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1 2015

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Zróżnicowanie temperatury i wilgotności wyględnej powietrza w rejonie Kaffiøyry (NW spitsbergen) w sezonie letnim 2014 roku

Kejna M., Ulandowska-Monarcha P., Strzyżewski T.

Problemy Klimatologii Polarnej

2015

Nr 25

211--226

W artykule przedstawiono zróżnicowanie przestrzenne temperatury oraz wilgotności powietrza w rejonie Kaffiøyry (NW Spitsbergen) w sezonie letnim 2014 r. Na podstawie pomiarów na stanowiskach położonych na różnych wysokościach nad poziomem morza przeanalizowano zmiany temperatury i wilgotności powietrza w pionie, obliczono pionowe gradienty tych elementów. Uzyskane wyniki odniesiono do pionowych sondaży atmosfery wykonywanych w pobliskiej stacji w Ny Ålesund. Temperatura oraz wilgotność względna powietrza wykazują znaczne zróżnicowanie przestrzenne. Relacje między stanowiskami zmieniają się z dnia na dzień w zależności od rodzaju mas powietrza oraz zachmurzenia. Stwierdzono również zmienność pionowych gradientów temperatury i wilgotności względnej powietrza w cyklu dobowym.

This article presents the spatial diversity of temperature and relative humidity of the air in the area of Kaffiøyra (NW Spitsbergen). In the summer season of 2014 (21 July – 31 August), observations were carried out at 9 measurement points equipped with temperature and humidity recorders. The points were located in two terrain profiles: the mountains where the highest point was situated at 590 m a.s.l. in the Prins Heinrichfjella range and from the terminal moraines to the firn field (375 m a.s.l.) of the Waldemar Glacier. On the basis of the measurements taken at the sites situated at different absolute heights vertical changes in air temperature and humidity were analysed and lapse rate of air temperature gradients were determined. The results were referenced to vertical atmospheric soundings carried out at the nearby station in Ny Ålesund. The air over NW Spitsbergen (Ny Ålesund) demonstrated a mean vertical lapse rate of 0.61˚C/100 m at the atmospheric layer up to six or seven hundred metres. On most days normal stratification was observed, where temperature fell with height, on 3 days a ground-level air temperature inversion occurred and on 9 days a temperature inversion occurred in the free troposphere. In the area of Kaffiøyra, air temperature decreased with height from 5.5°C on the coast (KH) to 2.5°C at 590 m a.s.l. (PH2). On the Waldemar Glacier, the mean air temperature ranged from 5.0°C on the moraines (ATA) to 3.6°C on the firn field (LW2). The relationship between the sites changed on a daily basis, depending on the cloud amount, insolation and local circulation (e.g. connected with the influence of foenic wind). Averaged lapse rate in relation to the coast (KH) reached between 0.84°C/100 m (LW1-KH) and 0.39°C/100 m (KU-KH) or 0.40°C/100 m (ATA-KH). The mountain tops (PH1 and PH2) are also distinguished by their smaller lapse rate. An inversion in the vertical distribution of air temperature was also frequent and, for example, at the KT site it occurred at 33.9% of the hours and at 28.7% at ATA. On the Waldemar Glacier, inversion occurred at a frequency of 16.3% at its front (LW1) to 8.8% at its firn field (LW2). On the mountain tops, the inversion occurred at a frequency of 18% (PH2). The relative humidity of the air over Spitsbergen is high due to the prevalence of maritime air masses. According to the soundings conducted at Ny Ålesund, the humidity increased with the height, however in 13 cases a vertical inversion of relative humidity occurred – the overground air layers proved more saturated with water vapour. On Kaffiøyra, the average relative humidity of the air was 87.7% and increased up to approx. 500 m, above which it slightly dropped. This results from a high frequency of occurrence of Stratus clouds which do not reach the higher tops. The vertical gradients of relative humidity were diverse: at most sites, the relative humidity increased with the height, for example at the PH1 site, the gradient was 3.12%/100 m. A greater diversity of the relative humidity was typical of the hours around midday.