Over the South American sector of the Antarctic Ocean intensive cyclonal activity occurred in turn with meridional circulation, which was a more common feature of winter 1986 than it usually is. At the Arctowski Station strong temperature oscillations were observed during the austral winter from May to October. In the end of July the lowest temperature of this winter, — 32.3°C, was recorded. In the first half of the winter an easterly air flow prevailed and in the second part — the westerly one. Winds were strong and gusty. The highest speed reached 74 ms-1 . Snowfalls were abundant; depth of snow exceeded 100 cm.
Obervations of wind directions and air temperatures in Hornsund, Spitsbergen, in 1978—1985 were used to compute frequency distribution of wind directions and mean air temperatures at particular wind directions. Prevailing easterly winds (60°, 90° and 120°) resulted in lower air temperatures (to —2.2°C) than winter and spring means and in higher (nearly 1°C) than summer and autumn mean temperatures. Greatest positive deviations from mean seasonal temperatures are observed in winter at southerly and southwesterly winds and reach 10°C. Greatest negative deviations from mean seasonal temperatures are noted at northerly winds (330° and 360°) in autumn and reach —3.7°C.
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.
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 areał T of the climatic regions and of the Arctic as a whole, with the northern hemisphere of temperature and selected climatic factors are presented.
The frequency of wind occurrence at sectors each 30° as well as mean air temperature at particular wind direction were accounted for the warmest and the coldest year of the investigation period 1978—1987 at Polish Antarctic „Arctowski" Station. The effect of orography on wind direction and air temperature was determined. A great rate of dependence of air temperature and wind direction upon atmospheric circulation type was found. High air temperature at the winds from 300° and 330° directions is related both to the kind of air mass and foehn phenomena.
Observations from 1978—81, 1983 and 1985 collected at the Polish Polar Arctowski Station (King George Island, South Shetland Islands) were used to calculate frequencies of wind directions in 30° sectors and mean air temperatures observed at each wind direction. Results reveal that all over the year the warmest air masses flow onto the South Shetland Islands from the northwest while the coolest ones from the southeast and east.
In this study, weather conditions causing warm waves in north−western Spits − bergen, exemplified by Ny− Å lesund station, were analyzed. Between 1981 and 2010, 536 days with the maximum temperature exceeding 8.3 ° C (the value of 95 percentile) were selected. 37 warm waves, which altogether lasted 268 days, were identified. A typical feature of pressure pattern causing warm waves was the appearance of positive anomalies of both the sea level pressure and the height of isobaric surface 500 hPa in the Euro−Atlantic sector of the Arctic. This indicates a presence of high−pressure systems in this region. Extremely warm days appeared more often with the circulation from the eastern than the western sector. Longer and warmer heat waves occurring in the last decade of the analyzed period may be considered as a sign of climate warming, which has a significant impact on environment, i.e. reduction in area and thickness of glaciers, reduction of permafrost and snow cover, changes in biodiversity, etc . The increase in the air temperature and more frequent occurrence of heat waves may encourage development of tourism in polar areas, potentially causing further changes in the environment.
The climatic change on King George Island (KGI) in the South Shetland Islands, Antarctica, in the years of 1948–2011 are presented. In the reference period, a statistically significant increase in the air temperature (0.19 ° C/10 years, 1.2 ° C in the analysed period) occurred along with a decrease in atmospheric pressure (−0.36 hPa/10 years, 2.3 hPa). In winter time, the warming up is more than twice as large as in summer. This leads to decrease in the amplitude of the annual cycle of air temperature. On KGI, there is also a warming trend of daily maximum and daily minimum air temperature. The evidently faster increase in daily minimum results in a decrease of the diurnal temperature range. The largest changes of air pressure took place in the summertime (−0.58 hPa/10 years) and winter (−0.34 hPa/10 years). The Semiannual Oscillation pattern of air pressure was disturbed. Climate changes on KGI are correlated with changing surface temperatures of the ocean and the concentration of sea ice. The precipitation on KGI is characterised by substantial variability year to year. In the analysed period, no statistically significant trend in atmospheric precipitation can be observed. The climate change on KGI results in substantial and rapid changes in the environment, which poses a great threat to the local ecosystem.
A two-year-long data set of air temperature from four different altitudes above Petuniabukta, central Spitsbergen, was analysed in order to assess the near-surface temperature lapse rates and the relative frequency of air temperature inversion occurrence. From August 2013 to July 2015, air temperatures at adjacent altitudes in Petuniabukta were strongly correlated. The near-surface lapse rates in all three layers differed significantly both from the average lapse rate in the international standard atmosphere (0.65°C 100 m-1) and the lapse rate calculated by linear regression. A pronounced annual cycle was detected in the lowermost air layer (from 23 to 136 m a.s.l.) with a variable near-surface lapse rate in the winter months, while an annual cycle was not apparent in the air layers above 136 m a.s.l. The lowermost layer was also characterized by a notable daily cycle in near-surface lapse rate in spring and autumn. Air temperature inversions occurred in up to 80% of the study period in the air layer below 136 m a.s.l., with the relative frequency being much lower in the other two air layers. The air temperature inversions lasted as long as 139 hours. A case study revealed that one of the strongest air temperature inversions was connected to an area of lower pressure gradients at the 850-hPa pressure level.
