Pääjärvi representative basin in Finland: comparative studies of climatological conditions over a lake and the surrounding land areas in 1969-1970

Abstract

Lake and land climatological stations in the study area were compared for air temperature and humidity, wind velocity, cloud cover, precipitation and evaporation. The biggest differences between the stations in regard to their meteorological parameters were found in the daily temperature minima, which were greatly affected by the amount of cloud cover and wind velocity, and in the periodic and aperiodic fluctuations of air temperature. The sums of effective growing temperatures were 10 ... 15 % higher over the lake than at the land stations. Water vapour pressure was higher over the lake than over land. Precipitation from June to October was about 10 % smaller on the lake than at the land stations. Evaporation was measured at the land stations with Class A pans, and evaporation from Lake Pääjärvi was estimated by the bulk‑aerodynamic method. The rate of evaporation from the lake was greater than that from the pans.