ON THE AIR-MASS TEMPERATURE DISTRIBUTION IN THE MIDDLE AND HIGH TROPOSPHERE IN WINTER

To place the upper-air analysis of baroclinic fields such as those associated with the polar front and the jet stream on a firmer basis, winter temperature data for selected stations in North America and the British Isles are analyzed. From the form of temperature frequency distributions for these stations at various levels in the middle and higher troposphere, it is found that the baroclinic field of the polar front is clearly evident up to at least 400 mb. No evidence exists for baroclinity at 300 mb. Little evidence of the jet-stream baro-clinic field is found by this method. Approximate temperatures for the tropical and polar air masses at various levels are determined. From the skewness of the distributions some deductions are made as to the advisability of replacing the mean by the median for spatial representation of temperature and contour-height data for mean conditions.