The aim of this study is to examine the nature and magnitude of the changes in mean seasonal daily maximum and minimum temperatures and diurnal temperature ranges for all of Turkey, its regions and the 59 stations during the period 1930-1993. Maximum temperatures show significant cooling trends in many stations in summer and autumn. Most of the regional mean maximum temperatures have decreased in all seasons, except spring. None of the observed trends in regions was significant statistically. Mean seasonal minimum temperatures have indicated significant warming trends in many stations in all seasons except winter. Majorities of the regional mean minimum temperatures have also increased markedly in all seasons. Warming trends of spring minimum temperatures were significant over the Black Sea, Aegean and South-eastern Anatolia regions. Spring minimum temperatures for all of Turkey have shown a significant linear trend, with an increase of + 0.145"C per decade.
Diurnal temperature ranges have decreased significantly over most of the regions in all seasons, except partly in autumn and in so many stations in all seasons. Most of the decreasing trends in summer were significant at the 1 per cent level. It seems that changes of the diurnal temperature range in spring, summer and autumn were related closely to changes of maximum temperatures. Thus the decrease of the regional mean diurnal range was associated mainly with decreases of maximum temperatures in summer and autumn, and with slightly increased maximum temperatures in spring. Many stations that experienced a significant trend in diurnal ranges had a significant positive serial correlation. Our !%st results for Ankara have shown no significant trend in the mean monthly cloudiness and monthly cloudiness at 1400 hours local time, except a decrease in May cloudiness at 1400 hours.