Abstract
Root-mean-square differences between satellite and radiosondes for the past three years that TIROS-N has been operational are examined. They show a pronounced annual cycle because the statistics are dominated by the Northern Hemisphere. Differences are smaller in the summer and are larger in the winter, but they reflect a change in the effect of location differences as well as retrieval error. In addition to the annual cycle, there is an increase in retrieval accuracy with time. For the partly cloudy retrievals, the increase approaches 1.3 K for some levels.
