Articles by J. Keränen

The aim of the investigation was to estimate the effect of climate on the temperature observations and heating of buildings. Temperature data of observation stations in Finland and in the neighbouring countries near Finnish borders, in all 190 stations, was collected during heating season. 

Heating season begins in the northern border of Finland in 20th of July,  in Rovaniemi oin the Northern Finland in the middle of August, and 5th of September in the Southern coast of the country. Similarly, the heating season ends in 2.-10.6. in Southern and Central Finland, in June in Northern Finland, and in the middle of June in the Northernmost Finland, where heating season continued almost the whole year. In Southern Finland the length of heating season was 280 days. In the coldest heating season in 1942-1942 the heating decree-days increased most in the province of Varsinais-Suomi in Southern Finland. The increase decreased towards North. In the warmest heating season in 1929-1930 decrease of heating decree-days was similar in almost the whole country. The data can be used to define how different weather conditions affect the need of fuel.  

The PDF includes a summary in German. 

• Keränen, E-mail: jk@mm.unknown

The article discusses the thermal conditions in the northern limits of trees and some bushes in Finland. Temperature is the most important limiting factor for distribution of plant species. Precipitation variations, however, are small in Finland. The article lists the main features of thermal conditions during the different seasons in different parts of Finland. The northern limits and the thermal condition of the area are described for the following species: Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.), mezereon, buckthorn, common alder, linden, elm, maple, hazel, ash, oak, hybrid mountain ash, yew and Swedish whitebeam.

The PDF includes a summary in English.

• Keränen, E-mail: jk@mm.unknown

Earlier studies have shown strokes of lightning as the reason for 42% of forest fires in Finland. The frequency in northern Finland has been three times higher than in more southern parts of the country or 1.5 times higher than in Sweden. Taking the climatic factors into account these figures don’t seem to be accurate.

The study is based on the statistics about thunders in northern Finland and the information on the forest fires. We know that though there has been a lightning it is not always that the lighting strikes on land and lights a fire.

From the statistics it can be seen that the most forest fires that are thought to be kindled by lightning, have occurred in the same time when there has been thunder and lighting. Thunders and strokes of lightning striking to the land are the most common reason for forest fires during the warmest summer in northern Finland. The knowledge that a proceeding thunder storm may kindle several forest fires in a row must be acknowledged when planning the fire fighting resources. 

The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.

• Keränen, E-mail: jk@mm.unknown