosen based on the areally averaged annual temperature for the Canadian Arctic. Significantly more stable results of changes were found for the S/T ratio, which in warmer periods was usually lower. However, more detailed and reliable investigations of temperature–precipitation relationships conducted for individual stations showed that though the S/T ratio in warmer periods may well be lower, this only applies to the southern (warmer) part of the Canadian Arctic (<70 °N). During periods with high positive values of the North Atlantic Oscillation Index (NAOI), a decrease in precipitation is observed in the south-eastern part of the Canadian Arctic, i.e. in the area where strong cooling was also observed. During El Niño events most of the Canadian Arctic had both greater precipitation and a higher S/T ratio than during La Niña events. The most unequivocal results of precipitation and S/T ratio changes were found for changes in the Arctic Ocean circulation regimes. In almost the whole study area, a lower precipitation and S/T ratio were noted during the anticyclonic circulation regime in the Arctic Ocean

    Spatial differentiation of air temperature and humidity on western coast of Spitsbergen in 1979-1983

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    Spatial differentiation of temperature and relative humidity of air on western coast of Spitsbergen in 1979-1983 is presented. Applying the author's classification of types of atmospheric circulation in the studied area, its influence on distribution of these elements is shown. Air temperature in the area is related more to the degree of climate continentality than to its latitude. The lowest mean 5-year temperatures were calculated for stations with highest degrees of thermic continentality (Svea Gruber and Svalbard Lufthavn). The highest thermic differentiation occurs from November to March (1-4°C) and the lowest in May-June and August-October (0.0-1.5°C). It is opposite if relative humidity is concerned: the highest differences occur in summer (10-15%) and the lowest in winter (0-9%). Influence of atmospheric circulation on air temperature is larger during a polar night than a polar day. Again, it is opposite in the case of relative humidity. In both analyzed seasons the highest thermic differentiation occurred at the circulation type Ca. However, it was the lowest during a polar night at advection of air from northern and southern sectors, and during a polar day at advection from a northern sector and at the type Cc

    Air temperature in the Canadian Arctic in the mid-nineteenth century based on data from expeditions

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    The paper presents the first results of the project aimed at collecting and analysing early instrumental records from the Arctic, from the period 1846-1854. Air temperature is characterized for the Canadian Arctic using data from various expeditions and a comparison with the present-day climate is also made

    Changes in seasonal and annual high-frequency air temperature variability in the Arctic from 1951-1990

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    A detailed analysis of intraseasonal (within season) and interannual (between years) temperature variability for the whole Arctic for the period 1951–90 is provided. For this purpose four temperature variables were used: average (TMEAN), maximum (TMAX) and minimum (TMIN) temperatures, and the diurnal temperature range (DTR). The source data for the analysis were the daily TMAX and TMIN for ten stations representing almost all climatic regions in the Arctic. The methods of calculation of temperature variability were mostly taken from Plummer (1996; Australian Meteorological Magazine 45: 233). Thus the results presented for the Arctic can be fully compared with existing results for the other parts of the world (China, the former USSR, the USA and Australia). Regional trends in intraseasonal and interannual temperature variability were mixed and the majority of them were insignificant. Trends in intraseasonal variability were positive in the Norwegian Arctic and eastern Greenland and negative in the Canadian and Russian Arctic. Small increases in interannual variability for all temperature variables were observed annually in the Norwegian Arctic and eastern Greenland, and in the Canadian Arctic. These were largely a result of increases in winter and transitional seasons respectively. On the other hand, opposite tendencies, both on a seasonal and an annual basis, occurred in the Russian Arctic. Statistically significant negative trends in intraseasonal variability were noted mainly in the Canadian Arctic, whereas such trends in interannual variability were noted mainly in the Russian Arctic. The absence of significant changes in intraseasonal and interannual variability of TMEAN, TMAX, TMIN and DTR is additional evidence (besides the average temperature) that in the Arctic in the period 1951–90 no tangible manifestations of the greenhouse effect can be identified

