Relative humidity and humid characteristic days in Lublin in 1951–2015

Abstract

The paper analyzes the temporal variability of relative humidity in Lublin in the years 1951–2015. In addition, the frequency of occurrence of specifi c humid days, i.e. dry, moderate dry, humid and very humid days were characterized. The source material of the study was the values of relative humidity measured at the UMCS Meteorological Observatory located in the city center. Dry days (f ≤ 55%), moderate dry (56–70%), humid (71–85%) and very humid days (f ≥ 86%) are defi ned on the basis of the average daily values of relative humidity. For the selected characteristics, the statistical signifi cance of trends was tested by the Mann-Kendall test. The average value of relative humidity in Lublin in 1951–2015 was 77.9% and it ranged from 73.6% in 2005 to 83.3% in 1958. In the analyzed years, a signifi cant downward trend was observed. This drop is caused by rising air temperature and spatial development of the city. Humid days (average 150 days a year) and very humid days (average 119 days a year) have occurred with the highest frequency. Moderate dry and dry days were much less frequent – 80 and 16 days a year, respectively. The values determined for these characteristics were statistically signifi cant for dry and moderate dry days (positive trend) and for very humid days (negative trend).