Geophysica , 35(1-2), 59-69, 1999.
1Sodankylä Geophysical Observatory, Sodankylä,
2Finnish Meteorological Institute, Sodankylä Observatory, Sodankylä, Finland
In the present study we analyse various long-term data series of measurements run by the Sodankylä Geophysical Observatory for possible indications of cooling trends in the upper atmosphere. We review trends seen in the ionospheric F2 peak altitude measured by ionosondes and compare them with the Finnish ionosondes at Nurmijärvi and Sodankylä as well as with comparable observations of the EISCAT incoherent scatter radars. Furthermore we study trends seen in the data of the Finnish riometer network at 7 different latitudes. While some of the observed trends suggest cooling, a consistent signal of upper atmospheric cooling, caused possibly by increasing amounts of greenhouse gases, cannot be deduced from the data.