    Spatial and temporal changes in extreme air temperatures in the Arctic over the period 1951-1990

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    A detailed analysis of the spatial and temporal changes in mean seasonal and annual daily maximum (Tmax) and minimum (Tmin) air temperatures and diurnal temperature range (DTR) in the Arctic over the period 1951–1990 is presented. This analysis is preceded by a description of the spatial distributions of the mean seasonal and annual 40-year extreme temperatures (i.e. Tmax and Tmin). The rate of decrease of the mean Arctic Tmin is about twice as weak as the rate for Tmax in the period 1951–1990. As a result, a decrease in DTR is observed. Not all areas of the Arctic, however, show such tendency, e.g. large parts of the Canadian Arctic do not. The increases in DTR here are more common in summer than in winter. The decrease in DTR is related partly to increases in cloud cover, especially in the warm half-year when solar radiation is present in the Arctic. On the contrary, in the cool half-year (mainly during polar night) the day-to-day changes of temperature, governed at this time by very variable atmospheric circulation, have a greater impact than the cloudiness. The increase in variability of Tmax and Tmin has not occurred in the most recent decades. No evidence of any greenhouse warming in the Arctic over the period 1951–1990 is seen. Most of the Tmax and Tmin trends are not statistically significant

    Influence of cloudiness on extreme air temperatures and diurnal temperature range in the Arctic in 1951-1990

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    Detailed analysis of the influence of cloudiness on extreme air temperatures and diurnal temperature ranges (DTR) in the Arctic in 1951-1990 is presented. This analysis is preceded by a description of a cloudiness fluctuation and trends in the Arctic during the last decades. A statistically significant increase of the mean cloudiness in the Arctic occurred in winter, spring and during a year. It could be due to incursion of a polluted air to the Arctic from the lower latitudes. An overall pattern of the influence of cloudiness on the daily maximum air temperature (TMAX) and the minimum air temperature (TMIN) is roughly similar. However, sometimes there are significant differences in the anomalies for clear, partly cloudy and cloudy days. In summer even an opposite influence of cloudiness on TMAX than on TMIN was noted for the Norwegian Arctic and the southern Canadian Arctic. Relations between cloudiness and DTR, based on daily data, entirely confirm the previous conclusions based on monthly data. Therefore, an increasing cloudiness of the last decades significantly influences a decrease of DTR in die Arctic, especially during the warm half-year when a solar radiation is present. During the cool half-year (particularly at polar night) an influence of cloudiness is clearly weaker and not univocal, and probably less important than non-periodical day-to-day changes of air temperature, governed at this time by very vigorous atmospheric circulation

    Temporal and spatial variation of surface air temperature over the period of instrumental observations in the Arctic

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    A detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperatures over the period of instrumental observations in the Arctic is presented. In addition, the role of atmospheric circulation in controlling the instrumental and decadal-scale changes of air temperature in the Arctic is investigated. Mean monthly temperature and temperature anomalies data from 37 Arctic, 7 sub-Arctic and 30 grid-boxes were used for analysis. The presented analysis shows that the observed variations in air temperature in the real Arctic (defined on the basis of climatic as opposed to other criteria, e.g. astronomical or botanical) are in many aspects not consistent with the projected climatic changes computed by climatic models for the enhanced greenhouse effect. The highest temperatures since the beginning of instrumental observation occurred clearly in the 1930s and can be attributed to changes in atmospheric circulation. The second phase of contemporary global warming (after 1975) is, at most, weakly marked in the Arctic. For example, the mean rate of warming for the period 1991–1995 was 2–3 times lower in the Arctic than the global average. Temperature levels observed in Greenland in the last 10–20 years are similar to those observed in the 19th century. Increases of temperature in the Arctic are more significant in the warm half-year than in the cold half-year. This seasonal pattern in temperature change confirms the view that positive feedback mechanisms (e.g. sea-ice–albedo– temperature) as yet play only a small role in enhancing temperature in the Arctic. Hypotheses are presented to explain the lack of warming in the Arctic after 1975. It is shown that in some parts of the Arctic atmospheric circulation changes, in particular in the cold half-year, can explain up to 10–50% of the temperature variance. For Arctic temperature, the most important factor is a change in the atmospheric circulation over the North Atlantic. The influence of atmospheric circulation change over the Pacific (both in the northern and in the tropical parts) is significantly lower

