Wyprawy Geograficzne na Spitsbergen, UMCS ... w historii ToruÅskich Wypraw Polarnych, Årednia dobowa temperatura z caÅego okresu wyniosÅa w KH. 6,3° C ...
Andrzej ARAZNY Department of Geomorphology and Hydrology of Lowlands Institute Geography and Spatial Organization Polish Academy of Sciences Kopernika 19, 87-100 Toruń POLAND
POLISH POLAR STUDIES XXVI Polar Symposium
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Ниш
Lublin, June 1999
DIFFERENTIATION OF AIR TEMPERATURE IN THE SUMMER SEASON 1998 ON THE WALDEMAR GLACIER AND ON THE KAFFIÖYRA PLAIN (SPITSBERGEN) ZRÓŻNICOWANIE TEMPERATURY POWIETRZA W SEZONIE LETNIM 1998 NA LODOWCU WALDEMARA I RÓWNINIE KAFFIÖYRA (SPITSBERGEN)
ABSTRACT In this paper the thermal conditions on the Waldemar Glacier and on the Kaffiöyra Plain are presented, which were studied during the XV Toruń Polar Expedition. The measurements were carried out in three points on the Kaffiöyra Plain (KH), in front of the snout of the Waldemar Glacier (LW1) and on its firn part (LW2). The differentiation of thermal conditions was analysed by different weather situations depending on the elevation above sea level, the distance from the sea and the character of the ground.
INTRODUCTION
The Waldemar Glacier (Fig. 1) is one of the smaller glaciers on the Kaffiöyra Plain, its surface equals 2.66 km 2 (Lankauf 1997). The snout of the glacier lays at 126 m above sea level and the firn fields at 370-470 m a.s.l. The glacier is oriented approximately to E-W direction. The whole Waldemar Glacier is situated in a mountain region in the Prins Heinrichfjella massif (the highest elevation - Prinsen peak 770 m a.s.l.). From the south it is separated from the Irena Glacier by the not very high Gräfjelletem (344 m a.s.l.), which impede the southern winds much less then Prins Heinrichfjellet the northern and eastern ones. Winds from the Lövenskiolda Plateau reach the Waldemar Glacier mainly by the pass separating this glacier from the Aavatsmark Glacier from NE (about 410 m a.s.l.). Frequently winds blow also from the direction of Irena Glacier over the eastern, highest part of Gräfjellet (Wójcik, Marciniak, Przybylak 1981). On the Kaffiöyra Plain winds with N and S components blowing along the Forland Strait dominate. Fig. 1. shows the locations and signs of measurement points.
26
Andrzej Araźny
Fig. 1. Localisation of the meteorological research area during the XV Toruń Polar Expedition and the distribution of meteorological stations (KH, LWI, LW2) according to the topographic map of K. R. Lankauf
Selected problems concerning the thermal conditions in the Kaffiöyra region have been presented in the following publications (e.g.: Wójcik, Marciniak, Przybylak 1981; Wójcik, Przybylak 1985; Marciniak, Marszelewski, Przybylak 1985; Marciniak, Przybylak 1992; Wójcik, Marciniak, Przybylak, Kejna 1993; Wójcik, Marciniak, Przybylak 1998; Araźny 1998b). IR this paper the results of meteorological observations were used, which were made in the summer 1998 (21 July-31 August) on the Waldemar Glacier and on the Kaffiöyra Plain by thermographs situated at 2 m height above the ground level in standard meteorological boxes. The summer season in 1998 was exceptionally warm and at the same time very cloudy with weak atmospheric dynamics, rare and low productive atmospheric precipitation. The thermal conditions on the Kaffiöyra region in a high degree are formed by circulation factors (Wójcik et al. 1992; Araźny 1998b). During the research period anticyclonic situations dominated (71.4%), only on 21.5% of the days the weather conditions were formed by cyclones. According the classification of synoptic situations (Niedźwiedź 1981) on the Kaffiöyra in the summer 1998 types SEa (26.2%), Ka (14.3%) and Ca (11.9%) dominated. The main meteorological research work was carried out at the Base of Toruń Polar Expeditions (KH) in the northern part of the Kaffiöyra Plain (78°41'N, 1Г5ГЕ). The KH station (Phot. 1) was situated on the moraine culmination of the Aavatsmark Glacier at 11.5 m elevation above sea level and about 200 m far from the Forland Strait. The KH station represent a climatic environments with the prevalence of oceanic features. The LW1 stand (Phot. 2) was situated on the snout moraine - 160 m from the snout of the Waldemar Glacier - at 128 m a.s.l. and about 4 km far from the Forland Strait. The meteorological conditions at this station are formed by the influence of two contrasting environments: the glacier and its moraine foreground. Therefore, among others, there is great variability of air temperature on short time scales due to opposite air currents flowing from inside of ice plateau down the gla-
Differentiation of air temperature in the summer season 1998.
