Royal Netherlands Meteorological Institute
Section of Atmospheric Composition
During POLINAT 1 -POLlution from Aircraft IN the North ATlantic flight corridor- experiment, in situ water vapor measurements has been performed in the upper troposphere and the lower stratosphere, from an aircraft, in the North-Atlantic region around 50 N. That experiment took place during winter 1994 and summer 1995. From the data analysis, and using PV coordinates, it is shown that the water vapor content observed in the region situated slightly above the local tropopause is consistent with the transport from troposphere to stratosphere at mid and high latitudes. It appears that there is a seasonal variation with a higher water vapor content in the lower stratosphere during summer. The source of this variation could be due to the difference in the relative contribution of the troposphere to stratosphere isentropic and convective transport as well as transport from the upper levels of the stratosphere due to the general circulation. It is however difficult to quantify the water vapor budget in the lower stratosphere and upper troposphere. It is pointed out that, for this quantification, there is a need of more in situ measurements in the vicinity of the tropopause at mid latitudes.
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