Regional trends of surface and tropospheric temperature and evening-morning temperature difference in northern latitudes: 1973-93

Trends for the 21-year period 1973-1993 of temperatures at the surface and in the troposphere were analyzed from radiosonde observations in eight north-latitude regions. The seasonal consistency of the surface and tropospheric trends of temperature and evening-morning temperature difference was examined for these regions. In most seasons the surface temperature trends were positive in Eurasia and western N. America but were negative in central N. America and eastern Canada. The regions with sizable and statistically significant surface temperature trends usually had significant tropospheric trends up to 500 mb and sometimes to 300 mb. An exception was central Asia, where the strong warming was confined below 850 mb. The significant tropospheric trends showed a tendency to de crease in magnitude with height. Trends of the evening minus morning temperature difference were also analyzed in two sectors, Canada and Russia, where the radiosonde launches occurred at 5am and pm +/-2hrs. Trends were fairly consistent in sign between the surface and lower troposphere in both sectors and up to 300 mb over Canada. Most Canadian trends were significant and represented a decreasing range between evening and morning temperatures. Significant Russian trends were primarily in summer.