27
cier (cooler) and currents from the sea up the glacier (warmer) (Wójcik, Marciniak, Przybylak 1981). The station at the firn part (LW2) was located at the altitude of 384 m a.s.l. and about 6 km away from the sea (Phot. 3). The air temperature is influenced mainly by a snowy-icy environment, whose surface temperature in summer is 0°C. RESULTS
The most important data related to thermal conditions on the research area in summer 1998 are presented in Table 1. and 2. The air temperature in summer 1998 at the stands KH, LW1 and LW2 shows a great day to day variability (Fig. 2). Warmer and cooler periods lasting a few days appeared in succession. The mean diurnal air temperature was at the KH stand between 2.6°C (22 August) and 11.4°C (22 July), at the LW1 1.8°C (21 and 22 August) and 11.7°C (22 July), and at the LW2 -0.ГС (22 August) and 11.6°C (22 July). The variability of mean day and night air temperature was at the KH stand 8.8°C, at LW1 9.9°C, and at LW2 11.7°C. The mean day and night temperature over the entire period was 6.3CC at the KH stand, 5.5°C at LW1, and 4.ГС at LW2. The mean air temperature falls with the altitude. The average gradient of air temperature between the KH and LW1 stands was 0.7ГС /100 m, between KH and LW2 0.60°C/100 m, and between LW1 and LW2 only 0.55°C/100 m (Table 1). The difference between the gradients of KH-LW1 and LW1-LW2 is a result of thermal jump (Table 1, Phot. 4) which is exist at the boundary of glaciated and nonglaciated environments (Wójcik, Marciniak, Przybylak 1998). Table 1. Five day average air temperatures (°C) at the stands KH, LW1, LW2 and mean day and night vertical gradients of air temperature (°(7100 m) between the stands KH-LW1, KH-LW2, LW1-LW2 Period
KH
LW1
LW2
KH-LW1
KH-LW2
LW1-LW2
21-25.07
8.9
8.4
7.3
0.39
0.41
0.41
26-31.07
6.2
4.8
3.6
1.15
0.70 0.54
0.50 0.41
0.91 0.84
0.91 0.76
01-05.08
5.3
4.3
06-10.08
6.0
4.9
3.3 2.6
0.82 0.94
11-15.08 16-20.08
6.3 7.1
5.1 6.9
3.1 5.4
1.03 0.20
0.46
0.59
21-25.08
4.8
4.4
3.6
0.36
0.32
0.30
26-31.08
6.0
5.2
3.8
0.74
0.59
0.53
01-31.08
5.9
5.1
3.6
0.68
0.61
0.58
21.07-31.08
6.3
5.5
4.1
0.71
0.60
0.55
Andrzej Araźny
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Table 2. Air temperature in the region of Kaffiöyra (KH, LW1 and LW2) in the period from 21 July to 31 August 1998 Station
Tmax abs
Tmax
Tm
Tmin
KH
14.0
7.6
6.3
5.0
Tmin abs 1.8
LW1
14.1
7.2
5.5
3.6
0.3
LW2
15.0
5.7
4.1
2.3
-1.1
The minimal temperatures bear evidence of radiative processes modified by local factors and weather conditions. Since the terrain relief allows for free gravitational flow of cold air down the glacier, the distribution of absolute minimum temperature, similarly as of mean temperature, is correlated with altitude and type of environment (Wójcik et al. 1981). The mean minimal temperatures in summer 1998 were as follows: 5.0°C at KH, 3.6°C at LW1, and 2.3°C at LW2 (Table 2). The absolute minimum temperatures were: 1.8°C, 0.3°C, -1.1°C, respectively (Table 2, Fig. 2). Minimum temperatures occurred mostly in the range of 0-4 hours LMT, when the solar irradiation was lower. The maximum temperatures depend on various dynamical processes in the atmosphere and on local factors. The mean maximal temperatures in the investigated season were as follows: 7.6°C at KH, 7.2°C at LW1, and 5.7°C at LW2. The absolute maximums were: 14.0°C, 14.ГС , 15.0°C, respectively (Table 2, Fig. 2). The highest maximum temperatures at KH and LW1 occur during sunny weather, in the afternoon from 14 to 18 hours LMT. It is connected with the warming up of the dark moraine ground. At LW2 the maximum temperature occurs almost uniformly during the whole day. The general course of air temperature during the observations exhibits a decreasing trend which is characteristic of the end of polar summer. By the end of the measurement period considerable cooling occurred twice. The mean temperature showed a large day to day variability (Fig.2). The average temperatures in the coo-lest five day period (21-25 August) were as follows: 4.8°C at KH, 4.4°C at LW1, and 3.6°C at LW2. They were conditioned by an advection of cool arctic air from the north. The highest temperature was recorded in the five day period of 21-25 July during an advection from south-west, and the mean temperatures of this period was: 8.9°C at ICH, 8.4°C at LW1, and 7.3°C at LW2. The day and night air temperatures for selected weather situations are presented in Fig. 3. Day and night course of temperature for overcast weather (27 July) at KH, LW1, and LW2 is uniform. The day and night amplitudes did not exceed 1.1°C. The day and night averages of 27 July correspond to elevation above sea level: 6.7°C at KH, 4.8°C at LW1, and 3.0°C at LW2. For partly cloudy weather the day and night course of temperature depends on the day and night cloudiness. The day and night temperatures on 10 August (partly cloudy day) were shaped by insolation at the analysed stands (the relative sunshine duration in this day equalled 42.9%). The day and night signature is clearly visible and has large amplitudes (3.2°C at KH, 4.ГС at LW1, and 5.4°C at LW2).
Differentiation of air temperature in the summer season 1998..
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