The Antarctic Peninsula region has experienced a recent cooling for about 15 years since the beginning of the 21st century. In Livingston Island, this cooling has been of 0.8°C over the 12-yr period 2004–2016, and of 1.0°C for the summer average temperatures over the same period. In this paper, we analyse whether this observed cooling has implied a significant change in the density of the snowpack covering Hurd and Johnsons glaciers, and whether such a density change has had, by itself, a noticeable impact in the calculated surface mass balance. Our results indicate a decrease in the snow density by 22 kg m-3 over the study period. The density changes are shown to be correlated with the summer temperature changes. We show that this observed decrease in density does not have an appreciable effect on the calculated surface mass balance, as the corresponding changes are below the usual error range of the surface mass balance estimates. This relieves us from the need of detailed and time-consuming snow density measurements at every mass-balance campaign.
In this study, atlases of wave characteristics and wave energy for the Barents Sea have been generated for the years from 1996 to 2015 based on ERA-Interim datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF). The wave power resources in the Barents Sea can be exploited with sea ice extent declining in recent years. The entire Barents Sea has been divided into multi-year sea ice zones, seasonal sea ice zones and open water zones according to the 20-year averaged sea ice concentration. In the entire domain, the spatial distributions of the annual averaged and mean monthly significant wave heights and wave energy flux are presented. For the open water zones, 15 points have been selected at different locations so as to derive and study the wave energy roses and the inter-annual wave power variation. Moreover, the correlations between the wave energy period and the significant wave height are shown in the energy and scatter diagrams. The maximum wave power occurs in the winter in the western parts of the Barents Sea with more than 60kW/m. The wave energy can therefore be exploited in the open water zones.
Temperature and precipitation conditions in the Kaffiøyra region in the summer season (21 July-31 August) for the period from 1975-2014 are described based on data collected during 22 expeditions, in which meteorological measurements were carried out, and complete data series combining both original and reconstructed data. The latter ones were obtained using data from the Ny Ålesund meteorological station, which are strongly correlated with data from the Kaffiøyra region. Seasonal statistics presented for temperature and precipitation based on these two sets of data reveal only slight changes. Summer temperatures in the Kaffiøyra region in the studied period (1975-2014) showed statistically significant strong upward trends, while precipitation totals revealed a downward trend, but not statistically significant. In the studied area, based on 40-years of data, it was demonstrated that the near-surface lapse rates of summer air temperature are slightly lower in glaciated (0.58°C/100 m) than in non-glaciated areas (0.67°C/100 m). Anticyclonic/cyclonic circulation types significantly increase/decrease air temperature on the Waldemar Glacier, while their impact on precipitation is markedly smaller. In summer, close correlations were observed between air temperature and such glacier characteristics as the mass balance and the location of the equilibrium line, while precipitation does not have a great influence on them.
The coreless winters ( i.e. not having a cold core) were distinguished in four stations within the European sector of the Arctic. Anomalies of the frequency of the Niedźwiedź’s (2011) circulation types were calculated separately for the mid−winter warm months and for cold months preceding and following the warm−spells. Furthermore, composite and anomaly maps of the sea level pressure as s well as anomaly maps of the air temperature at 850 gpm (geopotential meters) were constructed separately for the mid−winter warm events and for the cold months before and after warming. Different pressure patterns were recognized among the days of mid−winter warm spells, using the clustering method. The occurrence of coreless winters in the study area seems to be highly controlled by the position, extension and intensity of large scale atmospheric systems, mainly the Icelandic Low. When the Low spreads to the east and its centre locates over the Barents Sea the inflow of air masses from the northern quadrant is observed over the North Atlantic. This brings cold air of Arctic origin to the islands and causes an essential drop in the air temperature. Such situation takes place during the cold months preceding and following the warm mid−winter events. During the warm spells the Icelandic Low gets deeper−than−usual and it is pushed to the northeast, which contributes to the air inflow from the southern quadrant.
In this study, the turbulent non-premixed methane-air flame is simulated to determine the effect of air velocity on the length of flame, temperature distribution and mole fraction of species. The computational fluid dynamics (CFD) technique is used to perform this simulation. To solve the turbulence flow, k-ε model is used. In contrast to the previous works, in this study, in each one of simulations the properties of materials are taken variable and then the results are compared. The results show that at a certain flow rate of fuel, by increasing the air velocity, similar to when the properties are constant, the width of the flame becomes thinner and the maximum temperature is higher; the penetration of oxygen into the fuel as well as fuel consumption is also increased. It is noteworthy that most of the pollutants produced are NOx, which are strongly temperature dependent. The amount of these pollutants rises when the temperature is increased. As a solution, decreasing the air velocity can decrease the amount of these pollutants. Finally, comparing the result of this study and the other work, which considers constant properties, shows that the variable properties assumption leads to obtaining more exact solution but the trends of both results are similar.