Stratification of air temperature extreme values in Felin n. Lublin (1986–1995). Part I. Daily amplitudes

Abstract

This paper is the continuation of an earlier study on air temperature extreme values in vertical profile. The measurements were made at the Agrometeorological Observatory in Felin near Lublin. The research involved collecting data on maximal and minimal air temperature values taken by means of liquid thermometers put in the following places: a meteorological cage (200 cm), Geiger-Tomanek system cages (20, 50, 150 cm) and a wooden shuttered radiation shield on black earth (5 cm). Readouts were made at: 7(8), 13(14), 19(20) in the winter and summer parts of the year, respectively. Within the period of 10 years, that is from January 1, 1986 to December 31, 1995 the data were collected. The following basic statistic measures were applied: arithmetic mean, standard deviation, skewness, kurtosis and multiple regression. Box plots were used to present daily amplitude distributions at all levels. In the examined period, the highest mean temperature was taken in July and at the height 150 cm in vertical profile. On the other hand, the lowest mean minimal temperature was always measured at the level of 5 cm. The warm half of the year was characterized by the highest mean maximum air temperature at the level 20 cm, the cold half of the year – by the highest values at the level of 50 cm. The highest amplitude was recorded in the warm season with the maximum in July. The lowest amplitude at all levels was noted in winter months. Daily air temperature amplitude showed the highest degree of variability at the level of 5 cm. As the level increased, the air temperature amplitude decreased. Within a year the greatest variability was observed in summer months up to the height of 50 cm, above this level; however, the highest degree of variability was recorded in spring and autumn. For the major part of the year, daily amplitude distribution was standard but in winter a right-handed asymmetry was noted. In January the distribution became highly concentrated. Finally, significant difference in daily air temperature amplitude variability was observed at the layers of 5–50 cm and 150–200 cm. The amplitude depended on cloudiness and air humidity in July, August, September and October to a large extent in December; however, to a lesser extent. In March, May, June and July air humidity did not affect temperature amplitude at all.