Ekstremalne gradienty temperatury w przygruntowej warstwie powietrza

The paper presents extreme thermal gradients in the air layer 0.5-2 m above the ground (Stevenson’s shelters), measured AT the research station in Gaik-Brzezowa (Carpathian Foothills; φ = 49 °52 ’N, λ = 20 °04 ’E, h = 302 m a.s.l.), which is managed by the Jagiellonian University (Cracow, Poland). The measurements were taken six times per day (6, 8, 12, 14, 18, 20 UTC) in the periods 1976-1980 (river valley bottom) and 1988-1997 (flattened ridge top). Basic descriptive statistics were calculated for the gradients in every term, month and landform (Fig. 1, Tab. 1). In order to fmd the days with both extreme values of gradients and their diurnal differentiation, the k-means method of cluster analysis was used (Tab. 2). The main difference between the two landforms is that in the river valley the diumal gradients courses differ much more from each other than at the flattened ridge top, where only the winter differs from the rest. At 18 and 20 UTC in winter in the river valley there are largest negative gradients from all seasons, while at the ridge top - the smallest. In those two terms the extreme gradients from spring to autumn have much smaller values in the river valley than at the ridge top. The presented extreme gradients have no direct irnpact to the functioning of the plants, but they influence the energy and matter exchange in the air layer near the ground.