• cloud cover;
  • stratiform and convective clouds;
  • trend analysis;
  • Poland


In Łódź, the total cloud cover has significantly decreased in the second half of the 20th century. This change is opposite to that of the low-level cloud cover in the warm part of the year. But the most important are variations in frequencies of different cloud types. The stratiform clouds, St and Ns, became less frequent, whereas the convective ones, Cu and Cb, became more frequent. The rise in Ac and high-level clouds and the fall in As clouds were also observed. These changes are consistent with other observations in central and eastern Europe. Because different cloud types are created in different conditions, their variability is a valuable tool for assessment of changes in processes taking place in the troposphere. Such reorganization in cloud types distribution indicates significant changes in the vertical structure of the troposphere: fall of the frequency of temperature inversions in the lower troposphere and stronger lapse rate. Copyright © 2007 Royal Meteorological Society