    Diurnal temperature range in the Arctic and its relation to hemispheric and Arctic circulation patterns

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    The changes of atmospheric circulation patterns in the Northern Hemisphere and in the Arctic for the period 1939–1990 were investigated. For this purpose, the seasonal and annual frequencies of occurrence of W, E and C macrotypes according to the Vangengeim–Girs typology and groups of synoptic processes in the Arctic (A, B, W, G, D and K) according to the Dydina classification have been computed. Spatial and seasonal patterns of the mean diurnal temperature range (DTR) in the Arctic are presented, based on the data from 33 Arctic stations for the period 1951–1990. The relationships between the DTR in the Arctic and the atmospheric circulation changes in the Northern Hemisphere and in the Arctic have been investigated. The seasonal mean DTR for each macrotype of circulation and group of circulation was calculated using daily data from ten Arctic stations for the period 1951–1990. These stations represent all climatic regions and subregions identified by the authors of Atlas Arktiki (1985. Gla6noye Upra6lenye Geodeziy i Kartografiy, Moskva, p. 204). In addition, the correlation coefficients between DTR in the Arctic and both the North Atlantic Oscillation Index (NAO) and the Zonal Index (ZI) have been computed. Statistically significant changes of atmospheric circulation in the Northern Hemisphere (mainly in low and moderate latitudes) since the mid-1970s, which are also reported by other researchers, have been confirmed. In the Arctic, the atmospheric circulation has also undergone changes in recent decades; however, these changes are significantly smaller. Both the annual and the seasonal mean DTR values have been found to be the highest in the centre of the southernmost parts of the Canadian and Russian Arctic and the lowest in the Norwegian Arctic. Based on the seasonal means, four types of annual course of the DTR in the Arctic have been identified. The results pertaining to the relationship between DTR and atmospheric circulation provide some evidence that, in recent decades, both the large-scale changes of the atmospheric circulation in the Northern Hemisphere and its changes in the Arctic have led to the damping of the cool half-year DTR in the Arctic

    Spatial variation of air temperature in the Arctic in 1951-1990

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    The paper presents a spatial distribution of changes of air temperature (T) in the Arctic. Estimates of their spatial relations in the study region were based on a correlation analysis. T in the Arctic is most strongly correlated spatially in winter and spring, and least in summer. The radius of extent of statistically significant correlation coefficients of changes of T at the stations Svalbard Lufthavn, Ostrov Kotelny and Resolute A is equal to 2000-2500 km in winter and 1500-2000 km in summer. An attempt was done to delimit the regions of consistent occurrence of the anomalies T with respect to the signs and magnitudes, as well as of the regions with the most coherent T. The Wroclaw dendrite method was used to solve this problem. Relations of the mean areal T of the climatic regions and of the Arctic as a whole, with the northern hemisphere of temperature and selected climatic factors are presented

    Exposure-Dependent Variations in Air Temperature and Humidity on the Moraine of the Aavatsmark Glacier (Nw Spitsbergen) in the Summer Season of 2010

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    The article presents results of research on the development of air temperature and relative humidity at a height of 5 cm above the active surface of the terminal lateral moraine of the Aavatsmark Glacier, relative to its exposure in the summer season of 2010. Variations in the two conditions were analysed for five measurement sites situated on northerly (SN), easterly (SE), southerly (SS) and westerly (SW) slopes, as well as on the flat top surface of the moraine (STop), in different weather conditions. The article also includes a temperature and humidity stratification in the near surface air layer (5-200 cm) above the moraine. The issues were investigated for mean values from the whole period of research, as well as for individual days demonstrating distinct degrees of cloudiness and wind speed
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