Tropospheric Stratospheric Exchange (TroStra)

Prof. Dr. Justus Notholt
Dr. Mathias Palm
FB1; Universität Bremen
Otto Hahn Allee 1
D-28359 Bremen



In the project TroStra we will investigate the transport of trace gases from the troposphere into the stratosphere, in particular sulfur containing species. The project will contribute to the quantification of the variability of the aerosol layer in the stratosphere. To this end, the composition, the origin of measured trace gases and their way into the stratosphere will be monitored and studied.


We will use measurements obtained at four stations in the tropics:
Western pacific:

  • Koror, Palau
  • Burgos, Philippinen

South America

  • Paramaribo, Suriname
  • Porto Velho, Brasilia

The instruments in Koror and Paramaribo are operated by the Institute of Environmental physics in cooperation with the AWI Postsdam. The other instruments are operated by cooperation partners, the University of Wollongong, Australia and the BIRA, Brussels, Belgium.

Additionally we will analyze LIDAR measurements, which are obtained in Koror and Burgos for optically thin clouds in the tropopause region. Those clouds are created by slowly rising air in the tropopause region. These data are a valuable supplement to the measurements of the trace gases.

The measurement stations which are used in this project are alternating in the troposphere of the northern and southern hemisphere. The reasons are

  1. the boundary, which separates Northern and Southern hemispheric air is well defined. Air needs about one year to cross this boundary, while the mixing time within one hemisphere is in the range of weeks.
  2. the boundary, the so called ITCZ (Inner Tropical Convergence Zone) follows the sun with some time lag, i.e. it is south if the equator in the first half of the year and north in the second


The measured data will be interpreted using models of atmospheric circulation. In particular, the transport of sulfur containing species, e.g. COS, into the pacific warm pool and in the stratosphere will be investigated. The pacific warm pool is the area north-east from Indonesia, which is mainly the place of transport of air from the troposphere into the stratosphere