AbstractIt is shown that the high correlation coefficients between pressure‐and temperature high up in the troposphere are closely related to the constancy of the lapse‐rate of temperature. The correlations between the mean temperature of the column up to 9 km. and the temperatures at 3 and 6 km. are very high. Some factors tending to produce a constant lapse‐rate are discussed. It is previously shown that the observed pressure‐temperature correlations do not necessarily imply a “solid current” or “barotropic” motion, but are consistent with very large changes of wind with height, both in direction and velocity, provided that these are spread through most of the troposphere and are not concentrated at a surface of discontinuity.Groups of extreme cases show that when the barometer at sea level is very low or very high the troposphere contributes about half the deviation from the mean. Both cyclones and anticyclones can be grouped into systems largely confined to the troposphere, and systems extending to the stratosphere. The argument in favour of an advectional theory is developed. It is shown that the mean pressure at 8 km. over deep cyclones is no lower than over well marked