In-situ Messung von Wasserdampf in der unteren Stratospäre und im Breich der Tropopause

• Main Author: Eicke, N.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Forschungszentrum, Zentralbibliothek 1999
• Subjects: Arctic
• Online Access: https://juser.fz-juelich.de/record/40645; https://juser.fz-juelich.de/search?p=id:%22PreJuSER-40645%22

The aim of this thesis was the investigation of dynamical processes in the tropopause region using water vapour measurements . An existing hygrometer for airborne measurements was improved so that it works now more reliable and it is easy to operate . A new hygrometer was developed for balloon-borne measurements. H2O was measured during four airborne and two balloon-borne campaigns, The accuracy of measured tropospheric H 2 O-water vapour mixing ratios (> 40 ppmv) was better than 3% and of measured stratospheric H 2O-water vapour mixing ratios (3-6 ppmv) reached 3-10%. The result of frequent calibrations performed between two measurement flights is that the quality of measurements was reproduced and that measurements of different campaigns can be compared. Correlations of H2O with long lived trace gases, as N2O and 0 3, were used to investigate seasonal and regional differences of H 2O - mixing ratio in the lowermost stratosphere (especially in the mixing layer characterised by air mass intrusions at the lokal tropopause) and in the tropopause region . In May 1996 this region was wettest (35-58 ppmv) in the vicinity of the mid latitude jet-stream compared to measurements in other seasons and regions. In the winter the mean measured H2O mixing ratio at the arctic tropopause was 10-32 ppmv. During some flights only 5-6 ppmv were measured in cold air masses of that reagion (0 ,~ 300-325K). lt was shown that these cold air masses (T 200 K) were dried by condensation and sedimentation processes. Sometimes very dry air masses (H2 O mixing ratios < 4 ppmv) were measured above the tropopause . Condensation and sedimantation processes in these air masses could not be proved at the moment of measurments and some days earlier by trajectories calculation. Therefore statistics of minimum ECMWF temperatures / saturation water vapour mixing ratios were performed. The result was that minima of 1-4 ppmv are possible between 348 and 380 K potentiell temperature in the subtropics (15-35° N) . In mid and high latitudes the ...